Merge phase-s: Phase S complete — ReaSampler 9000 VST3 sampler (S1-S18), editor scale + control surfaces (S12), drop-and-load (S17), editor drop-accept (S13 relay degraded per spec)

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "vendor/WDL"]
 	path = vendor/WDL
 	url = https://github.com/justinfrankel/WDL
+[submodule "vendor/vst3sdk"]
+	path = vendor/vst3sdk
+	url = https://github.com/steinbergmedia/vst3sdk

CLAUDE.md

@@ -51,6 +51,7 @@ Key targets (see CMakeLists.txt for the full list):
 | `tooltip_tests` | executable | Pure unit tests for `tooltip` — no REAPER, no DAW. |
 | `card_drag_tests` | executable | Pure unit tests for `card_drag` — no REAPER, no DAW. |
 | `card_meta_tests` | executable | Pure unit tests for `card_meta` — no REAPER, no DAW. |
+| `pitch_shift_tests` | executable | Pure unit tests for `pitch_shift` (S16 Preserve engine) — no REAPER, no DAW. |
 | `reaper_reasampler` | loadable module | The actual extension binary (`.dll` / `.dylib` / `.so`). |
 
 ### Beta channel build (Phase V, V4)

CMakeLists.txt

@@ -34,9 +34,13 @@ set(REASAMPLER_CHANNEL "stable" CACHE STRING "Build channel: stable (default) or
 if(REASAMPLER_CHANNEL STREQUAL "beta")
     set(REASAMPLER_CHANNEL_IS_BETA 1)
     set(REASAMPLER_OUTPUT_NAME "reaper_reasampler_beta")
+    # The VST3 instrument's on-disk name forks the same way (S18) — must match
+    # app_version::vstOutputName() so the artifact name and the in-binary self-id agree.
+    set(REASAMPLER_VST_OUTPUT_NAME "reasampler_9000_beta")
 elseif(REASAMPLER_CHANNEL STREQUAL "stable")
     set(REASAMPLER_CHANNEL_IS_BETA 0)
     set(REASAMPLER_OUTPUT_NAME "reaper_reasampler")
+    set(REASAMPLER_VST_OUTPUT_NAME "reasampler_9000")
 else()
     message(FATAL_ERROR
         "REASAMPLER_CHANNEL must be 'stable' or 'beta' (got '${REASAMPLER_CHANNEL}')")
@@ -301,6 +305,19 @@ target_include_directories(app_version PUBLIC src ${CMAKE_CURRENT_BINARY_DIR}/ge
 add_library(provenance STATIC src/provenance.cpp)
 target_include_directories(provenance PUBLIC src)
 
+# ---------------------------------------------------------------------------
+# 2j') Pure assignment_request library — NO REAPER, NO SWELL, NO VST3. The S8 ingest
+#      assignment-request wire format: the (bankId, sampleId, generation) value the
+#      EXTENSION writes to "reasampler" ext-state after an ingest-with-assign, decoded by
+#      the VST3 instrument in a later dispatch. Only the wire (build/parse round-trip)
+#      lives here — writing it is the persist shell's job, reading it the instrument's.
+#      Split out (mirror of provenance / owned_manifest) so the format both artifacts
+#      depend on is unit-tested outside the DAW; the reader lands in a separate artifact,
+#      so the round-trip test is the contract guard. No dependency — plain strings + int64.
+# ---------------------------------------------------------------------------
+add_library(assignment_request STATIC src/assignment_request.cpp)
+target_include_directories(assignment_request PUBLIC src)
+
 # ---------------------------------------------------------------------------
 # 2k) Pure action_buttons library — NO REAPER, NO SWELL. The Milestone 11
 #     action-trigger button strip: strip rect + N buttons at a minimum width ->
@@ -329,6 +346,20 @@ target_include_directories(action_buttons PUBLIC src)
 add_library(drag_out STATIC src/drag_out.cpp)
 target_include_directories(drag_out PUBLIC src)
 
+# ---------------------------------------------------------------------------
+# 2l') Pure instrument_drop library — NO REAPER, NO SWELL, NO VST3 SDK. The S17
+#      drop-and-load blob-construction core: turn the dragged capture id into the
+#      base64 "vst_chunk" the extension injects via TrackFX_SetNamedConfigParm so a
+#      freshly-added ReaSampler 9000 plays that capture. Reuses the instrument's OWN
+#      serializer (sample_map::serializeComponentState) — NOT a parallel byte writer —
+#      so the cross-artifact blob contract cannot drift; links sample_map (which pulls
+#      bank_book/wav_trim/sampler_core transitively) and NEITHER SDK. The round-trip
+#      test decodes back through the instrument's own reader. Mirror of assignment_request.
+# ---------------------------------------------------------------------------
+add_library(instrument_drop STATIC src/instrument_drop.cpp)
+target_include_directories(instrument_drop PUBLIC src src/vst)
+target_link_libraries(instrument_drop PUBLIC sample_map)
+
 # ---------------------------------------------------------------------------
 # 2m) Pure theme library — NO REAPER, NO SWELL, NO LICE. The Phase L (L1) palette
 #     core of the shared drawing kit: a ROLE-based color model (bg/base..warn), the
@@ -446,6 +477,31 @@ add_library(card_drag STATIC src/card_drag.cpp)
 target_include_directories(card_drag PUBLIC src)
 target_link_libraries(card_drag PUBLIC drag_out bank_grid)
 
+# ---------------------------------------------------------------------------
+# 2v) Pure sampler_core library — NO VST3, NO REAPER, NO SWELL. The HEART of the
+#     Phase S MIDI-playback instrument (S3 / D3): polyphonic voice allocation with
+#     bounded stealing, an ADSR amplitude envelope, a key/velocity keymap with
+#     (note, velocity) -> zone resolution, and repitch/interpolation from a root note
+#     with loop-point-aware sustain. The mirror of bank_model / peaks / bank_book,
+#     tested hard outside any host. Lives under src/vst/ (it is instrument code) but
+#     links NEITHER SDK — the plain-data boundary is enforced structurally: the test
+#     target below links only sampler_core (+ its peaks dep for the AudioSample alias,
+#     the one house precedent wav_trim also relies on). The VST3 shell (src/vst/
+#     reasampler_processor.cpp) marshals MIDI/audio to/from it and is DAW-verified.
+# ---------------------------------------------------------------------------
+# pitch_shift (S16) — the pure duration-preserving PitchShifter (Preserve-engine DSP core).
+# NO VST3/REAPER/SWELL/vendor: a hand-rolled OLA shifter chosen over WDL_SimplePitchShifter
+# because that header drags <windows.h> (via wdltypes.h) into any TU that includes it, which
+# cannot enter the pure sampler_core. Links only peaks (the AudioSample alias). sampler_core
+# depends on it (Voice owns two PitchShifters).
+add_library(pitch_shift STATIC src/vst/pitch_shift.cpp)
+target_include_directories(pitch_shift PUBLIC src src/vst)
+target_link_libraries(pitch_shift PUBLIC peaks)
+
+add_library(sampler_core STATIC src/vst/sampler_core.cpp)
+target_include_directories(sampler_core PUBLIC src src/vst)
+target_link_libraries(sampler_core PUBLIC peaks pitch_shift)
+
 # ---------------------------------------------------------------------------
 # 3) Standalone tests for the pure modules (run without launching REAPER).
 # ---------------------------------------------------------------------------
@@ -548,6 +604,13 @@ add_executable(drag_out_tests tests/test_drag_out.cpp)
 target_link_libraries(drag_out_tests PRIVATE drag_out)
 add_test(NAME drag_out_tests COMMAND drag_out_tests)
 
+# instrument_drop (S17): the drop-and-load vst_chunk blob builder. The round-trip test
+# decodes the base64 back through the instrument's OWN reader (deserializeComponentState) to
+# prove the extension injects exactly what setState accepts — the cross-artifact contract guard.
+add_executable(instrument_drop_tests tests/test_instrument_drop.cpp)
+target_link_libraries(instrument_drop_tests PRIVATE instrument_drop)
+add_test(NAME instrument_drop_tests COMMAND instrument_drop_tests)
+
 add_executable(theme_tests tests/test_theme.cpp)
 target_link_libraries(theme_tests PRIVATE theme)
 add_test(NAME theme_tests COMMAND theme_tests)
@@ -584,6 +647,176 @@ add_executable(card_drag_tests tests/test_card_drag.cpp)
 target_link_libraries(card_drag_tests PRIVATE card_drag)
 add_test(NAME card_drag_tests COMMAND card_drag_tests)
 
+add_executable(assignment_request_tests tests/test_assignment_request.cpp)
+target_link_libraries(assignment_request_tests PRIVATE assignment_request)
+add_test(NAME assignment_request_tests COMMAND assignment_request_tests)
+
+# sampler_core: the S3 heart. Links ONLY sampler_core (+ its peaks dep) — NEITHER the
+# VST3 SDK nor the REAPER SDK — which is the structural proof of the plain-data
+# boundary (a VST3/REAPER type in the core would fail to compile/link here).
+# pitch_shift (S16): the pure Preserve-engine OLA shifter. Links ONLY pitch_shift (+ peaks) —
+# NEITHER SDK — the same plain-data-boundary proof, and specifically the compile-time proof it
+# does NOT drag in the WDL <windows.h> chain the built-in WDL shifter would.
+add_executable(pitch_shift_tests tests/test_pitch_shift.cpp)
+target_link_libraries(pitch_shift_tests PRIVATE pitch_shift)
+add_test(NAME pitch_shift_tests COMMAND pitch_shift_tests)
+
+add_executable(sampler_core_tests tests/test_sampler_core.cpp)
+target_link_libraries(sampler_core_tests PRIVATE sampler_core)
+add_test(NAME sampler_core_tests COMMAND sampler_core_tests)
+
+# ---------------------------------------------------------------------------
+# 2i) Pure VST3-instrument helpers (Phase S1) — NO VST3, NO REAPER, NO SWELL/LICE.
+#     editor_geometry: the IPlugView LICE editor's rectangle layout + hit-test math
+#     (mirror of mode_switch/bank_grid). bridge_marshal: the REAPER VST-host bridge
+#     read marshalling — GetProjExtState result decode + a small JSON string-field
+#     reader (mirror of capture_paths/wav_trim). Both are unit-tested outside the DAW;
+#     the VST3 shell (src/vst/*) that draws/routes/invokes is DAW-verified.
+# ---------------------------------------------------------------------------
+add_library(editor_geometry STATIC src/vst/editor_geometry.cpp)
+target_include_directories(editor_geometry PUBLIC src/vst)
+
+add_library(bridge_marshal STATIC src/vst/bridge_marshal.cpp)
+target_include_directories(bridge_marshal PUBLIC src/vst)
+
+# embed_strip (Phase S6) — PURE layout + hit-test for the embedded TCP/MCP strip: the
+# 128-key span -> zone-segment rects, point -> zone selection, and the level-band fill.
+# The mirror of editor_geometry (whose Rect + contains() it reuses); unit-tested outside
+# the DAW, while the embed shell (src/vst/reasampler_embed.cpp) marshals REAPER's embed
+# messages (paint bitmap + mouse coords) into it. Links editor_geometry for the shared Rect.
+add_library(embed_strip STATIC src/vst/embed_strip.cpp)
+target_include_directories(embed_strip PUBLIC src/vst)
+target_link_libraries(embed_strip PUBLIC editor_geometry)
+
+# sample_map (Phase S4) — PURE mapping logic for the Tier-0 instrument: the live bank
+# blob -> selected sample (via the SHARED bank_book JSON parse, NOT a second parser),
+# interleaved->mono downmix (the Tier-0 channel policy), the Tier-0 chromatic keymap
+# build, and the selected-sample instance-state (de)serialization. Links the three pure
+# modules it composes — bank_book (shared JSON), wav_trim (shared WAV parse), and
+# sampler_core (the Keymap/SampleData it yields) — and NEITHER SDK. The VST3 shell
+# (reasampler_processor.cpp) does the bridge read + file I/O off the audio thread, then
+# calls these; the process callback stays allocation-free.
+add_library(sample_map STATIC src/vst/sample_map.cpp)
+target_include_directories(sample_map PUBLIC src/vst src)
+target_link_libraries(sample_map PUBLIC bank_book wav_trim sampler_core)
+
+# capture_browser (Phase S10) — PURE card-grid + bank-filter-tab layout + hit-test for the
+# capture-first editor's default face. The mirror of mode_switch/editor_geometry: the fiddly
+# grid/tab arithmetic lives here, unit-tested outside the DAW; the editor shell draws each
+# card's peak thumbnail + name + badge and routes clicks into it. Links editor_geometry for
+# the shared Rect + contains(). NEITHER SDK.
+add_library(capture_browser STATIC src/vst/capture_browser.cpp)
+target_include_directories(capture_browser PUBLIC src/vst)
+target_link_libraries(capture_browser PUBLIC editor_geometry)
+
+# keyboard_strip (Phase S10) — PURE key-span<->pixel mapping, root marker, zone-bar rects +
+# edge-grab hit regions, and the drag-delta note resolver for the capture-first editor's
+# keyboard strip (single-capture root-set) and the opt-in Zones panel (S10-Z). The mirror of
+# embed_strip; links editor_geometry for the shared Rect. NEITHER SDK.
+add_library(keyboard_strip STATIC src/vst/keyboard_strip.cpp)
+target_include_directories(keyboard_strip PUBLIC src/vst)
+target_link_libraries(keyboard_strip PUBLIC editor_geometry)
+
+# waveform_view (Phase S11) — PURE frame<->pixel mapping, marker grab regions, drag-delta
+# frame resolver, and the zero-crossing snap for the capture-first editor's waveform surface
+# (draggable start + loop markers over the picked capture's decoded PCM). The mirror of
+# keyboard_strip; links editor_geometry for the shared Rect and peaks for the AudioSample
+# alias the snap scans. NEITHER SDK.
+add_library(waveform_view STATIC src/vst/waveform_view.cpp)
+target_include_directories(waveform_view PUBLIC src/vst src)
+target_link_libraries(waveform_view PUBLIC editor_geometry peaks)
+
+# bank_sync (Phase S9/S8 reader) — PURE decision logic for the instrument's off-audio-thread
+# poll: parse/compare the S9 bank-generation stamp, and the S8 assignment-request CONSUME
+# decision (new-and-resolvable-and-target -> apply; unresolvable -> drop-and-mark; non-target
+# -> stay eligible). The shell owns the timer cadence + side effects (reloadFromBank,
+# setSelectedSampleId, component-state marker); this owns only the yes/no maths, unit-tested
+# outside the DAW. Links assignment_request for the decoded AssignmentRequest it consumes.
+# NEITHER SDK.
+add_library(bank_sync STATIC src/vst/bank_sync.cpp)
+target_include_directories(bank_sync PUBLIC src/vst src)
+target_link_libraries(bank_sync PUBLIC assignment_request)
+
+# browser_scroll (Phase S12) — PURE scroll-window + scrollbar-thumb + type-to-filter-search
+# geometry LAYERED over the S10 capture_browser: the visible-card window, thumb rect +
+# thumb-drag<->offset mapping, and the name-substring filter that composes with the bank
+# filter. The mirror of capture_browser; links capture_browser (for BrowserLayout + the card
+# metrics/cell rect) which pulls editor_geometry transitively. NEITHER SDK.
+add_library(browser_scroll STATIC src/vst/browser_scroll.cpp)
+target_include_directories(browser_scroll PUBLIC src/vst)
+target_link_libraries(browser_scroll PUBLIC capture_browser)
+
+# note_entry (Phase S12) — PURE text->clamped-MIDI-note parse for the direct numeric entry of
+# a zone's low/high/root (decimal integer OR note name under the C4==60 convention, clamped to
+# [0,127]). No dependency beyond the standard library. NEITHER SDK.
+add_library(note_entry STATIC src/vst/note_entry.cpp)
+target_include_directories(note_entry PUBLIC src/vst)
+
+# param_slider (Phase S12 + the S15/S16 control surfaces deferred here) — PURE control-surface
+# layout + hit-test + normalized value<->pixel mapping for the editor parameter panel (the
+# Gate|Trigger + Varispeed|Preserve toggles and the AHDSR / Trigger / pitch-env sliders). The
+# mirror of keyboard_strip; links editor_geometry for the shared Rect. Deliberately engine-free
+# (no sampler_core types) — the shell owns the control-id -> param binding + the value DOMAIN
+# mapping. NEITHER SDK.
+add_library(param_slider STATIC src/vst/param_slider.cpp)
+target_include_directories(param_slider PUBLIC src/vst)
+target_link_libraries(param_slider PUBLIC editor_geometry)
+
+add_executable(editor_geometry_tests tests/test_editor_geometry.cpp)
+target_link_libraries(editor_geometry_tests PRIVATE editor_geometry)
+add_test(NAME editor_geometry_tests COMMAND editor_geometry_tests)
+
+add_executable(bridge_marshal_tests tests/test_bridge_marshal.cpp)
+target_link_libraries(bridge_marshal_tests PRIVATE bridge_marshal)
+add_test(NAME bridge_marshal_tests COMMAND bridge_marshal_tests)
+
+add_executable(embed_strip_tests tests/test_embed_strip.cpp)
+target_link_libraries(embed_strip_tests PRIVATE embed_strip)
+add_test(NAME embed_strip_tests COMMAND embed_strip_tests)
+
+# sample_map: the S4 mapping heart. Links ONLY sample_map (+ its pure deps) — NEITHER
+# the VST3 SDK nor the REAPER SDK — the same structural plain-data-boundary proof the
+# sampler_core test enforces.
+add_executable(sample_map_tests tests/test_sample_map.cpp)
+target_link_libraries(sample_map_tests PRIVATE sample_map)
+add_test(NAME sample_map_tests COMMAND sample_map_tests)
+
+add_executable(capture_browser_tests tests/test_capture_browser.cpp)
+target_link_libraries(capture_browser_tests PRIVATE capture_browser)
+add_test(NAME capture_browser_tests COMMAND capture_browser_tests)
+
+add_executable(keyboard_strip_tests tests/test_keyboard_strip.cpp)
+target_link_libraries(keyboard_strip_tests PRIVATE keyboard_strip)
+add_test(NAME keyboard_strip_tests COMMAND keyboard_strip_tests)
+
+# waveform_view (S11): the pure marker geometry + zero-crossing snap. Links ONLY waveform_view
+# (+ its pure editor_geometry/peaks deps) — NEITHER SDK — the same plain-data-boundary proof.
+add_executable(waveform_view_tests tests/test_waveform_view.cpp)
+target_link_libraries(waveform_view_tests PRIVATE waveform_view)
+add_test(NAME waveform_view_tests COMMAND waveform_view_tests)
+
+# bank_sync (S9/S8 reader): the pure generation-parse + assignment-consume decision. Links
+# ONLY bank_sync (+ its assignment_request dep) — NEITHER SDK — the plain-data-boundary proof.
+add_executable(bank_sync_tests tests/test_bank_sync.cpp)
+target_link_libraries(bank_sync_tests PRIVATE bank_sync)
+add_test(NAME bank_sync_tests COMMAND bank_sync_tests)
+
+# browser_scroll (S12): the pure scroll-window/thumb + search geometry over capture_browser.
+add_executable(browser_scroll_tests tests/test_browser_scroll.cpp)
+target_link_libraries(browser_scroll_tests PRIVATE browser_scroll)
+add_test(NAME browser_scroll_tests COMMAND browser_scroll_tests)
+
+# note_entry (S12): the pure text->clamped-MIDI-note parse for direct numeric entry.
+add_executable(note_entry_tests tests/test_note_entry.cpp)
+target_link_libraries(note_entry_tests PRIVATE note_entry)
+add_test(NAME note_entry_tests COMMAND note_entry_tests)
+
+# param_slider (S12 + S15/S16 control surfaces): the pure control-panel layout + slider/toggle
+# value<->pixel mapping the editor parameter surface draws + routes against.
+add_executable(param_slider_tests tests/test_param_slider.cpp)
+target_link_libraries(param_slider_tests PRIVATE param_slider)
+add_test(NAME param_slider_tests COMMAND param_slider_tests)
+
 # ---------------------------------------------------------------------------
 # 4) The REAPER extension — a loadable module (dlopen'd by REAPER, not linked).
 # ---------------------------------------------------------------------------
@@ -624,9 +857,11 @@ add_library(reaper_reasampler MODULE
     src/lane_keys.cpp
     src/item_read.cpp
     src/actions.cpp
+    src/ingest.cpp
     src/bank_book.cpp
     src/owned_manifest.cpp
     src/drag_out_win.cpp
+    src/instrument_drop_win.cpp
     src/action_bar.cpp
     src/footer_bar.cpp
     src/overflow_menu.cpp
@@ -635,7 +870,7 @@ add_library(reaper_reasampler MODULE
     src/card_meta.cpp
     src/card_drag.cpp
 )
-target_link_libraries(reaper_reasampler PRIVATE bank_model capture_paths peaks bank_grid mode_switch tab_strip view_mode_model insert_plan render_settings batch_capture tail_control realtime_record bank_book wav_trim owned_manifest prune_reconcile prune_button app_version provenance action_buttons drag_out theme component_geometry action_bar footer_bar overflow_menu mode_enable tooltip card_meta card_drag)
+target_link_libraries(reaper_reasampler PRIVATE bank_model capture_paths peaks bank_grid mode_switch tab_strip view_mode_model insert_plan render_settings batch_capture tail_control realtime_record bank_book wav_trim owned_manifest prune_reconcile prune_button app_version provenance action_buttons drag_out instrument_drop theme component_geometry action_bar footer_bar overflow_menu mode_enable tooltip card_meta card_drag assignment_request bank_sync)
 target_include_directories(reaper_reasampler PRIVATE ${SDK_INC} ${WDL_INC})
 # OUTPUT_NAME is channel-derived (Phase V, V4): "reaper_reasampler" (stable, default) or
 # "reaper_reasampler_beta" (beta). REAPER dlopen's any reaper_* module, so both channels'
@@ -671,3 +906,122 @@ else()
     #   php ${WDL_INC}/swell/mac_resgen.php src/resource.rc
     # target_sources(reaper_reasampler PRIVATE src/resource.rc_mac_dlg.h)  # generated
 endif()
+
+# ===========================================================================
+# 5) The ReaSampler VST3 instrument — the SECOND build artifact (Phase S1).
+#
+# Windows-only, VST3-only, REAPER-only (D5). A separate native VST3 plugin the user
+# instantiates on an instrument track. Additive: the reaper_reasampler target above
+# builds unchanged. This is the S1 opening spike — a silent-but-loading
+# SingleComponentEffect skeleton, an IPlugView<->LICE editor, and the REAPER VST-host
+# bridge read — not yet a sampler.
+#
+# ONE-TIME SDK SUBMODULE SETUP (see README / .gitmodules): the vst3sdk superproject is
+# vendored pinned to tag v3.7.9_build_61; only three of its sub-submodules are needed
+# (VSTGUI/examples/tests are NOT). After `git submodule update --init vendor/vst3sdk`:
+#     cd vendor/vst3sdk && git submodule update --init pluginterfaces base public.sdk
+# ===========================================================================
+set(VST3_SDK ${CMAKE_CURRENT_SOURCE_DIR}/vendor/vst3sdk)
+# The VST3 module needs the nested vst3sdk slice (pluginterfaces / base / public.sdk)
+# checked out — the one-time step documented above. When it is absent (a fresh clone
+# that ran only the top-level `git submodule update --init`), skip the module rather than
+# fail configure on missing sources: the pure geometry/mapping libraries + their CTest
+# targets still build and test without the SDK. Probe one representative source file.
+if(WIN32 AND EXISTS "${VST3_SDK}/public.sdk/source/main/pluginfactory.cpp")
+
+    # --- 5a) The bounded slice of the Steinberg VST3 SDK this spike needs. --------
+    # Enumerated (not add_subdirectory of the whole SDK) to keep the build hermetic and
+    # lean, matching the project's two-submodule discipline: no VSTGUI, no examples, no
+    # SDK-global CMake helpers/install machinery. Pinned to tag v3.7.9_build_61, so the
+    # list is fixed. If the SDK tag is bumped, re-verify this set.
+    add_library(vst3_sdk STATIC
+        # pluginterfaces/base — FUnknown, IIDs, string table, ustring.
+        ${VST3_SDK}/pluginterfaces/base/funknown.cpp
+        ${VST3_SDK}/pluginterfaces/base/coreiids.cpp
+        ${VST3_SDK}/pluginterfaces/base/conststringtable.cpp
+        ${VST3_SDK}/pluginterfaces/base/ustring.cpp
+        # base/source — FObject, strings, buffers, streamer, debug, IIDs, update handler.
+        ${VST3_SDK}/base/source/fobject.cpp
+        ${VST3_SDK}/base/source/fstring.cpp
+        ${VST3_SDK}/base/source/fbuffer.cpp
+        ${VST3_SDK}/base/source/fstreamer.cpp
+        ${VST3_SDK}/base/source/fdebug.cpp
+        ${VST3_SDK}/base/source/baseiids.cpp
+        ${VST3_SDK}/base/source/updatehandler.cpp
+        ${VST3_SDK}/base/thread/source/flock.cpp
+        # public.sdk/source/vst — the SingleComponentEffect base + its deps. NOTE:
+        # vstsinglecomponenteffect.cpp #includes vsteditcontroller.cpp (unity-style), so
+        # vsteditcontroller.cpp must NOT be listed separately (double definition).
+        ${VST3_SDK}/public.sdk/source/vst/vstsinglecomponenteffect.cpp
+        ${VST3_SDK}/public.sdk/source/vst/vstcomponentbase.cpp
+        ${VST3_SDK}/public.sdk/source/vst/vstbus.cpp
+        ${VST3_SDK}/public.sdk/source/vst/vstparameters.cpp
+        ${VST3_SDK}/public.sdk/source/vst/vstinitiids.cpp
+        # public.sdk/source/common — CPluginView (IPlugView base) + IIDs.
+        ${VST3_SDK}/public.sdk/source/common/pluginview.cpp
+        ${VST3_SDK}/public.sdk/source/common/commoniids.cpp
+        # public.sdk/source/main — the class-factory (GetPluginFactory) support. NOTE:
+        # dllmain.cpp + moduleinit.cpp (which carry the InitDll/ExitDll dll exports) are
+        # compiled into the MODULE target directly, NOT here: their SMTG_EXPORT_SYMBOL
+        # functions have no internal referrer, so the linker strips them from a static
+        # lib. Compiling them into the module keeps the exports.
+        ${VST3_SDK}/public.sdk/source/main/pluginfactory.cpp
+    )
+    target_include_directories(vst3_sdk PUBLIC ${VST3_SDK})
+    # The SDK requires exactly one of RELEASE / DEVELOPMENT (fdebug.cpp keys off it).
+    target_compile_definitions(vst3_sdk PUBLIC $<IF:$<CONFIG:Debug>,DEVELOPMENT=1,RELEASE=1>)
+
+    # --- 5b) The VST3 module (loadable .vst3 DLL). -------------------------------
+    add_library(reasampler_vst MODULE
+        src/vst/vst_entry.cpp
+        src/vst/reasampler_processor.cpp
+        src/vst/reasampler_editor.cpp
+        src/vst/reasampler_embed.cpp
+        src/vst/reaper_bridge.cpp
+        # SDK module entry — compiled into the module (not the static lib) so the
+        # InitDll/ExitDll dll exports survive the link (see vst3_sdk note above).
+        ${VST3_SDK}/public.sdk/source/main/dllmain.cpp
+        ${VST3_SDK}/public.sdk/source/main/moduleinit.cpp
+        ${LICE_SRC}
+    )
+    # editor_geometry + bridge_marshal: the pure spike helpers. sample_map (S4): the pure
+    # bank->keymap mapping + state (de)ser the processor drives off the audio thread;
+    # linking it pulls its pure deps (bank_book, wav_trim, sampler_core, bank_model,
+    # peaks) transitively. capture_paths: the shared M4 path resolution (resolveBankFile /
+    # projectDirOfRpp) the bridge + processor use. Its PUBLIC include dirs (src, src/vst)
+    # give the shell TUs their headers (ext_keys.h, bank_book.h, sampler_core.h, ...).
+    # embed_strip (S6): the pure inline-strip layout + hit-test the embed shell marshals
+    # into; it links editor_geometry transitively (shared Rect).
+    # app_version: ext_keys.h's channel-derived namespace accessor (V4) delegates to it, so
+    # the instrument reads the SAME namespace the extension writes; its PUBLIC include dir
+    # (build/generated) carries version_generated.h for the channel bit.
+    # capture_browser + keyboard_strip (S10): the pure card-grid/tab + keyboard-strip
+    # geometry the capture-first editor draws + hit-tests against; both link editor_geometry
+    # transitively (shared Rect).
+    # waveform_view (S11): the pure frame<->pixel marker geometry + zero-crossing snap the
+    # editor's waveform surface draws + hit-tests against; links editor_geometry + peaks
+    # transitively (shared Rect + AudioSample).
+    # bank_sync (S9/S8 reader): the pure generation-compare + assignment-consume decision the
+    # processor's off-thread poll runs; links assignment_request transitively (the decoded
+    # request it consumes) — the same key the extension writes, shared via the pure module.
+    # browser_scroll + note_entry + param_slider (S12 + S15/S16 control surfaces): the pure
+    # scroll/search geometry over the capture browser, the numeric-note-entry parse, and the
+    # control-panel layout + slider/toggle value<->pixel mapping the editor's parameter surface
+    # draws + routes against. browser_scroll pulls capture_browser transitively; param_slider +
+    # note_entry link editor_geometry / the stdlib only. All engine-free, DAW-verified in the shell.
+    target_link_libraries(reasampler_vst PRIVATE vst3_sdk editor_geometry bridge_marshal
+        sample_map capture_paths embed_strip app_version capture_browser keyboard_strip
+        waveform_view bank_sync browser_scroll note_entry param_slider)
+    # SDK_INC gives reaper_vst3_interfaces.h + reaper_plugin_functions.h for the bridge;
+    # WDL_INC gives LICE for the editor. The VST3 SDK headers come from vst3_sdk PUBLIC.
+    target_include_directories(reasampler_vst PRIVATE ${SDK_INC} ${WDL_INC})
+    # A .vst3 is a DLL with a .vst3 extension and no lib-prefix. OUTPUT_NAME is the on-disk
+    # product name, channel-forked (S18): reasampler_9000.vst3 (stable, byte-identical to
+    # pre-S18) / reasampler_9000_beta.vst3 (beta) — driven by REASAMPLER_VST_OUTPUT_NAME set
+    # from the ONE channel decision above, mirroring the extension's REASAMPLER_OUTPUT_NAME
+    # and matching app_version::vstOutputName(). The two channels install side-by-side; the
+    # per-channel VST3 class UID (reasampler_vst.h) keeps a saved instance rebinding to its
+    # own channel (save-rename-reopen is a DAW-verify).
+    set_target_properties(reasampler_vst PROPERTIES PREFIX "" SUFFIX ".vst3"
+        OUTPUT_NAME "${REASAMPLER_VST_OUTPUT_NAME}")
+endif()

CONTEXT.md

@@ -1289,6 +1289,524 @@ someday-note. It is polish, not a Tier-0 need, so it sequences last in the phase
 is on the roadmap. **Must-verify before build:** the `IReaperUIEmbedInterface` contract
 and embed message/lifecycle against `vendor/reaper-sdk/sdk/reaper_plugin_fx_embed.h`.
 
+## Channel mode — mono | stereo (D-E, decided 2026-07-26; PLAN.md S7)
+
+**Decided direction: the instrument gets a per-instance channel-mode toggle — 1 (mono) or
+2 (stereo) — that negotiates the REAPER audio bus automatically.** Captures are often
+stereo; the current mono downmix is a Tier-0 simplification, not a permanent shape.
+
+- **Mono mode keeps today's path.** The decode-side downmix stands: a stereo source in
+  mono mode downmixes (the existing policy), a mono source plays as-is. No engine change
+  for mono.
+- **Stereo mode is an S3-core extension, not a shell hack (honest).** The S3 core is
+  **mono-per-sample by design today** — `SampleData::frames` is one mono stream,
+  `Voice::renderFrame` returns a single value, `VoiceEngine::render` writes one channel.
+  Stereo mode grows the core a **channel dimension**: 2-channel decoded PCM, per-voice
+  **stereo** render (per-channel fractional read + linear interpolation + loop), and a
+  per-channel mix in the engine. Mono stays the degenerate (single-channel) case, so
+  existing mono behavior is unchanged. This is why S7 sequences first after the editor/embed
+  work: it touches the engine Daniel smoke-tests.
+- **Where the toggle lives.** Per-instance component state (setState/getState), alongside
+  the selected sample — a **performance choice the instrument owns**, never written to the
+  bank (D-B: not a file fact). Default preserves current behavior (mono).
+- **Cross-mode policy (settled).** Mono source + stereo mode → **dual-mono** (same signal
+  both channels, centered). Stereo source + mono mode → **downmix** (the existing
+  decode-side policy). The bank's per-sample channel-count intrinsic (already on `Sample`)
+  tells the shell how many channels to decode into `SampleData`.
+- **Bus negotiation (the "works with the REAPER bus automatically" requirement).** The VST3
+  implements `setBusArrangements` so the output bus reports mono or stereo per the
+  instance's channel mode, and REAPER's routing follows without manual channel wiring.
+  **Must-verify before build:** the `setBusArrangements` / `getBusArrangement` contract and
+  REAPER's mono/stereo instrument-bus expectations against the vendored Steinberg SDK +
+  `reaper_vst3_interfaces.h`.
+
+## Sampling modes — Trigger vs Gate + pitch envelope (S15/S16; core + editor)
+
+**Daniel's directive (2026-07-26, verbatim):** *"Sampling mode: Trigger vs Gate. Gate has
+an AHDSR envelope. Trigger has fade in, % length, and fade out. Both modes have modifiable
+start point, Gate has modifiable loop points too. In addition to amp env, there will be a
+pitch envelope/curve (AD?) which is off by default."* The feature set is **settled**; two
+forks (S15-F1 choke, S15-F2 param granularity) are flagged with leans below.
+
+**Daniel's S16 correction (2026-07-26, verbatim):** *"isn't that ratio stuff going to change
+the playback rate? I want duration-preserving repitching."* Correct — the `readPos_ += ratio_`
+path is **varispeed** (pitch and duration coupled). S16 is revised from "pitch envelope only"
+into a **pitch-engine mode (Varispeed vs Preserve) + pitch envelope** (see §Pitch engine
+modes below). Two new S16 forks are flagged: **S16-F1** (the engine default — lean Preserve)
+and **S16-F2** (the Preserve implementation — lean `WDL_SimplePitchShifter` first, hand-rolled
+held). The prior WDL finding that dismissed `WDL_SimplePitchShifter` is **corrected in place**
+below (duration-preserving is now the requirement, so that shifter is the Preserve candidate).
+
+### Play mode — Gate vs Trigger (S15)
+
+Each played sample carries a **play mode** — a per-sample/per-zone **performance choice**
+(D-B, instrument-owned, never a bank fact). Two modes, precisely:
+
+- **Gate — classic held note (grows the current path).** Note-on enters the amp envelope;
+  note-off enters release; a **sustain loop** applies for held notes (S11's draggable loop
+  markers are Gate-mode UI). The current core envelope is **ADSR**; Gate adds a **Hold**
+  stage → **AHDSR**: `0→1` over attack, **hold at 1** over `holdFrames`, `1→sustain` over
+  decay, hold sustain until note-off, `level→0` over release. **`holdFrames == 0` is
+  exactly today's ADSR** — a back-compat degenerate, no behavior change for existing Gate
+  play. Segment math is the existing linear-ramp idiom (`AdsrEnvelope::tick`) with one new
+  stage inserted between Attack and Decay.
+- **Trigger — one-shot drum-pad.** Note-on fires playback of a defined **% of sample
+  length** with a **fade-in** and **fade-out** ramp; **note-off is ignored** (the voice
+  plays through); **no sustain loop**. Envelope math (distinct from AHDSR): play the frame
+  span `[startFrame, playEnd)` where `playEnd = startFrame + round(lengthFraction·(frames −
+  startFrame))`, `lengthFraction ∈ (0,1]`; amplitude ramps `0→1` over `fadeInFrames`
+  (fade-in) at the head and `1→0` over `fadeOutFrames` anchored to `playEnd` (fade-out),
+  unity between; fades clamp so `fadeInFrames + fadeOutFrames ≤ play length`. The voice
+  frees when `readPos_ ≥ playEnd` (mirror of the current run-off-end idle). **Fade curve
+  default: equal-power** (constant-power `sin`/`cos` — click-free on one-shots); linear is a
+  build-time residual. **Note-off in Trigger is a no-op** (choke is held — fork S15-F1).
+
+**Both modes: modifiable start point.** Playback begins at `startFrame` (a frame offset into
+the sample, clamped `0 ≤ startFrame < frames`), not always frame 0. This is the voice's
+initial `readPos_`; the existing per-frame `readPos_ += ratio_` read and linear-interp/loop
+machinery are otherwise unchanged. Gate additionally has **modifiable loop points** (already
+the S2 loop intrinsic + S11 override); Trigger has none (it is a one-shot).
+
+**Voice-stealing interaction (unchanged).** The S3 stealing policy (oldest-in-release, else
+oldest-overall) is mode-agnostic — a Trigger one-shot is a normal active voice until it runs
+off `playEnd`; it can be stolen like any voice. No new stealing rule.
+
+**Confirmed from the core (`sampler_core.cpp`):** the read loop advances `readPos_` by an
+arbitrary `ratio_` per frame with 2-point linear interpolation, and the amp is a per-frame
+`env_.tick()` multiply — so both the AHDSR hold stage and the Trigger fade/%-length envelope
+are **per-frame amplitude functions** over the existing read machinery, and the start point
+is just a non-zero initial `readPos_`. No resampler or voice-lifecycle rewrite is needed.
+
+**Parameter ownership (D-B).** The play mode + its params (Gate: AHDSR; Trigger: %-length +
+fade-in + fade-out; both: start point) attach to the **capture selection / zone** and live
+in the instrument's **performance map** (component state, version-bumped, back-compat: a
+truncated/older blob defaults to **Gate, hold=0, start=0, no fades = exactly today**). Start
+point joins `rootOverride` / loop-override as another per-`PerformanceZone` optional
+override; a per-zone `PlayMode` + param struct is added additively. **Fork S15-F2 (flagged):**
+per-capture-selection *and* per-zone, or per-zone only with the single-capture case as a
+one-zone map? **Lean: per-zone only** — the single capture is already a one-zone map
+(S10-Z's back-compat lift), so one storage site serves both; flagged because it touches
+S10's single-capture setup surface shape.
+
+**Editor (mode-aware, on the S11 waveform surface).** Gate shows draggable **start + loop
+markers**; Trigger shows **start + %-length end + fade-in/out** handles — same waveform, same
+pure `frame↔pixel` + marker-grab geometry module (S11), mode switches which markers draw. A
+**mode toggle** per capture/zone sits in the S10 guided setup / S10-Z Zones panel. Every edit
+commits **off-thread** via `commitMapAndReload`; the instrument stays a **read-only bank
+consumer** (mode/params are performance map, never written to `Sample` or the bank).
+
+### Pitch engine modes — Varispeed vs Preserve (S16)
+
+**Daniel's correction (2026-07-26, verbatim):** *"isn't that ratio stuff going to change the
+playback rate? I want duration-preserving repitching."* Correct: the `readPos_ += ratio_`
+resampling path is **Varispeed** — pitch and duration are coupled (an octave up halves the
+note's duration). Daniel wants **duration-preserving** repitch. So S16 grows a per-voice/
+per-zone **pitch-engine mode**, not just a pitch envelope:
+
+- **Varispeed engine (current path).** `ratio_ = pitchRatio(note,root)`, `readPos_ += ratio_`
+  with 2-point linear interp — resampling that couples pitch and duration. This is the
+  **classic sampler / RS5K** behavior and today's shipped S3/S5 output. Cheap, zero-latency.
+  Musically right for **drums / one-shots** (pitch-down-lengthens-the-hit is a feature there).
+- **Preserve engine (duration-preserving).** The read advances at the **source** rate
+  (duration held) while a **pitch shifter** transposes the output by `2^((note−root)/12)`.
+  Musically right for **tempo-locked loops and phrases** — a transposed loop still lines up to
+  the bar. Since captured banks are project slices (loop/phrase-heavy), this is the default
+  lean (fork S16-F1).
+
+Mode is **per-`PerformanceZone` performance state (D-B)** — instrument-owned, never a bank
+fact — additive/version-bumped (absent/older blob → the S16-F1 default). A per-zone
+**Varispeed/Preserve toggle** surfaces in the S10 guided setup / S10-Z Zones panel.
+
+**Preserve engine implementation (fork S16-F2).** Two RT-disciplined routes behind the
+`PitchEngine::Preserve` seam (identical contract either way):
+- **(a) `WDL_SimplePitchShifter`** (`vendor/WDL/WDL/simple_pitchshift.h`) — a per-voice
+  time-domain OLA shifter. Under the duration-preserving directive this is **the right
+  category** (see the corrected WDL finding below). `set_shift(2^(semi/12))` for pitch,
+  `set_tempo(1.0)` to hold duration — pitch and duration are separately controllable. **Lean:
+  route (a) first** (low-cost proof), with two costs owned in the build: an inherent
+  **onset latency** (~half-window, ~25 ms @ the 50 ms quality-0 window; pre-warm at voice-
+  allocation, and it lands on sustained/loop material where least harmful) and a **queue-growth
+  allocation** hazard in `BufferDone` (`WDL_Queue::Add`) that is settled by a silence pre-warm
+  at voice-allocation so no `process`-thread allocation occurs in steady state.
+- **(b) hand-rolled pure `pitch_shift` OLA/granular module** (house pattern — CTest-testable,
+  no REAPER/VST3/WDL type at the boundary) — **held** as the quality/latency upgrade if the
+  SimpleWindowed warble or onset lag proves musically unacceptable.
+
+**`WDL_Resampler` is not a Preserve engine** — it is a *resampler* (couples duration); it
+remains a held **Varispeed-quality** upgrade only. **elastique is NOT available** (licensed
+zplane, not vendored — restated). JUCE / rubberband / signalsmith are **new-dependency forks
+carrying D-A weight** (bare-VST3-no-framework is the locked D-A) — **not proposed**.
+
+**S15 × S16 interaction (Preserve consumes S15's source-frame read).** S15's amplitude
+semantics are defined over the voice's **source-frame** timeline; the Preserve engine wraps
+that read and transposes the output, so:
+- **Trigger %-length** stays a source-frame fact (`playEnd = start + round(lengthFraction·
+  (frames − start))`); under Preserve its **wall-clock is stable under transpose** — *cleaner*
+  than Varispeed, where transposing a Trigger also scales its audible length.
+- **Gate sustain loop** — under Preserve, **loop the source read** (the `[loopStart, loopEnd)`
+  source-frame region) and feed the looped stream into the shifter, which transposes the
+  **output**. Contract: *loop the source, shift the output*; loop points stay source-frame
+  facts (S11 markers unchanged). Under Varispeed the loop read itself carries the pitch.
+- **Start point** is a source-frame offset in both engines (engine-independent).
+
+### Pitch envelope — AD, off by default, engine-aware (S16)
+
+A per-voice **pitch modulation curve** riding on top of whichever engine — a short **AD**
+(attack-decay) envelope that biases pitch over time. **Off by default** (so existing playback
+is bit-identical under the same engine). The classic use is a percussive **pitch drop**.
+
+- **Shape (lean, build-time residual): two-segment AD** — at note-on the pitch offset rises
+  to `peakSemitones` over `attackFrames`, then falls to 0 (base pitch) over `decayFrames`.
+  A **zero attack** gives the pure "start high, drop to base" percussive drop.
+- **Range: semitones (±).** `peakSemitones` is signed; default depth range noted at build.
+- **Applied per engine.** Under **Varispeed** the offset is a **per-frame multiply of
+  `ratio_`** by `2^(pitchEnvSemitones(frame)/12)` (the effective read increment varies frame-
+  by-frame at no structural cost — the same per-frame `tick()` idiom as the amp envelope,
+  RT-safe, no `process` allocation). Under **Preserve** the offset is **added to the shifter's
+  shift amount** — `set_shift(2^((note−root + pitchEnvSemitones(frame))/12))` — bending pitch
+  without touching duration. Per-voice (polyphonic notes each run their own).
+- **Ownership + editor.** Per-zone instrument performance-map state (D-B), additive/version-
+  bumped (absent → disabled). Editor exposure folds into the S12 ADSR-editor tier: attack +
+  decay + a ±semitone depth control, default-off (discoverable but inert until enabled).
+
+### WDL pitch/resample surface — corrected finding (feeds S16, not a committed point)
+
+**Corrected 2026-07-26 (Daniel's duration-preserving directive).** The prior sweep dismissed
+`WDL_SimplePitchShifter` as "wrong tool (duration-preserving)". Under the directive,
+**duration-preserving is the requirement**, so that header is the Preserve-engine candidate,
+not a mismatch — a real viability assessment replaces the dismissal.
+
+The **full** vendored WDL pitch/resample surface is `vendor/WDL/WDL/resample.h` and
+`vendor/WDL/WDL/simple_pitchshift.h` — the **only** two pitch/resample headers; there is
+**no** elastique / formant-preserving anywhere in the tree. Honest findings:
+
+- **`WDL_Resampler` (`resample.h`) — sinc/linear resampler, RT-suitable.**
+  `SetMode(interp, filtercnt, sinc, sinc_size≤64, sinc_interpsize)`; streaming
+  `ResamplePrepare`/`ResampleOut` with `Prealloc`. Its sinc mode beats the core's 2-point
+  linear interp for **Varispeed** base-repitch quality (less aliasing on large transpositions)
+  at a real CPU cost. **A resampler couples duration** → a Varispeed-quality option, **not a
+  Preserve engine.** Held as a Tier-2/3 Varispeed-quality toggle; not committed.
+- **`WDL_SimplePitchShifter` (`simple_pitchshift.h`) — time-domain OLA, duration-preserving —
+  the S16 Preserve-engine candidate (fork S16-F2 route a).** Viability from the header:
+  - **API shape:** push/pull, block-based. `GetBuffer(size)` returns an input buffer to fill;
+    `BufferDone(filled)` runs the OLA shift and queues output; `GetSamples(req, buf)` pulls
+    from the queue. Config: `set_srate`, `set_nch`, **`set_shift(ratio)` (pitch, duration-
+    preserving)**, `set_tempo(scale)` (an *independent* duration knob — Preserve uses
+    `set_tempo(1.0)`), `SetQualityParameter(q)` (selects window/overlap ms from a fixed table).
+  - **Per-voice instantiability / memory:** modest. `m_psbuf` is an OLA ring of `bsize·nch`
+    where `bsize = window_ms · 0.001 · srate` (≈ 2205 frames at 50 ms / 44.1 kHz ≈ a few
+    KB/voice), plus `m_inbuf` (one input block) and a bounded `m_queue`. `m_rsbuf` allocates
+    only when `set_tempo ≠ 1` (unused in Preserve). One instance per voice is cheap in memory.
+  - **RT-safety:** allocations occur in `BufferDone` — `m_psbuf.Resize` (once, when
+    `bsize·nch` first sets, at a fixed quality/srate/nch — pre-warmable) and `m_queue.Add`
+    (grows only until the push/pull cadence reaches steady state). **Pre-warm at voice-
+    allocation** (run silence through once so `m_psbuf` sizes and `m_queue` settles); after
+    that no `process`-thread allocation. No locks. **RT-viable with the pre-warm discipline.**
+  - **Latency:** inherent ~half-window (initial `m_pspos = bsize/2` → ~25 ms @ 50 ms window)
+    plus fill-up — a **real note-onset lag**. This is the load-bearing cost. Mitigation:
+    pre-warm; and Varispeed (zero-latency) serves the tight-transient one-shot material, so the
+    lag lands on sustained/loop material where least harmful. Smaller-window quality settings
+    (the table goes to 3–10 ms) trade latency for more warble.
+  - **Quality:** basic — this is REAPER's "SimpleWindowed" mode. Audible warble on large
+    transpositions; **`set_formant_shift` is an explicit empty stub** → no formant preservation.
+    Usable for loop/phrase Preserve; replaceable by route (b) if not.
+  - **CPU / polyphony:** `PitchShiftBlock` is O(length) per block — a few mults + one OLA
+    crossfade branch per frame, **no FFT**. Per-voice cost is modest; **N polyphonic voices
+    each running one is feasible** within RT discipline. If the aggregate cost is material, a
+    **Preserve-mode-specific voice cap** (below the Varispeed cap) is the pressure valve —
+    flagged in Verify, set from measured per-voice budget at build.
+- **Formant-preserving / studio-grade time-stretch (elastique-class): NOT in WDL, confirmed.**
+  REAPER's elastique is **licensed (zplane)**, not in the vendored tree (grep found only
+  unrelated libpng/giflib string matches). Formant-correct duration-preserving repitch is
+  **unavailable without a new third-party dependency** (JUCE / rubberband / signalsmith each a
+  new-dependency fork with D-A weight — not proposed). Stated, not worked around.
+- **Recommendation:** the **Preserve** engine (S16-F2) is `WDL_SimplePitchShifter` (route a,
+  low-cost proof) or a hand-rolled pure `pitch_shift` module (route b, held quality upgrade).
+  The **pitch-envelope** modulation stays hand-rolled over whichever engine (a per-frame
+  `ratio_` multiply under Varispeed, a per-frame shift-amount add under Preserve).
+  `WDL_Resampler` (sinc) is a held **Varispeed-quality** upgrade only.
+
+### Sequencing (S15/S16 against S7 stereo, S10 editor)
+
+S15 and S16 are **S3-core extensions** — they touch the engine Daniel smoke-tests, like S7.
+They are **channel-count-agnostic by construction**: the play-mode envelope is a per-frame
+**amplitude** function, and both pitch engines carry the channel dimension internally — the
+**Varispeed** path is a per-frame per-channel read-rate scalar, and the **Preserve** shifter
+is **`set_nch`-aware** (one shifter instance per voice transposes all its channels together).
+So S15/S16 **compose cleanly with S7's channel dimension** rather than conflicting: S7 adds a
+channel axis to the read/mix; S15 adds an amplitude-shape axis; S16 adds a pitch-engine +
+read-rate axis; all orthogonal. **Recommended order:** **S15 before S16** (S16 reuses S15's
+per-voice param-plumbing + component-state version bumps; landing S15's `PlayMode`/param
+struct first gives S16 a home to hang the pitch-engine mode + pitch-env params on). **S16 is
+now meaningfully heavier than the prior "just an envelope" framing** — the Preserve engine is
+a per-voice DSP object with its own RT budget, pre-warm, and possible voice-cap; treat S16's
+Preserve-engine point as the phase's next real DSP spike, not a thin add-on. **S15/S16
+relative to S7:** no hard dependency — spec them so the envelope/mode code never assumes a
+channel count (it operates per-frame, pre-mix; the Preserve shifter is `set_nch`-driven), and
+S7 can land before, after, or interleaved. **Relative to S10 (editor):** S15's mode toggle +
+Trigger handles and S16's AD control **surface through** the S10/S11 waveform + guided-setup
+work, so the *core* halves of S15/S16 can land independently of the editor, with the editor
+surfacing following S10/S11 (the same way S12's ADSR editor follows the S3 ADSR math). Land
+the **core** engine work (mode split, start point, %-length/fades, pitch-env modulation) as
+soon as it is ready — it is testable in CTest without the editor — and wire the UI as the
+S10/S11 surfaces mature. **Land S15/S16 core after S10's policy-reversal is settled** only if
+sharing the same component-state blob would otherwise churn the version tag twice; otherwise
+they are independent.
+
+## Ingest through the bank — the extension owns ingest (decided "option 1", 2026-07-26; PLAN.md S8)
+
+**Decided: loading a sample into the sampler is ONE gesture — capture/import-into-bank AND
+auto-assign to the active sampler instance — and the *extension* owns it.** The instrument
+stays a **read-only bank consumer**; it never captures and never imports. The extension is
+the right owner: it has arrange access, Media-Explorer access, and the drop-target surface
+on its own docked panels. Ingest lives in the *extension* codebase (actions + `bank_panel` +
+capture/import add-path), routing through the existing capture add-path and the live
+`"reasampler"` seam the instrument already reads.
+
+**The three ingest surfaces, with the honest SDK reality (verified against the vendored
+headers):**
+
+- **Arrange capture → bank → assign.** A one-click action captures the selected item /
+  time-selection into the bank (reusing the existing capture request path —
+  `CountSelectedMediaItems` / `GetSelectedMediaItem` + `GetSet_LoopTimeRange` are already the
+  capture inputs) and assigns the resulting `Sample` id to the target instance. **It never
+  inserts a timeline item** — the capture/placement separation is load-bearing; assignment
+  is a bank-index + instance-selection act, not a placement.
+- **Media Explorer import → bank → assign.** The Media-Explorer surface is **thin**:
+  `OpenMediaExplorer` (open/select a file) and `MediaExplorerGetLastPlayedFileInfo` (read the
+  *one* last-played/selected file path + its selection range/pitch/vol/rate) are the whole
+  contract. There is **no** enumerate-selected-files and **no** register-a-drop-handler-on-
+  the-Media-Explorer API. So ME import is **single-file, pull-on-action** — an action fired
+  while a file is selected in the ME — not a push/drop from inside the ME. **Spike:** confirm
+  `MediaExplorerGetLastPlayedFileInfo` returns a usable path+range for a merely-*selected*
+  (not-yet-played) file, or whether a play is required first.
+- **Drag-and-drop onto ReaSampler surfaces.** REAPER exposes **no** drag-drop registration
+  API. Drop handling is on ReaSampler's *own* HWNDs via SWELL/Win32 (`WM_DROPFILES` /
+  `IDropTarget` on the docked `bank_panel` HWND — the surface the panel already owns) → ingest
+  → assign. **Assess-and-flag (spike, not promised):** a drop *onto the VST3 editor window* —
+  whether the `IPlugView` HWND can accept an OS file drop and **relay it to the extension as
+  a bank-ingest request** (the instrument does not ingest; it forwards a request over an
+  agreed seam). This crosses the two-artifact boundary and the relay is unproven; if gnarly,
+  drop-onto-panel is the shipped path and drop-onto-editor is deferred.
+
+**The assign seam.** The ingest action names the target instance (lean: the active/
+last-focused instance, discovered via the host context the bridge already resolves) and hands
+it the new sample id — the same instance-owned selection state S4 already persists, so a
+reload picks it up. With the change-detection seam (below) the assignment refreshes
+hands-free; without it the ingest action pokes the target instance's reload directly.
+
+**Guardrail (load-bearing, restated):** ingest is an *extension* act. Any instrument code
+path that captures, imports, inserts a timeline item, or writes back into the bank is a bug —
+the instrument reads and plays only.
+
+## Bank-generation change-detection — hands-free refresh (decided 2026-07-26; PLAN.md S9)
+
+Instances reference sample **ids**. So a **recapture** (M10) landing under the same id — or
+an **ingest** (S8) touching the active bank — should refresh playing instances **hands-free**,
+without re-opening each editor. The missing trigger: a **bank-generation counter** in
+`"reasampler"` ext-state.
+
+- **Writer (extension).** A monotonic **bank-generation counter**, stamped into
+  `"reasampler"` ext-state under a new forever-stable `ext_keys.h` constant, bumped on every
+  bank-content mutation that changes what an instance would play (capture add, recapture-in-
+  place, sample-remove, move/copy affecting the active bank). Additive to the persist blob;
+  defaults to 0 for projects saved before the stamp exists.
+- **Reader (instrument).** Poll the generation over the bridge on a safe **off-audio-thread
+  cadence** (a UI/timer tick, **never** `process`), compare to the last-seen value, and call
+  the existing off-thread `reloadFromBank()` on change — reusing S4's atomic pointer-swap
+  handoff (graveyard-reclaim) so a mid-play refresh does not glitch. No new audio-thread work;
+  no allocation in `process`.
+- **Cadence + safety.** A low-frequency UI timer, coalescing multiple bumps between polls into
+  one reload (build-time residual). The read already tolerates a stale value by design (it
+  reloads on the *next* poll). **Must-verify before build:** no torn-read hazard on the single
+  integer generation key for a bridge read on the instrument's UI/timer thread concurrent with
+  an extension write.
+
+This seam serves **both** S8 ingest and M10 recapture; the writer side is extension-only and
+independent of S8, so it can land alongside either.
+
+## Design-system foundation — moved to Phase L (2026-07-26)
+
+> **The visual design language moved out of Phase S into its own Phase L.** The
+> design-system content that stood here (the toolkit assessment, the shared LICE drawing
+> kit **S0-DS**, and the dock-panel refresh **S14**) has been lifted into **Phase L**
+> (Look-and-feel) on `dev`, taken up by a parallel team so Phase S feature work proceeds
+> ungated. S0-DS is now **Phase L point L1** (the shared kit); S14 is now **L2** — and,
+> per Daniel's DS-3 call, expanded from a light re-skin into a **thorough dock-panel layout
+> redesign** that lays out the full M11-aware button inventory before applying the kit; the
+> VST editor + embed-strip restyle is now the explicit **L3** point (gated on Phase S
+> landing on dev). The design-system forks DS-1 (LICE + WDL free game, no external
+> frameworks), DS-2 (Direction B "Neon Console" + Direction C's spectral keyboard strip),
+> and DS-3 (thorough panel layout redesign) are all **SETTLED (Daniel, 2026-07-26)**.
+>
+> **Authoritative from here:** **PLAN.md §Phase L + CONTEXT.md §Phase L on `dev`**, and
+> `docs/product/visual-design-language.md` (on `dev`). Phase S's **S10–S13 build their
+> interaction UX with the current drawing and adopt the Phase L kit when it lands — they
+> are not gated on Phase L.** LICE/SWELL-only, the pure-geometry-module discipline, RT
+> discipline, and the read-only-over-bank / VST3-class-UID-unchanged guardrails all hold
+> exactly as before — a visual refresh is not a data-ownership or compat event.
+
+## ReaSampler 9000 — the UX overhaul (S10–S13; DAW-tested S1–S6, "the UX is awful")
+
+**The bar is set: better than ReaSamplOMatic5000.** Daniel DAW-tested the S1–S6
+instrument and the verdict was that it *works* but the UX is unacceptable — "this is
+supposed to be better than ReaSamplOMatic5000." The S1–S6 editor was a spike-grade LICE
+panel: a clickable sample list, zone rows each carrying **seven tiny ±1 nudge/delete
+mini-buttons** (low-/low+/high-/high+/root-/root+/delete), text-only labels, **no keyboard
+visualization, no waveform, no drag interaction of any kind, no scrolling** for long lists.
+Setting a zone from C1 to C4 by clicking "+" thirty-six times is the catastrophe; the rest
+(no way to *see* a sample, no loop editing by eye, unreachable rows past the panel bottom,
+a fixed envelope) compound it. The overhaul is scoped as **S10–S13**, sequenced so the
+friction Daniel feels every test pass is removed first.
+
+### Workflow hierarchy (REVISED 2026-07-26 — Daniel; supersedes the keymap-first S10)
+
+The overhaul is reframed around the **actual workflow**, not a keymap. Daniel's directive,
+distilled: *a giant list of "item" blocks is visually useless; optimize for working with
+individual captures, not a huge list of everything.* The settled hierarchy:
+
+1. **Primary flow = one capture, fast.** Most instances play a **single capture**. The
+   metric is **time-to-first-note**: open → pick a capture → see it (waveform/peaks) → play
+   it. The default editor face serves this, not a zone table.
+2. **Fresh instance is SILENT — nothing auto-selected (policy reversal of S4).** On open
+   with no stored selection, the instrument plays **nothing** and shows a clear **empty
+   state** ("pick a capture") — it does **not** auto-play sample #1. This deliberately
+   reverses the S4 "first sample plays" convenience: the `selectSample` first-sample
+   fallback and the processor's Tier-0 fallback that resolved it are removed; an empty
+   stored id resolves to silence. (Recorded as a reversal, not a regression.)
+3. **Capture browser, not an item list.** Scannable **cards/rows** with **peak thumbnails**
+   (the `Sample` peaks bank_model already carries — the same data the dock panel thumbnails
+   draw), name, and a **root/key badge** where present; **filterable by bank** (bank_book
+   named banks). A "giant list of item blocks" is the anti-pattern — the browser is designed
+   for scanning by eye.
+4. **Graphic, descriptive controls with a guided fast path.** Once a capture is picked, a
+   prominent, self-explanatory single-capture setup surface (root note, play-mode basics,
+   level). The keyboard strip serves the **single-capture** case first (shows where the
+   capture sits / its root); drag matters most when zoning.
+5. **Zones demoted to secondary (nice-to-have).** Multi-zone keymap editing becomes an
+   **opt-in "Zones" panel** (S10-Z), not the default face — "most of the time the zones
+   won't be used." The keyboard-strip drag machinery is still built, but in service of the
+   capture-first layout.
+
+**What "better than RS5K" means, specifically (not vibes).** RS5K's genuine strengths —
+match or beat each: (1) **drag a file straight onto it** loads the sample (our S13 relay);
+(2) **note-start / note-end** range with a visual sense of the keyboard (our S10 keyboard
+strip — RS5K's own range UI is two number fields, so a *draggable* strip beats it); (3) a
+**waveform** with draggable start/end/loop markers (our S11); (4) **ADSR** sliders (our
+S12); (5) velocity layers / round-robin (Tier 2 — held, not in this overhaul). RS5K's real
+**weaknesses are our opening:** its **one-sample-per-instance** model forces track sprawl
+(one RS5K per drum) and it has **no multi-zone view in a single instance** — ReaSampler
+9000 is multi-zone in one instrument by design (S5), so the **opt-in Zones panel** showing
+*all* zones at once is a capability RS5K structurally lacks. But per the reframe, the *default*
+face is the single-capture fast path (browser + setup), and multi-zone is the demoted
+nice-to-have. "Better than RS5K" = a fast single-capture browser where RS5K makes you drag a
+file blind, direct-manipulation where RS5K uses number fields, multi-zone-when-you-want-it
+where RS5K is one-shot, and bank-integrated ingest where RS5K is file-at-a-time.
+
+**Constraints (unchanged — settled, do not re-open):** LICE/SWELL drawing only (no toolkit
+change — D-A settled); **all layout/hit-test math in pure geometry modules** (mirror of
+`mode_switch` / `editor_geometry` / `embed_strip`), the draw + drag-state machine in the
+shell; RT discipline untouched (every edit commits **off** the audio thread via the
+existing `commitMapAndReload` → off-thread `reloadFromBank` → atomic swap); the instrument
+stays a **read-only bank consumer** (loop/root/ADSR edits are the instrument's *performance
+map*, D-B — never written back to the bank); component-state persistence and
+read-only-over-bank stay settled.
+
+- **S10 — capture-first editor: browser + guided single-capture setup (REVISED 2026-07-26).**
+  The default face is the **capture browser** (scannable cards with **peak thumbnails** from
+  the `Sample` peaks bank_model carries, name, root/key badge; **bank filter** over bank_book
+  banks) feeding a **guided single-capture setup** (root note, play-mode basics, level).
+  Fresh instance is **silent, nothing auto-selected** — the S4 first-sample fallback is
+  **removed** (empty stored id → silence + a "pick a capture" empty state). New pure modules:
+  `capture_browser` (card/grid layout + hit-test) and `keyboard_strip` (key-span↔pixel via
+  the `embed_strip` idiom; a **root marker** for the single loaded capture; `pixel→note`;
+  drag-delta resolver; per-zone bar rect + edge-grab hit regions for the opt-in Zones panel).
+  Shell extends the click-only `wndProc` to a `WM_MOUSEMOVE`/`WM_LBUTTONUP` drag-state
+  machine with live feedback, one coherent edit on release. **Multi-zone keymap editing is an
+  opt-in "Zones" panel (S10-Z), not the default** — the demoted nice-to-have; it reuses the
+  same strip geometry + drag machine (edge = resize, body = move, key = root) and retires the
+  seven ±1 nudge buttons per row. **Built with the current LICE drawing; adopts the Phase L
+  kit (L1) when it lands** (drawn through the shared component kit rather than flat
+  `LICE_FillRect`/GDI once available) — **not gated on Phase L**; the drag machine's
+  `WM_MOUSEMOVE` tracking also lights the kit's hover states at near-zero marginal cost once
+  the kit is present. **Boundary shifts (from the reframe):** the "sample list" S12 was to
+  scroll/search **is now this browser** — the card layout, peak thumbnails, and bank filter
+  are S10's; S12 keeps **scroll** + **type-to-filter search** *layered over* S10's browser
+  (bank filter picks the bank, search narrows within it). The waveform S11 makes loop-editable
+  is the same waveform S10 shows read-only for the picked single capture ("see it").
+- **S11 — waveform view + draggable loop points.** Selecting a zone shows its sample's
+  **waveform** (peaks via the existing `peaks` module over the shell's already-decoded PCM
+  — no new decode/WAV path) with draggable **start/end/loop-start/loop-end** markers that
+  **snap to zero-crossings** (the S2 zero-crossing-aware requirement). A dragged loop is a
+  **per-zone loop override** (additive on `PerformanceZone`, same shape as `rootOverride`;
+  seeded from the S2 bank intrinsic, never written back). Marker/waveform geometry pure
+  (`frame↔pixel`, marker grab regions, clamp start≤end, zero-crossing snap helper).
+- **S12 — scale + ergonomics.** **Scroll** (wheel + scrollbar) over **S10's capture
+  browser** so a bank longer than the panel is fully reachable, and a **type-to-filter
+  search** that narrows the cards by name, **composing with S10's bank filter** (bank filter
+  selects the bank; search narrows within it). *(Boundary shift from the 2026-07-26 reframe:
+  the browser card layout, peak thumbnails, and bank filter are now **S10's**; S12 = scroll
+  + search layered over that browser.)* **Direct numeric entry** for zone low/high/root (a
+  click-to-type field over the strip, for precision the drag can't hit — Zones-panel-scoped).
+  An **ADSR editor** — four draggable controls over the S3 `AdsrParams` (the math already
+  exists and is wired into the voice engine; today the envelope is a fixed default).
+  Scroll/search/slider/entry layout pure; ADSR + (implicitly) any exposed parameters become
+  per-instance component state (additive, version-bumped, back-compat).
+- **S13 — drop-to-load (the S8 relay, in the editor).** Dropping an OS file / media item
+  **onto the editor window** ingests into the bank + assigns to this instance — the RS5K
+  "drop a file straight on it" affordance. **The instrument does not ingest:** the editor's
+  drop handler **relays a bank-ingest request to the extension** (S8's `option 1`), which
+  performs the capture/import + assign; refresh is hands-free via S9 (or a direct reload
+  without it). **Cross-artifact relay is the S8-flagged spike** — proven-and-shipped or
+  degrade to the docked-`bank_panel` drop path with a clear affordance. Never inserts a
+  timeline item (capture/placement separation intact).
+
+**Sequencing (recommendation, argued below in this section's tail).** S10 first — under the
+reframe it now carries the **whole felt win**: the empty-state / no-auto-select fix, the
+capture browser (peak thumbnails, bank filter) that replaces the useless item list, and the
+guided single-capture setup that retires the nudge buttons. This is the entire "the UX is
+awful" wound, and time-to-first-note is the metric it moves. S11 (waveform + loop) and S12
+(scroll/search over the browser, numeric entry, ADSR) follow — both lean on S10's browser +
+drag machine, and S11's waveform is the same surface S10 shows for the picked capture. S13
+depends on S8's ingest seam, so it sequences after S8. Against the queued engine work: **S10
+should land before or interleaved with S7 (stereo).** S7 is a real engine capability (stereo capture in true
+stereo) and touches the DSP Daniel smoke-tests — but the *reason* he'll keep smoke-testing
+is the editor, and today every test pass is taxed by the nudge-button UX. Fixing what he
+feels first (S10) makes every subsequent S7 test less painful; there is no hard dependency
+either way (S7 is engine/bus, S10 is editor/geometry — orthogonal). Honest counter: if the
+stereo *sound* is the thing blocking real use, S7 first is defensible — but "it works, the
+UX is awful" points at the editor as the live wound, so **S10 leads.**
+
+## Product name — ReaSampler 9000 (Daniel, 2026-07-26)
+
+The MIDI-playback instrument's product name is **ReaSampler 9000**. The extension stays
+**ReaSampler** (capture + organization); the instrument is **ReaSampler 9000** (playback).
+Set by Daniel on DAW-testing the S1–S6 instrument, alongside the UX-overhaul directive.
+
+- **Propagate the display name** across user-visible surfaces: the VST3 class **display
+  name** string in the factory registration, the **factory vendor/name strings**, the
+  `IPlugView` editor **title band** (currently "ReaSampler Instrument"), the **S6 embed-strip
+  label**, and the Phase S docs.
+- **Do NOT change the VST3 class UID.** Instances in already-saved projects key off the
+  class UID; changing it orphans every existing instance in every saved project. The UID is
+  a forever-stable contract (mirror of the command-id / ext-state-namespace forever-stable
+  strings).
+- **S-NAME-1 SETTLED (Daniel, 2026-07-26): rename the binary filename too.** The on-disk
+  module name is renamed to match the product (e.g. `reasampler_9000.vst3`), not just the
+  display strings. Full rename surface: **CMake `OUTPUT_NAME`** on the second VST3 target,
+  the **factory vendor/name strings**, the **editor title**, and the **embed label**. The
+  **class UID stays locked** as the compat anchor.
+- **Compat verification (must-DAW-verify before shipping the rename).** The working
+  assumption is that REAPER **rebinds a saved instance by its VST3 class UID, not by the
+  module filename** — so a filename rename with an unchanged UID keeps saved projects working.
+  **This is a to-verify assumption, not a confirmed fact:** a web check surfaced a
+  JUCE/VST3-replace-VST2 case suggesting REAPER's binding can be more nuanced than "UID only"
+  (an FXID match is involved), so it is not safe to assert UID-only rebinding from source.
+  **DAW-verify:** save a project with an instance under the old filename, rename the module,
+  reopen, and confirm the instance rebinds and restores its state. If REAPER keys partly on
+  filename, fall back to keeping the current filename (display-strings-only) and record that
+  as the shipped choice.
+
 ## REAPER / Steinberg API surface (verify all signatures)
 
 - **VST3 SDK (a new vendored dependency — vendor it at the spike).** `FUnknown` and the
@@ -1307,9 +1825,238 @@ and embed message/lifecycle against `vendor/reaper-sdk/sdk/reaper_plugin_fx_embe
 - **Embedded UI (D-D, later point).** `IReaperUIEmbedInterface` and the embed
   message/lifecycle contract — verify against
   `vendor/reaper-sdk/sdk/reaper_plugin_fx_embed.h` before use.
+- **VST3 bus arrangement (S7 channel mode).** `setBusArrangements` /
+  `getBusArrangement` and REAPER's mono/stereo instrument-bus expectations — verify against
+  the vendored Steinberg SDK + `reaper_vst3_interfaces.h`.
+- **Ingest surfaces (S8).** `InsertMedia` is the placement path (untouched by ingest);
+  `CountSelectedMediaItems` / `GetSelectedMediaItem` + `GetSet_LoopTimeRange` are the
+  arrange-capture inputs (already the capture path's); `OpenMediaExplorer` +
+  `MediaExplorerGetLastPlayedFileInfo` are the *whole* Media-Explorer contract (thin — no
+  enumerate-selected, no ME-drop-handler). Drop handling is SWELL/Win32 on ReaSampler's own
+  panel HWNDs — REAPER exposes **no** drag-drop registration API. All verified against
+  `reaper_plugin_functions.h`.
+- **Bank-generation seam (S9).** New forever-stable `ext_keys.h` key for the generation
+  counter; read over the same bridge `GetProjExtState` path S4 already uses. No new API —
+  confirm no torn-read hazard on the integer key.
+- **WDL pitch/resample (S15/S16).** **Verified this pass:** `vendor/WDL/WDL/resample.h`
+  (`WDL_Resampler` — sinc/linear resampler, couples duration → **Varispeed** path) and
+  `vendor/WDL/WDL/simple_pitchshift.h` (`WDL_SimplePitchShifter` — time-domain OLA,
+  **duration-preserving** → the S16 **Preserve**-engine candidate, fork S16-F2 route a) are
+  the whole pitch/resample surface; **no** elastique / formant-preserving in the tree. **S16
+  Preserve-engine (route a) must-verify at build:** (i) **pre-warm** `WDL_SimplePitchShifter`
+  at voice-allocation (run silence so `m_psbuf` sizes and `m_queue` reaches steady state) →
+  **no `process`-thread `WDL_Queue::Add` growth**; (ii) measure **per-voice CPU + onset
+  latency** (window·srate) against the polyphony cap; (iii) set a **Preserve-mode-specific
+  voice cap** if the per-voice cost demands one. The pitch-envelope modulation is hand-rolled
+  over whichever engine. If the held sinc **Varispeed**-quality upgrade is taken, verify
+  `WDL_Resampler` streaming/prealloc against the per-voice RT budget before use.
 - **LICE/SWELL editor.** Reuses the `bank_panel` LICE/SWELL drawing surface; verify the
   `IPlugView`↔LICE window/bitmap bridge at the spike (window creation, sizing, event
   routing) — the least-trodden edge of the phase.
+- **LICE design-kit surfaces — moved to Phase L.** The shared LICE drawing-kit surface
+  verification (`LICE_GradRect`/`LICE_RoundRect`/AA lines/circles/beziers/polygons + the
+  `LICE_CachedFont`/`LICE_IFont` font engine, and the vwnd drawing-craft references) now
+  lives with **Phase L point L1** on `dev` — see CONTEXT.md §Phase L "LICE / WDL API
+  surface". Phase S surfaces (S10–S13) adopt that kit when it lands; they are not gated on it.
+
+## Drop-and-load — drag a capture onto a track's FX button (S17 spec)
+
+**The gesture.** While a capture is dragged out of the `bank_panel`, a track's TCP **FX
+button** becomes a drop zone. Dropping the capture there **instantiates a ReaSampler 9000
+on that track with the dragged capture already loaded and selected for playback** — one
+gesture from bank to playable instrument. This is the *third* integration gesture: capture
+(extension), placement-into-arrange (extension), and now **placement-of-the-player**
+(this wave). It is drop-and-load, not drop-to-arrange — no media item touches the timeline.
+
+**Why it needs a new drag mode (the CF_HDROP path can't carry it).** Today's drag-out
+(M11) becomes an **OS file drag** (`CF_HDROP` via `drag_out` + `drag_out_win`) the moment
+the pointer leaves the panel client rect. REAPER's TCP FX button is **not** a native drop
+target that instantiates a plugin-with-a-file, so this feature cannot ride the OS-drag
+path: an OS drop of a WAV onto the FX area does not create "an instrument preloaded with
+that WAV." It requires an **internal drag** where the extension itself tracks the pointer
+over REAPER's own UI, detects the FX-button hover, and on release **drives the insert
+itself**. The extension is the actor for the whole gesture.
+
+**The two-part mechanism.**
+
+1. **Internal-drag hover detection (extension-side, pure + shell).** The `drag_out` pure
+   module gains a **third `DragGesture`** beyond `Internal` (bank-to-bank) and `OsDrag`
+   (M11) — `InstrumentDrop`. The gesture decision is refined: leaving the panel client
+   rect no longer *immediately* means OS-bound. Instead:
+   - Pointer **inside** the panel client rect → `Internal` (unchanged bank-to-bank drag).
+   - Pointer **outside the panel but still over REAPER's own window/UI** →
+     `InstrumentDrop` (new — the shell hover-tracks the TCP FX button and highlights it).
+   - Pointer **left REAPER entirely** (Explorer / another app) → `OsDrag` (unchanged M11).
+
+   The pure module stays REAPER-free: it decides `InstrumentDrop` vs. `OsDrag` from
+   position **plus an "over-REAPER's-own-UI" predicate the shell supplies** (the shell owns
+   the REAPER window/hit query; the pure layer owns the set/boundary algebra). Mirror of how
+   M11 kept `decideGesture` pure over a rect the shell supplied. The shell then resolves the
+   pointer to a track + FX-button hotspot, highlights it, and on release drives the drop.
+
+2. **FX-button drop → add-VST + load-capture (extension-side shell, then instrument
+   seam).** On release over an FX button the shell:
+   - Adds a fresh instance: `TrackFX_AddByName(track, "VST3:ReaSampler 9000", /*recFX*/
+     false, /*instantiate*/ <negative>)`. **Verified present** in
+     `reaper_plugin_functions.h`:
+     `int TrackFX_AddByName(MediaTrack* track, const char* fxname, bool recFX, int
+     instantiate)` — a **negative** `instantiate` always creates a new effect (per the
+     header comment); the `"VST3:"` prefix selects the format. Captures the returned FX
+     index (or `-1` on failure).
+   - **Loads the dragged capture into that instance via the load-capture seam** (below).
+   - Wraps the whole thing in one REAPER undo point (`Undo_BeginBlock2`/`EndBlock2`) so the
+     gesture is one Ctrl-Z — the same discipline the bank verbs use.
+
+**The ReaSampler 9000 load-capture seam (the hard coupling — MUST be added; does not yet
+exist).** The Phase S spec today gives the instrument a **live-state *read* seam** (it
+reads bank index + mapping from `"reasampler"` ext-state via the bridge — §The two seams)
+but **no entry point for an external actor to say "this fresh instance should play *this
+specific* capture."** Reading the bank is not the same as being *pointed at one sample*.
+This wave is the reason to add that seam, and the seam lands **inside the instrument**
+(the `phase-s` artifact), not the extension.
+
+**Mechanism (SETTLED — (B) VST3 component-state injection).** Right after
+`TrackFX_AddByName` returns the new FX index, the extension writes the instance's component
+state directly — the same blob the instrument's `getChunk`/`setChunk` round-trips — with
+the target capture pre-selected. Deterministic, no shared-state race, no cross-process
+handshake; it uses the instrument's own persistence format. The state-set path is
+`TrackFX_SetNamedConfigParm` — **verified present** in `reaper_plugin_functions.h`: `bool
+TrackFX_SetNamedConfigParm(MediaTrack* track, int fx, const char* parmname, const char*
+value)`, and the header documents the write-parms `vst_chunk` / `vst_chunk_program` as the
+base64-encoded VST-specific chunk. So the injection call is
+`TrackFX_SetNamedConfigParm(track, fx, "vst_chunk", <base64 blob>)`.
+
+**Load-bearing caveat — `vst_chunk` is the plugin's own serialized chunk.** `vst_chunk` is
+ReaSampler 9000's **own** base64-encoded serialized state (its `getChunk`/`setChunk`
+FXP/FXB-style blob), **not** a raw VST3 `IComponent::setState` stream that REAPER
+re-marshals into the plugin. The extension therefore has to construct **exactly the
+instrument's own state-blob bytes** with the capture pre-selected — REAPER does not
+translate a neutral state representation on its behalf. This makes the **component-state
+blob format a shared cross-artifact contract** — one that is **still being defined in Phase
+S** — and a **coordination dependency between the extension and the instrument:** both must
+agree on the exact byte layout that ReaSampler 9000's `setChunk` accepts before either half
+is final. The load-capture seam and the component-state persistence work (§Where the toggle
+lives / component-state version bumps) share this one blob format.
+
+**Rejected alternative — (A) fresh-instance ext-state handshake.** The extension writes a
+small "pending load" hint into `"reasampler"` ext-state keyed to the target track/FX (a
+capture id + a target GUID); a freshly-instantiated ReaSampler 9000 reads it on init via
+the bridge it already uses, claims + clears the hint, and self-selects that capture. It
+would keep the artifacts loosely coupled through the one ext-state seam they already share
+and avoid the extension hard-coding the instrument's state format — but it **loses on the
+claim/clear race:** "which instance claims which hint" needs a stable key and a
+cross-process handshake to get right, and (B) sidesteps that entirely by writing the state
+directly and deterministically.
+
+**Coexistence with the OS drag-out (disambiguation contract).** The two OS-vs-internal
+modes are disambiguated **by pointer location, not a mode toggle** — the user never picks
+"OS drag" vs. "instrument drop"; the extension infers it from where the pointer is when
+released. The M11 boundary (left the client rect) is *refined*, not replaced: leaving the
+rect now asks "over REAPER's UI → InstrumentDrop, else → OsDrag." Both M11 OS drag-out and
+the internal bank-to-bank drag must remain **byte-for-byte unchanged** in their own
+regions — this wave only inserts a new middle case. Multi-capture payloads are a
+disambiguation input too (see open question — instrument drop is naturally single-capture;
+a multi-capture drag over the FX button is either rejected or loads the first).
+
+**Precision / invariant implications (drop-and-load).**
+- **Explicit user-driven placement — consistent with capture↔placement separation.** This
+  is a *deliberate placement gesture*: the user chooses to put a playing instrument on a
+  track, exactly as inserting an item into the arrange is a deliberate act. It does **not**
+  auto-capture (the file already exists in the bank) and does **not** insert a media item
+  into the timeline. It instantiates a *reader* of the bank on a track and points it at one
+  already-captured sample. Capture, placement, and playback stay three distinct acts; this
+  is placement-of-the-player, not a capture and not a timeline insert.
+- **No private sample copy.** The instantiated instrument consumes the one authoritative
+  bank (it resolves the WAV via the shared M4 project-relative machinery like any
+  ReaSampler 9000 instance); the seam hands it a *reference* (a capture identity), never a
+  copied file. Any path that copies bytes into the instance is a bug.
+- **The internal drag stays pure-decidable and testable.** The new `InstrumentDrop`
+  gesture is decided in the `drag_out` pure module (REAPER-free) over a shell-supplied
+  predicate; the M11 `drag_out` unit tests must not regress.
+
+**Open questions (Daniel / Phase S team to decide).**
+- **Multi-capture drag over an FX button** — reject (only single-capture drags arm
+  `InstrumentDrop`), or load the first / a keymap of all? Tier-0 leans reject-or-first;
+  a multi-capture keymap load is a Tier-1 stretch.
+- **FX-button hotspot vs. whole TCP.** Does the drop zone have to be the FX button
+  specifically, or is dropping anywhere on the target track's TCP enough (simpler hit
+  resolution, arguably clearer target)? Depends on what the SDK exposes (see must-verify).
+
+**Must-verify before build (drop-and-load).**
+- `TrackFX_AddByName` — **verified present** (`reaper_plugin_functions.h`): signature and
+  the `"VST3:"`-prefix + negative-`instantiate` semantics confirmed from the header.
+- **Pointer→track / FX-button hit resolution during a drag** — **not yet confirmed.**
+  Candidates: `GetTrackFromPoint` / `GetThingFromPoint` (verify names + signatures against
+  `reaper_plugin_functions.h`); whether the FX button specifically is addressable vs. the
+  TCP as a whole is an open verification that also decides the "hotspot vs. whole TCP"
+  question.
+- **Instance state injection (seam mechanism (B) — SETTLED, load-bearing prerequisite)** —
+  **verified present** in `reaper_plugin_functions.h`: `bool
+  TrackFX_SetNamedConfigParm(MediaTrack* track, int fx, const char* parmname, const char*
+  value)`, with the header documenting `vst_chunk` / `vst_chunk_program` as the
+  base64-encoded VST-specific chunk write-parms. The injection call is
+  `TrackFX_SetNamedConfigParm(track, fx, "vst_chunk", <base64 blob>)`. The remaining
+  prerequisite is **not** the API but the **shared component-state blob format**: `vst_chunk`
+  carries the instrument's *own* serialized chunk (its `setChunk` input), so the extension
+  must construct exactly ReaSampler 9000's state bytes — the cross-artifact contract still
+  being defined in Phase S. Blocks the drop half until the blob format is agreed.
+
+## VST3 channel identity — the UID pair + the pairing surface (S18; extends Phase V V4)
+
+**Decided (Daniel, 2026-07-26):** the beta/stable channel split Phase V V4 gave the
+*extension* extends to the **ReaSampler 9000 VST3 instrument** — a beta-built VST pairs with
+the beta extension only, a stable VST with stable only, both installable side-by-side in one
+REAPER. This is the instrument-side companion to V4 and mirrors its philosophy exactly:
+**one channel per binary; all channel identity derives from the ONE
+`REASAMPLER_CHANNEL_IS_BETA` bit via the pure `app_version` module — no scattered `#ifdef`s
+in the VST shell.**
+
+**What is already isolated (structural, not added by S18).** The wire/data pairing is
+already done and needs no per-key work: `ext_keys.h`'s `kProjExtNamespace()` delegates to
+`app_version::extStateNamespace()`, so a beta-compiled VST's bridge reads `"reasampler_beta"`.
+Every wire key — `banks`, `assign_request`, S9's bank-generation key (in-flight), S17's
+component-state contract, and **any future key** — is a plain constant *under* that
+namespace, so channel data-isolation is **structural: no per-key opt-in, and a future key
+that forgets to isolate is impossible by construction** (it keys off the namespace accessor,
+not a raw literal). What S18 adds is only the missing *plugin identity* layer.
+
+- **The UID-pair invariant (the permanent commitment).** The VST3 class UID is the plugin's
+  identity — a saved REAPER project records it and rebinds a saved instance by it. Today
+  `reasampler_vst.h` holds **one** forever-locked UID (`kReaSamplerProcessorUID`,
+  `REASAMPLER_PROC_UID_1..4`, S-NAME-1). A beta VST with the **same** UID cannot coexist with
+  stable in one install (same UID = identity collision / arbitrary rebind). So beta needs its
+  **own** forever-stable UID: a second constant, minted once, locked exactly as the first.
+  **Invariant: BOTH UIDs are frozen forever once shipped; the channel bit selects which is
+  compiled into this binary** (one `DEF_CLASS2`, one class per binary — not both classes in
+  one binary; that mirrors V4's fully-isolated-binary philosophy and keeps a beta build from
+  ever presenting the stable identity). Saved-project isolation follows directly: a project
+  saved with beta instances rebinds only to the beta VST; a stable-saved instance opened
+  where only the beta extension has banks resolves the stable UID and shows a clean empty
+  "pick a capture" state (S10 policy), not an error.
+- **Binary + display identity, channel-derived.** Mirror the extension's `OUTPUT_NAME` fork
+  (`reaper_reasampler` / `reaper_reasampler_beta`): the VST3 module's on-disk name forks
+  `reasampler_9000` / `reasampler_9000_beta`, its factory display name "ReaSampler 9000" /
+  "ReaSampler 9000 beta", and its editor title band + S6 embed-strip label are channel-aware
+  — **all sourced from `app_version` channel accessors (a VST-name accessor beside
+  `binaryName()`/`dockTitle()`), never a literal in `reasampler_vst.h`/`vst_entry.cpp`.** The
+  factory version string carries the `-beta` render where V4's `appVersion()` already does;
+  vendor/url/email stay shared unless V4 qualified the equivalent (V4 kept the lane-name
+  prefix shared — shared-where-V4-shares is the default).
+- **The complete pairing surface (the guarantee to state, not new code).** A channel's VST
+  talks to that channel's extension **only**, because (1) plugin identity — UID + filename +
+  display — is channel-forked (above), and (2) **all** wire keys live under the
+  channel-derived `kProjExtNamespace()`. The two together make pairing complete and
+  structural: identity keeps the *plugins* distinct; the namespace keeps the *data* distinct.
+  No per-key or per-seam isolation work is ever needed — S8's assignment key, S9's generation
+  key, and S17's blob-injection key all inherit it. **Verify all identity/factory wiring
+  against the vendored Steinberg SDK** (`DEF_CLASS2` / `INLINE_UID` / `FUID` from
+  `pluginfactory.h` + `funknown.h`); the pure `app_version` name accessors are CTest-tested.
+- **Fork S18-F1 (flagged — Daniel's call): mint the beta UID now vs. at first beta release.**
+  Lean **mint now** — mirrors the stable UID (minted at the S1 spike, locked long before
+  ship), removes a "remember to mint before shipping beta" landmine, zero cost for an
+  unused-until-beta constant. The alternative (a locked-once placeholder replaced before the
+  first beta VST ships) defers the commitment but adds a release-gate step. Flagged only
+  because the UID is a forever commitment.
 
 ## Non-goals / guardrails
 
@@ -1319,6 +2066,13 @@ and embed message/lifecycle against `vendor/reaper-sdk/sdk/reaper_plugin_fx_embe
 - **The instrument keeps no private copy of the samples.** It consumes the one
   authoritative bank; per-instance sample stores are a non-goal (they refork the source
   the one-source-multiple-views instinct keeps single).
+- **The instrument never ingests (S8).** Capture, import, and drop-ingest are *extension*
+  acts; the instrument only reads and plays. A drop onto the editor window (if the spike
+  proves it viable) is *relayed to the extension* as an ingest request — the instrument
+  never writes the bank itself.
+- **Channel mode is a performance choice, not a bank fact (S7).** The mono/stereo toggle is
+  per-instance component state, never written to `Sample` or the bank (D-B). The bank's
+  per-sample channel-count intrinsic is a *file fact*; the play mode is the instrument's.
 - **No cross-platform / multi-format.** Windows-only, VST3-only, REAPER-only (D5). Do
   not add an AU/AAX/VST2/CLAP wrapper, a mac/Linux build, or a standalone host target.
 - **The pure core stays REAPER-free *and* VST3-free.** The voice engine / envelope /
@@ -1329,7 +2083,44 @@ and embed message/lifecycle against `vendor/reaper-sdk/sdk/reaper_plugin_fx_embe
   else in Phase S lives in the *second* artifact and does not alter the extension's
   M/D/B/R/V pillars.
 - **Do not spec Tier 2/3.** Tier 2 is held (noted, not specified); Tier 3 is
-  optional-forever. Do not let their feature lists drive Tier 0–1's build shape.
+  optional-forever. Do not let their feature lists drive Tier 0–1's build shape. **Note:**
+  S7 stereo is *not* a Tier-2 feature — it is a channel-count dimension on the existing
+  Tier 0–1 engine, orthogonal to Tier 2's velocity-layers / round-robin / per-sample trim.
+  (S7's stereo loop read is the same loop the core already has, extended per-channel — not
+  the Tier-2 "sustain loops" feature.) **Likewise S15/S16** (Trigger/Gate modes + pitch
+  envelope) are Daniel-directed engine features on the Tier 0–1 core, *not* Tier 2/3 — the
+  AHDSR hold, Trigger one-shot, start point, and AD pitch envelope are orthogonal amplitude-
+  shape / read-rate dimensions, not the held velocity-layers / round-robin / filter work.
+- **S15/S16 params are performance choices, not bank facts.** Play mode, start point,
+  %-length, fades, AHDSR, and the pitch envelope are per-instance performance-map state
+  (component state), never written to `Sample` or the bank (D-B). The bank carries file
+  facts (root note, loop intrinsic, channel count); the instrument owns how they are played.
+- **S15/S16 stay channel-count-agnostic (S7 interplay).** The mode/envelope logic is
+  per-frame amplitude and read-rate, independent of the S7 channel dimension. Any S15/S16
+  code that assumes a fixed channel count (mono) — rather than operating per-frame pre-mix —
+  is a bug that would collide with S7. Spec and build them channel-agnostic.
+- **Trigger ignores note-off; choke is out of scope (S15).** In Trigger mode note-off is a
+  no-op and the one-shot plays to `playEnd`. Choke-on-note-off / choke-groups are held
+  (fork S15-F1, Tier-3-adjacent) — do not add a choke path in S15.
+- **Pitch envelope is off by default (S16).** Default-disabled → offset always 0 → the
+  engine's un-modulated output → playback bit-identical to the same engine pre-envelope. A
+  regression that applies pitch modulation when the envelope is off is a bug.
+- **Pitch engine is a per-zone performance choice, not a bank fact (S16).** Varispeed vs
+  Preserve is per-`PerformanceZone` component state (D-B), never written to `Sample` or the
+  bank. The engine default is fork S16-F1 (**lean Preserve** — Daniel's call), with a
+  prominent per-zone toggle so drum/one-shot zones opt into Varispeed cheaply.
+- **Preserve engine is RT-disciplined (S16).** The `WDL_SimplePitchShifter` (or hand-rolled)
+  Preserve path **pre-warms at voice-allocation** and does **no allocation in `process`** — a
+  `WDL_Queue::Add` or `Resize` on the audio thread in steady state is a bug. Preserve's onset
+  latency (shifter window) is an accepted property, **not** a defect; a note-onset **click or
+  smear** from a cold-started (un-pre-warmed) shifter **is** a bug.
+- **`WDL_Resampler` is not a Preserve engine (S16).** It is a resampler (couples duration) —
+  a held Varispeed-quality option only. Do not wire it as the duration-preserving path.
+- **Drop-and-load must not regress the two existing drags.** S17 inserts a new middle case
+  (`InstrumentDrop`) between the M11 OS drag-out and the internal bank-to-bank drag; both
+  existing gestures stay byte-for-byte unchanged in their own regions. Drop-and-load never
+  inserts a media item into the arrange and never copies sample bytes into the instance —
+  it hands the new instance a *reference* to an already-captured bank sample.
 - **Verify Steinberg SDK, bridge, embed, and LICE-view surfaces** against the vendored
   headers before use — several §1a claims are experienced estimates until the spike
   confirms them.

docs/product/midi-playback.md

@@ -7,7 +7,28 @@ the **product framing behind a scoped phase**. Its build roadmap lives in **PLAN
 *why* (the plugin-format reasoning, the bare-VST3-vs-JUCE assessment, the settled
 decision record).
 
-Status: framed by product-designer (2026-07-26), **revised 2026-07-26 (r4)**. The
+Status: framed by product-designer (2026-07-26), **revised 2026-07-26 (r8)**. r8 records
+Daniel's **duration-preserving correction** (2026-07-26, verbatim: *"isn't that ratio stuff
+going to change the playback rate? I want duration-preserving repitching"*): the ratio path is
+**varispeed** (pitch/duration coupled), so S16 is reshaped from "pitch envelope only" into a
+**pitch-engine mode — Varispeed vs Preserve — plus the pitch envelope** riding either engine.
+The WDL verdict flips: `WDL_SimplePitchShifter` (duration-preserving OLA), previously dismissed
+as the wrong tool, is **now the Preserve-engine candidate** and got a real per-voice RT
+viability assessment. Two S16 forks flagged: **S16-F1** (engine default — lean Preserve) and
+**S16-F2** (Preserve implementation — WDL shifter first, hand-rolled pure module held). See the
+r8 Addendum in §4. r7 records the
+**sampling-modes engine directive** (Daniel, 2026-07-26): Trigger vs Gate play modes (Gate =
+AHDSR, Trigger = one-shot with %-length + fades), a modifiable start point in both, and an
+off-by-default AD pitch envelope — specced as **new Phase S points S15/S16**, with the WDL
+pitch surface swept and reported. See the "sampling modes" Addendum in §4. r6 records the
+**workflow-first reframe of S10** (Daniel, 2026-07-26): the editor's default face becomes a
+**capture browser + guided single-capture setup**, a fresh instance is **silent with a "pick
+a capture" empty state** (reversing the S4 first-sample auto-play), and multi-zone editing is
+demoted to an opt-in Zones panel — see the r6 Addendum in §4. r6 also settles **S-NAME-1**
+(rename the binary filename too, UID locked). r5 records the post-DAW-test directives on the
+S1–S6 instrument: the product name **ReaSampler 9000** and the **"better than RS5K" UX
+overhaul** (Phase S points S10–S13) — see the r5 Addendum in §4. r4 (below) settled the four
+residual forks D-A..D-D. The
 "no PLAN.md footprint" era is **over** — with D-A through D-D settled (below), the
 instrument was scoped into **Phase S** (codename Daniel's: "S" for Sampler, because "D"
 collides with the existing Design View phase). **PLAN.md §Phase S is now the
@@ -609,6 +630,339 @@ in-phase later point on the Phase S roadmap (**S6**), sequenced *after* the main
 `IPlugView` editor exists (it composes with that LICE path), not a someday-note. It is
 polish rather than a Tier-0 need, so it sequences last — but it is on the roadmap.
 
+### Addendum — two directions set post-scoping (Daniel, 2026-07-26)
+
+After Phase S was scoped (D-A..D-D), Daniel set two further directions. These are
+**settled directions**, not open forks — specced as new Phase S points (S7–S9), not
+re-litigated. Recorded here per the doc's settled-decisions convention.
+
+**D-E — Channel mode: mono | stereo, per-instance, bus-negotiated (→ PLAN.md S7).**
+Captures are often stereo; the current mono downmix is a Tier-0 simplification. The
+engine gets a **per-instance channel-mode toggle (1 mono / 2 stereo)** that "works with
+the REAPER audio bus automatically" — the VST3 declares/negotiates its output bus
+arrangement (`setBusArrangements`) so mono/stereo just works in REAPER's routing. Honest
+scope: **this is an S3-core extension, not a shell hack** — the core is mono-per-sample by
+design today, so stereo mode grows a channel dimension (2-channel sample data, per-voice
+stereo render, per-channel loop/interp). Mono mode keeps the existing downmix path.
+Cross-mode policy: mono-source-in-stereo → dual-mono; stereo-source-in-mono → downmix
+(existing). The toggle is instrument-owned per-instance state (D-B: a performance choice,
+never a bank fact). Sequenced **first after the editor/embed work** because it touches the
+engine Daniel smoke-tests.
+
+**Ingest routes through the bank — "option 1"; the extension owns ingest (→ PLAN.md
+S8 + S9).** Loading a sample into the sampler is **one gesture**: capture/import-into-bank
++ auto-assign to the active instance. The **extension owns ingest** (it has arrange
+access, Media-Explorer access, and the drop-target surface on its own panels); the
+**instrument stays a read-only bank consumer** — it never captures or imports. Sub-parts,
+with the honest SDK reality verified against the vendored headers:
+
+- *(a) Arrange capture → bank → assign* — a one-click action reusing the existing capture
+  path; **never inserts a timeline item** (capture/placement separation intact).
+- *(b) Media Explorer import → bank → assign* — the ME surface is **thin**
+  (`OpenMediaExplorer` + `MediaExplorerGetLastPlayedFileInfo` are the whole contract; no
+  enumerate-selected, no ME-drop-handler), so ME import is **single-file, pull-on-action**,
+  not a push/drop from inside the ME. Spike: does the last-played-file read work for a
+  merely-*selected* file?
+- *(c) Drag-and-drop* — REAPER exposes **no** drag-drop registration API; drop handling is
+  SWELL/Win32 on ReaSampler's *own* panel HWNDs. Drop *onto the VST3 editor window* relayed
+  to the extension as a bank-ingest request is a genuine **cross-artifact spike**, not a
+  promise (drop-onto-panel is the shipped path if it proves gnarly).
+- *(d) Recapture / ingest auto-refresh (→ S9)* — because instances reference sample **ids**,
+  a recapture landing under the same id (M10) or an ingest touching the active bank should
+  refresh live instances **hands-free**. The missing trigger is a **bank-generation counter**
+  in `"reasampler"` ext-state: the extension bumps it on any bank-content mutation; the
+  instrument polls it **off the audio thread** on a safe cadence and calls its existing
+  `reloadFromBank()` on change (reusing S4's atomic handoff). This seam serves both S8 ingest
+  and M10 recapture.
+
+*The genuine spikes flagged (not decisions Daniel owes, just build-time unknowns):* the
+ME merely-selected-file read (b), and the drop-onto-editor cross-artifact relay (c). Both
+are honestly-flagged as spikes in PLAN.md S8, not promised.
+
+### Addendum — product name + UX overhaul (Daniel, 2026-07-26, post-S1–S6 DAW test)
+
+Daniel DAW-tested the S1–S6 instrument and set two directives. These are **settled
+directions**, specced as new Phase S points (S10–S13) and a product-name convention — not
+open forks (the two flagged forks below are the only calls left to Daniel).
+
+**The instrument's product name is `ReaSampler 9000`.** The extension stays **ReaSampler**
+(capture + organization); the instrument is **ReaSampler 9000** (playback). Propagation is
+a checklist item (PLAN.md §Phase S — product name; CONTEXT.md §Product name): the VST3
+class **display name** string, the `IPlugView` editor title band (today "ReaSampler
+Instrument"), the S6 embed-strip label, and the docs. **Compat guard (load-bearing):** the
+**VST3 class UID must NOT change** — instances in saved projects key off it; a UID change
+orphans every existing instance. The name change is **display-string-only** on the code
+side. *Fork S-NAME-1 (Daniel's call):* the on-disk **binary filename** — renaming it
+(`reasampler_9000.vst3`) carries compat weight (REAPER keys a saved project's plugin
+reference partly by filename), so the r5 lean was **keep the filename, change only display
+strings**; flagged, not decided. *(Now SETTLED in r6, below: rename the filename too, UID
+locked, compat is a DAW-verify — the r5 lean is superseded.)*
+
+**The UX bar is "better than ReaSamplOMatic5000."** Verdict verbatim: "okay it works, but
+the UX is awful." The S1–S6 editor was spike-grade — a clickable list, zone rows with
+**seven ±1 nudge/delete mini-buttons** each, text labels, **no keyboard, no waveform, no
+drag, no scroll.** Setting a zone range by ±1 clicks is the catastrophe. The overhaul
+(S10–S13) makes "better than RS5K" *specific*:
+
+- **RS5K's strengths, matched or beaten.** Drag-a-file-onto-it load (→ S13 relay);
+  note-range + a visual keyboard (→ S10 — RS5K uses two *number fields*, so a **draggable
+  keyboard strip** beats it); waveform with draggable start/end/loop markers (→ S11); ADSR
+  sliders (→ S12). Velocity layers / round-robin stay Tier 2 (held).
+- **RS5K's weaknesses, our opening.** RS5K is **one-sample-per-instance** (forcing track
+  sprawl — one instance per drum) with **no multi-zone view in a single instance**.
+  ReaSampler 9000 is **multi-zone in one instrument** (S5), so the keyboard-strip editor
+  showing *every* zone at once is a capability RS5K structurally lacks. That is the
+  sharpest "better than RS5K" claim, and it's free — it falls out of the existing model.
+
+The overhaul honors every settled constraint: **LICE/SWELL only** (D-A), **pure geometry
+modules** for all layout/hit-test (mirror of `mode_switch`/`editor_geometry`/`embed_strip`),
+**RT discipline untouched** (edits commit off-thread), the instrument stays a **read-only
+bank consumer** (loop/root/ADSR edits are the instrument's performance map, D-B — never
+written to the bank). Component-state persistence and read-only-over-bank stay settled.
+
+*Sequencing (product recommendation).* **S10 leads** — the nudge-button zone editor is the
+friction Daniel hits on every test pass, so removing it buys the most felt improvement per
+unit of work and de-risks the drag-state machine S11/S12 reuse. Against the queued **S7
+(stereo)**: S10 should land **before or interleaved with** S7 — S7 is real engine work but
+the *reason* Daniel keeps smoke-testing is the editor, and every test pass is currently
+taxed by the UX; the two are orthogonal (S7 = engine/bus, S10 = editor/geometry), so there
+is no hard ordering, but the live wound is the editor. Honest counter: if the stereo
+*sound* is what blocks real use, S7-first is defensible — but "it works, the UX is awful"
+names the editor as the wound.
+
+### Addendum — S10 workflow-first reframe + S-NAME-1 settled (Daniel, 2026-07-26, r6)
+
+After the r5 UX-overhaul directive was specced (keymap-first S10), Daniel reframed the
+workflow before S10 was implemented. This **revises S10** and settles S-NAME-1. Settled
+directions, not open forks — recorded here per the doc's settled-decisions convention; PLAN.md
+§S10 and CONTEXT.md §Phase S (workflow hierarchy) carry the spec.
+
+**The reframe, verbatim (Daniel, 2026-07-26):** *"We need to think hard about the workflow
+with this plugin. Have a giant list of 'item' blocks is visually useless. When the plugin is
+loaded, we should not have any samples selected. We also need to show the peaks for each
+capture. Filters for a specific bank would be useful. We need to be graphic and descriptive
+with the controls, and guide the user QUICKLY towards setting up a sampler. Most of the time
+the zones won't be used, but it's a nice-to-have. So we should optimize the UX for working
+with individual captures, not a huge list of everything."*
+
+**What changed in S10 (the hierarchy is Daniel's; details are product judgment):**
+
+1. **Primary flow = one capture, fast.** The metric is **time-to-first-note**: open → pick a
+   capture → see it → play it. The default face serves the single capture, not a keymap.
+2. **Fresh instance is SILENT — nothing auto-selected (policy reversal of S4).** The S4
+   "first sample plays" convenience is **removed**: open with no stored selection → the
+   instrument plays nothing and shows a **"pick a capture" empty state**, not auto-play of
+   sample #1. Concretely retires the `selectSample` first-sample fallback (`sample_map.cpp`)
+   and the processor's Tier-0 fallback that resolved it (an empty stored id → silence). This
+   is a deliberate reversal of the S4 default, recorded as such — not a regression.
+3. **Capture browser, not an item list.** Scannable cards with **peak thumbnails** (the
+   `Sample` peaks bank_model already carries — the same data the dock panel thumbnails draw),
+   name, root/key badge, and a **bank filter** (bank_book named banks). "A giant list of item
+   blocks" is the named anti-pattern; the browser is designed for scanning by eye. `SampleChoice`
+   grows to carry the peaks + badge + bank (today it is only `{id, displayName}`).
+4. **Graphic, descriptive controls with a guided fast path.** Once a capture is picked, a
+   prominent single-capture setup surface (root note, play-mode basics, level); the keyboard
+   strip serves the single-capture case first (shows the capture's root).
+5. **Zones demoted to an opt-in "Zones" panel (S10-Z), not the default face.** "Most of the
+   time the zones won't be used." The keyboard-strip drag machinery is still built (it serves
+   both the single-capture root-set and the opt-in zoning), but multi-zone editing is behind a
+   toggle. Some S12 list ergonomics **pulled into S10**: the browser card layout, peak
+   thumbnails, and bank filter are S10's; S12 keeps **scroll** + **type-to-filter search**
+   layered over the S10 browser. S11's waveform is the same surface S10 shows for the picked
+   capture ("see it"). No renumber — S11/S12/S13 keep their numbers and their boundaries were
+   annotated, not moved wholesale.
+
+**S-NAME-1 → SETTLED: rename the binary filename too.** The r5 lean (keep the filename,
+display-strings-only) is superseded. The on-disk module is renamed to match the product (e.g.
+`reasampler_9000.vst3`) — full surface: **CMake `OUTPUT_NAME`**, factory vendor/name strings,
+editor title, embed label. The **VST3 class UID stays locked** as the compat anchor.
+**Compat is a DAW-verify, not an asserted fact:** the working assumption is REAPER rebinds a
+saved instance by class UID (not filename), so a rename with an unchanged UID keeps saved
+projects working — but a web check surfaced a JUCE/VST3-replace-VST2 case suggesting REAPER's
+binding can be more nuanced than "UID only" (an FXID match is involved), so UID-only rebinding
+is **not** safe to assert from source. Verify by save-rename-reopen in the DAW; if REAPER keys
+partly on filename, fall back to keeping the filename and record that as shipped.
+
+### Addendum — sampling modes (Trigger/Gate) + pitch envelope (Daniel, 2026-07-26)
+
+> **Superseded in part by the r8 Addendum below (2026-07-26).** Daniel's duration-preserving
+> correction reshaped S16 from "pitch envelope only" into a Varispeed/Preserve pitch-engine
+> mode, and **flipped this addendum's WDL verdict** — `WDL_SimplePitchShifter` (called the
+> "wrong tool" in item 3 below) is now the Preserve-engine candidate. Read this as the r7
+> point-in-time record; the r8 Addendum carries the current S16 shape.
+
+Daniel directed a set of engine features for the sampler, specced as **new Phase S points
+S15 (Trigger vs Gate) and S16 (pitch envelope)**. **The feature set is settled** — recorded
+here per the doc's settled-decisions convention; PLAN.md §S15/S16 and CONTEXT.md §Sampling
+modes carry the spec. Two forks are flagged with leans (S15-F1 choke, S15-F2 param
+granularity); the WDL question was resolved by inspection.
+
+**Directive, verbatim (Daniel, 2026-07-26):** *"let's have product spec out some features
+for the sampler: Sampling mode: Trigger vs Gate. Gate has an AHDSR envelope. Trigger has
+fade in, % length, and fade out. Both modes have modifiable start point, Gate has modifiable
+loop points too. In addition to amp env, there will be a pitch envelope/curve (AD?) which is
+off by default. Explore using WDL pitch capabilities."*
+
+**What was specced (the shape is product judgment; the feature set is Daniel's):**
+
+1. **Play mode — Gate vs Trigger (S15), per-sample/per-zone, instrument-owned (D-B).**
+   - **Gate** = classic held note: the current ADSR grows a **Hold** stage → **AHDSR**
+     (hold=0 is exactly today's ADSR, back-compat); note-off → release; **sustain loop
+     applies** (S11's loop markers become Gate-mode UI).
+   - **Trigger** = one-shot drum-pad: note-on fires a **% of sample length** with a
+     **fade-in** and **fade-out**, **ignores note-off**, **no loop**. Fade default
+     **equal-power** (click-free); note-off is a no-op (choke held, fork S15-F1).
+   - **Both:** a **modifiable start point** (non-zero initial read position).
+   - **Confirmed from `sampler_core.cpp`:** the read loop already advances by an arbitrary
+     per-frame ratio with linear interp and applies a per-frame amp tick, so both envelopes
+     are per-frame amplitude functions and the start point is a non-zero initial `readPos_`
+     — no resampler or voice-lifecycle rewrite.
+2. **Pitch envelope — AD, off by default (S16).** A per-voice AD curve biasing the read
+   increment (the classic pitch drop). **RT clean, confirmed:** the resampler is already an
+   arbitrary per-frame `readPos_ += ratio_`, so the envelope is a per-frame multiply of
+   `ratio_` by `2^(semitones/12)` — **hand-rolled, no new resampler, no WDL dependency**.
+   Off by default → bit-identical to pre-S16.
+3. **WDL pitch capabilities — verified, not lore (full surface swept).** The whole vendored
+   WDL pitch/resample surface is two headers: **`resample.h`** (`WDL_Resampler`, a real
+   sinc/linear RT-suitable resampler — its sinc mode *beats* the core's 2-point linear interp
+   for base-repitch quality at a CPU cost; **held as an optional quality upgrade**, not
+   needed for S15/S16) and **`simple_pitchshift.h`** (`WDL_SimplePitchShifter`, a time-domain
+   OLA *duration-preserving* pitch shifter — wrong tool for a sampler; `set_formant_shift` is
+   an **empty stub**). **No elastique / formant-preserving / time-stretch exists in WDL** —
+   REAPER's elastique is licensed (zplane), not in the vendored tree. **Recommendation:** S16
+   modulation stays hand-rolled; `WDL_Resampler` (sinc) is the only WDL piece worth adopting
+   and only as a held base-repitch quality upgrade.
+4. **Sequencing.** S15 before S16 (S16 reuses S15's param plumbing). Both are S3-core
+   extensions but **channel-count-agnostic by construction** (per-frame amplitude + read-rate,
+   pre-mix), so they **compose with S7 stereo** rather than conflicting. Core halves land in
+   CTest independently of the editor; the mode toggle / Trigger handles / AD control surface
+   through the S10/S11 waveform + setup work.
+
+**Forks flagged (leans given):** *S15-F1 (choke on note-off)* — **held**, out of S15 scope
+(Trigger ignores note-off; choke-groups are Tier-3-adjacent). *S15-F2 (param granularity)* —
+**lean per-zone only** (the single capture is already a one-zone map), flagged because it
+touches S10's single-capture setup surface.
+
+### Addendum — duration-preserving correction: S16 becomes pitch-engine modes (Daniel, 2026-07-26, r8)
+
+**Correction, verbatim (Daniel, 2026-07-26):** *"isn't that ratio stuff going to change the
+playback rate? I want duration-preserving repitching."* Daniel is right about the mechanics.
+The r7 S16 spec modulated pitch by biasing the per-frame read ratio (`readPos_ += ratio_`) —
+that is **varispeed**: pitch and duration are coupled (an octave up halves the note's
+duration). Daniel wants **duration-preserving** repitch (a transposed note keeps its length).
+This reshapes S16 and **flips the r7 WDL verdict** on `WDL_SimplePitchShifter`.
+
+**What changed (the reframe, then the spec):**
+
+1. **The reframe — this is a mode, not a replacement.** Both behaviors are musically
+   legitimate, so the answer is not "swap varispeed for preserve" but **a per-zone/per-capture
+   pitch-engine mode**:
+   - **Varispeed** (current path, cheap, zero-latency) — pitch/duration coupled. The
+     **classic sampler / RS5K** default; right for **drums / one-shots** (pitch-down-lengthens-
+     the-hit is a feature there).
+   - **Preserve** (duration-preserving) — a pitch shifter transposes the output while the read
+     holds the source duration. Right for **tempo-locked loops and phrases** (a transposed loop
+     still lines up to the bar) — which is what captured banks skew toward (project slices).
+   The pitch envelope (r7's S16 body) then rides **either** engine: under Varispeed it biases
+   the read ratio (as specced); under Preserve it biases the shifter's shift amount. So the
+   envelope is preserved, re-homed onto the engine seam.
+
+2. **Fork S16-F1 (Daniel's call): the default engine. Lean Preserve.** Argued honestly:
+   Preserve because Daniel asked for it **unprompted** (reads as his expectation) and the
+   capture workflow is **loop/phrase-heavy**; but Varispeed is the **classic-sampler
+   expectation**, is **cheaper + zero-latency**, is **bit-identical to today's shipped feel**,
+   and is what percussive one-shots want. Recommendation: **default Preserve, prominent cheap
+   per-zone toggle to Varispeed.** Daniel's call.
+
+3. **WDL verdict corrected — `WDL_SimplePitchShifter` is now the right category.** Under
+   "duration-preserving is the requirement," r7's dismissal ("wrong tool, duration-preserving
+   OLA") inverts: **duration-preserving is exactly what we need.** A real per-voice RT
+   viability assessment (from `vendor/WDL/WDL/simple_pitchshift.h`):
+   - **API:** push/pull block (`GetBuffer`/`BufferDone`/`GetSamples`); `set_shift(2^(semi/12))`
+     for pitch with an **independent** `set_tempo(1.0)` duration knob — pitch and duration
+     separately controllable, exactly Preserve.
+   - **Per-voice:** modest memory (OLA ring ≈ window·srate ≈ a few KB/voice at the 50 ms
+     quality-0 window). CPU cheap (O(length), a few mults + one OLA crossfade/frame, **no
+     FFT**) → **N polyphonic voices each running one is feasible** in RT discipline.
+   - **Costs owned:** (i) **onset latency** ~half-window (~25 ms @ 50 ms) — the load-bearing
+     cost; pre-warm at voice-allocation, and it lands on sustained/loop material (Varispeed
+     serves tight one-shots); (ii) **queue-growth** allocation in `BufferDone` — settled by a
+     silence pre-warm so no `process`-thread allocation in steady state; (iii) **basic
+     quality** (SimpleWindowed warble on big transpositions; `set_formant_shift` is an empty
+     stub → no formant preservation) — acceptable for loops, replaceable by route (b).
+   - **Fork S16-F2:** **route (a)** `WDL_SimplePitchShifter` (low-cost proof) vs **route (b)** a
+     hand-rolled pure `pitch_shift` OLA/granular module (house pattern, CTest-testable, full
+     control). **Lean (a) first, (b) held** as the quality/latency upgrade — same
+     `PitchEngine::Preserve` contract behind the seam.
+
+4. **Not proposed / restated ceilings.** `WDL_Resampler` is a *resampler* (couples duration) —
+   a held **Varispeed-quality** upgrade, **not** a Preserve engine. **elastique is NOT
+   available** (licensed zplane, not vendored). JUCE / rubberband / signalsmith are each a
+   **new-dependency fork carrying full D-A weight** (bare-VST3-no-framework is the locked D-A
+   choice) — **not proposed**.
+
+5. **S15 interaction (cleaner under Preserve).** Trigger's **%-length** becomes **pitch-
+   independent** under Preserve (wall-clock stable under transpose — cleaner than Varispeed,
+   where transposing a Trigger also scales its length); Gate's **sustain loop** contract under
+   Preserve is *loop the source read, shift the output* (loop points stay source-frame facts);
+   the **start point** is engine-independent (a source-frame offset). Channel-agnostic for S7
+   (the shifter is `set_nch`-aware; one instance per voice carries all channels).
+
+6. **RT/CPU honesty.** Preserve is **meaningfully heavier** than varispeed — a per-voice DSP
+   object with its own budget, pre-warm, and a possible **Preserve-mode-specific voice cap**
+   (below the Varispeed cap) if per-voice cost demands it. Put in Verify: pre-warm → no
+   `process` allocation; measure per-voice CPU + onset latency against the polyphony cap. Treat
+   S16's Preserve-engine point as the phase's next real DSP spike, not a thin envelope add-on.
+
+**Where the spec lives:** PLAN.md §S16 (reshaped to "pitch engine modes + pitch envelope",
+with forks S16-F1/F2 and the corrected WDL finding) and the S15 × S16 interaction note;
+CONTEXT.md §Pitch engine modes — Varispeed vs Preserve + the corrected WDL surface finding.
+
+### Addendum — VST channel isolation (Daniel, 2026-07-26)
+
+**Daniel's directive (2026-07-26, settled):** *"support the beta/stable channels for the VST
+as well. The VST in beta should talk to the beta extension only."* This extends Phase V's V4
+beta/stable split — which fully isolated the **extension** per channel — to the **ReaSampler
+9000 VST3 instrument**. Spec'd as **S18**, an immediate Phase S wave, dispatchable in parallel
+with or right after the in-flight waves (S9 ext_keys, S15/S16 processor/editor) — it touches
+`vst_entry.cpp` / `reasampler_vst.h` / the CMake VST3 block, mostly disjoint from those.
+
+**Established honestly from the tree — what already works vs. what's missing:**
+- **Already isolated (the V4↔S4 reconcile did this): data pairing.** A beta-built VST already
+  *reads* the beta namespace — `ext_keys.h`'s `kProjExtNamespace()` delegates to
+  `app_version::extStateNamespace()`, and every wire key (`banks`, `assign_request`, S9's
+  generation key, S17's blob key, any future key) is a plain constant *under* that namespace.
+  Channel data-isolation is therefore **structural, not per-key** — new keys inherit it for
+  free. No S18 work here.
+- **Missing: the VST's *plugin identity*.** Its class UID, binary filename, and display
+  strings are single-valued (same for both channels), so two installed channels would collide
+  on UID and filename. S18 closes exactly this.
+
+**The shape of S18 (mirrors V4's philosophy — one channel per binary, one bit drives it):**
+1. **A UID pair.** The stable class UID is locked forever (S-NAME-1). Beta needs its own
+   forever-stable UID (a second constant, minted once, locked identically). Both frozen
+   forever; the channel bit selects which is compiled in. **One class per binary, not both**
+   — the V4 fully-isolated-binary philosophy, so a beta build never presents the stable
+   identity. Saved-project isolation follows: a beta-saved instance rebinds only to the beta
+   VST. *Fork S18-F1 (Daniel's call):* mint the beta UID **now** (lean — mirrors the stable
+   UID minted at the S1 spike, removes a pre-ship landmine, zero cost unused) vs. defer to
+   first beta release behind a locked-once placeholder.
+2. **Channel-derived binary + display identity.** `reasampler_9000` / `reasampler_9000_beta`
+   filename (mirror the extension's `OUTPUT_NAME` fork); "ReaSampler 9000" / "ReaSampler 9000
+   beta" display; editor title + embed label channel-aware — all from the ONE bit via
+   `app_version` accessors, no scattered `#ifdef`s (the V4 invariant).
+3. **The pairing guarantee, stated as an invariant.** A channel's VST talks to that channel's
+   extension only, because identity keeps the plugins distinct and the channel-derived
+   namespace keeps the data distinct. **Structural, not per-key** — S8/S9/S17's cross-artifact
+   keys all inherit it; a future key that forgets to isolate is impossible by construction.
+4. **DAW-verify contract.** Both channels installed side-by-side; each browser sees only its
+   channel's banks; stable-project + beta-VST = clean empty (not error); the S-NAME-1
+   rename/rebind test extends to the beta UID.
+
+**Where the spec lives:** PLAN.md §S18; CONTEXT.md §VST3 channel identity — the UID pair + the
+pairing surface. The pairing surface's data half is already load-bearing V4 machinery; S18
+adds only the identity fork on top.
+
 ---
 
 ## Where this landed
@@ -626,11 +980,64 @@ into **Phase S** — a native VST3 sampler as a **second build artifact** alongs
 4. **D-D → embedded TCP/MCP UI scheduled** (**S6**), after the main editor exists — on the
    roadmap, not deferred.
 
-**Authoritative from here:** **PLAN.md §Phase S** is the roadmap (S1–S6, sequenced by
-dependency order: spike → `Sample` fields → pure sampler core → Tier 0 → Tier 1 → embedded
-UI); **CONTEXT.md §Phase S** is the spec (seam-field semantics, scope contracts, the
-pure/shell split in the new artifact, the must-verify SDK/bridge surfaces). This doc is the
-framing/decision record they point back to. The "no PLAN.md footprint" era is over.
+Two further directions set post-scoping (2026-07-26; see the Addendum in §4):
+
+5. **D-E → channel mode (mono | stereo), per-instance, bus-negotiated** (**S7**) — an
+   S3-core channel-dimension extension, sequenced first after the editor/embed work.
+6. **Ingest through the bank ("option 1"), extension-owned** (**S8**) + **bank-generation
+   hands-free refresh** (**S9**) — one-gesture capture/import + assign; the instrument stays
+   a read-only consumer.
+
+Post-DAW-test directives (2026-07-26; see the "product name + UX overhaul" Addendum in §4):
+
+7. **Product name → `ReaSampler 9000`** (VST3 class UID unchanged; **binary filename renamed
+   too — S-NAME-1 SETTLED r6**, compat is a DAW-verify).
+8. **UX overhaul → workflow-first, "better than RS5K"** (**S10–S13**; S10 **reframed r6**):
+   S10 = **capture browser (peak thumbnails + bank filter) + guided single-capture setup**,
+   **silent-on-open / no auto-select** (reverses S4), multi-zone editing demoted to an opt-in
+   Zones panel (S10-Z); S11 waveform + draggable loop points; S12 scroll/search over the S10
+   browser + numeric entry + ADSR; S13 drop-to-load folding in the S8 relay. Metric:
+   time-to-first-note.
+9. **Visual design language → modern/sleek, system-wide — moved to its own Phase L
+   (2026-07-26).** The look-and-feel work (a shared LICE drawing kit + the surfaces that
+   adopt it) was originally drafted here as Phase S points S0-DS + S14; it has been **lifted
+   out of Phase S into its own Phase L** (Look-and-feel) on `dev`, taken up by a parallel team
+   so Phase S feature work proceeds ungated. S0-DS → **L1** (shared kit); S14 → **L2**
+   (expanded to a thorough dock-panel layout redesign per DS-3); VST editor + embed restyle →
+   **L3** (gated on Phase S landing on dev). Forks DS-1 (LICE + WDL free game, no external
+   frameworks), DS-2 (Direction B "Neon Console" + Direction C's spectral keyboard strip), and
+   DS-3 (thorough panel layout) are all **SETTLED (2026-07-26)**. Framing + palette + the three
+   visual directions + forks: `docs/product/visual-design-language.md` (on `dev`); roadmap +
+   spec: **PLAN.md §Phase L + CONTEXT.md §Phase L** (on `dev`). **S10–S13 build with the
+   current drawing and adopt the L1 kit when it lands — not gated on Phase L.** Answers
+   Daniel's "the VST is dogshit / temple os / does Cockos have a toolkit" (2026-07-26,
+   post-S1–S6 DAW test).
+10. **Sampling modes + pitch engine → engine features** (**S15** Trigger vs Gate, **S16**
+    pitch-engine modes + pitch envelope; see the "sampling modes" r7 + "duration-preserving"
+    r8 Addenda in §4). Gate = AHDSR held note (hold added to today's ADSR); Trigger = one-shot
+    with %-length + fade-in/out, ignores note-off; both carry a modifiable start point; Gate
+    keeps loop points. **S16 reshaped (r8, Daniel's duration-preserving correction):** a per-
+    zone **pitch-engine mode — Varispeed** (current, cheap, pitch/duration coupled — classic
+    sampler, right for drums) **vs Preserve** (duration-preserving via a per-voice pitch
+    shifter — right for tempo-locked loops/phrases). Pitch envelope = per-voice AD, off by
+    default, riding either engine (biases `ratio_` under Varispeed, the shift amount under
+    Preserve). WDL verdict corrected: **`WDL_SimplePitchShifter` is the Preserve-engine
+    candidate** (duration-preserving OLA — RT-viable per-voice with pre-warm; the load-bearing
+    cost is onset latency), `WDL_Resampler` (sinc) held as a Varispeed-quality upgrade only; no
+    formant-preserving/elastique in WDL. Forks: **S16-F1** (engine default — lean Preserve,
+    Daniel's call), **S16-F2** (Preserve impl — WDL shifter first / hand-rolled held), plus
+    S15-F1 (choke, held) / S15-F2 (param granularity, lean per-zone). Feature set settled;
+    the engine default is Daniel's fork.
+
+**Authoritative from here:** **PLAN.md §Phase S** is the roadmap (S1–S6 the original
+dependency chain: spike → `Sample` fields → pure sampler core → Tier 0 → Tier 1 → embedded
+UI; then **S7** stereo, **S8** ingest, **S9** change-detection, **S10–S13** the ReaSampler
+9000 UX overhaul, **S15/S16** the Trigger-vs-Gate + pitch-engine-modes engine features);
+**CONTEXT.md §Phase S** is the spec (seam-field semantics, scope contracts, the channel-mode
+/ ingest / bank-generation / sampling-mode / pitch-engine contracts, the UX-overhaul spec,
+the product-name convention, the pure/shell split, the WDL finding, the must-verify
+SDK/bridge surfaces). This doc is the framing/decision record they point back to. The "no
+PLAN.md footprint" era is over.
 
 ---
 

src/actions.cpp

@@ -645,7 +645,9 @@ void doBankDelete() {
         ShowConsoleMsg("ReaSampler: cannot delete that bank (the pool is un-deletable).\n");
         return;
     }
-    persistBankOp("ReaSampler: delete bank");
+    // S9: bump only when the deleted bank held samples — dropping them changes what a live
+    // instance referencing one could play. Deleting an EMPTY bank is purely organizational.
+    persistBankOp("ReaSampler: delete bank", /*bumpGeneration=*/members > 0);
 }
 
 // Evacuate a named bank: move every member back to the pool (index-only, collapse by
@@ -666,7 +668,8 @@ void doBankEvacuate() {
                        "destination, not a source).\n");
         return;
     }
-    persistBankOp("ReaSampler: evacuate bank");
+    // S9: evacuate moves members between banks (bank membership changes) -> bump.
+    persistBankOp("ReaSampler: evacuate bank", /*bumpGeneration=*/true);
 }
 
 // Cycle the active bank forward in ordinal order (pool -> named -> ... -> pool),
@@ -752,7 +755,9 @@ void doBankTransferSelected(bool copy) {
     if (mutated) {
         const std::string label =
             std::string("ReaSampler: ") + verb + " sample(s)";
-        persistBankOp(label.c_str());
+        // S9: a move/copy changes bank membership (a sample arrives in / leaves a bank an
+        // instance may reference) -> bump so assigned instances refresh hands-free.
+        persistBankOp(label.c_str(), /*bumpGeneration=*/true);
     }
 }
 
@@ -794,7 +799,9 @@ void doBankRemoveSelected() {
     }
 
     // No-op guardrail (R-B): open an undo point only if the index actually mutated.
-    if (removed > 0) persistBankOp("ReaSampler: remove sample(s)");
+    // S9: a remove drops a sample from a bank (an instance referencing it must refresh — it
+    // will resolve to silence, per the stale-id policy) -> bump.
+    if (removed > 0) persistBankOp("ReaSampler: remove sample(s)", /*bumpGeneration=*/true);
 }
 
 // Prune bank folder — Phase R (Reclaim), R3: the guarded DESTRUCTIVE step, and the SOLE
@@ -884,8 +891,14 @@ void doBankPruneFolder() {
 // change stands and persists on the user's next save; it just earns no undo point until
 // there is a project to persist into (undo of an unsaved bank op has nothing to roll
 // back to anyway). The Begin/End must still be balanced, hence the close-either-way.
-void persistBankOp(const char* label) {
+void persistBankOp(const char* label, bool bumpGeneration) {
     Undo_BeginBlock2(nullptr);
+    // S9: bump the bank-generation counter INSIDE the block, before persistBook(), so the
+    // fresh generation rides the same ext-state write the persist makes (persistBook() ->
+    // saveToActiveProject() stamps bankGeneration()). Bumped only for content-changing verbs
+    // (the caller decides); a pure-organizational verb passes false and leaves the counter be,
+    // so a rename/activate does not needlessly refresh live instances.
+    if (bumpGeneration) g_session->bumpBankGeneration();
     const bool persisted = persistBook();
     if (persisted)
         Undo_EndBlock2(nullptr, label, UNDO_STATE_MISCCFG);

src/actions.h

@@ -79,6 +79,14 @@ int bankPruneCommandId();
 // must invoke this ONLY after a successful/effective mutation — rejected ops (duplicate
 // name, un-deletable pool, etc.) must return before reaching here so no empty undo
 // point is ever opened for a no-op. Defined in actions.cpp alongside persistBook().
-void persistBankOp(const char* label);
+//
+// S9 bank-generation bump: pass `bumpGeneration = true` for a verb that changes what a live
+// instance would PLAY — move / copy / remove / evacuate / delete-with-members (a sample left,
+// arrived, or dropped out of a bank an instance may reference). Leave it false (the default)
+// for a PURELY ORGANIZATIONAL verb — create / rename / activate / reorder — which changes no
+// existing (bankId, sampleId) -> content mapping, so no instance need refresh. The bump (when
+// requested) happens INSIDE the block, BEFORE persistBook(), so the stamped counter rides the
+// same ext-state write and undo captures the pre/post generation with the rest of the blob.
+void persistBankOp(const char* label, bool bumpGeneration = false);
 
 }  // namespace reasampler

src/app_version.cpp

@@ -86,6 +86,24 @@ const std::string& dockIdent() {
     return kIdent;
 }
 
+const std::string& vstOutputName() {
+    // The .vst3 module OUTPUT_NAME base — FOREVER-STABLE per channel. Stable is
+    // byte-identical to pre-S18 ("reasampler_9000"); beta is isolated so both install
+    // side-by-side without a filename collision.
+    static const std::string kName =
+        kIsBeta ? "reasampler_9000_beta" : "reasampler_9000";
+    return kName;
+}
+
+const std::string& vstPluginName() {
+    // The factory display name / editor title / embed label. Stable is byte-identical to
+    // pre-S18 ("ReaSampler 9000"); beta appends " beta" so the two channels are distinct
+    // plugins in the FX browser.
+    static const std::string kName =
+        kIsBeta ? "ReaSampler 9000 beta" : "ReaSampler 9000";
+    return kName;
+}
+
 std::string channelCommandId(const std::string& suffix) {
     return commandIdPrefix() + suffix;
 }

src/app_version.h

@@ -104,6 +104,33 @@ const std::string& binaryName();
 const std::string& dockTitle();
 const std::string& dockIdent();
 
+// --- VST3 instrument identity (S18, beta-in-isolation) ------------------------------
+//
+// The ReaSampler 9000 VST3 instrument forks its plugin identity per channel exactly as the
+// extension forks its binary/dock idents above — one channel per binary, all derived from
+// the ONE channel bit here, so the VST shell carries no #ifdef fork. These are the VST's
+// analogues of binaryName()/dockTitle(): the on-disk module name and the human-facing name.
+//
+//   vstOutputName() — the CMake OUTPUT_NAME base for the .vst3 module. Stable:
+//                     "reasampler_9000" (byte-identical to pre-S18). Beta:
+//                     "reasampler_9000_beta". Mirrors the CMake target's OUTPUT_NAME (the
+//                     authoritative artifact name); exposed here so the one derivation lives
+//                     in this module. FOREVER-STABLE per channel — the on-disk filename a
+//                     REAPER project's saved instance path may reference.
+//   vstPluginName() — the factory display name (FX browser), editor title band, and S6
+//                     embed-strip label. Stable: "ReaSampler 9000". Beta:
+//                     "ReaSampler 9000 beta". Sourced from here, never a literal in
+//                     reasampler_vst.h / vst_entry.cpp / the editor / the embed strip.
+//
+// NOTE: the VST3 CLASS UID is NOT here — a UID is not a string derivation but a compile-time
+// FUID/INLINE_UID constant the factory needs in brace-init form; it lives in reasampler_vst.h,
+// channel-selected by the same REASAMPLER_CHANNEL_IS_BETA bit. This module owns the string
+// identity; reasampler_vst.h owns the binary UID identity. The version display the factory
+// stamps into PClassInfo2 reuses appVersion() (it already renders "-beta" on beta) — no
+// separate VST version accessor.
+const std::string& vstOutputName();
+const std::string& vstPluginName();
+
 // --- Channel-qualified action id / name builders ------------------------------------
 //
 // The two composition helpers every action-registering shell (main.cpp, actions.cpp)

src/assignment_request.cpp

@@ -0,0 +1,147 @@
+// assignment_request.cpp — see assignment_request.h. Pure: standard library only.
+
+#include "assignment_request.h"
+
+#include <cstddef>
+#include <limits>
+
+namespace reasampler {
+
+namespace {
+
+constexpr const char* kMagic = "rsassign1";
+
+// Append one length-prefixed field:  <decimal-len> ':' <bytes>. Mirror of
+// provenance's putField so the two seams share one wire idiom.
+void putField(std::string& out, const std::string& field) {
+    out += std::to_string(field.size());
+    out += ':';
+    out += field;
+}
+
+// Cursor over the encoded string. All reads are bounds-checked; a short read fails
+// the whole parse (ok_ latches false). Mirror of provenance's Cursor, trimmed to the
+// three field kinds this record needs.
+class Cursor {
+public:
+    explicit Cursor(const std::string& s) : s_(s) {}
+
+    bool ok() const { return ok_; }
+    bool atEnd() const { return pos_ >= s_.size(); }
+
+    // Reads one length-prefixed field into `out`. Fails on a missing ':', an empty or
+    // non-numeric length, a length that overflows SIZE_MAX, or a length that runs past
+    // the end. The digit count is capped at 20 (the decimal width of SIZE_MAX on a
+    // 64-bit host) so a crafted 200-digit length cannot accumulate past SIZE_MAX via
+    // repeated multiply. "never UB" promise from the header is upheld here.
+    bool field(std::string& out) {
+        if (!ok_) return false;
+        const std::size_t colon = s_.find(':', pos_);
+        if (colon == std::string::npos) return fail();
+        if (colon == pos_) return fail();  // empty length token
+        // Cap: SIZE_MAX fits in at most 20 decimal digits; a longer run is bogus.
+        if (colon - pos_ > 20u) return fail();
+        std::size_t len = 0;
+        for (std::size_t i = pos_; i < colon; ++i) {
+            const char c = s_[i];
+            if (c < '0' || c > '9') return fail();
+            const std::size_t digit = static_cast<std::size_t>(c - '0');
+            // Overflow guard: if len would exceed SIZE_MAX after multiply+add, fail.
+            if (len > (std::numeric_limits<std::size_t>::max() - digit) / 10u)
+                return fail();
+            len = len * 10u + digit;
+        }
+        const std::size_t start = colon + 1;
+        // Guard: start may equal s_.size() (empty remainder), in which case only len==0
+        // is valid; start > s_.size() cannot happen (colon < s_.size() by find()).
+        // Use subtraction-first form to avoid start+len wrapping on a huge len.
+        if (start > s_.size() || len > s_.size() - start) return fail();
+        out.assign(s_, start, len);
+        pos_ = start + len;
+        return true;
+    }
+
+    // Reads a length-prefixed field and parses it as a signed 64-bit decimal (an
+    // optional leading '-'). Fails on empty, non-digit, trailing bytes, or a value
+    // that would overflow INT64_MAX / underflow INT64_MIN. The digit count is capped
+    // at 19 (the decimal width of INT64_MAX, plus 1 for the optional sign = 20
+    // characters maximum) so a crafted 21-digit field cannot accumulate UB. "never UB"
+    // promise from the header is upheld: all arithmetic is done on positive digits
+    // and capped before applying the sign.
+    bool fieldInt64(std::int64_t& out) {
+        std::string f;
+        if (!field(f)) return false;
+        if (f.empty()) return fail();
+        std::size_t i = 0;
+        bool neg = false;
+        if (f[0] == '-') {
+            neg = true;
+            i = 1;
+            if (f.size() == 1) return fail();  // bare "-"
+        }
+        // Cap at 19 digits (INT64_MAX = 9223372036854775807 — 19 digits). A 20-digit
+        // positive value would overflow INT64_MAX; a 20-digit negative might be valid
+        // (INT64_MIN = -9223372036854775808) but we conservatively reject it too: the
+        // generation field is a unix timestamp, never near INT64 limits in practice.
+        if (f.size() - i > 19u) return fail();
+        std::int64_t v = 0;
+        for (; i < f.size(); ++i) {
+            const char c = f[i];
+            if (c < '0' || c > '9') return fail();
+            const std::int64_t digit = static_cast<std::int64_t>(c - '0');
+            // Overflow guard: v * 10 + digit must not exceed INT64_MAX.
+            if (v > (std::numeric_limits<std::int64_t>::max() - digit) / 10)
+                return fail();
+            v = v * 10 + digit;
+        }
+        out = neg ? -v : v;
+        return true;
+    }
+
+    // Consumes an exact literal at the cursor (the magic tag). Fails if absent.
+    bool literal(const char* lit) {
+        if (!ok_) return false;
+        std::size_t i = 0;
+        for (; lit[i] != '\0'; ++i) {
+            if (pos_ + i >= s_.size() || s_[pos_ + i] != lit[i]) return fail();
+        }
+        pos_ += i;
+        return true;
+    }
+
+private:
+    bool fail() {
+        ok_ = false;
+        return false;
+    }
+
+    const std::string& s_;
+    std::size_t        pos_ = 0;
+    bool               ok_ = true;
+};
+
+}  // namespace
+
+std::string encodeAssignmentRequest(const AssignmentRequest& req) {
+    std::string out = kMagic;
+    putField(out, req.bankId);
+    putField(out, req.sampleId);
+    putField(out, std::to_string(req.generation));
+    return out;
+}
+
+std::optional<AssignmentRequest> decodeAssignmentRequest(const std::string& wire) {
+    Cursor cur(wire);
+    if (!cur.literal(kMagic)) return std::nullopt;
+
+    AssignmentRequest req;
+    if (!cur.field(req.bankId)) return std::nullopt;
+    if (!cur.field(req.sampleId)) return std::nullopt;
+    if (!cur.fieldInt64(req.generation)) return std::nullopt;
+
+    // Reject trailing garbage: a well-formed value ends exactly at the last field.
+    if (!cur.ok() || !cur.atEnd()) return std::nullopt;
+    return req;
+}
+
+}  // namespace reasampler

src/assignment_request.h

@@ -0,0 +1,89 @@
+#pragma once
+// assignment_request — the pure core of the S8 ingest assignment-request seam.
+//
+// PURE MODULE (CLAUDE.md §load-bearing split): NO REAPER types, NO SWELL, NO VST3,
+// NO vendor/ includes. Standard library only. Unit-tested outside the DAW — the same
+// "small pure type + length-prefixed round-trip" pattern as provenance / owned_manifest.
+//
+// -- What it is --------------------------------------------------------------
+//
+// When the EXTENSION ingests a sample (S8: arrange capture / Media-Explorer import /
+// drop-onto-panel) it writes an ASSIGNMENT REQUEST to its own "reasampler" ext-state
+// namespace: "the active sampler instance should now play THIS sample." The value
+// names the ingested sample by (bankId, sampleId) plus a monotonic `generation` the
+// reader compares to decide the request is NEW (a fresh ingest, even of the same id).
+//
+// This module owns ONLY the value's WIRE FORMAT — build/parse round-trip. Writing it
+// to ext-state is the persist shell's job; READING it is the instrument's job in a
+// LATER dispatch (S8 instrument-side follow-up, after S10 merges). This is why the
+// format is documented here in the header, not just in code: the reader lands elsewhere
+// and must decode exactly what this writer produced.
+//
+// -- The data-ownership boundary (load-bearing) ------------------------------
+//
+// The EXTENSION writes this; the instrument only READS it. That does not violate the
+// instrument's read-only-over-the-bank rule: the assignment request is the extension
+// writing its OWN namespace (a request FROM the extension TO the instrument), never the
+// instrument writing back into the bank. The instrument, on reading a new generation,
+// updates its OWN component-state selection (the same selection S4 persists) and reloads.
+//
+// -- Why `generation` -------------------------------------------------------
+//
+// Instances reference sample IDs, so re-assigning the SAME id (e.g. a recapture, or a
+// re-drop of the same file) would be indistinguishable from a stale value without a
+// changing field. `generation` is a monotonic disambiguator (the ingest writer supplies
+// a wall-clock unix-epoch stamp today — see the writer shell) so the reader can tell
+// "assigned again just now" from "already saw this." It is DELIBERATELY the same shape
+// the S9 bank-generation counter will use, but it is NOT that counter — S9 is a separate
+// point; this field is self-contained to the request and does not depend on S9 landing.
+
+#include <cstdint>
+#include <optional>
+#include <string>
+
+namespace reasampler {
+
+// One assignment request: the ingested sample's identity + a monotonic disambiguator.
+//   bankId     — the bank the sample was ingested into (the active/target bank).
+//   sampleId   — the ingested Sample's stable id (BankIndex key).
+//   generation — a monotonic value the reader compares to detect a NEW request. The
+//                writer supplies a unix-epoch-seconds stamp; the reader treats it as an
+//                opaque "did this change?" token, not a wall-clock it interprets.
+struct AssignmentRequest {
+    std::string  bankId;
+    std::string  sampleId;
+    std::int64_t generation = 0;
+
+    bool operator==(const AssignmentRequest& o) const {
+        return bankId == o.bankId && sampleId == o.sampleId &&
+               generation == o.generation;
+    }
+    bool operator!=(const AssignmentRequest& o) const { return !(*this == o); }
+};
+
+// Encode an assignment request to the wire string. Length-prefixed fields behind a
+// magic+version tag ("rsassign1"), so arbitrary bytes in an id (a GUID, a display-
+// derived id) round-trip whole with no escaping ambiguity — the same idiom provenance
+// uses. Deterministic: the same request always yields the same string.
+//
+// FORMAT (documented for the LATER instrument-side reader):
+//   "rsassign1" <len>':'<bankId> <len>':'<sampleId> <len>':'<generation-decimal>
+// where each <len> is the decimal byte length of the field that follows the ':'.
+std::string encodeAssignmentRequest(const AssignmentRequest& req);
+
+// Parse a wire string produced by encodeAssignmentRequest. std::nullopt on any
+// malformed / truncated / trailing-garbage input (never UB, never a partial value) —
+// the reader shell treats absence/malformed as "no pending request." Round-trips:
+// decodeAssignmentRequest(encodeAssignmentRequest(x)) == x.
+//
+// READER REQUIREMENT (instrument-side, S8 follow-up dispatch): after successfully
+// decoding a request, the reader MUST verify that (bankId, sampleId) resolves to an
+// existing sample before acting on it. An undo on the extension side rolls back the
+// `banks` ext-state key (removing the sample) but cannot atomically clear the
+// `assign_request` key if the write happened outside the undo block. Even with the
+// undo-grouping fix (Major 2), the reader must guard against this: treat an
+// unresolvable (bankId, sampleId) pair as a stale/no-op request and discard it
+// silently, never crashing or selecting a nonexistent entry.
+std::optional<AssignmentRequest> decodeAssignmentRequest(const std::string& wire);
+
+} // namespace reasampler

src/bank_model.cpp

@@ -35,6 +35,10 @@ bool Levels::operator==(const Levels& o) const {
     return peakDb == o.peakDb && rmsDb == o.rmsDb && lufs == o.lufs;
 }
 
+bool LoopPoints::operator==(const LoopPoints& o) const {
+    return start == o.start && end == o.end;
+}
+
 bool Sample::operator==(const Sample& o) const {
     return id == o.id && displayName == o.displayName && relativePath == o.relativePath &&
            sourceMode == o.sourceMode && sourceRange == o.sourceRange &&
@@ -43,7 +47,8 @@ bool Sample::operator==(const Sample& o) const {
            lengthSeconds == o.lengthSeconds && lengthBeats == o.lengthBeats &&
            captureTempo == o.captureTempo &&
            captureTimeSigNum == o.captureTimeSigNum &&
-           captureTimeSigDenom == o.captureTimeSigDenom && key == o.key && levels == o.levels &&
+           captureTimeSigDenom == o.captureTimeSigDenom && key == o.key &&
+           rootNote == o.rootNote && loop == o.loop && levels == o.levels &&
            clipped == o.clipped && tier == o.tier && contentHash == o.contentHash &&
            provenance == o.provenance && createdTimestamp == o.createdTimestamp;
 }
@@ -253,6 +258,21 @@ void writeSample(std::string& out, const Sample& s) {
     w.keyBegin("key");
     if (s.key) writeEscaped(out, *s.key); else out += "null";
 
+    // Phase S seam fields (D-B). Emitted as null when absent (same shape as `key`
+    // and `provenance`) so pre-Phase-S JSON — which lacks these keys entirely —
+    // parses to empty optionals and re-serializes without invention.
+    w.keyBegin("rootNote");
+    if (s.rootNote) out += numToStr(*s.rootNote); else out += "null";
+
+    w.keyBegin("loop");
+    if (s.loop) {
+        ObjWriter lp(out);
+        lp.keyRaw("start", numToStr(s.loop->start));
+        lp.keyRaw("end", numToStr(s.loop->end));
+    } else {
+        out += "null";
+    }
+
     w.keyBegin("levels");
     {
         ObjWriter l(out);
@@ -608,6 +628,41 @@ bool Parser::parseSample(Sample& s) {
                 if (!parseString(k)) return false;
                 s.key = k;
             }
+        } else if (key == "rootNote") {
+            bool wasNull = false;
+            if (!expectNullOr(wasNull)) return false;
+            if (wasNull) {
+                s.rootNote.reset();
+            } else {
+                int v = 0;
+                if (!parseInt(v)) return false;
+                // Valid MIDI note range: 0..127 inclusive (boundaries valid).
+                if (v < 0 || v > 127) return false;
+                s.rootNote = v;
+            }
+        } else if (key == "loop") {
+            bool wasNull = false;
+            if (!expectNullOr(wasNull)) return false;
+            if (wasNull) {
+                s.loop.reset();
+            } else {
+                if (!consume('{')) return false;
+                LoopPoints lp;
+                do {
+                    std::string lk;
+                    if (!parseKey(lk)) return false;
+                    std::int64_t lv = 0;
+                    if (!parseInt64(lv)) return false;
+                    if (lk == "start") lp.start = lv;
+                    else if (lk == "end") lp.end = lv;
+                } while (consume(','));
+                if (!consume('}')) return false;
+                // Invariant: 0 <= start <= end. start == end is a valid zero-length
+                // marker; a negative index or start > end is malformed, not silently
+                // clamped (mirrors the enum-range rejection above).
+                if (lp.start < 0 || lp.end < lp.start) return false;
+                s.loop = lp;
+            }
         } else if (key == "levels") {
             if (!consume('{')) return false;
             do {

src/bank_model.h

@@ -63,6 +63,22 @@ struct Levels {
     bool operator==(const Levels& o) const;
 };
 
+// Sample-accurate sustain-loop bounds, as frame indices into the captured file
+// (Phase S seam field, D-B). A bank intrinsic — a fact about the file, like
+// sampleRate or length — consumed by the future MIDI-playback instrument to hold
+// notes past the recorded length. Modeled as one optional struct (not two loose
+// optionals) so "both points or neither" is a structural invariant, not a rule to
+// re-check at every boundary. Frame indices, not seconds, because the loop is a
+// per-sample-frame contract; the instrument reads the file's sample rate to relate
+// them to time. Invariant (enforced at the deserialize boundary): 0 <= start <= end.
+// start == end is a valid zero-length loop marker.
+struct LoopPoints {
+    std::int64_t start = 0;
+    std::int64_t end   = 0;
+
+    bool operator==(const LoopPoints& o) const;
+};
+
 // The metadata record for one captured sample. The audio itself lives in a
 // project-relative file; `relativePath` is ALWAYS relative (enforced at the
 // BankIndex::add boundary — see AddResult).
@@ -95,6 +111,18 @@ struct Sample {
 
     std::optional<std::string> key;  // musical key, when known
 
+    // Phase S seam fields (D-B) — bank intrinsics for the MIDI-playback instrument,
+    // additive like `provenance` (M1). Both default cleanly empty: pre-Phase-S
+    // samples deserialize without them and re-serialize without inventing values.
+    //  - rootNote: MIDI note (0..127) the sample was recorded at, so the instrument
+    //    can repitch it across the keyboard. DISTINCT from the musical `key` above:
+    //    `key` is a human label ("F#m"); `rootNote` is the exact pitch for repitch.
+    //    Populated at/after capture only where derivable — left empty (never guessed)
+    //    when the source is not a single played note.
+    //  - loop: sustain-loop bounds, populated only where explicitly set.
+    std::optional<int>        rootNote;
+    std::optional<LoopPoints> loop;
+
     Levels levels;
     bool   clipped = false;
 

src/bank_panel.cpp

@@ -61,6 +61,9 @@
 #include "draw_kit.h"      // kit text() over cached AA fonts — retires GDI DrawText (L1)
 #include "footer_bar.h"    // pure footer LEFT-group layout: toggle + count + Tail button (L4)
 #include "guid_diff.h"     // GuidBaseline — new-content detection (D2 Wave 2)
+#include "ingest.h"        // ingestDroppedFiles — S8 drop-onto-panel ingest
+#include "instrument_drop.h"      // pure buildInstrumentDropChunk — the vst_chunk blob (S17)
+#include "instrument_drop_win.h"  // resolveFxDropTarget / performInstrumentDrop shell (S17)
 #include "item_read.h"     // itemGuid / itemLaneName — shared item-read seam (D2 W3-B)
 #include "lane_keys.h"     // managed/manual lane heuristic (D2 Wave 2)
 #include "mode_enable.h"   // opposite-mode tag-button enablement predicate (pure, L5)
@@ -82,6 +85,7 @@
 #ifdef _WIN32
 #include <windows.h>
 #include <windowsx.h>  // GET_X_LPARAM / GET_Y_LPARAM (SWELL supplies them on mac/linux)
+#include <shellapi.h>  // DragAcceptFiles / DragQueryFile / DragFinish — S8 drop ingest
 #else
 #include <pthread.h>
 #endif
@@ -319,6 +323,15 @@ struct PanelState {
     CardGesture cardGesture = CardGesture::None;
     int         dragTargetSlot = -1;
 
+    // --- S17 drop-and-load (InstrumentDrop) -----------------------------------
+    // While a SINGLE-capture drag is over REAPER's own UI outside the panel, the drag is an
+    // InstrumentDrop heading for a track's TCP FX button. The shell hover-tracks the FX
+    // hotspot; on release over a valid target it adds a ReaSampler 9000 preloaded with the
+    // dragged capture (no OS drag, no timeline insert). instrumentDropTrack is the last
+    // resolved FX-hotspot track (null when the pointer is not over an FX button) — read on
+    // release. Only set/used on Windows (D5); the M11 OsDrag and internal drag are untouched.
+    MediaTrack* instrumentDropTrack = nullptr;
+
     // --- Tail-mode toggle -----------------------------------------------------
     // The authoritative tail setting now lives in ReaSamplerSession (session->tail()),
     // NOT in panel state, so it travels inside the .rpp (persist serializes it on save,
@@ -2057,7 +2070,10 @@ void doDeleteBank(const std::string& bankId) {
         // r == 6 (Yes) falls through to a plain delete (drops members).
     }
     if (!book()->deleteBank(bankId)) return;
-    persistBankOp("ReaSampler: delete bank");
+    // S9: bump when the bank held samples (either the Yes-drop path or the No-evacuate-then-
+    // delete path moved/dropped members) — both change what a live instance could play. An
+    // empty-bank delete is purely organizational, no bump.
+    persistBankOp("ReaSampler: delete bank", /*bumpGeneration=*/members > 0);
     // shownBankId is reconciled by the next fingerprint pass. If no named banks remain,
     // nudge focus to the pool so the selection has a valid home.
     if (namedBanks().empty()) g_panel.focusedRegion = Region::Pool;
@@ -2069,7 +2085,7 @@ void doEvacuateBank(const std::string& bankId) {
     const Bank* bk = book()->bank(bankId);
     if (!bk || bk->isPool()) return;
     if (!book()->evacuate(bankId)) return;
-    persistBankOp("ReaSampler: evacuate bank");
+    persistBankOp("ReaSampler: evacuate bank", /*bumpGeneration=*/true);  // S9: membership changed
     invalidatePanel();
 }
 
@@ -2113,7 +2129,7 @@ void transferSamples(const std::vector<std::string>& sampleIds,
     if (!mutated) return;  // nothing changed — no persist, no undo point
 
     const char* label = copy ? "ReaSampler: copy sample(s)" : "ReaSampler: move sample(s)";
-    persistBankOp(label);
+    persistBankOp(label, /*bumpGeneration=*/true);  // S9: bank membership changed
     // The selection indexed into the source; after a move those indices are stale, so
     // clear it (the fingerprint pass will also clear, but do it now for immediacy).
     g_panel.selection = Selection{};
@@ -2138,7 +2154,7 @@ void removeSamples(const std::vector<std::string>& sampleIds,
             ++removed;
     if (removed == 0) return;  // nothing changed — no persist, no undo point
 
-    persistBankOp("ReaSampler: remove sample(s)");
+    persistBankOp("ReaSampler: remove sample(s)", /*bumpGeneration=*/true);  // S9: sample dropped
     // The selection indexed into the source; after a remove those indices are stale, so
     // clear it (the fingerprint pass will also clear, but do it now for immediacy).
     g_panel.selection = Selection{};
@@ -2912,16 +2928,52 @@ void onMouseMove(int x, int y) {
         }
     }
     if (g_panel.dragging) {
-        // M11 gesture boundary (invariant #4): while a drag with samples is under way, the
-        // moment the pointer LEAVES the panel client area the gesture becomes OS-bound —
-        // hand the payload to the native OS drag. Inside the client area it stays the
-        // existing internal bank-to-bank drag, byte-identical. The boundary decision is the
-        // pure drag_out::decideGesture (drag state + pointer + client rect).
+        // M11 gesture boundary, REFINED by S17. While a drag with samples is under way and the
+        // pointer is INSIDE the client rect it stays the internal bank-to-bank drag (invariant
+        // #4, byte-identical). Once it LEAVES the client rect the pure drag_out::decideGesture
+        // splits the outside case three ways: a single-capture drag over REAPER's OWN UI is an
+        // InstrumentDrop (hover-track the FX button, drop on release); a multi-capture drag OR a
+        // pointer that has left REAPER entirely is the unchanged M11 OsDrag; inside stays
+        // Internal. The shell supplies the "over REAPER's UI" predicate via GetThingFromPoint.
         RECT cr{};
         GetClientRect(g_panel.hwnd, &cr);
         const PanelClientRect client{cr.left, cr.top, cr.right - cr.left, cr.bottom - cr.top};
-        const DragState st{/*dragging=*/true, /*hasArmedSamples=*/!g_panel.dragSampleIds.empty()};
-        if (decideGesture(x, y, client, st) == DragGesture::OsDrag) {
+        const bool inside = (x >= cr.left && x < cr.right && y >= cr.top && y < cr.bottom);
+
+        DragState st{/*dragging=*/true, /*hasArmedSamples=*/!g_panel.dragSampleIds.empty()};
+        st.singleCapture = (g_panel.dragSampleIds.size() == 1);
+
+        // Resolve the FX drop target only when OUTSIDE the client rect (the S17 middle case can
+        // only arise there) and only for a single-capture payload — the SDK hit-test is skipped
+        // on the common internal-drag path so it costs nothing there. The screen conversion is
+        // Windows-only (D5); resolveFxDropTarget owns the REAPER hit query.
+        FxDropTarget fx;
+        if (!inside && st.singleCapture) {
+            POINT sp{x, y};
+            ClientToScreen(g_panel.hwnd, &sp);
+            fx = resolveFxDropTarget(sp.x, sp.y);
+            st.overReaperUi = fx.overReaperUi;
+        }
+
+        const DragGesture gesture = decideGesture(x, y, client, st);
+
+        if (gesture == DragGesture::InstrumentDrop) {
+            // Track the FX hotspot for the release; the highlight is REAPER's own FX-button
+            // hover feedback under the pointer (the drop is driven on button-up). We keep the
+            // internal-drag capture alive so we keep receiving moves (unlike OsDrag, this does
+            // NOT hand off to a modal OS loop). Clear any internal drop-target highlight so the
+            // panel does not also paint a bank-drop cue while the drag is out over a track.
+            g_panel.instrumentDropTrack = fx.valid() ? fx.track : nullptr;
+            g_panel.dropKind = DropKind::None;
+            g_panel.dropBankId.clear();
+            invalidatePanel();
+            return;
+        }
+
+        // Left InstrumentDrop territory (back inside, or over a non-FX area): drop the FX target.
+        g_panel.instrumentDropTrack = nullptr;
+
+        if (gesture == DragGesture::OsDrag) {
             // Resolve the payload to existing on-disk paths BEFORE tearing down internal
             // drag state (the resolver reads dragSourceBankId / dragSampleIds).
             const std::vector<std::string> paths = resolveDragPathsForOs();
@@ -2983,6 +3035,20 @@ void doReplaceDrop(const std::string& newId, const std::string& oldId,
     invalidatePanel();
 }
 
+// Clears all drag-state fields to their resting values. Called from every exit path
+// (button-up, WM_CAPTURECHANGED, WM_DESTROY, closePanel) so the set of cleared fields
+// stays consistent across all four sites.
+void resetDragState() {
+    g_panel.dragArmed = false;
+    g_panel.dragging = false;
+    g_panel.dropKind = DropKind::None;
+    g_panel.dropBankId.clear();
+    g_panel.cardGesture = CardGesture::None;
+    g_panel.dragTargetSlot = -1;
+    g_panel.dragPrimaryId.clear();
+    g_panel.instrumentDropTrack = nullptr;
+}
+
 // Commits (or abandons) a drag on button-up. The resolved pure CardGesture decides:
 //   * Reorder / Replace -> in-grid, within the source bank (L7); one Ctrl-Z each.
 //   * Move / Copy       -> the EXISTING cross-bank transfer (unchanged; Ctrl = copy).
@@ -2990,6 +3056,19 @@ void doReplaceDrop(const std::string& newId, const std::string& oldId,
 // OsDragOut is never seen here: the pointer-left-client handoff happens live in onMouseMove.
 void onLBtnUp(int x, int y) {
     if (g_panel.dragging) {
+        // S17 drop-and-load: a release while hover-tracking a valid FX hotspot instantiates a
+        // ReaSampler 9000 on that track preloaded with the dragged capture — NOT a bank move,
+        // NOT an OS drag, NEVER a timeline insert. Takes priority over the L7 in-grid / cross-bank
+        // drop (the pointer is out over a track, not over a bank region). Single-capture only (the
+        // gesture never armed for a multi payload), so dragSampleIds.front() is the capture.
+        if (g_panel.instrumentDropTrack && g_panel.dragSampleIds.size() == 1) {
+            const std::string sampleId = g_panel.dragSampleIds.front();
+            const std::string chunk = buildInstrumentDropChunk(sampleId);
+            performInstrumentDrop(g_panel.instrumentDropTrack, chunk);
+            // Read-only over the bank + arrange: the ONLY mutations are the new FX instance +
+            // its state (both undoable in performInstrumentDrop). No book change, no ext-state,
+            // no dirty-mark here.
+        } else {
             updateDropTarget(x, y);
             classifyCardDrag(x, y);  // re-resolve at the drop point (modifiers may have changed)
             const CardGesture g = g_panel.cardGesture;
@@ -3017,6 +3096,7 @@ void onLBtnUp(int x, int y) {
                                     /*copy=*/g == CardGesture::Copy);
                 }
             }
+        }
         // CardGesture::None -> no-op drop (dead space, or same-bank gap resolved to None).
         SetCursor(LoadCursor(nullptr, IDC_ARROW));  // restore the arrow on drop
         if (GetCapture() == g_panel.hwnd) ReleaseCapture();
@@ -3029,13 +3109,7 @@ void onLBtnUp(int x, int y) {
         if (focus >= 0)
             g_panel.selection = applyClick(g_panel.selection, focus, false, false, count);
     }
-    g_panel.dragArmed = false;
-    g_panel.dragging = false;
-    g_panel.dropKind = DropKind::None;
-    g_panel.dropBankId.clear();
-    g_panel.cardGesture = CardGesture::None;
-    g_panel.dragTargetSlot = -1;
-    g_panel.dragPrimaryId.clear();
+    resetDragState();
     invalidatePanel();
 }
 
@@ -3075,8 +3149,35 @@ void handleRightClick(int x, int y) {
 
 // --- Dialog proc + docking ----------------------------------------------------
 
+// Decodes a WM_DROPFILES HDROP into the dropped file paths (absolute, OS-native) and hands
+// them to the S8 ingest path. Multi-file drop: ingestDroppedFiles imports all and assigns
+// the first. Always DragFinish's the HDROP (frees the shell-allocated drop buffer) on every
+// path. DragQueryFile(hDrop, 0xFFFFFFFF, ...) returns the file count; then each path is
+// queried by index. Both Win32 and SWELL expose DragQueryFile/DragFinish with this contract.
+void handleDropFiles(HDROP hDrop) {
+    std::vector<std::string> paths;
+    const UINT count = DragQueryFile(hDrop, 0xFFFFFFFF, nullptr, 0);
+    paths.reserve(count);
+    for (UINT i = 0; i < count; ++i) {
+        // Query the required length first (excludes the NUL), then read into a sized buffer.
+        const UINT len = DragQueryFile(hDrop, i, nullptr, 0);
+        if (len == 0) continue;
+        std::vector<char> buf(static_cast<std::size_t>(len) + 1, '\0');
+        DragQueryFile(hDrop, i, buf.data(), static_cast<UINT>(buf.size()));
+        std::string p(buf.data());
+        if (!p.empty()) paths.push_back(std::move(p));
+    }
+    DragFinish(hDrop);
+    if (!paths.empty()) ingestDroppedFiles(paths);
+}
+
 WDL_DLGRET dlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
     switch (msg) {
+        case WM_DROPFILES:
+            // S8 drop-onto-panel ingest: OS file drop on the docked panel HWND -> import
+            // into the active bank + assign the first. wParam is the HDROP.
+            handleDropFiles(reinterpret_cast<HDROP>(wParam));
+            return 0;
         case WM_PAINT: {
             PAINTSTRUCT ps;
             HDC hdc = BeginPaint(hwnd, &ps);
@@ -3105,13 +3206,7 @@ WDL_DLGRET dlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
             // state lingers, mirroring onLBtnUp's reset (peer-path symmetry). Nothing is
             // mutated on a cancel; the cursor is restored to the arrow.
             if (g_panel.dragArmed || g_panel.dragging) {
-                g_panel.dragArmed = false;
-                g_panel.dragging = false;
-                g_panel.dropKind = DropKind::None;
-                g_panel.dropBankId.clear();
-                g_panel.cardGesture = CardGesture::None;
-                g_panel.dragTargetSlot = -1;
-                g_panel.dragPrimaryId.clear();
+                resetDragState();
                 SetCursor(LoadCursor(nullptr, IDC_ARROW));
                 invalidatePanel();
             }
@@ -3133,10 +3228,7 @@ WDL_DLGRET dlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
             if (GetCapture() == hwnd) ReleaseCapture();
             stopAudition();
             g_panel.selection = Selection{};
-            g_panel.dragArmed = g_panel.dragging = false;
-            g_panel.cardGesture = CardGesture::None;
-            g_panel.dragTargetSlot = -1;
-            g_panel.dragPrimaryId.clear();
+            resetDragState();
             g_panel.hovered = Hover{};
             g_panel.tooltipShown = false;
             g_panel.hwnd = nullptr;
@@ -3172,6 +3264,17 @@ void openPanel() {
     DockWindowActivate(g_panel.hwnd);
     g_panel.open = true;
 
+    // S8: accept OS file drops on the panel HWND (WM_DROPFILES routes to handleDropFiles).
+    // DragAcceptFiles is a native Win32 shell call (shellapi.h); SWELL does NOT expose it,
+    // so the opt-in is Windows-only here. The primary/shipped platform is Windows (the VST3
+    // instrument the drop assigns to is Windows-only, D5); a mac/linux drop-registration
+    // surface is out of scope for this dispatch. WM_DROPFILES handling itself uses
+    // DragQueryFile/DragFinish, which SWELL DOES provide, so a drop delivered by other means
+    // would still ingest — only the accept opt-in is gated.
+#ifdef _WIN32
+    DragAcceptFiles(g_panel.hwnd, TRUE);
+#endif
+
     registerAccel();
 
     reconcileShownBank();
@@ -3182,7 +3285,7 @@ void closePanel() {
     if (GetCapture() == g_panel.hwnd) ReleaseCapture();
     stopAudition();
     g_panel.selection = Selection{};
-    g_panel.dragArmed = g_panel.dragging = false;
+    resetDragState();
     unregisterAccel();
     if (g_panel.hwnd) {
         DockWindowRemove(g_panel.hwnd);

src/capture.cpp

@@ -530,6 +530,11 @@ CaptureResult OfflineRenderBackend::capture(const CaptureRequest& request) {
         }
     }
     s.createdTimestamp = static_cast<std::int64_t>(std::time(nullptr));
+    // Phase S seam fields (rootNote / loop) left empty (D-B). An offline render of a
+    // master mix / track / time-selection is not a single played note, so no root
+    // note is derivable here — we do NOT guess one. Loop points are set later by an
+    // explicit user action, not at capture. Leaving them empty is the honest default;
+    // the instrument (Phase S) treats an absent root note as "not a pitched sample".
 
     result.status  = CaptureStatus::Ok;
     result.sample  = s;

src/capture_paths.cpp

@@ -5,6 +5,7 @@
 #include <cstdint>
 #include <cstdio>
 #include <cstring>  // std::memcmp
+#include <filesystem>
 #include <vector>
 
 namespace reasampler {
@@ -213,6 +214,15 @@ std::string resolveBankFile(const std::string& projectDir,
     return dir + "/" + rel;
 }
 
+std::string projectDirOfRpp(const std::string& rppPath) {
+    // An unsaved project reports an empty .rpp path; keep it empty so downstream
+    // resolution refuses (no default-location fallback). Mirrors persist.cpp's prior
+    // projectDirOf exactly: parent_path of the .rpp, then normalizeSlashes.
+    if (rppPath.empty()) return {};
+    std::string dir = std::filesystem::path(rppPath).parent_path().string();
+    return normalizeSlashes(dir);
+}
+
 BankRelocation deriveRelocationPlan(const std::string& oldProjectDir,
                                     const std::string& newProjectDir) {
     BankRelocation r;

src/capture_paths.h

@@ -121,6 +121,14 @@ std::string bankRelativeForName(const std::string& fileName);
 std::string resolveBankFile(const std::string& projectDir,
                             const std::string& relativePath);
 
+// The project directory that holds a .rpp: its parent directory, forward-slashed,
+// trailing slash stripped. Empty in -> empty out (an unsaved project has an empty
+// .rpp path, which must stay empty so resolveBankFile refuses to resolve — the
+// no-default-location invariant). This is the M4 convention persist uses to place
+// the bank alongside the .rpp; extracted here (pure) so the VST3 instrument resolves
+// audio paths the SAME way persist does rather than re-implementing the derivation.
+std::string projectDirOfRpp(const std::string& rppPath);
+
 // A relocation plan for the physical bank folder on Save-As to a new project
 // location. The index's relative paths do NOT change (they are relative to the
 // project dir, which is what moved with the .rpp), so relocation is purely a

src/drag_out.cpp

@@ -19,7 +19,13 @@ bool insideClient(int px, int py, const PanelClientRect& c) {
 DragGesture decideGesture(int px, int py, const PanelClientRect& client,
                           const DragState& state) {
     if (!state.dragging || !state.hasArmedSamples) return DragGesture::None;
-    return insideClient(px, py, client) ? DragGesture::Internal : DragGesture::OsDrag;
+    if (insideClient(px, py, client)) return DragGesture::Internal;
+    // Outside the client rect (M11 boundary), refined by S17: a SINGLE-capture drag that is
+    // still over REAPER's own UI is an instrument drop (heading for a track's FX button);
+    // anything else (a multi-capture payload, or the pointer off REAPER entirely) is the
+    // unchanged M11 OS drag-out.
+    if (state.singleCapture && state.overReaperUi) return DragGesture::InstrumentDrop;
+    return DragGesture::OsDrag;
 }
 
 PathList assemblePathList(const std::vector<ResolvedSample>& resolved) {

src/drag_out.h

@@ -52,28 +52,50 @@ struct PanelClientRect {
 // whether a drag is currently active (threshold crossed) and whether the armed payload
 // carries at least one sample. (Pre-threshold "armed but not yet dragging" is NOT a drag
 // for this decision — the shell only asks once a drag is under way.)
+//
+// S17 (drop-and-load) adds two inputs that refine the OUTSIDE-the-panel decision without
+// touching the INSIDE decision (the internal bank-to-bank drag stays byte-identical):
+//   * singleCapture — the payload holds EXACTLY ONE sample id. Only a single-capture drag
+//     arms the InstrumentDrop gesture (per the S17 open-question lean: a multi-capture drag
+//     over an FX button is NOT an instrument drop — it falls through to OsDrag, the natural
+//     multi-file drag-out to Explorer/another DAW). REJECT, not load-first: the whole gesture
+//     is "make ONE capture a playable instrument", so a multi payload is out of contract here.
+//   * overReaperUi — a SHELL-SUPPLIED predicate: true when the pointer, though outside the
+//     panel client rect, is still over REAPER's OWN window/UI (the shell owns the REAPER
+//     hit query, e.g. GetThingFromPoint; the pure layer owns only the set/boundary algebra).
+// Both default false, so an M11-era caller that fills only {dragging, hasArmedSamples} gets
+// EXACTLY the M11 behavior: outside the client rect with overReaperUi=false -> OsDrag.
 struct DragState {
     bool dragging = false;       // threshold crossed; a drag is in progress
     bool hasArmedSamples = false; // the drag payload holds >= 1 sample id
+    bool singleCapture = false;  // S17: payload holds EXACTLY one sample (arms InstrumentDrop)
+    bool overReaperUi = false;   // S17: pointer is over REAPER's own UI (shell-supplied)
 };
 
 // What the shell should do with the drag given the current pointer position.
 enum class DragGesture {
     None,           // no drag under way, or an empty payload — do nothing
     Internal,       // dragging inside the panel — the existing bank-to-bank move/copy drag
-    OsDrag,    // dragging with samples, pointer left the client area — hand off to the OS
+    InstrumentDrop, // S17: single-capture drag left the panel but is over REAPER's UI —
+                    // the shell hover-tracks the TCP FX button and, on release, adds a
+                    // ReaSampler 9000 instance preloaded with the dragged capture.
+    OsDrag,         // dragging with samples, pointer left REAPER entirely — hand off to the OS
 };
 
 // Decides the gesture for a drag at pointer (px, py) over `client`, given `state`.
 //   * Not dragging (or no armed samples): None — the shell ignores the move.
 //   * Dragging with samples, pointer INSIDE the client rect: Internal — unchanged
 //     bank-to-bank behavior (invariant #4: the internal drag stays byte-identical).
-//   * Dragging with samples, pointer OUTSIDE the client rect: OsDrag — the samples are
-//     leaving the panel; the shell initiates the native OS drag with the resolved paths.
-// The boundary is the client rect edge: the internal drag never targets outside it, so
-// crossing it is an unambiguous, discoverable OS-drag trigger. Re-entry is the shell's
-// concern (the OS drag loop is modal once begun); this function reports OsDrag purely from
-// position, so a shell that has already handed off simply will not ask again.
+//   * Dragging OUTSIDE the client rect, SINGLE capture, over REAPER's UI: InstrumentDrop —
+//     the drag is heading for a track's FX button (S17); the shell hover-tracks + highlights.
+//   * Dragging OUTSIDE the client rect otherwise (multi-capture, OR the pointer has left
+//     REAPER entirely): OsDrag — the samples are leaving to the OS; the shell initiates the
+//     native OS drag with the resolved paths.
+// The INSIDE decision is untouched (M11 internal drag is byte-identical). The M11 boundary
+// (left the client rect -> OsDrag) is REFINED, not replaced: leaving the rect now asks
+// "single-capture and over REAPER's UI -> InstrumentDrop, else -> OsDrag" — so the M11
+// OS-drag-out (multi payload, or pointer off REAPER) keeps its exact behavior. Position-only
+// + state-only (no hidden state), so re-entry back inside returns Internal.
 DragGesture decideGesture(int px, int py, const PanelClientRect& client,
                           const DragState& state);
 

src/ext_keys.h

@@ -0,0 +1,72 @@
+#pragma once
+// ext_keys — the SINGLE SOURCE OF TRUTH for the "reasampler" project ext-state
+// namespace + key names, shared by the extension (writer, via persist.h) and the
+// VST3 instrument (reader, via the bridge). Both sides include this header so the
+// wire contract cannot drift between the two artifacts (the S4 reviewer flagged the
+// spike's duplicated constants as a drift risk).
+//
+// PURE HEADER: NO REAPER types, NO VST3 types, NO SWELL, NO vendor/ includes. The key
+// spellings are string constants; the NAMESPACE is channel-derived (Phase V, V4) so it
+// delegates to the pure app_version module (also REAPER-free / VST3-free). Both the
+// REAPER-facing persist shell and the SDK-facing VST bridge include this without pulling
+// either SDK.
+//
+// FOREVER-STABLE once shipped: these strings key every already-saved project's
+// stored state. Changing any of them orphans that state. See persist.h for the
+// per-key retirement / migration semantics — this header only owns the spellings.
+
+#include "app_version.h"
+
+namespace reasampler {
+
+// The ext-state namespace all ReaSampler project state is stored under. CHANNEL-DERIVED
+// (Phase V, V4): delegates to the ONE app_version symbol so the extension (writer) and the
+// VST3 instrument (reader) resolve the SAME namespace per channel — "reasampler" on stable,
+// "reasampler_beta" on the isolated beta build. An accessor (not a constexpr literal)
+// because the value is fixed by the channel bit at build time. This is the wire-contract
+// reconciliation between S4 (shared ext_keys) and V4 (channel-isolated namespace): without
+// it a beta instrument would read the stable namespace and see empty state.
+inline const char* kProjExtNamespace() { return extStateNamespace().c_str(); }
+
+// The multi-bank key: the whole serialized BankBook (pool + named banks). This is
+// the key the VST3 instrument reads to see the live bank (read-only, S4). persist.h
+// documents its authority + the legacy-key migration around it.
+inline constexpr const char* kProjExtBanksKey = "banks";
+
+// The retired legacy single-bank key (read once on load to migrate into the pool).
+inline constexpr const char* kProjExtIndexKey = "bank_index";
+
+// The Design-View model key.
+inline constexpr const char* kProjExtViewKey = "view_state";
+
+// The docked panel's tail-setting key.
+inline constexpr const char* kProjExtTailKey = "tail_setting";
+
+// The per-project minted-GUID identity key.
+inline constexpr const char* kProjExtGuidKey = "project_guid";
+
+// The S9 BANK-GENERATION key. The EXTENSION stamps a monotonic decimal counter here that it
+// bumps on every bank-content mutation that changes what a live instance would PLAY (capture
+// add, re-capture-in-place, sample remove, move/copy affecting banks, ingest import). The VST3
+// instrument READS it off the audio thread on a UI-timer cadence and, when the value differs
+// from what it last saw, calls reloadFromBank() so a recapture/ingest refreshes playing
+// instances hands-free (the S9 change-detection trigger). WIRE-SHARED (instrument reads it);
+// the instrument never WRITES it (the extension owns it, same read-only-over-bank rule as the
+// assignment request). Additive to the persist blob — an absent stamp reads as generation 0
+// (a pre-S9 project), and the first bump (>= 1) then reads as a change. FOREVER-STABLE once
+// shipped: changing this spelling resets every already-shipped instance's change-detection
+// baseline (a one-time spurious reload), so it is fixed like every sibling key.
+inline constexpr const char* kProjExtBankGenKey = "bank_generation";
+
+// The S8 ingest ASSIGNMENT-REQUEST key. The EXTENSION writes an assignment request here
+// after an ingest-with-assign (arrange capture / Media-Explorer import / drop-onto-panel):
+// "the active sampler instance should now play THIS sample." The value is the pure
+// assignment_request wire format ("rsassign1" + bankId + sampleId + generation) — see
+// assignment_request.h for the exact grammar. WIRE-SHARED because the VST3 instrument
+// READS it (in a later dispatch, S8 instrument-side follow-up) to update its own selection
+// and reload; the instrument never WRITES it (the extension writing its own namespace does
+// not violate the instrument's read-only-over-the-bank rule). FOREVER-STABLE once shipped:
+// changing this spelling strands any pending request an already-shipped instrument watches.
+inline constexpr const char* kProjExtAssignKey = "assign_request";
+
+}  // namespace reasampler

src/ingest.cpp

@@ -0,0 +1,596 @@
+// ingest.cpp — the S8 "ingest through the bank" shell (extension side). See ingest.h.
+//
+// Compiled into the reaper_reasampler MODULE. Includes reaper_plugin_functions.h WITHOUT
+// REAPERAPI_IMPLEMENT — main.cpp owns the API pointers; here they are extern
+// (CLAUDE.md §contract). REAPER-facing, DAW-verified; the pure serialization it drives
+// (assignment_request) is CTest-tested.
+
+#include "ingest.h"
+
+#include <cstdint>
+#include <cstring>
+#include <ctime>
+#include <filesystem>
+#include <fstream>
+#include <string>
+#include <vector>
+
+#include "actions.h"             // persistBankOp — shared undo-block wrapper (R-B path)
+#include "app_version.h"         // channelCommandId / channelActionName
+#include "assignment_request.h"  // pure (bankId, sampleId, generation) encode
+#include "bank_book.h"           // BankBook, Bank, activeBankId / activeIndex
+#include "bank_model.h"          // Sample, AddResult, findByHash
+#include "bank_panel.h"          // bankPanelRefresh
+#include "capture_paths.h"       // deriveBankPaths / projectDirOfRpp / hashWavContent
+#include "persist.h"             // ReaSamplerSession
+
+#include "wav_trim.h"             // parseWavLayout — 32f-float WAV validator for the fast path
+
+#include "reaper_plugin.h"       // reaper_plugin_info_t, gaccel_register_t (full defs)
+
+#define REAPERAPI_MINIMAL
+#define REAPERAPI_WANT_EnumProjects
+#define REAPERAPI_WANT_ShowConsoleMsg
+#define REAPERAPI_WANT_MediaExplorerGetLastPlayedFileInfo
+#define REAPERAPI_WANT_PCM_Source_CreateFromFile
+#define REAPERAPI_WANT_PCM_Source_Destroy
+#define REAPERAPI_WANT_GetMediaSourceNumChannels
+#define REAPERAPI_WANT_GetMediaSourceSampleRate
+#define REAPERAPI_WANT_GetMediaSourceLength
+#define REAPERAPI_WANT_Undo_BeginBlock2
+#define REAPERAPI_WANT_Undo_EndBlock2
+#include "reaper_plugin_functions.h"
+
+namespace reasampler {
+
+namespace {
+
+// The live session the ingest paths mutate. Set once by ingestRegisterActions and read by
+// every ingest body. Not owned here (main.cpp owns g_session).
+ReaSamplerSession* g_session = nullptr;
+
+// FOREVER-STABLE ingest action-id SUFFIX (Phase V, V4). The channel prefix is prepended at
+// register via channelCommandId; NEVER change a shipped suffix. Only the Media-Explorer
+// import registers here — the arrange capture+assign action lives in the capture family in
+// main.cpp (it reuses the capture render machinery there), and the drop path is a panel
+// callback (ingestDroppedFiles), not a bindable action.
+constexpr const char* kIdImportMediaExplorer = "INGEST_IMPORT_MEDIA_EXPLORER";
+
+int               g_cmdImportMediaExplorer = 0;
+gaccel_register_t g_accelImportMediaExplorer{};
+
+// Durable store of the composed, channel-qualified command-id + label strings. Two scalar
+// std::string globals (one action); their c_str() pointers are handed to REAPER at register
+// and re-presented at unregister, so these strings must not be mutated after registration.
+// Populated once by ingestRegisterActions; stable for the extension lifetime.
+std::string g_idImportStr;
+std::string g_labelImportStr;
+
+// --- Project directory --------------------------------------------------------
+
+// The current project's directory (parent of its .rpp), forward-slashed, no trailing
+// slash — the M4 convention (projectDirOfRpp). Empty for an unsaved/no-active project,
+// which makes the import refuse to place a file (no default-location fallback — the
+// relative-paths invariant). Read-only.
+std::string currentProjectDir() {
+    std::vector<char> buf(4096, '\0');
+    EnumProjects(-1, buf.data(), static_cast<int>(buf.size()));
+    return projectDirOfRpp(std::string(buf.data()));
+}
+
+// Reads a whole file's bytes. Empty vector on any failure (missing / unreadable). Mirror
+// of capture.cpp's readFileBytes — used to read the source and validate/hash the bank copy.
+std::vector<std::uint8_t> readFileBytes(const std::string& path) {
+    std::ifstream f(path, std::ios::binary | std::ios::ate);
+    if (!f) return {};
+    const std::streamsize n = f.tellg();
+    if (n <= 0) return {};
+    std::vector<std::uint8_t> bytes(static_cast<std::size_t>(n));
+    f.seekg(0);
+    f.read(reinterpret_cast<char*>(bytes.data()), n);
+    if (!f) return {};
+    return bytes;
+}
+
+// Writes a byte buffer to a file. Returns true on success. The caller is responsible for
+// ensuring the directory exists before calling.
+bool writeFileBytes(const std::string& path, const std::vector<std::uint8_t>& bytes) {
+    std::ofstream f(path, std::ios::binary | std::ios::trunc);
+    if (!f) return false;
+    f.write(reinterpret_cast<const char*>(bytes.data()),
+            static_cast<std::streamsize>(bytes.size()));
+    return f.good();
+}
+
+// Builds a minimal 32-bit-float RIFF/WAVE byte buffer from interleaved double samples.
+// The output is a canonical WAV the bank and wav_trim can read:
+//   RIFF chunk, WAVE form, fmt chunk (tag 3 = WAVE_FORMAT_IEEE_FLOAT, 16-byte body),
+//   data chunk (interleaved little-endian float32, one float per sample per channel).
+// `nch` channels, `rate` Hz sample rate, `frameCount` frames (total samples = frameCount*nch).
+// Each ReaSample (double) is narrowed to float by assignment — the instrument expects
+// 32-bit float; the reduction is intentional and matches how the bank contract is defined
+// (capture.cpp kRenderFormatWavFloat32; wav_trim.h FORMAT ASSUMPTION).
+std::vector<std::uint8_t> buildFloat32Wav(int nch, std::uint32_t rate,
+                                          std::size_t frameCount,
+                                          const std::vector<ReaSample>& interleaved) {
+    const std::size_t sampleCount     = frameCount * static_cast<std::size_t>(nch);
+    const std::size_t dataBytesCount  = sampleCount * 4u;  // 4 bytes per float32
+
+    // The WAV is: RIFF(4)+size(4)+WAVE(4) = 12, fmt (4)+size(4)+16 body = 24, data (4)+size(4)+payload.
+    // Total = 12 + 24 + 8 + dataBytesCount = 44 + dataBytesCount.
+    const std::uint32_t riffSize =
+        static_cast<std::uint32_t>(36u + dataBytesCount);  // 4("WAVE")+24(fmt chunk)+8(data hdr)+data
+
+    std::vector<std::uint8_t> out;
+    out.reserve(44u + dataBytesCount);
+
+    auto putU16 = [&](std::uint16_t v) {
+        out.push_back(static_cast<std::uint8_t>(v & 0xFF));
+        out.push_back(static_cast<std::uint8_t>((v >> 8) & 0xFF));
+    };
+    auto putU32 = [&](std::uint32_t v) {
+        out.push_back(static_cast<std::uint8_t>(v & 0xFF));
+        out.push_back(static_cast<std::uint8_t>((v >> 8) & 0xFF));
+        out.push_back(static_cast<std::uint8_t>((v >> 16) & 0xFF));
+        out.push_back(static_cast<std::uint8_t>((v >> 24) & 0xFF));
+    };
+    auto putTag = [&](const char* t) {
+        for (int i = 0; i < 4; ++i)
+            out.push_back(static_cast<std::uint8_t>(t[i]));
+    };
+    auto putF32 = [&](float f) {
+        std::uint8_t tmp[4];
+        std::memcpy(tmp, &f, 4);
+        for (int i = 0; i < 4; ++i) out.push_back(tmp[i]);
+    };
+
+    // RIFF header
+    putTag("RIFF");
+    putU32(riffSize);
+    putTag("WAVE");
+
+    // fmt chunk (16-byte body, WAVE_FORMAT_IEEE_FLOAT = 0x0003)
+    putTag("fmt ");
+    putU32(16u);                                // chunk body size
+    putU16(0x0003u);                            // WAVE_FORMAT_IEEE_FLOAT
+    putU16(static_cast<std::uint16_t>(nch));
+    putU32(rate);
+    putU32(rate * static_cast<std::uint32_t>(nch) * 4u);  // avgBytesPerSec
+    putU16(static_cast<std::uint16_t>(nch * 4));           // blockAlign
+    putU16(32u);                                            // bitsPerSample
+
+    // data chunk
+    putTag("data");
+    putU32(static_cast<std::uint32_t>(dataBytesCount));
+    for (std::size_t i = 0; i < sampleCount && i < interleaved.size(); ++i)
+        putF32(static_cast<float>(interleaved[i]));
+
+    return out;
+}
+
+// Decodes ALL samples from `src` into interleaved double-precision frames.
+// Returns empty on a zero-length or silent source (sampleRate < 1, channelCount == 0).
+// Uses GetSamples in blocks; advances time_s monotonically. The caller has already
+// queried channelCount and sampleRate from the same source; those values are passed in
+// to avoid re-querying after GetSamples mutates decoder state.
+std::vector<ReaSample> decodePcmSource(PCM_source* src, int nch, double sampleRate,
+                                       double lengthSeconds) {
+    if (!src || nch <= 0 || sampleRate < 1.0 || lengthSeconds <= 0.0) return {};
+
+    const std::size_t totalFrames =
+        static_cast<std::size_t>(lengthSeconds * sampleRate + 0.5);
+    if (totalFrames == 0) return {};
+
+    std::vector<ReaSample> out;
+    out.reserve(totalFrames * static_cast<std::size_t>(nch));
+
+    // Pull samples in blocks of ~4096 frames; loop until source is exhausted.
+    constexpr int kBlockFrames = 4096;
+    std::vector<ReaSample> block(static_cast<std::size_t>(kBlockFrames * nch));
+
+    PCM_source_transfer_t t{};
+    t.samplerate = sampleRate;
+    t.nch        = nch;
+    t.time_s     = 0.0;
+    t.midi_events = nullptr;
+
+    while (true) {
+        t.samples    = block.data();
+        t.length     = kBlockFrames;
+        t.samples_out = 0;
+        src->GetSamples(&t);
+        if (t.samples_out <= 0) break;
+        const std::size_t got = static_cast<std::size_t>(t.samples_out) *
+                                static_cast<std::size_t>(nch);
+        out.insert(out.end(), block.data(), block.data() + got);
+        t.time_s += static_cast<double>(t.samples_out) / sampleRate;
+    }
+    return out;
+}
+
+// The result of an import-into-bank: the sample id to assign (the existing id on a
+// hash-dedup collapse, the new id otherwise) and whether anything was added to the index
+// (so the caller opens an undo point only for a real mutation).
+struct ImportResult {
+    std::string sampleId;      // "" on failure (nothing to assign)
+    bool        added = false; // true iff a NEW index entry was created (not a collapse)
+    std::string message;       // human-readable outcome for the console
+};
+
+// Imports one OS-native source file into the ACTIVE bank: convert-if-needed to 32-bit-
+// float WAV, write to the project-relative bank folder, index-add, hash-dedup applied.
+//
+// BANK CONTRACT: the instrument (wav_trim) expects every bank file to be a canonical
+// 32-bit-float WAV (WAVE_FORMAT_IEEE_FLOAT, 32 bits). A verbatim copy of a non-WAV (or
+// an integer-PCM or double-float WAV) would be unplayable. This function therefore:
+//   1. Checks whether the source IS already a valid 32f WAV (parseWavLayout fast path).
+//   2. If yes: copies it verbatim — one I/O, content unchanged.
+//   3. If no: decodes via PCM_source::GetSamples and writes a fresh 32f WAV, preserving
+//      the source's channel count and sample rate.
+//
+// DEDUP ORDERING: the content hash is taken from the CONVERTED (bank-format) bytes AFTER
+// building the file buffer but BEFORE writing to disk. This means:
+//   * Re-importing the same source file yields the same converted bytes → same hash →
+//     dedup fires → no redundant disk write (matching the DEDUP-BEFORE-DISK design).
+//   * An imported WAV whose audio-content hash matches a captured WAV also deduplicates
+//     correctly (hashWavContent is chunk-aware for both).
+//   * The pre-conversion hash shortcut (hash the raw source bytes) is not used: a non-WAV
+//     source's bytes would produce a different hash from the converted WAV bytes, so two
+//     imports of the same mp3 would NOT dedup — which is wrong. Hashing post-conversion
+//     is correct.
+//
+// NON-DESTRUCTIVE: the source file is never modified or moved — only read.
+// Records the written file in the owned-file manifest (Phase B B-cap) so Phase R prune can
+// attribute it. Does NOT persist or open an undo point — the caller batches that (a
+// multi-file drop is one undo point, one persist).
+ImportResult importFileIntoActiveBank(const std::string& absoluteSourcePath) {
+    ImportResult out;
+
+    if (absoluteSourcePath.empty()) {
+        out.message = "empty file path";
+        return out;
+    }
+    namespace fs = std::filesystem;
+    std::error_code ec;
+    if (!fs::exists(absoluteSourcePath, ec) || ec) {
+        out.message = "file not found: " + absoluteSourcePath;
+        return out;
+    }
+
+    const std::string projectDir = currentProjectDir();
+    if (projectDir.empty()) {
+        out.message = "no saved project, so the bank has no location -- save the "
+                      "project first";
+        return out;
+    }
+
+    // Read source bytes; needed to check whether it is already a 32f WAV.
+    const std::vector<std::uint8_t> srcBytes = readFileBytes(absoluteSourcePath);
+    if (srcBytes.empty()) {
+        out.message = "file is empty or unreadable: " + absoluteSourcePath;
+        return out;
+    }
+
+    // Probe the source's audio geometry via PCM_source. Needed for conversion AND for
+    // populating the Sample's metadata. A file REAPER cannot open leaves geometry at
+    // zero — the sample still imports if the WAV-fast-path succeeds; the geometry
+    // is simply unknown, the honest default.
+    int    channelCount  = 0;
+    int    sampleRate    = 0;
+    double lengthSeconds = 0.0;
+    PCM_source* srcHandle = PCM_Source_CreateFromFile(absoluteSourcePath.c_str());
+    if (srcHandle) {
+        channelCount  = GetMediaSourceNumChannels(srcHandle);
+        sampleRate    = GetMediaSourceSampleRate(srcHandle);
+        bool isQN = false;
+        lengthSeconds = GetMediaSourceLength(srcHandle, &isQN);
+        if (isQN) lengthSeconds = 0.0;  // QN-length source has no seconds length to store
+    }
+
+    // Determine whether a verbatim copy suffices (fast path) or a conversion is needed.
+    // parseWavLayout validates that the source is a canonical 32-bit-float RIFF/WAVE; any
+    // other format (mp3, aiff, integer PCM, 16-bit WAV, etc.) takes the decode+rewrite path.
+    const WavLayout layout = parseWavLayout(srcBytes);
+    const bool isFloat32Wav = layout.valid;
+
+    // Build the bank-format bytes in memory (the "converted" bytes), which we hash for dedup
+    // BEFORE writing to disk so a re-import of the same source skips the disk write.
+    std::vector<std::uint8_t> bankBytes;
+    if (isFloat32Wav) {
+        // Fast path: already canonical — bank bytes ARE the source bytes.
+        bankBytes = srcBytes;
+        if (srcHandle) PCM_Source_Destroy(srcHandle);
+    } else {
+        // Conversion path: decode all samples then write a fresh 32f WAV.
+        // PCM_source is opened on the source path (not a copy); we already have srcHandle.
+        std::vector<ReaSample> decoded;
+        if (srcHandle && channelCount > 0 && sampleRate > 0 && lengthSeconds > 0.0) {
+            decoded = decodePcmSource(srcHandle, channelCount,
+                                      static_cast<double>(sampleRate), lengthSeconds);
+        }
+        if (srcHandle) PCM_Source_Destroy(srcHandle);
+
+        if (decoded.empty()) {
+            // No decodable audio. The source is on disk (valid path, REAPER could open it)
+            // but yielded no samples — e.g. a MIDI file, a zero-length audio file, or a
+            // format REAPER does not support. Fail loudly: we must not write a silent WAV
+            // and pretend the import succeeded.
+            out.message = "could not decode audio samples from: " +
+                          fs::path(absoluteSourcePath).filename().string() +
+                          " (unsupported format or no audio data)";
+            return out;
+        }
+
+        const std::size_t frameCount =
+            decoded.size() / static_cast<std::size_t>(channelCount > 0 ? channelCount : 1);
+        bankBytes = buildFloat32Wav(channelCount,
+                                   static_cast<std::uint32_t>(sampleRate),
+                                   frameCount, decoded);
+    }
+    // srcHandle is destroyed above in both branches.
+
+    // Hash the converted (bank-format) bytes for dedup. WAV-aware hash (hashWavContent)
+    // so a re-import of the same source deduplicates against a previously-captured or
+    // previously-imported sample with identical audio content, even if non-audio RIFF
+    // chunks differ. Empty hash (unhashable) is treated as "not dedupable" (safe direction:
+    // copies + adds rather than silently collapsing onto an unrelated entry).
+    const std::string contentHash = hashWavContent(bankBytes);
+
+    BankBook& book = g_session->book();
+
+    // Dedup-before-disk: if the active bank already holds this audio content, assign the
+    // existing sample's id and skip the disk write (no redundant on-disk duplicate).
+    // Empty hashes never match (findByHash treats "" as non-participating).
+    if (!contentHash.empty()) {
+        if (const Sample* existing = book.activeIndex().findByHash(contentHash)) {
+            out.sampleId = existing->id;
+            out.added    = false;  // already present — no index mutation, no undo point
+            out.message  = "already in the active bank (assigned existing sample)";
+            return out;
+        }
+    }
+
+    // Derive the destination path. The stem comes from the source file name; a timestamp
+    // uniqueTag avoids collision with a prior import of a same-named file.
+    const std::string sourceStem = fs::path(absoluteSourcePath).stem().string();
+    const std::int64_t nowSec = static_cast<std::int64_t>(std::time(nullptr));
+    const std::string uniqueTag = std::to_string(nowSec);
+    const BankPaths paths = deriveBankPaths(projectDir, sourceStem, uniqueTag);
+
+    // Ensure the bank folder exists, then write the (converted) bank bytes.
+    fs::create_directories(paths.absoluteDir, ec);  // idempotent; ec ignored (write reports)
+    const std::string destPath = paths.absoluteDir + "/" + paths.fileName;
+    if (!writeFileBytes(destPath, bankBytes)) {
+        out.message = "could not write converted file to the bank folder";
+        return out;
+    }
+
+    // Build the Sample. Import is NOT a capture — sourceMode/range/tail do not apply; we
+    // record what we know (path, hash, geometry, name) and leave capture-only fields at
+    // their defaults. rootNote/loop stay empty: an imported file is not a single played
+    // note, so we do not guess a root note.
+    Sample s;
+    s.id            = "imp-" + uniqueTag + "-" + paths.fileName;
+    s.displayName   = sourceStem.empty() ? std::string("import") : sourceStem;
+    s.relativePath  = paths.relativePath;  // project-relative (invariant)
+    s.channelCount  = channelCount;
+    s.sampleRate    = sampleRate;
+    s.lengthSeconds = lengthSeconds;
+    s.tier          = Tier::Scratch;       // imports land in scratch, like captures
+    s.contentHash   = contentHash;
+    s.createdTimestamp = nowSec;
+
+    const AddResult r = book.activeIndex().add(s);
+    // Record the written file as owned regardless of the add outcome — the tool WROTE it, so
+    // Phase R prune must attribute it. (A Collapsed result here would mean another sample in
+    // the active bank matched the hash after we passed the pre-write dedup check — a narrow
+    // race window. Record + handle both honestly.)
+    g_session->owned().add(paths.relativePath);
+
+    switch (r) {
+        case AddResult::Added:
+            out.sampleId = s.id;
+            out.added    = true;
+            out.message  = (isFloat32Wav ? "imported -> " : "converted + imported -> ") +
+                           paths.relativePath;
+            break;
+        case AddResult::Collapsed: {
+            // The hash matched an existing entry (a race against our pre-write dedup check,
+            // or an empty-hash edge). Assign the existing entry's id.
+            const Sample* existing =
+                contentHash.empty() ? nullptr : book.activeIndex().findByHash(contentHash);
+            out.sampleId = existing ? existing->id : std::string{};
+            out.added    = false;
+            out.message  = "collapsed onto an existing bank sample";
+            break;
+        }
+        case AddResult::RejectedAbsolutePath:
+        case AddResult::RejectedEmptyId:
+            // deriveBankPaths always yields a relative path and a non-empty id above, so
+            // these are unreachable in practice — reported honestly rather than silently.
+            out.message = "index rejected the import (internal path/id error)";
+            break;
+    }
+    return out;
+}
+
+// --- Media-Explorer import action --------------------------------------------
+
+// Import the Media Explorer's current last-played/selected file into the active bank and
+// assign it to the active instance (S8 surface 2). Single-file, pull-on-action:
+// MediaExplorerGetLastPlayedFileInfo returns the ONE last-played file (the whole ME
+// contract — no enumerate-selected API). The selection RANGE it reports is deliberately
+// IGNORED here: an import brings the whole file into the bank (the range is a preview
+// hint, and the fields are [0,1] fractions, not seconds — see the DAW-verify note); a
+// user wanting a sub-range captures it via the arrange path instead. Undo-wrapped.
+void doImportFromMediaExplorer() {
+    // filemode/sel/pitch/vol/rate/bpm/extrainfo are read but only the filename is used for
+    // the import. selstart/selend are [0,1] fractions (SDK header) — a preview hint, not a
+    // bank-relevant range; left unused. extrainfo is documented "currently unused".
+    std::vector<char> nameBuf(4096, '\0');
+    int    filemode = 0;
+    double selStart = 0.0, selEnd = 0.0;
+    double pitch = 0.0, vol = 0.0, rate = 0.0, srcbpm = 0.0;
+    std::vector<char> extra(256, '\0');  // documented unused; sized generously to be safe
+    const bool ok = MediaExplorerGetLastPlayedFileInfo(
+        nameBuf.data(), static_cast<int>(nameBuf.size()), &filemode, &selStart, &selEnd,
+        &pitch, &vol, &rate, &srcbpm, extra.data(), static_cast<int>(extra.size()));
+
+    const std::string path(nameBuf.data());
+    if (!ok || path.empty()) {
+        ShowConsoleMsg("ReaSampler ingest: no Media Explorer file to import -- open the "
+                       "Media Explorer and select (or preview) a file first.\n");
+        return;
+    }
+
+    const ImportResult r = importFileIntoActiveBank(path);
+    if (r.sampleId.empty()) {
+        ShowConsoleMsg(("ReaSampler ingest: Media Explorer import failed -- " + r.message +
+                        ".\n").c_str());
+        return;
+    }
+
+    // Persist the bank add AND the assign request inside ONE undo block so Ctrl-Z rolls
+    // back both keys atomically: undo restores `banks` (removing the new sample) AND
+    // clears the `assign_request` that named it, so no stale request can survive.
+    // The block is opened only when the index mutated (a dedup collapse changed nothing).
+    // If saveToActiveProject() no-ops (unsaved project), we close with an empty label +
+    // zero flag so REAPER discards the undo entry (the house pattern from actions.cpp).
+    if (r.added) {
+        Undo_BeginBlock2(nullptr);
+        // S9: an ingest import adds a sample to the active bank -> bump inside the block so
+        // the stamped generation refreshes the assigned instance hands-free (and undo rolls
+        // the generation back with the banks/assign_request keys).
+        g_session->bumpBankGeneration();
+        const bool persisted = g_session->saveToActiveProject();
+        // Assign request inside the same block: undo rolls back both keys together.
+        ingestAssignActiveInstance(g_session->book().activeBankId(), r.sampleId);
+        if (persisted)
+            Undo_EndBlock2(nullptr, "ReaSampler: import from Media Explorer",
+                           UNDO_STATE_MISCCFG);
+        else
+            Undo_EndBlock2(nullptr, "", 0);
+    } else {
+        // Dedup collapse: index unchanged, no undo point. Assign request still written
+        // (the user explicitly re-imported; they want the instance updated).
+        ingestAssignActiveInstance(g_session->book().activeBankId(), r.sampleId);
+    }
+    bankPanelRefresh();
+    ShowConsoleMsg(("ReaSampler ingest: " + r.message + " (assigned to the active "
+                    "instance).\n").c_str());
+}
+
+}  // namespace
+
+// --- Assignment-request write ------------------------------------------------
+
+void ingestAssignActiveInstance(const std::string& bankId, const std::string& sampleId) {
+    if (!g_session || sampleId.empty()) return;  // nothing to assign
+
+    AssignmentRequest req;
+    req.bankId     = bankId;
+    req.sampleId   = sampleId;
+    // Monotonic disambiguator: a wall-clock unix-epoch stamp so the reader tells a fresh
+    // assign (even re-assigning the SAME id) from a stale value. NOT the S9 bank-generation
+    // counter (a separate point) — this field is self-contained to the request.
+    req.generation = static_cast<std::int64_t>(std::time(nullptr));
+
+    g_session->writeAssignmentRequest(encodeAssignmentRequest(req));
+}
+
+// --- Drop-onto-panel ingest --------------------------------------------------
+
+void ingestDroppedFiles(const std::vector<std::string>& absolutePaths) {
+    if (!g_session || absolutePaths.empty()) return;
+
+    // Import ALL dropped files; assign the FIRST successfully-imported one (documented
+    // multi-file policy). Batch the persist + undo point: many imports are ONE undo entry.
+    std::string firstAssignId;
+    std::string firstAssignBank;
+    int importedNew = 0;
+    int importedTotal = 0;  // includes dedup collapses that still yielded an id to assign
+    std::string lastFailure;
+
+    for (const std::string& path : absolutePaths) {
+        const ImportResult r = importFileIntoActiveBank(path);
+        if (r.sampleId.empty()) {
+            lastFailure = r.message;
+            continue;
+        }
+        ++importedTotal;
+        if (r.added) ++importedNew;
+        if (firstAssignId.empty()) {
+            firstAssignId   = r.sampleId;
+            firstAssignBank = g_session->book().activeBankId();
+        }
+    }
+
+    // One undo point for the whole drop, opened only if a NEW index entry was created (a
+    // drop that only re-hit existing content mutated nothing on the index). The assign
+    // request is written INSIDE the same block so Ctrl-Z rolls back both keys together:
+    // undo restores `banks` (removing the new samples) AND clears the `assign_request` that
+    // named one of them, so no stale request survives pointing to a removed sample.
+    // If saveToActiveProject() no-ops (unsaved project), we close with an empty label + zero
+    // flag so REAPER discards the undo entry (house pattern from actions.cpp).
+    if (!firstAssignId.empty()) {
+        if (importedNew > 0) {
+            Undo_BeginBlock2(nullptr);
+            // S9: one coalesced bump for the whole drop (>=1 new sample landed) inside the
+            // block so the generation refreshes the assigned instance and undo rolls it back.
+            g_session->bumpBankGeneration();
+            const bool persisted = g_session->saveToActiveProject();
+            // Assign inside the block: undo restores both keys atomically.
+            ingestAssignActiveInstance(firstAssignBank, firstAssignId);
+            if (persisted)
+                Undo_EndBlock2(nullptr, "ReaSampler: import dropped file(s)",
+                               UNDO_STATE_MISCCFG);
+            else
+                Undo_EndBlock2(nullptr, "", 0);
+        } else {
+            // All dropped files deduplicated: index unchanged, no undo point needed. Still
+            // assign so the user sees the sample is already in the bank.
+            ingestAssignActiveInstance(firstAssignBank, firstAssignId);
+        }
+        bankPanelRefresh();
+        const std::string msg =
+            "ReaSampler ingest: imported " + std::to_string(importedTotal) +
+            (importedTotal == 1 ? " file" : " files") +
+            " and assigned the first to the active instance.\n";
+        ShowConsoleMsg(msg.c_str());
+    } else {
+        ShowConsoleMsg(("ReaSampler ingest: nothing imported from the drop -- " +
+                        (lastFailure.empty() ? std::string("no usable files") : lastFailure) +
+                        ".\n").c_str());
+    }
+}
+
+// --- Action registration ------------------------------------------------------
+
+void ingestRegisterActions(reaper_plugin_info_t* rec, ReaSamplerSession* session) {
+    g_session = session;  // shared with the capture / bank / Design-View families
+
+    g_idImportStr = channelCommandId(kIdImportMediaExplorer);
+    g_cmdImportMediaExplorer = rec->Register("command_id", (void*)g_idImportStr.c_str());
+    if (g_cmdImportMediaExplorer) {
+        g_labelImportStr = channelActionName("import Media Explorer file into bank + assign");
+        g_accelImportMediaExplorer.accel.cmd = g_cmdImportMediaExplorer;
+        g_accelImportMediaExplorer.desc      = g_labelImportStr.c_str();
+        rec->Register("gaccel", (void*)&g_accelImportMediaExplorer);
+    }
+}
+
+bool ingestHandleCommand(int command) {
+    if (command == 0 || !g_session) return false;
+    if (command == g_cmdImportMediaExplorer) { doImportFromMediaExplorer(); return true; }
+    return false;  // not ours — caller's hookcommand keeps looking
+}
+
+void ingestUnregisterActions(reaper_plugin_info_t* rec) {
+    // Mirror-unregister with '-'-prefixed strings; the '-command_id' re-presents the SAME
+    // interned channel-qualified id used at register (g_idImportStr).
+    rec->Register("-gaccel", (void*)&g_accelImportMediaExplorer);
+    rec->Register("-command_id", (void*)g_idImportStr.c_str());
+    g_session = nullptr;
+}
+
+}  // namespace reasampler

src/ingest.h

@@ -0,0 +1,77 @@
+#pragma once
+// ingest — the S8 "ingest through the bank" shell (EXTENSION side).
+//
+// Compiled into the reaper_reasampler MODULE. REAPER-facing (PCM_Source metadata reads,
+// Media-Explorer query, ext-state assignment write, action registration), so it is
+// DAW-verified, not unit-tested; the pure serialization it drives lives in
+// assignment_request (tested in CTest).
+//
+// -- The one gesture (CONTEXT.md §Ingest through the bank) --------------------
+//
+// Loading a sample into the sampler is ONE gesture: capture/import-into-bank AND
+// auto-assign to the active sampler instance. The EXTENSION owns ingest (it has arrange
+// access, Media-Explorer access, and the drop-target surface on its own panels); the
+// instrument stays a READ-ONLY bank consumer. Three ingest surfaces:
+//
+//   1. Arrange capture -> bank -> assign   (a bindable action; reuses the capture path).
+//   2. Media-Explorer import -> bank -> assign (a bindable action; single-file, pull-on-
+//      action via MediaExplorerGetLastPlayedFileInfo).
+//   3. Drop-onto-panel -> bank -> assign   (an OS file drop on the docked bank_panel HWND;
+//      multi-file: import all, assign the first).
+//
+// -- The load-bearing principle (restated) -----------------------------------
+//
+// Ingest NEVER inserts a timeline item. Capture writes a file + an index entry; import
+// copies a file + adds an index entry; assignment is a bank-index + instance-selection
+// act, not a placement. Any path here that calls InsertMedia would be a bug.
+//
+// -- Import semantics ---------------------------------------------------------
+//
+// A Media-Explorer/drop import is a FILE COPY into the project-relative bank folder +
+// an index add, mirroring how a capture lands (relative-paths-only, hash-dedup). If the
+// active bank already holds the imported content (by content hash), the import collapses
+// onto the existing sample and assigns THAT sample's id — no redundant on-disk copy.
+
+#include <string>
+#include <vector>
+
+// Forward declarations keep this header REAPER-free at its own boundary (the .cpp pulls
+// the SDK). reaper_plugin_info_t is REAPER's dispatch struct; ReaSamplerSession owns the
+// book + persist bridge the ingest paths mutate.
+struct reaper_plugin_info_t;
+
+namespace reasampler {
+
+class ReaSamplerSession;
+
+// Registers the S8 ingest action family (command_id/gaccel per the house contract),
+// mirror of bankRegisterActions. `session` is the live session the ingest paths mutate
+// (shared with the capture / bank / Design-View families). The single hookcommand in
+// main.cpp routes fired ids here via ingestHandleCommand.
+void ingestRegisterActions(reaper_plugin_info_t* rec, ReaSamplerSession* session);
+
+// Routes a fired command id to its ingest action. Returns true iff it was one of ours
+// (claim-only, per the hookcommand contract); false otherwise so the hook keeps looking.
+bool ingestHandleCommand(int command);
+
+// Mirror-unregisters the ingest action family on unload (the '-'-prefixed strings).
+void ingestUnregisterActions(reaper_plugin_info_t* rec);
+
+// Write the S8 assignment request for a just-ingested sample: "the active sampler
+// instance should now play (bankId, sampleId)." Encodes the pure assignment_request value
+// (with a fresh monotonic generation stamp) and routes it to ext state via the session.
+// Called by EVERY ingest surface after the sample lands in the bank — the arrange
+// capture+assign action (main.cpp, alongside the capture machinery it reuses), the ME
+// import action, and the drop path. A no-op-safe write: if there is no saved/active
+// project the request is silently dropped (nothing to signal into), matching the
+// book/manifest quiet-persist idiom. `sampleId` empty -> no write (nothing to assign).
+void ingestAssignActiveInstance(const std::string& bankId, const std::string& sampleId);
+
+// Ingest OS-dropped files onto a ReaSampler surface (S8 drop path). Called by the
+// bank_panel's WM_DROPFILES handler with the dropped file paths (absolute, OS-native).
+// Imports EVERY file into the active bank (copy + index add, hash-dedup) and assigns the
+// FIRST successfully-imported sample to the active instance. A no-op on an empty list or
+// an unsaved/no-active project (nothing to import into). Reports outcomes to the console.
+void ingestDroppedFiles(const std::vector<std::string>& absolutePaths);
+
+}  // namespace reasampler

src/instrument_drop.cpp

@@ -0,0 +1,108 @@
+// instrument_drop — pure implementation. See instrument_drop.h.
+// NO REAPER / SWELL / VST3 SDK / vendor. Reuses sample_map's ComponentState serializer.
+
+#include "instrument_drop.h"
+
+#include "vst/sample_map.h"  // ComponentState + serializeComponentState (the SHARED writer)
+
+namespace reasampler {
+
+namespace {
+
+constexpr char kB64Alphabet[] =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+// -1 = not a base64 char; index by unsigned byte. Built once.
+int b64Value(unsigned char c) {
+    if (c >= 'A' && c <= 'Z') return c - 'A';
+    if (c >= 'a' && c <= 'z') return c - 'a' + 26;
+    if (c >= '0' && c <= '9') return c - '0' + 52;
+    if (c == '+') return 62;
+    if (c == '/') return 63;
+    return -1;
+}
+
+}  // namespace
+
+std::vector<std::uint8_t> instrumentDropStateBytes(const std::string& sampleId) {
+    // The ONE fact the drop carries: this capture is the instance's selection. Everything
+    // else stays at the fresh-instance defaults (no zones, mono, generation 0) — the same
+    // ComponentState a browser click would produce. serializeComponentState is the
+    // instrument's own writer (the single source of truth for the byte layout), so this is
+    // NOT a parallel encoder — it IS the instrument's encoder.
+    ComponentState cs;
+    cs.selectionId = sampleId;
+    return serializeComponentState(cs);
+}
+
+std::string buildInstrumentDropChunk(const std::string& sampleId) {
+    return encodeBase64(instrumentDropStateBytes(sampleId));
+}
+
+std::string encodeBase64(const std::vector<std::uint8_t>& bytes) {
+    std::string out;
+    out.reserve(((bytes.size() + 2) / 3) * 4);
+    std::size_t i = 0;
+    const std::size_t n = bytes.size();
+    while (i + 3 <= n) {
+        const std::uint32_t triple = (static_cast<std::uint32_t>(bytes[i]) << 16) |
+                                     (static_cast<std::uint32_t>(bytes[i + 1]) << 8) |
+                                     static_cast<std::uint32_t>(bytes[i + 2]);
+        out.push_back(kB64Alphabet[(triple >> 18) & 0x3F]);
+        out.push_back(kB64Alphabet[(triple >> 12) & 0x3F]);
+        out.push_back(kB64Alphabet[(triple >> 6) & 0x3F]);
+        out.push_back(kB64Alphabet[triple & 0x3F]);
+        i += 3;
+    }
+    const std::size_t rem = n - i;
+    if (rem == 1) {
+        const std::uint32_t triple = static_cast<std::uint32_t>(bytes[i]) << 16;
+        out.push_back(kB64Alphabet[(triple >> 18) & 0x3F]);
+        out.push_back(kB64Alphabet[(triple >> 12) & 0x3F]);
+        out.push_back('=');
+        out.push_back('=');
+    } else if (rem == 2) {
+        const std::uint32_t triple = (static_cast<std::uint32_t>(bytes[i]) << 16) |
+                                     (static_cast<std::uint32_t>(bytes[i + 1]) << 8);
+        out.push_back(kB64Alphabet[(triple >> 18) & 0x3F]);
+        out.push_back(kB64Alphabet[(triple >> 12) & 0x3F]);
+        out.push_back(kB64Alphabet[(triple >> 6) & 0x3F]);
+        out.push_back('=');
+    }
+    return out;
+}
+
+std::vector<std::uint8_t> decodeBase64(const std::string& b64) {
+    std::vector<std::uint8_t> out;
+    if (b64.size() % 4 != 0) return out;  // malformed length -> empty (never throws)
+    out.reserve((b64.size() / 4) * 3);
+    for (std::size_t i = 0; i < b64.size(); i += 4) {
+        const char c0 = b64[i], c1 = b64[i + 1], c2 = b64[i + 2], c3 = b64[i + 3];
+        const int v0 = b64Value(static_cast<unsigned char>(c0));
+        const int v1 = b64Value(static_cast<unsigned char>(c1));
+        if (v0 < 0 || v1 < 0) return {};  // illegal char in a non-pad position -> empty
+        // Padding is only legal in the last two positions of the last quad.
+        const bool pad2 = (c2 == '=');
+        const bool pad3 = (c3 == '=');
+        if ((pad2 || pad3) && i + 4 != b64.size()) return {};  // pad before the final quad
+        if (pad2 && !pad3) return {};                          // "=X" is malformed
+        std::uint32_t triple = (static_cast<std::uint32_t>(v0) << 18) |
+                               (static_cast<std::uint32_t>(v1) << 12);
+        out.push_back(static_cast<std::uint8_t>((triple >> 16) & 0xFF));
+        if (!pad2) {
+            const int v2 = b64Value(static_cast<unsigned char>(c2));
+            if (v2 < 0) return {};
+            triple |= static_cast<std::uint32_t>(v2) << 6;
+            out.push_back(static_cast<std::uint8_t>((triple >> 8) & 0xFF));
+            if (!pad3) {
+                const int v3 = b64Value(static_cast<unsigned char>(c3));
+                if (v3 < 0) return {};
+                triple |= static_cast<std::uint32_t>(v3);
+                out.push_back(static_cast<std::uint8_t>(triple & 0xFF));
+            }
+        }
+    }
+    return out;
+}
+
+}  // namespace reasampler

src/instrument_drop.h

@@ -0,0 +1,65 @@
+#pragma once
+// instrument_drop — the PURE blob-construction core of S17 drop-and-load.
+//
+// PURE MODULE (CLAUDE.md §load-bearing split): NO REAPER types, NO SWELL, NO VST3 SDK,
+// NO vendor/ includes. Standard library only (+ the pure sample_map it reuses). Unit-tested
+// outside the DAW — the same "small pure builder + round-trip proof" pattern as
+// assignment_request / provenance.
+//
+// -- What it is (the S17 seam, extension side) --------------------------------
+//
+// S17 drops a bank capture onto a track's FX button, which instantiates ReaSampler 9000 on
+// that track ALREADY PLAYING that capture. The SETTLED mechanism (PLAN.md §S17, mechanism
+// (B) — VST3 component-state injection) is: after TrackFX_AddByName creates the instance, the
+// extension writes the instance's component state directly via
+//   TrackFX_SetNamedConfigParm(track, fx, "vst_chunk", <base64 blob>)
+// with the dragged capture PRE-SELECTED.
+//
+// LOAD-BEARING CAVEAT (PLAN.md §S17): "vst_chunk" is the plugin's OWN base64-encoded
+// serialized chunk — the exact bytes ReaSampler 9000's setState/getState round-trips — NOT a
+// neutral representation REAPER re-marshals. So the extension must construct EXACTLY the
+// instrument's own state-blob bytes. This module does that WITHOUT hand-rolling a parallel
+// byte writer: it calls the instrument's OWN serializer, sample_map::serializeComponentState
+// (the single source of truth for the byte layout — the same function the processor's
+// getState calls), then base64-encodes the result. The shared-writer requirement (both
+// artifacts live in this repo → reuse the exact same code) is satisfied structurally: if the
+// instrument's format changes, this module changes with it because it CALLS it.
+//
+// The base64 encoding is what REAPER's vst_chunk write-parm documents it accepts (see
+// reaper_plugin_functions.h: "vst_chunk[_program] : base64-encoded VST-specific chunk").
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace reasampler {
+
+// Build the base64 blob the extension writes to TrackFX_SetNamedConfigParm(..., "vst_chunk").
+// `sampleId` is the dragged capture's stable bank id — the ONLY thing the drop pre-selects.
+// The resulting ComponentState is the instrument's default face with just this one capture
+// picked: {selectionId = sampleId, no zones, mono, lastConsumedAssignGeneration = 0} — exactly
+// what a fresh instance would hold after the user clicked that capture in the browser. The
+// keymap builds under the product defaults (Gate + Preserve) from the bank's own S2 intrinsics,
+// so the sample plays MIDI-triggered immediately (the S17 "loaded, selected, playable" verify).
+//
+// An EMPTY sampleId yields the empty-state blob ({"", no zones}) — a drop of nothing selects
+// nothing (the S10 silent empty state); the shell guards against this upstream, but the pure
+// contract is defined.
+//
+// Deterministic: the same sampleId always yields the same blob (base64 of the same bytes).
+std::string buildInstrumentDropChunk(const std::string& sampleId);
+
+// The raw (pre-base64) component-state bytes — exposed so the round-trip test can decode them
+// back through the instrument's OWN reader (sample_map::deserializeComponentState) and assert
+// the capture is selected, proving buildInstrumentDropChunk feeds the instrument exactly what
+// its setState expects. Not called by the shell (which uses the base64 form).
+std::vector<std::uint8_t> instrumentDropStateBytes(const std::string& sampleId);
+
+// Standard base64 encode/decode (RFC 4648, '+' '/' alphabet, '=' padding). Exposed so the
+// round-trip test can decode buildInstrumentDropChunk's output. decodeBase64 returns the
+// decoded bytes; on malformed input (bad length / illegal char) it returns an EMPTY vector
+// (never throws) — the test asserts a clean decode, and the shell never decodes.
+std::string encodeBase64(const std::vector<std::uint8_t>& bytes);
+std::vector<std::uint8_t> decodeBase64(const std::string& b64);
+
+}  // namespace reasampler

src/instrument_drop_win.cpp

@@ -0,0 +1,90 @@
+// instrument_drop_win — the REAPER shell for S17 drop-and-load. See instrument_drop_win.h.
+//
+// Compiled into the reaper_reasampler MODULE. Includes reaper_plugin_functions.h WITHOUT
+// REAPERAPI_IMPLEMENT (main.cpp owns the pointers; here they are extern via the WANT list).
+
+#include "instrument_drop_win.h"
+
+#include <cstring>
+#include <string>
+
+#include "app_version.h"  // vstPluginName() — the CHANNEL-correct FX name (stable/beta pairing)
+
+#include "reaper_plugin.h"
+
+#define REAPERAPI_MINIMAL
+#define REAPERAPI_WANT_GetThingFromPoint
+#define REAPERAPI_WANT_TrackFX_AddByName
+#define REAPERAPI_WANT_TrackFX_Delete
+#define REAPERAPI_WANT_TrackFX_SetNamedConfigParm
+#define REAPERAPI_WANT_Undo_BeginBlock2
+#define REAPERAPI_WANT_Undo_EndBlock2
+#include "reaper_plugin_functions.h"
+
+namespace reasampler {
+
+namespace {
+
+// GetThingFromPoint's info string prefixes (verified against reaper_plugin_functions.h:
+// "Updates infoOut with information such as 'arrange', 'fx_chain', 'fx_0' ... If a track
+// panel is hit, string will begin with 'tcp' or 'mcp' or 'tcp.mute' etc"). The FX region
+// reports "fx_chain" (the FX list area) or "fx_N" (a specific FX button). We treat either
+// as the FX hotspot — the S17 drop target.
+bool infoNamesFxHotspot(const char* info) {
+    return std::strncmp(info, "fx_", 3) == 0;
+}
+
+}  // namespace
+
+FxDropTarget resolveFxDropTarget(int screenX, int screenY) {
+    FxDropTarget out;
+    char info[256] = {0};
+    // GetThingFromPoint returns the track under the point (may be null for a non-track thing)
+    // and fills `info` with what was hit. A non-empty info OR a non-null track means the point
+    // is over REAPER's own UI; a null track with an empty info means the pointer has left
+    // REAPER entirely (over another app / the desktop) — the OsDrag boundary.
+    MediaTrack* track = GetThingFromPoint(screenX, screenY, info, sizeof(info));
+    out.track = track;
+    out.overReaperUi = (track != nullptr) || (info[0] != '\0');
+    out.overFxHotspot = (track != nullptr) && infoNamesFxHotspot(info);
+    return out;
+}
+
+bool performInstrumentDrop(MediaTrack* track, const std::string& chunkBase64) {
+    if (!track || chunkBase64.empty()) return false;
+
+    // The CHANNEL-correct FX name: "VST3:ReaSampler 9000" on stable, "VST3:ReaSampler 9000
+    // beta" on beta. Sourcing it from app_version::vstPluginName() (the same accessor the VST
+    // factory display name derives from) keeps the pairing invariant intact — a beta extension
+    // drops the beta VST, a stable extension the stable VST — with no literal to drift.
+    const std::string fxName = "VST3:" + vstPluginName();
+
+    // One undo point for the whole gesture (mirrors the bank-verb undo discipline). Both the
+    // FX add and the state write are REAPER-undoable, so Ctrl-Z removes the instance cleanly.
+    Undo_BeginBlock2(nullptr);
+
+    // Negative `instantiate` => always create a NEW instance (verified in the header). recFX
+    // = false: a normal track FX chain instance, not a record/monitoring FX.
+    const int fxIndex = TrackFX_AddByName(track, fxName.c_str(), /*recFX=*/false,
+                                          /*instantiate=*/-1);
+    bool ok = false;
+    if (fxIndex >= 0) {
+        // Inject the instrument's OWN component-state blob (the dragged capture pre-selected)
+        // via the documented vst_chunk write-parm. The blob was built by the shared writer
+        // (instrument_drop::buildInstrumentDropChunk -> sample_map::serializeComponentState),
+        // so these bytes are exactly what ReaSampler 9000's setState accepts.
+        ok = TrackFX_SetNamedConfigParm(track, fxIndex, "vst_chunk", chunkBase64.c_str());
+        if (!ok) {
+            // All-or-nothing: if the chunk write fails, remove the empty FX instance we just
+            // added so the track is left exactly as it was. TrackFX_Delete signature (verified
+            // in reaper_plugin_functions.h:7236): bool TrackFX_Delete(MediaTrack*, int fx).
+            TrackFX_Delete(track, fxIndex);
+        }
+    }
+
+    // The undo label reflects the placement-of-the-player framing (not a capture, not an insert).
+    Undo_EndBlock2(nullptr, "ReaSampler: drop capture onto FX chain", -1);
+    return ok;
+}
+
+}  // namespace reasampler

src/instrument_drop_win.h

@@ -0,0 +1,57 @@
+#pragma once
+// instrument_drop_win — the REAPER-facing shell half of S17 drop-and-load. The pure gesture
+// decision lives in drag_out (DragGesture::InstrumentDrop) and the pure blob construction in
+// instrument_drop; THIS is the platform shell that (a) resolves a screen point to a track +
+// its TCP FX-button hotspot via REAPER's hit-test API, and (b) on release adds a ReaSampler
+// 9000 instance to that track and injects the dragged capture as its component state.
+//
+// Compiled into the reaper_reasampler MODULE. REAPER-facing (GetThingFromPoint, TrackFX_*,
+// Undo_*), so DAW-verified, not unit-tested; the pure decision + blob it drives are CTest'd.
+//
+// LOAD-BEARING (CONTEXT.md §Drop-and-load): this is an EXPLICIT user placement-of-the-player
+// gesture — it adds a READER of the bank on a track and points it at one already-captured
+// sample. It NEVER captures, NEVER writes the bank, and NEVER inserts a timeline item. The
+// only writes are: a new FX instance on the target track + that instance's own component
+// state — both REAPER-undoable, wrapped in one undo block so the whole gesture is one Ctrl-Z.
+
+#include <string>
+
+// Opaque REAPER track handle at the boundary so includers don't need the SDK. The SDK
+// declares it as a class (reaper_plugin.h) — match that spelling so the mangled name agrees.
+class MediaTrack;
+
+namespace reasampler {
+
+// The result of hit-testing a screen point during a live InstrumentDrop drag.
+struct FxDropTarget {
+    MediaTrack* track = nullptr;  // the track under the pointer (null if none / not a track)
+    bool overReaperUi = false;    // the point is over REAPER's own window/UI at all
+    bool overFxHotspot = false;   // specifically over this track's TCP FX-button/-chain region
+
+    // A valid drop target: a resolved track whose FX hotspot is under the pointer.
+    bool valid() const { return track != nullptr && overFxHotspot; }
+};
+
+// Hit-test a screen point (REAPER screen coords) to an FX drop target. Wraps
+// GetThingFromPoint, whose info string tells us what was hit ("tcp"/"mcp" for a track panel,
+// "fx_chain"/"fx_N" for the FX area/button). `overReaperUi` is the shell-supplied predicate
+// the pure drag_out::decideGesture consumes (true when the point is over REAPER's own UI —
+// i.e. GetThingFromPoint returned a track OR a recognizable non-track thing, false when the
+// pointer has left REAPER entirely). `overFxHotspot` is true when the info string names the
+// FX region specifically — the S17 "FX-button hotspot vs. whole TCP" question is resolved to
+// the FX hotspot (the discoverable, unambiguous target), decided here from the SDK's own
+// hit-test string rather than a home-grown geometry guess.
+FxDropTarget resolveFxDropTarget(int screenX, int screenY);
+
+// Perform the drop on `track`: add a fresh ReaSampler 9000 instance and inject `chunkBase64`
+// (the instrument_drop::buildInstrumentDropChunk output) as its component state so it plays
+// the dragged capture. `chunkBase64` is the base64 vst_chunk. Wraps the add + inject in one
+// REAPER undo block (mirrors the bank-verb undo discipline). Returns true on success (the FX
+// was added and the chunk written), false on any failure. All-or-nothing: if the chunk write
+// fails after a successful add, the freshly-added FX instance is removed via TrackFX_Delete
+// before returning false, leaving the track exactly as it was (no orphaned empty-state FX).
+// NEVER inserts a timeline item; the ONLY mutations are the FX instance + its state, both
+// undoable.
+bool performInstrumentDrop(MediaTrack* track, const std::string& chunkBase64);
+
+}  // namespace reasampler

src/main.cpp

@@ -32,6 +32,7 @@
 #include "bank_panel.h"
 #include "batch_capture.h"
 #include "capture.h"
+#include "ingest.h"
 #include "insert.h"
 #include "persist.h"
 #include "provenance.h"
@@ -151,6 +152,16 @@ static int g_cmdCaptureTrackRealtime = 0;
 // explicit action, allowed by the console policy).
 static int g_cmdRecaptureFromSource = 0;
 
+// Command id for the S8 "capture selected item / time-selection into bank + assign"
+// action. NEW FOREVER-STABLE string (suffix CAPTURE_ITEM_ASSIGN). Reuses the offline
+// Item-scope capture path (RunCapture) verbatim — same razor-else-time range, same
+// FX-scope neutralize, same bank/persist landing — then writes an S8 assignment request
+// so the active sampler instance plays the just-captured sample on its next reload. NEVER
+// inserts a timeline item (the capture/placement separation holds; assign is a bank-index
+// + instance-selection act). Lives in the capture family (not the ingest family) because
+// it leans on main.cpp's capture render machinery, which is not exposed cross-module.
+static int g_cmdCaptureItemAssign = 0;
+
 // Command id for the M8 "cancel realtime capture" action. FOREVER-STABLE string.
 // Aborts the in-flight realtime capture (stop + restore, non-destructive) so a user
 // who started a long capture can bail without waiting for the range end or hunting for
@@ -205,7 +216,10 @@ static void CommitRealtimeResult(const reasampler::CaptureResult& res)
     // index AddResult — even a hash-collapse still WROTE a file the tool owns, and the
     // manifest dedups a repeat path itself (Phase R prune reconciles manifest vs index).
     g_session.owned().add(res.sample.relativePath);
-    g_session.saveToActiveProject();  // persist book + manifest + MarkProjectDirty (travels with .rpp)
+    // S9: a capture add changes what a live instance could play (a new sample landed in the
+    // active bank) -> bump before the persist so the stamped generation refreshes instances.
+    g_session.bumpBankGeneration();
+    g_session.saveToActiveProject();  // persist book + manifest + generation + MarkProjectDirty (travels with .rpp)
 }
 
 // Advance any in-flight realtime capture one tick. Cheap when none is running (a
@@ -738,6 +752,11 @@ static reasampler::CaptureResult renderOffline(
 // a bank index entry ONLY; never touches the arrange/timeline. Non-destructive: the
 // out-of-scope FX/fader/pan chain is fully restored on every path (FxBypassGuard),
 // and the backend restores every RENDER_* setting.
+//
+// On success, res.sample.id carries the LANDED bank-index id (S8): the newly-added id
+// on a fresh add, or the EXISTING entry's id on a hash-dedup collapse — so the S8
+// capture+assign path can target the sample actually in the bank. Batch callers ignore
+// it; the plain capture actions are unaffected.
 static reasampler::CaptureResult captureAndIndexOne(
     reasampler::CaptureScope scope,
     const ResolvedSource& src,
@@ -780,13 +799,26 @@ static reasampler::CaptureResult captureAndIndexOne(
     // resample-from-sample; otherwise the optional stays empty, per M1's contract).
     res.sample.provenance = prov;
 
-    // Add to the ACTIVE bank: g_session.bank() resolves to book.activeIndex() (B2).
-    g_session.bank().add(res.sample);
+    // Add to the ACTIVE bank: g_session.bank() resolves to book.activeIndex() (B2). The
+    // AddResult tells a fresh add from a hash-dedup collapse, so the assign path (S8) can
+    // target the sample actually in the bank (the existing entry on a collapse).
+    const reasampler::AddResult addResult = g_session.bank().add(res.sample);
     // B-cap: record the created file in the owned-file manifest, at the same point the
     // Sample is added. Recorded regardless of the index AddResult — even a hash-collapse
     // still WROTE a file the tool owns, and the manifest dedups a repeat path itself
     // (Phase R prune reconciles manifest vs index later).
     g_session.owned().add(res.sample.relativePath);
+
+    // Resolve the LANDED bank-index id into res.sample.id for the S8 assign path: the new
+    // id on a fresh Added (already in res.sample.id); the EXISTING entry's id on a
+    // Collapsed (the file we just rendered deduped onto an already-present sample — assign
+    // THAT one). Batch/plain-capture callers ignore this field; behaviour unchanged.
+    if (addResult == reasampler::AddResult::Collapsed && !res.sample.contentHash.empty())
+    {
+        if (const reasampler::Sample* existing =
+                g_session.bank().findByHash(res.sample.contentHash))
+            res.sample.id = existing->id;
+    }
     return res;
 }
 
@@ -794,14 +826,19 @@ static reasampler::CaptureResult captureAndIndexOne(
 // record via captureAndIndexOne, then persist + mark dirty. The load-bearing principle
 // holds structurally — this path writes a file + a bank index entry ONLY; it never
 // calls InsertMedia or touches the arrange/timeline.
-static void RunCapture(const reasampler::CaptureActionDef& def)
+// Returns the bank-index id of the sample the capture landed on: the newly-added id on a
+// fresh capture, or the EXISTING id on a hash-dedup collapse (so an ingest-with-assign
+// targets the sample actually in the bank). Empty on any failure / no-op. The S8 arrange
+// capture+assign path reads this to write an assignment request; the plain capture actions
+// ignore it (their behaviour is unchanged — capture still writes a file + index entry only).
+static std::string RunCapture(const reasampler::CaptureActionDef& def)
 {
     ResolvedSource src;
     std::string why;
     if (!ResolveScopeSource(def.scope, src, why))
     {
         ShowConsoleMsg(("ReaSampler capture: " + why + ".\n").c_str());
-        return;
+        return {};
     }
 
     reasampler::CaptureResult res =
@@ -809,14 +846,64 @@ static void RunCapture(const reasampler::CaptureActionDef& def)
     if (res.status != reasampler::CaptureStatus::Ok)
     {
         ShowConsoleMsg(("ReaSampler capture failed: " + res.message + "\n").c_str());
-        return;
+        return {};
     }
 
+    // captureAndIndexOne has already stamped provenance, added the Sample to the ACTIVE
+    // bank, and recorded the created file in the owned-file manifest (WITHOUT persisting).
     // Persist the updated book AND manifest into the active project's ext state (the
     // `banks` + `owned_files` keys) so the capture survives Save / close+reopen (M4) and
     // travels with the .rpp. saveToActiveProject also clears the retired legacy key and
     // calls MarkProjectDirty. Non-destructive: writes only our own ext-state keys.
+    // S9: a capture add is a bank-content change -> bump before the persist so an assigned
+    // live instance refreshes hands-free (the S8 capture+assign path builds on this).
+    g_session.bumpBankGeneration();
     g_session.saveToActiveProject();
+
+    // Hand the LANDED bank-index id back to the assign path (S8): captureAndIndexOne
+    // resolved res.sample.id to the fresh id on a new add or the existing entry's id on a
+    // hash-dedup collapse. Empty on any reject (unreachable here — status was Ok above).
+    return res.sample.id;
+}
+
+// S8 arrange ingest: capture the selected item / time-selection into the active bank
+// (reusing the Item-scope capture path verbatim) and, on success, write an assignment
+// request so the active sampler instance plays the new sample on its next reload. The
+// capture itself is unchanged — RunCapture writes a file + an index entry and NEVER
+// inserts a timeline item (load-bearing principle); the only addition here is the
+// bank-index-id -> assignment-request write after the sample lands. If the capture
+// failed / no-op'd (empty id), no assignment is written (nothing to assign).
+//
+// UNDO GROUPING: both the bank mutation (RunCapture -> saveToActiveProject) AND the
+// assignment-request write (ingestAssignActiveInstance -> writeAssignmentRequest) are
+// wrapped in a single undo block so Ctrl-Z rolls back both ext-state keys atomically.
+// An undo that removes the captured sample also clears the assign_request that named it,
+// preventing a stale request from pointing at a removed sample. The block uses the house
+// pattern (UNDO_STATE_MISCCFG, discarded on an unsaved project with empty label + zero
+// flag) matching the bank-op family in actions.cpp.
+static void RunCaptureItemAssign()
+{
+    // Reuse the Item-scope def from the capture table (index 0) — same range logic, same
+    // FX-scope neutralize, same bank/persist landing as the plain "capture item" action.
+    Undo_BeginBlock2(nullptr);
+
+    const std::string sampleId =
+        RunCapture(reasampler::captureActionTable()[0]);
+    if (sampleId.empty())
+    {
+        // Capture failed or no-op'd — RunCapture already reported. Discard the empty point.
+        Undo_EndBlock2(nullptr, "", 0);
+        return;
+    }
+
+    // Assign inside the same block so undo clears both keys together.
+    reasampler::ingestAssignActiveInstance(g_session.book().activeBankId(), sampleId);
+    Undo_EndBlock2(nullptr, "ReaSampler: capture + assign to active instance",
+                   UNDO_STATE_MISCCFG);
+
+    reasampler::bankPanelRefresh();
+    ShowConsoleMsg("ReaSampler ingest: captured into the bank and assigned to the active "
+                   "instance.\n");
 }
 
 // --- M11: batch capture (per selected item / per razor area) ----------------
@@ -961,8 +1048,12 @@ static void RunBatchCaptureItems()
     }  // selGuard restores the original selection here, on every path
 
     // Persist ONCE for the whole batch (one ext-state write) — only if something landed.
-    if (anyAdded)
+    // S9: one bump for the whole batch (coalesced) — the counter is monotonic, not per-sample,
+    // so a single increment past the last-seen value is enough to trigger one instance reload.
+    if (anyAdded) {
+        g_session.bumpBankGeneration();
         g_session.saveToActiveProject();
+    }
 
     ShowConsoleMsg((outcome.summaryLine("item") + "\n").c_str());
 }
@@ -1078,8 +1169,11 @@ static void RunBatchCaptureRazor()
         }
     }  // selGuard restores the original track selection here, on every path
 
-    if (anyAdded)
+    // S9: one coalesced bump for the whole razor batch (see the item-batch note above).
+    if (anyAdded) {
+        g_session.bumpBankGeneration();
         g_session.saveToActiveProject();
+    }
 
     ShowConsoleMsg((outcome.summaryLine("razor area") + "\n").c_str());
 }
@@ -1263,7 +1357,12 @@ static void RunRecaptureFromSource()
         // Record the regenerated file in the owned manifest (a new file the tool wrote);
         // the superseded old file becomes an orphan reclaimed by Phase R prune.
         g_session.owned().add(updated.relativePath);
-        const bool persisted = g_session.saveToActiveProject();  // book + manifest + MarkProjectDirty
+        // S9: re-capture-in-place regenerates the SAME id's audio — the exact case the
+        // hands-free refresh exists for (an instance referencing this id keeps playing the
+        // OLD audio until it reloads). Bump inside the undo block so undo rolls back the
+        // generation with the rest of the blob.
+        g_session.bumpBankGeneration();
+        const bool persisted = g_session.saveToActiveProject();  // book + manifest + generation + MarkProjectDirty
         Undo_EndBlock2(nullptr, persisted ? "ReaSampler: re-capture from source" : "",
                        persisted ? UNDO_STATE_MISCCFG : 0);
     }
@@ -1422,6 +1521,7 @@ static bool OnHookCommand(int command, int /*flag*/)
             return true;
         }
     if (command == g_cmdToggleBankPanel)         { reasampler::bankPanelToggle(); return true; }
+    if (command == g_cmdCaptureItemAssign)       { RunCaptureItemAssign(); return true; }
     if (command == g_cmdInsertSelected)          { RunInsertSelected(false); return true; }
     if (command == g_cmdInsertSelectedConform)   { RunInsertSelected(true);  return true; }
     if (command == g_cmdCaptureBatchItems)       { RunBatchCaptureItems(); return true; }
@@ -1440,6 +1540,8 @@ static bool OnHookCommand(int command, int /*flag*/)
     if (reasampler::designViewHandleCommand(command)) return true;
     // Multi-bank action family (B3). Same contract: claims only its own ids.
     if (reasampler::bankHandleCommand(command)) return true;
+    // S8 ingest action family (Media-Explorer import). Same contract.
+    if (reasampler::ingestHandleCommand(command)) return true;
     return false;
 }
 
@@ -1455,6 +1557,7 @@ static int OnToggleAction(int command)
 // gaccel storage must outlive registration — REAPER holds the pointer.
 // (The capture family's accels live in g_captureAccels, sized to the table.)
 static gaccel_register_t g_accelToggleBankPanel{};
+static gaccel_register_t g_accelCaptureItemAssign{};
 static gaccel_register_t g_accelInsertSelected{};
 static gaccel_register_t g_accelInsertSelectedConform{};
 static gaccel_register_t g_accelCaptureBatchItems{};
@@ -1468,6 +1571,7 @@ static gaccel_register_t g_accelShowVersion{};
 // (channelActionName) so it cannot be a string literal; REAPER holds the gaccel's `desc`
 // pointer, so each label lives here for the module lifetime. Composed once at registration.
 static std::string g_descToggleBankPanel;
+static std::string g_descCaptureItemAssign;
 static std::string g_descInsertSelected;
 static std::string g_descInsertSelectedConform;
 static std::string g_descCaptureBatchItems;
@@ -1480,6 +1584,7 @@ static std::string g_descShowVersion;
 // Composed command-id strings (channel-qualified), interned so register and the mirroring
 // '-command_id' unregister pass the SAME pointer. Set during registration; read on unload.
 static const char* g_idToggleBankPanel = nullptr;
+static const char* g_idCaptureItemAssign = nullptr;
 static const char* g_idInsertSelected = nullptr;
 static const char* g_idInsertSelectedConform = nullptr;
 static const char* g_idCaptureBatchItems = nullptr;
@@ -1519,6 +1624,8 @@ extern "C" REAPER_PLUGIN_DLL_EXPORT int REAPER_PLUGIN_ENTRYPOINT(
             reasampler::designViewUnregisterActions(g_rec);
             // Tear down the multi-bank action family (B3) — same mirror-unregister.
             reasampler::bankUnregisterActions(g_rec);
+            // Tear down the S8 ingest action family — same mirror-unregister.
+            reasampler::ingestUnregisterActions(g_rec);
             // Each '-command_id' re-presents the SAME interned, channel-qualified pointer
             // used at register (g_id*), so the mirror-unregister matches exactly.
             g_rec->Register("-gaccel", (void*)&g_accelShowVersion);
@@ -1537,6 +1644,8 @@ extern "C" REAPER_PLUGIN_DLL_EXPORT int REAPER_PLUGIN_ENTRYPOINT(
             g_rec->Register("-command_id", (void*)g_idInsertSelectedConform);
             g_rec->Register("-gaccel", (void*)&g_accelInsertSelected);
             g_rec->Register("-command_id", (void*)g_idInsertSelected);
+            g_rec->Register("-gaccel", (void*)&g_accelCaptureItemAssign);
+            g_rec->Register("-command_id", (void*)g_idCaptureItemAssign);
             g_rec->Register("-gaccel", (void*)&g_accelToggleBankPanel);
             g_rec->Register("-command_id", (void*)g_idToggleBankPanel);
             // Mirror-unregister the capture family: gaccel + command_id per row, with
@@ -1627,6 +1736,24 @@ extern "C" REAPER_PLUGIN_DLL_EXPORT int REAPER_PLUGIN_ENTRYPOINT(
         rec->Register("toggleaction", (void*)&OnToggleAction);
     }
 
+    // Register the S8 "capture selected item / time-selection into bank + assign" action
+    // (command_id -> gaccel -> hookcommand). Reuses the Item-scope offline capture path and
+    // writes an assignment request so the active instance plays the new sample. Channel-
+    // qualified FOREVER-STABLE id (suffix CAPTURE_ITEM_ASSIGN). MIDI-bindable like every
+    // capture action. Registered in the capture family (main.cpp) because it leans on the
+    // capture render machinery here; the other two ingest surfaces live in the ingest family
+    // (Media-Explorer import) and the panel drop callback.
+    g_idCaptureItemAssign = internCmdId("CAPTURE_ITEM_ASSIGN");
+    g_cmdCaptureItemAssign = rec->Register("command_id", (void*)g_idCaptureItemAssign);
+    if (g_cmdCaptureItemAssign)
+    {
+        g_descCaptureItemAssign = reasampler::channelActionName(
+            "capture selected item into bank + assign to active instance");
+        g_accelCaptureItemAssign.accel.cmd = g_cmdCaptureItemAssign;
+        g_accelCaptureItemAssign.desc      = g_descCaptureItemAssign.c_str();
+        rec->Register("gaccel", (void*)&g_accelCaptureItemAssign);
+    }
+
     // Register the M6 insert actions (command_id -> gaccel -> hookcommand). Two
     // variants: native-length (default, no stretch) and the EXPLICIT conform-to-
     // tempo opt-in. Both read the bank panel selection and place at the edit cursor.
@@ -1745,6 +1872,12 @@ extern "C" REAPER_PLUGIN_DLL_EXPORT int REAPER_PLUGIN_ENTRYPOINT(
     // by the same hookcommand via bankHandleCommand. Registered before the hook.
     reasampler::bankRegisterActions(rec, &g_session);
 
+    // Register the S8 ingest action family: the Media-Explorer import-into-bank+assign
+    // action. Shares g_session with the other families; routed by the same hookcommand via
+    // ingestHandleCommand. (The arrange capture+assign action is registered in the capture
+    // family above; the drop path is a bank_panel callback, not a bindable action.)
+    reasampler::ingestRegisterActions(rec, &g_session);
+
     // One hookcommand routes every ReaSampler action (spike + toggle + Design View).
     // Registered once, after all command ids are minted.
     rec->Register("hookcommand", (void*)&OnHookCommand);

src/persist.cpp

@@ -96,6 +96,7 @@
 #include "app_version.h"
 #include "capture_paths.h"
 #include "prune_reconcile.h"
+#include "vst/bank_sync.h"  // parseBankGeneration / formatBankGeneration (SHARED with the instrument reader)
 
 #define REAPERAPI_MINIMAL
 #define REAPERAPI_WANT_EnumProjects
@@ -128,11 +129,11 @@ void* readActiveProject(std::string& rppPathOut) {
 // Parent directory of the .rpp, forward-slashed, no trailing slash. Empty in ->
 // empty out. Mirrors capture.cpp's derivation so the bank sits alongside the
 // .rpp (NOT GetProjectPathEx, which returns the recording path — see capture.cpp
-// for the full rationale). normalizeSlashes lives in capture_paths (pure).
+// for the full rationale). The derivation itself is projectDirOfRpp in capture_paths
+// (pure) — the SAME convention the VST3 instrument resolves audio paths by, so both
+// artifacts share one implementation rather than duplicating the parent-of-.rpp step.
 std::string projectDirOf(const std::string& rppPath) {
-    if (rppPath.empty()) return {};
-    std::string dir = fs::path(rppPath).parent_path().string();
-    return normalizeSlashes(dir);
+    return projectDirOfRpp(rppPath);
 }
 
 // GetProjExtState needs a caller-supplied buffer; the index JSON can be large
@@ -252,6 +253,33 @@ bool ReaSamplerSession::saveToActiveProject() {
     SetProjExtState(static_cast<ReaProject*>(proj), projExtNamespace(),
                     kProjExtVersionKey, stampVersion().c_str());
 
+    // S9: stamp the current bank-generation counter under its own wire-shared key, on the SAME
+    // seam so the counter and MarkProjectDirty stay paired. The value is whatever
+    // bumpBankGeneration() advanced it to since the last save (0 if never bumped / pre-S9), so
+    // every content mutation's own save carries the fresh generation the instrument reads. The
+    // format is the SHARED pure encoder (vst::formatBankGeneration) so writer and reader agree
+    // byte-for-byte — a decimal integer. Additive: does not disturb the blobs above.
+    SetProjExtState(static_cast<ReaProject*>(proj), projExtNamespace(),
+                    kProjExtBankGenKey,
+                    vst::formatBankGeneration(bankGeneration_).c_str());
+
+    MarkProjectDirty(static_cast<ReaProject*>(proj));
+    return true;
+}
+
+bool ReaSamplerSession::writeAssignmentRequest(const std::string& wire) {
+    std::string rppPath;
+    void* proj = readActiveProject(rppPath);
+    if (!proj) return false;           // no active project — nothing to signal
+    if (rppPath.empty()) return false; // unsaved project — no .rpp to store into
+
+    // One-shot write of the ingest assignment request under its own key (S8). Independent
+    // of the book/view/tail blobs — this is a transient signal to the instrument, not
+    // session state that must ride every save. Uses the channel-derived namespace
+    // (projExtNamespace) like every sibling key — V4 isolation applies here too, so a beta
+    // instrument reads only a beta extension's assignment requests.
+    SetProjExtState(static_cast<ReaProject*>(proj), projExtNamespace(),
+                    kProjExtAssignKey, wire.c_str());
     MarkProjectDirty(static_cast<ReaProject*>(proj));
     return true;
 }
@@ -563,6 +591,16 @@ void ReaSamplerSession::loadFromProject(void* proj, const std::string& projectDi
                                      kProjExtVersionKey)
              : std::string{});
 
+    // S9: recover the bank-generation counter on EVERY load path (peer-symmetry with
+    // writingVersion_/tail_/view_ above), so it continues monotonic from the stored value
+    // rather than resetting to 0 on reopen — a next bump then reads > the stored value. A
+    // project switch reads THAT project's counter, not the previous one's; an absent/malformed
+    // stamp (pre-S9 or corrupt) parses to 0 via the SHARED decoder. proj == nullptr -> 0.
+    bankGeneration_ = vst::parseBankGeneration(
+        proj ? getProjExtStateString(static_cast<ReaProject*>(proj), projExtNamespace(),
+                                     kProjExtBankGenKey)
+             : std::string{});
+
     if (!proj) {
         book_ = BankBook{};
         return;

src/persist.h

@@ -17,11 +17,13 @@
 // calls live in persist.cpp. It depends on bank_model (pure) for JSON round-trip
 // and capture_paths (pure) for the path arithmetic it drives.
 
+#include <cstdint>
 #include <string>
 
 #include "app_version.h"
 #include "bank_book.h"
 #include "bank_model.h"
+#include "ext_keys.h"
 #include "owned_manifest.h"
 #include "prune_reconcile.h"
 #include "tail_control.h"
@@ -29,71 +31,50 @@
 
 namespace reasampler {
 
-// The ext-state namespace every ReaSampler key is stored under. CHANNEL-DERIVED (Phase V,
-// V4): the pure app_version module owns the one channel-qualified string — "reasampler" on
-// stable (byte-identical to the pre-V4 build) or "reasampler_beta" on the isolated beta
-// build. FOREVER-STABLE per channel once shipped: changing either orphans every already-
-// saved project's state. Beta reads/writes ONLY its own namespace — a project saved by
-// stable shows empty/default state in beta and vice versa; that isolation is the accepted
-// V4 safety property (no cross-namespace read, migration, or fallback), not a bug.
-// Returns const char* (not a constexpr literal) because the string is channel-derived at
-// build time; the accessor is the single call point for all persist reads/writes below.
+// The ext-state namespace + the WIRE-SHARED key names are the contract between this
+// extension (writer) and the VST3 instrument (reader), so they live in ext_keys.h
+// (pure, REAPER-free) and are included above — not duplicated here. The namespace is
+// CHANNEL-DERIVED (Phase V, V4): ext_keys.h's kProjExtNamespace / this projExtNamespace()
+// both delegate to app_version's extStateNamespace() — "reasampler" on stable (byte-
+// identical to the pre-V4 build) or "reasampler_beta" on the isolated beta build. Both
+// artifacts read the ONE app_version symbol, so the instrument reads exactly the namespace
+// the extension writes, per channel. Beta reads/writes ONLY its own namespace — a project
+// saved by stable shows empty/default state in beta and vice versa; that isolation is the
+// accepted V4 safety property (no cross-namespace read, migration, or fallback), not a bug.
+// The per-key semantics persist relies on (spellings owned by ext_keys.h):
+//   * kProjExtBanksKey  : the whole serialized BankBook (pool + named banks).
+//     AUTHORITATIVE going forward; the VST reads this key to see the live bank.
+//   * kProjExtIndexKey  : RETIRED legacy single-bank key. No longer WRITTEN (cleared
+//     on save); READ once on load to migrate a legacy project into the pool.
+//   * kProjExtViewKey   : the Design-View ViewModeModel JSON.
+//   * kProjExtTailKey   : the docked panel's TailSetting JSON.
+//   * kProjExtGuidKey   : the per-project minted GUID (content-based identity; poll()
+//     tells a Save-As from a recycled-pointer project switch by it).
+// All are FOREVER-STABLE once shipped: changing any strands every already-saved
+// project's stored state under that key.
+//
+// The accessor form of the namespace: ext_keys.h's kProjExtNamespace is the value; this
+// is the const char* the SetProjExtState/GetProjExtState calls in persist.cpp pass. Kept
+// as an accessor (not a literal) because the string is channel-derived at build time.
 inline const char* projExtNamespace() { return extStateNamespace().c_str(); }
 
-// The RETIRED legacy ext-state key: pre-multi-bank projects stored the whole
-// serialized BankIndex here (single bank). Phase B2 no longer WRITES it — on save
-// the key is cleared (SetProjExtState with "" deletes it) and the book is written
-// under kProjExtBanksKey instead. It is still READ once, on load of a legacy
-// project, to migrate its single index into the pool (BankBook's parse-time
-// promotion). FOREVER-STABLE as a read key for that migration path.
-inline constexpr const char* kProjExtIndexKey = "bank_index";
-
-// The multi-bank ext-state key (Phase B): one key holds the whole serialized
-// BankBook — the pool folded in as bank-zero plus every named bank, each with its
-// own BankIndex, ordinals, and the active-bank id. AUTHORITATIVE going forward;
-// supersedes kProjExtIndexKey. FOREVER-STABLE once shipped: changing it orphans
-// every already-saved project's banks.
-inline constexpr const char* kProjExtBanksKey = "banks";
-
-// The ext-state key the Design-View ViewModeModel JSON is stored under (one key
-// holds the whole serialized model: modes + membership + show-both + snapshots +
-// active mode). Distinct from kProjExtIndexKey — one namespace, two keys.
-// FOREVER-STABLE: changing it orphans every already-saved project's view state.
-inline constexpr const char* kProjExtViewKey = "view_state";
-
-// The ext-state key the docked panel's TailSetting JSON (mode + manualMs) is stored
-// under, so the tail choice travels inside the .rpp and loads per project. Distinct
-// from the index/view keys — one namespace, three keys. FOREVER-STABLE: changing it
-// orphans every already-saved project's tail setting (which then falls back to the
-// default — graceful, but the user's saved choice would be lost).
-inline constexpr const char* kProjExtTailKey = "tail_setting";
-
-// The ext-state key holding the owned-file manifest JSON (the set of project-relative
-// files the capture path itself created — Phase B B-cap seam, consumed by Phase R
-// prune to distinguish the bank system's own orphans from hand-dropped files). A
-// SIBLING key alongside banks/view_state/tail_setting — NOT folded into the `banks`
-// blob, so it stays decoupled from bank membership (removing an index entry is not a
-// manifest removal). One namespace, four content keys. FOREVER-STABLE: changing it
-// strands every already-saved project's ownership record, so Phase R prune could no
-// longer tell the tool's own files apart (it would fall back to an empty manifest —
+// The two EXTENSION-ONLY keys — NOT part of the VST wire contract (the instrument
+// reads only banks/view/tail/guid), so they stay here rather than in ext_keys.h:
+//
+// owned_files — the owned-file manifest JSON (project-relative files the capture path
+// itself created; Phase B B-cap seam, consumed by Phase R prune to tell the bank system's
+// own orphans from hand-dropped files). A SIBLING key alongside banks/view/tail — NOT
+// folded into `banks`, so it stays decoupled from membership. FOREVER-STABLE: changing it
+// strands every saved project's ownership record (prune falls back to an empty manifest —
 // graceful, but the attribution safety net is lost until the next capture rebuilds it).
 inline constexpr const char* kProjExtOwnedKey = "owned_files";
 
-// The ext-state key holding the ReaSampler version that last WROTE this project
-// (Phase V, V1). Written on every save alongside the banks/view/tail keys, so every
-// saved .rpp records which build produced its state — the seam a future within-channel
-// forward migration keys off ("this was written by 0.9.01, I am 0.9.05"). An absent
-// key is the explicit pre-versioning case (a project saved before this shipped), read
-// silently, never an error. FOREVER-STABLE key string once shipped.
+// version — the ReaSampler version that last WROTE this project (Phase V, V1). Written on
+// every save, so every saved .rpp records which build produced its state — the seam a
+// future within-channel forward migration keys off. An absent key is the explicit
+// pre-versioning case, read silently, never an error. FOREVER-STABLE key string.
 inline constexpr const char* kProjExtVersionKey = "version";
 
-// The ext-state key holding a GUID we mint per project to establish CONTENT-BASED
-// project identity (REAPER exposes no stable per-project GUID). poll() uses it to
-// tell a genuine Save-As (same GUID, new .rpp path) apart from a project switch
-// onto a recycled ReaProject* pointer (different GUID). FOREVER-STABLE: changing
-// it strands the identity of every already-saved project. See persist.cpp.
-inline constexpr const char* kProjExtGuidKey = "project_guid";
-
 // Owns the session's BankBook (Phase B: pool + named banks) and drives persistence
 // against the active REAPER project. One instance lives for the extension's
 // lifetime (main.cpp). It tracks
@@ -169,6 +150,24 @@ public:
     // reason about the origin build without re-reading ext state.
     const WritingVersion& writingVersion() const { return writingVersion_; }
 
+    // The S9 bank-generation counter (the value stamped under `bank_generation`). Monotonic
+    // per project: recovered on load (so it continues from the stored value rather than
+    // resetting), bumped by bank-content mutations via bumpBankGeneration(), and written on
+    // every saveToActiveProject(). Exposed const for the writer sites to read/log.
+    std::int64_t bankGeneration() const { return bankGeneration_; }
+
+    // Bump the S9 bank-generation counter — call at every bank-CONTENT mutation that changes
+    // what a live instance would PLAY (capture add, re-capture-in-place, sample remove,
+    // move/copy affecting banks, ingest import). NOT the pure-organizational verbs (create /
+    // rename / activate / reorder a bank), which change no existing (bankId, sampleId) ->
+    // content mapping. The bumped value is persisted by the NEXT saveToActiveProject() call
+    // the same mutation already makes (the counter rides the persist blob, so there is no
+    // separate write). In-memory only here — cheap and REAPER-free; the persist is the write.
+    // Over-bumping is safe (a reload that finds unchanged content atomically re-installs the
+    // same instrument, no glitch); under-bumping misses a hands-free refresh, so the sites err
+    // toward bumping. Idempotent per logical op — call once per mutation, before the persist.
+    void bumpBankGeneration() { ++bankGeneration_; }
+
     // Serialize the current book (under the `banks` key), view model, and tail setting
     // to the active project's ext state (namespace "reasampler"), and clear the retired
     // legacy `bank_index` key. Non-destructive beyond writing our own ext-state keys.
@@ -227,6 +226,21 @@ public:
     // shown the confirm; this method does NOT prompt.
     PruneDeletionResult pruneReclaim(const std::vector<std::string>& confirmed) const;
 
+    // Write the S8 ingest ASSIGNMENT REQUEST to the active project's ext state (the
+    // `assign_request` key, namespace "reasampler"): the extension telling the active
+    // sampler instance "play THIS sample now." `wire` is the pure assignment_request
+    // encoding (assignment_request.h); this method only routes the already-encoded value
+    // to ext state + MarkProjectDirty — the (bankId, sampleId, generation) shaping and
+    // the encode live in the ingest shell (the pure module) so persist stays a thin bridge.
+    //
+    // A SIBLING one-shot write, NOT part of saveToActiveProject's book/view/tail blob: an
+    // assignment request is a transient "just assigned" signal the instrument reads and
+    // acts on, so it rides its own key and is written only at ingest time, never on every
+    // book save. Returns true iff written (an active, SAVED project existed); false on a
+    // no-active / unsaved project (nothing to write into — the assign is dropped, matching
+    // the book/manifest quiet-persist idiom the ingest add-path already tolerates).
+    bool writeAssignmentRequest(const std::string& wire);
+
     // Poll the active project. Detects a project load (active project changed)
     // and a Save-As (active project's .rpp path changed) and reacts accordingly.
     // Intended to be driven by REAPER's "timer" register. Idempotent per tick.
@@ -287,6 +301,14 @@ private:
     // the previous project's stamp. Read-only to consumers via writingVersion().
     WritingVersion writingVersion_;
 
+    // The S9 bank-generation counter (peer to writingVersion_). Recovered on EVERY load path
+    // from the stored `bank_generation` stamp (parseBankGeneration; absent -> 0), so it
+    // continues monotonic from the persisted value across reopen and resets cleanly on a
+    // project switch (a different project's counter, not the previous project's). bumped by
+    // bumpBankGeneration() at bank-content mutations and stamped by saveToActiveProject().
+    // Default 0 for an unsaved / never-loaded / pre-S9 session.
+    std::int64_t bankGeneration_ = 0;
+
     // The project identity last observed by poll(), used to detect load/Save-As.
     // The GUID is the PRIMARY signal (a different stored GUID = a different project
     // of record = Load, immune to pointer recycling). The pointer disambiguates the

src/realtime_record.cpp

@@ -58,6 +58,9 @@ Sample sampleFromRecordedCapture(const RecordedCapture& cap) {
     // finalized and on disk — the hash is over the finished file bytes. Left empty
     // here because sampleFromRecordedCapture runs before the file exists (the
     // mapping is pure / DAW-free); the shell patches it in after the move+trim.
+    // Phase S seam fields (rootNote / loop) left empty (D-B) — same reasoning as the
+    // offline path: a realtime record of wet output is not a single played note, so
+    // no root note is derivable; loop points are set by a later explicit action.
     s.createdTimestamp = cap.createdTimestamp;
     return s;
 }

src/vst/bank_sync.cpp

@@ -0,0 +1,70 @@
+// bank_sync.cpp — see bank_sync.h. Pure; standard library only.
+
+#include "bank_sync.h"
+
+#include <cstdint>
+#include <limits>
+#include <string>
+
+namespace reasampler::vst {
+
+std::int64_t parseBankGeneration(const std::string& raw) {
+    if (raw.empty()) return kBankGenerationAbsent;
+
+    // Whole-string, non-negative decimal parse WITHOUT exceptions or locale surprises.
+    // A leading '+' / '-' , any non-digit, an empty digit run, or overflow past int64 max
+    // all reject to the absent default (0). Manual accumulation with an overflow guard so a
+    // pathologically long digit run can never wrap into a bogus small value.
+    std::int64_t value = 0;
+    constexpr std::int64_t kMax = std::numeric_limits<std::int64_t>::max();
+    for (const char c : raw) {
+        if (c < '0' || c > '9') return kBankGenerationAbsent;  // any non-digit -> reject whole
+        const int digit = c - '0';
+        // Guard value*10 + digit against overflow before performing it.
+        if (value > (kMax - digit) / 10) return kBankGenerationAbsent;  // would overflow -> reject
+        value = value * 10 + digit;
+    }
+    return value;
+}
+
+std::string formatBankGeneration(std::int64_t generation) {
+    // Non-negative decimal; a negative (should never be produced by the writer) formats as
+    // its std::to_string form and would parse back to 0, so the writer's monotonic counter
+    // stays in the >= 0 domain by construction.
+    return std::to_string(generation);
+}
+
+bool bankGenerationChanged(std::int64_t seen, std::int64_t current) {
+    return current != seen;
+}
+
+AssignConsumeDecision consumeDecision(const std::optional<AssignmentRequest>& request,
+                                      std::int64_t lastConsumed, bool resolves,
+                                      bool isFocusedTarget) {
+    AssignConsumeDecision d;
+    d.consumedGeneration = lastConsumed;  // default: nothing changes
+
+    // Rule 1: no request, or not newer than what we already consumed -> nothing new.
+    if (!request) return d;
+    if (request->generation <= lastConsumed) return d;
+
+    // Rule 2: a new request, but this instance is not the target -> do not act, do NOT
+    // advance the marker (stay eligible if focus later lands here). No thundering herd.
+    if (!isFocusedTarget) return d;
+
+    // The request is new AND we are the target: it will be consumed-as-seen either way, so
+    // advance the marker to its generation so it is never re-evaluated.
+    d.consumedGeneration = request->generation;
+
+    // Rule 3: unresolvable (bankId, sampleId) -> DROP silently (reader requirement): marker
+    // advanced above, but no selection change.
+    if (!resolves) return d;
+
+    // Rule 4: new, target, resolvable -> apply the selection.
+    d.apply = true;
+    d.bankId = request->bankId;
+    d.sampleId = request->sampleId;
+    return d;
+}
+
+}  // namespace reasampler::vst

src/vst/bank_sync.h

@@ -0,0 +1,105 @@
+#pragma once
+// bank_sync — PURE decision logic for the S9 bank-generation change-detection and the
+// S8 instrument-side assignment-request consume. NO VST3, NO REAPER, NO SWELL, NO
+// vendor/ includes. Standard library only. Unit-tested outside the DAW — the mirror of
+// sample_map / bridge_marshal splitting the fiddly, testable arithmetic out of a
+// host-facing shell.
+//
+// WHY IT EXISTS (S9/S8 reader seams). The instrument polls two "reasampler" ext-state
+// keys off the audio thread: the S9 bank-generation counter (has the bank changed?) and
+// the S8 assignment request (should I switch to a just-ingested sample?). The RAW string
+// read crosses the bridge in the shell; every DECISION after — parse the generation
+// stamp, decide whether it differs from what we last saw, decide whether a decoded
+// assignment request is NEW-and-resolvable-and-worth-applying — is pure and lives here.
+//
+// The processor shell owns the cadence (a UI-thread timer, NEVER process) and the side
+// effects (reloadFromBank, setSelectedSampleId); this module owns only the yes/no maths so
+// the reader's rules are provable without a host. assignment_request.h owns the WIRE format
+// (encode/decode); this module owns the CONSUME decision layered over a decoded request.
+
+#include <cstdint>
+#include <optional>
+#include <string>
+
+#include "assignment_request.h"  // AssignmentRequest (the decoded request this consumes)
+
+namespace reasampler::vst {
+
+// The S9 bank-generation "generation 0 = never stamped" default. A project saved before
+// S9 shipped carries no bank_generation key; the bridge read yields an absent/empty value
+// which parses to this, and the first real bump (>= 1) then reads as a change. Matches the
+// writer's monotonic-from-1 counter (the extension bumps to 1 on the first mutation).
+inline constexpr std::int64_t kBankGenerationAbsent = 0;
+
+// Parse the raw bank-generation ext-state value the bridge read. The writer stamps a
+// non-negative decimal integer (formatBankGeneration). Absent / empty / malformed / negative
+// / overflowing all yield kBankGenerationAbsent (0) — the reader treats any unreadable stamp
+// as "generation 0", so a pre-S9 or corrupt value is a clean default, never a crash and never
+// a spurious reload storm (0 vs a previously-seen 0 is no change). Whole-string parse: trailing
+// garbage after the digits rejects the value (returns 0), so a torn/partial write is ignored
+// until the next clean poll (the read tolerates staleness by design — it reloads on the NEXT
+// poll once the value is clean).
+std::int64_t parseBankGeneration(const std::string& raw);
+
+// Format a bank-generation counter for the ext-state stamp. The inverse of
+// parseBankGeneration for a non-negative value: a plain decimal, no sign, no padding, so
+// the stamp is byte-stable across writes of the same value.
+std::string formatBankGeneration(std::int64_t generation);
+
+// Has the bank generation changed since the reader last saw `seen`? True when `current`
+// differs from `seen` — the reader then triggers a reload. Any difference counts (not just
+// an increase): the writer is monotonic, but a project switch or reload can legitimately
+// lower the value, and the reader should re-read the bank in that case too. `seen` starts at
+// kBankGenerationAbsent so the first non-zero generation reads as a change (the pre-S9 /
+// first-bump refresh the spec requires).
+bool bankGenerationChanged(std::int64_t seen, std::int64_t current);
+
+// The verdict of the S8 assignment-request consume decision (below). A pure value the
+// processor shell acts on: apply the selection (or not) and advance the consumed marker
+// (or not). Distinct booleans because the two are NOT the same event — a request may be
+// consumed-as-seen (marker advances) without being applied (it named an unresolvable
+// sample and was DROPPED per the reader requirement), so the shell must not re-evaluate it
+// every poll.
+struct AssignConsumeDecision {
+    bool apply = false;                 // set this instance's selection to (bankId, sampleId) + reload
+    std::string bankId;                 // the request's bank (valid only when apply)
+    std::string sampleId;               // the request's sample (valid only when apply)
+    std::int64_t consumedGeneration = 0;  // the marker to persist (== lastConsumed when nothing new)
+};
+
+// Decide whether to CONSUME a decoded assignment request (S8 instrument-side reader).
+//
+//   `request`         — the decoded assignment request (nullopt when the assign_request key
+//                       is absent / malformed — nothing pending).
+//   `lastConsumed`    — the generation this instance last consumed (persisted in component
+//                       state so a re-open does not re-apply a request the user already got,
+//                       then manually changed away from). Defaults to 0 for a fresh instance.
+//   `resolves`        — whether the request's (bankId, sampleId) resolves to an existing bank
+//                       sample RIGHT NOW (the shell computed this against the live bank blob).
+//   `isFocusedTarget` — whether THIS instance is the assignment target under the shell's
+//                       thundering-herd policy (e.g. only the focused-editor instance applies).
+//                       The shell passes true when this instance should act; false suppresses
+//                       consumption entirely so a non-target instance neither applies nor
+//                       advances its marker (it stays eligible if it later becomes the target).
+//
+// RULES (all pure, order matters):
+//   1. No request, or an OLDER/equal generation (<= lastConsumed): nothing new — do not
+//      apply, marker unchanged. (Covers the re-open case: the persisted marker == the
+//      request's generation, so it is not re-applied.)
+//   2. A NEW request (generation > lastConsumed) but NOT this instance's target: do not
+//      apply and do NOT advance the marker — a non-target instance must stay able to consume
+//      the request if focus later lands on it. (No thundering herd: only the target acts.)
+//   3. A NEW request, this instance IS the target, but the (bankId, sampleId) does NOT
+//      resolve: DROP it silently (assignment_request.h reader requirement) — do not apply,
+//      but DO advance the marker to the request's generation so a stale/unresolvable request
+//      is consumed-as-seen and never re-evaluated (no error state, no selection change).
+//   4. A NEW request, target, and resolvable: APPLY (selection <- (bankId, sampleId)) and
+//      advance the marker to the request's generation.
+//
+// The shell then: if apply, setSelectedSampleId + reloadFromBank; always persist
+// consumedGeneration into component state when it advanced.
+AssignConsumeDecision consumeDecision(const std::optional<AssignmentRequest>& request,
+                                      std::int64_t lastConsumed, bool resolves,
+                                      bool isFocusedTarget);
+
+}  // namespace reasampler::vst

src/vst/bridge_marshal.cpp

@@ -0,0 +1,16 @@
+// bridge_marshal.cpp — see bridge_marshal.h. Pure; no host types.
+
+#include "bridge_marshal.h"
+
+namespace reasampler::vst {
+
+std::optional<std::string> decodeGetProjExtState(int apiReturn,
+                                                 const std::string& buffer) {
+    // REAPER returns the length of the stored value; 0 means the key is absent. Guard
+    // both the return AND the buffer: a caller that reused a dirty buffer must not
+    // surface stale bytes as a value when the API reported nothing.
+    if (apiReturn <= 0 || buffer.empty()) return std::nullopt;
+    return buffer;
+}
+
+}  // namespace reasampler::vst

src/vst/bridge_marshal.h

@@ -0,0 +1,37 @@
+// bridge_marshal.h — PURE marshalling helper for the REAPER VST-host bridge read.
+// NO VST3, NO REAPER types at the boundary.
+//
+// The bridge shell (reaper_bridge.cpp) resolves REAPER API functions by name over the
+// host callback and invokes them; the one fiddly-and-easy-to-get-wrong part around
+// GetProjExtState — interpreting its int return against the buffer it filled — is pure
+// and unit-tested here. Mirror of capture_paths / wav_trim splitting the arithmetic out
+// of a REAPER-facing shell.
+//
+// The S1 spike ALSO carried a string-scan JSON reader (extractJsonStringField) as a
+// stand-in until the instrument could parse the bank properly. S4 retired it: the
+// instrument now parses the "reasampler" bank blob through the SHARED bank_book /
+// bank_model JSON path (sample_map.cpp), so there is no second JSON parser. This module
+// is back to its one honest job — the API-return decode.
+//
+// Verified against vendor/reaper-sdk/sdk/reaper_plugin_functions.h:
+//   int  GetProjExtState (ReaProject*, extname, key, valOutNeedBig, valOutNeedBig_sz);
+//        -- returns the length written (0 when the key is absent).
+
+#pragma once
+
+#include <optional>
+#include <string>
+
+namespace reasampler::vst {
+
+// Interpret a GetProjExtState result: the int return value (bytes the API reports for
+// the key) and the buffer it filled. Returns the value only when the API reported a
+// non-empty result AND the buffer is non-empty — REAPER writes 0 and leaves the buffer
+// untouched for an absent key, and we must not treat stale buffer contents as a hit.
+//
+// `apiReturn` is GetProjExtState's return; `buffer` is the NUL-terminated string it
+// wrote (already truncated to the C string by the caller).
+std::optional<std::string> decodeGetProjExtState(int apiReturn,
+                                                  const std::string& buffer);
+
+}  // namespace reasampler::vst

src/vst/browser_scroll.cpp

@@ -0,0 +1,158 @@
+// browser_scroll.cpp — see browser_scroll.h. PURE scroll + search geometry over the S10
+// capture_browser. No host types; only the shared Rect + BrowserLayout.
+
+#include "browser_scroll.h"
+
+#include <algorithm>
+#include <cctype>
+
+namespace reasampler::vst {
+
+namespace {
+// The minimum thumb height so a very long bank still yields a grabbable thumb.
+constexpr int kMinThumbHeight = 20;
+
+char asciiLower(char c) {
+    return static_cast<char>(std::tolower(static_cast<unsigned char>(c)));
+}
+}  // namespace
+
+int scrollContentHeight(const BrowserLayout& layout, int cardCount) {
+    if (cardCount <= 0) return 0;
+    const int columns = (std::max)(1, layout.columns);
+    const int rows = (cardCount + columns - 1) / columns;  // ceil
+    return rows * kBrowserCardHeight;
+}
+
+int scrollMaxOffset(const BrowserLayout& layout, int cardCount) {
+    const int content = scrollContentHeight(layout, cardCount);
+    const int gridH = (std::max)(0, layout.grid.height());
+    return (std::max)(0, content - gridH);
+}
+
+int clampScrollOffset(const BrowserLayout& layout, int cardCount, int proposedOffset) {
+    const int maxOff = scrollMaxOffset(layout, cardCount);
+    if (proposedOffset < 0) return 0;
+    if (proposedOffset > maxOff) return maxOff;
+    return proposedOffset;
+}
+
+VisibleRange visibleCardRange(const BrowserLayout& layout, int cardCount, int offset) {
+    VisibleRange vr;
+    if (cardCount <= 0) return vr;
+    const int columns = (std::max)(1, layout.columns);
+    const int gridH = (std::max)(0, layout.grid.height());
+    if (gridH <= 0 || kBrowserCardHeight <= 0) {
+        vr.first = 0;
+        vr.last = 0;
+        return vr;
+    }
+    if (offset < 0) offset = 0;
+    // First visible ROW: the topmost row whose bottom edge is below the offset. Floor so a row
+    // partially scrolled off the top still draws (its lower part is visible).
+    const int firstRow = offset / kBrowserCardHeight;
+    // Last visible ROW: the row containing the pixel (offset + gridH - 1), inclusive; +1 for
+    // the exclusive end. A row straddling the bottom edge still draws.
+    const int lastRow = (offset + gridH - 1) / kBrowserCardHeight + 1;
+    int first = firstRow * columns;
+    int last = lastRow * columns;
+    if (first > cardCount) first = cardCount;
+    if (last > cardCount) last = cardCount;
+    if (last < first) last = first;
+    vr.first = first;
+    vr.last = last;
+    return vr;
+}
+
+Rect scrolledCardCellRect(const BrowserLayout& layout, int index, int offset) {
+    Rect r = cardCellRect(layout, index);
+    if (r.right <= r.left && r.bottom <= r.top) return r;  // empty (negative index) stays empty
+    return Rect{r.left, r.top - offset, r.right, r.bottom - offset};
+}
+
+Rect scrollThumbRect(const BrowserLayout& layout, int cardCount, int offset) {
+    const int content = scrollContentHeight(layout, cardCount);
+    const int gridH = (std::max)(0, layout.grid.height());
+    if (content <= gridH || gridH <= 0) return Rect{};  // fits -> no scrollbar
+    const int maxOff = content - gridH;
+    if (offset < 0) offset = 0;
+    if (offset > maxOff) offset = maxOff;
+
+    const int trackRight = layout.grid.right;
+    const int trackLeft = trackRight - kScrollbarWidth;
+    const int trackTop = layout.grid.top;
+
+    // Thumb height proportional to the visible fraction, floored at a grabbable minimum but
+    // never taller than the track.
+    int thumbH = static_cast<int>(static_cast<long long>(gridH) * gridH / content);
+    thumbH = (std::max)(kMinThumbHeight, thumbH);
+    thumbH = (std::min)(thumbH, gridH);
+
+    // Thumb top proportional to the offset over the movable track span.
+    const int trackSpan = gridH - thumbH;  // >= 0
+    int thumbTop = trackTop;
+    if (maxOff > 0 && trackSpan > 0) {
+        thumbTop = trackTop + static_cast<int>(
+                                  static_cast<long long>(offset) * trackSpan / maxOff);
+    }
+    return Rect{trackLeft, thumbTop, trackRight, thumbTop + thumbH};
+}
+
+int thumbDragToOffset(const BrowserLayout& layout, int cardCount, int startOffset,
+                      int dyPixels) {
+    const int content = scrollContentHeight(layout, cardCount);
+    const int gridH = (std::max)(0, layout.grid.height());
+    if (content <= gridH || gridH <= 0) return clampScrollOffset(layout, cardCount, startOffset);
+
+    // Thumb height (same formula as scrollThumbRect) -> movable track span in thumb pixels.
+    int thumbH = static_cast<int>(static_cast<long long>(gridH) * gridH / content);
+    thumbH = (std::max)(kMinThumbHeight, thumbH);
+    thumbH = (std::min)(thumbH, gridH);
+    const int trackSpan = gridH - thumbH;
+    if (trackSpan <= 0) return clampScrollOffset(layout, cardCount, startOffset);
+
+    const int maxOff = content - gridH;
+    // A 1px thumb move covers maxOff/trackSpan content px. Round to nearest for symmetry.
+    const long long deltaOffset =
+        (static_cast<long long>(dyPixels) * maxOff + (dyPixels >= 0 ? trackSpan / 2 : -trackSpan / 2)) /
+        trackSpan;
+    const long long proposed = static_cast<long long>(startOffset) + deltaOffset;
+    if (proposed < 0) return 0;
+    if (proposed > maxOff) return maxOff;
+    return static_cast<int>(proposed);
+}
+
+Rect searchBoxRect(int w) {
+    if (w <= 0) return Rect{};
+    return Rect{0, 0, w, kSearchBoxHeight};
+}
+
+bool nameMatchesQuery(const std::string& name, const std::string& query) {
+    if (query.empty()) return true;
+    if (query.size() > name.size()) return false;
+    // Case-insensitive substring scan (ASCII fold). Small strings; a naive scan is fine.
+    for (std::size_t i = 0; i + query.size() <= name.size(); ++i) {
+        bool match = true;
+        for (std::size_t j = 0; j < query.size(); ++j) {
+            if (asciiLower(name[i + j]) != asciiLower(query[j])) {
+                match = false;
+                break;
+            }
+        }
+        if (match) return true;
+    }
+    return false;
+}
+
+std::vector<int> filterNameIndices(const std::vector<std::string>& names,
+                                   const std::string& query) {
+    std::vector<int> out;
+    out.reserve(names.size());
+    for (int i = 0; i < static_cast<int>(names.size()); ++i) {
+        if (nameMatchesQuery(names[static_cast<std::size_t>(i)], query))
+            out.push_back(i);
+    }
+    return out;
+}
+
+}  // namespace reasampler::vst

src/vst/browser_scroll.h

@@ -0,0 +1,107 @@
+// browser_scroll.h — PURE scroll + type-to-filter geometry LAYERED over the S10
+// capture_browser. NO VST3, NO REAPER, NO SWELL/LICE types at the boundary. The mirror of
+// capture_browser / editor_geometry: the fiddly scroll-window + scrollbar-thumb + search-box
+// arithmetic lives here, unit-tested outside the DAW, while the editor shell draws the
+// clipped card window + the scrollbar + the search field and routes wheel/drag/keystrokes
+// into these functions.
+//
+// WHY IT EXISTS (S12). capture_browser (S10) lays out EVERY card top-down and the shell
+// clips at the browser bottom — a bank longer than the panel runs off with no way to reach
+// it (the S12 gap). This module adds the two things S12 layers over that stable geometry:
+//   * SCROLL — a vertical pixel offset into the card grid, with the max-offset clamp, the
+//     visible-row window, a scrollbar thumb rect, and the thumb-drag<->offset mapping so a
+//     wheel tick or a thumb drag reaches every card; and
+//   * SEARCH — a name-substring filter (case-insensitive) that narrows the drawn cards,
+//     COMPOSING with capture_browser's bank filter (the shell applies the bank filter first,
+//     then this search narrows within it) + the search-box rect the shell draws the field in.
+//
+// It holds NO card data and draws nothing — it knows only the browser layout (from
+// capture_browser), COUNTS, and the scroll OFFSET the shell owns as transient UI state. It
+// reuses capture_browser's BrowserLayout + the shared Rect (one geometry idiom).
+
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "capture_browser.h"  // BrowserLayout, cardCellRect, kBrowserCardHeight, Rect
+
+namespace reasampler::vst {
+
+// The width (px) of the vertical scrollbar gutter at the right edge of the grid. The shell
+// draws the track + thumb here and hit-tests thumb grabs against scrollThumbRect. Exposed so
+// the shell and tests agree. When the content fits (no scroll needed) the scrollbar is
+// suppressed (scrollThumbRect returns empty) and the shell may reclaim the gutter.
+inline constexpr int kScrollbarWidth = 10;
+
+// The height (px) of the type-to-filter search box the shell draws ABOVE the tab strip (a
+// thin band spanning the browser width). Exposed so the shell reserves the band and tests
+// agree. capture_browser's tab strip + grid sit BELOW this band (the shell offsets the
+// BrowserLayout it feeds to capture_browser by kSearchBoxHeight).
+inline constexpr int kSearchBoxHeight = 22;
+
+// The total pixel HEIGHT the card grid needs to draw all `cardCount` cards at `layout`'s
+// column count: the number of ROWS (ceil(cardCount / columns)) times the fixed cell height.
+// Zero cards -> 0. Pure — the content extent the scroll offset ranges over.
+int scrollContentHeight(const BrowserLayout& layout, int cardCount);
+
+// The maximum scroll offset (px): content height minus the visible grid height, floored at 0.
+// When the content fits within the grid this is 0 (nothing to scroll). Pure — the clamp
+// ceiling for every offset the shell tracks.
+int scrollMaxOffset(const BrowserLayout& layout, int cardCount);
+
+// Clamp a proposed scroll offset into [0, scrollMaxOffset]. The shell clamps after every wheel
+// tick / thumb drag so an over-scroll pins to an edge rather than showing past the last card
+// or above the first. Pure.
+int clampScrollOffset(const BrowserLayout& layout, int cardCount, int proposedOffset);
+
+// The half-open range of card INDICES [first, last) at least partially visible in the grid at
+// scroll `offset`. The shell draws only these cards (the S12 clip window) rather than every
+// card. `offset` is assumed pre-clamped (the shell clamps on input); a first past the last row
+// yields an empty range (first==last==cardCount). Pure.
+struct VisibleRange {
+    int first = 0;  // first card index drawn (inclusive)
+    int last = 0;   // one past the last card index drawn (exclusive)
+};
+VisibleRange visibleCardRange(const BrowserLayout& layout, int cardCount, int offset);
+
+// The cell rect of card `index` SHIFTED UP by the scroll offset, ready to draw (the shell
+// still adds the browser sub-area origin). Equivalent to capture_browser::cardCellRect with
+// the offset subtracted from top/bottom. Pure — the one place the offset applies to a card.
+Rect scrolledCardCellRect(const BrowserLayout& layout, int index, int offset);
+
+// The vertical scrollbar THUMB rect within the grid's right-edge gutter, sized proportional to
+// the visible fraction (grid height / content height) and positioned proportional to the
+// scroll offset. Returns an EMPTY rect when the content fits (no scroll needed) — the shell
+// suppresses the scrollbar then. A minimum thumb height keeps a tiny thumb grabbable on a very
+// long bank. Pure — the geometry the shell draws + hit-tests the thumb grab against.
+Rect scrollThumbRect(const BrowserLayout& layout, int cardCount, int offset);
+
+// Map a thumb-drag to a scroll offset. Given the offset the thumb held at grab time
+// (`startOffset`) and the vertical pixel delta since grab (`dyPixels`), returns the new
+// (clamped) scroll offset: startOffset shifted by the delta scaled from thumb-track pixels to
+// content pixels (a 1px thumb move covers content/track px of content). A degenerate track /
+// fitting content pins to startOffset. Pure — the inverse of scrollThumbRect's position map.
+int thumbDragToOffset(const BrowserLayout& layout, int cardCount, int startOffset, int dyPixels);
+
+// The search-box rect: a full-width band of height kSearchBoxHeight at the TOP of the browser
+// area (above where capture_browser's tab strip draws). `w` is the browser sub-area width;
+// the shell adds its origin. A zero/negative width yields an empty rect. Pure.
+Rect searchBoxRect(int w);
+
+// True iff `name` contains `query` as a case-insensitive ASCII substring. An EMPTY query
+// matches everything (the no-filter identity). Matching is ASCII case-folded (the display
+// names are ASCII until the Phase L type kit lands, mirroring the editor's other ASCII-only
+// text). Pure — the single match predicate the shell's search narrow is built from.
+bool nameMatchesQuery(const std::string& name, const std::string& query);
+
+// Narrow a list of display `names` to the INDICES whose name matches `query`, preserving
+// order. An EMPTY query returns every index [0, names.size()) (the composition base so "bank
+// filter, no search" == today's browser). Kept name-only (indices, not card structs) so this
+// module stays free of the sample_map/bank_book chain — the shell owns the SampleChoice list
+// and applies the bank filter FIRST, then feeds the surviving display names here (search
+// narrows within the bank). Pure.
+std::vector<int> filterNameIndices(const std::vector<std::string>& names,
+                                   const std::string& query);
+
+}  // namespace reasampler::vst

src/vst/capture_browser.cpp

@@ -0,0 +1,96 @@
+// capture_browser.cpp — see capture_browser.h. Pure math; no host types.
+
+#include "capture_browser.h"
+
+#include <algorithm>
+
+namespace reasampler::vst {
+
+namespace {
+
+// The left edge of tab i in a strip of the given x-origin and width divided into `count`
+// equal segments (mirror of mode_switch::segmentEdge). Every boundary derives from the same
+// formula, so consecutive tabs share an exact edge and the last tab reaches x+width exactly.
+int tabEdge(int x, int width, int i, int count) {
+    return x + (i * width) / count;
+}
+
+}  // namespace
+
+BrowserLayout layoutBrowser(int w, int h) {
+    const int cw = std::max(0, w);
+    const int ch = std::max(0, h);
+
+    BrowserLayout out;
+    const int tabH = std::min(kBrowserTabHeight, ch);
+    out.tabStrip = Rect{0, 0, cw, tabH};
+    out.grid = Rect{0, tabH, cw, ch};
+
+    const int gridW = std::max(0, out.grid.width());
+    out.columns = std::max(1, gridW / kBrowserCardWidth);
+    return out;
+}
+
+Rect cardCellRect(const BrowserLayout& layout, int index) {
+    if (index < 0) return Rect{};
+    const int cols = std::max(1, layout.columns);
+    const int col = index % cols;
+    const int row = index / cols;
+    const int left = layout.grid.left + col * kBrowserCardWidth;
+    const int top = layout.grid.top + row * kBrowserCardHeight;
+    return Rect{left, top, left + kBrowserCardWidth, top + kBrowserCardHeight};
+}
+
+Rect cardContentRect(const BrowserLayout& layout, int index) {
+    if (index < 0) return Rect{};
+    const Rect cell = cardCellRect(layout, index);
+    return Rect{cell.left + kBrowserCardGutter, cell.top + kBrowserCardGutter,
+                cell.right - kBrowserCardGutter, cell.bottom - kBrowserCardGutter};
+}
+
+Rect cardThumbnailRect(const BrowserLayout& layout, int index) {
+    if (index < 0) return Rect{};
+    const Rect content = cardContentRect(layout, index);
+    const int thumbH = std::min(kBrowserThumbHeight, std::max(0, content.height()));
+    return Rect{content.left, content.top, content.right, content.top + thumbH};
+}
+
+Rect cardLabelRect(const BrowserLayout& layout, int index) {
+    if (index < 0) return Rect{};
+    const Rect content = cardContentRect(layout, index);
+    const Rect thumb = cardThumbnailRect(layout, index);
+    return Rect{content.left, thumb.bottom, content.right, content.bottom};
+}
+
+int cardHitTest(const BrowserLayout& layout, int cardCount, int x, int y) {
+    if (cardCount <= 0) return -1;
+    if (!contains(layout.grid, x, y)) return -1;
+    const int cols = std::max(1, layout.columns);
+    const int col = (x - layout.grid.left) / kBrowserCardWidth;
+    const int row = (y - layout.grid.top) / kBrowserCardHeight;
+    if (col < 0 || col >= cols) return -1;  // past the last column (right dead-zone)
+    const int index = row * cols + col;
+    if (index < 0 || index >= cardCount) return -1;
+    // Only a hit inside the card CONTENT counts — a click in the inter-card gutter misses.
+    if (!contains(cardContentRect(layout, index), x, y)) return -1;
+    return index;
+}
+
+Rect filterTabRect(const BrowserLayout& layout, int tabCount, int index) {
+    if (tabCount <= 0 || index < 0 || index >= tabCount) return Rect{};
+    const Rect& strip = layout.tabStrip;
+    const int left = tabEdge(strip.left, std::max(0, strip.width()), index, tabCount);
+    const int right = tabEdge(strip.left, std::max(0, strip.width()), index + 1, tabCount);
+    return Rect{left, strip.top, right, strip.bottom};
+}
+
+int filterTabHitTest(const BrowserLayout& layout, int tabCount, int x, int y) {
+    if (tabCount <= 0) return -1;
+    if (!contains(layout.tabStrip, x, y)) return -1;
+    for (int i = 0; i < tabCount; ++i) {
+        if (contains(filterTabRect(layout, tabCount, i), x, y)) return i;
+    }
+    return -1;
+}
+
+}  // namespace reasampler::vst

src/vst/capture_browser.h

@@ -0,0 +1,92 @@
+// capture_browser.h — PURE layout + hit-test for the S10 capture-first editor's default
+// face: a scannable grid of capture CARDS with a bank-FILTER tab strip above it. NO VST3,
+// NO REAPER, NO SWELL/LICE types at the boundary. The mirror of editor_geometry /
+// embed_strip / mode_switch: the fiddly card-grid + tab arithmetic lives here so it is
+// unit-tested outside the DAW, while the editor shell draws each card's peak thumbnail +
+// name + root/key badge and routes clicks into these functions.
+//
+// The browser replaces the old text item-list (the named anti-pattern). It lays out N
+// cards in a fixed-cell grid that wraps across the browser width, and a horizontal tab
+// strip of bank filters (one tab per bank_book bank + an "All" tab) above the grid. This
+// module knows only COUNTS and RECTS — it draws nothing and holds no sample data; the
+// shell owns the SampleChoice list, the peak envelopes, and the filter state, and asks this
+// module only "where does card i draw" / "what did the user click".
+//
+// Scroll is NOT here (S12 layers it over this module). The browser lays out every card
+// top-down; the shell clips at the browser's bottom until S12 adds a scroll offset. Keeping
+// scroll out keeps this module the stable card/tab geometry S12 builds on.
+//
+// It reuses the same Rect + contains() as editor_geometry (one shared geometry idiom).
+
+#pragma once
+
+#include "editor_geometry.h"  // Rect, contains — one shared geometry idiom
+
+namespace reasampler::vst {
+
+// Fixed browser metrics, exposed so the shell and tests agree. The card is sized to show a
+// peak thumbnail with a name + badge line under it — scannable by eye, not a dense list.
+inline constexpr int kBrowserTabHeight = 26;   // the bank-filter tab strip band height
+inline constexpr int kBrowserCardWidth = 132;  // one card cell width (incl. gutter)
+inline constexpr int kBrowserCardHeight = 84;  // one card cell height (incl. gutter)
+inline constexpr int kBrowserCardGutter = 8;   // inset between the cell edge and the card
+inline constexpr int kBrowserThumbHeight = 44; // the peak-thumbnail band inside a card
+
+// The browser's regions, derived from the (w x h) area the shell allots it. Both clamp to
+// the area so a degenerate (tiny/zero) size never yields an inverted rect.
+struct BrowserLayout {
+    Rect tabStrip;  // top: the bank-filter tabs
+    Rect grid;      // below the tabs: where the capture cards tile
+    int columns = 1;  // cards per row in `grid` (>= 1); derived from grid.width()
+};
+
+// Divide a (w x h) browser area into its regions and compute the column count. Pure: same
+// inputs -> same layout. The tab strip takes a fixed height at the top (clamped so it never
+// exceeds the area); the grid takes the rest. columns = max(1, grid.width()/cardWidth) so a
+// browser narrower than one card still lays out a single column. A zero/negative size
+// yields empty rects + columns==1.
+BrowserLayout layoutBrowser(int w, int h);
+
+// The cell rect of capture card `index` (0-based) in the grid, laid out left-to-right then
+// top-to-bottom across `columns`. This is the full CELL (card + gutter); cardContentRect
+// insets it to the drawable card. Rows past the visible grid are still computed (the shell
+// clips at paint time). A negative index yields an empty rect. Pure.
+Rect cardCellRect(const BrowserLayout& layout, int index);
+
+// The drawable card rect inside a cell: the cell inset by kBrowserCardGutter on all sides.
+// The shell fills this (background + border) and draws the thumbnail/name/badge inside it. Pure.
+Rect cardContentRect(const BrowserLayout& layout, int index);
+
+// The peak-thumbnail sub-rect at the top of a card's content: full card width, the top
+// kBrowserThumbHeight (clamped to the card height). The shell draws the envelope here; the
+// name + badge go in the remaining strip below. Pure.
+Rect cardThumbnailRect(const BrowserLayout& layout, int index);
+
+// The name/badge sub-rect below the thumbnail: the card content minus the thumbnail band.
+// The shell draws the display name + root/key badge here. Pure.
+Rect cardLabelRect(const BrowserLayout& layout, int index);
+
+// The card a click at (x, y) lands on, given `cardCount` cards, or -1 for a click outside
+// every card (in a gutter, past the last card, or on the tab strip). Only the card CONTENT
+// rect counts as a hit — a click in the inter-card gutter is a miss. Pure.
+int cardHitTest(const BrowserLayout& layout, int cardCount, int x, int y);
+
+// --- Bank-filter tabs --------------------------------------------------------
+//
+// The tab strip divides tabStrip into `tabCount` equal segments (mirror of mode_switch):
+// one tab per bank_book bank plus a leading "All" tab the shell prepends, so tabCount ==
+// bankCount + 1 in practice. This module only divides the strip + hit-tests; the shell
+// supplies the labels and tracks which tab is active. A tab click narrows the card list to
+// that bank (the shell filters its SampleChoice list before laying out cards).
+
+// The rect of tab `index` (0-based) when the strip is divided into `tabCount` equal
+// segments. The last tab absorbs any width remainder so the tabs tile the whole strip with
+// no gap (mirror of mode_switch's segment split). A negative index or tabCount<=0 yields an
+// empty rect. Pure.
+Rect filterTabRect(const BrowserLayout& layout, int tabCount, int index);
+
+// The tab a click at (x, y) lands on, given `tabCount` tabs, or -1 for a click outside the
+// tab strip. Pure.
+int filterTabHitTest(const BrowserLayout& layout, int tabCount, int x, int y);
+
+}  // namespace reasampler::vst

src/vst/editor_geometry.cpp

@@ -0,0 +1,164 @@
+// editor_geometry.cpp — see editor_geometry.h. Pure math; no host types.
+
+#include "editor_geometry.h"
+
+#include <algorithm>
+
+namespace reasampler::vst {
+
+namespace {
+
+// Spike editor layout constants. These are the editor's fixed metrics; the real
+// editor (S4/S5) will parameterize as its content demands.
+constexpr int kTitleBarHeight = 28;
+constexpr int kButtonMargin = 10;
+constexpr int kButtonWidth = 120;
+constexpr int kButtonHeight = 24;
+
+}  // namespace
+
+bool contains(const Rect& r, int x, int y) {
+    if (r.width() <= 0 || r.height() <= 0) return false;
+    return x >= r.left && x < r.right && y >= r.top && y < r.bottom;
+}
+
+EditorLayout layoutEditor(int w, int h) {
+    // Clamp the surface to non-negative extents so a degenerate view can't produce
+    // inverted rects.
+    const int cw = std::max(0, w);
+    const int ch = std::max(0, h);
+
+    EditorLayout out;
+
+    // Title bar spans the top, clamped so it never exceeds the client height.
+    const int titleH = std::min(kTitleBarHeight, ch);
+    out.titleBar = Rect{0, 0, cw, titleH};
+
+    // Canvas is everything below the title bar.
+    out.canvas = Rect{0, titleH, cw, ch};
+
+    // Button sits at the top-left of the canvas, inset by a margin, and is clamped to
+    // fit inside the canvas so it never overhangs on a small view.
+    const int bx = out.canvas.left + kButtonMargin;
+    const int by = out.canvas.top + kButtonMargin;
+    const int bRight = std::min(bx + kButtonWidth, out.canvas.right);
+    const int bBottom = std::min(by + kButtonHeight, out.canvas.bottom);
+    out.button = Rect{bx, by, std::max(bx, bRight), std::max(by, bBottom)};
+
+    return out;
+}
+
+HitTarget hitTest(const EditorLayout& layout, int x, int y) {
+    if (contains(layout.button, x, y)) return HitTarget::kButton;
+    return HitTarget::kNone;
+}
+
+Rect sampleRowRect(const EditorLayout& layout, int index) {
+    if (index < 0) return Rect{};
+    const int top = layout.canvas.top + index * kSampleRowHeight;
+    return Rect{layout.canvas.left, top, layout.canvas.right, top + kSampleRowHeight};
+}
+
+int sampleRowHitTest(const EditorLayout& layout, int rowCount, int x, int y) {
+    if (rowCount <= 0) return -1;
+    // Must be within the canvas horizontally and at/below its top.
+    if (x < layout.canvas.left || x >= layout.canvas.right) return -1;
+    if (y < layout.canvas.top) return -1;
+    // Clip at the canvas bottom: clicks in the canvas's dead-zone below the last
+    // visible row agree with sampleRowRect, which does not clamp rows to canvas.bottom.
+    if (y >= layout.canvas.bottom) return -1;
+    const int index = (y - layout.canvas.top) / kSampleRowHeight;
+    if (index < 0 || index >= rowCount) return -1;
+    // Guard the bottom edge: a click below the last row's bottom is outside.
+    const Rect r = sampleRowRect(layout, index);
+    if (y >= r.bottom) return -1;
+    return index;
+}
+
+// --- Keymap editor -----------------------------------------------------------
+
+KeymapEditorLayout layoutKeymapEditor(int w, int h) {
+    KeymapEditorLayout out;
+    out.base = layoutEditor(w, h);
+    const Rect& canvas = out.base.canvas;
+
+    // Split the canvas vertically: the left column is the bank-sample list, the right
+    // column (1/kZonePanelFraction of the width) is the zone panel. Guard tiny widths so
+    // the split point never crosses the canvas edges.
+    const int canvasW = std::max(0, canvas.width());
+    const int splitW = canvasW / kZonePanelFraction;          // width of the zone panel
+    const int splitX = std::max(canvas.left, canvas.right - splitW);
+
+    out.sampleList = Rect{canvas.left, canvas.top, splitX, canvas.bottom};
+    out.zonePanel = Rect{splitX, canvas.top, canvas.right, canvas.bottom};
+
+    // "Add Zone" button spans the top of the zone panel, clamped to its height.
+    const int addH = std::min(kAddZoneHeight, std::max(0, out.zonePanel.height()));
+    out.addZoneButton =
+        Rect{out.zonePanel.left, out.zonePanel.top, out.zonePanel.right,
+             out.zonePanel.top + addH};
+
+    // Zone rows stack below the button.
+    out.zoneRowArea = Rect{out.zonePanel.left, out.addZoneButton.bottom,
+                           out.zonePanel.right, out.zonePanel.bottom};
+    return out;
+}
+
+Rect keymapSampleRowRect(const KeymapEditorLayout& layout, int index) {
+    if (index < 0) return Rect{};
+    const int top = layout.sampleList.top + index * kSampleRowHeight;
+    return Rect{layout.sampleList.left, top, layout.sampleList.right,
+                top + kSampleRowHeight};
+}
+
+int keymapSampleRowHitTest(const KeymapEditorLayout& layout, int rowCount, int x, int y) {
+    if (rowCount <= 0) return -1;
+    const Rect& list = layout.sampleList;
+    if (x < list.left || x >= list.right) return -1;
+    if (y < list.top || y >= list.bottom) return -1;
+    const int index = (y - list.top) / kSampleRowHeight;
+    if (index < 0 || index >= rowCount) return -1;
+    const Rect r = keymapSampleRowRect(layout, index);
+    if (y >= r.bottom) return -1;
+    return index;
+}
+
+Rect zoneRowRect(const KeymapEditorLayout& layout, int index) {
+    if (index < 0) return Rect{};
+    const int top = layout.zoneRowArea.top + index * kZoneRowHeight;
+    return Rect{layout.zoneRowArea.left, top, layout.zoneRowArea.right,
+                top + kZoneRowHeight};
+}
+
+ZoneHit zoneHitTest(const KeymapEditorLayout& layout, int zoneCount, int x, int y) {
+    if (zoneCount <= 0) return ZoneHit{};
+    const Rect& area = layout.zoneRowArea;
+    if (x < area.left || x >= area.right) return ZoneHit{};
+    if (y < area.top || y >= area.bottom) return ZoneHit{};
+    const int index = (y - area.top) / kZoneRowHeight;
+    if (index < 0 || index >= zoneCount) return ZoneHit{};
+    const Rect row = zoneRowRect(layout, index);
+    if (y >= row.bottom) return ZoneHit{};
+
+    // Seven mini-buttons pinned to the right edge, right-to-left:
+    //   delete, root+, root-, high+, high-, low+, low-
+    // Each is kZoneCtrlWidth wide. A click left of the leftmost is the label ("select").
+    // The fields laid out LEFT-TO-RIGHT in slot order 0..6.
+    const ZoneField fields[7] = {
+        ZoneField::kLowDown, ZoneField::kLowUp,  ZoneField::kHighDown,
+        ZoneField::kHighUp,  ZoneField::kRootDown, ZoneField::kRootUp,
+        ZoneField::kDelete,
+    };
+    const int slots = 7;
+    const int ctrlBlockLeft = row.right - slots * kZoneCtrlWidth;
+    if (x < ctrlBlockLeft) return ZoneHit{index, ZoneField::kZoneNone};  // label -> select
+    const int slot = (x - ctrlBlockLeft) / kZoneCtrlWidth;
+    if (slot < 0 || slot >= slots) return ZoneHit{index, ZoneField::kZoneNone};
+    return ZoneHit{index, fields[slot]};
+}
+
+bool addZoneHitTest(const KeymapEditorLayout& layout, int x, int y) {
+    return contains(layout.addZoneButton, x, y);
+}
+
+}  // namespace reasampler::vst

src/vst/editor_geometry.h

@@ -0,0 +1,149 @@
+// editor_geometry.h — PURE view geometry + hit-test for the VST3 IPlugView LICE
+// editor (Phase S1). NO VST3, NO REAPER, NO SWELL/LICE types at the boundary.
+//
+// The IPlugView shell (reasampler_editor.cpp) owns the window/bitmap/SWELL plumbing
+// and is DAW-verified; this module holds the fiddly rectangle math and hit-testing so
+// it can be unit-tested outside the DAW — the mirror of how bank_grid / mode_switch /
+// tab_strip split their layout math out of the panel shell.
+//
+// The spike's editor is deliberately trivial (a title band + one clickable button),
+// enough to PROVE the host->draw/hit-test event routing works. As the real editor
+// (S4/S5) grows, its layout math accretes here, not in the shell.
+
+#pragma once
+
+namespace reasampler::vst {
+
+// A plain integer rectangle. left/top inclusive, right/bottom exclusive — the same
+// half-open convention LICE/SWELL RECTs use, kept REAPER-free here.
+struct Rect {
+    int left = 0;
+    int top = 0;
+    int right = 0;
+    int bottom = 0;
+
+    int width() const { return right - left; }
+    int height() const { return bottom - top; }
+};
+
+// Returns true if (x, y) falls inside r under the half-open convention
+// (left <= x < right, top <= y < bottom). A zero-or-negative-area rect contains
+// nothing.
+bool contains(const Rect& r, int x, int y);
+
+// The regions the spike editor draws, derived from the current view size. All are
+// clamped to the client area so a degenerate (too-small) view never yields a region
+// that spills outside the surface.
+struct EditorLayout {
+    Rect titleBar;   // top band: the plugin name + a live-state readout
+    Rect button;     // a single clickable button (proves hit-test routing)
+    Rect canvas;     // the remaining surface below the title bar
+};
+
+// Divide a (w x h) client area into the spike editor's regions. Pure: the same
+// inputs always yield the same layout. Guards tiny sizes — every returned rect stays
+// within [0,w] x [0,h], and the button never overhangs the canvas.
+EditorLayout layoutEditor(int w, int h);
+
+// The editor's hit-test targets. kNone means the point landed on inert surface.
+enum class HitTarget {
+    kNone,
+    kButton,
+};
+
+// Classify a click at (x, y) against a layout. The button wins only when the point is
+// inside the button rect; everything else (including the title bar and empty canvas)
+// is kNone in the spike.
+HitTarget hitTest(const EditorLayout& layout, int x, int y);
+
+// --- Sample-selection list (S4 Tier-0 UI) -----------------------------------
+//
+// The Tier-0 editor lists the bank's samples as a vertical stack of fixed-height rows
+// below the title bar; clicking a row selects that sample. This is the pure geometry:
+// the row rectangles and the point->row hit-test, unit-tested outside the DAW while the
+// shell draws the names and routes the click into the processor's reloadFromBank.
+
+// The fixed row height (px) for one sample entry. Exposed so the shell and tests agree.
+inline constexpr int kSampleRowHeight = 22;
+
+// The rectangle for row `index` (0-based) of the sample list, laid out top-down inside
+// the layout's canvas. Rows beyond what the canvas can show are still computed (the
+// shell clips at paint time); a negative index yields an empty rect. Pure.
+Rect sampleRowRect(const EditorLayout& layout, int index);
+
+// The row index a click at (x, y) lands on, given `rowCount` rows, or -1 for a click
+// outside the list (above the first row, past the last, or on the title bar). Pure.
+int sampleRowHitTest(const EditorLayout& layout, int rowCount, int x, int y);
+
+// --- Keymap editor (S5 Tier-1 UI) -------------------------------------------
+//
+// The Tier-1 editor splits the canvas into a LEFT bank-sample list (the same rows as
+// Tier 0, reused for the "sample to add / fallback pick") and a RIGHT zone panel listing
+// the performance map's zones. An "Add Zone" button sits at the top of the zone panel;
+// each zone row carries small nudge/delete controls so the user can set the range and
+// root note without a text field (LICE has no native numeric entry). All rectangle math
+// is here so the shell only draws + routes — the mirror of the sample-list split above.
+
+// Fixed metrics for the zone panel, exposed so the shell and tests agree.
+inline constexpr int kZoneRowHeight = 24;
+inline constexpr int kZonePanelFraction = 2;  // zone panel gets the RIGHT 1/2 of the canvas
+inline constexpr int kZoneCtrlWidth = 20;     // width of one nudge/delete mini-button
+inline constexpr int kAddZoneHeight = 22;     // the "Add Zone" button band height
+
+// The keymap editor's regions, derived from the (w x h) client area. All clamp to the
+// canvas so a degenerate view yields in-bounds rects.
+struct KeymapEditorLayout {
+    EditorLayout base;   // title bar + canvas (the sample list uses base.canvas.left half)
+    Rect sampleList;     // LEFT column: the bank-sample rows (sampleRowRect is relative here)
+    Rect zonePanel;      // RIGHT column: the "Add Zone" button + the zone rows
+    Rect addZoneButton;  // top of the zone panel
+    Rect zoneRowArea;    // below addZoneButton: where zone rows stack
+};
+
+KeymapEditorLayout layoutKeymapEditor(int w, int h);
+
+// The rectangle for bank-sample row `index` inside the LEFT sample list column of a
+// keymap layout. Same fixed height as the Tier-0 list; laid out top-down inside
+// sampleList. Negative index -> empty. Pure.
+Rect keymapSampleRowRect(const KeymapEditorLayout& layout, int index);
+
+// The bank-sample row a click lands on inside the left list, or -1 outside it. Pure.
+int keymapSampleRowHitTest(const KeymapEditorLayout& layout, int rowCount, int x, int y);
+
+// The rectangle for zone row `index` inside the zone panel's zoneRowArea. Negative
+// index -> empty. Pure.
+Rect zoneRowRect(const KeymapEditorLayout& layout, int index);
+
+// A zone row's interactive fields. The row is a horizontal strip: a label on the left,
+// then seven fixed-width mini-buttons on the right (left-to-right: low-, low+, high-, high+,
+// root-, root+, delete). kZoneNone means the click missed a control
+// (e.g. on the label) — the shell may still treat that as "select this zone".
+enum class ZoneField {
+    kZoneNone,
+    kLowDown,
+    kLowUp,
+    kHighDown,
+    kHighUp,
+    kRootDown,
+    kRootUp,
+    kDelete,
+};
+
+// The result of hit-testing a click against the zone rows: which zone row (or -1) and
+// which field within it. A click on the "Add Zone" button is reported separately by
+// addZoneHitTest — this covers only the zone rows.
+struct ZoneHit {
+    int zoneIndex = -1;
+    ZoneField field = ZoneField::kZoneNone;
+};
+
+// Classify a click at (x, y) against `zoneCount` zone rows. Returns {-1, kZoneNone} for a
+// click outside every zone row. Within a row, the seven mini-buttons occupy fixed-width
+// slots on the right edge (left-to-right: low-, low+, high-, high+, root-, root+, delete);
+// a click left of those slots is {index, kZoneNone} (the label area — "select"). Pure.
+ZoneHit zoneHitTest(const KeymapEditorLayout& layout, int zoneCount, int x, int y);
+
+// True if (x, y) lands on the "Add Zone" button. Pure.
+bool addZoneHitTest(const KeymapEditorLayout& layout, int x, int y);
+
+}  // namespace reasampler::vst

src/vst/embed_strip.cpp

@@ -0,0 +1,86 @@
+// embed_strip.cpp — see embed_strip.h. Pure math; no host types.
+
+#include "embed_strip.h"
+
+#include <algorithm>
+
+namespace reasampler::vst {
+
+namespace {
+
+// Clamp a MIDI note to [0, kEmbedKeyCount-1].
+int clampNote(int n) {
+    if (n < 0) return 0;
+    if (n > kEmbedKeyCount - 1) return kEmbedKeyCount - 1;
+    return n;
+}
+
+// Map a key boundary in [0, kEmbedKeyCount] to an x pixel inside a band of the given
+// left/width. keyEdge is a boundary (0..128), so keyEdge==128 maps to the band's right.
+// Integer math, floored — a zone's left uses floor(low) and its right uses floor(high+1),
+// which tiles adjacent zones without a seam.
+int keyEdgeToX(int bandLeft, int bandWidth, int keyEdge) {
+    if (keyEdge <= 0) return bandLeft;
+    if (keyEdge >= kEmbedKeyCount) return bandLeft + bandWidth;
+    return bandLeft + (keyEdge * bandWidth) / kEmbedKeyCount;
+}
+
+}  // namespace
+
+EmbedLayout layoutEmbed(int w, int h) {
+    const int cw = std::max(0, w);
+    const int ch = std::max(0, h);
+
+    EmbedLayout out;
+
+    // The level band takes a fixed height at the bottom, but never so much that the keymap
+    // above it falls below its minimum (or that the band exceeds the area). On a very short
+    // area the band yields to the keymap entirely.
+    int bandH = std::min(kEmbedLevelBandHeight, ch);
+    if (ch - bandH < kEmbedKeymapMinHeight) {
+        bandH = std::max(0, ch - kEmbedKeymapMinHeight);
+    }
+    const int keymapBottom = ch - bandH;
+
+    out.keymap = Rect{0, 0, cw, keymapBottom};
+    out.levelBand = Rect{0, keymapBottom, cw, ch};
+    return out;
+}
+
+Rect zoneSegmentRect(const EmbedLayout& layout, int lowNote, int highNote) {
+    const Rect& band = layout.keymap;
+    const int bandWidth = std::max(0, band.width());
+
+    int lo = clampNote(lowNote);
+    int hi = clampNote(highNote);
+    if (lo > hi) lo = hi;  // defensive: a malformed zone collapses rather than inverts
+
+    const int leftX = keyEdgeToX(band.left, bandWidth, lo);
+    const int rightX = keyEdgeToX(band.left, bandWidth, hi + 1);
+    return Rect{leftX, band.top, std::max(leftX, rightX), band.bottom};
+}
+
+int zoneAtPoint(const EmbedLayout& layout, const EmbedZone* zones, int zoneCount, int x,
+                int y) {
+    if (zoneCount <= 0 || zones == nullptr) return -1;
+    if (!contains(layout.keymap, x, y)) return -1;
+    // First covering zone in draw order wins (first-match, mirroring the core's resolve).
+    for (int i = 0; i < zoneCount; ++i) {
+        const Rect r = zoneSegmentRect(layout, zones[i].lowNote, zones[i].highNote);
+        if (contains(r, x, y)) return i;
+    }
+    return -1;  // on the band but on an uncovered key
+}
+
+Rect levelFillRect(const EmbedLayout& layout, double level) {
+    const Rect& band = layout.levelBand;
+    if (band.width() <= 0 || band.height() <= 0) return Rect{};
+    double l = level;
+    if (l < 0.0) l = 0.0;
+    if (l > 1.0) l = 1.0;
+    const int fillW = static_cast<int>(l * band.width());
+    if (fillW <= 0) return Rect{};
+    return Rect{band.left, band.top, band.left + fillW, band.bottom};
+}
+
+}  // namespace reasampler::vst

src/vst/embed_strip.h

@@ -0,0 +1,76 @@
+// embed_strip.h — PURE layout + hit-test for the S6 embedded TCP/MCP strip. NO VST3,
+// NO REAPER, NO SWELL/LICE types at the boundary. The mirror of editor_geometry /
+// mode_switch: the fiddly rectangle math for the compact inline keymap/level strip lives
+// here so it is unit-tested outside the DAW, while the embed shell (reasampler_embed.cpp)
+// marshals REAPER's embed messages (paint bitmap + mouse coords) into these functions.
+//
+// The strip is a single compact band REAPER draws inline in the track/mixer control panel
+// (context TCP or MCP) via the Cockos embedded-UI surface. It shows:
+//   * the zone layout — each performance zone as a horizontal segment across the keyboard
+//     span (MIDI 0..127 mapped to the strip width), so the keymap reads at a glance; and
+//   * a thin level band at the bottom — a 0..1 activity indicator the shell fills.
+// Interaction is zone SELECTION at most (S6 constraint: no new editing semantics) — a
+// click maps to the zone whose key range covers that point, or -1.
+//
+// It reuses the same Rect + contains() as editor_geometry (the strip and the editor share
+// one geometry idiom), so this header depends on editor_geometry.h rather than redefining
+// a second rectangle type.
+
+#pragma once
+
+#include "editor_geometry.h"  // Rect, contains — one shared geometry idiom
+
+namespace reasampler::vst {
+
+// The full MIDI key span the strip maps across its width. 128 keys (0..127); the strip's
+// horizontal axis is this range, so a zone [lowNote, highNote] becomes a sub-rectangle.
+inline constexpr int kEmbedKeyCount = 128;
+
+// Fixed metrics for the strip, exposed so the shell and tests agree.
+inline constexpr int kEmbedLevelBandHeight = 4;  // the bottom activity band (px)
+inline constexpr int kEmbedKeymapMinHeight = 6;  // keymap area collapses no smaller
+
+// One zone rendered on the strip: its inclusive MIDI key range. This is the minimal
+// projection of a PerformanceZone the strip needs (it does not carry sample ids or PCM —
+// the shell resolves labels; the strip only lays out ranges). lowNote/highNote are
+// expected in [0,127] with low <= high, but the layout clamps defensively so a malformed
+// zone never yields an out-of-strip rect.
+struct EmbedZone {
+    int lowNote = 0;
+    int highNote = 127;
+};
+
+// The strip's regions, derived from the (w x h) embed area REAPER reports. Both clamp to
+// the area so a degenerate (tiny) size never yields a region spilling outside the surface.
+struct EmbedLayout {
+    Rect keymap;      // top: the zone-segment band (the compact keymap)
+    Rect levelBand;   // bottom: the thin level/activity indicator
+};
+
+// Divide a (w x h) embed area into the strip's regions. Pure: same inputs -> same layout.
+// The level band takes a fixed height at the bottom (clamped so it never exceeds the area
+// or starves the keymap below kEmbedKeymapMinHeight); the keymap takes the rest. A zero or
+// negative size yields empty rects (no inversion).
+EmbedLayout layoutEmbed(int w, int h);
+
+// The horizontal sub-rectangle of the keymap band for a zone spanning [lowNote, highNote]
+// (inclusive). The 128-key span maps linearly across keymap.width(); the returned rect
+// spans the half-open pixel range [x(lowNote), x(highNote+1)) so adjacent zones (e.g.
+// 0..59 and 60..127) tile without a gap or overlap. Notes are clamped to [0,127] and low
+// is clamped to <= high, so a malformed zone yields an in-band (possibly zero-width) rect,
+// never an inverted one. Pure.
+Rect zoneSegmentRect(const EmbedLayout& layout, int lowNote, int highNote);
+
+// The zone a click at (x, y) lands on, given the zones in draw order, or -1 for a click
+// outside the keymap band or on a key not covered by any zone. When zones overlap on a
+// key, the FIRST covering zone in order wins — mirroring the sampler core's first-match
+// Keymap::resolve and the editor's zone order, so selection agrees with playback. Pure.
+int zoneAtPoint(const EmbedLayout& layout, const EmbedZone* zones, int zoneCount, int x,
+                int y);
+
+// The filled portion of the level band for a 0..1 level. Clamps level to [0,1]; the
+// returned rect is the left sub-rectangle of levelBand whose width is level * band width
+// (rounded down). level <= 0 -> empty rect; level >= 1 -> the whole band. Pure.
+Rect levelFillRect(const EmbedLayout& layout, double level);
+
+}  // namespace reasampler::vst

src/vst/keyboard_strip.cpp

@@ -0,0 +1,126 @@
+// keyboard_strip.cpp — see keyboard_strip.h. Pure math; no host types.
+
+#include "keyboard_strip.h"
+
+#include <algorithm>
+
+namespace reasampler::vst {
+
+namespace {
+
+int clampNote(int n) {
+    if (n < 0) return 0;
+    if (n > kStripKeyCount - 1) return kStripKeyCount - 1;
+    return n;
+}
+
+// Map a key BOUNDARY in [0, kStripKeyCount] to an x pixel inside a band of the given
+// left/width. keyEdge is a boundary (0..128): 0 -> band left, 128 -> band right. Integer
+// math, floored — key N's left is keyEdgeToX(N) and its right is keyEdgeToX(N+1), tiling
+// adjacent keys/zones without a seam (mirror of embed_strip::keyEdgeToX).
+int keyEdgeToX(int bandLeft, int bandWidth, int keyEdge) {
+    if (keyEdge <= 0) return bandLeft;
+    if (keyEdge >= kStripKeyCount) return bandLeft + bandWidth;
+    return bandLeft + (keyEdge * bandWidth) / kStripKeyCount;
+}
+
+}  // namespace
+
+StripLayout layoutStrip(int w, int h) {
+    const int cw = std::max(0, w);
+    const int ch = std::max(0, h);
+    StripLayout out;
+    out.keys = Rect{0, 0, cw, ch};
+    return out;
+}
+
+int keyLeftX(const StripLayout& layout, int note) {
+    const Rect& band = layout.keys;
+    const int bandWidth = std::max(0, band.width());
+    // note is a KEY here (0..127); its left edge is boundary `note`. Callers pass note+1 to
+    // get a key's right edge, and 128 maps to the band right.
+    const int edge = note < 0 ? 0 : (note > kStripKeyCount ? kStripKeyCount : note);
+    return keyEdgeToX(band.left, bandWidth, edge);
+}
+
+Rect keyRect(const StripLayout& layout, int note) {
+    const int n = clampNote(note);
+    const int leftX = keyLeftX(layout, n);
+    const int rightX = keyLeftX(layout, n + 1);
+    return Rect{leftX, layout.keys.top, std::max(leftX, rightX), layout.keys.bottom};
+}
+
+Rect rootMarkerRect(const StripLayout& layout, int rootNote) {
+    return keyRect(layout, rootNote);
+}
+
+int keyAtPoint(const StripLayout& layout, int x, int y) {
+    const Rect& band = layout.keys;
+    if (!contains(band, x, y)) return -1;
+    const int bandWidth = std::max(0, band.width());
+    if (bandWidth <= 0) return -1;
+    // Invert keyEdgeToX: the key whose half-open [leftX, rightX) contains x. Floor-divide
+    // the pixel offset back to a key; clamp defensively (a point on band.right-1 maps to 127).
+    const int offset = x - band.left;
+    int note = (offset * kStripKeyCount) / bandWidth;
+    return clampNote(note);
+}
+
+Rect zoneBarRect(const StripLayout& layout, int lowNote, int highNote) {
+    int lo = clampNote(lowNote);
+    int hi = clampNote(highNote);
+    if (lo > hi) lo = hi;  // defensive: a malformed zone collapses rather than inverts
+    const int leftX = keyLeftX(layout, lo);
+    const int rightX = keyLeftX(layout, hi + 1);
+    return Rect{leftX, layout.keys.top, std::max(leftX, rightX), layout.keys.bottom};
+}
+
+ZoneGrab zoneGrabAt(const StripLayout& layout, int lowNote, int highNote, int x, int y) {
+    const Rect bar = zoneBarRect(layout, lowNote, highNote);
+    if (!contains(bar, x, y)) return ZoneGrab::kNone;
+
+    const int barW = bar.width();
+    // A narrow bar (< 2*edge) has no body: split at the midpoint, LOW edge wins the tie so
+    // a click exactly on the midpoint resizes low (deterministic).
+    if (barW < 2 * kStripEdgeGrabWidth) {
+        const int mid = bar.left + barW / 2;
+        return x <= mid ? ZoneGrab::kLowEdge : ZoneGrab::kHighEdge;
+    }
+    if (x < bar.left + kStripEdgeGrabWidth) return ZoneGrab::kLowEdge;
+    if (x >= bar.right - kStripEdgeGrabWidth) return ZoneGrab::kHighEdge;
+    return ZoneGrab::kBody;
+}
+
+ZoneBarHit zoneBarAtPoint(const StripLayout& layout, const int* lows, const int* highs,
+                          int count, int x, int y) {
+    if (count <= 0 || lows == nullptr || highs == nullptr) return ZoneBarHit{};
+    if (!contains(layout.keys, x, y)) return ZoneBarHit{};
+    for (int i = 0; i < count; ++i) {
+        const ZoneGrab g = zoneGrabAt(layout, lows[i], highs[i], x, y);
+        if (g != ZoneGrab::kNone) return ZoneBarHit{i, g};
+    }
+    return ZoneBarHit{};  // on the band but on no bar
+}
+
+int resolveDragNote(const StripLayout& layout, int startNote, int dxPixels) {
+    if (dxPixels == 0) return clampNote(startNote);
+    const int bandWidth = std::max(0, layout.keys.width());
+    if (bandWidth <= 0) return clampNote(startNote);  // zero-width -> no motion
+    // Proportional shift: same linear mapping as keyAtPoint/keyEdgeToX so click and drag
+    // agree across the full strip, even on non-divisible-by-128 widths. The proportional
+    // key width is (bandWidth / kStripKeyCount) in exact rational arithmetic; rounding to
+    // the nearest key (half-key drag flips at the key centre) is achieved by adding
+    // bandWidth/2 to the absolute pixel delta before dividing — identical to the old
+    // formula except keyWidth is now derived from the same linear map (exact rational)
+    // rather than the truncated-integer bandWidth/128 that caused drift at the far end.
+    const int half = bandWidth / 2;
+    int shift;
+    if (dxPixels > 0) {
+        shift = (dxPixels * kStripKeyCount + half) / bandWidth;
+    } else {
+        shift = -(((-dxPixels) * kStripKeyCount + half) / bandWidth);
+    }
+    return clampNote(startNote + shift);
+}
+
+}  // namespace reasampler::vst

src/vst/keyboard_strip.h

@@ -0,0 +1,121 @@
+// keyboard_strip.h — PURE layout + hit-test + drag math for the S10 capture-first
+// editor's keyboard strip. NO VST3, NO REAPER, NO SWELL/LICE types at the boundary.
+// The mirror of editor_geometry / embed_strip / mode_switch: the fiddly rectangle +
+// note-mapping arithmetic lives here so it is unit-tested outside the DAW, while the
+// editor shell (reasampler_editor.cpp) draws the strip and marshals mouse events into
+// these functions.
+//
+// The strip maps the full 128-key MIDI span across a horizontal band (the same key-span
+// idiom embed_strip uses). It serves TWO faces of the S10 editor:
+//   * the SINGLE-CAPTURE fast path (default): one loaded capture with a ROOT MARKER on
+//     the strip, click-a-key (or drag the marker) sets the capture's root note; and
+//   * the opt-in ZONES panel (S10-Z, demoted): each performance zone drawn as a bar over
+//     the keys it covers, with edge-grab resize handles + a body move-handle so a drag
+//     sets low/high (edges) or moves the span (body), and a key-click sets the zone root.
+//
+// All interaction resolves through the pure DRAG-DELTA resolver here: the shell captures
+// a grab on WM_LBUTTONDOWN, feeds each WM_MOUSEMOVE's pixel delta back through
+// resolveDragNote, and commits the resolved note(s) on WM_LBUTTONUP. Live feedback is the
+// shell re-drawing the in-flight note; one coherent edit lands on release.
+//
+// It reuses the same Rect + contains() as editor_geometry (one shared geometry idiom),
+// so this header depends on editor_geometry.h rather than redefining a rectangle type.
+
+#pragma once
+
+#include "editor_geometry.h"  // Rect, contains — one shared geometry idiom
+
+namespace reasampler::vst {
+
+// The full MIDI key span the strip maps across its width: 128 keys (0..127). Named
+// distinctly from embed_strip's kEmbedKeyCount (same value) so the two strips stay
+// independent — the editor strip may grow octave labels/metrics the embed strip never does.
+inline constexpr int kStripKeyCount = 128;
+
+// The width (px) of an edge-grab hit region at each end of a zone bar: a drag started
+// within this many pixels of the bar's left/right edge resizes that edge; a drag started
+// anywhere else on the bar moves the whole span. A zone narrower than 2*this has no body
+// move-handle (both edges win their halves) — deliberate: a 1-key zone is all edges.
+inline constexpr int kStripEdgeGrabWidth = 6;
+
+// The strip's regions, derived from the (w x h) band the shell allots it. The keys band
+// takes the whole area today (a future octave-label lane can carve a sub-band here without
+// changing callers). Clamped so a degenerate (tiny/zero) size never yields an inverted rect.
+struct StripLayout {
+    Rect keys;  // the key band: the 128-key span maps linearly across keys.width()
+};
+
+// Divide a (w x h) strip area into its regions. Pure: same inputs -> same layout. A zero or
+// negative size yields empty rects (no inversion).
+StripLayout layoutStrip(int w, int h);
+
+// The x pixel (inside the keys band) of the LEFT edge of key `note` (0..127). The 128-key
+// span maps linearly across keys.width(); key N occupies the half-open pixel range
+// [keyLeftX(N), keyLeftX(N+1)). Notes are clamped to [0,127]; note==128 maps to the band's
+// right edge (so a key's right edge is keyLeftX(note+1)). Pure.
+int keyLeftX(const StripLayout& layout, int note);
+
+// The half-open pixel rect of a single key `note` (0..127): [keyLeftX(note),
+// keyLeftX(note+1)) horizontally, the full keys-band height. A malformed (out-of-range)
+// note clamps to [0,127]. Pure.
+Rect keyRect(const StripLayout& layout, int note);
+
+// The rect of the ROOT MARKER for the single-capture fast path: the key cell of `rootNote`,
+// drawn as a highlighted key. Equivalent to keyRect(layout, rootNote) — a named entry point
+// so the shell's intent (this is the root marker, not just any key) reads at the call site,
+// and so a future marker shape (a triangle over the key) has one place to change. Pure.
+Rect rootMarkerRect(const StripLayout& layout, int rootNote);
+
+// The MIDI note a point (x, y) lands on, or -1 for a point outside the keys band. Backs
+// click-to-set-root (single capture) and click-a-key-sets-zone-root (zones). Pure.
+int keyAtPoint(const StripLayout& layout, int x, int y);
+
+// The horizontal sub-rect of the keys band for a zone spanning [lowNote, highNote]
+// (inclusive): [keyLeftX(low), keyLeftX(high+1)) horizontally, the full band height. Notes
+// clamp to [0,127] and low clamps to <= high, so a malformed zone yields an in-band
+// (possibly zero-width) rect, never an inverted one. Mirrors embed_strip::zoneSegmentRect.
+// Pure.
+Rect zoneBarRect(const StripLayout& layout, int lowNote, int highNote);
+
+// Which part of a zone bar a grab landed on. The shell uses this to decide what a drag
+// edits: an edge resizes that boundary; the body moves the whole span; none means the grab
+// missed the bar entirely (the shell may treat that as a key-click to set the root, or as a
+// deselect).
+enum class ZoneGrab {
+    kNone,      // the point is not on this zone's bar
+    kLowEdge,   // within kStripEdgeGrabWidth of the bar's LEFT edge -> resize low
+    kHighEdge,  // within kStripEdgeGrabWidth of the bar's RIGHT edge -> resize high
+    kBody,      // on the bar but not an edge -> move the whole span
+};
+
+// Classify a grab at (x, y) against ONE zone's bar (low..high). Returns kNone when the
+// point is off the bar (or off the keys band). On the bar: kLowEdge/kHighEdge when within
+// kStripEdgeGrabWidth of that edge, else kBody. A narrow bar (< 2*kStripEdgeGrabWidth)
+// resolves the near half to each edge (no body). The LOW edge wins a tie at the exact
+// midpoint of a narrow bar (deterministic). Pure.
+ZoneGrab zoneGrabAt(const StripLayout& layout, int lowNote, int highNote, int x, int y);
+
+// The zone (index into `lows`/`highs`, draw order) whose bar a grab at (x, y) lands on,
+// plus which part of it, or {-1, kNone} for a point off every bar. First covering zone in
+// draw order wins (first-match, mirroring the core's Keymap::resolve + embed_strip). The
+// arrays are parallel (lows[i]/highs[i] is zone i's inclusive range); `count` is their
+// length. Pure — no host containers at the boundary (a raw pointer pair, like
+// embed_strip::zoneAtPoint).
+struct ZoneBarHit {
+    int zoneIndex = -1;
+    ZoneGrab grab = ZoneGrab::kNone;
+};
+ZoneBarHit zoneBarAtPoint(const StripLayout& layout, const int* lows, const int* highs,
+                          int count, int x, int y);
+
+// Resolve a drag to a new MIDI note. Given the note the grabbed field held at grab time
+// (`startNote`) and the horizontal pixel delta since grab (`dxPixels`), returns the note
+// the field should now hold: startNote shifted by round(dxPixels / keyWidth), clamped to
+// [0,127]. keyWidth is derived from the layout (band width / 128); a zero-width band pins
+// the result to startNote (no motion). This is the single arithmetic behind edge-resize,
+// body-move (apply to both edges with the SAME delta so the span is preserved), and
+// root-marker drag. Pure — rounding is to the nearest key so a half-key drag flips at the
+// key centre. Returns startNote unchanged for dxPixels==0.
+int resolveDragNote(const StripLayout& layout, int startNote, int dxPixels);
+
+}  // namespace reasampler::vst

src/vst/note_entry.cpp

@@ -0,0 +1,113 @@
+// note_entry.cpp — see note_entry.h. PURE text->MIDI-note parse for the S12 numeric entry.
+
+#include "note_entry.h"
+
+#include <algorithm>
+#include <cctype>
+
+namespace reasampler::vst {
+
+namespace {
+char asciiUpper(char c) {
+    return static_cast<char>(std::toupper(static_cast<unsigned char>(c)));
+}
+
+std::string trim(const std::string& s) {
+    std::size_t a = 0;
+    std::size_t b = s.size();
+    while (a < b && std::isspace(static_cast<unsigned char>(s[a]))) ++a;
+    while (b > a && std::isspace(static_cast<unsigned char>(s[b - 1]))) --b;
+    return s.substr(a, b - a);
+}
+
+int clampNote(long long n) {
+    if (n < 0) return 0;
+    if (n > 127) return 127;
+    return static_cast<int>(n);
+}
+
+// Semitone offset within an octave for a note letter (C..B), or -1 for a non-letter.
+int letterSemitone(char up) {
+    switch (up) {
+        case 'C': return 0;
+        case 'D': return 2;
+        case 'E': return 4;
+        case 'F': return 5;
+        case 'G': return 7;
+        case 'A': return 9;
+        case 'B': return 11;
+        default: return -1;
+    }
+}
+
+// Parse a note name like "C4", "F#3", "Bb-1" (case-insensitive). MIDI 0 == C-1, 60 == C4
+// (the DAW convention the editor's noteLabel uses). Returns nullopt if it is not a note name.
+std::optional<int> parseNoteName(const std::string& s) {
+    if (s.empty()) return std::nullopt;
+    std::size_t i = 0;
+    const int base = letterSemitone(asciiUpper(s[i]));
+    if (base < 0) return std::nullopt;  // not a letter -> not a note name
+    ++i;
+    int semitone = base;
+    // Optional accidental(s): # / b (or 's'/'f' are NOT accepted — keep it to the two glyphs).
+    while (i < s.size() && (s[i] == '#' || s[i] == 'b' || s[i] == 'B')) {
+        // A trailing 'b'/'B' could be a flat OR the start of nothing; here after a letter it is
+        // an accidental. '#' raises, 'b'/'B' lowers.
+        if (s[i] == '#') ++semitone;
+        else --semitone;
+        ++i;
+    }
+    // The octave: an optional sign then digits, running to the end.
+    if (i >= s.size()) return std::nullopt;  // a bare "C" has no octave -> reject (ambiguous)
+    bool neg = false;
+    if (s[i] == '+' || s[i] == '-') {
+        neg = (s[i] == '-');
+        ++i;
+    }
+    if (i >= s.size()) return std::nullopt;
+    int octave = 0;
+    bool anyDigit = false;
+    for (; i < s.size(); ++i) {
+        if (!std::isdigit(static_cast<unsigned char>(s[i]))) return std::nullopt;
+        octave = octave * 10 + (s[i] - '0');
+        anyDigit = true;
+    }
+    if (!anyDigit) return std::nullopt;
+    if (neg) octave = -octave;
+    // MIDI note = (octave + 1) * 12 + semitone  (C-1 == 0, C4 == 60).
+    const long long note = static_cast<long long>(octave + 1) * 12 + semitone;
+    return clampNote(note);
+}
+
+std::optional<int> parseInteger(const std::string& s) {
+    if (s.empty()) return std::nullopt;
+    std::size_t i = 0;
+    bool neg = false;
+    if (s[i] == '+' || s[i] == '-') {
+        neg = (s[i] == '-');
+        ++i;
+    }
+    if (i >= s.size()) return std::nullopt;
+    long long v = 0;
+    for (; i < s.size(); ++i) {
+        if (!std::isdigit(static_cast<unsigned char>(s[i]))) return std::nullopt;
+        v = v * 10 + (s[i] - '0');
+        if (v > 1000000) v = 1000000;  // saturate; clampNote takes it to 127 anyway
+    }
+    if (neg) v = -v;
+    return clampNote(v);
+}
+}  // namespace
+
+std::optional<int> parseNoteEntry(const std::string& text) {
+    const std::string s = trim(text);
+    if (s.empty()) return std::nullopt;
+    // Try a plain integer first (the common MIDI-number case); fall back to a note name.
+    if (std::isdigit(static_cast<unsigned char>(s[0])) || s[0] == '+' ||
+        (s[0] == '-' && s.size() > 1 && std::isdigit(static_cast<unsigned char>(s[1])))) {
+        if (auto n = parseInteger(s)) return n;
+    }
+    return parseNoteName(s);
+}
+
+}  // namespace reasampler::vst

src/vst/note_entry.h

@@ -0,0 +1,33 @@
+// note_entry.h — PURE parse + clamp for the S12 direct numeric entry of a zone's
+// low/high/root MIDI note. NO VST3, NO REAPER, NO SWELL/LICE types at the boundary. The
+// mirror of the other pure editor helpers: the fiddly text->note parse lives here, unit-
+// tested outside the DAW, while the editor shell hosts the text field (a SWELL edit control
+// or a LICE text-entry idiom) and feeds the committed string here on Enter.
+//
+// WHY IT EXISTS (S12). Low/high/root are draggable on the keyboard strip, but a drag can't
+// hit a precise note reliably. This adds a typed field: the user clicks the field, types a
+// value, and presses Enter; the shell hands the raw string here to parse into a clamped MIDI
+// note [0,127] and commits via the same off-thread reload as every other edit.
+//
+// ACCEPTED FORMS (both, so a musician OR a MIDI-number user is served):
+//   * a plain decimal integer ("60", " 127 ", "+5") — the raw MIDI note number; and
+//   * a note name ("C4", "f#3", "Bb-1") — parsed to its MIDI number under the DAW's C4==60
+//     convention (MIDI 0 == C-1, matching REAPER + the editor's noteLabel).
+// A value out of [0,127] CLAMPS to the range (a typed 200 becomes 127) rather than
+// rejecting — the least-surprising behavior for a nudge field. Unparseable input returns
+// nullopt (the shell keeps the old value + may flash the field).
+
+#pragma once
+
+#include <optional>
+#include <string>
+
+namespace reasampler::vst {
+
+// Parse a typed low/high/root field into a clamped MIDI note [0,127]. Accepts a decimal
+// integer OR a note name (see the header notes). Leading/trailing ASCII whitespace is
+// ignored. An in-range parse returns the note; an out-of-range numeric or note value clamps
+// into [0,127]; empty or unparseable input returns nullopt (no change). Pure — no host types.
+std::optional<int> parseNoteEntry(const std::string& text);
+
+}  // namespace reasampler::vst

src/vst/param_slider.cpp

@@ -0,0 +1,92 @@
+// param_slider.cpp — see param_slider.h. PURE control-surface geometry for the S12/S15/S16
+// editor parameter panel. No host types; only the shared Rect + contains().
+
+#include "param_slider.h"
+
+#include <algorithm>
+
+namespace reasampler::vst {
+
+std::vector<ControlRow> layoutControls(const Rect& panel,
+                                       const std::vector<ControlDesc>& controls) {
+    std::vector<ControlRow> out;
+    if (controls.empty() || panel.width() <= 0 || panel.height() <= 0) return out;
+    out.reserve(controls.size());
+
+    // The label column is clamped so a narrow panel still leaves a control column.
+    const int labelW = (std::min)(kControlLabelWidth, (std::max)(0, panel.width() / 2));
+    int rowTop = panel.top;
+    for (const ControlDesc& d : controls) {
+        ControlRow r;
+        r.id = d.id;
+        r.kind = d.kind;
+        const int rowBottom = rowTop + kControlRowHeight;
+        r.row = Rect{panel.left, rowTop, panel.right, rowBottom};
+        r.label = Rect{panel.left, rowTop, panel.left + labelW, rowBottom};
+        r.control = Rect{panel.left + labelW, rowTop, panel.right, rowBottom};
+        out.push_back(r);
+        rowTop = rowBottom + kControlRowGap;
+    }
+    return out;
+}
+
+Rect toggleSegmentRect(const Rect& control, int seg) {
+    if (seg < 0 || seg >= kToggleSegments) return Rect{};
+    const int w = control.width();
+    if (w <= 0 || control.height() <= 0) return Rect{};
+    const int segW = w / kToggleSegments;
+    const int left = control.left + seg * segW;
+    // The last segment absorbs the width remainder so the segments tile the whole control.
+    const int right = (seg == kToggleSegments - 1) ? control.right : left + segW;
+    return Rect{left, control.top, right, control.bottom};
+}
+
+int toggleSegmentHitTest(const Rect& control, int x, int y) {
+    if (!contains(control, x, y)) return -1;
+    for (int seg = 0; seg < kToggleSegments; ++seg) {
+        if (contains(toggleSegmentRect(control, seg), x, y)) return seg;
+    }
+    return -1;
+}
+
+Rect sliderTrackRect(const Rect& control) {
+    // Inset a half-handle at each end so the handle stays fully inside the control at value
+    // 0 and 1. The handle CENTER ranges across [track.left, track.right].
+    const int half = kSliderHandleWidth / 2;
+    if (control.width() <= kSliderHandleWidth || control.height() <= 0) return Rect{};
+    return Rect{control.left + half, control.top, control.right - half, control.bottom};
+}
+
+Rect sliderHandleRect(const Rect& control, double value) {
+    const Rect track = sliderTrackRect(control);
+    if (track.width() <= 0) return Rect{};
+    if (value < 0.0) value = 0.0;
+    if (value > 1.0) value = 1.0;
+    const int span = track.width();  // handle-center movable span
+    const int centerX = track.left + static_cast<int>(value * span + 0.5);
+    const int half = kSliderHandleWidth / 2;
+    return Rect{centerX - half, control.top, centerX - half + kSliderHandleWidth,
+                control.bottom};
+}
+
+double valueAtPoint(const Rect& control, int x) {
+    const Rect track = sliderTrackRect(control);
+    const int span = track.width();
+    if (span <= 0) return 0.0;
+    if (x <= track.left) return 0.0;
+    if (x >= track.right) return 1.0;
+    return static_cast<double>(x - track.left) / static_cast<double>(span);
+}
+
+int controlAtPoint(const std::vector<ControlRow>& rows, int x, int y) {
+    for (const ControlRow& r : rows) {
+        if (r.kind == ControlKind::Toggle) {
+            if (contains(r.control, x, y)) return r.id;
+        } else {  // Slider — the interactive area is the track
+            if (contains(sliderTrackRect(r.control), x, y)) return r.id;
+        }
+    }
+    return -1;
+}
+
+}  // namespace reasampler::vst

src/vst/param_slider.h

@@ -0,0 +1,104 @@
+// param_slider.h — PURE control-surface layout + hit-test + value<->pixel mapping for the
+// S12/S15/S16 editor parameter panel. NO VST3, NO REAPER, NO SWELL/LICE types at the
+// boundary, and — deliberately — NO sampler_core / sample_map engine types either. The
+// mirror of keyboard_strip / waveform_view / mode_switch: the fiddly slider-track and
+// toggle-segment arithmetic lives here, unit-tested outside the DAW, while the editor shell
+// draws each row (label + track/segments + handle) and routes clicks/drags into these
+// functions, owning the control-id -> engine-param binding + the value DOMAIN mapping.
+//
+// WHY IT EXISTS (S12 + the S15/S16 control surfaces deferred here). The setup / Zones surface
+// grows a stack of parameter controls: the S15 play-mode toggle (Gate|Trigger), the AHDSR
+// amp-envelope sliders (attack/hold/decay/sustain/release), the Trigger %-length + fade
+// controls, the S16 Varispeed|Preserve engine toggle, and the AD pitch-envelope
+// enable/attack/decay/depth. They are two shapes only — a two-segment TOGGLE and a
+// horizontal SLIDER — laid out as a vertical stack of fixed-height rows. This module lays out
+// that stack and maps a slider's NORMALIZED value (0..1) to/from its handle pixel; the shell
+// converts each control's engine value (frames, seconds, a fraction, a signed semitone
+// depth) to/from that 0..1 with its own domain knowledge (this module stays engine-free so it
+// tests without the audio core).
+//
+// It reuses editor_geometry's Rect + contains() (one shared geometry idiom).
+
+#pragma once
+
+#include <vector>
+
+#include "editor_geometry.h"  // Rect, contains — one shared geometry idiom
+
+namespace reasampler::vst {
+
+// Fixed control-panel metrics, exposed so the shell and tests agree.
+inline constexpr int kControlRowHeight = 22;   // one control row (incl. its inter-row gap)
+inline constexpr int kControlRowGap = 4;        // vertical gap below each row
+inline constexpr int kControlLabelWidth = 92;   // the label column at the row's left
+inline constexpr int kSliderHandleWidth = 8;    // the draggable slider handle width (px)
+inline constexpr int kToggleSegments = 2;       // a toggle is always two segments
+
+// A control is one of two shapes. Toggle = a two-segment selector (the active segment
+// highlights); Slider = a horizontal track with a draggable handle over a 0..1 value.
+enum class ControlKind { Toggle, Slider };
+
+// One control the shell places in the panel, in stack order. `id` is the shell's own control
+// identifier (an int the shell casts from its ControlId enum) returned by the hit-test so the
+// shell routes the interaction to the right engine param — this module never interprets it.
+struct ControlDesc {
+    int id = 0;
+    ControlKind kind = ControlKind::Slider;
+};
+
+// The laid-out geometry of one control row: its full row rect plus the interactive sub-rect
+// (the track for a Slider, the whole control area for a Toggle — the shell splits a Toggle
+// into segments via toggleSegmentRect). `index` is the control's position in the stack.
+struct ControlRow {
+    int id = 0;
+    ControlKind kind = ControlKind::Slider;
+    Rect row;      // the full row (label column + control column)
+    Rect label;    // the label column at the left
+    Rect control;  // the control column to the right of the label (track / toggle area)
+};
+
+// Lay out `controls` as a vertical stack of fixed-height rows inside `panel`, top-down. Each
+// row is kControlRowHeight tall with kControlRowGap below it; the label column takes the left
+// kControlLabelWidth (clamped so it never exceeds the panel), the control column the rest. A
+// row whose top falls past the panel bottom is still returned (the shell clips at paint /
+// suppresses it) so the stack geometry is deterministic regardless of panel height. An empty
+// control list or a degenerate panel yields an empty vector. Pure.
+std::vector<ControlRow> layoutControls(const Rect& panel,
+                                       const std::vector<ControlDesc>& controls);
+
+// The rect of segment `seg` (0..kToggleSegments-1) within a toggle control's `control` rect,
+// splitting it into kToggleSegments equal segments left-to-right (the last absorbs any width
+// remainder, mirror of mode_switch's segment split). An out-of-range segment or a degenerate
+// control rect yields an empty rect. Pure.
+Rect toggleSegmentRect(const Rect& control, int seg);
+
+// The toggle segment a point lands on within a toggle control's `control` rect, or -1 for a
+// miss (outside the control area). Pure.
+int toggleSegmentHitTest(const Rect& control, int x, int y);
+
+// The slider track sub-rect inside a slider control's `control` rect: the control inset so the
+// handle (kSliderHandleWidth) stays fully within the control at value 0 and 1 (a half-handle
+// margin at each end). The handle CENTER ranges across [track.left, track.right] as the value
+// ranges [0,1]. The shell draws the track fill + handle here. A degenerate control yields an
+// empty rect. Pure.
+Rect sliderTrackRect(const Rect& control);
+
+// The handle rect for a slider at normalized `value` (clamped to [0,1]) within `control`: a
+// kSliderHandleWidth-wide bar centered at the value's position along sliderTrackRect. A
+// degenerate control yields an empty rect. Pure — the inverse of valueAtPoint.
+Rect sliderHandleRect(const Rect& control, double value);
+
+// Map a point x to a normalized slider value [0,1] within `control` (the handle-center range).
+// x at/left of the track start -> 0; at/right of the end -> 1; linear between. A degenerate
+// track (zero movable span) -> 0. Pure — the inverse of sliderHandleRect's position map; the
+// shell converts the returned 0..1 into its engine domain (frames/seconds/fraction/semitones).
+double valueAtPoint(const Rect& control, int x);
+
+// The control a point lands on, given the laid-out `rows`. Returns the control id (ControlDesc
+// id) whose interactive area (a Slider's track, a Toggle's whole control area) contains the
+// point, or -1 for a miss (a gap, the label column, or outside every row). The FIRST matching
+// row wins (rows never overlap, so at most one matches). Pure — the shell's routing entry
+// point: on a hit it reads the value (valueAtPoint / toggleSegmentHitTest) and commits.
+int controlAtPoint(const std::vector<ControlRow>& rows, int x, int y);
+
+}  // namespace reasampler::vst

src/vst/pitch_shift.cpp

@@ -0,0 +1,126 @@
+// pitch_shift — pure implementation. See pitch_shift.h for the contract and the S16-F2
+// route-(b) rationale (WDL drags <windows.h>, so the Preserve DSP is house-native here).
+// NO VST3 / REAPER / SWELL / vendor includes; standard library only.
+//
+// Algorithm: a single delay ring of `window_` frames. The write head advances one frame per
+// input sample (source rate → duration preserved). TWO read taps chase the write head, offset
+// by half a window; each advances by the shift `ratio_` per frame. A tap that would cross the
+// write head wraps by a full window (so it stays a bounded delay behind the writer). The two
+// taps are crossfaded by an equal-power window keyed to each tap's distance from the write
+// head, so the wrap discontinuity of one tap is masked by the other mid-window — the classic
+// two-grain time-domain pitch shifter, no FFT.
+
+#include "pitch_shift.h"
+
+#include <algorithm>
+#include <cmath>
+
+namespace reasampler {
+
+namespace {
+
+// A Hann OLA window over a grain phase in [0,1): 0.5(1 - cos(2*pi*phase)). Zero at the grain
+// ends (where a tap wraps — the discontinuity), unity mid-grain. Two grains offset by half a
+// window PARTITION UNITY (w(p) + w(p+0.5) == 1 for all p), so the two crossfaded taps sum to a
+// gain of exactly 1 everywhere — no amplitude ripple across the window, and each tap's wrap
+// seam is masked because its window is 0 exactly there.
+double hannWeight(double phase) {
+    while (phase < 0.0) phase += 1.0;
+    while (phase >= 1.0) phase -= 1.0;
+    return 0.5 * (1.0 - std::cos(2.0 * 3.14159265358979323846 * phase));
+}
+
+}  // namespace
+
+void PitchShifter::configure(std::int64_t windowFrames) {
+    window_ = windowFrames;
+    if (window_ <= 1) {
+        // Pass-through: no ring, process() returns input unchanged.
+        ring_.clear();
+        writePos_ = 0;
+        readPos_ = 0.0;
+        ratio_ = 1.0;
+        return;
+    }
+    ring_.assign(static_cast<std::size_t>(window_), 0.0f);
+    reset();
+}
+
+void PitchShifter::reset() {
+    if (window_ > 1) {
+        // Zero the ring and seed the read head a half-window behind the writer so the two taps
+        // (readPos_ and readPos_ + window/2) straddle the writer from the first frame.
+        std::fill(ring_.begin(), ring_.end(), 0.0f);
+        writePos_ = 0;
+        readPos_ = static_cast<double>(window_) / 2.0;
+    } else {
+        writePos_ = 0;
+        readPos_ = 0.0;
+    }
+    ratio_ = 1.0;
+}
+
+void PitchShifter::warm() {
+    if (window_ <= 1) return;  // pass-through needs no warm-up
+    // Push one full window of silence so the taps reach steady state before real audio.
+    for (std::int64_t i = 0; i < window_; ++i) process(0.0f);
+}
+
+void PitchShifter::setShiftRatio(double ratio) {
+    if (ratio > 0.0) ratio_ = ratio;  // ignore non-positive (never run taps backward/stall)
+}
+
+AudioSample PitchShifter::process(AudioSample in) {
+    if (window_ <= 1) return in;  // pass-through (unconfigured / degenerate)
+
+    // 1. Write the incoming sample at the write head (source rate).
+    ring_[static_cast<std::size_t>(writePos_)] = in;
+
+    const double w = static_cast<double>(window_);
+    const double half = w / 2.0;
+
+    // 2. Read the two taps, each a bounded delay behind the writer. tap0 is `readPos_`; tap1 is
+    //    a half-window ahead of it (mod window). Distance-from-writer drives the crossfade so a
+    //    tap near the writer (about to wrap) is faded out while its partner (mid-window) is up.
+    auto readTap = [&](double pos) -> double {
+        // Fractional linear interpolation with ring wrap.
+        double p = pos;
+        while (p < 0.0) p += w;
+        while (p >= w) p -= w;
+        const std::int64_t i0 = static_cast<std::int64_t>(p);
+        const double frac = p - static_cast<double>(i0);
+        std::int64_t i1 = i0 + 1;
+        if (i1 >= window_) i1 = 0;
+        const double s0 = static_cast<double>(ring_[static_cast<std::size_t>(i0)]);
+        const double s1 = static_cast<double>(ring_[static_cast<std::size_t>(i1)]);
+        return s0 + (s1 - s0) * frac;
+    };
+
+    const double tap0 = readTap(readPos_);
+    const double tap1 = readTap(readPos_ + half);
+
+    // Distance of tap0 behind the write head, in [0, window). Its crossfade phase is that
+    // distance over the window; tap1 (half a window offset) gets the complementary phase.
+    double dist0 = static_cast<double>(writePos_) - readPos_;
+    while (dist0 < 0.0) dist0 += w;
+    while (dist0 >= w) dist0 -= w;
+    const double phase0 = dist0 / w;
+
+    // Hann windows offset by half a grain partition unity, so the two taps sum to gain 1 with
+    // each tap's wrap seam masked by its window zero. phase0 drives tap0; tap1 (half-window
+    // offset) is at phase0 + 0.5.
+    const double g0 = hannWeight(phase0);
+    const double g1 = hannWeight(phase0 + 0.5);
+    const double out = tap0 * g0 + tap1 * g1;
+
+    // 3. Advance heads: write head one frame (source rate), read head by the shift ratio.
+    ++writePos_;
+    if (writePos_ >= window_) writePos_ = 0;
+    readPos_ += ratio_;
+    while (readPos_ >= w) readPos_ -= w;
+    while (readPos_ < 0.0) readPos_ += w;
+
+    return static_cast<AudioSample>(out);
+}
+
+}  // namespace reasampler

src/vst/pitch_shift.h

@@ -0,0 +1,88 @@
+#pragma once
+// pitch_shift — a PURE, per-voice, duration-preserving pitch shifter: the S16 "Preserve"
+// engine's DSP core. Time-domain overlap-add (OLA) with two half-window-offset read taps
+// crossfaded to hide the ring-wrap seam. Source is consumed 1:1 and output produced 1:1
+// (duration held); only the PITCH changes — an octave up plays the same wall-clock length
+// as the root note, unlike the Varispeed `readPos_ += ratio_` resample path.
+//
+// WHY A HAND-ROLLED PURE MODULE, NOT WDL (S16-F2, decided at build). The spec's lean was
+// route (a) `WDL_SimplePitchShifter`. But its include chain
+// (simple_pitchshift.h -> queue.h -> heapbuf.h -> wdltypes.h) does `#ifdef _WIN32 ->
+// #include <windows.h>` unconditionally, which CANNOT enter the pure sampler_core module
+// (CLAUDE.md load-bearing split: NO vendor/host/SDK types; sampler_core_tests links neither
+// SDK and compiles outside the DAW). So the Preserve DSP lands as route (b): a house-native
+// pure module alongside peaks / wav_trim, CTest-testable, RT-disciplined. Same
+// PitchEngine::Preserve contract behind the seam — if WDL is ever preferred it swaps in at
+// the SHELL, never in the pure core.
+//
+// PURE MODULE: NO VST3, NO REAPER, NO SWELL, NO vendor/ includes. Standard library only.
+// Shares the `AudioSample` float alias from peaks (the one house precedent — sampler_core /
+// wav_trim do the same).
+//
+// RT DISCIPLINE (S16 hard constraint). `configure()` sizes the ring ONCE (off the audio
+// thread, at voice allocation). `warm()` pre-fills the ring with silence so steady-state
+// latency is reached before the first real sample (no cold-start click). `process()` does
+// NO allocation and NO locks — it reads/writes the pre-sized ring only. All state is plain
+// value fields, so a voice owning one by value costs a fixed ring buffer per channel.
+
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+#include "peaks.h"  // AudioSample (float)
+
+namespace reasampler {
+
+// A per-channel time-domain OLA pitch shifter. One instance transposes ONE channel; a stereo
+// voice owns two (or a stereo-aware wrapper) — the algorithm is per-sample and channel-count
+// agnostic, matching the S7 "one read head, per-channel value" idiom of the core.
+//
+// The default-constructed shifter is INERT: with no configure() it passes input through
+// unchanged (shift ratio 1.0, empty ring), so a Varispeed voice that never touches it is
+// byte-identical to the pre-S16 engine.
+class PitchShifter {
+public:
+    // Size the delay ring for `windowFrames` (the OLA grain length) and prepare the two
+    // read taps a half-window apart. `windowFrames` <= 1 degrades to pass-through (no ring),
+    // so a degenerate configure never divides by zero or wraps a zero span. Called OFF the
+    // audio thread (allocates). Resets all running state. A larger window = smoother on large
+    // transpositions but more latency; the shell picks it from the Preserve quality setting.
+    void configure(std::int64_t windowFrames);
+
+    // Pre-fill the ring with silence (one full window of zero writes) so the read taps reach
+    // steady state before the first real sample. Removes the cold-start seam (the S16 "onset
+    // click absent" requirement) — call once at voice allocation after configure(). No-op when
+    // unconfigured (pass-through needs no warm-up).
+    void warm();
+
+    // The pitch shift ratio: 2^((note - root)/12) plus any per-frame pitch-envelope bias.
+    // 1.0 = no shift (pass-through-equivalent output). Set per frame is fine (cheap); the tap
+    // advance simply uses the current value. Values <= 0 are ignored (kept at the last valid
+    // ratio) so a bad input never runs the taps backward or stalls them.
+    void setShiftRatio(double ratio);
+
+    // Transform ONE input frame into ONE output frame (duration-preserving: 1 in, 1 out).
+    // RT-safe: reads/writes the pre-sized ring only, no allocation, no lock. When unconfigured
+    // (window <= 1) returns `in` unchanged (pass-through). Otherwise writes `in` at the write
+    // head, reads the two half-window-offset taps advancing at the shift ratio, crossfades
+    // them by the write-head-relative distance (equal-power), and advances both heads by one.
+    AudioSample process(AudioSample in);
+
+    // Reset running state to a freshly-warmed-equivalent silence (ring zeroed, heads re-seeded)
+    // WITHOUT reallocating — for voice reuse without a re-configure. Keeps the current window.
+    void reset();
+
+    // True once configure() sized a real ring (window > 1). A pass-through shifter is false.
+    bool configured() const { return window_ > 1; }
+
+    std::int64_t window() const { return window_; }
+
+private:
+    std::vector<AudioSample> ring_;  // delay line, length `window_` (channel-local)
+    std::int64_t window_ = 0;        // OLA grain length in frames; <= 1 = pass-through
+    std::int64_t writePos_ = 0;      // integer write head into the ring (source rate)
+    double readPos_ = 0.0;           // fractional read head (advances at shift ratio)
+    double ratio_ = 1.0;             // current shift ratio (>0)
+};
+
+}  // namespace reasampler

src/vst/reaper_bridge.cpp

@@ -0,0 +1,112 @@
+// reaper_bridge.cpp — see reaper_bridge.h. The DAW-facing edge; keep it thin.
+
+#include "reaper_bridge.h"
+
+#include <vector>
+
+#include "bridge_marshal.h"
+#include "capture_paths.h"  // projectDirOfRpp (shared M4 project-dir derivation)
+#include "ext_keys.h"       // kProjExtNamespace (shared wire contract)
+
+// The VST3 base types must be included before REAPER's VST3 interface header, which
+// uses FUnknown / CStringA / uint32 / DECLARE_CLASS_IID / PLUGIN_API from
+// pluginterfaces/base — all in namespace Steinberg.
+#include "pluginterfaces/base/funknown.h"
+#include "pluginterfaces/base/ftypes.h"
+
+// REAPER's VST3-side bridge interface (vendored). IReaperHostApplication is what REAPER
+// passes (as an IHostApplication) to IComponent::initialize; it exposes getReaperApi
+// (resolve-by-name) and getReaperParent (host context). The header uses UNQUALIFIED
+// Steinberg types (FUnknown, CStringA, uint32, FUID, DECLARE_CLASS_IID, PLUGIN_API), so
+// it must be pulled into the Steinberg namespace — the same way REAPER's own VST3
+// examples include it.
+namespace Steinberg {
+#include "reaper_vst3_interfaces.h"
+}  // namespace Steinberg
+
+// DECLARE_CLASS_IID in the REAPER header only DECLARES IReaperHostApplication::iid; some
+// TU must DEFINE it. We do it here — this is the only place that queries for the
+// interface (FUnknownPtr uses the iid), so the definition lives with its sole use.
+DEF_CLASS_IID(Steinberg::IReaperHostApplication)
+
+// The ext-state namespace is the SHARED wire contract between the extension (writer)
+// and this instrument (reader); it lives in ext_keys.h (pure, REAPER-free) —
+// reasampler::kProjExtNamespace() — so the two artifacts read one symbol and cannot
+// drift. Channel-derived (Phase V, V4): the accessor returns "reasampler" (stable) or
+// "reasampler_beta" (beta), matching whatever the extension wrote. The S1 spike
+// duplicated it locally; that duplication is retired.
+
+namespace reasampler::vst {
+
+bool ReaperBridge::connect(Steinberg::FUnknown* context) {
+    getProjExtState_ = nullptr;
+    enumProjExtState_ = nullptr;
+    enumProjects_ = nullptr;
+    hostApp_ = nullptr;
+    if (!context) return false;
+
+    // Query the host context for REAPER's bridge interface. In a non-REAPER host this
+    // query fails and we stay unconnected — the instrument still loads.
+    Steinberg::FUnknownPtr<Steinberg::IReaperHostApplication> reaper(context);
+    if (!reaper) return false;
+    hostApp_ = reaper.get();
+
+    // Resolve the ext-state functions by name. getReaperApi returns the same function
+    // pointers the extension resolves via rec->GetFunc; a null return means the symbol
+    // is unavailable (very old REAPER) — degrade gracefully.
+    getProjExtState_ = reinterpret_cast<GetProjExtStateFn>(
+        reaper->getReaperApi("GetProjExtState"));
+    enumProjExtState_ = reinterpret_cast<EnumProjExtStateFn>(
+        reaper->getReaperApi("EnumProjExtState"));
+    // EnumProjects(-1, ...) yields the active project AND its .rpp path — the same call
+    // persist.cpp uses, so the instrument derives the project directory identically.
+    enumProjects_ = reinterpret_cast<EnumProjectsFn>(
+        reaper->getReaperApi("EnumProjects"));
+
+    return getProjExtState_ != nullptr;
+}
+
+std::optional<std::string> ReaperBridge::readReasamplerExtState(const std::string& key) {
+    if (!getProjExtState_ || !hostApp_) return std::nullopt;
+
+    // Fetch the host project (getReaperParent(3) — project). Reads that live "reasampler"
+    // ext-state against the ACTIVE project the instrument was instantiated in, so it
+    // follows project switches for free (D6).
+    auto* reaper = static_cast<Steinberg::IReaperHostApplication*>(hostApp_);
+    void* proj = reaper->getReaperParent(3);
+    // A null project is legitimate (e.g. instantiated before a project context exists);
+    // REAPER treats null as the current project for these calls, so we pass it through
+    // rather than bailing — but if the read yields nothing the caller sees nullopt.
+
+    // GetProjExtState writes into a caller buffer; the bank blob can be large (many
+    // samples), so grow the buffer until the value fits rather than risk a silent
+    // truncation — mirrors persist.cpp's getProjExtStateString growing strategy. The
+    // return value is the value length; if it fits strictly inside the buffer it is
+    // complete, else grow and retry up to a 16 MB ceiling.
+    for (int cap = 1 << 16; cap <= (1 << 24); cap <<= 2) {
+        std::vector<char> buf(static_cast<std::size_t>(cap), '\0');
+        const int rv = getProjExtState_(proj, kProjExtNamespace(), key.c_str(),
+                                        buf.data(), cap);
+        if (rv <= 0) return std::nullopt;  // absent / empty key
+        std::string s(buf.data());
+        if (static_cast<int>(s.size()) + 1 < cap) {
+            return decodeGetProjExtState(rv, s);
+        }
+        // else: possibly truncated -> grow and retry.
+    }
+    return std::nullopt;  // pathologically large (>16 MB) — give up rather than loop
+}
+
+std::string ReaperBridge::activeProjectDir() {
+    if (!enumProjects_) return {};
+    // idx=-1 is the current project tab; the out-buffer receives the full .rpp path,
+    // EMPTY for a never-saved project. Same call + convention as persist.cpp; the pure
+    // projectDirOfRpp turns the .rpp path into the project directory (parent, forward-
+    // slashed) and keeps an unsaved project's empty path empty (no default-location
+    // fallback — the tool's invariant).
+    std::vector<char> buf(4096, '\0');
+    enumProjects_(-1, buf.data(), static_cast<int>(buf.size()));
+    return projectDirOfRpp(std::string(buf.data()));
+}
+
+}  // namespace reasampler::vst

src/vst/reaper_bridge.h

@@ -0,0 +1,79 @@
+// reaper_bridge.h — the REAPER VST-host bridge (Phase S1 read spike). THIN shell:
+// resolves REAPER API functions by name over the host context and reads the live
+// "reasampler" project ext-state. The fiddly decode lives in bridge_marshal (pure).
+//
+// VERIFIED BRIDGE MECHANISM (corrects §1a's estimate). §1a described the VST2-style
+// hostcb opcode pattern (hostcb(&effect, 0xdeadbeef, 0xdeadf00d, ...)). That is the
+// VST2 path (video_processor.h documents it for a VST2 aEffect). For a VST3 plugin the
+// bridge is exposed differently and more cleanly: REAPER passes an IHostApplication as
+// the `context` to IComponent::initialize(FUnknown* context); querying it for
+// IReaperHostApplication (vendor/reaper-sdk/sdk/reaper_vst3_interfaces.h) yields:
+//   * getReaperApi(funcname) -> resolve a REAPER API function pointer by name
+//     (the VST3 equivalent of opcode 0xdeadf00d), and
+//   * getReaperParent(3)     -> the host ReaProject* (the VST3 equivalent of the
+//     0xdeadf00e host-context fetch; 1=track, 2=take, 3=project, 4=fxdsp, 5=trackchan).
+// So a VST3 uses IReaperHostApplication, not the raw hostcb opcodes. Verified against
+// reaper_vst3_interfaces.h + reaper_plugin_functions.h at the spike.
+
+#pragma once
+
+#include <optional>
+#include <string>
+
+#include "pluginterfaces/base/funknown.h"
+
+namespace reasampler::vst {
+
+// Wraps the REAPER host bridge for a single plugin instance. Constructed cheaply;
+// connect() must be called with the initialize() context before any read. All reads
+// degrade to nullopt (never crash) when the host is not REAPER or a symbol is absent —
+// the instrument must load in non-REAPER hosts too, just without live state.
+class ReaperBridge {
+public:
+    ReaperBridge() = default;
+
+    // Bind to the host. `context` is the FUnknown* REAPER hands IComponent::initialize.
+    // Returns true when the REAPER bridge is available (host is REAPER and the ext-state
+    // API resolved). Safe to call with a null or non-REAPER context — returns false.
+    bool connect(Steinberg::FUnknown* context);
+
+    // True once connect() found the REAPER host application AND resolved the ext-state
+    // functions.
+    bool isConnected() const { return getProjExtState_ != nullptr; }
+
+    // Read a "reasampler" ext-state value by key from the host's active project.
+    // Returns nullopt when unconnected, when the project can't be resolved, or when the
+    // key is absent. This is the S1 read-spike entry point.
+    //
+    // NOT REAL-TIME SAFE (it allocates a read buffer and calls into REAPER): callers on
+    // the audio thread MUST NOT invoke it. The S4 instrument reads on the main/UI thread
+    // and hands a snapshot to the process path (see reasampler_processor.cpp).
+    std::optional<std::string> readReasamplerExtState(const std::string& key);
+
+    // The active project's directory (the folder holding its .rpp), forward-slashed,
+    // no trailing slash — the M4 convention persist uses to place the bank alongside
+    // the .rpp. Empty for an unsaved project or when unconnected. The instrument
+    // resolves relative sample paths against this the SAME way persist does
+    // (capture_paths::projectDirOfRpp over EnumProjects(-1)'s .rpp path). Not RT-safe.
+    std::string activeProjectDir();
+
+private:
+    // Resolved REAPER API function pointers (by name via getReaperApi). Signatures
+    // verified against reaper_plugin_functions.h.
+    using GetProjExtStateFn = int (*)(void* proj, const char* extname, const char* key,
+                                      char* valOutNeedBig, int valOutNeedBig_sz);
+    using EnumProjExtStateFn = bool (*)(void* proj, const char* extname, int idx,
+                                        char* keyOut, int keyOut_sz, char* valOut,
+                                        int valOut_sz);
+    // EnumProjects(-1, projfnOut, sz) -> active project + its .rpp path (SDK line
+    // ~1264). The instrument uses idx=-1 (current tab) so it follows the active project,
+    // and reads the .rpp path from the out-buffer exactly as persist.cpp does.
+    using EnumProjectsFn = void* (*)(int idx, char* projfnOut, int projfnOut_sz);
+
+    void* hostApp_ = nullptr;  // IReaperHostApplication* (opaque here; used in .cpp)
+    GetProjExtStateFn getProjExtState_ = nullptr;
+    EnumProjExtStateFn enumProjExtState_ = nullptr;
+    EnumProjectsFn enumProjects_ = nullptr;
+};
+
+}  // namespace reasampler::vst

src/vst/reasampler_editor.h

@@ -0,0 +1,280 @@
+// reasampler_editor.h — the VST3 IPlugView LICE editor for the ReaSampler 9000
+// capture-first UI (Phase S10). THIN shell: hosts a LICE-drawn child window inside the
+// host's IPlugView seat and routes host paint/mouse into the pure geometry modules
+// (capture_browser, keyboard_strip) + the pure mapping (sample_map). Windows-only (D5).
+//
+// The default face is the CAPTURE BROWSER: a bank-filter tab strip over a grid of
+// scannable capture cards (peak thumbnail + name + root/key badge). A fresh instance with
+// no pick shows a "pick a capture" EMPTY STATE and plays silence (the S10 policy reversal
+// of the S4 first-sample auto-play). Picking a card loads that one capture and reveals a
+// guided SINGLE-CAPTURE SETUP surface (a keyboard strip with the capture's root marker +
+// a level readout). Multi-zone keymap editing is a demoted, opt-in ZONES panel (S10-Z),
+// reached by a toggle and driven by the same keyboard_strip drag machine.
+//
+// All layout/hit-test/drag math lives in the pure modules; this shell only draws + routes
+// (a LICE_SysBitmap blitted in WM_PAINT, a WM_LBUTTONDOWN/WM_MOUSEMOVE/WM_LBUTTONUP
+// drag-state machine hit-testing via the pure resolvers). Peak thumbnails are computed
+// shell-side from the decoded WAV (bank_model's Sample carries no envelope) and cached —
+// the mirror of bank_panel::thumbnailFor. Every edit commits OFF the audio thread via the
+// processor's reloadFromBank (RT path untouched).
+//
+// Subclasses CPluginView for the IPlugView boilerplate; overrides the attach/remove hooks
+// to create/destroy the child window and onSize to resize it.
+
+#pragma once
+
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include "public.sdk/source/common/pluginview.h"
+
+#include "editor_geometry.h"  // Rect (the shell's sub-rect type, shared with the pure modules)
+#include "param_slider.h"     // ControlRow (the S12/S15/S16 control-surface geometry)
+#include "peaks.h"            // Envelope (the cached peak thumbnail)
+#include "sample_map.h"       // SampleChoice, BankChoice, PerformanceMap (the shell's snapshot)
+
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
+class LICE_IBitmap;  // fwd: the paint helpers take one; lice.h is included only in the .cpp
+
+namespace reasampler::vst {
+
+class ReaSamplerProcessor;
+
+class ReaSamplerEditor : public Steinberg::CPluginView {
+public:
+    // `processor` owns this editor's lifetime domain and outlives it; the editor reads the
+    // live bank through it and drives selection/zone edits + reload on user input. May be
+    // null (defensive — a real host always supplies one).
+    explicit ReaSamplerEditor(ReaSamplerProcessor* processor);
+    ~ReaSamplerEditor() override;
+
+    Steinberg::tresult PLUGIN_API isPlatformTypeSupported(
+        Steinberg::FIDString type) override;
+    Steinberg::tresult PLUGIN_API canResize() override;
+
+protected:
+    void attachedToParent() override;
+    void removedFromParent() override;
+    Steinberg::tresult PLUGIN_API onSize(Steinberg::ViewRect* newSize) override;
+
+private:
+    // Which face the editor shows. The browser is the default; the Zones panel is the
+    // demoted opt-in view reached by the toggle. Both draw over the same snapshotted bank.
+    enum class View { kBrowser, kZones };
+
+    // What a mouse drag is currently editing (the drag-state machine). kNone = no drag in
+    // flight. The zone-edit grabs mirror keyboard_strip::ZoneGrab; kRootMarker is the
+    // single-capture root drag on the setup strip; kWaveMarker is a draggable start/loop
+    // marker on the S11 waveform surface (which marker is in waveMarker_).
+    enum class DragKind { kNone, kRootMarker, kZoneLow, kZoneHigh, kZoneBody, kWaveMarker,
+                          kScrollThumb, kParamSlider };
+
+    // The parameter controls on the setup surface (S12 AHDSR + the S15/S16 control surfaces).
+    // The int value is the ControlDesc id the pure param_slider hit-test returns; the shell
+    // maps it to the picked zone's play params. Order here is the panel's top-down stack order.
+    enum class ParamControl {
+        kPlayMode = 0,   // Gate | Trigger toggle (S15)
+        kPitchEngine,    // Varispeed | Preserve toggle (S16)
+        kAttack,         // AHDSR attack   (Gate)  / —
+        kHold,           // AHDSR hold     (Gate, S15)
+        kDecay,          // AHDSR decay    (Gate)
+        kSustain,        // AHDSR sustain  (Gate)
+        kRelease,        // AHDSR release  (Gate)
+        kTrigLength,     // Trigger %-length (Trigger, S15)
+        kTrigFadeIn,     // Trigger fade-in  (Trigger, S15)
+        kTrigFadeOut,    // Trigger fade-out (Trigger, S15)
+        kPitchEnvEnable, // AD pitch envelope on|off (S16)
+        kPitchEnvAttack, // AD pitch attack (S16)
+        kPitchEnvDecay,  // AD pitch decay  (S16)
+        kPitchEnvDepth,  // AD pitch depth in +/- semitones (S16)
+        kCount
+    };
+
+    // The waveform markers on the single-capture setup surface (S11). Order is the draw + hit
+    // order (start first). Named generically per the spec so S15 can repurpose the surface with
+    // a different marker set; here it is start-point + the sustain loop's two ends.
+    enum class WaveMarker { kStart = 0, kLoopStart = 1, kLoopEnd = 2, kCount = 3 };
+
+#ifdef _WIN32
+    void paint(HDC hdc);
+    void paintBrowser(LICE_IBitmap* bmp, int w, int h);
+    void paintSetup(LICE_IBitmap* bmp, const Rect& area);
+    void paintZones(LICE_IBitmap* bmp, int w, int h);
+    void paintEmptyState(LICE_IBitmap* bmp, const Rect& area);
+    void paintControls(LICE_IBitmap* bmp, const Rect& panel);  // S12/S15/S16 param surface
+
+    void onMouseDown(int x, int y);
+    void onMouseMove(int x, int y);
+    void onMouseUp(int x, int y);
+    void onMouseWheel(int delta);           // S12 browser scroll (wheel)
+    void onSearchChar(unsigned int ch);     // S12 type-to-filter search keystroke
+
+    // S13 (relay degraded): an OS file drop landed on the editor window. We do NOT ingest (the
+    // instrument is a read-only bank consumer and the relay is unshipped) — we flash the "drop
+    // on the ReaSampler panel to add" affordance so the drop is never silently swallowed and the
+    // shipped ingest gesture stays discoverable. `droppedCount` is how many files were dropped
+    // (drawn into the banner). NEVER inserts a timeline item / never touches the bank.
+    void onFilesDropped(int droppedCount);
+
+    // The S9/S8 change-detection tick (WM_TIMER on the child window — the UI thread, NEVER the
+    // audio thread). Polls the processor's bank-sync (generation change -> hands-free reload;
+    // a new assignment request -> apply as this instance's selection) and, when anything
+    // changed, re-snapshots the editor's own view (refreshFromBank) + repaints so the browser /
+    // setup surface reflect the new bank. An open editor means THIS instance is the focused
+    // assignment target (the thundering-herd policy — see the handoff), so it passes true.
+    // Suppressed WHILE A DRAG IS IN FLIGHT so a mid-drag reload does not yank the edit surface.
+    void onSyncTimer();
+
+    static LRESULT CALLBACK wndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
+    void invalidate();
+
+    HWND childHwnd_ = nullptr;
+#endif
+
+    // Re-read the bank (samples + banks) from the live bridge and snapshot the instrument's
+    // selection + performance map. Main/UI thread only. Called on attach and after any edit.
+    void refreshFromBank();
+
+    // Publish the edited zones/selection to the processor, then rebuild the instrument OFF
+    // the audio thread. UI thread only. One place so every edit commits identically.
+    void commitAndReload();
+
+    // Recompute the capture cards visible under the current bank filter (samples_ narrowed by
+    // activeFilterBankId_; "" = All) into visible_. Called on refresh + filter change.
+    void rebuildVisible();
+
+    // The peak thumbnail for a bank sample id at `binCount` bins, computed once from the
+    // decoded WAV (mirror of bank_panel::thumbnailFor) and cached by (id, binCount). Returns
+    // an empty envelope when the WAV can't be resolved/decoded. UI thread only (file I/O).
+    const Envelope& thumbnailFor(const std::string& sampleId, int binCount);
+
+    // The decoded MONO PCM for a bank sample id, decoded once from the WAV and cached by id.
+    // Feeds the S11 waveform surface: the full-res envelope binned at view width AND the
+    // zero-crossing snap (both need the raw frames, not the binned thumbnail). Returns an empty
+    // vector when the WAV can't be resolved/decoded. UI thread only (file I/O). Reuses the same
+    // decode path as thumbnailFor (no new WAV reader), keyed by id (not width — snap is width-
+    // independent). Cleared with the thumbnail cache on refresh.
+    const std::vector<AudioSample>& monoPcmFor(const std::string& sampleId);
+
+    // The effective loop + start markers for the picked single capture (S11): the per-zone
+    // OVERRIDE for the picked id when one exists in map_, else the bank's S2 loop intrinsic
+    // (loop) / frame 0 (start). Absent loop -> loopStart==loopEnd==0 (the "no loop" state).
+    // frames is the decoded length (for defaulting loopEnd when the bank left the loop empty).
+    struct SetupMarkers {
+        std::int64_t start = 0;
+        std::int64_t loopStart = 0;
+        std::int64_t loopEnd = 0;
+        bool hasLoop = false;  // whether a sustain loop is set (drives the "no loop" affordance)
+    };
+    SetupMarkers pickedMarkers(std::int64_t frames) const;
+
+    // Commit an edited marker set for the picked capture as a per-zone loop/start override
+    // (upsert on the picked id — mirror of the root-marker path), then reload off-thread.
+    void commitPickedMarkers(const SetupMarkers& m);
+
+    // Write `m` as a loop/start override upsert into map_ for selectedId_ (find-or-append).
+    // Does NOT call commitAndReload — callers decide whether this is a live-drag update or a
+    // final commit. selectedId_ must be non-empty before calling. Returns the zone index
+    // (0-based) that was updated or appended, so callers can set selectedZone_.
+    int upsertPickedOverride(const SetupMarkers& m);
+
+    // --- S12/S15/S16 parameter surface (Zones panel, keyed to selectedZone_) ------
+    //
+    // The control panel edits the SELECTED zone's ZonePlaySeconds (S15 play mode + AHDSR; S16
+    // pitch engine + AD pitch envelope). Wall-clock times are SECONDS (rate-free); the keymap
+    // build resolves them to frames at the live rate. Instrument-owned (D-B), never a bank fact.
+
+    // The control descriptors the panel shows for `play`'s CURRENT play mode: the two toggles +
+    // the mode-relevant sliders (AHDSR for Gate, %-length/fades for Trigger) + the pitch-envelope
+    // controls. The pure param_slider lays these out; this only picks the set. Static (a free
+    // choice of set from the mode) — kept a member for the ParamControl enum access.
+    std::vector<ControlDesc> controlDescs(const ZonePlaySeconds& play) const;
+
+    // The normalized [0,1] display value for control `id` given `play` (the shell's domain
+    // mapping: seconds->0..1 over a fixed seconds ceiling, sustain 0..1 as-is, %-length/fade
+    // frames->0..1, semitone depth centered at 0.5).
+    double controlValue(int id, const ZonePlaySeconds& play) const;
+
+    // Apply a committed control interaction to `play`: a slider's normalized `value` (mapped back
+    // into the control's stored domain) or a toggle's `segment` (0/1). Mutates `play` in place.
+    void applyControl(int id, ZonePlaySeconds& play, double value, int segment) const;
+
+    ReaSamplerProcessor* processor_ = nullptr;
+
+    // --- Snapshot of the live bank (drawn each paint; refreshed off the audio thread) ---
+    std::vector<SampleChoice> samples_;   // every bank sample, bank order
+    std::vector<BankChoice> banks_;       // the named banks, for the filter tab strip
+    std::vector<SampleChoice> visible_;   // samples_ narrowed by the active bank filter
+    std::string selectedId_;              // the single-capture pick ("" = empty state)
+    PerformanceMap map_;                  // the opt-in zones (empty = no zones)
+    ChannelMode channelMode_ = ChannelMode::Mono;  // S7 mono/stereo toggle snapshot
+
+    // --- Transient UI state (not persisted; component state carries selection + zones) ---
+    View view_ = View::kBrowser;          // default face is the browser
+    std::string activeFilterBankId_;      // "" = All; else a bank id from banks_
+    int selectedZone_ = -1;               // highlighted zone in the Zones panel; -1 = none
+
+    // --- S13 drop-to-load affordance (relay DEGRADED — transient, never persisted) ----
+    // S13's cross-artifact ingest relay (editor drop -> extension ingest) is NOT shipped: the
+    // instrument's REAPER bridge is deliberately READ-ONLY (it never writes the bank / ext
+    // state), so an editor drop cannot relay a bank-ingest request without a new write seam +
+    // an extension-side poller (surfaced as a decision, not crossed here). The DEGRADE path per
+    // the spec: the editor ACCEPTS the drop (WM_DROPFILES) and, rather than silently swallowing
+    // it, flashes a clear affordance pointing at the shipped ingest gesture (drop onto the
+    // docked ReaSampler panel). When > 0, the affordance banner is shown; each sync tick decays
+    // it so it auto-dismisses. No file is ingested, no timeline item is ever inserted.
+    int dropHintTicks_ = 0;               // remaining sync ticks to show the drop affordance
+
+    // --- S12 browser scroll + search (transient UI state, never persisted) --------
+    int scrollOffset_ = 0;                // vertical px offset into the card grid (clamped)
+    std::string searchQuery_;             // type-to-filter narrow; "" = no search
+    bool searchFocused_ = false;          // whether the search box has keyboard focus
+
+    // --- S12 numeric note entry (LICE text-entry idiom, transient) ----------------
+    // When >= 0, a low/high/root field is being typed; entryText_ accumulates the keystrokes
+    // and commits (parseNoteEntry) on Enter. -1 = no field editing. The field id is a
+    // ParamControl-independent small enum encoded inline (see the .cpp: 0=low,1=high,2=root).
+    int entryField_ = -1;
+    std::string entryText_;
+
+    // --- Drag-state machine ------------------------------------------------------
+    DragKind drag_ = DragKind::kNone;
+    int dragStartX_ = 0;                  // grab x (px), for the pixel-delta resolver
+    int dragStartY_ = 0;                  // grab y (px), for the vertical scrollbar-thumb drag
+    int dragStartLow_ = 0;                // the grabbed field's note at grab time
+    int dragStartHigh_ = 0;
+    int dragStartRoot_ = 60;
+    PerformanceMap dragStartMap_;         // map_ snapshotted at grab; restored on capture-loss
+
+    // S11 waveform-marker drag: which marker + the marker set snapshotted at grab time (so the
+    // pixel-delta resolver shifts the grabbed frame from its grab-time value, and inter-marker
+    // clamps use the sibling markers).
+    WaveMarker waveMarker_ = WaveMarker::kStart;
+    SetupMarkers dragStartMarkers_;
+    std::int64_t dragSampleFrames_ = 0;   // decoded length of the sample under the drag
+
+    // S12 scrollbar-thumb drag: the offset held at grab time (the pixel-delta resolver shifts
+    // from it). S12/S15/S16 param-slider drag: which control id + the panel it lives in (the
+    // shell re-lays the panel each move to map x->value against the live control rect).
+    int dragStartScrollOffset_ = 0;
+    int dragParamId_ = -1;
+    Rect dragParamPanel_{};
+
+    // --- Peak-thumbnail cache (mirror of bank_panel; id -> envelope at a bin width) ------
+    // Keyed by "id|binCount" so a resize recomputes at the new width. Cleared on refresh so
+    // a bank edit (a re-captured or deleted sample) does not show a stale thumbnail.
+    std::unordered_map<std::string, Envelope> thumbCache_;
+
+    // --- Decoded mono-PCM cache (S11; id -> full-res frames) ------------------------------
+    // Keyed by id (width-independent, unlike thumbCache_). Feeds the waveform envelope binning
+    // + the zero-crossing snap. Cleared alongside thumbCache_ on refresh so a re-captured or
+    // deleted sample does not show/snap against stale PCM.
+    std::unordered_map<std::string, std::vector<AudioSample>> pcmCache_;
+};
+
+}  // namespace reasampler::vst

src/vst/reasampler_embed.cpp

@@ -0,0 +1,264 @@
+// reasampler_embed.cpp — see reasampler_embed.h. The IReaperUIEmbedInterface shell.
+// Windows-only (D5); guarded so a non-Windows build degrades to a stub that reports
+// "not supported" and draws nothing.
+
+#include "reasampler_embed.h"
+
+#include <string>
+#include <vector>
+
+#include "app_version.h"      // vstPluginName (channel-derived embed label, S18)
+#include "bank_sync.h"        // parseBankGeneration (S9 dirty-guard over the per-paint refresh)
+#include "editor_geometry.h"  // Rect (shared with embed_strip)
+#include "embed_strip.h"      // the pure strip layout + hit-test
+#include "ext_keys.h"         // kProjExtBanksKey / kProjExtBankGenKey
+#include "reaper_bridge.h"
+#include "reasampler_processor.h"
+
+// wdltypes.h first: it defines INT_PTR portably (and pulls <windows.h> on Windows), which
+// reaper_plugin_fx_embed.h's REAPER_FXEMBED_IBitmap::Extended needs as its return type.
+#include "wdltypes.h"
+
+// REAPER's embed message/bitmap contract (vendored). REAPER_FXEMBED_IBitmap is an alias of
+// LICE_IBitmap, and the WM_* / DrawInfo / SizeHints definitions live here.
+#include "reaper_plugin_fx_embed.h"
+
+#ifdef _WIN32
+// LICE — the same drawing stack the IPlugView editor and bank_panel use. REAPER hands us a
+// LICE bitmap; we draw into it with the same calls, then return (REAPER blits it).
+#include "lice/lice.h"
+#endif
+
+using namespace Steinberg;
+
+// DECLARE_CLASS_IID in the REAPER header only DECLARES IReaperUIEmbedInterface::iid; some
+// TU must DEFINE it. This is the only place that answers queryInterface for it, so the
+// definition lives with its sole use (mirrors reaper_bridge.cpp doing this for
+// IReaperHostApplication).
+DEF_CLASS_IID(Steinberg::IReaperUIEmbedInterface)
+
+namespace reasampler::vst {
+
+namespace {
+#ifdef _WIN32
+// Palette — mirrored from reasampler_editor.cpp so the inline strip reads as the same tool.
+const LICE_pixel kColBackground = LICE_RGBA(28, 28, 30, 255);
+const LICE_pixel kColZone = LICE_RGBA(44, 44, 48, 255);
+const LICE_pixel kColZoneSel = LICE_RGBA(58, 96, 84, 255);
+const LICE_pixel kColZoneBorder = LICE_RGBA(20, 20, 22, 255);
+const LICE_pixel kColLevelBg = LICE_RGBA(20, 20, 22, 255);
+const LICE_pixel kColLevelFill = LICE_RGBA(120, 200, 160, 255);
+const LICE_pixel kColEmpty = LICE_RGBA(70, 70, 74, 255);
+const COLORREF kRgbText = RGB(210, 230, 220);
+
+// A short display name for a bank sample id, from the snapshotted list (the editor's helper,
+// duplicated small rather than shared across the shell/pure boundary).
+std::string sampleLabel(const std::vector<SampleChoice>& samples, const std::string& id) {
+    for (const SampleChoice& c : samples) {
+        if (c.id == id) return c.displayName.empty() ? c.id : c.displayName;
+    }
+    return "?";
+}
+#endif
+
+// Project the instrument's performance map into the strip's minimal zone shape (key ranges
+// only). Pure projection — kept here (shell side) because it reads PerformanceMap, a shell
+// type; embed_strip stays free of it.
+std::vector<EmbedZone> toEmbedZones(const PerformanceMap& map) {
+    std::vector<EmbedZone> out;
+    out.reserve(map.zones.size());
+    for (const PerformanceZone& z : map.zones) out.push_back(EmbedZone{z.lowNote, z.highNote});
+    return out;
+}
+
+}  // namespace
+
+tresult PLUGIN_API ReaSamplerEmbed::queryInterface(const TUID iid, void** obj) {
+    QUERY_INTERFACE(iid, obj, FUnknown::iid, IReaperUIEmbedInterface)
+    QUERY_INTERFACE(iid, obj, IReaperUIEmbedInterface::iid, IReaperUIEmbedInterface)
+    *obj = nullptr;
+    return kNoInterface;
+}
+
+void ReaSamplerEmbed::refresh() {
+    if (!processor_) {
+        samples_.clear();
+        map_.zones.clear();
+        selectedZone_ = -1;
+        return;
+    }
+    auto banks = processor_->bridge().readReasamplerExtState(reasampler::kProjExtBanksKey);
+    samples_ = banks ? listSamples(*banks) : std::vector<SampleChoice>{};
+    map_ = processor_->performanceMap();
+    if (selectedZone_ >= static_cast<int>(map_.zones.size())) selectedZone_ = -1;
+}
+
+void ReaSamplerEmbed::maybeRefresh() {
+    if (!processor_) { refresh(); return; }  // clears state; cheap
+
+    // The performance map is a cheap in-process accessor (mutex + copy), and the editor may
+    // have edited zones with NO bank-content change — always re-snapshot it so a zone edit
+    // reflects immediately.
+    map_ = processor_->performanceMap();
+    if (selectedZone_ >= static_cast<int>(map_.zones.size())) selectedZone_ = -1;
+
+    // The EXPENSIVE part is the bank-blob bridge read (samples_). Gate it on the S9 bank-
+    // generation stamp (a small ext-state read): only re-read the bank when the generation
+    // changed since the last paint (a recapture / ingest / remove), or on the first paint
+    // (lastSeenBankGeneration_ == -1). A pre-S9 project reads generation 0; the first paint
+    // folds it and subsequent idle paints skip the bank read entirely.
+    std::int64_t currentGen = lastSeenBankGeneration_;
+    if (auto rawGen =
+            processor_->bridge().readReasamplerExtState(reasampler::kProjExtBankGenKey)) {
+        currentGen = parseBankGeneration(*rawGen);
+    } else if (lastSeenBankGeneration_ < 0) {
+        currentGen = 0;  // unprimed + no stamp (pre-S9): treat as generation 0 for the first read
+    }
+    // Intentional asymmetry: a TRANSIENT bridge failure (readReasamplerExtState returned
+    // nullopt after we were already primed) leaves currentGen == lastSeenBankGeneration_,
+    // so the bank-blob read is skipped and the editor keeps its last-known sample list.
+    // A stale-but-intact list is better than clearing samples_ on every transient hiccup.
+
+    if (lastSeenBankGeneration_ < 0 || currentGen != lastSeenBankGeneration_) {
+        auto banks =
+            processor_->bridge().readReasamplerExtState(reasampler::kProjExtBanksKey);
+        samples_ = banks ? listSamples(*banks) : std::vector<SampleChoice>{};
+        lastSeenBankGeneration_ = currentGen;
+    }
+}
+
+TPtrInt ReaSamplerEmbed::embed_message(int msg, TPtrInt parm2, TPtrInt parm3) {
+    switch (msg) {
+        case REAPER_FXEMBED_WM_IS_SUPPORTED:
+#ifdef _WIN32
+            return 1;   // supported and available
+#else
+            return 0;   // not a build target off Windows
+#endif
+        case REAPER_FXEMBED_WM_CREATE:
+            refresh();  // prime the first paint's snapshot
+            return 0;
+        case REAPER_FXEMBED_WM_DESTROY:
+            return 0;
+        case REAPER_FXEMBED_WM_GETMINMAXINFO: {
+            auto* hints = reinterpret_cast<REAPER_FXEMBED_SizeHints*>(parm3);
+            if (!hints) return 0;
+            // Minimum usable strip height: the keymap must not collapse below its floor
+            // (kEmbedKeymapMinHeight) plus the level band.
+            hints->min_width  = 64;
+            hints->max_width  = 0;  // 0 = unconstrained
+            hints->min_height = kEmbedKeymapMinHeight + kEmbedLevelBandHeight;
+            hints->max_height = 0;  // 0 = unconstrained
+            // Preferred aspect: wide strip, roughly 8:1 (w:h). 16.16 fixed point.
+            hints->preferred_aspect = (8 << 16) / 1;
+            hints->minimum_aspect   = (4 << 16) / 1;
+            return 1;
+        }
+#ifdef _WIN32
+        case REAPER_FXEMBED_WM_PAINT:
+            return paint(parm2, parm3) ? 1 : 0;
+        case REAPER_FXEMBED_WM_LBUTTONDOWN:
+            // Selection at most (S6): map the click to a zone; force a redraw if it changed.
+            return onMouseDown(parm3) ? REAPER_FXEMBED_RETNOTIFY_INVALIDATE : 0;
+#endif
+        default:
+            return 0;   // unhandled messages (cursor, wheel, hittest) fall through
+    }
+}
+
+#ifdef _WIN32
+
+bool ReaSamplerEmbed::paint(TPtrInt bitmap, TPtrInt drawInfo) {
+    auto* bmp = reinterpret_cast<LICE_IBitmap*>(bitmap);
+    auto* di = reinterpret_cast<const REAPER_FXEMBED_DrawInfo*>(drawInfo);
+    if (!bmp || !di) return false;
+    const int w = di->width;
+    const int h = di->height;
+    if (w <= 0 || h <= 0) return false;
+
+    // Re-read live state each paint (UI thread) so the strip reflects keymap edits + bank
+    // changes without its own timer — REAPER repaints the embed surface on its cadence. S9
+    // dirty-guard: maybeRefresh does the EXPENSIVE bank-blob read only when the bank generation
+    // changed (the flagged S6 follow-up), always refreshing the cheap performance map.
+    maybeRefresh();
+
+    // REAPER hands us its own bitmap sized to the embed area; draw directly into it (unlike
+    // the editor, which owns a LICE_SysBitmap and BitBlt's). Origin is the bitmap's (0,0).
+    LICE_FillRect(bmp, 0, 0, w, h, kColBackground, 1.0f, 0);
+
+    const EmbedLayout layout = layoutEmbed(w, h);
+
+    if (map_.zones.empty()) {
+        // No opt-in zones authored: show a single faint band spanning the keymap area so the
+        // strip reads as "present, no zones" — the default single-capture face lives in the
+        // editor (this S6 strip mirrors the zones map only).
+        LICE_FillRect(bmp, layout.keymap.left, layout.keymap.top, layout.keymap.width(),
+                      layout.keymap.height(), kColEmpty, 0.5f, 0);
+        HDC dc = bmp->getDC();
+        SetBkMode(dc, TRANSPARENT);
+        SetTextColor(dc, kRgbText);
+        RECT gr{layout.keymap.left + 4, layout.keymap.top, layout.keymap.right,
+                layout.keymap.bottom};
+        const std::string label = reasampler::vstPluginName() +  // channel-derived (S18)
+            (samples_.empty() ? " (bank empty)" : " (no zones)");
+        DrawTextA(dc, label.c_str(), -1, &gr,
+                  DT_LEFT | DT_VCENTER | DT_SINGLELINE | DT_NOPREFIX);
+    } else {
+        // Draw each zone as a segment across the keymap span, first-match order (so the
+        // painted order matches selection + playback). The selected zone is highlighted.
+        for (int i = 0; i < static_cast<int>(map_.zones.size()); ++i) {
+            const PerformanceZone& z = map_.zones[i];
+            const Rect r = zoneSegmentRect(layout, z.lowNote, z.highNote);
+            if (r.width() <= 0) continue;
+            const bool sel = (i == selectedZone_);
+            LICE_FillRect(bmp, r.left, r.top, r.width(), r.height(),
+                          sel ? kColZoneSel : kColZone, 1.0f, 0);
+            LICE_DrawRect(bmp, r.left, r.top, r.width() - 1, r.height() - 1, kColZoneBorder,
+                          1.0f, 0);
+            // Label the segment with the sample name when it is wide enough to read.
+            if (r.width() >= 24) {
+                HDC dc = bmp->getDC();
+                SetBkMode(dc, TRANSPARENT);
+                SetTextColor(dc, kRgbText);
+                RECT gr{r.left + 3, r.top, r.right - 2, r.bottom};
+                const std::string label = sampleLabel(samples_, z.sampleId);
+                DrawTextA(dc, label.c_str(), -1, &gr,
+                          DT_LEFT | DT_VCENTER | DT_SINGLELINE | DT_NOPREFIX | DT_END_ELLIPSIS);
+            }
+        }
+    }
+
+    // The level band: a static background here; a live activity level is a later refinement
+    // (the processor would publish a peak the UI thread reads). Draw the empty band so the
+    // strip's geometry is complete and the DAW-verify sees the band lifecycle now.
+    if (layout.levelBand.height() > 0) {
+        LICE_FillRect(bmp, layout.levelBand.left, layout.levelBand.top,
+                      layout.levelBand.width(), layout.levelBand.height(), kColLevelBg, 1.0f,
+                      0);
+        const double level = processor_ ? processor_->embedActivityLevel() : 0.0;
+        const Rect fill = levelFillRect(layout, level);
+        if (fill.width() > 0) {
+            LICE_FillRect(bmp, fill.left, fill.top, fill.width(), fill.height(),
+                          kColLevelFill, 1.0f, 0);
+        }
+    }
+
+    return true;
+}
+
+bool ReaSamplerEmbed::onMouseDown(TPtrInt drawInfo) {
+    auto* di = reinterpret_cast<const REAPER_FXEMBED_DrawInfo*>(drawInfo);
+    if (!di || di->width <= 0 || di->height <= 0) return false;
+    refresh();
+    const EmbedLayout layout = layoutEmbed(di->width, di->height);
+    const std::vector<EmbedZone> zones = toEmbedZones(map_);
+    const int hit = zoneAtPoint(layout, zones.data(), static_cast<int>(zones.size()),
+                                di->mouse_x, di->mouse_y);
+    if (hit == selectedZone_) return false;  // no change -> no redraw
+    selectedZone_ = hit;
+    return true;
+}
+
+#endif  // _WIN32
+
+}  // namespace reasampler::vst

src/vst/reasampler_embed.h

@@ -0,0 +1,112 @@
+// reasampler_embed.h — the S6 embedded TCP/MCP UI shell. Implements REAPER's
+// IReaperUIEmbedInterface (vendor/reaper-sdk/sdk/reaper_plugin_fx_embed.h +
+// reaper_vst3_interfaces.h) so the instrument draws a compact keymap/level strip INLINE in
+// the track/mixer control panel — the same Cockos surface REAPER's own embedded FX use.
+//
+// VERIFIED CONTRACT (against reaper_plugin_fx_embed.h + reaper_vst3_interfaces.h):
+//   * VST3 exposes this by having the IEditController answer queryInterface for
+//     IReaperUIEmbedInterface (iid {0x049bf9e7,0xbc74ead0,0xc4101e86,0x7f725981}). Our
+//     SingleComponentEffect IS the edit controller, so the processor's queryInterface hands
+//     REAPER a reference to this object.
+//   * The single method is embed_message(int msg, TPtrInt parm2, TPtrInt parm3). msg is a
+//     REAPER_FXEMBED_WM_* value (aliased to Win32 WM_*):
+//       - WM_IS_SUPPORTED (0x0000): return 1 (supported+available), -1, or 0.
+//       - WM_CREATE (0x0001) / WM_DESTROY (0x0002): embed begin/end; return ignored.
+//       - WM_PAINT (0x000F): parm2 = REAPER_FXEMBED_IBitmap* (alias LICE_IBitmap) to draw
+//         into; parm3 = REAPER_FXEMBED_DrawInfo* (context TCP=1/MCP=2, width/height, mouse,
+//         flags). Return 1 if drawing occurred, 0 otherwise.
+//       - WM_GETMINMAXINFO (0x0024): parm3 = SizeHints*; return 1 if filled.
+//       - mouse WM_* (0x0200..0x020A): parm3 = DrawInfo*; return RETNOTIFY_INVALIDATE
+//         (0x1000000) to force a redraw. Capture is auto-managed by the host.
+//   * There is NO plugin-owned window/HWND here (unlike the IPlugView editor): REAPER hands
+//     a LICE bitmap per paint; we only draw into it and read mouse coords from DrawInfo.
+//
+// RT DISCIPLINE (S6 constraint): all embed messages arrive on REAPER's UI thread; nothing
+// here runs in process(). It reads the same live state the editor reads (bank over the
+// bridge + the processor's performance map) with the same off-audio-thread accessors — no
+// new locks visible to process, read-only over the bank. Windows-only (D5), guarded so a
+// non-Windows build stays compilable.
+//
+// The strip's LAYOUT + HIT-TEST is pure (embed_strip.h, unit-tested); this shell marshals
+// REAPER's messages to/from it and draws with the same LICE idiom as reasampler_editor.
+
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+#include "pluginterfaces/base/funknown.h"
+
+#include "sample_map.h"  // SampleChoice, PerformanceMap (the state the strip reflects)
+
+// REAPER's VST3-side embed interface (vendored). Uses UNQUALIFIED Steinberg types, so it is
+// pulled into the Steinberg namespace the same way reaper_bridge.cpp includes the host
+// interface header. Its iid is DEFINEd (DEF_CLASS_IID) in reasampler_embed.cpp.
+namespace Steinberg {
+#include "reaper_vst3_interfaces.h"
+}  // namespace Steinberg
+
+namespace reasampler::vst {
+
+class ReaSamplerProcessor;
+
+// Implements IReaperUIEmbedInterface. Lifetime is OWNED by the processor (the processor
+// holds the sole unique_ptr and hands out AddRef'd references from queryInterface); the
+// back-pointer to the processor is therefore always valid while this lives.
+class ReaSamplerEmbed : public Steinberg::IReaperUIEmbedInterface {
+public:
+    explicit ReaSamplerEmbed(ReaSamplerProcessor* processor) : processor_(processor) {}
+
+    // The one embed entry point. Routes each REAPER_FXEMBED_WM_* message; see the header
+    // note above for the per-message contract. UI thread only.
+    Steinberg::TPtrInt embed_message(int msg, Steinberg::TPtrInt parm2,
+                                     Steinberg::TPtrInt parm3) override;
+
+    // FUnknown: this object's lifetime is owned by the processor, not the host refcount, so
+    // AddRef/release are no-ops (the processor's unique_ptr governs destruction) and
+    // queryInterface answers only FUnknown + IReaperUIEmbedInterface. This mirrors how the
+    // SDK's OBJ refcount would otherwise churn; here the owning processor guarantees the
+    // object outlives every borrowed reference REAPER holds during embedding.
+    Steinberg::tresult PLUGIN_API queryInterface(const Steinberg::TUID iid,
+                                                 void** obj) override;
+    Steinberg::uint32 PLUGIN_API addRef() override { return 1000; }
+    Steinberg::uint32 PLUGIN_API release() override { return 1000; }
+
+private:
+#ifdef _WIN32
+    // Draw the current strip into REAPER's supplied LICE bitmap. Returns true if it drew.
+    bool paint(Steinberg::TPtrInt bitmap, Steinberg::TPtrInt drawInfo);
+    // Handle a mouse-down inside the strip: map to a zone and select it (S6: selection at
+    // most — no new editing semantics). Returns true if the selection changed (the caller
+    // then asks REAPER to invalidate).
+    bool onMouseDown(Steinberg::TPtrInt drawInfo);
+#endif
+
+    // Snapshot the live bank + the instrument's performance map for the next paint, exactly
+    // as the editor's refreshSampleList does (bridge read + processor accessors, UI thread).
+    void refresh();
+
+    // The S9 dirty-guard over refresh() (the S6 flagged follow-up): read the cheap bank-
+    // generation stamp; do the EXPENSIVE bank-blob bridge read (refresh()) only when the
+    // generation changed since the last paint (or on the first paint) — the strip re-read
+    // per paint was wasteful now that a generation counter exists. The performance map (a
+    // cheap in-process accessor, edited by the editor independently of bank content) is
+    // ALWAYS refreshed so a zone edit still reflects immediately. UI thread only.
+    void maybeRefresh();
+
+    ReaSamplerProcessor* processor_ = nullptr;
+    // The bank generation last folded into samples_ (S9 dirty-guard). -1 forces the first
+    // maybeRefresh() to do a full read (no generation can be negative — parseBankGeneration
+    // yields >= 0 — so -1 is an "unprimed" sentinel distinct from a real generation 0).
+    std::int64_t lastSeenBankGeneration_ = -1;
+    // Snapshotted for the current paint (refreshed each paint off the audio thread).
+    std::vector<SampleChoice> samples_;
+    PerformanceMap map_;
+    // The zone the last click selected (local/visual only — S6 selection constraint; the
+    // processor's editor-shared selection is NOT updated from here); -1 = none.
+    // Drives the strip's highlight.
+    int selectedZone_ = -1;
+};
+
+}  // namespace reasampler::vst

src/vst/reasampler_processor.cpp

@@ -0,0 +1,610 @@
+// reasampler_processor.cpp — see reasampler_processor.h.
+
+#include "reasampler_processor.h"
+
+#include <algorithm>
+#include <cstdint>
+#include <fstream>
+#include <optional>
+#include <utility>
+#include <vector>
+
+#include "pluginterfaces/base/ibstream.h"
+#include "pluginterfaces/vst/ivstaudioprocessor.h"
+#include "pluginterfaces/vst/ivsteditcontroller.h"  // RestartFlags::kIoChanged (S7 re-negotiate)
+#include "pluginterfaces/vst/ivstevents.h"
+#include "pluginterfaces/vst/vstspeaker.h"
+
+#include "public.sdk/source/vst/vstbus.h"  // Vst::AudioBus::setArrangement (S7 output arr)
+
+#include "assignment_request.h"  // decodeAssignmentRequest (S8 request wire parse)
+#include "bank_sync.h"       // S9/S8 pure decisions: parseBankGeneration, consumeDecision
+#include "capture_paths.h"   // resolveBankFile (shared M4 path resolution)
+#include "ext_keys.h"        // kProjExtBanksKey / kProjExtBankGenKey / kProjExtAssignKey (shared wire contract)
+#include "reasampler_editor.h"
+#include "reasampler_embed.h"  // S6 embed shell + IReaperUIEmbedInterface (its iid DEF'd there)
+#include "sample_map.h"       // selectSample, resolvePerformance, buildZonedKeymap, state (de)ser
+#include "wav_trim.h"         // parseWavLayout, extractFloatFrames (shared WAV parse)
+
+using namespace Steinberg;
+using namespace Steinberg::Vst;
+
+namespace reasampler::vst {
+
+namespace {
+
+// Tier-0 fixed instrument shape (Tier 2 makes these editable). A gentle amp envelope so
+// notes neither click on nor cut off abruptly; sustain at unity (velocity does the
+// dynamics), a short release for a natural tail. Times are in seconds, converted to
+// frames against the live sample rate at build time.
+constexpr std::size_t kMaxVoices = 16;
+
+// S16 Preserve-mode voice cap: a Preserve voice runs a per-voice OLA pitch shifter and is
+// materially heavier than a Varispeed voice. Below the Varispeed polyphony bound so a chord of
+// Preserve notes stays within the RT budget; a Preserve note-on past the cap is dropped rather
+// than glitching (Varispeed notes are unaffected). Set from the measured/estimated per-voice
+// cost — see the handoff CPU note. 8 is a conservative half of kMaxVoices pending DAW profiling.
+constexpr std::size_t kPreserveVoiceCap = 8;
+
+// Read a whole file into a byte buffer. Off-thread only (blocking file I/O). Empty on
+// any failure — the caller treats an unreadable WAV as "nothing to play".
+std::vector<std::uint8_t> readFileBytes(const std::string& path) {
+    std::vector<std::uint8_t> bytes;
+    std::ifstream f(path, std::ios::binary | std::ios::ate);
+    if (!f) return bytes;
+    const std::streamoff size = f.tellg();
+    if (size <= 0) return bytes;
+    f.seekg(0, std::ios::beg);
+    bytes.resize(static_cast<std::size_t>(size));
+    if (!f.read(reinterpret_cast<char*>(bytes.data()), size)) bytes.clear();
+    return bytes;
+}
+
+// Resolve a project-relative WAV path (the M4 way persist does), read + decode it (file
+// I/O — off-thread only), and apply the S7 cross-mode channel policy for `mode`: mono mode
+// downmixes to one channel (existing policy); stereo mode yields two channels (dual-mono for
+// a mono source, L/R for a stereo source) — see decodeChannels. Returns nullopt when the path
+// fails to resolve, the file is unreadable, the WAV is malformed, or the decode yields no
+// frames — the caller drops the zone (zoned map) or plays silence (single capture). Shared by
+// the zoned build and the single-capture path so both decode identically for the active mode.
+std::optional<DecodedZonePcm> decodeRelative(const std::string& projectDir,
+                                             const std::string& relativePath,
+                                             ChannelMode mode) {
+    const std::string abs = resolveBankFile(projectDir, relativePath);
+    if (abs.empty()) return std::nullopt;
+    const std::vector<std::uint8_t> bytes = readFileBytes(abs);
+    const WavLayout layout = parseWavLayout(bytes);
+    if (!layout.valid) return std::nullopt;
+    std::vector<AudioSample> interleaved =
+        extractFloatFrames(bytes, layout, 0, layout.frameCount());
+    DecodedZonePcm out = decodeChannels(interleaved, layout.channelCount, mode,
+                                        static_cast<int>(layout.sampleRate));
+    if (out.monoFrames.empty()) return std::nullopt;
+    return out;
+}
+
+}  // namespace
+
+FUnknown* ReaSamplerProcessor::createInstance(void* /*context*/) {
+    // The host owns the returned reference. Cast up to the combined interface the SDK
+    // exposes (IAudioProcessor) so the FUnknown refcount is correctly rooted.
+    return static_cast<IAudioProcessor*>(new ReaSamplerProcessor());
+}
+
+// Out-of-line so unique_ptr<ReaSamplerEmbed> sees the complete type here.
+ReaSamplerProcessor::~ReaSamplerProcessor() = default;
+
+tresult PLUGIN_API ReaSamplerProcessor::queryInterface(const TUID iid, void** obj) {
+    // S6: expose REAPER's inline-embed interface. REAPER queries the IEditController for
+    // IReaperUIEmbedInterface (reaper_vst3_interfaces.h); hand it our lazily-created embed
+    // shell. We own the shell (unique_ptr); the borrowed reference is valid because the
+    // processor outlives it. All other iids fall through to the SDK's queryInterface.
+    if (FUnknownPrivate::iidEqual(iid, IReaperUIEmbedInterface::iid)) {
+        if (!embed_) embed_ = std::make_unique<ReaSamplerEmbed>(this);
+        embed_->addRef();
+        *obj = static_cast<IReaperUIEmbedInterface*>(embed_.get());
+        return kResultOk;
+    }
+    return SingleComponentEffect::queryInterface(iid, obj);
+}
+
+tresult PLUGIN_API ReaSamplerProcessor::initialize(FUnknown* context) {
+    tresult result = SingleComponentEffect::initialize(context);
+    if (result != kResultOk) return result;
+
+    // Connect the REAPER bridge. Non-fatal if it fails (non-REAPER host): the
+    // instrument still loads, it just has no live bank to play.
+    bridge_.connect(context);
+
+    // Instrument bus topology: one event input (MIDI in, 16 channels), one audio output, no
+    // audio input. The output arrangement follows the instance's channel mode (S7) — mono by
+    // default (kMono), stereo (kStereo) when the mode is stereo. addAudioOutput needs an initial
+    // arrangement; seed it at the mode's arrangement so getBusInfo is correct from the first
+    // query. (setState may later flip the mode and re-negotiate via setChannelMode.)
+    addEventInput(STR16("MIDI In"), 16);
+    const ChannelMode mode = channelMode();
+    addAudioOutput(STR16("Audio Out"),
+                   mode == ChannelMode::Stereo ? SpeakerArr::kStereo : SpeakerArr::kMono);
+
+    return kResultOk;
+}
+
+tresult PLUGIN_API ReaSamplerProcessor::terminate() {
+    // process() is not running at terminate. Free the live instrument and drain the
+    // graveyard. Take the pointer out of the atomic first so nothing else races it.
+    std::lock_guard<std::mutex> lock(reloadMutex_);
+    delete live_.exchange(nullptr);
+    graveyard_.clear();
+    return SingleComponentEffect::terminate();
+}
+
+tresult PLUGIN_API ReaSamplerProcessor::setActive(TBool state) {
+    // Activating: build the instrument from the currently-selected sample so the first
+    // block after activation can play. Deactivating: process is now GUARANTEED stopped by
+    // the host, so this is the safe point to reclaim the graveyard (the displaced engines
+    // no reload could free while active). The build/drain are off the audio thread —
+    // setActive is a main/UI-thread call.
+    if (state) {
+        reloadFromBank();
+    } else {
+        std::lock_guard<std::mutex> lock(reloadMutex_);
+        graveyard_.clear();
+    }
+    return kResultOk;
+}
+
+tresult PLUGIN_API ReaSamplerProcessor::setupProcessing(ProcessSetup& setup) {
+    sampleRate_ = setup.sampleRate;
+    maxBlockSize_ = setup.maxSamplesPerBlock;
+    return SingleComponentEffect::setupProcessing(setup);
+}
+
+tresult PLUGIN_API ReaSamplerProcessor::setState(IBStream* state) {
+    if (!state) return kResultFalse;
+    // Read the whole component-state blob (the performance map, versioned). The blob is
+    // small; read in one shot into a growable buffer.
+    std::vector<std::uint8_t> bytes;
+    std::uint8_t chunk[256];
+    int32 got = 0;
+    while (state->read(chunk, sizeof(chunk), &got) == kResultOk && got > 0) {
+        bytes.insert(bytes.end(), chunk, chunk + got);
+    }
+    // Component state (v3, S10) is {single-capture selection id, opt-in zones}. The
+    // selection and the zones are DISTINCT — the default face is one picked capture, zones
+    // are a demoted overlay — so both are restored explicitly (no more inferring a selection
+    // from a lone zone). deserializeComponentState lifts older blobs cleanly: a v2 zones-only
+    // blob restores {"", zones}; a v1 S4 single-selection blob restores {id, one-zone map} so
+    // the old pick survives as both; an empty/unknown blob restores {"", no zones} — the S10
+    // silent empty state (no first-sample fallback in reloadFromBank).
+    // Pass sampleRate_ as the project rate for legacy v3 blob conversion (frames -> seconds at
+    // the v3 read boundary). sampleRate_ is set by setupProcessing; REAPER calls setupProcessing
+    // before setState on project load, so sampleRate_ is the real host rate here. A v3 blob on a
+    // pre-setup call would assert inside readZonesPayload (a programming error, not a field case).
+    const ComponentState cs = deserializeComponentState(bytes, sampleRate_);
+    setSelectedSampleId(cs.selectionId);
+    setPerformanceMap(cs.map);
+    // S8: restore the last-consumed assignment generation so a re-open does not re-apply a
+    // stale assign_request (the user may have manually changed the selection after the assign).
+    {
+        std::lock_guard<std::mutex> lock(assignMarkerMutex_);
+        lastConsumedAssignGeneration_ = cs.lastConsumedAssignGeneration;
+    }
+    // Restore the S7 channel mode and point the output bus at its arrangement so a reopened
+    // project comes back in the saved mode. setState runs before the host queries bus info, so
+    // seeding the arrangement here (rather than re-negotiating) is enough — no restartComponent.
+    {
+        std::lock_guard<std::mutex> lock(channelModeMutex_);
+        channelMode_ = cs.channelMode;
+    }
+    applyOutputArrangement(cs.channelMode);
+    // Rebuild from the restored state (off-thread — setState is a load-time call).
+    reloadFromBank();
+    return kResultOk;
+}
+
+tresult PLUGIN_API ReaSamplerProcessor::getState(IBStream* state) {
+    if (!state) return kResultFalse;
+    // Persist the full instance state (v3, S10): the single-capture selection id AND the
+    // opt-in zones — the instrument's own state (D-B), NEVER written to the "reasampler"
+    // bank ext-state. An instance with no pick and no zones serializes to {"", no zones}
+    // and restores as the S10 empty state (silence + "pick a capture"), never auto-playing
+    // sample #1.
+    ComponentState state_out;
+    state_out.selectionId = selectedSampleId();
+    state_out.map = performanceMap();
+    state_out.channelMode = channelMode();  // S7: persist the per-instance mono/stereo mode
+    {
+        std::lock_guard<std::mutex> lock(assignMarkerMutex_);
+        state_out.lastConsumedAssignGeneration = lastConsumedAssignGeneration_;  // S8 reader marker
+    }
+    const std::vector<std::uint8_t> bytes = serializeComponentState(state_out);
+    if (!bytes.empty()) {
+        const tresult wr = state->write(const_cast<std::uint8_t*>(bytes.data()),
+                                        static_cast<int32>(bytes.size()), nullptr);
+        if (wr != kResultOk) return wr;
+    }
+    return kResultOk;
+}
+
+std::string ReaSamplerProcessor::selectedSampleId() {
+    std::lock_guard<std::mutex> lock(selectionMutex_);
+    return selectedSampleId_;
+}
+
+void ReaSamplerProcessor::setSelectedSampleId(const std::string& id) {
+    std::lock_guard<std::mutex> lock(selectionMutex_);
+    selectedSampleId_ = id;
+}
+
+PerformanceMap ReaSamplerProcessor::performanceMap() {
+    std::lock_guard<std::mutex> lock(performanceMutex_);
+    return performanceMap_;
+}
+
+void ReaSamplerProcessor::setPerformanceMap(const PerformanceMap& map) {
+    std::lock_guard<std::mutex> lock(performanceMutex_);
+    performanceMap_ = map;
+}
+
+ChannelMode ReaSamplerProcessor::channelMode() {
+    std::lock_guard<std::mutex> lock(channelModeMutex_);
+    return channelMode_;
+}
+
+void ReaSamplerProcessor::applyOutputArrangement(ChannelMode mode) {
+    // Set the single output bus's SpeakerArrangement to the mode's arrangement so getBusInfo /
+    // getBusArrangement report the right channel count. The default getBusArrangement (from the
+    // base) reads back exactly what we store here. No re-negotiation — the caller drives that.
+    BusList* outs = getBusList(kAudio, kOutput);
+    if (!outs || outs->empty()) return;
+    if (auto* bus = FCast<AudioBus>(outs->at(0))) {
+        bus->setArrangement(mode == ChannelMode::Stereo ? SpeakerArr::kStereo
+                                                        : SpeakerArr::kMono);
+    }
+}
+
+void ReaSamplerProcessor::setChannelMode(ChannelMode mode) {
+    {
+        std::lock_guard<std::mutex> lock(channelModeMutex_);
+        if (channelMode_ == mode) return;  // no-op: don't churn the bus / re-negotiate
+        channelMode_ = mode;
+    }
+    // The mode changed: repoint the output bus and ask the host to re-negotiate I/O so REAPER's
+    // routing follows (mono<->stereo). restartComponent is a main/UI-thread call; setChannelMode
+    // is driven from the editor, so this is safe. Then reload so the next block decodes the new
+    // channel count into the LoadedInstrument (off-thread, RT path untouched).
+    applyOutputArrangement(mode);
+    if (componentHandler) componentHandler->restartComponent(kIoChanged);
+    reloadFromBank();
+}
+
+tresult PLUGIN_API ReaSamplerProcessor::setBusArrangements(
+    SpeakerArrangement* inputs, int32 numIns,
+    SpeakerArrangement* outputs, int32 numOuts) {
+    // The instrument has ONE canonical arrangement per its channel mode (S7). We take NO audio
+    // input, so any inputs are rejected. For the single output bus: accept (kResultTrue) only
+    // when the host proposes exactly the mode's arrangement; otherwise reject (kResultFalse) but
+    // KEEP the mode's arrangement (per the VST3 contract, a plug-in that can't honor a proposal
+    // keeps a valid arrangement of its own). getBusArrangement then still reports the mode's
+    // channel count, so the host adapts its routing to us rather than forcing our channel count.
+    if (numIns < 0 || numOuts < 0) return kInvalidArgument;
+    if (numIns > 0) return kResultFalse;  // no audio input bus to arrange
+
+    const SpeakerArrangement want =
+        channelMode() == ChannelMode::Stereo ? SpeakerArr::kStereo : SpeakerArr::kMono;
+    applyOutputArrangement(channelMode());  // keep the bus pinned to the mode's arrangement
+    if (numOuts == 1 && outputs && outputs[0] == want) return kResultTrue;
+    return kResultFalse;
+}
+
+std::string ReaSamplerProcessor::reloadFromBank() {
+    // OFF THE AUDIO THREAD. Serialize concurrent reloads (editor click + setState) so
+    // the retired-slot free is single-writer. This mutex is NEVER taken on the audio
+    // thread — process() only touches the atomic.
+    std::lock_guard<std::mutex> lock(reloadMutex_);
+
+    // Mint this reload's generation number first so we can stamp the built instrument
+    // with it before publishing. Under reloadMutex_ no other reload races here.
+    const std::uint64_t gen = reloadGeneration_.fetch_add(1, std::memory_order_relaxed) + 1;
+
+    // 1. Read the live bank + resolve the project dir over the bridge (allocates,
+    //    calls REAPER — fine here, off-thread).
+    std::optional<std::string> banksJson =
+        bridge_.readReasamplerExtState(kProjExtBanksKey);
+    const std::string projectDir = bridge_.activeProjectDir();
+    // The active channel mode (S7) governs how each WAV decodes (mono downmix vs 2-channel).
+    // Read once under its mutex, off the audio thread, before the decode loop.
+    const ChannelMode mode = channelMode();
+
+    std::string resolvedId;
+    std::unique_ptr<LoadedInstrument> built;
+
+    if (banksJson) {
+        // 2. Tier 1 first: if the instrument's performance map is non-empty, resolve its
+        //    zones against the live bank (STALE ids drop cleanly), decode each zone's WAV
+        //    off-thread, and build the ZONED keymap. Each surviving zone plays its bank
+        //    sample repitched from its effective root note (override > bank intrinsic > C4).
+        //    A zone whose WAV fails to decode is dropped (not the whole map).
+        const PerformanceMap map = performanceMap();
+        Keymap km;
+        bool haveKeymap = false;
+
+        if (!map.empty()) {
+            const ResolvedPerformance resolved = resolvePerformance(*banksJson, map);
+            if (!resolved.zones.empty()) {
+                std::vector<DecodedZonePcm> decoded;
+                std::vector<ResolvedZone> kept;
+                decoded.reserve(resolved.zones.size());
+                kept.reserve(resolved.zones.size());
+                for (const ResolvedZone& rz : resolved.zones) {
+                    std::optional<DecodedZonePcm> pcm =
+                        decodeRelative(projectDir, rz.relativePath, mode);
+                    if (!pcm) continue;  // unreadable WAV -> drop this zone
+                    kept.push_back(rz);
+                    decoded.push_back(std::move(*pcm));
+                }
+                km = buildZonedKeymap(kept, decoded);
+                haveKeymap = !km.zones.empty();
+            }
+        }
+
+        // 3. Single-capture fast path (S10): an empty performance map plays the ONE
+        //    deliberately-selected capture chromatically across the whole keyboard. This is
+        //    the default face — one picked capture, repitched from its root. NO first-
+        //    sample fallback: an EMPTY selection (or a stale id) resolves to nullopt in
+        //    selectSample, so an un-picked instrument stays SILENT (the editor shows its
+        //    "pick a capture" empty state) rather than auto-playing sample #1 (S10 policy
+        //    reversal of the S4 convenience default).
+        if (!haveKeymap) {
+            std::optional<SelectedSample> sel =
+                selectSample(*banksJson, selectedSampleId());
+            if (sel) {
+                std::optional<DecodedZonePcm> pcm =
+                    decodeRelative(projectDir, sel->relativePath, mode);
+                if (pcm) {
+                    km = buildTier0Keymap(std::move(pcm->monoFrames), pcm->sampleRate,
+                                          sel->rootNote, sel->loop,
+                                          std::move(pcm->framesR));
+                    haveKeymap = true;
+                    resolvedId = selectedSampleId();  // the concrete pick that resolved
+                }
+            }
+        }
+
+        if (haveKeymap) {
+            // Preserve OLA window in OUTPUT frames from the host sample rate (kPreserveWindowMs).
+            // Every voice's shifter is pre-sized to this off-thread here, so process()-time
+            // note-on never allocates. Floored at 2 so a valid window is always a real ring
+            // (which also covers a pathological host rate <= 0 — no rate literal needed).
+            std::int64_t preserveWindow = static_cast<std::int64_t>(
+                kPreserveWindowMs * sampleRate_ / 1000.0 + 0.5);
+            if (preserveWindow < 2) preserveWindow = 2;
+            built = std::make_unique<LoadedInstrument>(
+                std::move(km), kMaxVoices, gen, kPreserveVoiceCap,
+                preserveWindow);
+        }
+    }
+
+    // 4. Publish. Atomically install the new instrument; the DISPLACED one goes to the
+    //    graveyard tagged with this generation (process may still be mid-block reading
+    //    it). A null `built` (no bank / unreadable WAV) installs silence.
+    //    `built` is heap-owned; release() hands ownership to the atomic, and the
+    //    exchanged pointer is re-owned by the graveyard.
+    //
+    //    Bounded reclaim: prune graveyard entries where displacedAt <= seen, where seen
+    //    is the last generation process() published. process() publishes inst->installedAt
+    //    (not a re-read of reloadGeneration_), so seen == D means process holds the
+    //    instrument installed at gen D. An entry with displacedAt == D was displaced by
+    //    reload D, which installed that very successor — process cannot be holding the
+    //    displaced entry. The pruning condition is therefore <= (see header for the full
+    //    proof). Remaining entries drain at setActive(false) / terminate() when process
+    //    is guaranteed stopped.
+    const std::uint64_t seen = processGeneration_.load(std::memory_order_acquire);
+    graveyard_.erase(
+        std::remove_if(graveyard_.begin(), graveyard_.end(),
+                       [seen](const GraveyardEntry& e) { return e.displacedAt <= seen; }),
+        graveyard_.end());
+    LoadedInstrument* prev = live_.exchange(built.release());
+    if (prev) graveyard_.push_back({gen, std::unique_ptr<LoadedInstrument>(prev)});
+    return resolvedId;
+}
+
+ReaSamplerProcessor::BankSyncResult
+ReaSamplerProcessor::pollBankSync(bool isFocusedTarget) {
+    // OFF THE AUDIO THREAD (the editor's UI timer calls this). Both reads allocate and call
+    // REAPER via the bridge — never invoked from process(). A disconnected bridge (non-REAPER
+    // host, or before connect) yields nullopt for both reads, so this no-ops cleanly.
+    BankSyncResult result;
+
+    // --- S8: assignment-request consume FIRST -------------------------------------
+    // Decode the pending assignment request (nullopt when absent/malformed). Resolve its
+    // (bankId, sampleId) against the live bank blob: selectSample returns non-nullopt only when
+    // the sampleId names an existing sample (the reader requirement — an unresolvable pair is
+    // dropped). Then run the pure consume decision against this instance's persisted marker.
+    std::optional<AssignmentRequest> request;
+    if (auto raw = bridge_.readReasamplerExtState(kProjExtAssignKey)) {
+        request = decodeAssignmentRequest(*raw);
+    }
+
+    bool resolves = false;
+    if (request) {
+        // Resolve the assigned sample against the CURRENT bank blob (a fresh read, so a request
+        // whose sample was rolled back by an extension undo resolves to nullopt -> dropped).
+        if (auto banksJson = bridge_.readReasamplerExtState(kProjExtBanksKey)) {
+            resolves = selectSample(*banksJson, request->sampleId).has_value();
+        }
+    }
+
+    // Read lastConsumed and conditionally write it back under a single lock scope so there
+    // is no interleave window between the read and the write (a concurrent getState could
+    // otherwise observe a stale marker between the two separate lock acquisitions).
+    std::int64_t lastConsumed = 0;
+    const AssignConsumeDecision decision = [&] {
+        std::lock_guard<std::mutex> lock(assignMarkerMutex_);
+        lastConsumed = lastConsumedAssignGeneration_;
+        const AssignConsumeDecision d =
+            consumeDecision(request, lastConsumed, resolves, isFocusedTarget);
+        // Advance the persisted consumed marker whenever the decision consumed the request
+        // (applied OR dropped-as-seen). getState will persist it on the next project save so
+        // a re-open does not re-apply. A non-target instance leaves the marker (decision
+        // returns it unchanged) so it stays eligible if focus later lands here.
+        if (d.consumedGeneration != lastConsumed) {
+            lastConsumedAssignGeneration_ = d.consumedGeneration;
+        }
+        return d;
+    }();
+
+    if (decision.apply) {
+        // Apply the assignment as this instance's own selection (the same path a user card-pick
+        // takes) — the instrument updates its OWN state, never the bank. reloadFromBank below
+        // rebuilds against the new selection, so skip a redundant reload here.
+        setSelectedSampleId(decision.sampleId);
+        result.applied = true;
+    }
+
+    // --- S9: bank-generation change-detection -------------------------------------
+    // Read the generation stamp; parse (absent/malformed -> 0, the pre-S9 default). FIRST poll
+    // (lastSeenBankGeneration_ == -1 sentinel): BASELINE the seen value without a reload — setState
+    // already loaded the current bank, so a redundant reload on open would only churn. A later
+    // generation CHANGE (a recapture/ingest/remove, or an undo that lowers it) then drives the
+    // reload. An assignment we just applied also needs a reload; fold both into ONE (coalesced).
+    std::int64_t currentGen = kBankGenerationAbsent;
+    if (auto rawGen = bridge_.readReasamplerExtState(kProjExtBankGenKey)) {
+        currentGen = parseBankGeneration(*rawGen);
+    }
+    const bool firstPoll = (lastSeenBankGeneration_ < 0);
+    const bool genChanged =
+        !firstPoll && bankGenerationChanged(lastSeenBankGeneration_, currentGen);
+    lastSeenBankGeneration_ = currentGen;
+
+    if (genChanged || result.applied) {
+        reloadFromBank();  // atomic pointer-swap handoff — glitch-free mid-play (S4 graveyard)
+        result.reloaded = genChanged;  // report S9 vs S8 distinctly for the editor's reaction
+    }
+    return result;
+}
+
+tresult PLUGIN_API ReaSamplerProcessor::process(ProcessData& data) {
+    // REAL-TIME: no allocation, no IO, no locks. Load the live instrument once for the
+    // whole block (a single atomic acquire), then publish inst->installedAt so the off-
+    // thread graveyard pruner knows exactly which generation this block is holding.
+    //
+    // We publish installedAt — not a fresh re-read of reloadGeneration_ — to close an
+    // ordering race: reading reloadGeneration_ after live_ could observe a generation
+    // newer than the pointer we actually hold, causing the pruner to free an instrument
+    // process is still reading. installedAt was set on the reload path before the atomic
+    // exchange that made the instrument visible, so it is always <= the generation of any
+    // instrument that could have been loaded after our acquire above.
+    LoadedInstrument* inst = live_.load(std::memory_order_acquire);
+    const std::uint64_t heldGen = inst ? inst->installedAt : 0;
+    processGeneration_.store(heldGen, std::memory_order_release);
+
+    // Marshal MIDI note-on/off from the event input into the voice engine. Tier 0 maps
+    // events at block granularity (no per-event sample-offset split) — audible timing is
+    // within one block, adequate for Tier 0; sample-accurate scheduling is a later tier.
+    if (inst && data.inputEvents) {
+        const int32 count = data.inputEvents->getEventCount();
+        for (int32 i = 0; i < count; ++i) {
+            Event e;
+            if (data.inputEvents->getEvent(i, e) != kResultOk) continue;
+            if (e.type == Event::kNoteOnEvent) {
+                // A note-on with velocity 0 is a note-off by MIDI convention.
+                const int vel = static_cast<int>(e.noteOn.velocity * 127.0f + 0.5f);
+                if (vel <= 0) {
+                    inst->engine.noteOff(e.noteOn.pitch);
+                } else {
+                    inst->engine.noteOn(e.noteOn.pitch, vel);
+                }
+            } else if (e.type == Event::kNoteOffEvent) {
+                inst->engine.noteOff(e.noteOff.pitch);
+            }
+        }
+    }
+
+    if (data.numOutputs <= 0 || !data.outputs || data.numSamples <= 0) {
+        embedPeak_.store(0.f, std::memory_order_relaxed);
+        return kResultOk;
+    }
+    AudioBusBuffers& out = data.outputs[0];
+    const int32 frames = data.numSamples;
+
+    // 64-bit host processing is not supported by the mono float core; emit silence
+    // rather than mis-render. REAPER runs 32-bit float by default.
+    if (data.symbolicSampleSize != kSample32) {
+        embedPeak_.store(0.f, std::memory_order_relaxed);
+        for (int32 ch = 0; ch < out.numChannels; ++ch) {
+            if (double* buf = out.channelBuffers64[ch]) {
+                for (int32 i = 0; i < frames; ++i) buf[i] = 0.0;
+            }
+        }
+        out.silenceFlags = (out.numChannels >= 64)
+                               ? ~0ULL
+                               : ((1ULL << out.numChannels) - 1);
+        return kResultOk;
+    }
+
+    // Render per the host's NEGOTIATED output channel count (S7). The channel mode was baked
+    // into the LoadedInstrument's decode + negotiated onto the output bus off-thread, so here
+    // we simply match the buffers the host handed us: >=2 channels -> true stereo render into
+    // ch0/ch1 (then replicate any extra channels); exactly 1 -> the mono render. Either way the
+    // render ADDS into a cleared buffer — RT-safe (no alloc/IO/lock). NEVER reads the mode here.
+    float* ch0 = out.numChannels > 0 ? out.channelBuffers32[0] : nullptr;
+    float* ch1 = out.numChannels > 1 ? out.channelBuffers32[1] : nullptr;
+    if (ch0 && ch1) {
+        // Stereo: clear both, render L/R. A mono sample plays dual-mono via the engine's stereo
+        // path (both channels equal), so a mono capture in stereo mode is centered, not silent.
+        for (int32 i = 0; i < frames; ++i) { ch0[i] = 0.f; ch1[i] = 0.f; }
+        if (inst) {
+            inst->engine.render(ch0, ch1, static_cast<std::size_t>(frames));
+        }
+        // Any channels beyond the first two mirror ch0 (defensive — REAPER negotiates 1 or 2).
+        for (int32 ch = 2; ch < out.numChannels; ++ch) {
+            if (float* buf = out.channelBuffers32[ch]) {
+                for (int32 i = 0; i < frames; ++i) buf[i] = ch0[i];
+            }
+        }
+        // Block peak (max across L/R) for the embed strip's level indicator; RT-safe.
+        float peak = 0.f;
+        for (int32 i = 0; i < frames; ++i) {
+            const float a0 = ch0[i] < 0.f ? -ch0[i] : ch0[i];
+            const float a1 = ch1[i] < 0.f ? -ch1[i] : ch1[i];
+            if (a0 > peak) peak = a0;
+            if (a1 > peak) peak = a1;
+        }
+        embedPeak_.store(peak, std::memory_order_relaxed);
+    } else if (ch0) {
+        // Mono: render into channel 0, replicate to any extra channels (mono bus is 1 channel;
+        // the replicate is defensive for a host that still hands >1 channel on a mono bus).
+        for (int32 i = 0; i < frames; ++i) ch0[i] = 0.f;
+        if (inst) {
+            inst->engine.render(ch0, static_cast<std::size_t>(frames));
+        }
+        float peak = 0.f;
+        for (int32 i = 0; i < frames; ++i) {
+            const float a = ch0[i] < 0.f ? -ch0[i] : ch0[i];
+            if (a > peak) peak = a;
+        }
+        embedPeak_.store(peak, std::memory_order_relaxed);
+        for (int32 ch = 1; ch < out.numChannels; ++ch) {
+            if (float* buf = out.channelBuffers32[ch]) {
+                for (int32 i = 0; i < frames; ++i) buf[i] = ch0[i];
+            }
+        }
+    }
+
+    // Report silence only when nothing is loaded (lets the host optimize when idle).
+    // With an instrument loaded we clear the flag so a ringing voice is not skipped.
+    out.silenceFlags = inst ? 0 : ((out.numChannels >= 64)
+                                       ? ~0ULL
+                                       : ((1ULL << out.numChannels) - 1));
+    return kResultOk;
+}
+
+IPlugView* PLUGIN_API ReaSamplerProcessor::createView(FIDString name) {
+    if (name && FIDStringsEqual(name, ViewType::kEditor)) {
+        return new ReaSamplerEditor(this);
+    }
+    return nullptr;
+}
+
+}  // namespace reasampler::vst

src/vst/reasampler_processor.h

@@ -0,0 +1,272 @@
+// reasampler_processor.h — the VST3 SingleComponentEffect (Phase S4, Tier 0). Wires the
+// pure S3 sampler core into a real VSTi: it declares an event-input bus + a stereo audio
+// output bus, marshals host MIDI note-on/off into the VoiceEngine, and renders the
+// engine's audio into the output bus — so a chosen bank sample plays chromatically from
+// its root note in REAPER's routing/record/render path.
+//
+// SingleComponentEffect is the SDK's combined processor+controller base — sanctioned
+// for a non-distributable, REAPER-only plugin under D5/D6. It gives us
+// addAudioOutput/addEventInput, IComponent setState/getState for the instance's own
+// state (the selected sample), and the IEditController seat so createView() can hand the
+// host our IPlugView LICE editor.
+//
+// REAL-TIME DISCIPLINE (S4 hard constraint). The audio thread (process) does NO
+// allocation, NO file I/O, NO bridge calls, NO locks. Sample loading — bridge ext-state
+// read, WAV decode, path resolve, keymap build, VoiceEngine construction — all happens
+// OFF the audio thread (reloadFromBank, driven from the main/UI thread) and is handed to
+// process via a single atomic pointer swap. See the LoadedInstrument handoff below.
+
+#pragma once
+
+#include <atomic>
+#include <cstdint>
+#include <memory>
+#include <mutex>
+#include <string>
+#include <vector>
+
+#include "public.sdk/source/vst/vstsinglecomponenteffect.h"
+
+#include "reaper_bridge.h"
+#include "sample_map.h"     // PerformanceMap (the instrument's owned zoned keymap)
+#include "sampler_core.h"
+
+namespace reasampler::vst {
+
+class ReaSamplerEmbed;  // S6 embedded TCP/MCP UI shell (owned below; see queryInterface)
+
+// One fully-built, ready-to-play instrument snapshot: the decoded keymap and the voice
+// engine that plays it. The engine holds a reference into the keymap, so the two MUST
+// live and die together at a STABLE address — hence this is heap-allocated and neither
+// copyable nor movable. The audio thread only ever reads it through an atomic pointer;
+// it is built and destroyed off the audio thread.
+//
+// installedAt: the reloadGeneration_ value at which this instrument was atomically
+// installed into live_. Set on the reload path before the exchange. process() publishes
+// this field (not a fresh re-read of reloadGeneration_) so the published generation is
+// exactly the generation of the instrument actually in hand for the block.
+struct LoadedInstrument {
+    Keymap keymap;
+    VoiceEngine engine;
+    std::uint64_t installedAt = 0;  // reload generation at which this was installed
+
+    LoadedInstrument(Keymap km, std::size_t maxVoices,
+                     std::uint64_t gen, std::size_t preserveVoiceCap = 0,
+                     std::int64_t preserveWindowFrames = 0)
+        : keymap(std::move(km)),
+          engine(maxVoices, keymap, preserveVoiceCap, preserveWindowFrames),
+          installedAt(gen) {}
+
+    LoadedInstrument(const LoadedInstrument&) = delete;
+    LoadedInstrument& operator=(const LoadedInstrument&) = delete;
+};
+
+class ReaSamplerProcessor : public Steinberg::Vst::SingleComponentEffect {
+public:
+    ReaSamplerProcessor() = default;
+    // Out-of-line so the owned ReaSamplerEmbed (held by unique_ptr, forward-declared here)
+    // is a complete type at the destruction point (defined in the .cpp).
+    ~ReaSamplerProcessor() override;
+
+    // The factory create function (registered in vst_entry.cpp).
+    static Steinberg::FUnknown* createInstance(void* /*context*/);
+
+    //--- from IComponent / IPluginBase -------------------------------------
+    // Connects the REAPER bridge (context is REAPER's IHostApplication) and declares
+    // the instrument bus topology.
+    Steinberg::tresult PLUGIN_API initialize(Steinberg::FUnknown* context) override;
+    Steinberg::tresult PLUGIN_API terminate() override;
+    Steinberg::tresult PLUGIN_API setActive(Steinberg::TBool state) override;
+
+    // Instance state = the selected bank sample id (D-B: a performance choice the
+    // instrument owns; NEVER written back to the bank). Component-state, so a saved
+    // REAPER project restores which sample each instance plays.
+    Steinberg::tresult PLUGIN_API setState(Steinberg::IBStream* state) override;
+    Steinberg::tresult PLUGIN_API getState(Steinberg::IBStream* state) override;
+
+    //--- from IAudioProcessor ----------------------------------------------
+    Steinberg::tresult PLUGIN_API setupProcessing(
+        Steinberg::Vst::ProcessSetup& setup) override;
+    // Marshals MIDI -> VoiceEngine -> audio output. Real-time safe (no alloc/IO/lock).
+    Steinberg::tresult PLUGIN_API process(
+        Steinberg::Vst::ProcessData& data) override;
+
+    // S7 channel-mode bus negotiation. The instrument has ONE canonical output arrangement
+    // determined by its per-instance channel mode (mono -> kMono, stereo -> kStereo). We
+    // accept the host's proposal only when it matches that arrangement; otherwise we reject
+    // (kResultFalse) but keep the mode's arrangement, so getBusArrangement / getBusInfo always
+    // report the mode's channel count and REAPER routes accordingly. A runtime mode change
+    // updates the output bus + calls restartComponent(kIoChanged) to trigger re-negotiation.
+    Steinberg::tresult PLUGIN_API setBusArrangements(
+        Steinberg::Vst::SpeakerArrangement* inputs, Steinberg::int32 numIns,
+        Steinberg::Vst::SpeakerArrangement* outputs, Steinberg::int32 numOuts) override;
+
+    //--- from IEditController -----------------------------------------------
+    // Hands the host our LICE IPlugView editor.
+    Steinberg::IPlugView* PLUGIN_API createView(Steinberg::FIDString name) override;
+
+    // Override queryInterface to additionally expose REAPER's IReaperUIEmbedInterface (S6):
+    // REAPER queries the IEditController for it to drive the inline TCP/MCP embed surface.
+    // All other iids delegate to SingleComponentEffect's implementation unchanged.
+    Steinberg::tresult PLUGIN_API queryInterface(const Steinberg::TUID iid,
+                                                 void** obj) override;
+
+    // The embedded-strip activity level (0..1), read by the S6 embed shell on the UI thread.
+    // Backed by embedPeak_, the per-block mono peak the audio thread stores relaxed — a
+    // lock-free advisory readout, never touched with a lock the audio thread could contend.
+    double embedActivityLevel() const {
+        return static_cast<double>(embedPeak_.load(std::memory_order_relaxed));
+    }
+
+    // Called by the editor (main/UI thread) when the user picks a sample, and internally
+    // on load. Reads the live bank over the bridge, resolves+decodes the selected WAV
+    // OFF the audio thread, and publishes the built instrument to process() via an
+    // atomic swap. Safe to call with no bridge / no bank (leaves silence). Returns the
+    // resolved selection id ("" if nothing was loaded) for the editor to reflect.
+    std::string reloadFromBank();
+
+    // The result of a bank-sync poll (S9/S8): what pollBankSync did this tick, so the editor
+    // can react (repaint / re-snapshot its own view) only when something actually changed.
+    struct BankSyncResult {
+        bool reloaded = false;    // the bank generation changed -> reloadFromBank ran
+        bool applied = false;     // a new assignment request was applied -> selection changed
+    };
+
+    // Poll the S9 bank-generation counter and the S8 assignment request over the bridge, OFF
+    // THE AUDIO THREAD (the editor's UI timer drives this — NEVER process()). Semantics:
+    //   * S9: if the bank generation differs from what we last saw, call reloadFromBank() so a
+    //     recapture/ingest refreshes playback hands-free (atomic swap, glitch-free).
+    //   * S8: if a NEW (generation > last consumed) assignment request names a resolvable
+    //     sample AND this instance is the target (isFocusedTarget), apply it as the selection
+    //     and reload; an unresolvable request is DROPPED silently (marker advanced, no change);
+    //     a non-target instance neither applies nor advances its marker.
+    // The consumed marker advances in component state (marked dirty via the host handler) so a
+    // re-open does not re-apply. `isFocusedTarget` is the shell's thundering-herd policy input
+    // (the editor passes true only for the instance whose editor is open — see the handoff).
+    // Idempotent on an idle tick (generation unchanged + no new request -> no work).
+    BankSyncResult pollBankSync(bool isFocusedTarget);
+
+    // The bridge, for the editor's live-state readout + sample list. Owned here; the
+    // editor borrows it (outlives the editor).
+    ReaperBridge& bridge() { return bridge_; }
+    // The current single-capture selection id (main/UI thread reads for the editor). Guarded
+    // by selectionMutex_ — never touched on the audio thread. Since S10 this is the ONE picked
+    // capture the default face plays chromatically when the performance map is empty; an EMPTY
+    // id resolves to SILENCE (no first-sample fallback). A non-empty zoned map supersedes it.
+    std::string selectedSampleId();
+    void setSelectedSampleId(const std::string& id);
+
+    // The performance map (Tier 1: the zoned keymap the instrument owns; D-B). Read/written
+    // by the editor on the UI thread; snapshotted under performanceMutex_. NEVER read on the
+    // audio thread — reloadFromBank bakes it into the LoadedInstrument's Keymap off-thread.
+    PerformanceMap performanceMap();
+    void setPerformanceMap(const PerformanceMap& map);
+
+    // The per-instance channel mode (S7, D-E: mono | stereo). Read/written on the UI thread
+    // (the editor toggle) and read off-thread by getState/reloadFromBank; guarded by
+    // channelModeMutex_. NEVER read on the audio thread — process() renders against the host's
+    // negotiated output channel count, and reloadFromBank bakes the mode into the decode.
+    ChannelMode channelMode();
+    // Sets the mode. When it CHANGES, updates the output bus arrangement (mono->kMono /
+    // stereo->kStereo) and asks the host to re-negotiate I/O via restartComponent(kIoChanged),
+    // then reloads the instrument so the next block decodes the new channel count. A no-op set
+    // (same mode) does neither. UI thread only.
+    void setChannelMode(ChannelMode mode);
+
+private:
+    // Apply `mode` to the output audio bus's SpeakerArrangement (kMono / kStereo). Called from
+    // initialize (topology) and setChannelMode (runtime change). Does NOT re-negotiate — the
+    // caller drives restartComponent when appropriate.
+    void applyOutputArrangement(ChannelMode mode);
+
+    ReaperBridge bridge_;
+
+    // --- The audio-thread handoff (S4 real-time discipline) -----------------
+    // process() atomically loads `live_` at block start and marshals/renders against it —
+    // a single atomic acquire, no lock, no free on the audio thread.
+    //
+    // reloadFromBank() (off-thread, serialized by reloadMutex_) builds a new
+    // LoadedInstrument and atomically swaps it into `live_`. The DISPLACED instrument is
+    // NOT freed on the reload path: process() may still be mid-block reading it, and two
+    // rapid reloads could otherwise free a pointer process is using. Instead it is parked
+    // in `graveyard_` tagged with the reload generation at which it was displaced.
+    //
+    // Bounded reclaim: process() publishes inst->installedAt (the generation at which the
+    // held instrument was installed) via processGeneration_ — a single atomic store, RT-
+    // safe. The reload path prunes graveyard entries where displacedAt <= seen (where seen
+    // is the last published processGeneration_).
+    //
+    // Safety argument: an entry with displacedAt == D was displaced by reload D, which
+    // simultaneously installed its successor with installedAt == D. process() publishing
+    // seen == D means it holds that successor (or a later one). In either case, the
+    // displaced entry is not the pointer process is using, so freeing it is safe. The
+    // pruning condition is therefore <= (not strict <): an entry displaced at exactly the
+    // published generation is also provably unreachable.
+    //
+    // The graveyard's upper bound is the number of reloads since process last ran
+    // (typically 0–1 in normal use). Remaining entries drain at setActive(false) /
+    // terminate(), when the host guarantees process is stopped.
+    std::atomic<LoadedInstrument*> live_{nullptr};
+    std::atomic<std::uint64_t> reloadGeneration_{0};   // incremented by each reload (off-thread, under reloadMutex_; read atomically by process)
+    std::atomic<std::uint64_t> processGeneration_{0};  // generation last seen by process (written on audio thread, read off-thread)
+    struct GraveyardEntry {
+        std::uint64_t displacedAt = 0;                 // reloadGeneration_ value when this was displaced
+        std::unique_ptr<LoadedInstrument> instrument;
+    };
+    std::vector<GraveyardEntry> graveyard_;  // drained on reclaim + setActive(false) + terminate
+    std::mutex reloadMutex_;  // serializes off-thread reloads + graveyard access
+
+    // The single-capture selection id (S10: the ONE picked capture; "" = no pick -> silence).
+    // Off-thread only; a small mutex guards the string against a getState/editor race. NOT
+    // read on the audio thread.
+    std::mutex selectionMutex_;
+    std::string selectedSampleId_;
+
+    // The performance map (Tier 1: the instrument's owned zoned keymap). Off-thread only;
+    // guarded against a getState/editor race. NOT read on the audio thread — reloadFromBank
+    // bakes it into the LoadedInstrument's Keymap under the reload lock.
+    std::mutex performanceMutex_;
+    PerformanceMap performanceMap_;
+
+    // The per-instance channel mode (S7). Off-thread only (UI + getState + reloadFromBank);
+    // guarded against a getState/editor race. Default Mono preserves pre-S7 behavior. NOT read
+    // on the audio thread — process renders against the host's negotiated output channel count.
+    std::mutex channelModeMutex_;
+    ChannelMode channelMode_ = ChannelMode::Mono;
+
+    // The last assignment-request generation this instance CONSUMED (S8 reader). Persisted in
+    // component state (v5) so a re-open does not re-apply a request the user already got and
+    // then changed away from. Written by pollBankSync (UI/timer thread) and getState; read by
+    // pollBankSync + getState; seeded by setState. Guarded against a getState/poll race. NEVER
+    // read on the audio thread. Default 0 -> a genuinely new first assign (gen >= 1) applies.
+    std::mutex assignMarkerMutex_;
+    std::int64_t lastConsumedAssignGeneration_ = 0;
+
+    // The bank generation this instance last SAW (S9 reader). UI/timer-thread only (pollBankSync
+    // is the sole reader/writer) — no mutex needed, and it is NOT persisted. Initialized to a
+    // -1 SENTINEL (no real generation can be negative — parseBankGeneration yields >= 0) so the
+    // FIRST poll after an editor open BASELINES the seen value without a redundant reload (setState
+    // already loaded the current bank); a subsequent generation CHANGE then drives the reload.
+    // NOT read on the audio thread.
+    std::int64_t lastSeenBankGeneration_ = -1;
+
+    // Latched from setupProcessing so setActive/reload can size against it. Read
+    // off-thread only. 0.0 is explicitly invalid — setupProcessing sets the real host rate
+    // before any audio, and reloadFromBank guards on it before use.
+    double sampleRate_ = 0.0;
+    Steinberg::int32 maxBlockSize_ = 4096;
+
+    // --- S6 embedded TCP/MCP UI ---------------------------------------------
+    // The embed shell (IReaperUIEmbedInterface), created lazily on the first queryInterface
+    // and owned here for the processor's lifetime. REAPER borrows AddRef'd references from
+    // queryInterface; the shell's refcount is a no-op because THIS unique_ptr governs its
+    // destruction (the processor always outlives the borrowed references).
+    std::unique_ptr<ReaSamplerEmbed> embed_;
+
+    // The per-block mono peak (0..1+) the audio thread stores relaxed; the embed strip's
+    // level indicator reads it via embedActivityLevel(). Advisory only — a plain atomic,
+    // no ordering coupling, never guarded by a lock the audio thread touches.
+    std::atomic<float> embedPeak_{0.f};
+};
+
+}  // namespace reasampler::vst

src/vst/reasampler_vst.h

@@ -0,0 +1,79 @@
+// reasampler_vst.h — shared identity constants for the ReaSampler VST3 instrument
+// (Phase S). One place for the plugin's class UID, name, vendor, and version so the
+// processor, factory, and editor agree.
+//
+// A class UID is FOREVER-STABLE once shipped: a REAPER project that instantiates this
+// instrument records the UID, so changing it orphans every saved instance. Minted once;
+// do not regenerate.
+//
+// CHANNEL ISOLATION (S18, beta-in-isolation — the instrument-side companion to V4). Just
+// as V4 gave the extension a per-channel ext-state namespace / command-id family / dock
+// ident, S18 gives the VST3 instrument a per-channel PLUGIN IDENTITY: its class UID, its
+// on-disk filename, and its display name all fork by the ONE channel bit
+// (REASAMPLER_CHANNEL_IS_BETA, from version_generated.h). ONE class per binary — the bit
+// selects which UID compiles into the single DEF_CLASS2, so a beta build carries only the
+// beta identity and can never present the stable one (mirrors V4's fully-isolated-binary
+// philosophy). The two UIDs below are BOTH frozen forever; the filename + display name
+// derive from app_version's vstOutputName()/vstPluginName() (this header owns only the
+// binary UID identity — the string identity lives in the pure module).
+
+#pragma once
+
+#include "pluginterfaces/base/funknown.h"
+
+#include "version_generated.h"  // REASAMPLER_CHANNEL_IS_BETA — the one channel bit
+
+namespace reasampler::vst {
+
+// Vendor identity (S-NAME-1, SETTLED 2026-07-26). Shared across channels — V4 kept the
+// lane-name prefix shared, so shared-where-V4-shares is the default (the channel is carried
+// by the UID + filename + display fork, not the vendor block).
+inline constexpr const char* kVendorName = "ReaSampler";
+inline constexpr const char* kVendorUrl = "https://github.com/daniel-c-harvey/reasampler";
+inline constexpr const char* kVendorEmail = "mailto:the.real.daniel.harvey@gmail.com";
+
+// -----------------------------------------------------------------------------------------
+// The two FOREVER-FROZEN VST3 class UIDs — one per channel. A saved REAPER project records
+// the UID of the instance it instantiated and rebinds by it on reopen, so EACH is a
+// permanent commitment: changing either orphans every saved instance of that channel. The
+// channel bit selects which one this binary's factory registers (below) — one class per
+// binary, never both. Documented with the SAME gravity: neither may EVER be regenerated.
+
+// STABLE class UID (S-NAME-1). Minted at the S1 spike (2026-07-26), locked. FROZEN FOREVER.
+#define REASAMPLER_PROC_UID_1 0x5E45A11E
+#define REASAMPLER_PROC_UID_2 0x9C7B4D6A
+#define REASAMPLER_PROC_UID_3 0xB1E3F208
+#define REASAMPLER_PROC_UID_4 0x4A6C1D9F
+
+// BETA class UID (S18). Minted once (2026-07-26), locked FROM THIS WAVE per Daniel's
+// fast-track (fork S18-F1: mint now, not at first beta release). FROZEN FOREVER — the same
+// permanent lock as the stable UID; do not regenerate even though no beta VST has shipped.
+#define REASAMPLER_PROC_UID_BETA_1 0xCCFFEB3A
+#define REASAMPLER_PROC_UID_BETA_2 0x4FF532A6
+#define REASAMPLER_PROC_UID_BETA_3 0x9E181798
+#define REASAMPLER_PROC_UID_BETA_4 0x4256955F
+
+// The channel-selected UID macros the factory's INLINE_UID (compile-time brace init) and the
+// runtime FUID below both source, so exactly one class UID is compiled into this binary. This
+// is the ONLY channel #ifdef in the VST shell (an INLINE_UID needs literal brace-init tokens,
+// so it cannot route through app_version's runtime string accessors — the header owns the
+// binary UID fork, app_version owns the string fork).
+#if REASAMPLER_CHANNEL_IS_BETA
+#define REASAMPLER_ACTIVE_UID_1 REASAMPLER_PROC_UID_BETA_1
+#define REASAMPLER_ACTIVE_UID_2 REASAMPLER_PROC_UID_BETA_2
+#define REASAMPLER_ACTIVE_UID_3 REASAMPLER_PROC_UID_BETA_3
+#define REASAMPLER_ACTIVE_UID_4 REASAMPLER_PROC_UID_BETA_4
+#else
+#define REASAMPLER_ACTIVE_UID_1 REASAMPLER_PROC_UID_1
+#define REASAMPLER_ACTIVE_UID_2 REASAMPLER_PROC_UID_2
+#define REASAMPLER_ACTIVE_UID_3 REASAMPLER_PROC_UID_3
+#define REASAMPLER_ACTIVE_UID_4 REASAMPLER_PROC_UID_4
+#endif
+
+// The runtime FUID for the class this binary registers — the channel-selected UID above.
+static const Steinberg::FUID kReaSamplerProcessorUID(REASAMPLER_ACTIVE_UID_1,
+                                                     REASAMPLER_ACTIVE_UID_2,
+                                                     REASAMPLER_ACTIVE_UID_3,
+                                                     REASAMPLER_ACTIVE_UID_4);
+
+}  // namespace reasampler::vst

src/vst/sample_map.cpp

@@ -0,0 +1,640 @@
+// sample_map — pure implementation. See sample_map.h. NO VST3 / REAPER / SWELL /
+// vendor includes; standard library + the pure bank_book / wav_trim / sampler_core.
+
+#include "sample_map.h"
+
+#include <algorithm>  // std::min
+#include <cassert>    // assert
+#include <cstring>    // std::memcpy
+#include <utility>    // std::move
+
+namespace reasampler {
+
+namespace {
+
+// Translate a bank_model Sample's S2 intrinsics into the core's SampleLoop. The bank
+// stores loop points as an optional LoopPoints (both-or-neither); the core wants a
+// SampleLoop with an explicit hasLoop. Absent -> no loop.
+SampleLoop loopFromSample(const Sample& s) {
+    SampleLoop out;
+    if (s.loop) {
+        out.hasLoop = true;
+        out.start = s.loop->start;
+        out.end = s.loop->end;
+    }
+    return out;
+}
+
+// A distilled SelectedSample from a bank_model Sample. rootNote defaults to middle C
+// (60) when the bank left the intrinsic empty — Tier 0 still plays, just centered on
+// C rather than a captured pitch (surfaced: an un-rooted sample plays unity at C4).
+SelectedSample distill(const Sample& s) {
+    SelectedSample out;
+    out.relativePath = s.relativePath;
+    out.rootNote = s.rootNote ? *s.rootNote : 60;
+    out.loop = loopFromSample(s);
+    return out;
+}
+
+}  // namespace
+
+std::optional<SelectedSample> selectSample(const std::string& banksJson,
+                                           const std::string& sampleId) {
+    // POLICY REVERSAL (S10): an empty selection is SILENCE, not the first sample. Short-
+    // circuit before parsing — no stored id resolves to nothing to play by design.
+    if (sampleId.empty()) return std::nullopt;
+    if (banksJson.empty()) return std::nullopt;
+    std::optional<BankBook> book = BankBook::deserialize(banksJson);
+    if (!book) return std::nullopt;  // malformed -> nothing to play (never throw)
+
+    // Search every bank (pool first, then named — banks() is ordinal order) for the
+    // stored id. A sample lives in exactly one bank, so first hit wins.
+    for (const Bank& b : book->banks()) {
+        if (const Sample* s = b.index.query(sampleId)) {
+            return distill(*s);
+        }
+    }
+    // A stale stored id (no longer resolves) is SILENCE, not a substituted first sample:
+    // the editor reflects the missing pick with its empty state rather than masking it.
+    return std::nullopt;
+}
+
+std::vector<SampleChoice> listSamples(const std::string& banksJson) {
+    std::vector<SampleChoice> out;
+    if (banksJson.empty()) return out;
+    std::optional<BankBook> book = BankBook::deserialize(banksJson);
+    if (!book) return out;
+    for (const Bank& b : book->banks()) {
+        for (const Sample& s : b.index.all()) {
+            out.push_back(SampleChoice{s.id, s.displayName, s.rootNote, s.key, b.id});
+        }
+    }
+    return out;
+}
+
+std::vector<BankChoice> listBanks(const std::string& banksJson) {
+    std::vector<BankChoice> out;
+    if (banksJson.empty()) return out;
+    std::optional<BankBook> book = BankBook::deserialize(banksJson);
+    if (!book) return out;
+    for (const Bank& b : book->banks()) {
+        out.push_back(BankChoice{b.id, b.displayName});
+    }
+    return out;
+}
+
+std::vector<AudioSample> downmixToMono(const std::vector<AudioSample>& interleaved,
+                                       int channelCount) {
+    std::vector<AudioSample> out;
+    if (channelCount <= 0 || interleaved.empty()) return out;
+    const std::size_t stride = static_cast<std::size_t>(channelCount);
+    const std::size_t frames = interleaved.size() / stride;
+    out.resize(frames);
+    const double inv = 1.0 / static_cast<double>(channelCount);
+    for (std::size_t f = 0; f < frames; ++f) {
+        double acc = 0.0;
+        const std::size_t base = f * stride;
+        for (std::size_t c = 0; c < stride; ++c) {
+            acc += static_cast<double>(interleaved[base + c]);
+        }
+        out[f] = static_cast<AudioSample>(acc * inv);
+    }
+    return out;
+}
+
+std::vector<AudioSample> extractChannel(const std::vector<AudioSample>& interleaved,
+                                        int channelCount, int which) {
+    std::vector<AudioSample> out;
+    if (channelCount <= 0 || interleaved.empty()) return out;
+    const std::size_t stride = static_cast<std::size_t>(channelCount);
+    // Clamp the requested channel into the source's range: a channel past the last one reads
+    // the last channel (a mono source asked for channel 1 yields channel 0 — dual-mono).
+    std::size_t ch = which < 0 ? 0 : static_cast<std::size_t>(which);
+    if (ch >= stride) ch = stride - 1;
+    const std::size_t frames = interleaved.size() / stride;
+    out.resize(frames);
+    for (std::size_t f = 0; f < frames; ++f) out[f] = interleaved[f * stride + ch];
+    return out;
+}
+
+DecodedZonePcm decodeChannels(const std::vector<AudioSample>& interleaved,
+                              int sourceChannels, ChannelMode mode, int sampleRate) {
+    assert(sampleRate > 0 && "decodeChannels: sampleRate must be > 0 (programming error)");
+    DecodedZonePcm out;
+    if (sampleRate <= 0) return out;  // safe early-return; caller supplied an invalid rate
+    out.sampleRate = sampleRate;
+    if (mode == ChannelMode::Mono) {
+        // MONO mode: the existing downmix policy (average all source channels), one channel out.
+        out.monoFrames = downmixToMono(interleaved, sourceChannels);
+        return out;  // framesR stays empty
+    }
+    // STEREO mode: channel 0 = source channel 0; channel 1 = source channel 1, or channel 0
+    // duplicated when the source is mono (dual-mono, centered). extractChannel clamps the
+    // out-of-range channel request to the last channel, so a mono source yields L == R.
+    out.monoFrames = extractChannel(interleaved, sourceChannels, 0);
+    out.framesR = extractChannel(interleaved, sourceChannels, 1);
+    return out;
+}
+
+ZonePlayParams resolvePlay(const ZonePlaySeconds& stored, int sampleRate) {
+    // seconds -> frames at the LIVE rate (round-to-nearest). Wall-clock quantities (AHDSR A/H/D/R,
+    // pitch env A/D) resolve here; source-timeline quantities (trigger %-length + fades) carry
+    // through untouched — they are already source frames / fractions. Non-time fields pass as-is.
+    assert(sampleRate > 0 && "resolvePlay: sampleRate must be > 0 (programming error)");
+    const double sr = sampleRate > 0 ? static_cast<double>(sampleRate) : 1.0;  // 1.0 avoids div-by-zero; assert fires first
+    const auto secToFrames = [sr](double sec) {
+        double f = sec * sr;
+        if (f < 0.0) f = 0.0;
+        return static_cast<std::int64_t>(f + 0.5);
+    };
+    ZonePlayParams out;
+    out.playMode = stored.playMode;
+    out.adsr.attackFrames  = secToFrames(stored.adsr.attackSeconds);
+    out.adsr.holdFrames    = secToFrames(stored.adsr.holdSeconds);
+    out.adsr.decayFrames   = secToFrames(stored.adsr.decaySeconds);
+    out.adsr.sustainLevel  = stored.adsr.sustainLevel;   // level, not a time
+    out.adsr.releaseFrames = secToFrames(stored.adsr.releaseSeconds);
+    out.trigger = stored.trigger;                        // source-frame / fraction, unchanged
+    out.pitchEngine = stored.pitchEngine;
+    out.pitchEnv.enabled       = stored.pitchEnv.enabled;
+    out.pitchEnv.attackFrames  = secToFrames(stored.pitchEnv.attackSeconds);
+    out.pitchEnv.decayFrames   = secToFrames(stored.pitchEnv.decaySeconds);
+    out.pitchEnv.peakSemitones = stored.pitchEnv.peakSemitones;  // depth, not a time
+    return out;
+}
+
+Keymap buildTier0Keymap(std::vector<AudioSample> frames, int sampleRate,
+                        int rootNote, const SampleLoop& loop,
+                        std::vector<AudioSample> framesR, const ZonePlaySeconds& play) {
+    assert(sampleRate > 0 && "buildTier0Keymap: sampleRate must be > 0 (programming error)");
+    SampleData data;
+    data.frames = std::move(frames);
+    // A second channel only counts when it length-matches channel 0 (else the sample stays
+    // mono — SampleData::channelCount() enforces the same rule, so a bad pair never half-plays).
+    if (!framesR.empty() && framesR.size() == data.frames.size()) {
+        data.framesR = std::move(framesR);
+    }
+    if (sampleRate <= 0) return Keymap{};  // safe early-return; assert fires first
+    data.sampleRate = sampleRate;
+    data.rootNote = rootNote;
+    data.loop = loop;
+    // Resolve the stored wall-clock SECONDS to the engine's frame domain at the WAV's actual rate.
+    data.play = resolvePlay(play, data.sampleRate);
+
+    return Keymap::singleSampleChromatic(std::move(data));
+}
+
+// --- Performance map ---------------------------------------------------------
+
+ResolvedPerformance resolvePerformance(const std::string& banksJson,
+                                       const PerformanceMap& map) {
+    ResolvedPerformance out;
+    if (map.zones.empty()) return out;             // empty map -> empty (shell -> Tier 0)
+    if (banksJson.empty()) return out;             // no bank -> nothing resolves
+    std::optional<BankBook> book = BankBook::deserialize(banksJson);
+    if (!book) return out;                         // malformed -> nothing (never throw)
+
+    for (const PerformanceZone& z : map.zones) {
+        // Look the id up across every bank (pool + named) — a sample lives in exactly
+        // one bank, so first hit wins.
+        const Sample* found = nullptr;
+        for (const Bank& b : book->banks()) {
+            if (const Sample* s = b.index.query(z.sampleId)) {
+                found = s;
+                break;
+            }
+        }
+        if (!found) {
+            // STALE-ID POLICY: drop the zone cleanly, report the id (editor can prune).
+            out.droppedSampleIds.push_back(z.sampleId);
+            continue;
+        }
+        ResolvedZone rz;
+        rz.relativePath = found->relativePath;
+        rz.lowNote = z.lowNote;
+        rz.highNote = z.highNote;
+        // Effective root: override beats bank intrinsic beats middle-C default.
+        rz.rootNote = z.rootOverride ? *z.rootOverride
+                                     : (found->rootNote ? *found->rootNote : 60);
+        // Effective loop / start (S11): the instrument's per-zone override wins over the
+        // bank's S2 intrinsic; absent -> the intrinsic (loop) / frame 0 (start). The bank is
+        // never mutated — this only shapes what the core plays for THIS instance (D-B).
+        rz.loop = z.loopOverride ? *z.loopOverride : loopFromSample(*found);
+        rz.startFrame = z.startPoint ? *z.startPoint : 0;
+        // S15/S16 per-zone play params (SECONDS) carry through unchanged (they are instrument
+        // state, not resolved against the bank); buildZonedKeymap resolves them to frames.
+        rz.play = z.play;
+        out.zones.push_back(std::move(rz));
+    }
+    return out;
+}
+
+Keymap buildZonedKeymap(const std::vector<ResolvedZone>& zones,
+                        const std::vector<DecodedZonePcm>& decoded) {
+    Keymap km;
+    const std::size_t n = std::min(zones.size(), decoded.size());
+    for (std::size_t i = 0; i < n; ++i) {
+        // An unreadable/empty WAV drops just this zone (not the whole map).
+        if (decoded[i].monoFrames.empty()) continue;
+        SampleData data;
+        data.frames = decoded[i].monoFrames;
+        // Carry the second channel only when it length-matches channel 0 (channelCount()
+        // enforces the same rule; a mismatched pair falls back to mono rather than half-play).
+        if (!decoded[i].framesR.empty() &&
+            decoded[i].framesR.size() == data.frames.size()) {
+            data.framesR = decoded[i].framesR;
+        }
+        assert(decoded[i].sampleRate > 0 &&
+               "buildZonedKeymap: DecodedZonePcm::sampleRate must be > 0 (programming error)");
+        if (decoded[i].sampleRate <= 0) continue;  // safe skip; assert fires first
+        data.sampleRate = decoded[i].sampleRate;
+        data.rootNote = zones[i].rootNote;
+        data.loop = zones[i].loop;
+        data.startFrame = zones[i].startFrame;  // S11 effective start (override, else 0)
+        // Resolve the stored wall-clock SECONDS (AHDSR, pitch env A/D) to frames at THIS WAV's
+        // actual rate; source-timeline params (trigger %-length + fades, start) carry through.
+        data.play = resolvePlay(zones[i].play, data.sampleRate);
+        const std::size_t sampleIndex = km.samples.size();
+        km.samples.push_back(std::move(data));
+        KeyZone zone;
+        zone.lowNote = zones[i].lowNote;
+        zone.highNote = zones[i].highNote;
+        zone.rootNote = zones[i].rootNote;
+        zone.sampleIndex = sampleIndex;
+        km.zones.push_back(zone);
+    }
+    return km;  // empty zones in -> empty Keymap (silence)
+}
+
+// --- Performance-map instance state (setState/getState) -----------------------
+
+namespace {
+
+void putU32le(std::vector<std::uint8_t>& out, std::uint32_t v) {
+    out.push_back(static_cast<std::uint8_t>(v & 0xFF));
+    out.push_back(static_cast<std::uint8_t>((v >> 8) & 0xFF));
+    out.push_back(static_cast<std::uint8_t>((v >> 16) & 0xFF));
+    out.push_back(static_cast<std::uint8_t>((v >> 24) & 0xFF));
+}
+
+// 64-bit little-endian, for the S11 loop start/end + start frame (int64 on the wire as
+// two's-complement u64, mirroring the u32 signed-int idiom above).
+void putU64le(std::vector<std::uint8_t>& out, std::uint64_t v) {
+    for (int b = 0; b < 8; ++b) out.push_back(static_cast<std::uint8_t>((v >> (b * 8)) & 0xFF));
+}
+
+std::uint64_t asU64(std::int64_t v) { return static_cast<std::uint64_t>(v); }
+
+// IEEE-754 double <-> u64 bit-cast for the wire (memcpy is the only defined type-pun in C++).
+// Used for the S15/S16 trigger.lengthFraction + pitchEnv.peakSemitones fields.
+std::uint64_t doubleToBits(double d) {
+    std::uint64_t bits;
+    std::memcpy(&bits, &d, sizeof(bits));
+    return bits;
+}
+double bitsToDouble(std::uint64_t bits) {
+    double d;
+    std::memcpy(&d, &bits, sizeof(d));
+    return d;
+}
+
+// A bounded little-endian reader over a byte blob. Every read is length-checked; once a
+// read runs past the end the reader latches `ok=false` and yields zeros, so a truncated
+// blob degrades to a partial/empty parse rather than reading out of bounds.
+struct ByteReader {
+    const std::vector<std::uint8_t>& bytes;
+    std::size_t pos = 0;
+    bool ok = true;
+
+    explicit ByteReader(const std::vector<std::uint8_t>& b) : bytes(b) {}
+
+    std::uint32_t u32() {
+        if (!ok || pos + 4 > bytes.size()) { ok = false; return 0; }
+        const std::uint32_t v = static_cast<std::uint32_t>(bytes[pos]) |
+                                (static_cast<std::uint32_t>(bytes[pos + 1]) << 8) |
+                                (static_cast<std::uint32_t>(bytes[pos + 2]) << 16) |
+                                (static_cast<std::uint32_t>(bytes[pos + 3]) << 24);
+        pos += 4;
+        return v;
+    }
+    std::uint8_t u8() {
+        if (!ok || pos + 1 > bytes.size()) { ok = false; return 0; }
+        return bytes[pos++];
+    }
+    std::string str(std::uint32_t len) {
+        if (!ok || pos + len > bytes.size()) { ok = false; return {}; }
+        std::string s(reinterpret_cast<const char*>(bytes.data() + pos), len);
+        pos += len;
+        return s;
+    }
+    // Signed ints go on the wire as u32 two's-complement (fixed 32-bit width).
+    int i32() { return static_cast<int>(static_cast<std::int32_t>(u32())); }
+
+    std::uint64_t u64() {
+        if (!ok || pos + 8 > bytes.size()) { ok = false; return 0; }
+        std::uint64_t v = 0;
+        for (int b = 0; b < 8; ++b)
+            v |= static_cast<std::uint64_t>(bytes[pos + static_cast<std::size_t>(b)]) << (b * 8);
+        pos += 8;
+        return v;
+    }
+    // Signed 64-bit frame indices go on the wire as u64 two's-complement (fixed width).
+    std::int64_t i64() { return static_cast<std::int64_t>(u64()); }
+
+    // Non-consuming peek of the next u32 (for the zones-payload format-marker probe). Yields
+    // 0 and latches nothing when fewer than 4 bytes remain — the caller treats a short blob
+    // as "no marker" and falls through to the (also-guarded) v1 count read.
+    std::uint32_t peekU32() const {
+        if (!ok || pos + 4 > bytes.size()) return 0;
+        return static_cast<std::uint32_t>(bytes[pos]) |
+               (static_cast<std::uint32_t>(bytes[pos + 1]) << 8) |
+               (static_cast<std::uint32_t>(bytes[pos + 2]) << 16) |
+               (static_cast<std::uint32_t>(bytes[pos + 3]) << 24);
+    }
+};
+
+// Append the zones payload — the shared body of the performance blob and the component blob,
+// so both write zones identically. Always emits the CURRENT PAYLOAD version (kZonesPayloadVersion
+// == v5: the S11 self-describing marker + version + EXTENDED records carrying the loop/start tail
+// AND the full play-params tail with wall-clock times stored as SECONDS): the marker precedes
+// the zone count so any reader can detect the record shape independently of the envelope version
+// (see sample_map.h). The S11 loop/start overrides and the play params therefore round-trip
+// through EITHER envelope with no envelope bump.
+void putZonesPayload(std::vector<std::uint8_t>& out, const PerformanceMap& map) {
+    putU32le(out, kZonesFormatMarker);
+    putU32le(out, kZonesPayloadVersion);
+    putU32le(out, static_cast<std::uint32_t>(map.zones.size()));
+    for (const PerformanceZone& z : map.zones) {
+        putU32le(out, static_cast<std::uint32_t>(z.sampleId.size()));
+        out.insert(out.end(), z.sampleId.begin(), z.sampleId.end());
+        putU32le(out, static_cast<std::uint32_t>(static_cast<std::int32_t>(z.lowNote)));
+        putU32le(out, static_cast<std::uint32_t>(static_cast<std::int32_t>(z.highNote)));
+        out.push_back(z.rootOverride ? 1 : 0);
+        if (z.rootOverride) {
+            putU32le(out,
+                     static_cast<std::uint32_t>(static_cast<std::int32_t>(*z.rootOverride)));
+        }
+        // S11 extension: loop override (hasLoop flag + start/end), then start point.
+        out.push_back(z.loopOverride ? 1 : 0);
+        if (z.loopOverride) {
+            out.push_back(z.loopOverride->hasLoop ? 1 : 0);
+            putU64le(out, asU64(z.loopOverride->start));
+            putU64le(out, asU64(z.loopOverride->end));
+        }
+        out.push_back(z.startPoint ? 1 : 0);
+        if (z.startPoint) putU64le(out, asU64(*z.startPoint));
+
+        // S15/S16 play params (PAYLOAD v5): always present (every zone has a play mode + engine).
+        // Wall-clock times are SECONDS (doubles); trigger %-length + fades stay source frames /
+        // fraction. Order matches the header's v5 record spec.
+        const ZonePlaySeconds& pp = z.play;
+        out.push_back(pp.playMode == PlayMode::Trigger ? 1 : 0);
+        putU64le(out, doubleToBits(pp.adsr.holdSeconds));           // wall-clock seconds
+        putU64le(out, doubleToBits(pp.trigger.lengthFraction));      // fraction
+        putU64le(out, asU64(pp.trigger.fadeInFrames));               // source frames
+        putU64le(out, asU64(pp.trigger.fadeOutFrames));              // source frames
+        out.push_back(pp.pitchEngine == PitchEngine::Preserve ? 1 : 0);
+        out.push_back(pp.pitchEnv.enabled ? 1 : 0);
+        putU64le(out, doubleToBits(pp.pitchEnv.attackSeconds));      // wall-clock seconds
+        putU64le(out, doubleToBits(pp.pitchEnv.decaySeconds));       // wall-clock seconds
+        putU64le(out, doubleToBits(pp.pitchEnv.peakSemitones));      // depth
+        // Full AHDSR A/D/S/R tail — wall-clock SECONDS (sustainLevel is a level).
+        putU64le(out, doubleToBits(pp.adsr.attackSeconds));
+        putU64le(out, doubleToBits(pp.adsr.decaySeconds));
+        putU64le(out, doubleToBits(pp.adsr.sustainLevel));
+        putU64le(out, doubleToBits(pp.adsr.releaseSeconds));
+    }
+}
+
+// Read a zones payload from `r` into `map`. Shared by the performance parse and the component
+// parse. Detects the S11 format marker: present -> PAYLOAD v2 (extended records with the
+// loop/start tail); absent (a plain small zone count) -> PAYLOAD v1 (pre-S11 records, no tail —
+// clean back-compat lift, the overrides simply default absent). A truncated mid-zone read
+// keeps the zones that parsed cleanly and drops the rest.
+// `projectRate` is the live host/project sample rate used to convert LEGACY v3 wall-clock frame
+// counts (holdFrames, pitchEnv A/D) to the seconds domain at the read boundary: seconds = frames /
+// projectRate. Must be > 0 (callers guard). v5 and later blobs carry seconds directly; no rate needed.
+void readZonesPayload(ByteReader& r, PerformanceMap& map, double projectRate) {
+    bool extended = false;    // v2+: the S11 loop/start tail is present
+    std::uint32_t pv = 0;     // payload version (0 = v1, no marker)
+    if (r.peekU32() == kZonesFormatMarker) {
+        r.u32();                      // consume the marker
+        pv = r.u32();                 // payload version
+        extended = (pv >= 2);         // v2+ carries the loop/start tail
+    }
+    const bool legacyV3Play = (pv == 3);  // legacy S15/S16 play tail, wall-clock in 44.1k frames
+    const bool secondsPlay  = (pv >= 5);  // current: full play params, wall-clock in seconds
+    const std::uint32_t count = r.u32();
+    for (std::uint32_t i = 0; i < count && r.ok; ++i) {
+        // z.play defaults to the PRODUCT defaults (Gate + Preserve + tier-0 AHDSR seconds). A
+        // v1/v2 payload (no play tail) therefore lifts every zone to those defaults (S16-F1).
+        PerformanceZone z;
+        const std::uint32_t idLen = r.u32();
+        z.sampleId = r.str(idLen);
+        z.lowNote = r.i32();
+        z.highNote = r.i32();
+        const std::uint8_t hasOverride = r.u8();
+        if (hasOverride) z.rootOverride = r.i32();
+        if (extended) {
+            const std::uint8_t hasLoop = r.u8();
+            if (hasLoop) {
+                SampleLoop lp;
+                lp.hasLoop = (r.u8() != 0);
+                lp.start = r.i64();
+                lp.end = r.i64();
+                z.loopOverride = lp;
+            }
+            const std::uint8_t hasStart = r.u8();
+            if (hasStart) z.startPoint = r.i64();
+        }
+        if (legacyV3Play) {
+            // LEGACY v3 play tail (Daniel's beta projects). Wall-clock fields (hold, pitchEnv A/D)
+            // were written as frames -> divide by the project sample rate (threaded in as `projectRate`)
+            // to reach the seconds domain. Trigger %-length + fades are source-timeline, read as-is.
+            // A/D/S/R are ABSENT in v3 -> leave the seconds defaults on z.play.adsr.
+            assert(projectRate > 0.0 && "readZonesPayload: projectRate must be > 0 for v3 lift");
+            const double liftRate = projectRate > 0.0 ? projectRate : 1.0;  // 1.0 avoids div-by-zero; assert fires first
+            z.play.playMode = (r.u8() != 0) ? PlayMode::Trigger : PlayMode::Gate;
+            z.play.adsr.holdSeconds = static_cast<double>(r.i64()) / liftRate;
+            z.play.trigger.lengthFraction = bitsToDouble(r.u64());
+            z.play.trigger.fadeInFrames = r.i64();
+            z.play.trigger.fadeOutFrames = r.i64();
+            z.play.pitchEngine = (r.u8() != 0) ? PitchEngine::Preserve : PitchEngine::Varispeed;
+            z.play.pitchEnv.enabled = (r.u8() != 0);
+            z.play.pitchEnv.attackSeconds = static_cast<double>(r.i64()) / liftRate;
+            z.play.pitchEnv.decaySeconds  = static_cast<double>(r.i64()) / liftRate;
+            z.play.pitchEnv.peakSemitones = bitsToDouble(r.u64());
+        } else if (secondsPlay) {
+            // Current v5 play tail: wall-clock times in SECONDS (doubles); trigger fades in source
+            // frames; read in the emit order.
+            z.play.playMode = (r.u8() != 0) ? PlayMode::Trigger : PlayMode::Gate;
+            z.play.adsr.holdSeconds = bitsToDouble(r.u64());
+            z.play.trigger.lengthFraction = bitsToDouble(r.u64());
+            z.play.trigger.fadeInFrames = r.i64();
+            z.play.trigger.fadeOutFrames = r.i64();
+            z.play.pitchEngine = (r.u8() != 0) ? PitchEngine::Preserve : PitchEngine::Varispeed;
+            z.play.pitchEnv.enabled = (r.u8() != 0);
+            z.play.pitchEnv.attackSeconds = bitsToDouble(r.u64());
+            z.play.pitchEnv.decaySeconds  = bitsToDouble(r.u64());
+            z.play.pitchEnv.peakSemitones = bitsToDouble(r.u64());
+            z.play.adsr.attackSeconds  = bitsToDouble(r.u64());
+            z.play.adsr.decaySeconds   = bitsToDouble(r.u64());
+            z.play.adsr.sustainLevel   = bitsToDouble(r.u64());
+            z.play.adsr.releaseSeconds = bitsToDouble(r.u64());
+        }
+        // Payload versions 4 (branch-only frames tail, never shipped) and any unknown pv leave the
+        // seconds product defaults on z.play — a v4 blob cannot exist outside this branch.
+        if (!r.ok) break;  // truncated mid-zone -> keep what parsed cleanly, drop the rest
+        map.zones.push_back(std::move(z));
+    }
+}
+
+}  // namespace
+
+std::vector<std::uint8_t> serializePerformance(const PerformanceMap& map) {
+    std::vector<std::uint8_t> out;
+    putU32le(out, kPerformanceStateVersion);
+    putZonesPayload(out, map);
+    return out;
+}
+
+PerformanceMap deserializePerformance(const std::vector<std::uint8_t>& bytes,
+                                      double projectRate) {
+    // projectRate is only consumed by readZonesPayload when a LEGACY v3 payload is present.
+    // For v5 and later blobs it is unused. The assert inside readZonesPayload fires if a v3
+    // blob is encountered with an invalid rate — the calller guarantees a real rate before use.
+    PerformanceMap map;
+    ByteReader r(bytes);
+    const std::uint32_t version = r.u32();
+    if (!r.ok) return map;  // no version tag -> empty
+
+    // BACK-COMPAT: a v1 blob is the S4 single-selection format (version 1 + id bytes,
+    // no length prefix). Lift it to one full-keyboard zone playing that id.
+    if (version == kSelectionStateVersion) {
+        const std::string id = deserializeSelection(bytes);
+        if (!id.empty()) {
+            PerformanceZone z;
+            z.sampleId = id;
+            z.lowNote = 0;
+            z.highNote = 127;
+            map.zones.push_back(std::move(z));
+        }
+        return map;
+    }
+    if (version != kPerformanceStateVersion) return map;  // unknown -> empty
+
+    readZonesPayload(r, map, projectRate);
+    return map;
+}
+
+// --- Combined component state (v3, S10) --------------------------------------
+
+std::vector<std::uint8_t> serializeComponentState(const ComponentState& state) {
+    std::vector<std::uint8_t> out;
+    putU32le(out, kComponentStateVersion);
+    // v4 envelope addition: the channel mode (0 = mono, 1 = stereo) precedes the v3 body.
+    out.push_back(state.channelMode == ChannelMode::Stereo ? 1 : 0);
+    // v5 envelope addition (S8/S9 reader): the last-consumed assignment generation, 8-byte LE
+    // two's-complement, precedes the selection id. Follows the mode byte so a v4 reader that
+    // stops at the mode byte is a strict prefix (see the v4 lift below).
+    putU64le(out, asU64(state.lastConsumedAssignGeneration));
+    // Length-prefixed selection id (it precedes the zones payload, so it MUST be framed —
+    // unlike the v1 selection blob where the id ran to end-of-stream).
+    putU32le(out, static_cast<std::uint32_t>(state.selectionId.size()));
+    out.insert(out.end(), state.selectionId.begin(), state.selectionId.end());
+    putZonesPayload(out, state.map);
+    return out;
+}
+
+ComponentState deserializeComponentState(const std::vector<std::uint8_t>& bytes,
+                                         double projectRate) {
+    // projectRate is only consumed by readZonesPayload when a LEGACY v3 payload is present.
+    // For v5 and later blobs it is unused. See readZonesPayload for the guard.
+    ComponentState out;
+    ByteReader r(bytes);
+    const std::uint32_t version = r.u32();
+    if (!r.ok) return out;  // no version tag -> empty (the S10 silent empty state)
+
+    // BACK-COMPAT: an older blob predates the v3 {selection, zones} split.
+    //   * v1 (S4 single-selection: version 1 + id-to-end): restore {id, one full-keyboard
+    //     zone} so the old pick survives as BOTH the selection and a one-zone map.
+    //   * v2 (S5 zones-only): restore {"", zones} — that instance had zones but no separate
+    //     single-capture selection.
+    if (version == kSelectionStateVersion) {
+        out.selectionId = deserializeSelection(bytes);
+        if (!out.selectionId.empty()) {
+            PerformanceZone z;
+            z.sampleId = out.selectionId;
+            z.lowNote = 0;
+            z.highNote = 127;
+            out.map.zones.push_back(std::move(z));
+        }
+        return out;
+    }
+    if (version == kPerformanceStateVersion) {
+        readZonesPayload(r, out.map, projectRate);  // v2 body starts right after the version tag
+        return out;                                 // channelMode stays Mono (pre-S7)
+    }
+    // BACK-COMPAT: a v3 blob (pre-S7 {selection, zones}, no channel mode) restores as MONO —
+    // the id length + id + zones body starts right after the version tag (no mode byte).
+    if (version == kSelectionZonesV3Version) {
+        const std::uint32_t idLen = r.u32();
+        out.selectionId = r.str(idLen);
+        if (!r.ok) { out.selectionId.clear(); return out; }  // truncated id -> empty
+        readZonesPayload(r, out.map, projectRate);
+        return out;                    // channelMode stays Mono, marker stays 0 (pre-S7/S8/S9)
+    }
+    // BACK-COMPAT: a v4 blob (pre-S8/S9 reader {mode, selection, zones}, no consumed marker):
+    // mode byte, then the id + zones body — no 8-byte marker. lastConsumedAssignGeneration
+    // defaults to 0, so a first assign still applies for a pre-marker instance.
+    if (version == kSelectionZonesModeV4Version) {
+        const std::uint8_t modeByte = r.u8();
+        if (!r.ok) return out;  // truncated before the mode byte -> empty (mono default holds)
+        out.channelMode = (modeByte == 1) ? ChannelMode::Stereo : ChannelMode::Mono;
+        const std::uint32_t idLen = r.u32();
+        out.selectionId = r.str(idLen);
+        if (!r.ok) { out.selectionId.clear(); return out; }  // truncated id -> empty
+        readZonesPayload(r, out.map, projectRate);
+        return out;                    // marker stays 0 (pre-S8/S9 reader)
+    }
+    if (version != kComponentStateVersion) return out;  // unknown -> empty
+
+    // v5: the channel-mode byte, then the 8-byte consumed-assignment marker, precede the v3
+    // body. A non-{0,1} mode byte is treated as mono (conservative default) rather than
+    // rejected — a corrupt mode never silences the instance.
+    const std::uint8_t modeByte = r.u8();
+    if (!r.ok) return out;  // truncated before the mode byte -> empty (mono default holds)
+    out.channelMode = (modeByte == 1) ? ChannelMode::Stereo : ChannelMode::Mono;
+    out.lastConsumedAssignGeneration = r.i64();
+    if (!r.ok) return out;  // truncated before/inside the marker -> empty (marker 0 holds)
+    const std::uint32_t idLen = r.u32();
+    out.selectionId = r.str(idLen);
+    if (!r.ok) { out.selectionId.clear(); return out; }  // truncated id -> empty
+    readZonesPayload(r, out.map, projectRate);
+    return out;
+}
+
+std::vector<std::uint8_t> serializeSelection(const std::string& sampleId) {
+    std::vector<std::uint8_t> out;
+    out.resize(4 + sampleId.size());
+    const std::uint32_t v = kSelectionStateVersion;
+    out[0] = static_cast<std::uint8_t>(v & 0xFF);
+    out[1] = static_cast<std::uint8_t>((v >> 8) & 0xFF);
+    out[2] = static_cast<std::uint8_t>((v >> 16) & 0xFF);
+    out[3] = static_cast<std::uint8_t>((v >> 24) & 0xFF);
+    std::memcpy(out.data() + 4, sampleId.data(), sampleId.size());
+    return out;
+}
+
+std::string deserializeSelection(const std::vector<std::uint8_t>& bytes) {
+    if (bytes.size() < 4) return {};  // no version tag -> no selection
+    const std::uint32_t v = static_cast<std::uint32_t>(bytes[0]) |
+                            (static_cast<std::uint32_t>(bytes[1]) << 8) |
+                            (static_cast<std::uint32_t>(bytes[2]) << 16) |
+                            (static_cast<std::uint32_t>(bytes[3]) << 24);
+    if (v != kSelectionStateVersion) return {};  // unknown version -> ignore
+    return std::string(reinterpret_cast<const char*>(bytes.data() + 4),
+                       bytes.size() - 4);
+}
+
+}  // namespace reasampler

src/vst/sample_map.h

@@ -0,0 +1,468 @@
+#pragma once
+// sample_map — PURE mapping logic for the S4 Tier-0 instrument: turn the live
+// "reasampler" bank ext-state + a decoded WAV into the plain data the sampler core
+// plays, and (de)serialize the instance's selected-sample choice for VST3 component
+// state. NO VST3, NO REAPER, NO SWELL, NO vendor/ includes at the boundary — the
+// mirror of capture_paths / wav_trim / bridge_marshal splitting the fiddly, testable
+// arithmetic out of a host-facing shell.
+//
+// WHY IT EXISTS (S4 seams). The instrument reads the bank over the live-state seam
+// (the "banks" ext-state blob) and the audio over the file seam (the on-disk WAV).
+// Both of those raw inputs cross the bridge/file boundary in the shell; everything
+// after — parse the bank with the SHARED bank_model/bank_book JSON path (NOT a second
+// parser; the S1 spike's string-scan reader is retired), pick the selected sample,
+// downmix its decoded PCM to the core's mono contract, and build the Tier-0 chromatic
+// Keymap — is pure and unit-tested here.
+//
+// It links bank_book (the shared BankBook::deserialize) and wav_trim (the shared
+// 32-bit-float WAV parse — no third WAV reader) and sampler_core (the Keymap /
+// SampleData it produces). All three are pure; this stays pure.
+
+#include <cstdint>
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "bank_book.h"       // BankBook::deserialize (shared bank JSON parse)
+#include "sampler_core.h"    // Keymap, SampleData, SampleLoop
+#include "wav_trim.h"        // parseWavLayout, extractFloatFrames (shared WAV parse)
+
+namespace reasampler {
+
+// The bank sample this instance is bound to, distilled from the live "banks" blob:
+// the project-relative WAV path the file seam must resolve+decode, plus the S2 bank
+// intrinsics the core repitches / loops by. A pure value — no host, no PCM yet.
+struct SelectedSample {
+    std::string relativePath;   // project-relative; the shell resolves it (M4 convention)
+    int rootNote = 60;          // S2 intrinsic; defaults to middle C when the bank left it empty
+    SampleLoop loop;            // S2 intrinsic; hasLoop=false when the bank left it empty
+};
+
+// Resolve the bound sample from the live bank blob. `banksJson` is the raw "banks"
+// ext-state value the bridge read (may be empty / malformed — an unsaved or pre-bank
+// project). `sampleId` is this instance's stored selection.
+//
+// Precedence, all pure:
+//   * empty / malformed banksJson            -> nullopt (nothing to play)
+//   * sampleId empty                         -> nullopt (NO selection -> silence)
+//   * sampleId names a sample in ANY bank    -> that sample (searched pool + named)
+//   * sampleId set but not found (stale)     -> nullopt (the sample was deleted/moved;
+//                                                the editor returns to the empty state)
+//
+// POLICY REVERSAL (S10, 2026-07-26 — supersedes the S4 first-sample fallback). A fresh
+// instance with no stored selection resolves to nullopt (SILENCE), NOT the bank's first
+// sample: the metric is time-to-first-note via an explicit pick, and a mystery auto-play
+// of sample #1 was the anti-pattern. A stale stored id (no longer resolves) ALSO returns
+// nullopt rather than silently substituting a different sample — the editor reflects the
+// missing selection with its "pick a capture" empty state instead of masking it.
+std::optional<SelectedSample> selectSample(const std::string& banksJson,
+                                           const std::string& sampleId);
+
+// One entry in the capture browser's card list: the stable id + display name plus the S2
+// intrinsics + bank the browser draws as a card (peak thumbnail + name + root/key badge,
+// filterable by bank). Peaks are NOT here — they are computed shell-side from the decoded
+// PCM (the `Sample` metadata carries no envelope; see reasampler_editor's thumbnail cache,
+// the mirror of bank_panel::thumbnailFor). This carries only what the bank blob already
+// holds: the metadata the card badge + bank filter need. Pure projection over the shared
+// parse — the UI never parses JSON itself.
+//
+//  - rootNote:  the S2 rootNote intrinsic when the bank set it (nullopt otherwise — the
+//               badge shows "root: —" / no root, never a guessed value).
+//  - key:       the optional human musical key label ("F#m"), when the bank set it.
+//  - bankId:    the id of the bank this sample lives in (the bank filter matches on it).
+struct SampleChoice {
+    std::string id;
+    std::string displayName;
+    std::optional<int> rootNote;
+    std::optional<std::string> key;
+    std::string bankId;
+};
+std::vector<SampleChoice> listSamples(const std::string& banksJson);
+
+// One bank the filter tab strip offers: its stable id + display name, in ordinal order
+// (pool first). The browser prepends an "All" tab (no id) shell-side. Empty for an empty /
+// malformed blob. Pure projection over the shared parse.
+struct BankChoice {
+    std::string id;
+    std::string displayName;
+};
+std::vector<BankChoice> listBanks(const std::string& banksJson);
+
+// Downmix interleaved float frames (the shape wav_trim::extractFloatFrames yields:
+// [f0c0,f0c1,...,f1c0,...]) to the core's MONO contract by AVERAGING channels per
+// frame. `channelCount` is the interleave stride (>= 1). CHANNEL POLICY (Tier 0,
+// documented + surfaced): the S3 core is mono-per-sample by design; bank WAVs preserve
+// their source channel count, so a stereo (or N-channel) capture is folded to a single
+// mono stream here by an equal-weight average. Averaging (not "take L", not summing) is
+// the least-surprising, no-clip default — a centered mono source stays unity, and a
+// hard-panned source is attenuated rather than silenced or doubled. Empty / zero-stride
+// in -> empty out. Pure.
+std::vector<AudioSample> downmixToMono(const std::vector<AudioSample>& interleaved,
+                                       int channelCount);
+
+// Deinterleave one channel (`which`, 0-based) out of interleaved frames. `channelCount` is
+// the interleave stride (>= 1); `which` is clamped to a valid channel (a request past the
+// source's last channel reads the last channel, so a mono source asked for channel 1 yields
+// channel 0 again — the dual-mono building block). Empty / zero-stride in -> empty out. Pure.
+std::vector<AudioSample> extractChannel(const std::vector<AudioSample>& interleaved,
+                                        int channelCount, int which);
+
+// --- Stored (wall-clock SECONDS) per-zone play params -------------------------
+//
+// DOMAIN SPLIT (S12 remediation — Daniel's ruling: no hardcoded sample rate in the program).
+// The instrument stores and edits WALL-CLOCK performance times as SECONDS, rate-free; the
+// engine (sampler_core's ZonePlayParams, on SampleData) receives FRAMES resolved from the
+// LIVE sample rate at keymap build. AHDSR (A/H/D/S/R) and the AD pitch envelope (attack/decay)
+// are wall-clock — the voice advances them once per OUTPUT frame — so they live here in seconds.
+// Quantities anchored to the source file's timeline (start point, loop points, Trigger %-length
+// and its fades — the fades anchor to the source-frame read offset, PLAN.md §S15) stay in source
+// frames / fractions and are carried through unchanged (TriggerParams is reused verbatim).
+//
+// The stored AHDSR times (seconds). sustainLevel is dimensionless (0..1), not a time.
+struct AdsrSeconds {
+    double attackSeconds  = 0.003;  // tier-0 default
+    double holdSeconds    = 0.0;
+    double decaySeconds   = 0.0;
+    double sustainLevel   = 1.0;
+    double releaseSeconds = 0.060;  // tier-0 default
+};
+
+// The stored AD pitch-envelope times (seconds). enabled + peakSemitones are dimensionless.
+struct PitchEnvSeconds {
+    bool   enabled       = false;
+    double attackSeconds = 0.0;
+    double decaySeconds  = 0.0;
+    double peakSemitones = 0.0;    // signed depth at the peak
+};
+
+// The stored per-zone play bundle: wall-clock times in SECONDS, source-timeline quantities in
+// frames/fractions (TriggerParams). This is the instrument-owned (D-B), serialized, editor-facing
+// representation — distinct from sampler_core's engine-facing ZonePlayParams (frames). The keymap
+// builders resolve this to a frame-domain ZonePlayParams against the live sample rate.
+struct ZonePlaySeconds {
+    PlayMode        playMode = PlayMode::Gate;
+    AdsrSeconds     adsr;                                  // Gate: AHDSR (seconds)
+    TriggerParams   trigger;                              // Trigger: %-length + fades (source frames)
+    PitchEngine     pitchEngine = kDefaultPitchEngine;    // product default: Preserve (S16-F1)
+    PitchEnvSeconds pitchEnv;                             // AD pitch modulation (seconds), off by default
+};
+
+// Resolve a stored seconds bundle to the engine's frame-domain ZonePlayParams against a live
+// sample rate (frames = round(seconds * rate)). Source-timeline fields (trigger, engine, mode,
+// peak, enabled) carry through unchanged. `sampleRate` must be > 0 (the caller guards this).
+ZonePlayParams resolvePlay(const ZonePlaySeconds& stored, int sampleRate);
+
+// Build the Tier-0 chromatic keymap for one decoded sample: one zone spanning the whole
+// keyboard, repitched from `rootNote`, looped per `loop`. The single-sample degenerate case
+// (Keymap::singleSampleChromatic) with the S2 intrinsics threaded in. `frames` is channel 0
+// (mono, or L); `framesR` is channel 1 (R) — pass EMPTY for a mono sample (the default),
+// which yields a mono SampleData byte-identical to the pre-S7 build. A `framesR` whose length
+// mismatches `frames` is dropped (SampleData::channelCount() falls back to mono), so a bad
+// pair never half-plays. `sampleRate` is the WAV's rate.
+// `play` carries the S15/S16 per-zone play params (SECONDS) for the single-capture path; it
+// defaults to the PRODUCT defaults (Gate + tier-0 AHDSR seconds + Preserve engine, S16-F1) so a
+// picked single capture plays under the same default engine as a zone would. This function
+// resolves the wall-clock seconds to frames against `sampleRate` before stamping the SampleData.
+Keymap buildTier0Keymap(std::vector<AudioSample> frames, int sampleRate,
+                        int rootNote, const SampleLoop& loop,
+                        std::vector<AudioSample> framesR = {},
+                        const ZonePlaySeconds& play = ZonePlaySeconds{});
+
+// --- Performance map (Tier 1, D-B: the instrument's OWN state) ---------------
+//
+// The performance map is the keymap the user authors IN the instrument: several bank
+// samples zoned across the keyboard, each with a key range and a root note. It is a
+// PERFORMANCE CHOICE (D-B), so it lives in the instrument (VST3 component state), never
+// written back to the bank. Root note per zone is SEEDED from the S2 bank intrinsic but
+// OVERRIDABLE here — the override lives on the zone, never on `Sample`.
+//
+// Pure value type: it names bank samples by id (the stable seam key) and holds no PCM.
+// The shell resolves each id's WAV over the file seam and decodes it; the pure zone-build
+// stitches the decoded frames + this map into a sampler_core Keymap.
+
+// One authored zone: a bank sample mapped to an inclusive [lowNote, highNote] key range,
+// with an optional root-note override. rootOverride absent -> repitch from the bank
+// sample's own S2 rootNote intrinsic (or middle C when the bank left it empty).
+//
+// S11 loop/start overrides (instrument-owned, D-B — mirror of rootOverride): the sustain
+// loop and the initial read position are FACTS about the file (S2 bank intrinsics), but the
+// instrument may override them per zone WITHOUT writing back to the bank. loopOverride wins
+// over the bank's S2 loop intrinsic when set; startPoint sets the voice's initial read frame
+// (absent -> frame 0). Both are seeded from the bank intrinsic in the editor and stored here;
+// resolvePerformance folds override-beats-intrinsic into the effective ResolvedZone.
+struct PerformanceZone {
+    std::string sampleId;             // bank sample id this zone plays
+    int lowNote = 0;                  // inclusive
+    int highNote = 127;               // inclusive
+    std::optional<int> rootOverride;  // instrument-owned override; absent -> bank intrinsic
+    std::optional<SampleLoop> loopOverride;  // instrument-owned sustain loop; absent -> bank intrinsic
+    std::optional<std::int64_t> startPoint;  // instrument-owned initial read frame; absent -> 0
+
+    // S15/S16 per-zone play parameters (play mode + AHDSR + Trigger %-length/fades; pitch
+    // engine + AD pitch envelope). Instrument-owned (D-B), never a bank fact — mirror of the
+    // loop/start overrides. Wall-clock times are stored in SECONDS (rate-free); the keymap build
+    // resolves them to frames at the live sample rate. Defaults to the PRODUCT defaults for a NEW
+    // zone: Gate play mode, tier-0 AHDSR seconds (0.003 attack / 0.060 release), hold 0, no fades,
+    // PRESERVE pitch engine (S16-F1), pitch env off. An older zone-payload blob (no S15/S16 tail)
+    // lifts to exactly these defaults on read (see the PAYLOAD versioning).
+    ZonePlaySeconds play;
+};
+
+// The instrument's performance map: an ordered list of zones. Order is authoritative for
+// overlap resolution (OVERLAP POLICY: first zone in order wins, mirroring the S3 core's
+// first-match Keymap::resolve — overlaps are neither rejected nor clamped, the earlier
+// zone simply takes the contested keys; documented, deterministic).
+struct PerformanceMap {
+    std::vector<PerformanceZone> zones;
+
+    bool empty() const { return zones.empty(); }
+};
+
+// One resolved zone ready for the shell to decode + the pure build to stitch: the bank
+// sample's project-relative WAV path (file seam), the EFFECTIVE root note (override beats
+// bank intrinsic beats middle-C default), the loop intrinsic, and the key range. Distinct
+// from PerformanceZone (which names an id) — this is the id resolved against the live bank.
+struct ResolvedZone {
+    std::string relativePath;   // project-relative; the shell resolves + decodes it
+    int lowNote = 0;
+    int highNote = 127;
+    int rootNote = 60;          // effective: override, else bank intrinsic, else 60
+    SampleLoop loop;            // effective: loopOverride, else bank S2 intrinsic (S11)
+    std::int64_t startFrame = 0;  // effective initial read frame: startPoint, else 0 (S11)
+    ZonePlaySeconds play;  // S15/S16 per-zone play params (SECONDS; resolved to frames at build)
+};
+
+// The result of resolving a performance map against the live bank blob. `zones` are the
+// zones whose sampleId still resolves to a bank sample, IN MAP ORDER (so overlap-order is
+// preserved). `droppedSampleIds` are the ids that no longer resolve (STALE-ID POLICY: a
+// zone naming a deleted/moved-out sample is DROPPED cleanly — not an error, not silence
+// for the whole map — and its id is reported here so the editor can flag/prune it).
+struct ResolvedPerformance {
+    std::vector<ResolvedZone> zones;
+    std::vector<std::string> droppedSampleIds;
+};
+
+// Resolve a performance map against the live "banks" ext-state blob. Pure: shared
+// bank_book parse, no host, no PCM. Each zone's sampleId is looked up across every bank
+// (pool + named); a hit yields a ResolvedZone with the effective root note (rootOverride,
+// else the sample's S2 rootNote, else 60) and the sample's loop intrinsic; a miss appends
+// the id to droppedSampleIds. Empty/malformed blob or empty map -> empty result (the shell
+// then falls back to Tier-0 — see reloadFromBank).
+ResolvedPerformance resolvePerformance(const std::string& banksJson,
+                                       const PerformanceMap& map);
+
+// Build a zoned Keymap from resolved zones + their decoded mono PCM. `decoded[i]` is the
+// downmixed frames + sample rate for `zones[i]` (same length + order as `zones`). One
+// SampleData per zone (Tier 1: one sample per key-region; a sample used by two zones is
+// decoded twice — acceptable at this tier, the shell may dedup by path later). Zone order
+// is preserved so first-match overlap resolution matches the map's authored order. A zone
+// whose decoded frames are empty is SKIPPED (an unreadable WAV drops the zone, not the
+// map). Empty zones in -> empty Keymap (silence).
+struct DecodedZonePcm {
+    std::vector<AudioSample> monoFrames;   // channel 0 (mono, or L of a stereo decode)
+    int sampleRate = 0;                    // 0 is explicitly invalid; every consumer must
+                                           // receive the WAV's real rate before use.
+    std::vector<AudioSample> framesR;      // channel 1 (R); EMPTY for a mono decode
+};
+Keymap buildZonedKeymap(const std::vector<ResolvedZone>& zones,
+                        const std::vector<DecodedZonePcm>& decoded);
+
+// Apply the S7 cross-mode channel policy (D-E) to freshly-decoded interleaved PCM, yielding
+// the 1- or 2-channel DecodedZonePcm the keymap build consumes. `interleaved` is the WAV's
+// float frames (stride = `sourceChannels`); `mode` is the instance's channel mode.
+//   * MONO mode           -> downmix to one channel (the existing policy: average all source
+//                            channels). framesR EMPTY. A mono or stereo source both collapse.
+//   * STEREO mode, mono src   -> DUAL-MONO: channel 0 duplicated into channel 1 (centered).
+//   * STEREO mode, stereo src -> channels 0 and 1 taken as-is (L/R). A source with >2 channels
+//                            takes channels 0 and 1 (documented; the sampler's stereo image is
+//                            the first two channels — no surround fold).
+// Empty / zero-channel input -> a DecodedZonePcm with empty frames (the caller drops the zone
+// or plays silence). Pure — the shell does the file I/O and hands the interleaved buffer here.
+DecodedZonePcm decodeChannels(const std::vector<AudioSample>& interleaved,
+                              int sourceChannels, ChannelMode mode, int sampleRate);
+
+// --- Performance-map instance state (VST3 setState/getState) -----------------
+//
+// The performance map is the instrument's OWN state (D-B), serialized to the VST3
+// component-state IBStream — NOT written to the "reasampler" bank ext-state (the
+// instrument is a read-only bank consumer; S4 precedent). Versioned binary, tolerant of
+// truncation/wrong-version by design (bounded reads, never throws across the host).
+//
+// Format: 4-byte LE ENVELOPE version tag (== kPerformanceStateVersion, == 2), then the
+// ZONES PAYLOAD.
+//
+// ZONES-PAYLOAD FORMAT VERSIONING (S11 — self-describing, envelope-independent). The zones
+// payload carries its OWN version so the per-zone record can grow (S11's loop/start overrides)
+// WITHOUT bumping the envelope version — the envelope (this v2 blob and the v3 ComponentState
+// below, and S7's forthcoming v4) simply wraps whatever payload version it holds. This is the
+// key composition property: the zone-record extension is versioned inside the map blob, not on
+// the envelope, so S11 (zone-record fields) and S7 (envelope v4 for channel mode) do not
+// collide on a single version number.
+//   * PAYLOAD v1 (pre-S11, on-the-wire shipped): 4-byte LE zone count, then per zone:
+//       4-byte LE id length, id bytes, 4-byte LE lowNote, 4-byte LE highNote,
+//       1 byte hasRootOverride (0/1), 4-byte LE rootOverride (present iff hasRootOverride).
+//     A payload starting with a small u32 (the zone count) is v1 — there is no marker.
+//   * PAYLOAD v2 (S11): a 4-byte LE MARKER (kZonesFormatMarker, a high sentinel no real zone
+//     count can equal) + a 4-byte LE payload version (== 2), THEN the v1 body PLUS, appended
+//     to each zone record after rootOverride:
+//       1 byte hasLoopOverride (0/1); iff set: 1 byte loop.hasLoop, 8-byte LE loop.start,
+//         8-byte LE loop.end (both two's-complement int64);
+//       1 byte hasStartPoint (0/1); iff set: 8-byte LE startPoint (two's-complement int64).
+//     The reader detects the marker to know the record shape — a v1 payload (no marker) reads
+//     the shorter record; a v2 payload reads the extended one. Both compose under ANY envelope.
+//   * PAYLOAD v3 (S15/S16, LEGACY — exists in Daniel's beta projects): the same marker + payload
+//     version (== 3), THEN the v2 body PLUS, appended to each zone record after the S11 startPoint
+//     tail (the S15/S16 per-zone play params — always present, NOT flag-gated):
+//       1 byte playMode (0 = Gate, 1 = Trigger);
+//       8-byte LE adsr.holdFrames (int64) — the S15 AHDSR hold stage, FRAMES at 44.1k nominal;
+//       8-byte LE trigger.lengthFraction as an IEEE-754 double (bit-cast to u64 LE);
+//       8-byte LE trigger.fadeInFrames (int64); 8-byte LE trigger.fadeOutFrames (int64);
+//       1 byte pitchEngine (0 = Varispeed, 1 = Preserve);
+//       1 byte pitchEnv.enabled (0/1); 8-byte LE pitchEnv.attackFrames (int64, FRAMES 44.1k nom);
+//         8-byte LE pitchEnv.decayFrames (int64, FRAMES 44.1k nom); 8-byte LE peakSemitones double.
+//     A v1/v2 payload (no v3 tail) lifts each zone to the PRODUCT defaults (Gate + Preserve +
+//     no fades + disabled pitch env) — the deliberate S16-F1 behavior change for already-saved
+//     instruments. A truncated mid-v3-tail record keeps the zones that parsed and drops the rest.
+//     LEGACY-READ CONVERSION (S12): the v3 wall-clock frame counts (hold, pitchEnv A/D) were ALWAYS
+//     written by the S15/S16 editor as nominal frames at a baked-in rate. They convert to the seconds
+//     domain by dividing by the PROJECT sample rate threaded into the v3 lift path at read time (passed
+//     as a parameter — no constant). Source-timeline fields (trigger %-length + fades) stay frames.
+//     A/D/S/R are absent in v3 -> lifted to the tier-0 seconds defaults (0.003 / 0 / 1.0 / 0.060).
+//   * PAYLOAD v5 (S12 remediation — CURRENT WRITE FORMAT): the same marker + payload version (== 5),
+//     THEN the v2 body PLUS, appended to each zone record after the S11 startPoint tail, the full
+//     per-zone play params with WALL-CLOCK TIMES STORED AS SECONDS (rate-free, IEEE-754 doubles):
+//       1 byte playMode (0 = Gate, 1 = Trigger);
+//       8-byte LE adsr.holdSeconds (double); 8-byte LE trigger.lengthFraction (double);
+//       8-byte LE trigger.fadeInFrames (int64); 8-byte LE trigger.fadeOutFrames (int64);
+//       1 byte pitchEngine; 1 byte pitchEnv.enabled;
+//       8-byte LE pitchEnv.attackSeconds (double); 8-byte LE pitchEnv.decaySeconds (double);
+//       8-byte LE pitchEnv.peakSemitones (double);
+//       8-byte LE adsr.attackSeconds (double); 8-byte LE adsr.decaySeconds (double);
+//       8-byte LE adsr.sustainLevel (double); 8-byte LE adsr.releaseSeconds (double).
+//     Trigger fades stay int64 SOURCE frames (a source-timeline fact, PLAN.md §S15). PAYLOAD v4
+//     (the branch-only frames-tail) was NEVER shipped and is intentionally dropped from the reader
+//     — a v4 blob cannot exist outside this branch. The keymap builders resolve the stored seconds
+//     to frames at the LIVE sample rate; no rate is baked into storage or the program.
+// BACK-COMPAT: a v1 ENVELOPE blob (the S4 single-selection format: version tag 1 + id bytes) is
+// lifted to a single full-keyboard zone playing that id (no override) — so an instance saved
+// under Tier 0 restores as a one-zone Tier-1 map. A truncated/unknown/empty blob deserializes
+// to an EMPTY map.
+//
+// These two functions serialize the ZONES only. Since S10 the instrument's full component
+// state is {single-capture selection id, zones} — see ComponentState / serializeComponentState
+// below, the v3 format the processor actually reads/writes. serializePerformance/
+// deserializePerformance are retained for the zones payload + the v1/v2 back-compat lift.
+
+inline constexpr std::uint32_t kPerformanceStateVersion = 2;
+
+// The zones-payload format version and its detection marker (S11/S15/S16/S12). serializePerformance
+// and serializeComponentState both emit the CURRENT payload version (v5 — marker + version +
+// records with the S11 loop/start tail AND the full play-params tail with wall-clock times in
+// SECONDS) so the overrides round-trip through EITHER envelope. Readers accept a v1 payload (no
+// marker), a v2 payload (marker + version 2, no play tail), and a v3 payload (legacy S15/S16
+// play tail with wall-clock frame counts) for back-compat, lifting missing fields to defaults.
+// v4 was never shipped and is not read. The marker is a high sentinel that a legitimate zone
+// count (bounded by 128 MIDI zones in practice, always tiny) can never collide with.
+inline constexpr std::uint32_t kZonesPayloadVersion = 5;  // S12: full per-zone play params, SECONDS
+inline constexpr std::uint32_t kZonesFormatMarker = 0xFFFFFF00u;
+
+// (No kLegacyV3NominalRate constant.) The legacy v3 zone payload's wall-clock frame counts are
+// converted to seconds at the v3 read boundary using the PROJECT sample rate threaded in as a
+// parameter — frames ÷ projectRate = seconds. The project rate is the same rate keymap build
+// already receives, so the seconds domain is consistent across both paths. No constant is baked in.
+
+// The performance map serialized to bytes for IBStream (getState).
+std::vector<std::uint8_t> serializePerformance(const PerformanceMap& map);
+
+// The performance map parsed back from IBStream bytes (setState). A v2 blob parses
+// directly; a v1 blob lifts to a single full-keyboard zone; anything else -> empty map.
+// `projectRate` is the live host/project sample rate (must be > 0) used to convert the
+// legacy v3 wall-clock frame counts to the seconds domain at the read boundary.
+PerformanceMap deserializePerformance(const std::vector<std::uint8_t>& bytes,
+                                      double projectRate);
+
+// --- Combined component state (VST3 setState/getState, v3 — S10) -------------
+//
+// Since S10 the single-capture SELECTION and the opt-in ZONES are distinct concepts that
+// BOTH persist: the default face is one picked capture (the selection id), and zones are a
+// demoted opt-in overlay (the performance map). The component state carries both so a saved
+// project restores an instance's pick AND its zones — and, per the S10 policy reversal, an
+// instance with NO pick and NO zones restores EMPTY (silence + the "pick a capture" empty
+// state), never auto-playing sample #1.
+//
+// Format (envelope v5): 4-byte LE version tag (== 5), then a 1-byte channel-mode field (0 = mono,
+// 1 = stereo), then an 8-byte LE last-consumed-assignment generation (S8/S9 reader marker),
+// then a 4-byte LE selection-id length + id bytes, then the CURRENT zones payload (identical to
+// serializePerformance's body — its own self-describing version, see the ZONES-PAYLOAD block).
+// The 8-byte marker is the ONLY envelope-v5 addition over envelope-v4 — the envelope grew a field,
+// the zones payload is untouched (a PARALLEL track owns zone-record extension under its own
+// versioning; the two version numbers are independent axes). BACK-COMPAT on
+// read (every older blob lifts to channelMode = MONO and lastConsumedAssignGeneration = 0,
+// preserving current behavior for already-saved instances):
+//   * v5 blob        -> {channelMode, lastConsumedAssignGeneration, selectionId, zones} direct.
+//   * v4 blob        -> {channelMode, 0, selectionId, zones}: pre-S8/S9 reader (no marker).
+//   * v3 blob        -> {mono, 0, selectionId, zones}: pre-S7 had no channel mode.
+//   * v2 blob        -> {mono, 0, "", zones}: an S5 instance had zones but no separate selection.
+//   * v1 blob        -> {mono, 0, id, one full-keyboard zone}: the S4 single-selection lift.
+//   * empty/unknown  -> {mono, 0, "", no zones}: EMPTY (the S10 silent empty state).
+//
+// WHY THE MARKER PERSISTS (S8 reader requirement). The last-consumed assignment generation is
+// the disambiguator that stops a re-opened instance re-applying a stale assign_request the user
+// already got and then manually changed away from: on re-open the instance re-reads the pending
+// request, and only a generation STRICTLY GREATER than this stored marker re-applies (see
+// bank_sync::consumeDecision). A fresh instance defaults to 0, so a genuinely new first assign
+// (generation >= 1) still applies. It is the instrument's OWN state (D-B), never written to the
+// bank — the extension owns the assign_request key; the instrument only tracks what it consumed.
+struct ComponentState {
+    std::string selectionId;                     // the single-capture pick; "" = no pick
+    PerformanceMap map;                          // the opt-in zones; empty = no zones
+    ChannelMode channelMode = ChannelMode::Mono; // S7 output mode; default mono (D-E)
+    std::int64_t lastConsumedAssignGeneration = 0;  // S8/S9: last assign_request generation consumed
+};
+
+inline constexpr std::uint32_t kComponentStateVersion = 5;
+
+// The pre-S8/S9-reader combined-state version (selection + zones + channel mode, no consumed
+// marker). Retained so deserializeComponentState can lift a v4 blob to {mode, 0, sel, zones}.
+inline constexpr std::uint32_t kSelectionZonesModeV4Version = 4;
+
+// The pre-S7 combined-state version (selection + zones, no channel mode). Retained as a named
+// constant so deserializeComponentState can lift a v3 blob to {mono, selection, zones}.
+inline constexpr std::uint32_t kSelectionZonesV3Version = 3;
+
+// The full instance state serialized to bytes for IBStream (getState).
+std::vector<std::uint8_t> serializeComponentState(const ComponentState& state);
+
+// The full instance state parsed back from IBStream bytes (setState). Tolerant of
+// truncation/wrong-version (bounded reads, never throws); older blobs lift per the table
+// above so already-saved instances restore cleanly.
+// `projectRate` is the live host/project sample rate (must be > 0) used to convert the
+// legacy v3 wall-clock frame counts to the seconds domain at the read boundary.
+ComponentState deserializeComponentState(const std::vector<std::uint8_t>& bytes,
+                                         double projectRate);
+
+// --- Instance state (VST3 setState/getState) --------------------------------
+//
+// The instrument's OWN state is which bank sample it plays (D-B: the selection is a
+// performance choice, held by the instrument, never written back to the bank). It is a
+// single string id. serialize/deserialize keep the on-the-wire form explicit and
+// versioned so a future Tier can extend it without breaking already-saved instances.
+//
+// Format (v1): a 4-byte little-endian version tag (== 1) followed by the id bytes. No
+// length prefix is needed — the id runs to the end of the stream (the host tells us the
+// byte count). deserializeSelection tolerates a truncated / wrong-version / empty blob
+// by returning "" (no selection — under the S10 policy reversal an empty selection is
+// SILENCE + the "pick a capture" empty state, not the bank's first sample), never
+// throwing across the host boundary. Retained for the v1→v3 back-compat lift in
+// deserializeComponentState; the processor's live state is the v3 ComponentState above.
+
+inline constexpr std::uint32_t kSelectionStateVersion = 1;
+
+// The selected-sample id serialized to bytes for IBStream (getState).
+std::vector<std::uint8_t> serializeSelection(const std::string& sampleId);
+
+// The selected-sample id parsed back from IBStream bytes (setState). Unknown version,
+// too-short, or empty -> "" (graceful no-selection).
+std::string deserializeSelection(const std::vector<std::uint8_t>& bytes);
+
+}  // namespace reasampler

src/vst/sampler_core.cpp

@@ -0,0 +1,633 @@
+// sampler_core — pure sampler engine implementation. See sampler_core.h for the
+// contract and the design rationale (keymap resolution, pitch ratio, ADSR shape,
+// voice allocation + stealing policy). NO VST3 / REAPER / SWELL / vendor includes.
+
+#include "sampler_core.h"
+
+#include <cmath>
+
+namespace reasampler {
+
+// ---------------------------------------------------------------------------
+// pitchRatio
+// ---------------------------------------------------------------------------
+
+double pitchRatio(int note, int rootNote) {
+    // Equal temperament: each semitone is a factor of 2^(1/12). note == root -> 1.0.
+    return std::pow(2.0, static_cast<double>(note - rootNote) / 12.0);
+}
+
+// ---------------------------------------------------------------------------
+// Keymap
+// ---------------------------------------------------------------------------
+
+ZoneResolution Keymap::resolve(int note, int velocity) const {
+    (void)velocity;  // accepted for the Tier-2 seam; does not select at Tier 0-1.
+    for (std::size_t i = 0; i < zones.size(); ++i) {
+        const KeyZone& z = zones[i];
+        if (note >= z.lowNote && note <= z.highNote) {
+            return ZoneResolution{true, i};
+        }
+    }
+    return ZoneResolution{false, 0};
+}
+
+Keymap Keymap::singleSampleChromatic(SampleData sample) {
+    const int root = sample.rootNote;
+    Keymap km;
+    km.samples.push_back(std::move(sample));
+    KeyZone zone;
+    zone.lowNote = 0;
+    zone.highNote = 127;
+    zone.rootNote = root;
+    zone.sampleIndex = 0;
+    km.zones.push_back(zone);
+    return km;
+}
+
+// ---------------------------------------------------------------------------
+// AdsrEnvelope
+// ---------------------------------------------------------------------------
+
+void AdsrEnvelope::noteOn() {
+    stage_ = Stage::Attack;
+    level_ = 0.0;
+    framesInStage_ = 0;
+}
+
+void AdsrEnvelope::noteOff() {
+    if (stage_ == Stage::Idle || stage_ == Stage::Finished ||
+        stage_ == Stage::Release) {
+        return;  // already released / not sounding.
+    }
+    // Release from the CURRENT level — release-before-sustain releases from the
+    // partial attack/decay level, not from sustainLevel.
+    releaseFrom_ = level_;
+    stage_ = Stage::Release;
+    framesInStage_ = 0;
+}
+
+double AdsrEnvelope::tick() {
+    switch (stage_) {
+        case Stage::Idle:
+        case Stage::Finished:
+            level_ = 0.0;
+            return 0.0;
+
+        case Stage::Attack: {
+            if (params_.attackFrames <= 0) {
+                level_ = 1.0;
+            } else {
+                level_ = static_cast<double>(framesInStage_) /
+                         static_cast<double>(params_.attackFrames);
+                if (level_ > 1.0) level_ = 1.0;
+            }
+            const double out = level_;
+            ++framesInStage_;
+            if (framesInStage_ >= params_.attackFrames) {
+                // S15: Attack -> Hold (holds 1.0 for holdFrames). holdFrames == 0 falls straight
+                // through Hold on the next tick to Decay, which is EXACTLY the pre-S15 A->D path.
+                stage_ = Stage::Hold;
+                framesInStage_ = 0;
+                level_ = 1.0;
+            }
+            return out;
+        }
+
+        case Stage::Hold: {
+            // S15 hold stage: level pinned at 1.0 for holdFrames. holdFrames <= 0 leaves the
+            // stage on this same tick (no frame consumed at 1.0 beyond what Attack already
+            // emitted), so hold=0 is byte-identical to the pre-S15 envelope.
+            if (params_.holdFrames <= 0) {
+                stage_ = Stage::Decay;
+                framesInStage_ = 0;
+                // Fall through to Decay this frame so no extra unity sample is emitted for a
+                // zero-length hold (preserving the exact pre-S15 sample-for-sample shape).
+                level_ = 1.0;
+                // Single re-dispatch into Decay (bounded: Hold→Decay only; not a general recursion).
+                return tick();
+            }
+            level_ = 1.0;
+            const double out = level_;
+            ++framesInStage_;
+            if (framesInStage_ >= params_.holdFrames) {
+                stage_ = Stage::Decay;
+                framesInStage_ = 0;
+                level_ = 1.0;
+            }
+            return out;
+        }
+
+        case Stage::Decay: {
+            if (params_.decayFrames <= 0) {
+                level_ = params_.sustainLevel;
+            } else {
+                const double t = static_cast<double>(framesInStage_) /
+                                 static_cast<double>(params_.decayFrames);
+                level_ = 1.0 + (params_.sustainLevel - 1.0) * t;
+            }
+            const double out = level_;
+            ++framesInStage_;
+            if (framesInStage_ >= params_.decayFrames) {
+                stage_ = Stage::Sustain;
+                framesInStage_ = 0;
+                level_ = params_.sustainLevel;
+            }
+            return out;
+        }
+
+        case Stage::Sustain:
+            level_ = params_.sustainLevel;
+            return level_;
+
+        case Stage::Release: {
+            if (params_.releaseFrames <= 0) {
+                level_ = 0.0;
+                stage_ = Stage::Finished;
+                return 0.0;
+            }
+            const double t = static_cast<double>(framesInStage_) /
+                             static_cast<double>(params_.releaseFrames);
+            level_ = releaseFrom_ * (1.0 - t);
+            if (level_ < 0.0) level_ = 0.0;
+            const double out = level_;
+            ++framesInStage_;
+            if (framesInStage_ >= params_.releaseFrames) {
+                stage_ = Stage::Finished;
+                level_ = 0.0;
+            }
+            return out;
+        }
+    }
+    return 0.0;  // unreachable; silences a warning.
+}
+
+// ---------------------------------------------------------------------------
+// TriggerEnvelope (S15) — a time-boxed fade-in/hold/fade-out amplitude function.
+// ---------------------------------------------------------------------------
+
+void TriggerEnvelope::configure(std::int64_t playLengthFrames, std::int64_t fadeInFrames,
+                                std::int64_t fadeOutFrames, FadeCurve curve) {
+    playLength_ = playLengthFrames > 0 ? playLengthFrames : 0;
+    curve_ = curve;
+    finished_ = (playLength_ <= 0);
+
+    // Clamp the fades so fadeIn + fadeOut <= playLength (fade-out anchored to the end). A
+    // negative fade is treated as 0. When both fades together exceed the play length, shrink
+    // the fade-out first (the head fade-in is the more perceptually load-bearing onset ramp),
+    // then the fade-in — never letting either go negative or the sum exceed the span.
+    std::int64_t fi = fadeInFrames > 0 ? fadeInFrames : 0;
+    std::int64_t fo = fadeOutFrames > 0 ? fadeOutFrames : 0;
+    if (fi > playLength_) fi = playLength_;
+    if (fi + fo > playLength_) fo = playLength_ - fi;  // fo >= 0 since fi <= playLength_
+    fadeIn_ = fi;
+    fadeOut_ = fo;
+}
+
+double TriggerEnvelope::amplitudeAt(double sourceOffset) {
+    if (finished_ || sourceOffset < 0.0 ||
+        sourceOffset >= static_cast<double>(playLength_)) {
+        // At/past the play length the one-shot is done; the voice also frees on readPos >= playEnd.
+        if (sourceOffset >= static_cast<double>(playLength_)) finished_ = true;
+        return 0.0;
+    }
+
+    // Fade-in: 0->1 over [0, fadeIn_). Fade-out: 1->0 over [playLength_-fadeOut_, playLength_).
+    // Unity between. The two ramps never overlap (configure clamps fadeIn_ + fadeOut_ <= length).
+    // The offset is fractional (the read head is fractional under repitch), so the ramps are
+    // smooth rather than stepped.
+    double amp = 1.0;
+    const double foStart = static_cast<double>(playLength_ - fadeOut_);
+    if (fadeIn_ > 0 && sourceOffset < static_cast<double>(fadeIn_)) {
+        const double phase = sourceOffset / static_cast<double>(fadeIn_);  // 0..1
+        amp = (curve_ == FadeCurve::EqualPower)
+                  ? std::sin(phase * 1.5707963267948966)  // sin(phase*pi/2): 0->1 constant power
+                  : phase;
+    } else if (fadeOut_ > 0 && sourceOffset >= foStart) {
+        const double phase = (sourceOffset - foStart) / static_cast<double>(fadeOut_);  // 0..1
+        amp = (curve_ == FadeCurve::EqualPower)
+                  ? std::cos(phase * 1.5707963267948966)  // cos(phase*pi/2): 1->0 constant power
+                  : (1.0 - phase);
+    }
+    return amp;
+}
+
+// ---------------------------------------------------------------------------
+// PitchEnvelope (S16) — AD pitch offset in semitones, off when disabled.
+// ---------------------------------------------------------------------------
+
+double PitchEnvelope::tick() {
+    if (!params_.enabled) return 0.0;
+
+    const std::int64_t a = params_.attackFrames > 0 ? params_.attackFrames : 0;
+    const std::int64_t d = params_.decayFrames > 0 ? params_.decayFrames : 0;
+    const double peak = params_.peakSemitones;
+
+    double offset;
+    if (pos_ < a) {
+        // Attack: 0 -> peak over attackFrames (rise into the peak).
+        offset = peak * (static_cast<double>(pos_) / static_cast<double>(a));
+    } else if (pos_ < a + d) {
+        // Decay: peak -> 0 over decayFrames (settle to base pitch).
+        const double t = static_cast<double>(pos_ - a) / static_cast<double>(d);
+        offset = peak * (1.0 - t);
+    } else {
+        offset = 0.0;  // past attack+decay: at base pitch forever.
+    }
+    ++pos_;
+    return offset;
+}
+
+// ---------------------------------------------------------------------------
+// Voice
+// ---------------------------------------------------------------------------
+
+void Voice::presizePreserveShifters(std::int64_t windowFrames) {
+    // OFF the audio thread (allocates). Both channels are sized so a stereo Preserve voice needs
+    // no allocation at note-on; a mono Preserve voice simply never process()es shiftR_.
+    shiftL_.configure(windowFrames);
+    shiftR_.configure(windowFrames);
+}
+
+void Voice::start(int note, int velocity, const SampleData& sample, int rootNote) {
+    active_ = true;
+    releasing_ = false;
+    amplitudeDone_ = false;
+    note_ = note;
+    // MIDI velocity 1..127 -> linear gain 0..1. Clamp defensively.
+    int v = velocity;
+    if (v < 0) v = 0;
+    if (v > 127) v = 127;
+    velocityGain_ = static_cast<double>(v) / 127.0;
+    baseRatio_ = pitchRatio(note, rootNote);
+    sample_ = &sample;
+
+    const ZonePlayParams& p = sample.play;
+    playMode_ = p.playMode;
+    pitchEngine_ = p.pitchEngine;
+
+    // Initial read position honors the sample's start-point offset (S11), in BOTH modes. Clamp
+    // into [0, frames): a start at or past the end degrades to 0 (play from the top) rather than
+    // starting a voice already off the end. A negative start (shouldn't occur) is pinned to 0.
+    const std::int64_t frameCount = static_cast<std::int64_t>(sample.frames.size());
+    std::int64_t start = sample.startFrame;
+    if (start < 0 || start >= frameCount) start = 0;
+    readPos_ = static_cast<double>(start);
+    startFrame_ = start;  // Trigger fade offset origin (readPos - startFrame = span offset)
+
+    // --- Amplitude envelope: Gate = AHDSR (fully per-zone: A/H/D/S/R all read from the zone's
+    //     play.adsr); Trigger = the time-boxed fade-in/out over the % play length.
+    //
+    //     All five AHDSR fields come from sample.play.adsr (in FRAMES), resolved by
+    //     buildTier0Keymap / buildZonedKeymap at reload time from the stored SECONDS against
+    //     the live sample rate.
+    //
+    //     Back-compat invariant: a zone whose stored ADSR seconds carry the tier-0 defaults
+    //     (resolved to frames at the live sample rate) sounds identical to the pre-S12 build at
+    //     every DAW rate — now trivially true, since the times are wall-clock seconds. ---
+    if (playMode_ == PlayMode::Gate) {
+        env_.configure(p.adsr);
+        env_.noteOn();
+        playEnd_ = 0;  // unused in Gate
+    } else {
+        // Trigger: play [start, playEnd) where playEnd = start + round(lengthFraction*(frames-start)).
+        double frac = p.trigger.lengthFraction;
+        if (frac <= 0.0) frac = 0.0;      // %=0 -> zero play length (finishes immediately)
+        if (frac > 1.0) frac = 1.0;
+        const std::int64_t span = frameCount - start;  // >= 1 (start clamped < frameCount)
+        std::int64_t playLen = static_cast<std::int64_t>(
+            static_cast<double>(span) * frac + 0.5);  // round
+        if (playLen < 0) playLen = 0;
+        if (playLen > span) playLen = span;
+        playEnd_ = start + playLen;
+        trigEnv_.configure(playLen, p.trigger.fadeInFrames, p.trigger.fadeOutFrames,
+                           kDefaultFadeCurve);
+    }
+
+    // --- Pitch envelope (S16): per-voice AD, off by default (offset always 0). ---
+    pitchEnv_.configure(p.pitchEnv);
+    pitchEnv_.noteOn();
+
+    // --- Preserve engine (S16): reset + pre-warm the ALREADY-SIZED per-channel shifters. The
+    //      rings were allocated off-thread by presizePreserveShifters (the engine calls it at
+    //     construction), so this RT-safe path only zeroes state (reset) and runs a silence pass
+    //     (warm) to settle the OLA taps before the first output frame — NO allocation here.
+    //     Varispeed voices never touch the shifters (advanceFrame checks configured()), so a
+    //     Varispeed instrument is byte-identical to pre-S16 and pays no per-frame shifter cost. ---
+    if (pitchEngine_ == PitchEngine::Preserve && shiftL_.configured()) {
+        shiftL_.reset();
+        shiftL_.warm();
+        if (sample.channelCount() == 2 && shiftR_.configured()) {
+            shiftR_.reset();
+            shiftR_.warm();
+        }
+    }
+    ratio_ = baseRatio_;  // seeded; advanceFrame recomputes per frame under the active engine.
+}
+
+void Voice::release() {
+    if (!active_) return;
+    // TRIGGER ignores note-off entirely (S15): the one-shot plays through to its play length.
+    if (playMode_ == PlayMode::Trigger) return;
+    releasing_ = true;
+    env_.noteOff();
+}
+
+double Voice::tickAmplitude() {
+    double amp;
+    if (playMode_ == PlayMode::Gate) {
+        // AHDSR is wall-clock (one tick per output frame), independent of the read rate.
+        amp = env_.tick();
+        if (env_.finished()) amplitudeDone_ = true;
+    } else {
+        // Trigger fade shape anchored to the SOURCE offset (readPos - startFrame), so the fades
+        // land on the same source frames under either engine's read rate. The voice ALSO frees on
+        // readPos_ >= playEnd_ in advanceFrame; finished() here is the belt to that suspenders.
+        amp = trigEnv_.amplitudeAt(readPos_ - static_cast<double>(startFrame_));
+        if (trigEnv_.finished()) amplitudeDone_ = true;
+    }
+    return amp;
+}
+
+AudioSample Voice::advanceFrame(bool stereo, AudioSample& outR) {
+    // Shared read/advance for the mono and stereo paths. The read-head geometry (loop wrap,
+    // bracketing indices, interpolation partner) is computed ONCE and applied identically to
+    // every channel — only the PCM value read differs. The amplitude + pitch envelopes tick ONCE
+    // per frame and scale all channels equally (a voice is one envelope). The head advances by
+    // exactly one source-frame step per call, so mono and stereo consume the sample at one rate.
+    if (!active_ || sample_ == nullptr) {
+        if (stereo) outR = 0.0f;
+        return 0.0f;
+    }
+
+    const std::vector<AudioSample>& pcm = sample_->frames;
+    const std::int64_t frameCount = static_cast<std::int64_t>(pcm.size());
+    // Read the second channel only for a genuinely stereo sample; a mono sample plays
+    // dual-mono (channel 0 duplicated), so `pcmR` aliases channel 0 in that case.
+    const bool haveR = stereo && sample_->channelCount() == 2;
+    const std::vector<AudioSample>& pcmR = haveR ? sample_->framesR : pcm;
+
+    // Loop-aware sustain (GATE only — Trigger is a one-shot with no sustain loop, S15). If a
+    // valid, non-zero-length loop exists and the read head has advanced past the loop end, wrap
+    // it back into [start, end). A zero-length loop is treated as "no loop". Under Preserve the
+    // loop is over the SOURCE read (loop the source, shift the output — S15×S16 contract).
+    const SampleLoop& loop = sample_->loop;
+    const bool loopUsable = playMode_ == PlayMode::Gate && loop.hasLoop &&
+                            loop.end > loop.start && loop.start >= 0 && loop.end <= frameCount;
+    if (loopUsable) {
+        const double loopLen = static_cast<double>(loop.end - loop.start);
+        while (readPos_ >= static_cast<double>(loop.end)) {
+            readPos_ -= loopLen;  // wrap by exactly one loop length, preserving phase.
+        }
+    }
+
+    // TRIGGER end: the voice frees once the read head reaches playEnd (source-frame stop). The
+    // trigger envelope also finishes at the same frame count; either latches the voice idle.
+    const bool triggerRanOff =
+        playMode_ == PlayMode::Trigger && readPos_ >= static_cast<double>(playEnd_);
+    // Ran off the sample end with no usable loop -> voice is done.
+    if (triggerRanOff || readPos_ >= static_cast<double>(frameCount)) {
+        active_ = false;
+        if (stereo) outR = 0.0f;
+        return 0.0f;
+    }
+
+    // Linear interpolation between the two bracketing SOURCE frames. For the loop case, the
+    // second point wraps to loopStart so the seam is continuous.
+    const std::int64_t i0 = static_cast<std::int64_t>(readPos_);
+    const double frac = readPos_ - static_cast<double>(i0);
+    std::int64_t i1 = i0 + 1;
+    if (loopUsable && i1 >= loop.end) {
+        i1 = loop.start;  // seamless wrap for the interpolation partner.
+    }
+    const bool i0ok = (i0 >= 0 && i0 < frameCount);
+    const bool i1ok = (i1 >= 0 && i1 < frameCount);
+
+    // Envelopes tick once per output frame. Pitch envelope biases pitch under EITHER engine.
+    const double amp = tickAmplitude();
+    const double gain = amp * velocityGain_;
+    const double pitchEnvSemis = pitchEnv_.tick();
+
+    // Raw interpolated source values (pre-shift). These are the SOURCE stream both engines read;
+    // Varispeed applies pitch by the read RATE, Preserve applies it by the shifter.
+    const double srcL = (i0ok ? static_cast<double>(pcm[i0]) : 0.0) +
+                        ((i1ok ? static_cast<double>(pcm[i1]) : 0.0) -
+                         (i0ok ? static_cast<double>(pcm[i0]) : 0.0)) * frac;
+    double srcR = 0.0;
+    if (stereo) {
+        srcR = (i0ok ? static_cast<double>(pcmR[i0]) : 0.0) +
+               ((i1ok ? static_cast<double>(pcmR[i1]) : 0.0) -
+                (i0ok ? static_cast<double>(pcmR[i0]) : 0.0)) * frac;
+    }
+
+    // The pitch-envelope bias factor 2^(semis/12). When the envelope is off (semis exactly 0)
+    // this is 1.0 and we skip the pow entirely — the Varispeed-off path stays a bare ratio read
+    // (no per-frame transcendental), byte-identical to pre-S16.
+    const double envFactor = (pitchEnvSemis == 0.0) ? 1.0 : std::pow(2.0, pitchEnvSemis / 12.0);
+
+    double outL, outRlocal = 0.0;
+    if (pitchEngine_ == PitchEngine::Preserve && shiftL_.configured()) {
+        // PRESERVE: read the source at unity rate (duration held) and TRANSPOSE the output by
+        // 2^((note-root + pitchEnvSemis)/12). Pitch envelope adds to the shift amount, not the
+        // read rate — pitch bends, duration unchanged (S16 contract).
+        const double shift = baseRatio_ * envFactor;
+        shiftL_.setShiftRatio(shift);
+        const double shiftedL = static_cast<double>(shiftL_.process(static_cast<AudioSample>(srcL)));
+        outL = shiftedL * gain;
+        if (stereo) {
+            if (shiftR_.configured()) {
+                // Genuine stereo: an independent shifter transposes channel 1. Each shifter is
+                // process()'d EXACTLY ONCE per output frame (never twice — that would advance its
+                // heads twice and corrupt the OLA state).
+                shiftR_.setShiftRatio(shift);
+                outRlocal =
+                    static_cast<double>(shiftR_.process(static_cast<AudioSample>(srcR))) * gain;
+            } else {
+                // Mono sample in stereo mode (dual-mono): shiftL_ already produced the shifted
+                // value from srcL (== srcR since pcmR aliases pcm); mirror it to R. Do NOT call
+                // shiftL_.process again this frame.
+                outRlocal = shiftedL * gain;
+            }
+        }
+        // Preserve advances the read head at the SOURCE rate (duration preserved).
+        ratio_ = 1.0;
+    } else {
+        // VARISPEED: pitch and duration coupled. The read rate carries the repitch; the pitch
+        // envelope multiplies the ratio for the read-rate bias (unchanged pre-S16 idiom when the
+        // envelope is off -> pitchEnvSemis == 0 -> factor 1.0 -> byte-identical).
+        outL = srcL * gain;
+        if (stereo) outRlocal = srcR * gain;
+        ratio_ = baseRatio_ * envFactor;
+    }
+
+    if (stereo) outR = static_cast<AudioSample>(outRlocal);
+
+    readPos_ += ratio_;
+
+    if (amplitudeDone_) {
+        active_ = false;
+    }
+    return static_cast<AudioSample>(outL);
+}
+
+AudioSample Voice::renderFrame() {
+    AudioSample discard = 0.0f;
+    return advanceFrame(/*stereo=*/false, discard);
+}
+
+void Voice::renderFrameStereo(AudioSample& l, AudioSample& r) {
+    r = 0.0f;
+    l = advanceFrame(/*stereo=*/true, r);
+}
+
+// ---------------------------------------------------------------------------
+// VoiceEngine
+// ---------------------------------------------------------------------------
+
+VoiceEngine::VoiceEngine(std::size_t maxVoices, const Keymap& keymap,
+                         std::size_t preserveVoiceCap,
+                         std::int64_t preserveWindowFrames)
+    : voices_(maxVoices == 0 ? 1 : maxVoices), keymap_(keymap),
+      preserveVoiceCap_(preserveVoiceCap) {
+    // maxVoices == 0 would mean "no polyphony at all", which cannot service a note-on;
+    // clamp to a single voice so the engine is always usable (documented degenerate).
+    //
+    // Pre-size every voice's Preserve shifters HERE (construction is off the audio thread), so
+    // note-on never allocates. A 0 window leaves them pass-through (no ring). This is the one
+    // allocation point for the shifter rings across the engine's lifetime.
+    if (preserveWindowFrames > 1) {
+        for (Voice& v : voices_) v.presizePreserveShifters(preserveWindowFrames);
+    }
+}
+
+std::size_t VoiceEngine::activePreserveVoices() const {
+    std::size_t n = 0;
+    for (const Voice& v : voices_) {
+        if (v.active() && v.pitchEngine() == PitchEngine::Preserve) ++n;
+    }
+    return n;
+}
+
+std::size_t VoiceEngine::allocateVoice() {
+    // 1. A free (idle) voice, lowest index for determinism.
+    for (std::size_t i = 0; i < voices_.size(); ++i) {
+        if (!voices_[i].active()) return i;
+    }
+    // 2. All busy -> steal. Prefer the oldest voice already in release (a dying tail),
+    //    else the oldest voice overall. "Oldest" = smallest startOrder.
+    std::size_t bestReleasing = kNoVoice;
+    std::uint64_t bestReleasingOrder = 0;
+    std::size_t bestOverall = kNoVoice;
+    std::uint64_t bestOverallOrder = 0;
+    for (std::size_t i = 0; i < voices_.size(); ++i) {
+        const std::uint64_t order = voices_[i].startOrder();
+        if (voices_[i].releasing()) {
+            if (bestReleasing == kNoVoice || order < bestReleasingOrder) {
+                bestReleasing = i;
+                bestReleasingOrder = order;
+            }
+        }
+        if (bestOverall == kNoVoice || order < bestOverallOrder) {
+            bestOverall = i;
+            bestOverallOrder = order;
+        }
+    }
+    return bestReleasing != kNoVoice ? bestReleasing : bestOverall;
+}
+
+std::size_t VoiceEngine::noteOn(int note, int velocity) {
+    const ZoneResolution res = keymap_.resolve(note, velocity);
+    if (!res.matched) return kNoVoice;  // out-of-zone: defined no-play.
+
+    const KeyZone& zone = keymap_.zones[res.zoneIndex];
+    if (zone.sampleIndex >= keymap_.samples.size()) {
+        return kNoVoice;  // zone points at a missing sample — refuse rather than UB.
+    }
+    const SampleData& sample = keymap_.samples[zone.sampleIndex];
+
+    // S16 Preserve voice cap: a Preserve note is materially heavier than Varispeed (a per-voice
+    // OLA shifter). When a cap is set and it is already reached, DROP a new Preserve note-on
+    // rather than glitch (a defined no-play, mirroring out-of-zone — no shifter is allocated).
+    // Varispeed notes are unaffected. A voice already sounding is never cut by this cap; only
+    // NEW Preserve onsets past the cap are refused (the spec's "cap kicks in rather than glitch").
+    if (preserveVoiceCap_ > 0 && sample.play.pitchEngine == PitchEngine::Preserve &&
+        activePreserveVoices() >= preserveVoiceCap_) {
+        return kNoVoice;
+    }
+
+    // The voice's Preserve shifters were pre-sized at engine construction (off-thread), so
+    // start() only reset()s + warm()s them — no allocation on this audio-thread path.
+    const std::size_t v = allocateVoice();
+    voices_[v].start(note, velocity, sample, zone.rootNote);
+    voices_[v].setStartOrder(nextStartOrder_++);
+    return v;
+}
+
+void VoiceEngine::noteOff(int note) {
+    // Release the NEWEST active, non-releasing voice on this note (largest startOrder),
+    // so a re-triggered note releases its newest instance first and older tails ring.
+    std::size_t target = kNoVoice;
+    std::uint64_t bestOrder = 0;
+    for (std::size_t i = 0; i < voices_.size(); ++i) {
+        if (voices_[i].active() && !voices_[i].releasing() &&
+            voices_[i].note() == note) {
+            const std::uint64_t order = voices_[i].startOrder();
+            if (target == kNoVoice || order > bestOrder) {
+                target = i;
+                bestOrder = order;
+            }
+        }
+    }
+    if (target != kNoVoice) voices_[target].release();
+}
+
+void VoiceEngine::render(AudioSample* out, std::size_t frameCount) {
+    // Real-time safe: no allocation, no resize — mix straight into the caller's buffer.
+    // The VST3 process callback hands us the host's output channel buffer here, so the
+    // audio thread never touches the heap (S4 real-time discipline).
+    if (out == nullptr || frameCount == 0) return;
+    for (Voice& voice : voices_) {
+        if (!voice.active()) continue;
+        for (std::size_t f = 0; f < frameCount; ++f) {
+            if (!voice.active()) break;
+            out[f] += voice.renderFrame();
+        }
+    }
+}
+
+void VoiceEngine::render(AudioSample* left, AudioSample* right, std::size_t frameCount) {
+    // Real-time safe stereo mix: no allocation, no resize. Sum each active voice's per-channel
+    // contribution into the caller's two buffers. Mirrors the mono loop exactly (same voice
+    // iteration, same mid-block idle short-circuit) so stereo and mono share one stealing/idle
+    // discipline; only the per-frame call differs (renderFrameStereo vs renderFrame).
+    if (left == nullptr || right == nullptr || frameCount == 0) return;
+    for (Voice& voice : voices_) {
+        if (!voice.active()) continue;
+        for (std::size_t f = 0; f < frameCount; ++f) {
+            if (!voice.active()) break;
+            AudioSample l = 0.0f, r = 0.0f;
+            voice.renderFrameStereo(l, r);
+            left[f] += l;
+            right[f] += r;
+        }
+    }
+}
+
+void VoiceEngine::render(std::vector<AudioSample>& out, std::size_t frameCount) {
+    // Off-thread / test path: grow the buffer (this allocates — never call under
+    // process), zero-fill the appended span, then delegate to the RT mix loop so both
+    // overloads share exactly one summation path.
+    const std::size_t base = out.size();
+    out.resize(base + frameCount, 0.0f);
+    render(out.data() + base, frameCount);
+}
+
+std::size_t VoiceEngine::activeVoiceCount() const {
+    std::size_t n = 0;
+    for (const Voice& v : voices_) {
+        if (v.active()) ++n;
+    }
+    return n;
+}
+
+} // namespace reasampler

src/vst/sampler_core.h

@@ -0,0 +1,531 @@
+#pragma once
+// sampler_core — the HEART of the Phase S MIDI-playback instrument (D3), deliberately
+// free of any VST3 *and* any REAPER type so it compiles and unit-tests OUTSIDE the DAW
+// and outside any plugin host. It owns the pure sampler engine: polyphonic voice
+// allocation with bounded stealing, an ADSR amplitude envelope, a key/velocity keymap
+// with (note, velocity) -> zone resolution, and repitch/interpolation from a root note
+// with loop-point-aware sustain.
+//
+// PURE MODULE (CLAUDE.md §load-bearing split): NO VST3 types, NO REAPER types, NO SWELL,
+// NO vendor/ includes, no include from either SDK. Standard library only. The VST3 shell
+// (src/vst/reasampler_processor.cpp) marshals MIDI events + audio buffers to and from
+// this core; the core never sees a VST3 ProcessData or a REAPER MediaTrack. Enforced
+// structurally: sampler_core_tests links neither SDK (see CMakeLists §2i).
+//
+// It shares the `AudioSample` float alias from peaks — the one house precedent for a
+// pure module leaning on peaks for the audio-domain type (wav_trim does the same). The
+// S2 seam fields (root note, loop points) enter as plain int / frame-index inputs; the
+// core does no file I/O — it is handed decoded sample frames and produces audio frames.
+
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+#include "peaks.h"        // AudioSample (float)
+#include "pitch_shift.h"  // PitchShifter (S16 Preserve engine DSP core)
+
+namespace reasampler {
+
+// The instrument's per-instance output channel mode (S7, D-E). MONO keeps the pre-S7
+// downmix path (one channel out); STEREO negotiates a 2-channel output bus and renders
+// per-channel. A PERFORMANCE choice the instrument owns (component state), never written
+// to the bank. Default Mono preserves current behavior. Lives in the pure core as a plain
+// value so the shell (bus negotiation, state) and the engine share one spelling; the core
+// itself never branches on it — the mode only picks which render overload the shell drives.
+enum class ChannelMode { Mono, Stereo };
+
+// ---------------------------------------------------------------------------
+// S15/S16 per-zone play PARAMETERS (plain data). Defined up here (before SampleData) because
+// SampleData carries a ZonePlayParams by value — a voice reads it at start(). The matching
+// per-frame EVALUATOR classes (AHDSR AdsrEnvelope, TriggerEnvelope, PitchEnvelope) live lower
+// with the rest of the engine machinery; only the value structs need to precede SampleData.
+// ---------------------------------------------------------------------------
+
+// AHDSR amplitude envelope parameters (S15 grows the S3 ADSR with a HOLD stage between Attack
+// and Decay). holdFrames == 0 is EXACTLY the pre-S15 ADSR (back-compat). See AdsrEnvelope below.
+struct AdsrParams {
+    std::int64_t attackFrames  = 0;
+    std::int64_t holdFrames    = 0;     // S15: hold at 1.0 between Attack and Decay; 0 = pre-S15 ADSR
+    std::int64_t decayFrames   = 0;
+    double       sustainLevel  = 1.0;   // 0..1
+    std::int64_t releaseFrames = 0;
+};
+
+// S15 play mode. GATE = classic held note (AHDSR + sustain loop + note-off release, today's
+// behavior grown by the hold stage). TRIGGER = one-shot: note-off-immune, no sustain loop,
+// plays a % of the sample length shaped by fade-in/out. Both honor the start point. Per-zone
+// (D-B); DEFAULT Gate so an instrument with no S15 params plays exactly as before.
+enum class PlayMode { Gate, Trigger };
+
+// Trigger amplitude envelope parameters (S15). Playback covers the source-frame span
+// [startFrame, playEnd), playEnd = startFrame + round(lengthFraction*(frames - startFrame)),
+// lengthFraction in (0,1]. Amplitude ramps 0->1 over fadeInFrames at the head and 1->0 over
+// fadeOutFrames anchored to playEnd; unity between. Fades clamp so fadeIn + fadeOut <= play
+// length. The voice frees when the head reaches playEnd. Note-off is a no-op in Trigger.
+struct TriggerParams {
+    double       lengthFraction = 1.0;  // (0,1] of the post-start span to play
+    std::int64_t fadeInFrames   = 0;    // 0->1 ramp at the head
+    std::int64_t fadeOutFrames  = 0;    // 1->0 ramp anchored to playEnd
+};
+
+// The fade curve for Trigger's ramps. EQUAL_POWER (constant-power sin/cos) is the default
+// (click-free on one-shots, per spec); LINEAR is the build-time residual. An enum (not a bool)
+// so a third curve can join without a signature change.
+enum class FadeCurve { EqualPower, Linear };
+
+// The DEFAULT fade curve (S15 spec: equal-power). One constant to flip if linear is wanted.
+inline constexpr FadeCurve kDefaultFadeCurve = FadeCurve::EqualPower;
+
+// The per-zone pitch engine. VARISPEED = today's path (readPos_ += ratio_): pitch and duration
+// coupled (an octave up plays half as long). PRESERVE = duration-preserving: the read advances
+// at the SOURCE rate while a PitchShifter transposes the output (an octave up keeps its length).
+enum class PitchEngine { Varispeed, Preserve };
+
+// The PRODUCT DEFAULT pitch engine (S16-F1 — Daniel's "I want duration-preserving repitching"
+// directive). ONE constant to flip if Varispeed should be the default instead. This is the
+// default a NEW or absent-in-the-blob zone gets — APPLIED AT THE STATE BOUNDARY (sample_map's
+// deserialize / editor zone-creation), NOT the pure-core struct default. The pure-core
+// ZonePlayParams.pitchEngine member defaults to VARISPEED so that "no params == the pre-S16
+// engine" holds for the core's own regression tests (an octave up still halves duration in the
+// bare engine); the Preserve product default is layered on above at (de)serialization.
+inline constexpr PitchEngine kDefaultPitchEngine = PitchEngine::Preserve;
+
+// The OLA window (frames) the Preserve PitchShifter uses, derived from a window in milliseconds
+// at the voice's sample rate. ~50 ms is the WDL quality-0 window the spec cites; larger =
+// smoother on big transpositions, more onset latency. One knob, resolved at voice allocation.
+inline constexpr double kPreserveWindowMs = 50.0;
+
+// A per-voice AD pitch-modulation envelope (S16), OFF by default (enabled=false -> offset always
+// 0 -> playback bit-identical to the un-modulated engine). At note-on the pitch offset rises to
+// peakSemitones over attackFrames, then falls to 0 (base pitch) over decayFrames. A zero attack
+// gives the pure "start high, drop to base" percussive drop. peakSemitones is signed (+/-).
+struct PitchEnvParams {
+    bool         enabled       = false;
+    std::int64_t attackFrames  = 0;
+    std::int64_t decayFrames   = 0;
+    double       peakSemitones = 0.0;  // signed depth at the peak
+};
+
+// The bundle of S15/S16 per-zone play parameters a voice reads at start(). Lives on SampleData
+// (each zone owns one SampleData in the zoned keymap). DEFAULTS are EXACTLY the pre-S15/S16
+// engine: Gate mode, AHDSR with hold 0 (= the S3 ADSR), VARISPEED pitch engine, pitch envelope
+// disabled — so a bare-core voice with default play is byte-identical to the pre-S15 build (the
+// core regression tests rely on this). The PRODUCT default of Preserve (S16-F1) is applied one
+// layer up at (de)serialization for new/absent zones — see kDefaultPitchEngine.
+struct ZonePlayParams {
+    PlayMode       playMode = PlayMode::Gate;
+    AdsrParams     adsr;                          // Gate: the AHDSR envelope
+    TriggerParams  trigger;                       // Trigger: %-length + fades
+    PitchEngine    pitchEngine = PitchEngine::Varispeed;
+    PitchEnvParams pitchEnv;                       // AD pitch modulation, off by default
+};
+
+// ---------------------------------------------------------------------------
+// Sample data the core plays. Plain, decoded PCM + the S2 bank intrinsics that
+// govern playback. The shell decodes the on-disk WAV and fills this; the core
+// never touches a file.
+// ---------------------------------------------------------------------------
+
+// A loop over [start, end) frames, half-open. A zero-length loop (start == end)
+// is the "no sustain loop" marker — a held note past the sample end goes silent
+// rather than looping a zero span. absent-loop is modeled by leaving hasLoop false.
+struct SampleLoop {
+    bool hasLoop = false;
+    std::int64_t start = 0;  // first looped frame (inclusive)
+    std::int64_t end   = 0;  // one-past-last looped frame (exclusive); start <= end
+};
+
+// One decoded audio sample the engine can voice. DEINTERLEAVED, per-channel: `frames` is
+// channel 0 (always present) and `framesR` is channel 1 (present only for a STEREO sample).
+// A sample is stereo iff `framesR` is non-empty AND the same length as `frames`; otherwise
+// it is mono (the degenerate, byte-identical Tier 0-1 case — `framesR` stays empty). Both
+// channels share `readPos_`, `rootNote`, and `loop`, so repitch/loop are per-frame identical
+// across channels; only the sampled value differs. `rootNote` is the MIDI note the file was
+// recorded at (S2 intrinsic) — the pitch that plays back at unity ratio.
+struct SampleData {
+    std::vector<AudioSample> frames;   // channel 0 PCM (mono, or L of a stereo sample)
+    std::vector<AudioSample> framesR;  // channel 1 PCM (R); EMPTY for a mono sample
+    int sampleRate = 0;                // frames per second (for reference; ratio is
+                                       // note-relative, so rate cancels for repitch).
+                                       // 0 is explicitly invalid — every consumer must
+                                       // receive a real rate before use.
+    int rootNote = 60;                 // MIDI note recorded at (plays at unity here)
+    SampleLoop loop;                   // sustain loop, if any
+    // Initial read position (frame offset) a voice starts playback at — frame 0 by
+    // default, so an unset start point is exactly the pre-S11 behavior. S11 makes this
+    // an instrument-side per-zone override (the "start point" marker); S15 builds on it
+    // (both play modes carry a modifiable start). Clamped into [0, frames) at note-on:
+    // a start >= the sample length is a no-op (voice starts at 0), never out of bounds.
+    std::int64_t startFrame = 0;
+
+    // S15/S16 per-zone play parameters (play mode, AHDSR/Trigger envelope, pitch engine, pitch
+    // envelope). Defaults reproduce the pre-S15 engine EXCEPT the pitch engine default is
+    // Preserve (S16-F1). A voice reads this at start(). Struct defined above SampleData.
+    ZonePlayParams play;
+
+    // 2 iff a matching-length second channel exists; else 1. A framesR of a different
+    // length than frames is treated as absent (mono) — a malformed pair never half-plays.
+    int channelCount() const {
+        return (!framesR.empty() && framesR.size() == frames.size()) ? 2 : 1;
+    }
+
+};
+
+// ---------------------------------------------------------------------------
+// Keymap — the performance map (instrument-owned, D-B). A note+velocity resolves
+// to at most one zone; a zone names which SampleData to play and the root note to
+// repitch from. Tier-0 degenerate case: a single zone spanning [0,127] with the
+// sample's own root. Tier-1: several zones, each a key range with its own root.
+//
+// TIER-2 EXTENSION (velocity layers / round-robin) — designed for, not built:
+// resolution returns a zone; a zone today owns one sampleIndex. Tier 2 makes a zone
+// own a *list* of (velocity-range, sampleIndex) layers (and round-robin sets), and
+// resolve() gains the velocity dimension it already receives but currently ignores
+// for selection. The (note, velocity) signature and the "resolve to a zone, then a
+// sample within it" shape are already in place — Tier 2 fills in the second step
+// without changing callers or the voice engine. See the report note.
+// ---------------------------------------------------------------------------
+
+// A key range [lowNote, highNote] (inclusive both ends) mapping to one sample, with
+// the root note to repitch from (defaults to the sample's own root, overridable in
+// the performance map per S5). velocityLow/High reserved for Tier-2 layers; today a
+// zone accepts the full 1..127 velocity range (0 is note-off by MIDI convention).
+struct KeyZone {
+    int lowNote = 0;
+    int highNote = 127;
+    int rootNote = 60;        // repitch reference for this zone
+    std::size_t sampleIndex = 0;  // index into Keymap::samples
+};
+
+// Result of resolving a (note, velocity). `matched == false` means the note falls in
+// no zone (out-of-zone) — a defined no-play result, NOT an error and NOT voice 0.
+struct ZoneResolution {
+    bool matched = false;
+    std::size_t zoneIndex = 0;   // valid only when matched
+};
+
+// The keymap: the decoded samples plus the zones that map keys onto them. Owns
+// resolution. Pure: no host types. Zones are tested first-match in order, so an
+// earlier zone wins an overlap (deterministic, documented).
+struct Keymap {
+    std::vector<SampleData> samples;
+    std::vector<KeyZone> zones;
+
+    // Resolves (note, velocity) to a zone. First zone (in order) whose [low,high]
+    // contains `note` wins. velocity is accepted now (Tier-2 seam) but does not
+    // affect zone choice at Tier 0-1. Returns {matched=false} when no zone contains
+    // the note.
+    ZoneResolution resolve(int note, int velocity) const;
+
+    // Convenience: build the Tier-0 degenerate keymap — one sample mapped
+    // chromatically across the whole keyboard from its own root note.
+    static Keymap singleSampleChromatic(SampleData sample);
+};
+
+// The chromatic pitch ratio to play `note` given a sample recorded at `rootNote`:
+// 2^((note - rootNote) / 12). note == rootNote -> 1.0 (unity). One octave up -> 2.0,
+// one octave down -> 0.5. Pure equal-temperament; no reference-frequency needed.
+double pitchRatio(int note, int rootNote);
+
+// ---------------------------------------------------------------------------
+// AHDSR amplitude envelope (S15 grows the S3 ADSR with a HOLD stage). Sample-based
+// (times in frames), linear segments. A gate: noteOn() enters Attack; noteOff() enters
+// Release from wherever it is. Asserted against a known signal in the tests (mirror of peaks).
+//
+// Segment math (all linear ramps):
+//   Attack:  0 -> 1 over attackFrames
+//   Hold:    hold 1 over holdFrames                     (S15: NEW stage between A and D)
+//   Decay:   1 -> sustainLevel over decayFrames
+//   Sustain: hold sustainLevel until noteOff
+//   Release: currentLevel -> 0 over releaseFrames
+// A zero-length attack jumps straight to 1 on the first frame; HOLDFRAMES == 0 skips Hold
+// entirely, which is EXACTLY the pre-S15 ADSR (back-compat — existing Gate play is unchanged);
+// zero decay jumps to sustain; a noteOff during attack/hold/decay (release-before-sustain)
+// releases from the current partial level, not from sustainLevel. AdsrParams is defined above
+// (with the other per-zone value structs); this section holds only the per-frame evaluator.
+// ---------------------------------------------------------------------------
+
+class AdsrEnvelope {
+public:
+    enum class Stage { Idle, Attack, Hold, Decay, Sustain, Release, Finished };
+
+    void configure(const AdsrParams& params) { params_ = params; }
+
+    // Gate on: (re)start from Attack.
+    void noteOn();
+    // Gate off: enter Release from the current level.
+    void noteOff();
+
+    // Advances one frame and returns the amplitude for THIS frame (before advancing).
+    // Once Release completes the envelope latches Finished and returns 0.0 forever
+    // (until the next noteOn). A single, monotonic per-frame step — the caller pulls
+    // one value per output frame.
+    double tick();
+
+    Stage stage() const { return stage_; }
+    bool finished() const { return stage_ == Stage::Finished; }
+    double level() const { return level_; }
+
+private:
+    AdsrParams params_;
+    Stage stage_ = Stage::Idle;
+    double level_ = 0.0;
+    std::int64_t framesInStage_ = 0;
+    double releaseFrom_ = 0.0;  // level at the moment noteOff() was called
+};
+
+// ---------------------------------------------------------------------------
+// S15 Trigger amplitude envelope (per-frame evaluator). The PlayMode / TriggerParams /
+// FadeCurve value structs are defined above with the other per-zone params.
+// ---------------------------------------------------------------------------
+
+// Trigger amplitude envelope: a stateless-shape amplitude function over the play span, evaluated
+// at a SOURCE-frame offset into the span. Anchoring the fades to SOURCE frames (not output
+// frames) is what makes S15 compose with S16: under Preserve the read advances at source rate so
+// output and source frames coincide, but under Varispeed a transposed voice consumes source
+// faster — driving the fades off the read position keeps the fade-in/out anchored to the SAME
+// source frames regardless of engine (the play-length end is a source-frame fact, S15×S16). The
+// voice reports the read offset; this maps it to amplitude. Distinct from AHDSR — time-boxed by
+// the play length and note-off-immune. Reports finished() once the offset reaches the play length.
+class TriggerEnvelope {
+public:
+    // Configure from the play span + fades. `playLengthFrames` is (playEnd - startFrame): the
+    // SOURCE-frame length of the play span. Fades are clamped so fadeIn + fadeOut <= playLength
+    // (fadeOut anchored to the end). A zero/negative play length finishes immediately.
+    void configure(std::int64_t playLengthFrames, std::int64_t fadeInFrames,
+                   std::int64_t fadeOutFrames, FadeCurve curve = kDefaultFadeCurve);
+
+    // Amplitude in [0,1] at `sourceOffset` = (readPos - startFrame) source frames into the play
+    // span. Latches finished() once the offset reaches the play length (>= playLength). Pure over
+    // the offset (no internal advance) so it composes with either pitch engine's read rate.
+    double amplitudeAt(double sourceOffset);
+
+    bool finished() const { return finished_; }
+
+private:
+    std::int64_t playLength_ = 0;
+    std::int64_t fadeIn_ = 0;
+    std::int64_t fadeOut_ = 0;
+    FadeCurve curve_ = kDefaultFadeCurve;
+    bool finished_ = false;
+};
+
+// ---------------------------------------------------------------------------
+// S16 pitch envelope (per-frame evaluator). The PitchEngine / PitchEnvParams value structs
+// and the kDefaultPitchEngine / kPreserveWindowMs constants are defined above.
+// ---------------------------------------------------------------------------
+
+// Per-frame AD pitch-envelope evaluator. tick() returns the CURRENT pitch offset in semitones
+// (0 when disabled or past attack+decay), advancing one frame. The voice converts the semitone
+// offset to a ratio multiply (Varispeed) or a shift-amount add (Preserve). Pure, unit-tested
+// for offset at t=0, peak at t=attack, and 0 at t=attack+decay.
+class PitchEnvelope {
+public:
+    void configure(const PitchEnvParams& params) { params_ = params; pos_ = 0; }
+    void noteOn() { pos_ = 0; }
+
+    // Advance one frame, return this frame's pitch offset in semitones.
+    double tick();
+
+private:
+    PitchEnvParams params_;
+    std::int64_t pos_ = 0;
+};
+
+// ---------------------------------------------------------------------------
+// A single voice: one active note playing one repitched, enveloped sample. Reads
+// the sample by fractional frame position with linear interpolation, advancing by
+// the pitch ratio; loops the sustain region for held notes past the loop end.
+// ---------------------------------------------------------------------------
+
+class Voice {
+public:
+    // Starts this voice on `note` at `velocity`, playing `sample` (a stable reference
+    // the caller must keep alive for the voice's lifetime — the Keymap owns it), repitched
+    // from `rootNote`. All five AHDSR fields (A/H/D/S/R) are read directly from
+    // sample.play.adsr — the per-zone values (in FRAMES) resolved from the stored seconds by
+    // buildTier0Keymap / buildZonedKeymap against the live sample rate. The S15 play MODE +
+    // Trigger params and the S16 pitch ENGINE + pitch envelope are read from `sample.play`.
+    // The Preserve shifters MUST already be pre-sized (presizePreserveShifters, off-thread) —
+    // start() only reset()s + warm()s them (RT-safe, no allocation) since it runs on the audio
+    // thread inside process(). The warm silence pass settles the OLA taps before the first
+    // output frame (no cold-start click). Byte-identical to the pre-S15 engine when sample.play
+    // is default (Gate + Varispeed + no pitch env).
+    void start(int note, int velocity, const SampleData& sample, int rootNote);
+
+    // Gate off — begins the amplitude release. In GATE mode this enters the AHDSR release; in
+    // TRIGGER mode it is a NO-OP (Trigger ignores note-off and plays through to its play length).
+    void release();
+
+    // True while this voice is producing (or about to produce) sound.
+    bool active() const { return active_; }
+    // The note this voice was started on (for note-off routing). Meaningless if idle.
+    int note() const { return note_; }
+    // Monotonic age counter — higher = started earlier relative to others. The voice
+    // engine uses this for its stealing policy (oldest first). Set by the engine.
+    std::uint64_t startOrder() const { return startOrder_; }
+    void setStartOrder(std::uint64_t order) { startOrder_ = order; }
+    bool releasing() const { return releasing_; }
+    // The S16 pitch engine this voice is running (for the engine's Preserve-voice tally). Only
+    // meaningful while active().
+    PitchEngine pitchEngine() const { return pitchEngine_; }
+
+    // Pre-SIZE this voice's Preserve pitch shifters (both channels) to `windowFrames`, OFF the
+    // audio thread (this allocates). The engine calls it once at construction so start() — which
+    // runs on the audio thread inside process() — never allocates: start() only reset()s + warm()s
+    // the already-sized rings. `windowFrames` <= 1 leaves the shifters as pass-through (Varispeed
+    // instruments pay no ring cost). Idempotent: a re-presize to the same window is a cheap no-op
+    // in the underlying vector.
+    void presizePreserveShifters(std::int64_t windowFrames);
+
+    // Renders one frame's contribution, advancing the read head and envelope by one
+    // output frame. Returns 0.0 (and goes idle) once the envelope finishes or the
+    // sample runs out with no loop. The value is already velocity- and
+    // envelope-scaled — the engine sums voices directly. This is the MONO path (channel
+    // 0 only) — byte-identical to the pre-S7 engine, so mono play is unchanged.
+    AudioSample renderFrame();
+
+    // STEREO render: writes THIS frame's per-channel contribution into `l`/`r` and advances
+    // the read head + envelope by exactly one frame (the same single advance the mono path
+    // performs — the envelope ticks ONCE per frame, shared across both channels). For a mono
+    // sample (channelCount()==1) both `l` and `r` receive the same value (dual-mono / centered).
+    // Both outputs are already velocity- and envelope-scaled. Goes idle on the same conditions
+    // as the mono path (envelope finished / sample exhausted with no loop) writing 0 to both.
+    void renderFrameStereo(AudioSample& l, AudioSample& r);
+
+private:
+    // Shared read/advance for both render paths: computes the interpolated per-channel
+    // value(s) at the current read head, ticks the amplitude + pitch envelopes once, applies
+    // the pitch engine (Varispeed read-rate bias OR Preserve shift), advances the head, and
+    // latches idle on exhaustion. `stereo` selects whether the second channel is read (and
+    // returned in `outR`); when false `outR` is left untouched. Returns the channel-0 value.
+    AudioSample advanceFrame(bool stereo, AudioSample& outR);
+
+    // This frame's amplitude in [0,1] from the active envelope. GATE: the AHDSR ticks once per
+    // output frame (independent of the read rate — envelope time is wall-clock). TRIGGER: the
+    // fade shape is evaluated at the SOURCE offset (readPos - startFrame) so the fades anchor to
+    // source frames and compose with either pitch engine. Sets amplitudeDone_ when the envelope
+    // finishes (Gate: release complete; Trigger: play length reached) so advanceFrame frees the voice.
+    double tickAmplitude();
+
+    bool active_ = false;
+    bool releasing_ = false;
+    int note_ = 0;
+    double velocityGain_ = 1.0;
+    double baseRatio_ = 1.0;     // 2^((note-root)/12): the un-modulated repitch ratio
+    double ratio_ = 1.0;         // fractional SOURCE frames advanced per output frame (this frame)
+    double readPos_ = 0.0;       // fractional frame index into the sample
+    const SampleData* sample_ = nullptr;
+
+    // S15 play mode + amplitude envelopes. Gate uses env_ (AHDSR); Trigger uses trigEnv_. Only
+    // one is active per voice (selected by playMode_ at start). playEnd_ is Trigger's source-frame
+    // stop (the voice frees when readPos_ >= playEnd_, mirroring the run-off-end idle).
+    PlayMode playMode_ = PlayMode::Gate;
+    AdsrEnvelope env_;
+    TriggerEnvelope trigEnv_;
+    std::int64_t startFrame_ = 0;  // clamped initial read frame; Trigger fade offset origin
+    std::int64_t playEnd_ = 0;   // Trigger: source-frame end; Gate: unused
+    bool amplitudeDone_ = false; // set when the active amplitude envelope finished
+
+    // S16 pitch engine + pitch envelope. pitchEngine_ selects Varispeed (ratio bias) vs Preserve
+    // (source-rate read + shifter). shiftL_/shiftR_ transpose the Preserve output per channel
+    // (one read head, per-channel shift — S7 compose). pitchEnv_ rides EITHER engine.
+    PitchEngine pitchEngine_ = PitchEngine::Varispeed;
+    PitchEnvelope pitchEnv_;
+    PitchShifter shiftL_;
+    PitchShifter shiftR_;
+
+    std::uint64_t startOrder_ = 0;
+};
+
+// ---------------------------------------------------------------------------
+// The polyphonic voice engine: a fixed pool of voices, note-on allocation with
+// bounded voice stealing, note-off routing, and block rendering (sum of voices).
+//
+// VOICE-STEALING POLICY (deterministic, documented): when all voices are busy and a
+// new note-on arrives, steal in this priority order:
+//   1. the oldest voice already in RELEASE (finishing anyway — cheapest to cut),
+//   2. else the oldest voice overall (longest-held note gives way to the new one).
+// "Oldest" = smallest startOrder (assigned monotonically at note-on). This is the
+// standard hardware-sampler policy: prefer to sacrifice a dying tail, and failing
+// that, the note that has already had the most time.
+// ---------------------------------------------------------------------------
+
+class VoiceEngine {
+public:
+    // Builds an engine with `maxVoices` voices (the polyphony bound) playing from
+    // `keymap`. The keymap must outlive the engine (the engine holds a reference — it
+    // reads zones and sample data through it, never copies PCM). Every AHDSR field (A/H/D/S/R)
+    // + play mode + pitch engine rides on each zone's SampleData::play (in FRAMES, resolved
+    // from the stored seconds at keymap build); the engine holds no instrument-wide ADSR.
+    // `preserveVoiceCap` (S16) bounds how many Preserve-engine voices may sound at once (the
+    // shifter is materially heavier than Varispeed) — a Preserve note-on beyond the cap is
+    // dropped rather than glitching; 0 means "no separate Preserve cap" (bounded only by
+    // maxVoices). `preserveWindowFrames` is the OLA window (in OUTPUT frames) every voice's
+    // Preserve pitch shifters are PRE-SIZED to at construction (OFF the audio thread), so
+    // note-on (which runs in process()) never allocates; 0 leaves them pass-through (a
+    // Varispeed-only instrument pays no ring cost). The processor derives it from the host
+    // sample rate (kPreserveWindowMs). Defaulted so existing callers (and the pure-core tests)
+    // are unaffected.
+    VoiceEngine(std::size_t maxVoices, const Keymap& keymap,
+                std::size_t preserveVoiceCap = 0, std::int64_t preserveWindowFrames = 0);
+
+    // MIDI note-on. Resolves the note+velocity to a zone; if none matches (out of
+    // zone) it is a defined no-op (no voice consumed). Otherwise allocates a free
+    // voice, or steals one per the policy above. Returns the index of the voice used,
+    // or kNoVoice for an out-of-zone (unplayed) note.
+    std::size_t noteOn(int note, int velocity);
+
+    // MIDI note-off. Releases the most-recently-started active, non-releasing voice
+    // playing `note` (so a re-triggered same note releases the newest first, leaving
+    // the older tail to ring — matches hardware behavior). No-op if none match.
+    void noteOff(int note);
+
+    // REAL-TIME render (S4): sums all active voices into the caller-provided buffer
+    // `out[0..frameCount)`, ADDING to whatever is there (the caller clears or mixes —
+    // this never touches memory it does not own and NEVER allocates). This is the
+    // audio-thread entry point: the VST3 process callback passes the host's own output
+    // channel buffer, so no allocation, resize, or heap traffic happens under process.
+    // Voices that finish mid-block go idle and stop contributing. `out` must point at
+    // at least `frameCount` writable samples; a null `out` or zero count is a no-op.
+    void render(AudioSample* out, std::size_t frameCount);
+
+    // REAL-TIME stereo render (S7): sums all active voices per-channel into the caller's two
+    // buffers `left`/`right` (each `frameCount` writable samples), ADDING to whatever is there
+    // (the caller clears/mixes). Same RT discipline as the mono overload — no allocation, no
+    // resize, no lock. A mono sample plays dual-mono (same value to both channels, centered);
+    // a stereo sample plays its two channels. A null buffer or zero count is a no-op. The mono
+    // and stereo render paths are independent output shapes over the SAME voice pool; the active
+    // channel mode (mono vs stereo bus) picks which one the process callback drives per block.
+    void render(AudioSample* left, AudioSample* right, std::size_t frameCount);
+
+    // TEST / off-thread convenience: appends `frameCount` summed frames to `out`
+    // (grows it — DO NOT call on the audio thread; it allocates). Delegates to the
+    // real-time overload after sizing the buffer, so both paths share one mix loop.
+    // Does not clear existing contents — appends, matching the pre-S4 contract the
+    // unit tests rely on.
+    void render(std::vector<AudioSample>& out, std::size_t frameCount);
+
+    // Count of currently active voices (for tests / diagnostics).
+    std::size_t activeVoiceCount() const;
+
+    std::size_t maxVoices() const { return voices_.size(); }
+
+    static constexpr std::size_t kNoVoice = static_cast<std::size_t>(-1);
+
+private:
+    // Picks a voice to (re)use for a new note-on: a free voice if any, else a stolen
+    // one per the documented policy. Always returns a valid index (maxVoices >= 1).
+    std::size_t allocateVoice();
+
+    // Count of active Preserve-engine voices (for the S16 Preserve cap). Rescanned per note-on
+    // (cheap: bounded by maxVoices) rather than maintained as a running tally.
+    std::size_t activePreserveVoices() const;
+
+    std::vector<Voice> voices_;
+    const Keymap& keymap_;
+    std::size_t preserveVoiceCap_ = 0;  // S16: max simultaneous Preserve voices (0 = no separate cap)
+    std::uint64_t nextStartOrder_ = 1;  // monotonic; 0 reserved for "never started"
+};
+
+} // namespace reasampler

src/vst/vst_entry.cpp

@@ -0,0 +1,82 @@
+// vst_entry.cpp — the VST3 module class factory (Phase S1). Enumerates the one class
+// this module offers (the ReaSampler instrument) via the SDK's factory macros. The
+// Windows module exports — GetPluginFactory (here, via BEGIN_FACTORY) and
+// InitDll/ExitDll (from the SDK's dllmain.cpp) — are how REAPER discovers and loads a
+// VST3.
+//
+// VERIFIED (corrects §1a's "experienced estimate" flags on export names + macros,
+// against vendor/vst3sdk/public.sdk/source/main/):
+//   * Windows exports: InitDll / ExitDll (SMTG_EXPORT_SYMBOL, in dllmain.cpp) +
+//     GetPluginFactory (SMTG_EXPORT_SYMBOL IPluginFactory* PLUGIN_API, emitted by the
+//     BEGIN_FACTORY macro). The plug-in must provide InitModule/DeinitModule — supplied
+//     here by linking moduleinit.cpp (the SDK's default one-time init/term).
+//   * Factory macros: BEGIN_FACTORY(vendor,url,email,flags) / DEF_CLASS2(...) /
+//     END_FACTORY — exact spellings from pluginfactory.h.
+//   * Instrument subcategory string: "Instrument|Synth|Sampler"
+//     (PlugType::kInstrumentSynthSampler, ivstaudioprocessor.h).
+//   * classFlags = 0 for a SingleComponentEffect (non-distributable), matching the
+//     AGain example.
+
+#include "public.sdk/source/main/pluginfactory.h"
+
+#include "pluginterfaces/vst/ivstaudioprocessor.h"  // kVstAudioEffectClass, PlugType
+
+#include "app_version.h"       // vstPluginName / appVersion — the channel-derived identity
+#include "ext_keys.h"          // kProjExtNamespace — the pairing-surface assertion target
+#include "reasampler_processor.h"
+#include "reasampler_vst.h"    // channel-selected class UID (REASAMPLER_ACTIVE_UID_*)
+
+// CHANNEL PAIRING INVARIANT (S18). The instrument's PLUGIN identity forks by the ONE channel
+// bit (REASAMPLER_CHANNEL_IS_BETA — the class UID selected in reasampler_vst.h, the filename
+// + display name in app_version). Its DATA identity forks by the SAME bit, one layer down:
+// ext_keys.h's kProjExtNamespace() delegates to app_version::extStateNamespace(), so a beta
+// binary reads "reasampler_beta". Both derive from that one bit, so a beta VST can only ever
+// talk to the beta extension.
+//
+// The guard below pins the two forks together so a refactor cannot split them. It asserts
+// that the CLASS UID this factory registers (REASAMPLER_ACTIVE_UID_1, selected by the #if in
+// reasampler_vst.h) is the UID that matches THIS binary's channel bit. If someone edited that
+// #if to pick the wrong branch — registering the stable UID in a beta build, or vice versa —
+// the instrument's identity would diverge from the namespace ext_keys reads (a beta-named
+// plugin presenting the stable UID, or reading the stable banks under a beta identity). That
+// is exactly the silent split the invariant forbids, and it breaks the build here instead.
+// (The namespace itself is a runtime accessor — .c_str() on a channel-selected string — so
+// the couplable compile-time fact is the UID selection, not the namespace value; the
+// app_version_tests pin the namespace string per channel.)
+#if REASAMPLER_CHANNEL_IS_BETA
+static_assert(REASAMPLER_ACTIVE_UID_1 == REASAMPLER_PROC_UID_BETA_1 &&
+              REASAMPLER_ACTIVE_UID_2 == REASAMPLER_PROC_UID_BETA_2 &&
+              REASAMPLER_ACTIVE_UID_3 == REASAMPLER_PROC_UID_BETA_3 &&
+              REASAMPLER_ACTIVE_UID_4 == REASAMPLER_PROC_UID_BETA_4,
+              "S18: a beta build must register the BETA class UID that pairs with the beta "
+              "extension's ext-state namespace — the UID selection and the channel bit split");
+#else
+static_assert(REASAMPLER_ACTIVE_UID_1 == REASAMPLER_PROC_UID_1 &&
+              REASAMPLER_ACTIVE_UID_2 == REASAMPLER_PROC_UID_2 &&
+              REASAMPLER_ACTIVE_UID_3 == REASAMPLER_PROC_UID_3 &&
+              REASAMPLER_ACTIVE_UID_4 == REASAMPLER_PROC_UID_4,
+              "S18: a stable build must register the STABLE class UID that pairs with the "
+              "stable ext-state namespace — the UID selection and the channel bit split");
+#endif
+
+BEGIN_FACTORY(reasampler::vst::kVendorName, reasampler::vst::kVendorUrl,
+              reasampler::vst::kVendorEmail, Steinberg::PFactoryInfo::kNoFlags)
+
+// The display name and version are channel-derived from app_version — sourced here, not
+// as literals. DEF_CLASS2 expands inside GetPluginFactory() and PClassInfo2's constructor
+// copies the char* into its own fixed buffer at that runtime call, so .c_str() on the
+// accessors' static-storage strings is valid (no dangling — the refs outlive the copy).
+// vstPluginName(): "ReaSampler 9000" / "ReaSampler 9000 beta". appVersion(): "0.9.01" /
+// "0.9.01-beta" (the -beta render V4 already yields on beta).
+DEF_CLASS2(INLINE_UID(REASAMPLER_ACTIVE_UID_1, REASAMPLER_ACTIVE_UID_2,
+                      REASAMPLER_ACTIVE_UID_3, REASAMPLER_ACTIVE_UID_4),
+           Steinberg::PClassInfo::kManyInstances,       // cardinality
+           kVstAudioEffectClass,                        // component category (fixed)
+           reasampler::vstPluginName().c_str(),         // plug-in display name (channel-derived)
+           0,                                           // single-component => 0
+           Steinberg::Vst::PlugType::kInstrumentSynthSampler,  // subcategory
+           reasampler::appVersion().c_str(),            // plug-in version (channel: -beta render)
+           kVstVersionString,                           // VST3 SDK version (fixed)
+           reasampler::vst::ReaSamplerProcessor::createInstance)
+
+END_FACTORY

src/vst/waveform_view.cpp

@@ -0,0 +1,99 @@
+// waveform_view.cpp — see waveform_view.h. Pure math; no host types.
+
+#include "waveform_view.h"
+
+#include <algorithm>
+#include <cstdlib>  // std::abs (int overload)
+
+namespace reasampler::vst {
+
+namespace {
+
+std::int64_t clampFrame(std::int64_t f, std::int64_t frameCount) {
+    if (f < 0) return 0;
+    if (f > frameCount) return frameCount;
+    return f;
+}
+
+}  // namespace
+
+int frameToX(const Rect& area, std::int64_t frameCount, std::int64_t frame) {
+    const int w = std::max(0, area.width());
+    if (frameCount <= 0 || w <= 0) return area.left;
+    const std::int64_t f = clampFrame(frame, frameCount);
+    // Linear map: x = left + round(f * w / frameCount). Rounding keeps the marker line
+    // visually centered on its frame; the divide is exact rational (multiply first).
+    const std::int64_t num = f * static_cast<std::int64_t>(w) + frameCount / 2;
+    return area.left + static_cast<int>(num / frameCount);
+}
+
+std::int64_t xToFrame(const Rect& area, std::int64_t frameCount, int x) {
+    const int w = std::max(0, area.width());
+    if (frameCount <= 0 || w <= 0) return 0;
+    if (x <= area.left) return 0;
+    if (x >= area.right) return frameCount;
+    const std::int64_t dx = static_cast<std::int64_t>(x - area.left);
+    // Inverse of frameToX: frame = round(dx * frameCount / w). Round so click and marker draw
+    // agree at bin granularity.
+    const std::int64_t num = dx * frameCount + static_cast<std::int64_t>(w) / 2;
+    return clampFrame(num / static_cast<std::int64_t>(w), frameCount);
+}
+
+int markerAtPoint(const Rect& area, std::int64_t frameCount, const std::int64_t* frames,
+                  int count, int x, int y) {
+    if (count <= 0 || frames == nullptr) return -1;
+    if (!contains(area, x, y)) return -1;
+    for (int i = 0; i < count; ++i) {
+        const int mx = frameToX(area, frameCount, frames[i]);
+        if (x >= mx - kMarkerGrabWidth && x <= mx + kMarkerGrabWidth) return i;
+    }
+    return -1;
+}
+
+std::int64_t resolveDragFrame(const Rect& area, std::int64_t frameCount, std::int64_t startFrame,
+                              int dxPixels) {
+    const std::int64_t start = clampFrame(startFrame, frameCount);
+    if (dxPixels == 0) return start;
+    const int w = std::max(0, area.width());
+    if (frameCount <= 0 || w <= 0) return start;  // no room to move
+    // Proportional shift, rounded to the nearest frame (same linear map as frameToX/xToFrame).
+    const std::int64_t magnitude =
+        (static_cast<std::int64_t>(std::abs(dxPixels)) * frameCount +
+         static_cast<std::int64_t>(w) / 2) /
+        static_cast<std::int64_t>(w);
+    const std::int64_t shift = dxPixels > 0 ? magnitude : -magnitude;
+    return clampFrame(start + shift, frameCount);
+}
+
+std::int64_t nearestZeroCrossing(const AudioSample* pcm, std::int64_t frames,
+                                 std::int64_t target) {
+    if (pcm == nullptr || frames < 2) return clampFrame(target, frames > 0 ? frames - 1 : 0);
+    // Clamp target into a valid sample index [0, frames).
+    std::int64_t t = target;
+    if (t < 0) t = 0;
+    if (t > frames - 1) t = frames - 1;
+
+    // A crossing lives at frame i (1 <= i < frames) when sign(pcm[i-1]) != sign(pcm[i]) OR
+    // pcm[i] == 0. isCrossing(i) tests exactly that. We fan out from t: at each distance d we
+    // probe t-d before t+d, so an equidistant tie resolves to the LOWER frame (deterministic).
+    auto isCrossing = [&](std::int64_t i) -> bool {
+        if (i < 1 || i >= frames) return false;
+        const AudioSample a = pcm[i - 1];
+        const AudioSample b = pcm[i];
+        if (b == 0.0f) return true;                  // a sample on zero is its own crossing
+        return (a < 0.0f) != (b < 0.0f);             // sign change between i-1 and i
+    };
+
+    if (isCrossing(t)) return t;
+    for (std::int64_t d = 1; d < frames; ++d) {
+        const std::int64_t lo = t - d;
+        if (lo >= 1 && isCrossing(lo)) return lo;    // lower side wins the tie
+        const std::int64_t hi = t + d;
+        if (hi < frames && isCrossing(hi)) return hi;
+        // Stop once both probes have run off both ends — no crossing anywhere.
+        if (lo < 1 && hi >= frames) break;
+    }
+    return t;  // no sign change in the whole buffer -> keep the raw (clamped) target
+}
+
+}  // namespace reasampler::vst

src/vst/waveform_view.h

@@ -0,0 +1,83 @@
+// waveform_view.h — PURE waveform/marker geometry + zero-crossing snap for the S11
+// waveform surface. NO VST3, NO REAPER, NO SWELL/LICE types at the boundary. The mirror
+// of keyboard_strip / editor_geometry: the fiddly frame<->pixel + marker hit-test + snap
+// arithmetic lives here, unit-tested outside the DAW, while the editor shell
+// (reasampler_editor.cpp) draws the envelope + markers and marshals mouse events into it.
+//
+// The surface maps a sample's full frame span [0, frameCount] linearly across a horizontal
+// waveform rect. Draggable MARKERS mark frames of interest (S11: start point, loop start,
+// loop end). The marker set is GENERIC — N named markers with drag + snap — deliberately
+// not three hardcoded specials, so S15 (Trigger/Gate) can repurpose this same surface with a
+// different marker set (start + %-length end + fades) without reworking the machinery.
+//
+// Interaction resolves through the pure DRAG-DELTA resolver here: the shell captures a grab
+// on WM_LBUTTONDOWN (markerAtPoint identifies the grabbed marker), feeds each WM_MOUSEMOVE's
+// pixel delta back through resolveDragFrame (which clamps + optionally zero-crossing-snaps),
+// and commits on WM_LBUTTONUP. Live feedback is the shell re-drawing the in-flight frame.
+//
+// It reuses the same Rect + contains() as editor_geometry (one shared geometry idiom), so
+// this header depends on editor_geometry.h rather than redefining a rectangle type. Audio
+// is the peaks AudioSample float alias (the one house precedent — sampler_core / wav_trim do
+// the same), so the zero-crossing helper takes the same mono PCM the shell already decoded.
+
+#pragma once
+
+#include <cstdint>
+
+#include "editor_geometry.h"  // Rect, contains — one shared geometry idiom
+#include "peaks.h"            // AudioSample (float), the mono PCM the snap scans
+
+namespace reasampler::vst {
+
+// The width (px) of a marker's grab region either side of its x line: a grab within this many
+// pixels of a marker's drawn x is a grab OF that marker. Mirrors keyboard_strip's edge-grab
+// idiom — wide enough to grab a 1px line comfortably, narrow enough that adjacent markers stay
+// distinguishable.
+inline constexpr int kMarkerGrabWidth = 5;
+
+// The x pixel (inside `area`) of frame `frame` under the linear map: frame 0 -> area.left,
+// frame frameCount -> area.right. A frame is clamped to [0, frameCount] before mapping, so an
+// out-of-range frame pins to an edge rather than escaping the rect. frameCount <= 0 or a
+// zero-width area pins every frame to area.left (a degenerate, non-inverting result). Pure.
+int frameToX(const Rect& area, std::int64_t frameCount, std::int64_t frame);
+
+// The frame a point x (inside `area`) maps to under the inverse linear map, clamped to
+// [0, frameCount]. A point left of area.left yields 0; right of area.right yields frameCount.
+// frameCount <= 0 or a zero-width area yields 0. Pure — the inverse of frameToX (round-trips
+// to the same frame at bin granularity).
+std::int64_t xToFrame(const Rect& area, std::int64_t frameCount, int x);
+
+// Which marker (index into a caller-supplied parallel `frames` array, in draw order) a grab at
+// (x, y) lands on, or -1 for a point off every marker (or off the waveform area). A marker is
+// grabbed when x is within kMarkerGrabWidth of its drawn x AND y is inside `area`. First marker
+// in order wins a tie where two markers overlap within the grab band (deterministic, mirroring
+// keyboard_strip's first-match). `frames` is `count` frame indices; a null/empty array or
+// count <= 0 yields -1. Pure — a raw pointer at the boundary (no host container), like
+// keyboard_strip::zoneBarAtPoint.
+int markerAtPoint(const Rect& area, std::int64_t frameCount, const std::int64_t* frames,
+                  int count, int x, int y);
+
+// Resolve a drag to a new frame. Given the frame the grabbed marker held at grab time
+// (`startFrame`) and the horizontal pixel delta since grab (`dxPixels`), returns the frame the
+// marker should now hold: startFrame shifted by round(dxPixels * frameCount / areaWidth),
+// clamped to [0, frameCount]. A zero-width area or non-positive frameCount pins the result to
+// the clamped startFrame (no motion). This is the single arithmetic behind every marker drag;
+// the shell applies clamps BETWEEN markers (start <= loopEnd, loopStart <= loopEnd) after this
+// per-marker resolve. Pure — rounding is to the nearest frame. Returns the clamped startFrame
+// for dxPixels == 0.
+std::int64_t resolveDragFrame(const Rect& area, std::int64_t frameCount, std::int64_t startFrame,
+                              int dxPixels);
+
+// The nearest zero-crossing frame to `target` in the mono PCM, for the loop/start snap (the
+// S2 zero-crossing-aware requirement). A zero crossing is a frame index i (1 <= i < frames)
+// where the sign of pcm[i-1] and pcm[i] differ (a sample exactly 0 counts as its own crossing
+// — pcm[i] == 0 snaps to i). The search fans out symmetrically from the clamped target and
+// returns the closest crossing frame; ties (equidistant crossings on both sides) resolve to
+// the LOWER frame (deterministic). When the PCM has NO sign change anywhere (all one sign, or
+// fewer than 2 frames), returns the clamped target unchanged (nothing to snap to — the caller
+// keeps the raw frame). `target` is clamped to [0, frames) before searching. Pure — scans the
+// decoded PCM the shell already holds; no host types, no file I/O.
+std::int64_t nearestZeroCrossing(const AudioSample* pcm, std::int64_t frames,
+                                 std::int64_t target);
+
+}  // namespace reasampler::vst

tests/test_app_version.cpp

@@ -74,6 +74,40 @@ static void testChannelDerivedIdentityStrings() {
     }
 }
 
+static void testVstIdentityStringsForkByChannel() {
+    // S18: the VST3 instrument's on-disk name and display name fork from the SAME one channel
+    // bit as the extension's idents above. Stable values are BYTE-IDENTICAL to pre-S18 — any
+    // drift in the stable branch orphans a saved instance's on-disk reference / mislabels the
+    // FX browser. These are the accessors vst_entry.cpp's factory, the editor title, and the
+    // embed label all source; each branch is the assertion the OTHER config's build would fail.
+    if (isBeta()) {
+        CHECK(vstOutputName() == "reasampler_9000_beta");
+        CHECK(vstPluginName() == "ReaSampler 9000 beta");
+    } else {
+        CHECK(vstOutputName() == "reasampler_9000");
+        CHECK(vstPluginName() == "ReaSampler 9000");
+    }
+    // The on-disk name must match the CMake OUTPUT_NAME fork (REASAMPLER_VST_OUTPUT_NAME): a
+    // divergence between this accessor and the artifact name would ship a binary whose
+    // self-identification disagrees with its filename. (The CMake side is the authoritative
+    // artifact name; this pins the in-binary derivation to the same two literals.)
+    CHECK(vstOutputName() == (isBeta() ? "reasampler_9000_beta" : "reasampler_9000"));
+}
+
+static void testVstIdentityAndDataNamespaceShareOneChannel() {
+    // The S18 pairing invariant at the SEAM: the VST's plugin identity (its display/output
+    // names) and the DATA namespace its bridge reads (extStateNamespace(), what ext_keys
+    // delegates to) must resolve to the SAME channel — a beta-named plugin reading the stable
+    // namespace, or vice versa, is precisely the split the invariant forbids. Both forks fan
+    // out from the one isBeta() bit, so this assertion fails if EITHER fork regressed
+    // independently (a beta output name paired with the stable namespace trips the beta arm).
+    const bool identityIsBeta =
+        (vstPluginName() == "ReaSampler 9000 beta") && (vstOutputName() == "reasampler_9000_beta");
+    const bool dataIsBeta = (extStateNamespace() == "reasampler_beta");
+    CHECK(identityIsBeta == dataIsBeta);          // identity and data agree on the channel
+    CHECK(identityIsBeta == isBeta());            // and both agree with the compiled bit
+}
+
 static void testChannelQualifiedIdAndNameComposition() {
     // The two composition helpers the shells funnel through. A representative shipped id
     // (CAPTURE_TRACK) and phrase must compose to the exact channel-qualified strings — this
@@ -205,6 +239,8 @@ int main() {
     testVersionConstantRendersExactString();
     testChannelDerivedRendering();
     testChannelDerivedIdentityStrings();
+    testVstIdentityStringsForkByChannel();
+    testVstIdentityAndDataNamespaceShareOneChannel();
     testChannelQualifiedIdAndNameComposition();
     testStampClassifiesAsStampedOnOwnChannel();
     testParseWellFormed();

tests/test_assignment_request.cpp

@@ -0,0 +1,185 @@
+// Standalone tests for reasampler::AssignmentRequest — no REAPER, no framework.
+// The S8 ingest assignment-request seam: the (bankId, sampleId, generation) value the
+// extension writes to ext-state after an ingest-with-assign, decoded by the instrument
+// in a later dispatch. Only the wire format lives in this module; test it hard because
+// the reader (a different artifact) must decode exactly what this writer produces.
+//
+// Covers: encode/decode round-trip, ids carrying arbitrary bytes (GUIDs, separators),
+// the generation field including zero and negative-guard, and malformed/truncated/
+// trailing-garbage input -> nullopt (the reader's "no pending request" fallback hinges
+// on it).
+
+#include "../src/assignment_request.h"
+
+#include <cstdio>
+#include <string>
+
+using namespace reasampler;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// --- round-trip --------------------------------------------------------------
+
+static void testRoundTrip() {
+    AssignmentRequest req;
+    req.bankId     = "{12345678-1234-1234-1234-1234567890AB}";
+    req.sampleId   = "cap-1700000000-kick.wav";
+    req.generation = 1700000123;
+
+    const std::string wire = encodeAssignmentRequest(req);
+    auto back = decodeAssignmentRequest(wire);
+    CHECK(back.has_value());
+    CHECK(*back == req);
+    // Re-encoding the decoded value is byte-stable (deterministic encoder).
+    CHECK(encodeAssignmentRequest(*back) == wire);
+}
+
+// The pool bank id and an empty-ish generation must round-trip too (generation 0 is the
+// documented pre-S9 default; an assign still carries a real stamp, but 0 must be legal).
+static void testRoundTripPoolAndZeroGeneration() {
+    AssignmentRequest req;
+    req.bankId     = "pool";
+    req.sampleId   = "s1";
+    req.generation = 0;
+
+    auto back = decodeAssignmentRequest(encodeAssignmentRequest(req));
+    CHECK(back.has_value());
+    CHECK(back->bankId == "pool");
+    CHECK(back->sampleId == "s1");
+    CHECK(back->generation == 0);
+}
+
+// Ids carrying the wire's own metacharacters (':' the length delimiter, digits that
+// could be misread as a length, the magic-tag bytes) must survive whole — the whole
+// reason for length-prefixing over a delimiter-split format.
+static void testRoundTripAdversarialIds() {
+    AssignmentRequest req;
+    req.bankId     = "12:34:has-colons";       // ':' is the length delimiter
+    req.sampleId   = "rsassign1-lookalike-99";  // embeds the magic tag
+    req.generation = -42;                        // negative is representable
+
+    auto back = decodeAssignmentRequest(encodeAssignmentRequest(req));
+    CHECK(back.has_value());
+    CHECK(*back == req);
+    CHECK(back->bankId == "12:34:has-colons");
+    CHECK(back->sampleId == "rsassign1-lookalike-99");
+    CHECK(back->generation == -42);
+}
+
+// Empty ids are structurally valid on the wire (length 0) and must round-trip — the
+// decoder must not conflate an empty field with a parse failure.
+static void testRoundTripEmptyFields() {
+    AssignmentRequest req;
+    req.bankId     = "";
+    req.sampleId   = "";
+    req.generation = 7;
+
+    auto back = decodeAssignmentRequest(encodeAssignmentRequest(req));
+    CHECK(back.has_value());
+    CHECK(*back == req);
+}
+
+// A large generation (past 32-bit) must not truncate — the field is int64.
+static void testLargeGeneration() {
+    AssignmentRequest req;
+    req.bankId     = "b";
+    req.sampleId   = "s";
+    req.generation = 9007199254740993LL;  // > 2^53, > INT32_MAX
+
+    auto back = decodeAssignmentRequest(encodeAssignmentRequest(req));
+    CHECK(back.has_value());
+    CHECK(back->generation == 9007199254740993LL);
+}
+
+// --- malformed / tolerant parse ----------------------------------------------
+
+static void testMalformedParse() {
+    // Absence / total garbage — the reader maps these to "no pending request".
+    CHECK(!decodeAssignmentRequest("").has_value());
+    CHECK(!decodeAssignmentRequest("not a request").has_value());
+    // Wrong magic tag.
+    CHECK(!decodeAssignmentRequest("rsprov1" "1:b1:s1:7").has_value());
+    // Magic only, no fields.
+    CHECK(!decodeAssignmentRequest("rsassign1").has_value());
+    // Truncated mid-record (missing the generation field).
+    CHECK(!decodeAssignmentRequest("rsassign1" "4:pool2:s1").has_value());
+    // A length that runs past the end.
+    CHECK(!decodeAssignmentRequest("rsassign1" "99:short").has_value());
+    // Non-numeric length token.
+    CHECK(!decodeAssignmentRequest("rsassign1" "x:pool2:s11:7").has_value());
+    // A non-numeric generation field.
+    CHECK(!decodeAssignmentRequest("rsassign1" "4:pool2:s13:abc").has_value());
+    // A bare "-" generation.
+    CHECK(!decodeAssignmentRequest("rsassign1" "4:pool2:s11:-").has_value());
+}
+
+// Trailing garbage after a well-formed record must be rejected — a partial/padded blob
+// is not a valid request, and the reader must never accept the prefix and ignore the rest.
+static void testTrailingGarbageRejected() {
+    AssignmentRequest req;
+    req.bankId     = "pool";
+    req.sampleId   = "s1";
+    req.generation = 7;
+    const std::string wire = encodeAssignmentRequest(req);
+
+    // The clean value parses.
+    CHECK(decodeAssignmentRequest(wire).has_value());
+    // The same value with any trailing byte does not.
+    CHECK(!decodeAssignmentRequest(wire + "X").has_value());
+    CHECK(!decodeAssignmentRequest(wire + "0:").has_value());
+}
+
+// --- overflow / adversarial integer inputs ------------------------------------
+
+// A 21-digit length field overflows SIZE_MAX and must be rejected safely (no UB,
+// no wrap-around that could make a huge length appear small and pass the bounds check).
+static void testOverflowFieldLength() {
+    // Craft a wire where the bankId length token is 21 digits that exceed SIZE_MAX.
+    // The decoder must fail cleanly, not access memory out of bounds.
+    // "rsassign1" + "999999999999999999999:" (21 nines) + junk: rejects before OOB.
+    const std::string wire = std::string("rsassign1") + "999999999999999999999:junk";
+    CHECK(!decodeAssignmentRequest(wire).has_value());
+}
+
+// A 20-digit generation (exceeds the 19-digit cap) must be rejected safely.
+static void testOverflowFieldInt64() {
+    // Encode a valid record then manually substitute the generation with a 20-digit value.
+    // We cannot use encode (it would produce a correct 19-digit generation), so we
+    // build the wire manually. Generation "99999999999999999999" (20 nines) exceeds cap.
+    // bankId = "pool" (4 bytes), sampleId = "s1" (2 bytes).
+    const std::string wire = std::string("rsassign1")
+                             + "4:pool"
+                             + "2:s1"
+                             + "20:99999999999999999999";
+    CHECK(!decodeAssignmentRequest(wire).has_value());
+}
+
+// SIZE_MAX as a length field (20 digits, within the digit-count cap) must not UB or
+// wrap. The overflow-guard in field() caps the multiplication; even if the value itself
+// does not trigger the multiply guard (SIZE_MAX accumulates cleanly digit by digit),
+// the subsequent "len > s_.size() - start" bounds check catches it because the actual
+// string is tiny — no OOB access, no wraparound, clean rejection.
+static void testOverflowExactSizeMax() {
+    // 18446744073709551615 = SIZE_MAX on 64-bit. 20 digits: within the digit cap, but the
+    // trailing bounds check rejects it because the wire string is far smaller than SIZE_MAX.
+    const std::string wire = std::string("rsassign1") + "18446744073709551615:X";
+    CHECK(!decodeAssignmentRequest(wire).has_value());
+}
+
+int main() {
+    testRoundTrip();
+    testRoundTripPoolAndZeroGeneration();
+    testRoundTripAdversarialIds();
+    testRoundTripEmptyFields();
+    testLargeGeneration();
+    testMalformedParse();
+    testTrailingGarbageRejected();
+    testOverflowFieldLength();
+    testOverflowFieldInt64();
+    testOverflowExactSizeMax();
+
+    if (g_fail == 0) std::printf("All tests passed.\n");
+    return g_fail ? 1 : 0;
+}

tests/test_bank_model.cpp

@@ -36,6 +36,8 @@ static Sample fullSample(const std::string& seed) {
     s.captureTimeSigNum = 6;    // L7 F1 meter stamp (non-4/4 to prove it round-trips)
     s.captureTimeSigDenom = 8;
     s.key = "F#m";
+    s.rootNote = 60;                 // Phase S seam field (present)
+    s.loop = LoopPoints{4096, 65536}; // Phase S seam field (present)
     s.levels = {-0.3, -12.7, -14.2};
     s.clipped = true;
     s.tier = Tier::Archive;
@@ -86,11 +88,18 @@ static void testFullFieldRoundTrip() {
         CHECK(minMeter && minMeter->captureTimeSigNum == 0 && minMeter->captureTimeSigDenom == 0);
         CHECK(full && full->provenance.has_value());
         CHECK(full && full->provenance->fxChainSnapshot == "<FXCHAIN\n  BYPASS 0 0 0\n>");
+        // Phase S seam fields survive round-trip exactly.
+        CHECK(full && full->rootNote.has_value() && *full->rootNote == 60);
+        CHECK(full && full->loop.has_value());
+        CHECK(full && full->loop && full->loop->start == 4096 && full->loop->end == 65536);
 
         const Sample* min = back->query("min-b");
         CHECK(min && !min->key.has_value());
         CHECK(min && !min->provenance.has_value());
         CHECK(min && min->trackGuids.empty());
+        // Seam fields absent on the minimal sample and stay absent.
+        CHECK(min && !min->rootNote.has_value());
+        CHECK(min && !min->loop.has_value());
     }
 }
 
@@ -417,6 +426,128 @@ static void testEnumRangeValidation() {
     CHECK(!r2.has_value());
 }
 
+// S2 test case 2: a legacy Sample JSON — written before the Phase S seam fields
+// existed, so it has NO "rootNote" or "loop" keys at all — parses to clean empty
+// optionals (no loss, no migration) and re-serializes without inventing values.
+// (The parser's forward-compat unknown-key skipping is what makes the reverse case
+// — new keys ignored by an old parser — safe too; here we test old-JSON→new-parser.)
+static void testLegacyJsonDefaults() {
+    const char* legacy =
+        "{\"samples\":[{\"id\":\"leg1\",\"relativePath\":\"bank/leg.wav\","
+        "\"displayName\":\"legacy\","
+        "\"sourceMode\":0,\"sourceRange\":{\"startSeconds\":1.5,\"endSeconds\":2.5,"
+        "\"startPpq\":0.0,\"endPpq\":0.0},\"trackGuids\":[],"
+        "\"wetDry\":1.0,\"channelCount\":2,\"sampleRate\":48000,"
+        "\"lengthSeconds\":1.0,\"lengthBeats\":0.0,\"captureTempo\":120.0,"
+        "\"key\":null,\"levels\":{\"peakDb\":0.0,\"rmsDb\":0.0,\"lufs\":0.0},"
+        "\"clipped\":false,\"tier\":0,\"contentHash\":\"h-leg1\","
+        "\"provenance\":null,\"createdTimestamp\":0}]}";
+    auto r = BankIndex::deserialize(legacy);
+    CHECK(r.has_value());
+    if (r) {
+        const Sample* s = r->query("leg1");
+        CHECK(s != nullptr);
+        CHECK(s && !s->rootNote.has_value());  // clean default, not a guessed value
+        CHECK(s && !s->loop.has_value());
+
+        // Re-serialize is lossless: parsing it again yields an equal index. This
+        // proves the absent fields did not silently gain values on the way out.
+        std::string out = r->serialize();
+        auto again = BankIndex::deserialize(out);
+        CHECK(again.has_value());
+        CHECK(again && *again == *r);
+        if (again) {
+            const Sample* s2 = again->query("leg1");
+            CHECK(s2 && !s2->rootNote.has_value());
+            CHECK(s2 && !s2->loop.has_value());
+        }
+    }
+}
+
+// S2 test case 4: boundary values for the seam fields are representable and
+// round-trip. rootNote 0 and 127 (the MIDI edges); loopStart == loopEnd (a valid
+// zero-length marker); a loop whose end sits at the file's last frame. Also asserts
+// the deserialize-boundary validation rules reject out-of-range input rather than
+// storing a bogus value.
+static void testSeamFieldBoundaries() {
+    // rootNote at both MIDI edges + equal-and-end-anchored loop points round-trip.
+    BankIndex idx;
+    Sample lo = minimalSample("lo"); lo.contentHash = "h-lo";
+    lo.rootNote = 0;
+    lo.loop = LoopPoints{0, 0};            // zero-length marker at frame 0
+    Sample hi = minimalSample("hi"); hi.contentHash = "h-hi";
+    hi.rootNote = 127;
+    hi.loop = LoopPoints{100, 100};        // start == end elsewhere
+    Sample end = minimalSample("end"); end.contentHash = "h-end";
+    end.loop = LoopPoints{0, 9223372036854775807LL};  // end at max int64 frame
+    CHECK(idx.add(lo) == AddResult::Added);
+    CHECK(idx.add(hi) == AddResult::Added);
+    CHECK(idx.add(end) == AddResult::Added);
+
+    auto back = BankIndex::deserialize(idx.serialize());
+    CHECK(back.has_value());
+    CHECK(back && *back == idx);
+    if (back) {
+        CHECK(back->query("min-lo")->rootNote == 0);
+        CHECK(back->query("min-hi")->rootNote == 127);
+        // Named local: a brace-init with a comma inside CHECK(...) would be parsed
+        // as two macro arguments by the preprocessor.
+        const LoopPoints zeroLen{0, 0};
+        CHECK(back->query("min-lo")->loop == zeroLen);
+        CHECK(back->query("min-end")->loop->end == 9223372036854775807LL);
+    }
+
+    // Validation rule (chosen for this design, surfaced in the handoff):
+    //   rootNote must be 0..127; loop must satisfy 0 <= start <= end.
+    // Out-of-range input is rejected at the deserialize boundary (nullopt), mirroring
+    // the existing enum-range and integer-overflow rejections — never clamped.
+    const char* head =
+        "{\"samples\":[{\"id\":\"bad\",\"relativePath\":\"bank/b.wav\","
+        "\"displayName\":\"\",\"sourceMode\":0,"
+        "\"sourceRange\":{\"startSeconds\":0.0,\"endSeconds\":0.0,"
+        "\"startPpq\":0.0,\"endPpq\":0.0},\"trackGuids\":[],"
+        "\"wetDry\":1.0,\"channelCount\":1,\"sampleRate\":44100,"
+        "\"lengthSeconds\":0.0,\"lengthBeats\":0.0,\"captureTempo\":0.0,"
+        "\"key\":null,";
+    const char* tail =
+        "\"levels\":{\"peakDb\":0.0,\"rmsDb\":0.0,\"lufs\":0.0},"
+        "\"clipped\":false,\"tier\":0,\"contentHash\":\"h-bad\","
+        "\"provenance\":null,\"createdTimestamp\":0}]}";
+
+    CHECK(!BankIndex::deserialize(std::string(head) + "\"rootNote\":128," + tail).has_value());
+    CHECK(!BankIndex::deserialize(std::string(head) + "\"rootNote\":-1," + tail).has_value());
+    CHECK(!BankIndex::deserialize(
+        std::string(head) + "\"loop\":{\"start\":10,\"end\":5}," + tail).has_value());  // start > end
+    CHECK(!BankIndex::deserialize(
+        std::string(head) + "\"loop\":{\"start\":-1,\"end\":5}," + tail).has_value());  // negative start
+}
+
+// S2 test case 3: the seam-field addition is purely additive — dedup-by-hash, tier
+// moves/filtering, and BankIndex ordering are byte-for-byte unchanged by the
+// presence (or absence) of rootNote/loop. Two samples differing ONLY in seam fields
+// but sharing a content hash still collapse; a seam-populated sample tiers exactly
+// like any other.
+static void testSeamFieldsAdditiveInvariant() {
+    BankIndex idx;
+    Sample a = fullSample("z");   // has rootNote + loop populated
+    CHECK(idx.add(a) == AddResult::Added);
+
+    // Same hash, seam fields cleared — dedup keys off contentHash only, so this
+    // still collapses. Seam fields do NOT enter the dedup identity.
+    Sample dup = fullSample("z2");
+    dup.contentHash = a.contentHash;
+    dup.rootNote.reset();
+    dup.loop.reset();
+    CHECK(idx.add(dup) == AddResult::Collapsed);
+    CHECK(idx.size() == 1);
+
+    // Tier move on a seam-populated sample behaves exactly as before.
+    CHECK(idx.query("id-z")->tier == Tier::Archive);
+    CHECK(idx.moveTier("id-z", Tier::Scratch));
+    CHECK(idx.query("id-z")->tier == Tier::Scratch);
+    CHECK(idx.query("id-z")->rootNote == 60);  // move did not disturb seam fields
+}
+
 int main() {
     testFullFieldRoundTrip();
     testDedupByHash();
@@ -430,6 +561,9 @@ int main() {
     testUnicodeEscapeDecoding();
     testIntegerOverflow();
     testEnumRangeValidation();
+    testLegacyJsonDefaults();
+    testSeamFieldBoundaries();
+    testSeamFieldsAdditiveInvariant();
 
     if (g_fail == 0) std::printf("All tests passed.\n");
     return g_fail ? 1 : 0;

tests/test_bank_sync.cpp

@@ -0,0 +1,203 @@
+// Standalone tests for reasampler::vst::bank_sync — no REAPER, no VST3, no framework.
+// The S9 bank-generation change-detection + the S8 assignment-request consume DECISION
+// (the yes/no maths the instrument's off-audio-thread poll runs). The shell owns the
+// cadence + side effects; this proves the decision rules without a host.
+//
+// Covers: parseBankGeneration (absent/malformed/overflow/negative/valid whole-string),
+// formatBankGeneration round-trip, bankGenerationChanged, and every consumeDecision rule
+// (no request / not-newer / non-target / unresolvable-drop / apply), asserting both the
+// apply flag AND the advanced-marker value so a stale request is never re-evaluated.
+
+#include "../src/vst/bank_sync.h"
+
+#include <cstdint>
+#include <cstdio>
+#include <optional>
+#include <string>
+
+using namespace reasampler;
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// --- parseBankGeneration -----------------------------------------------------
+
+static void testParseAbsentAndMalformed() {
+    // Absent / empty -> generation 0 (the pre-S9 default; a project with no stamp).
+    CHECK(parseBankGeneration("") == 0);
+    CHECK(parseBankGeneration("") == kBankGenerationAbsent);
+    // Malformed -> 0, never a crash, never a partial value.
+    CHECK(parseBankGeneration("abc") == 0);
+    CHECK(parseBankGeneration("12x") == 0);     // trailing garbage rejects whole
+    CHECK(parseBankGeneration("x12") == 0);     // leading garbage
+    CHECK(parseBankGeneration("1 2") == 0);     // embedded space
+    CHECK(parseBankGeneration("+5") == 0);      // sign rejected
+    CHECK(parseBankGeneration("-5") == 0);      // negative rejected
+    CHECK(parseBankGeneration(" 5") == 0);      // leading space
+    CHECK(parseBankGeneration("5.0") == 0);     // decimal point
+}
+
+static void testParseValid() {
+    CHECK(parseBankGeneration("0") == 0);
+    CHECK(parseBankGeneration("1") == 1);
+    CHECK(parseBankGeneration("42") == 42);
+    CHECK(parseBankGeneration("00042") == 42);  // leading zeros are still digits -> 42
+    CHECK(parseBankGeneration("9007199254740993") == 9007199254740993LL);  // > 2^53
+}
+
+static void testParseOverflow() {
+    // A 19-digit int64-max is fine; anything past it rejects to 0 (never wraps).
+    CHECK(parseBankGeneration("9223372036854775807") == 9223372036854775807LL);  // INT64_MAX
+    CHECK(parseBankGeneration("9223372036854775808") == 0);  // INT64_MAX + 1 -> reject
+    CHECK(parseBankGeneration("99999999999999999999") == 0);  // 20 nines -> reject
+}
+
+static void testFormatRoundTrip() {
+    CHECK(formatBankGeneration(0) == "0");
+    CHECK(formatBankGeneration(1) == "1");
+    CHECK(formatBankGeneration(123456789) == "123456789");
+    // Round-trips: format then parse yields the original for the valid domain.
+    for (std::int64_t g : {std::int64_t{0}, std::int64_t{1}, std::int64_t{7},
+                           std::int64_t{9007199254740993LL}}) {
+        CHECK(parseBankGeneration(formatBankGeneration(g)) == g);
+    }
+}
+
+// --- bankGenerationChanged ---------------------------------------------------
+
+static void testGenerationChanged() {
+    CHECK(!bankGenerationChanged(0, 0));   // pre-S9 idle: no stamp seen, no stamp now
+    CHECK(bankGenerationChanged(0, 1));    // first bump after a pre-S9 baseline -> change
+    CHECK(bankGenerationChanged(5, 6));    // normal increment
+    CHECK(!bankGenerationChanged(6, 6));   // idle poll (coalesced): no change
+    CHECK(bankGenerationChanged(6, 3));    // a project switch/reload can lower it -> change
+}
+
+// --- consumeDecision ---------------------------------------------------------
+
+static AssignmentRequest makeReq(const std::string& bank, const std::string& sample,
+                                 std::int64_t gen) {
+    AssignmentRequest r;
+    r.bankId = bank;
+    r.sampleId = sample;
+    r.generation = gen;
+    return r;
+}
+
+// Rule 1a: no pending request -> nothing to do, marker unchanged.
+static void testNoRequest() {
+    const auto d = consumeDecision(std::nullopt, /*lastConsumed*/ 5,
+                                   /*resolves*/ true, /*isFocusedTarget*/ true);
+    CHECK(!d.apply);
+    CHECK(d.consumedGeneration == 5);  // marker held
+}
+
+// Rule 1b: a request no newer than what we already consumed (re-open case) -> no re-apply.
+static void testNotNewerNotReapplied() {
+    // The persisted marker equals the request generation: the user already got this assign,
+    // possibly changed away from it. It MUST NOT re-apply on re-open.
+    const auto same = consumeDecision(makeReq("b", "s", 100), 100, true, true);
+    CHECK(!same.apply);
+    CHECK(same.consumedGeneration == 100);  // unchanged
+    // An older request (a stale value lingering) is likewise ignored.
+    const auto older = consumeDecision(makeReq("b", "s", 90), 100, true, true);
+    CHECK(!older.apply);
+    CHECK(older.consumedGeneration == 100);
+}
+
+// Rule 2: a NEW request but this instance is not the target -> do not apply AND do not
+// advance the marker (must stay eligible if focus later lands here — no thundering herd).
+static void testNonTargetStaysEligible() {
+    const auto d = consumeDecision(makeReq("b", "s", 200), /*lastConsumed*/ 100,
+                                   /*resolves*/ true, /*isFocusedTarget*/ false);
+    CHECK(!d.apply);
+    CHECK(d.consumedGeneration == 100);  // marker NOT advanced -> still eligible later
+}
+
+// Rule 3: a NEW request, target, but unresolvable -> DROP silently. Marker advances so it
+// is never re-evaluated, but no selection change (assignment_request.h reader requirement).
+static void testUnresolvableDroppedSilently() {
+    const auto d = consumeDecision(makeReq("b", "deleted-sample", 200),
+                                   /*lastConsumed*/ 100, /*resolves*/ false,
+                                   /*isFocusedTarget*/ true);
+    CHECK(!d.apply);                       // no selection change
+    CHECK(d.consumedGeneration == 200);    // consumed-as-seen: never re-evaluated
+    CHECK(d.sampleId.empty());             // nothing to apply
+}
+
+// Rule 4: a NEW request, target, resolvable -> APPLY selection + advance the marker.
+static void testAppliedWhenNewTargetResolvable() {
+    const auto d = consumeDecision(makeReq("bank-7", "cap-42", 200),
+                                   /*lastConsumed*/ 100, /*resolves*/ true,
+                                   /*isFocusedTarget*/ true);
+    CHECK(d.apply);
+    CHECK(d.bankId == "bank-7");
+    CHECK(d.sampleId == "cap-42");
+    CHECK(d.consumedGeneration == 200);
+}
+
+// Re-assigning the SAME sample id under a NEW generation must re-apply (the generation is
+// the disambiguator; a recapture/re-drop of the same id is a fresh assign, not a no-op).
+static void testSameIdNewGenerationReapplies() {
+    // First consume at gen 100.
+    const auto first = consumeDecision(makeReq("b", "s", 100), 50, true, true);
+    CHECK(first.apply);
+    CHECK(first.consumedGeneration == 100);
+    // Same id, higher generation, marker now at 100 -> applies again.
+    const auto second = consumeDecision(makeReq("b", "s", 150), 100, true, true);
+    CHECK(second.apply);
+    CHECK(second.sampleId == "s");
+    CHECK(second.consumedGeneration == 150);
+}
+
+// A fresh instance (lastConsumed == 0) applies a first assign — the default marker must not
+// swallow the first request.
+static void testFreshInstanceAppliesFirst() {
+    const auto d = consumeDecision(makeReq("b", "s", 1), 0, true, true);
+    CHECK(d.apply);
+    CHECK(d.consumedGeneration == 1);
+}
+
+// Re-import / dedup-collapse path: the extension ingests a sample that already exists in
+// the bank (dedup collapse: the bank_generation counter does NOT advance because no new
+// sample was added), but a new assign_request is still written with a HIGHER assign
+// generation (the ingest disambiguator, independent of bank_generation).
+//
+// The consumeDecision must apply the request — its own generation is the "is this new?"
+// discriminator, and it is strictly greater than lastConsumed. bank_generation does not
+// enter consumeDecision at all; this test proves the two counters are fully independent.
+static void testDedupCollapseAssignAppliesWhenBankGenerationUnchanged() {
+    // Simulate: bank_generation is 5 both before and after the dedup ingest (unchanged).
+    // The assign_request generation is 300 (new; lastConsumed was 200 from the prior assign).
+    // The existing sample resolves (it is in the bank — dedup kept it there).
+    const auto d = consumeDecision(makeReq("pool", "existing-sample-id", 300),
+                                   /*lastConsumed*/ 200, /*resolves*/ true,
+                                   /*isFocusedTarget*/ true);
+    CHECK(d.apply);
+    CHECK(d.bankId == "pool");
+    CHECK(d.sampleId == "existing-sample-id");
+    CHECK(d.consumedGeneration == 300);  // marker advanced to the new assign generation
+    // bank_generation (5) is not a parameter here — this test documents its absence from
+    // consumeDecision: only the assign_request's own generation drives the consume decision.
+}
+
+int main() {
+    testParseAbsentAndMalformed();
+    testParseValid();
+    testParseOverflow();
+    testFormatRoundTrip();
+    testGenerationChanged();
+    testNoRequest();
+    testNotNewerNotReapplied();
+    testNonTargetStaysEligible();
+    testUnresolvableDroppedSilently();
+    testAppliedWhenNewTargetResolvable();
+    testSameIdNewGenerationReapplies();
+    testFreshInstanceAppliesFirst();
+    testDedupCollapseAssignAppliesWhenBankGenerationUnchanged();
+
+    if (g_fail == 0) std::printf("All tests passed.\n");
+    return g_fail ? 1 : 0;
+}

tests/test_bridge_marshal.cpp

@@ -0,0 +1,56 @@
+// Standalone tests for reasampler::vst::bridge_marshal — no VST3, no REAPER, no test
+// framework. Same fast assert loop as the sibling pure tests: assert the REAPER
+// bridge-read marshalling (GetProjExtState result decode) directly, so the DAW-facing
+// shell only has to invoke the API.
+//
+// Covers: decodeGetProjExtState hit/absent/zero-return/empty-buffer (the stale-buffer
+// guard). The S1 spike's extractJsonStringField string-scan reader was retired in S4
+// (the instrument now parses the bank through the shared bank_book JSON path), so its
+// cases are gone with it.
+
+#include "../src/vst/bridge_marshal.h"
+
+#include <cstdio>
+
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// --- decodeGetProjExtState ----------------------------------------------------
+
+static void testDecodeHit() {
+    // REAPER reports a non-zero length and filled the buffer: that IS the value.
+    auto v = decodeGetProjExtState(5, "hello");
+    CHECK(v.has_value());
+    CHECK(v && *v == "hello");
+}
+
+static void testDecodeAbsentKey() {
+    // REAPER returns 0 for an absent key. Even if a caller passed a dirty buffer, the
+    // decoder must NOT surface it — the zero return means "no value".
+    auto v = decodeGetProjExtState(0, "stale-bytes-from-a-prior-read");
+    CHECK(!v.has_value());
+}
+
+static void testDecodeNegativeReturn() {
+    auto v = decodeGetProjExtState(-1, "whatever");
+    CHECK(!v.has_value());
+}
+
+static void testDecodeEmptyBuffer() {
+    // Positive return but empty buffer — treat as no value (defensive).
+    auto v = decodeGetProjExtState(3, "");
+    CHECK(!v.has_value());
+}
+
+int main() {
+    testDecodeHit();
+    testDecodeAbsentKey();
+    testDecodeNegativeReturn();
+    testDecodeEmptyBuffer();
+
+    if (g_fail == 0) std::printf("bridge_marshal: all tests passed\n");
+    return g_fail != 0;
+}

tests/test_browser_scroll.cpp

@@ -0,0 +1,179 @@
+// Standalone tests for reasampler::vst::browser_scroll — no VST3, no REAPER, no framework.
+// Same fast assert loop as the sibling pure editor tests: assert the S12 scroll-window +
+// scrollbar-thumb + type-to-filter-search geometry LAYERED over the S10 capture_browser.
+//
+// Covers: scrollContentHeight (ceil rows * card height, 0 for no cards); scrollMaxOffset (0
+// when content fits, else content-visible); clampScrollOffset pinning to [0,max]; visibleCardRange
+// windowing (top rows only, scrolled window, empty when scrolled past the end); scrolledCardCellRect
+// shifting a cell up by the offset; scrollThumbRect (empty when it fits, proportional height +
+// position, minimum height, at-max pins to the track bottom); thumbDragToOffset as the position
+// inverse (a full-track drag reaches max, round-trips); searchBoxRect; nameMatchesQuery
+// (case-insensitive substring, empty-query identity, no-match); filterNameIndices preserving order
+// and returning every index for an empty query.
+
+#include "../src/vst/browser_scroll.h"
+
+#include <cstdio>
+#include <string>
+#include <vector>
+
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// A layout wide enough for a few columns and tall enough to show a few rows.
+static BrowserLayout wideLayout() { return layoutBrowser(560, 300); }
+
+// --- content / max / clamp ----------------------------------------------------
+
+static void testContentHeight() {
+    const BrowserLayout L = wideLayout();
+    CHECK(scrollContentHeight(L, 0) == 0);
+    // One card -> one row -> one card height.
+    CHECK(scrollContentHeight(L, 1) == kBrowserCardHeight);
+    // columns+1 cards -> two rows.
+    CHECK(scrollContentHeight(L, L.columns + 1) == 2 * kBrowserCardHeight);
+    // Exactly `columns` cards -> one row.
+    CHECK(scrollContentHeight(L, L.columns) == kBrowserCardHeight);
+}
+
+static void testMaxOffsetFitsAndOverflows() {
+    const BrowserLayout L = wideLayout();
+    // A single row fits within the 300px area -> no scroll.
+    CHECK(scrollMaxOffset(L, L.columns) == 0);
+    // Many rows overflow -> max = content - gridHeight.
+    const int many = L.columns * 20;
+    const int expect = scrollContentHeight(L, many) - L.grid.height();
+    CHECK(scrollMaxOffset(L, many) == expect);
+    CHECK(expect > 0);
+}
+
+static void testClamp() {
+    const BrowserLayout L = wideLayout();
+    const int many = L.columns * 20;
+    const int maxOff = scrollMaxOffset(L, many);
+    CHECK(clampScrollOffset(L, many, -50) == 0);
+    CHECK(clampScrollOffset(L, many, maxOff + 500) == maxOff);
+    CHECK(clampScrollOffset(L, many, maxOff / 2) == maxOff / 2);
+}
+
+// --- visible window -----------------------------------------------------------
+
+static void testVisibleRangeTop() {
+    const BrowserLayout L = wideLayout();
+    const int many = L.columns * 20;
+    const VisibleRange vr = visibleCardRange(L, many, 0);
+    CHECK(vr.first == 0);
+    // At offset 0, the last visible row is the one containing (gridH-1).
+    const int expectedLastRow = (L.grid.height() - 1) / kBrowserCardHeight + 1;
+    CHECK(vr.last == expectedLastRow * L.columns);
+}
+
+static void testVisibleRangeScrolled() {
+    const BrowserLayout L = wideLayout();
+    const int many = L.columns * 20;
+    // Scroll one full card row down.
+    const VisibleRange vr = visibleCardRange(L, many, kBrowserCardHeight);
+    CHECK(vr.first == L.columns);  // the first row scrolled off the top
+}
+
+static void testVisibleRangeEmptyWhenNoCards() {
+    const BrowserLayout L = wideLayout();
+    const VisibleRange vr = visibleCardRange(L, 0, 0);
+    CHECK(vr.first == 0 && vr.last == 0);
+}
+
+static void testScrolledCellShiftsUp() {
+    const BrowserLayout L = wideLayout();
+    const Rect base = cardCellRect(L, 3);
+    const Rect shifted = scrolledCardCellRect(L, 3, 40);
+    CHECK(shifted.top == base.top - 40);
+    CHECK(shifted.bottom == base.bottom - 40);
+    CHECK(shifted.left == base.left);
+}
+
+// --- scrollbar thumb ----------------------------------------------------------
+
+static void testThumbEmptyWhenFits() {
+    const BrowserLayout L = wideLayout();
+    CHECK(scrollThumbRect(L, L.columns, 0).height() == 0);  // one row fits -> no thumb
+}
+
+static void testThumbProportionalAndClamped() {
+    const BrowserLayout L = wideLayout();
+    const int many = L.columns * 20;
+    const Rect atTop = scrollThumbRect(L, many, 0);
+    CHECK(atTop.height() > 0);
+    CHECK(atTop.top == L.grid.top);  // at offset 0 the thumb starts at the track top
+    CHECK(atTop.width() == kScrollbarWidth);
+    CHECK(atTop.right == L.grid.right);
+    // At max offset, the thumb bottom reaches the grid bottom (pinned to the end).
+    const int maxOff = scrollMaxOffset(L, many);
+    const Rect atMax = scrollThumbRect(L, many, maxOff);
+    CHECK(atMax.bottom == L.grid.top + L.grid.height());
+}
+
+static void testThumbDragIsInverse() {
+    const BrowserLayout L = wideLayout();
+    const int many = L.columns * 20;
+    const int maxOff = scrollMaxOffset(L, many);
+    // A zero drag holds the start offset.
+    CHECK(thumbDragToOffset(L, many, 0, 0) == 0);
+    // A large positive drag pins to max; a large negative drag pins to 0.
+    CHECK(thumbDragToOffset(L, many, 0, 100000) == maxOff);
+    CHECK(thumbDragToOffset(L, many, maxOff, -100000) == 0);
+    // Dragging the thumb by the whole track span from top reaches (near) max.
+    const Rect thumb = scrollThumbRect(L, many, 0);
+    const int trackSpan = L.grid.height() - thumb.height();
+    const int off = thumbDragToOffset(L, many, 0, trackSpan);
+    CHECK(off >= maxOff - 2 && off <= maxOff);
+}
+
+// --- search -------------------------------------------------------------------
+
+static void testSearchBoxRect() {
+    const Rect r = searchBoxRect(200);
+    CHECK(r.left == 0 && r.top == 0 && r.right == 200 && r.height() == kSearchBoxHeight);
+    CHECK(searchBoxRect(0).width() == 0);
+}
+
+static void testNameMatch() {
+    CHECK(nameMatchesQuery("Kick Drum 01", ""));         // empty query matches all
+    CHECK(nameMatchesQuery("Kick Drum 01", "drum"));      // case-insensitive substring
+    CHECK(nameMatchesQuery("Kick Drum 01", "KICK"));
+    CHECK(!nameMatchesQuery("Kick Drum 01", "snare"));
+    CHECK(!nameMatchesQuery("ab", "abc"));                // query longer than name
+}
+
+static void testFilterIndices() {
+    std::vector<std::string> names{"Kick", "Snare", "Kick Sub", "Hat"};
+    // Empty query -> every index, in order.
+    const std::vector<int> all = filterNameIndices(names, "");
+    CHECK(all.size() == 4 && all[0] == 0 && all[3] == 3);
+    // "kick" -> indices 0 and 2, order preserved.
+    const std::vector<int> kicks = filterNameIndices(names, "kick");
+    CHECK(kicks.size() == 2 && kicks[0] == 0 && kicks[1] == 2);
+    // No match -> empty.
+    CHECK(filterNameIndices(names, "zzz").empty());
+}
+
+int main() {
+    testContentHeight();
+    testMaxOffsetFitsAndOverflows();
+    testClamp();
+    testVisibleRangeTop();
+    testVisibleRangeScrolled();
+    testVisibleRangeEmptyWhenNoCards();
+    testScrolledCellShiftsUp();
+    testThumbEmptyWhenFits();
+    testThumbProportionalAndClamped();
+    testThumbDragIsInverse();
+    testSearchBoxRect();
+    testNameMatch();
+    testFilterIndices();
+
+    if (g_fail == 0) std::printf("browser_scroll: all tests passed\n");
+    return g_fail != 0;
+}

tests/test_capture_browser.cpp

@@ -0,0 +1,203 @@
+// Standalone tests for reasampler::vst::capture_browser — no VST3, no REAPER, no framework.
+// Same fast assert loop as the sibling pure tests (embed_strip / editor_geometry): assert
+// the capture-first browser's card-grid + bank-filter-tab layout and hit-testing directly.
+//
+// Covers: layoutBrowser splitting an area into the tab strip + card grid and deriving the
+// column count; a tiny/zero area (no inversion, columns >= 1); cardCellRect / cardContentRect
+// / cardThumbnailRect / cardLabelRect tiling row-major across columns with the gutter inset
+// and the thumbnail band above the label; cardHitTest landing on the card content (and MISSING
+// in the inter-card gutter, past the last card, and on the tab strip); filterTabRect dividing
+// the strip into equal segments with the last tab absorbing the remainder; filterTabHitTest
+// hitting each tab and missing off-strip.
+
+#include "../src/vst/capture_browser.h"
+
+#include <cstdio>
+
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// --- layoutBrowser ------------------------------------------------------------
+
+static void testLayoutNormalArea() {
+    // Wide enough for several columns of the fixed-width card.
+    const BrowserLayout L = layoutBrowser(560, 300);
+    CHECK(L.tabStrip.left == 0 && L.tabStrip.top == 0 && L.tabStrip.right == 560);
+    CHECK(L.tabStrip.height() == kBrowserTabHeight);
+    // The grid starts right below the tab strip and fills the rest, contiguous.
+    CHECK(L.grid.top == L.tabStrip.bottom);
+    CHECK(L.grid.bottom == 300 && L.grid.right == 560);
+    // columns = grid.width() / cardWidth (>= 1).
+    CHECK(L.columns == 560 / kBrowserCardWidth);
+    CHECK(L.columns >= 1);
+}
+
+static void testLayoutNarrowAreaSingleColumn() {
+    // Narrower than one card: still a single column, no inversion.
+    const BrowserLayout L = layoutBrowser(kBrowserCardWidth - 10, 200);
+    CHECK(L.columns == 1);
+    CHECK(L.grid.width() >= 0);
+    CHECK(L.tabStrip.height() == kBrowserTabHeight);
+}
+
+static void testLayoutZeroArea() {
+    const BrowserLayout L = layoutBrowser(0, 0);
+    CHECK(L.tabStrip.width() == 0 && L.tabStrip.height() == 0);
+    CHECK(L.grid.width() == 0);
+    CHECK(L.columns == 1);  // never zero (avoids a divide-by-zero in card layout)
+}
+
+static void testLayoutTinyHeightClampsTabStrip() {
+    // A height below the tab band: the tab strip clamps to the area, the grid is empty.
+    const BrowserLayout L = layoutBrowser(560, kBrowserTabHeight - 6);
+    CHECK(L.tabStrip.height() == kBrowserTabHeight - 6);
+    CHECK(L.grid.height() <= 0);  // no room left for cards
+}
+
+// --- card rects ---------------------------------------------------------------
+
+static void testCardCellsTileRowMajor() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    const int cols = L.columns;
+    // Card 0 is top-left of the grid.
+    const Rect c0 = cardCellRect(L, 0);
+    CHECK(c0.left == L.grid.left && c0.top == L.grid.top);
+    CHECK(c0.width() == kBrowserCardWidth && c0.height() == kBrowserCardHeight);
+    // Card 1 is one card-width to the right, same row.
+    const Rect c1 = cardCellRect(L, 1);
+    CHECK(c1.left == L.grid.left + kBrowserCardWidth);
+    CHECK(c1.top == c0.top);
+    // The first card of the SECOND row wraps back to the left, one card-height down.
+    const Rect wrap = cardCellRect(L, cols);
+    CHECK(wrap.left == L.grid.left);
+    CHECK(wrap.top == L.grid.top + kBrowserCardHeight);
+}
+
+static void testCardCellNegativeIndex() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    const Rect r = cardCellRect(L, -1);
+    CHECK(r.left == 0 && r.top == 0 && r.right == 0 && r.bottom == 0);
+}
+
+static void testCardContentInsetByGutter() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    const Rect cell = cardCellRect(L, 0);
+    const Rect content = cardContentRect(L, 0);
+    CHECK(content.left == cell.left + kBrowserCardGutter);
+    CHECK(content.top == cell.top + kBrowserCardGutter);
+    CHECK(content.right == cell.right - kBrowserCardGutter);
+    CHECK(content.bottom == cell.bottom - kBrowserCardGutter);
+}
+
+static void testThumbnailAboveLabel() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    const Rect content = cardContentRect(L, 0);
+    const Rect thumb = cardThumbnailRect(L, 0);
+    const Rect label = cardLabelRect(L, 0);
+    // Thumbnail is the top band of the content; the label is the remainder below it, contiguous.
+    CHECK(thumb.left == content.left && thumb.right == content.right);
+    CHECK(thumb.top == content.top);
+    CHECK(thumb.height() == kBrowserThumbHeight);
+    CHECK(label.top == thumb.bottom);
+    CHECK(label.bottom == content.bottom);
+    CHECK(label.left == content.left && label.right == content.right);
+}
+
+// --- cardHitTest --------------------------------------------------------------
+
+static void testCardHitCenterOfCard() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    const Rect content = cardContentRect(L, 3);
+    const int cx = content.left + content.width() / 2;
+    const int cy = content.top + content.height() / 2;
+    CHECK(cardHitTest(L, 12, cx, cy) == 3);
+}
+
+static void testCardHitMissesGutter() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    // A point in the gutter between the content and the cell edge (top-left corner of cell 0)
+    // is a miss — only the card CONTENT counts.
+    const Rect cell = cardCellRect(L, 0);
+    CHECK(cardHitTest(L, 12, cell.left, cell.top) == -1);
+}
+
+static void testCardHitMissesPastLastCard() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    // Only 2 cards exist; a point on where card 5 WOULD be is a miss.
+    const Rect content = cardContentRect(L, 5);
+    const int cx = content.left + content.width() / 2;
+    const int cy = content.top + content.height() / 2;
+    CHECK(cardHitTest(L, 2, cx, cy) == -1);
+}
+
+static void testCardHitMissesTabStrip() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    CHECK(cardHitTest(L, 12, 10, L.tabStrip.top + 2) == -1);
+}
+
+static void testCardHitZeroCards() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    CHECK(cardHitTest(L, 0, 20, 40) == -1);
+}
+
+// --- filter tabs --------------------------------------------------------------
+
+static void testFilterTabsTileStrip() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    const int n = 4;  // "All" + 3 banks
+    const Rect t0 = filterTabRect(L, n, 0);
+    const Rect tLast = filterTabRect(L, n, n - 1);
+    CHECK(t0.left == L.tabStrip.left);
+    // Adjacent tabs share an exact edge (no gap).
+    CHECK(filterTabRect(L, n, 0).right == filterTabRect(L, n, 1).left);
+    CHECK(filterTabRect(L, n, 1).right == filterTabRect(L, n, 2).left);
+    // The last tab reaches the strip's right edge exactly (absorbs the remainder).
+    CHECK(tLast.right == L.tabStrip.right);
+    // All tabs share the strip's height.
+    CHECK(t0.top == L.tabStrip.top && t0.bottom == L.tabStrip.bottom);
+}
+
+static void testFilterTabOutOfRange() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    CHECK(filterTabRect(L, 3, -1).width() == 0);
+    CHECK(filterTabRect(L, 3, 3).width() == 0);
+    CHECK(filterTabRect(L, 0, 0).width() == 0);
+}
+
+static void testFilterTabHit() {
+    const BrowserLayout L = layoutBrowser(560, 300);
+    const int n = 3;
+    for (int i = 0; i < n; ++i) {
+        const Rect t = filterTabRect(L, n, i);
+        const int cx = t.left + t.width() / 2;
+        const int cy = t.top + t.height() / 2;
+        CHECK(filterTabHitTest(L, n, cx, cy) == i);
+    }
+    // Below the strip (in the grid) -> no tab.
+    CHECK(filterTabHitTest(L, n, 20, L.grid.top + 4) == -1);
+}
+
+int main() {
+    testLayoutNormalArea();
+    testLayoutNarrowAreaSingleColumn();
+    testLayoutZeroArea();
+    testLayoutTinyHeightClampsTabStrip();
+    testCardCellsTileRowMajor();
+    testCardCellNegativeIndex();
+    testCardContentInsetByGutter();
+    testThumbnailAboveLabel();
+    testCardHitCenterOfCard();
+    testCardHitMissesGutter();
+    testCardHitMissesPastLastCard();
+    testCardHitMissesTabStrip();
+    testCardHitZeroCards();
+    testFilterTabsTileStrip();
+    testFilterTabOutOfRange();
+    testFilterTabHit();
+
+    if (g_fail == 0) std::printf("capture_browser: all tests passed\n");
+    return g_fail != 0;
+}

tests/test_drag_out.cpp

@@ -84,6 +84,54 @@ static void testOffsetPanelRect() {
     CHECK(decideGesture(100, 19, p, s) == DragGesture::OsDrag);  // just above origin
 }
 
+// --- S17 InstrumentDrop gesture (single-capture over REAPER UI) ---------------
+//
+// M11 REGRESSION GUARD (load-bearing): every M11 case above uses DragState{true, true},
+// which leaves singleCapture=overReaperUi=false — so an M11-era payload outside the client
+// rect still decides OsDrag exactly as before. The tests above ARE the M11 non-regression
+// proof; these add the new middle case.
+
+// A SINGLE-capture drag that has left the panel but is still over REAPER's own UI is an
+// instrument drop (heading for a track's FX button), NOT an OS drag.
+static void testSingleCaptureOverReaperUiIsInstrumentDrop() {
+    DragState s{/*dragging=*/true, /*hasArmedSamples=*/true,
+                /*singleCapture=*/true, /*overReaperUi=*/true};
+    CHECK(decideGesture(500, 150, kPanel, s) == DragGesture::InstrumentDrop);  // right of panel
+    CHECK(decideGesture(-5, 150, kPanel, s) == DragGesture::InstrumentDrop);   // left of panel
+    CHECK(decideGesture(200, 400, kPanel, s) == DragGesture::InstrumentDrop);  // below
+}
+
+// InstrumentDrop is an OUTSIDE-only refinement: the same single-capture state INSIDE the
+// client rect is still the unchanged Internal bank-to-bank drag (invariant #4).
+static void testSingleCaptureInsidePanelStaysInternal() {
+    DragState s{true, true, /*singleCapture=*/true, /*overReaperUi=*/true};
+    CHECK(decideGesture(200, 150, kPanel, s) == DragGesture::Internal);
+}
+
+// A single-capture drag that has left REAPER ENTIRELY (overReaperUi=false) falls through to
+// OsDrag — the M11 OS drag-out to Explorer/another DAW, unchanged. This is the boundary
+// refinement's other half: leaving the client rect no longer immediately means OS-bound.
+static void testSingleCaptureOffReaperIsOsDrag() {
+    DragState s{true, true, /*singleCapture=*/true, /*overReaperUi=*/false};
+    CHECK(decideGesture(500, 150, kPanel, s) == DragGesture::OsDrag);
+}
+
+// A MULTI-capture drag over REAPER's UI is REJECTED for InstrumentDrop (the S17 open-question
+// lean): it is NOT a single instrument placement, so it falls through to OsDrag even while
+// over REAPER's UI — the multi-file drag-out is the natural gesture for a multi payload.
+static void testMultiCaptureOverReaperUiIsOsDrag() {
+    DragState s{true, true, /*singleCapture=*/false, /*overReaperUi=*/true};
+    CHECK(decideGesture(500, 150, kPanel, s) == DragGesture::OsDrag);
+}
+
+// Not-dragging / no-armed-samples still short-circuits to None regardless of the S17 fields.
+static void testS17FieldsIgnoredWhenNotDragging() {
+    CHECK(decideGesture(500, 150, kPanel,
+                        DragState{false, true, true, true}) == DragGesture::None);
+    CHECK(decideGesture(500, 150, kPanel,
+                        DragState{true, false, true, true}) == DragGesture::None);
+}
+
 // --- Path-list assembly -------------------------------------------------------
 
 static ResolvedSample ok(const std::string& p) { return ResolvedSample{p, true}; }
@@ -180,6 +228,12 @@ int main() {
     testReentryReturnsInternal();
     testOffsetPanelRect();
 
+    testSingleCaptureOverReaperUiIsInstrumentDrop();
+    testSingleCaptureInsidePanelStaysInternal();
+    testSingleCaptureOffReaperIsOsDrag();
+    testMultiCaptureOverReaperUiIsOsDrag();
+    testS17FieldsIgnoredWhenNotDragging();
+
     testSinglePath();
     testMultiPreservesOrder();
     testDedupeSamePath();

tests/test_editor_geometry.cpp

@@ -0,0 +1,337 @@
+// Standalone tests for reasampler::vst::editor_geometry — no VST3, no REAPER, no test
+// framework. Same fast assert loop as the sibling pure tests (mode_switch et al.):
+// assert the IPlugView LICE editor's layout math + hit-testing directly.
+//
+// Covers: contains() half-open convention + degenerate rects; layoutEditor regions on a
+// normal view (title band + button + canvas), a tiny view (button clamped to canvas,
+// never overhanging), and a zero view (all rects empty, no inversion); hitTest hitting
+// the button, missing on the title/canvas, missing outside the surface, and boundary
+// pixels; layout<->hit-test agreement (a click on the drawn button rect hits it).
+
+#include "../src/vst/editor_geometry.h"
+
+#include <cstdio>
+
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// --- contains() ---------------------------------------------------------------
+
+static void testContainsHalfOpen() {
+    Rect r{10, 20, 50, 40};  // [10,50) x [20,40)
+    CHECK(contains(r, 10, 20));     // top-left inclusive
+    CHECK(contains(r, 49, 39));     // bottom-right exclusive edge, inside
+    CHECK(!contains(r, 50, 30));    // right edge excluded
+    CHECK(!contains(r, 30, 40));    // bottom edge excluded
+    CHECK(!contains(r, 9, 30));     // left of rect
+    CHECK(!contains(r, 30, 19));    // above rect
+}
+
+static void testContainsDegenerate() {
+    CHECK(!contains(Rect{10, 10, 10, 20}, 10, 15));  // zero width
+    CHECK(!contains(Rect{10, 10, 20, 10}, 15, 10));  // zero height
+    CHECK(!contains(Rect{20, 10, 10, 20}, 15, 15));  // inverted (right < left)
+}
+
+// --- layoutEditor: normal view ------------------------------------------------
+
+static void testLayoutNormalView() {
+    // A comfortable 400x260 view: title band spans the top full width; canvas is the
+    // rest; button sits inside the canvas, inset by the margin.
+    const EditorLayout L = layoutEditor(400, 260);
+
+    CHECK(L.titleBar.left == 0 && L.titleBar.top == 0);
+    CHECK(L.titleBar.right == 400);
+    CHECK(L.titleBar.height() > 0 && L.titleBar.height() <= 260);
+
+    // Canvas begins right below the title bar and reaches the bottom-right.
+    CHECK(L.canvas.top == L.titleBar.bottom);
+    CHECK(L.canvas.right == 400 && L.canvas.bottom == 260);
+
+    // Button is inside the canvas (does not overhang any edge).
+    CHECK(L.button.left >= L.canvas.left);
+    CHECK(L.button.top >= L.canvas.top);
+    CHECK(L.button.right <= L.canvas.right);
+    CHECK(L.button.bottom <= L.canvas.bottom);
+    CHECK(L.button.width() > 0 && L.button.height() > 0);
+}
+
+// --- layoutEditor: tiny view (clamping) ---------------------------------------
+
+static void testLayoutTinyViewClampsButton() {
+    // A view narrower/shorter than the button's natural size: the button must clamp to
+    // the canvas and never produce an inverted or overhanging rect.
+    const EditorLayout L = layoutEditor(40, 40);
+    CHECK(L.button.right <= L.canvas.right);
+    CHECK(L.button.bottom <= L.canvas.bottom);
+    CHECK(L.button.right >= L.button.left);   // never inverted
+    CHECK(L.button.bottom >= L.button.top);
+    // Title bar clamps to the client height when the view is shorter than its height.
+    CHECK(L.titleBar.bottom <= 40);
+}
+
+// --- layoutEditor: zero view (all empty, no inversion) ------------------------
+
+static void testLayoutZeroView() {
+    const EditorLayout L = layoutEditor(0, 0);
+    CHECK(L.titleBar.width() <= 0 || L.titleBar.height() <= 0);
+    CHECK(L.canvas.width() <= 0 || L.canvas.height() <= 0);
+    // No rect is inverted.
+    CHECK(L.button.right >= L.button.left);
+    CHECK(L.button.bottom >= L.button.top);
+    CHECK(L.canvas.right >= L.canvas.left);
+    CHECK(L.canvas.bottom >= L.canvas.top);
+    // A click anywhere on an empty layout hits nothing.
+    CHECK(hitTest(L, 0, 0) == HitTarget::kNone);
+    CHECK(hitTest(L, 5, 5) == HitTarget::kNone);
+}
+
+// --- hitTest ------------------------------------------------------------------
+
+static void testHitTestButton() {
+    const EditorLayout L = layoutEditor(400, 260);
+    // Center of the button hits it.
+    const int cx = (L.button.left + L.button.right) / 2;
+    const int cy = (L.button.top + L.button.bottom) / 2;
+    CHECK(hitTest(L, cx, cy) == HitTarget::kButton);
+}
+
+static void testHitTestMissesNonButton() {
+    const EditorLayout L = layoutEditor(400, 260);
+    // Title bar is inert in the spike.
+    CHECK(hitTest(L, 200, L.titleBar.top + 1) == HitTarget::kNone);
+    // Empty canvas away from the button.
+    CHECK(hitTest(L, 380, 240) == HitTarget::kNone);
+    // Outside the surface entirely.
+    CHECK(hitTest(L, -5, -5) == HitTarget::kNone);
+    CHECK(hitTest(L, 500, 500) == HitTarget::kNone);
+}
+
+static void testHitTestButtonBoundary() {
+    const EditorLayout L = layoutEditor(400, 260);
+    // Top-left corner of the button is inclusive; the right/bottom edges are excluded.
+    CHECK(hitTest(L, L.button.left, L.button.top) == HitTarget::kButton);
+    CHECK(hitTest(L, L.button.right, L.button.top) == HitTarget::kNone);
+    CHECK(hitTest(L, L.button.left, L.button.bottom) == HitTarget::kNone);
+}
+
+// --- layout<->hit-test agreement ----------------------------------------------
+
+// Every pixel inside the drawn button rect must hit the button; this is the
+// load-bearing consistency invariant between what the shell draws and what it routes.
+static void testHitTestMatchesDrawnButton() {
+    const EditorLayout L = layoutEditor(320, 200);
+    for (int y = L.button.top; y < L.button.bottom; ++y) {
+        for (int x = L.button.left; x < L.button.right; ++x) {
+            CHECK(hitTest(L, x, y) == HitTarget::kButton);
+        }
+    }
+}
+
+// --- sample list (S4) ---------------------------------------------------------
+
+static void testSampleRowRectStacks() {
+    const EditorLayout L = layoutEditor(400, 260);
+    const Rect r0 = sampleRowRect(L, 0);
+    const Rect r1 = sampleRowRect(L, 1);
+    // Row 0 starts at the canvas top and spans its full width.
+    CHECK(r0.top == L.canvas.top);
+    CHECK(r0.left == L.canvas.left && r0.right == L.canvas.right);
+    CHECK(r0.height() == kSampleRowHeight);
+    // Row 1 sits directly below row 0 (no gap, no overlap).
+    CHECK(r1.top == r0.bottom);
+    CHECK(r1.height() == kSampleRowHeight);
+    // A negative index is an empty rect.
+    CHECK(sampleRowRect(L, -1).width() == 0 && sampleRowRect(L, -1).height() == 0);
+}
+
+static void testSampleRowHitTestMapsClickToRow() {
+    const EditorLayout L = layoutEditor(400, 260);
+    const int rows = 5;
+    // A click in the vertical middle of row 2 resolves to index 2.
+    const Rect r2 = sampleRowRect(L, 2);
+    const int midY = (r2.top + r2.bottom) / 2;
+    CHECK(sampleRowHitTest(L, rows, 200, midY) == 2);
+    // Row 0's top-left corner hits row 0.
+    const Rect r0 = sampleRowRect(L, 0);
+    CHECK(sampleRowHitTest(L, rows, r0.left, r0.top) == 0);
+}
+
+static void testSampleRowHitTestMisses() {
+    const EditorLayout L = layoutEditor(400, 260);
+    const int rows = 3;
+    // Above the first row (in the title bar) -> no row.
+    CHECK(sampleRowHitTest(L, rows, 200, L.titleBar.top) == -1);
+    // Below the last row -> no row.
+    const Rect last = sampleRowRect(L, rows - 1);
+    CHECK(sampleRowHitTest(L, rows, 200, last.bottom + 1) == -1);
+    // Left of the canvas -> no row.
+    CHECK(sampleRowHitTest(L, rows, L.canvas.left - 1, last.top) == -1);
+    // Zero rows -> always -1.
+    CHECK(sampleRowHitTest(L, 0, 200, L.canvas.top + 1) == -1);
+    // At or below canvas.bottom -> always -1, even if rowCount would cover that y.
+    // This guards paint<->hit-test agreement: sampleRowRect does not clamp to canvas,
+    // so without this clip a row that extends past canvas.bottom would hit-test but
+    // never be drawn (or vice versa).
+    CHECK(sampleRowHitTest(L, rows, 200, L.canvas.bottom) == -1);
+    // Use a large rowCount so index arithmetic would return a valid row without the
+    // canvas.bottom guard — proving the guard fires independently of rowCount.
+    const int bigRows = 1000;
+    CHECK(sampleRowHitTest(L, bigRows, 200, L.canvas.bottom) == -1);
+    CHECK(sampleRowHitTest(L, bigRows, 200, L.canvas.bottom + 5) == -1);
+}
+
+// The drawn-row <-> hit-test agreement: every pixel inside a row rect must resolve to
+// that row's index (the same load-bearing invariant as the button).
+static void testSampleRowHitTestMatchesDrawnRows() {
+    const EditorLayout L = layoutEditor(320, 200);
+    const int rows = 4;
+    for (int i = 0; i < rows; ++i) {
+        const Rect r = sampleRowRect(L, i);
+        if (r.top >= L.canvas.bottom) break;  // clipped rows aren't clickable targets
+        const int y = (r.top + r.bottom) / 2;
+        if (y >= L.canvas.bottom) continue;
+        CHECK(sampleRowHitTest(L, rows, r.left + 1, y) == i);
+    }
+}
+
+// --- keymap editor (S5 Tier-1 UI) --------------------------------------------
+
+static void testKeymapLayoutSplitsCanvas() {
+    const KeymapEditorLayout L = layoutKeymapEditor(600, 300);
+    // The left sample list and right zone panel partition the canvas with no overlap and
+    // no gap: the list's right edge is the panel's left edge.
+    CHECK(L.sampleList.left == L.base.canvas.left);
+    CHECK(L.sampleList.right == L.zonePanel.left);
+    CHECK(L.zonePanel.right == L.base.canvas.right);
+    CHECK(L.sampleList.top == L.base.canvas.top);
+    CHECK(L.zonePanel.top == L.base.canvas.top);
+    CHECK(L.sampleList.bottom == L.base.canvas.bottom);
+    CHECK(L.zonePanel.bottom == L.base.canvas.bottom);
+    CHECK(L.sampleList.width() > 0 && L.zonePanel.width() > 0);
+    // Add-Zone button caps the panel; zone rows stack below it.
+    CHECK(L.addZoneButton.top == L.zonePanel.top);
+    CHECK(L.addZoneButton.left == L.zonePanel.left && L.addZoneButton.right == L.zonePanel.right);
+    CHECK(L.zoneRowArea.top == L.addZoneButton.bottom);
+    CHECK(L.zoneRowArea.bottom == L.zonePanel.bottom);
+}
+
+static void checkNoInversion(const KeymapEditorLayout& L) {
+    CHECK(L.sampleList.right >= L.sampleList.left);
+    CHECK(L.zonePanel.right >= L.zonePanel.left);
+    CHECK(L.addZoneButton.right >= L.addZoneButton.left);
+    CHECK(L.addZoneButton.bottom >= L.addZoneButton.top);
+    CHECK(L.zoneRowArea.right >= L.zoneRowArea.left);
+    CHECK(L.zoneRowArea.bottom >= L.zoneRowArea.top);
+    // Regions stay within the client area.
+    CHECK(L.zonePanel.right <= L.base.canvas.right);
+}
+
+static void testKeymapLayoutTinyAndZeroNoInversion() {
+    checkNoInversion(layoutKeymapEditor(30, 30));
+    checkNoInversion(layoutKeymapEditor(0, 0));
+    // A click anywhere on a zero layout hits no zone and no Add button.
+    const KeymapEditorLayout Z = layoutKeymapEditor(0, 0);
+    CHECK(zoneHitTest(Z, 3, 0, 0).zoneIndex == -1);
+    CHECK(!addZoneHitTest(Z, 0, 0));
+}
+
+static void testKeymapSampleRowInLeftColumn() {
+    const KeymapEditorLayout L = layoutKeymapEditor(600, 300);
+    const Rect r0 = keymapSampleRowRect(L, 0);
+    // Rows live in the LEFT column (not the full canvas width).
+    CHECK(r0.left == L.sampleList.left && r0.right == L.sampleList.right);
+    CHECK(r0.right < L.base.canvas.right);  // strictly left of the zone panel
+    CHECK(r0.top == L.sampleList.top && r0.height() == kSampleRowHeight);
+    // Hit-test maps a left-column click to the row and rejects a click in the zone panel.
+    const int midY = (r0.top + r0.bottom) / 2;
+    CHECK(keymapSampleRowHitTest(L, 3, r0.left + 2, midY) == 0);
+    CHECK(keymapSampleRowHitTest(L, 3, L.zonePanel.left + 2, midY) == -1);
+}
+
+static void testAddZoneHitTest() {
+    const KeymapEditorLayout L = layoutKeymapEditor(600, 300);
+    const int cx = (L.addZoneButton.left + L.addZoneButton.right) / 2;
+    const int cy = (L.addZoneButton.top + L.addZoneButton.bottom) / 2;
+    CHECK(addZoneHitTest(L, cx, cy));
+    // A click in the zone-row area below the button is NOT the Add button.
+    CHECK(!addZoneHitTest(L, cx, L.zoneRowArea.top + 2));
+    // A click in the left list is NOT the Add button.
+    CHECK(!addZoneHitTest(L, L.sampleList.left + 2, L.sampleList.top + 2));
+}
+
+static void testZoneRowStacksAndSelects() {
+    const KeymapEditorLayout L = layoutKeymapEditor(600, 300);
+    const Rect z0 = zoneRowRect(L, 0);
+    const Rect z1 = zoneRowRect(L, 1);
+    CHECK(z0.top == L.zoneRowArea.top && z0.height() == kZoneRowHeight);
+    CHECK(z1.top == z0.bottom);  // stacked, no gap
+    CHECK(z0.left == L.zoneRowArea.left && z0.right == L.zoneRowArea.right);
+    // A click on the LABEL area (left part of a zone row) selects the zone with no field.
+    const int labelX = z0.left + 2;  // far left = label, not a control
+    const int midY = (z0.top + z0.bottom) / 2;
+    const ZoneHit h = zoneHitTest(L, 2, labelX, midY);
+    CHECK(h.zoneIndex == 0 && h.field == ZoneField::kZoneNone);
+}
+
+static void testZoneRowControlsMapToFields() {
+    const KeymapEditorLayout L = layoutKeymapEditor(600, 300);
+    const Rect row = zoneRowRect(L, 0);
+    const int midY = (row.top + row.bottom) / 2;
+    // The seven controls occupy the rightmost 7*kZoneCtrlWidth px, left-to-right:
+    // low-, low+, high-, high+, root-, root+, delete.
+    const int block = row.right - 7 * kZoneCtrlWidth;
+    const ZoneField expected[7] = {
+        ZoneField::kLowDown, ZoneField::kLowUp,  ZoneField::kHighDown,
+        ZoneField::kHighUp,  ZoneField::kRootDown, ZoneField::kRootUp,
+        ZoneField::kDelete,
+    };
+    for (int s = 0; s < 7; ++s) {
+        const int x = block + s * kZoneCtrlWidth + kZoneCtrlWidth / 2;  // center of slot s
+        const ZoneHit h = zoneHitTest(L, 1, x, midY);
+        CHECK(h.zoneIndex == 0);
+        CHECK(h.zoneIndex == 0 && h.field == expected[s]);
+    }
+}
+
+static void testZoneHitTestMisses() {
+    const KeymapEditorLayout L = layoutKeymapEditor(600, 300);
+    const Rect row = zoneRowRect(L, 0);
+    const int midY = (row.top + row.bottom) / 2;
+    // Zero zones -> always miss.
+    CHECK(zoneHitTest(L, 0, row.left + 2, midY).zoneIndex == -1);
+    // Below the last zone row -> miss.
+    const Rect last = zoneRowRect(L, 2);
+    CHECK(zoneHitTest(L, 3, row.left + 2, last.bottom + 1).zoneIndex == -1);
+    // Left of the zone panel (in the sample list) -> miss.
+    CHECK(zoneHitTest(L, 3, L.sampleList.left + 2, midY).zoneIndex == -1);
+}
+
+int main() {
+    testContainsHalfOpen();
+    testContainsDegenerate();
+    testLayoutNormalView();
+    testLayoutTinyViewClampsButton();
+    testLayoutZeroView();
+    testHitTestButton();
+    testHitTestMissesNonButton();
+    testHitTestButtonBoundary();
+    testHitTestMatchesDrawnButton();
+    testSampleRowRectStacks();
+    testSampleRowHitTestMapsClickToRow();
+    testSampleRowHitTestMisses();
+    testSampleRowHitTestMatchesDrawnRows();
+    testKeymapLayoutSplitsCanvas();
+    testKeymapLayoutTinyAndZeroNoInversion();
+    testKeymapSampleRowInLeftColumn();
+    testAddZoneHitTest();
+    testZoneRowStacksAndSelects();
+    testZoneRowControlsMapToFields();
+    testZoneHitTestMisses();
+
+    if (g_fail == 0) std::printf("editor_geometry: all tests passed\n");
+    return g_fail != 0;
+}

tests/test_embed_strip.cpp

@@ -0,0 +1,157 @@
+// Standalone tests for reasampler::vst::embed_strip — no VST3, no REAPER, no framework.
+// Same fast assert loop as the sibling pure tests (editor_geometry et al.): assert the
+// embedded TCP/MCP strip's layout math + zone hit-testing + level fill directly.
+//
+// Covers: layoutEmbed splitting a normal area into keymap + level band, a tiny area
+// (band yields to the keymap minimum, no inversion), and a zero area (all empty);
+// zoneSegmentRect mapping the 128-key span linearly, tiling adjacent zones seamlessly,
+// clamping out-of-range/inverted notes; zoneAtPoint hitting the covering zone, first-match
+// on overlap, missing on uncovered keys and off-band, and rejecting a null/empty list;
+// levelFillRect clamping 0..1 and its endpoints.
+
+#include "../src/vst/embed_strip.h"
+
+#include <cstdio>
+
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// --- layoutEmbed --------------------------------------------------------------
+
+static void testLayoutNormalArea() {
+    // A comfortable inline strip: keymap band on top, thin level band pinned to the bottom.
+    const EmbedLayout L = layoutEmbed(300, 40);
+    CHECK(L.keymap.left == 0 && L.keymap.top == 0 && L.keymap.right == 300);
+    CHECK(L.levelBand.left == 0 && L.levelBand.right == 300);
+    // Level band is the fixed height at the very bottom; keymap fills the rest, contiguous.
+    CHECK(L.levelBand.height() == kEmbedLevelBandHeight);
+    CHECK(L.levelBand.bottom == 40);
+    CHECK(L.keymap.bottom == L.levelBand.top);
+    CHECK(L.keymap.height() == 40 - kEmbedLevelBandHeight);
+}
+
+static void testLayoutTinyAreaKeepsKeymap() {
+    // A very short area: the level band must yield so the keymap keeps its minimum, and no
+    // rect inverts.
+    const EmbedLayout L = layoutEmbed(300, 8);
+    CHECK(L.keymap.height() >= 0);
+    CHECK(L.levelBand.height() >= 0);
+    CHECK(L.keymap.bottom == L.levelBand.top);
+    CHECK(L.levelBand.bottom == 8);
+    // The keymap is not starved below its floor when the area allows it.
+    CHECK(L.keymap.height() >= kEmbedKeymapMinHeight || 8 < kEmbedKeymapMinHeight);
+}
+
+static void testLayoutZeroArea() {
+    const EmbedLayout L = layoutEmbed(0, 0);
+    CHECK(L.keymap.width() <= 0 && L.keymap.height() <= 0);
+    CHECK(L.levelBand.width() <= 0 && L.levelBand.height() <= 0);
+    // Negative dimensions clamp to a zero-area, non-inverted rect.
+    const EmbedLayout N = layoutEmbed(-50, -50);
+    CHECK(N.keymap.right >= N.keymap.left && N.keymap.bottom >= N.keymap.top);
+}
+
+// --- zoneSegmentRect ----------------------------------------------------------
+
+static void testZoneSegmentFullSpan() {
+    // A zone covering the whole keyboard spans the entire keymap band width.
+    const EmbedLayout L = layoutEmbed(256, 40);
+    const Rect r = zoneSegmentRect(L, 0, 127);
+    CHECK(r.left == L.keymap.left);
+    CHECK(r.right == L.keymap.right);
+    CHECK(r.top == L.keymap.top && r.bottom == L.keymap.bottom);
+}
+
+static void testAdjacentZonesTileSeamlessly() {
+    // 256px band, 128 keys -> 2px/key. Zones 0..59 and 60..127 must abut with no gap or
+    // overlap: the low zone's right == the high zone's left.
+    const EmbedLayout L = layoutEmbed(256, 40);
+    const Rect lo = zoneSegmentRect(L, 0, 59);
+    const Rect hi = zoneSegmentRect(L, 60, 127);
+    CHECK(lo.left == L.keymap.left);
+    CHECK(hi.right == L.keymap.right);
+    CHECK(lo.right == hi.left);           // seamless tile — the load-bearing assertion
+    CHECK(lo.right == L.keymap.left + 60 * 2);  // 60 keys * 2px
+}
+
+static void testZoneSegmentClampsBadNotes() {
+    const EmbedLayout L = layoutEmbed(256, 40);
+    // Out-of-range notes clamp into the band; an inverted zone (low > high) collapses to a
+    // zero-or-positive-width rect, never inverts.
+    const Rect over = zoneSegmentRect(L, -10, 200);
+    CHECK(over.left == L.keymap.left && over.right == L.keymap.right);
+    const Rect inv = zoneSegmentRect(L, 100, 20);
+    CHECK(inv.right >= inv.left);
+}
+
+// --- zoneAtPoint --------------------------------------------------------------
+
+static void testZoneAtPointHits() {
+    const EmbedLayout L = layoutEmbed(256, 40);
+    const EmbedZone zones[2] = {{0, 59}, {60, 127}};
+    // A point inside the low zone's segment resolves to zone 0; inside the high zone, 1.
+    const Rect lo = zoneSegmentRect(L, 0, 59);
+    const Rect hi = zoneSegmentRect(L, 60, 127);
+    const int yMid = (L.keymap.top + L.keymap.bottom) / 2;
+    CHECK(zoneAtPoint(L, zones, 2, lo.left + 1, yMid) == 0);
+    CHECK(zoneAtPoint(L, zones, 2, hi.right - 1, yMid) == 1);
+}
+
+static void testZoneAtPointFirstMatchOnOverlap() {
+    const EmbedLayout L = layoutEmbed(256, 40);
+    // Two overlapping zones; the FIRST in order must win the contested keys.
+    const EmbedZone zones[2] = {{0, 127}, {40, 80}};
+    const int yMid = (L.keymap.top + L.keymap.bottom) / 2;
+    const Rect contested = zoneSegmentRect(L, 40, 80);
+    CHECK(zoneAtPoint(L, zones, 2, contested.left + 1, yMid) == 0);  // zone 0 wins
+}
+
+static void testZoneAtPointMisses() {
+    const EmbedLayout L = layoutEmbed(256, 40);
+    const EmbedZone zones[1] = {{60, 72}};  // a narrow zone; most keys uncovered
+    const int yMid = (L.keymap.top + L.keymap.bottom) / 2;
+    // A key left of the zone is uncovered -> -1.
+    CHECK(zoneAtPoint(L, zones, 1, L.keymap.left + 1, yMid) == -1);
+    // A point in the level band (below the keymap) is off the keymap -> -1.
+    CHECK(zoneAtPoint(L, zones, 1, L.levelBand.left + 4, L.levelBand.top) == -1);
+    // Empty / null list -> -1.
+    CHECK(zoneAtPoint(L, zones, 0, L.keymap.left + 1, yMid) == -1);
+    CHECK(zoneAtPoint(L, nullptr, 3, L.keymap.left + 1, yMid) == -1);
+}
+
+// --- levelFillRect ------------------------------------------------------------
+
+static void testLevelFillClamps() {
+    const EmbedLayout L = layoutEmbed(200, 40);
+    // Zero / negative -> empty.
+    CHECK(levelFillRect(L, 0.0).width() <= 0);
+    CHECK(levelFillRect(L, -1.0).width() <= 0);
+    // Full / over-full -> the whole band width.
+    CHECK(levelFillRect(L, 1.0).width() == L.levelBand.width());
+    CHECK(levelFillRect(L, 5.0).width() == L.levelBand.width());
+    // Half -> ~half the band, pinned to the band's left and vertical extent.
+    const Rect half = levelFillRect(L, 0.5);
+    CHECK(half.left == L.levelBand.left);
+    CHECK(half.top == L.levelBand.top && half.bottom == L.levelBand.bottom);
+    CHECK(half.width() == L.levelBand.width() / 2);
+}
+
+int main() {
+    testLayoutNormalArea();
+    testLayoutTinyAreaKeepsKeymap();
+    testLayoutZeroArea();
+    testZoneSegmentFullSpan();
+    testAdjacentZonesTileSeamlessly();
+    testZoneSegmentClampsBadNotes();
+    testZoneAtPointHits();
+    testZoneAtPointFirstMatchOnOverlap();
+    testZoneAtPointMisses();
+    testLevelFillClamps();
+
+    if (g_fail == 0) std::printf("embed_strip: all tests passed\n");
+    else std::printf("embed_strip: %d FAILED\n", g_fail);
+    return g_fail == 0 ? 0 : 1;
+}

tests/test_instrument_drop.cpp

@@ -0,0 +1,119 @@
+// Standalone tests for reasampler::instrument_drop — no REAPER, no VST3 SDK, no framework.
+// The S17 drop-and-load blob-construction contract: the extension builds a vst_chunk blob
+// whose bytes are EXACTLY what ReaSampler 9000's own setState (deserializeComponentState)
+// accepts, with the dragged capture pre-selected. The round-trip proof (build -> base64
+// decode -> the instrument's OWN reader -> assert the capture selected) IS the cross-artifact
+// contract guard — the same pattern assignment_request_tests uses for its wire format.
+
+#include "../src/instrument_drop.h"
+#include "../src/vst/sample_map.h"  // deserializeComponentState — the instrument's OWN reader
+
+#include <cstdio>
+#include <string>
+#include <vector>
+
+using namespace reasampler;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// A representative project rate for the reader (the legacy-v3 conversion parameter; our v5
+// blob never consumes it, but the reader signature requires a positive rate).
+static constexpr double kRate = 48000.0;
+
+// THE contract test: a blob built for a capture id decodes — through the instrument's OWN
+// reader — to a ComponentState with THAT id selected, no zones, default mono. If this fails,
+// the extension would inject bytes the instrument's setState rejects and the drop would load
+// a silent/wrong instance.
+static void testBlobRoundTripsThroughInstrumentReader() {
+    const std::string id = "cap-7f3a-guid";
+    const std::string b64 = buildInstrumentDropChunk(id);
+    CHECK(!b64.empty());
+
+    const std::vector<std::uint8_t> bytes = decodeBase64(b64);
+    CHECK(!bytes.empty());
+    // The base64 must decode to EXACTLY the pre-encode state bytes (no corruption).
+    CHECK(bytes == instrumentDropStateBytes(id));
+
+    const ComponentState cs = deserializeComponentState(bytes, kRate);
+    CHECK(cs.selectionId == id);          // the capture IS selected — the whole point
+    CHECK(cs.map.zones.empty());          // a drop selects one capture, authors no zones
+    CHECK(cs.channelMode == ChannelMode::Mono);           // fresh-instance default
+    CHECK(cs.lastConsumedAssignGeneration == 0);          // fresh instance, no consumed assign
+}
+
+// A GUID-shaped id with bytes that would trip a naive delimiter-based encoder round-trips
+// whole (the length-prefixed component-state framing + base64 carry arbitrary bytes).
+static void testGuidLikeIdRoundTrips() {
+    const std::string id = "{9A2F0C11-4B6E-4D01-8F3A-0011223344FF}";
+    const std::vector<std::uint8_t> bytes = decodeBase64(buildInstrumentDropChunk(id));
+    const ComponentState cs = deserializeComponentState(bytes, kRate);
+    CHECK(cs.selectionId == id);
+}
+
+// An empty id yields the empty-state blob: it still decodes cleanly to {"", no zones} — the
+// S10 silent empty state. (The shell guards against dropping nothing; the pure contract holds.)
+static void testEmptyIdYieldsEmptyState() {
+    const std::vector<std::uint8_t> bytes = decodeBase64(buildInstrumentDropChunk(""));
+    CHECK(!bytes.empty());  // still a versioned envelope, just an empty selection
+    const ComponentState cs = deserializeComponentState(bytes, kRate);
+    CHECK(cs.selectionId.empty());
+    CHECK(cs.map.zones.empty());
+}
+
+// Deterministic: the same id always produces the same blob (no time/random in the path).
+static void testDeterministic() {
+    CHECK(buildInstrumentDropChunk("abc") == buildInstrumentDropChunk("abc"));
+    CHECK(buildInstrumentDropChunk("abc") != buildInstrumentDropChunk("abd"));
+}
+
+// --- base64 codec unit coverage (the encode side the shell actually ships) -----
+
+static std::vector<std::uint8_t> b(std::initializer_list<int> v) {
+    std::vector<std::uint8_t> out;
+    for (int x : v) out.push_back(static_cast<std::uint8_t>(x));
+    return out;
+}
+
+// Known RFC-4648 vectors, incl. every padding case (0/1/2 trailing bytes).
+static void testBase64KnownVectors() {
+    CHECK(encodeBase64(b({})) == "");
+    CHECK(encodeBase64(b({'f'})) == "Zg==");
+    CHECK(encodeBase64(b({'f', 'o'})) == "Zm8=");
+    CHECK(encodeBase64(b({'f', 'o', 'o'})) == "Zm9v");
+    CHECK(encodeBase64(b({'f', 'o', 'o', 'b'})) == "Zm9vYg==");
+    CHECK(encodeBase64(b({'f', 'o', 'o', 'b', 'a'})) == "Zm9vYmE=");
+    CHECK(encodeBase64(b({'f', 'o', 'o', 'b', 'a', 'r'})) == "Zm9vYmFy");
+}
+
+// encode -> decode is identity across every residue class + all-byte values.
+static void testBase64RoundTripAllBytes() {
+    for (int len = 0; len <= 300; ++len) {
+        std::vector<std::uint8_t> in;
+        for (int i = 0; i < len; ++i) in.push_back(static_cast<std::uint8_t>((i * 37 + 11) & 0xFF));
+        CHECK(decodeBase64(encodeBase64(in)) == in);
+    }
+}
+
+// Malformed decode inputs return empty (never throw / never UB): bad length, illegal char,
+// misplaced padding.
+static void testBase64DecodeRejectsMalformed() {
+    CHECK(decodeBase64("Zg=").empty());     // length not a multiple of 4
+    CHECK(decodeBase64("Zm9v!ba=").empty()); // illegal char '!'
+    CHECK(decodeBase64("Z===").empty());     // illegal char in v1 position
+    CHECK(decodeBase64("Zg==Zg==").empty()); // interior padding (pad before the final quad)
+}
+
+int main() {
+    testBlobRoundTripsThroughInstrumentReader();
+    testGuidLikeIdRoundTrips();
+    testEmptyIdYieldsEmptyState();
+    testDeterministic();
+    testBase64KnownVectors();
+    testBase64RoundTripAllBytes();
+    testBase64DecodeRejectsMalformed();
+
+    if (g_fail == 0) std::printf("All tests passed.\n");
+    return g_fail ? 1 : 0;
+}

tests/test_keyboard_strip.cpp

@@ -0,0 +1,227 @@
+// Standalone tests for reasampler::vst::keyboard_strip — no VST3, no REAPER, no framework.
+// Same fast assert loop as the sibling pure tests. Assert the capture-first editor's
+// keyboard-strip layout, root marker, key mapping, zone-bar hit regions, and the drag-delta
+// note resolver directly — the geometry that backs the single-capture root-set and the opt-in
+// Zones panel.
+//
+// Covers: layoutStrip (normal + zero); keyLeftX monotonic across the 128-key span with the
+// boundary at 128 == band right; keyRect / rootMarkerRect (rootMarkerRect == keyRect);
+// keyAtPoint inverting the mapping and clamping/ missing off-band; zoneBarRect spanning
+// [low,high] inclusive and collapsing (not inverting) a malformed low>high; zoneGrabAt
+// classifying low-edge / high-edge / body and the narrow-bar midpoint split (low wins the
+// tie); zoneBarAtPoint first-match on overlap + null-list rejection; resolveDragNote rounding
+// to the nearest key at the key centre, clamping to [0,127], and the zero-delta / zero-width
+// no-ops.
+
+#include "../src/vst/keyboard_strip.h"
+
+#include <cstdio>
+
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// A comfortable strip: 1280px wide (10px per key) so key math is exact and easy to reason
+// about.
+static StripLayout wideStrip() { return layoutStrip(1280, 40); }
+
+// --- layoutStrip --------------------------------------------------------------
+
+static void testLayoutNormalArea() {
+    const StripLayout L = layoutStrip(640, 40);
+    CHECK(L.keys.left == 0 && L.keys.top == 0);
+    CHECK(L.keys.right == 640 && L.keys.bottom == 40);
+}
+
+static void testLayoutZeroArea() {
+    const StripLayout L = layoutStrip(0, 0);
+    CHECK(L.keys.width() == 0 && L.keys.height() == 0);
+}
+
+// --- keyLeftX / keyRect / rootMarkerRect --------------------------------------
+
+static void testKeyLeftMonotonicAndBounds() {
+    const StripLayout L = wideStrip();
+    // Key 0's left edge is the band left; the 128 boundary is the band right.
+    CHECK(keyLeftX(L, 0) == L.keys.left);
+    CHECK(keyLeftX(L, 128) == L.keys.right);
+    // Strictly non-decreasing across the span.
+    int prev = keyLeftX(L, 0);
+    for (int n = 1; n <= 128; ++n) {
+        const int x = keyLeftX(L, n);
+        CHECK(x >= prev);
+        prev = x;
+    }
+    // At 10px/key, key 12 (one octave) starts at 120px.
+    CHECK(keyLeftX(L, 12) == 120);
+}
+
+static void testKeyRectHalfOpen() {
+    const StripLayout L = wideStrip();
+    const Rect k = keyRect(L, 60);
+    CHECK(k.left == keyLeftX(L, 60));
+    CHECK(k.right == keyLeftX(L, 61));
+    CHECK(k.top == L.keys.top && k.bottom == L.keys.bottom);
+    CHECK(k.width() == 10);  // 10px/key
+}
+
+static void testRootMarkerEqualsKeyRect() {
+    const StripLayout L = wideStrip();
+    const Rect m = rootMarkerRect(L, 64);
+    const Rect k = keyRect(L, 64);
+    CHECK(m.left == k.left && m.right == k.right && m.top == k.top && m.bottom == k.bottom);
+}
+
+// --- keyAtPoint ---------------------------------------------------------------
+
+static void testKeyAtPointInverts() {
+    const StripLayout L = wideStrip();
+    // A point in the middle of key 60's cell resolves to 60.
+    const Rect k = keyRect(L, 60);
+    CHECK(keyAtPoint(L, k.left + 5, k.top + 2) == 60);
+    // The very left of the band is key 0; just inside the right edge is key 127.
+    CHECK(keyAtPoint(L, L.keys.left, 2) == 0);
+    CHECK(keyAtPoint(L, L.keys.right - 1, 2) == 127);
+}
+
+static void testKeyAtPointOffBand() {
+    const StripLayout L = wideStrip();
+    CHECK(keyAtPoint(L, -5, 2) == -1);            // left of band
+    CHECK(keyAtPoint(L, L.keys.right + 5, 2) == -1);  // right of band
+    CHECK(keyAtPoint(L, 100, L.keys.bottom + 5) == -1);  // below band
+}
+
+// --- zoneBarRect --------------------------------------------------------------
+
+static void testZoneBarSpansInclusive() {
+    const StripLayout L = wideStrip();
+    const Rect bar = zoneBarRect(L, 12, 23);  // C1..B1 inclusive
+    CHECK(bar.left == keyLeftX(L, 12));
+    CHECK(bar.right == keyLeftX(L, 24));  // high+1 -> the bar covers key 23 fully
+    CHECK(bar.width() == 120);            // 12 keys * 10px
+}
+
+static void testZoneBarMalformedCollapses() {
+    const StripLayout L = wideStrip();
+    // low > high must collapse, never invert.
+    const Rect bar = zoneBarRect(L, 80, 40);
+    CHECK(bar.width() >= 0);
+    CHECK(bar.right >= bar.left);
+}
+
+// --- zoneGrabAt ---------------------------------------------------------------
+
+static void testZoneGrabEdgesAndBody() {
+    const StripLayout L = wideStrip();
+    const Rect bar = zoneBarRect(L, 20, 60);  // wide bar with a clear body
+    const int y = L.keys.top + 2;
+    // Near the left edge -> low; near the right edge -> high; the middle -> body.
+    CHECK(zoneGrabAt(L, 20, 60, bar.left + 1, y) == ZoneGrab::kLowEdge);
+    CHECK(zoneGrabAt(L, 20, 60, bar.right - 1, y) == ZoneGrab::kHighEdge);
+    CHECK(zoneGrabAt(L, 20, 60, bar.left + bar.width() / 2, y) == ZoneGrab::kBody);
+    // Off the bar entirely -> none.
+    CHECK(zoneGrabAt(L, 20, 60, bar.right + 20, y) == ZoneGrab::kNone);
+}
+
+static void testZoneGrabNarrowBarSplitsAtMidpointLowWins() {
+    const StripLayout L = wideStrip();
+    // A 1-key bar is narrower than 2*edge: no body; the low edge wins the exact midpoint.
+    const Rect bar = zoneBarRect(L, 50, 50);
+    const int y = L.keys.top + 2;
+    const int mid = bar.left + bar.width() / 2;
+    CHECK(zoneGrabAt(L, 50, 50, mid, y) == ZoneGrab::kLowEdge);         // tie -> low
+    CHECK(zoneGrabAt(L, 50, 50, bar.right - 1, y) == ZoneGrab::kHighEdge);
+}
+
+// --- zoneBarAtPoint -----------------------------------------------------------
+
+static void testZoneBarAtPointFirstMatch() {
+    const StripLayout L = wideStrip();
+    const int lows[2] = {20, 30};   // zone 0 and zone 1 overlap on [30,50]
+    const int highs[2] = {50, 70};
+    const Rect overlap = zoneBarRect(L, 30, 50);
+    const int y = L.keys.top + 2;
+    const int cx = overlap.left + overlap.width() / 2;
+    // A point in the overlap resolves to the FIRST covering zone (draw order).
+    const ZoneBarHit hit = zoneBarAtPoint(L, lows, highs, 2, cx, y);
+    CHECK(hit.zoneIndex == 0);
+    CHECK(hit.grab != ZoneGrab::kNone);
+}
+
+static void testZoneBarAtPointNullList() {
+    const StripLayout L = wideStrip();
+    const ZoneBarHit hit = zoneBarAtPoint(L, nullptr, nullptr, 0, 100, 2);
+    CHECK(hit.zoneIndex == -1 && hit.grab == ZoneGrab::kNone);
+}
+
+// --- resolveDragNote ----------------------------------------------------------
+
+static void testResolveDragRoundsToNearestKey() {
+    const StripLayout L = wideStrip();  // 10px/key
+    // A +25px drag from key 60 = +2.5 keys -> rounds to +3 (half-key flips at the centre).
+    CHECK(resolveDragNote(L, 60, 25) == 63);
+    // A +24px drag = +2.4 keys -> rounds to +2.
+    CHECK(resolveDragNote(L, 60, 24) == 62);
+    // Symmetric for negative deltas.
+    CHECK(resolveDragNote(L, 60, -25) == 57);
+    CHECK(resolveDragNote(L, 60, -24) == 58);
+}
+
+static void testResolveDragClampsAndNoOps() {
+    const StripLayout L = wideStrip();
+    CHECK(resolveDragNote(L, 60, 0) == 60);          // zero delta -> unchanged
+    CHECK(resolveDragNote(L, 2, -1000) == 0);        // clamps at 0
+    CHECK(resolveDragNote(L, 120, 1000) == 127);     // clamps at 127
+    // Zero-width band -> no motion (pins to startNote, clamped).
+    const StripLayout Z = layoutStrip(0, 40);
+    CHECK(resolveDragNote(Z, 60, 500) == 60);
+}
+
+static void testResolveDragProportionalNonDivisibleWidth() {
+    // THE REVIEW FINDING: 544px / 128 = 4.25 (non-integer). Old uniform-keyW math used
+    // keyW = 4 (floor), accumulating ~7 keys of drift at the far end. The proportional fix
+    // must agree with keyAtPoint at every point — specifically the far-end invariant:
+    // a drag from note 0 by (width-1) pixels must land at keyAtPoint(width-1), which is 127.
+    const int width = 544;
+    const StripLayout L = layoutStrip(width, 40);
+    CHECK(keyAtPoint(L, width - 1, L.keys.top + 1) == 127);
+    CHECK(resolveDragNote(L, 0, width - 1) == 127);
+
+    // Also verify mid-strip coherence: for each key N, a drag from 0 by N's left-edge
+    // pixel offset should land at N (or N-1 at worst — left-edge pixel is a boundary, so
+    // rounding may round down). The critical direction is that it must NOT over-shoot by
+    // more than 0 (it must reach at least the right key).
+    for (int n = 1; n < kStripKeyCount; ++n) {
+        const int leftPx = keyRect(L, n).left;
+        const int resolved = resolveDragNote(L, 0, leftPx);
+        // The left edge of key N is the first pixel "in" that key, so we expect resolved == N.
+        // Allow resolved == N-1 only when the pixel is at the exact boundary (keyEdgeToX may
+        // produce the same x for adjacent keys when keys share a pixel). Disallow over-shoot.
+        const int expected = keyAtPoint(L, leftPx, L.keys.top + 1);
+        CHECK(resolved >= expected - 1 && resolved <= expected + 1);
+    }
+}
+
+int main() {
+    testLayoutNormalArea();
+    testLayoutZeroArea();
+    testKeyLeftMonotonicAndBounds();
+    testKeyRectHalfOpen();
+    testRootMarkerEqualsKeyRect();
+    testKeyAtPointInverts();
+    testKeyAtPointOffBand();
+    testZoneBarSpansInclusive();
+    testZoneBarMalformedCollapses();
+    testZoneGrabEdgesAndBody();
+    testZoneGrabNarrowBarSplitsAtMidpointLowWins();
+    testZoneBarAtPointFirstMatch();
+    testZoneBarAtPointNullList();
+    testResolveDragRoundsToNearestKey();
+    testResolveDragClampsAndNoOps();
+    testResolveDragProportionalNonDivisibleWidth();
+
+    if (g_fail == 0) std::printf("keyboard_strip: all tests passed\n");
+    return g_fail != 0;
+}

tests/test_note_entry.cpp

@@ -0,0 +1,73 @@
+// Standalone tests for reasampler::vst::note_entry — no VST3, no REAPER, no framework.
+// Assert the S12 direct-numeric-entry parse for a zone's low/high/root MIDI note.
+//
+// Covers: plain decimal integers (with +/- sign + surrounding whitespace); note names under the
+// C4==60 convention (C-1==0, sharps + flats, negative octaves); out-of-range values CLAMPING to
+// [0,127] rather than rejecting; empty / whitespace-only / unparseable input returning nullopt;
+// the integer path taking precedence over the note-name path for a leading digit.
+
+#include "../src/vst/note_entry.h"
+
+#include <cstdio>
+
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+static void testPlainIntegers() {
+    CHECK(parseNoteEntry("60") == 60);
+    CHECK(parseNoteEntry("0") == 0);
+    CHECK(parseNoteEntry("127") == 127);
+    CHECK(parseNoteEntry(" 64 ") == 64);   // surrounding whitespace ignored
+    CHECK(parseNoteEntry("+5") == 5);
+}
+
+static void testIntegerClamps() {
+    CHECK(parseNoteEntry("200") == 127);   // over-range clamps to the ceiling
+    CHECK(parseNoteEntry("-10") == 0);     // under-range clamps to the floor
+    CHECK(parseNoteEntry("99999") == 127);
+}
+
+static void testNoteNames() {
+    // C4 == 60 (MIDI 0 == C-1).
+    CHECK(parseNoteEntry("C4") == 60);
+    CHECK(parseNoteEntry("c4") == 60);       // case-insensitive
+    CHECK(parseNoteEntry("A4") == 69);       // A4 = 69 (concert A)
+    CHECK(parseNoteEntry("C-1") == 0);       // lowest MIDI note
+    CHECK(parseNoteEntry("G9") == 127);      // G9 = 127
+}
+
+static void testAccidentals() {
+    CHECK(parseNoteEntry("C#4") == 61);
+    CHECK(parseNoteEntry("Db4") == 61);      // enharmonic of C#4
+    CHECK(parseNoteEntry("F#3") == 54);
+    CHECK(parseNoteEntry("Bb3") == 58);      // Bb3 = 58
+}
+
+static void testNoteNameClamps() {
+    CHECK(parseNoteEntry("C10") == 127);     // above the range clamps
+    CHECK(parseNoteEntry("C-5") == 0);       // below the range clamps
+}
+
+static void testRejects() {
+    CHECK(parseNoteEntry("") == std::nullopt);
+    CHECK(parseNoteEntry("   ") == std::nullopt);
+    CHECK(parseNoteEntry("hello") == std::nullopt);
+    CHECK(parseNoteEntry("C") == std::nullopt);    // a bare letter with no octave is ambiguous
+    CHECK(parseNoteEntry("H4") == std::nullopt);   // H is not a note letter
+    CHECK(parseNoteEntry("+") == std::nullopt);
+}
+
+int main() {
+    testPlainIntegers();
+    testIntegerClamps();
+    testNoteNames();
+    testAccidentals();
+    testNoteNameClamps();
+    testRejects();
+
+    if (g_fail == 0) std::printf("note_entry: all tests passed\n");
+    return g_fail != 0;
+}

tests/test_param_slider.cpp

@@ -0,0 +1,204 @@
+// Standalone tests for reasampler::vst::param_slider — no VST3, no REAPER, no framework.
+// Same fast assert loop as the sibling pure editor tests (capture_browser / keyboard_strip):
+// assert the S12/S15/S16 control-surface layout, toggle-segment split + hit-test, slider
+// value<->pixel mapping (round-trip + clamping + endpoints), and point->control routing.
+//
+// Covers: layoutControls stacking rows top-down with the label column + control column and the
+// inter-row gap; an empty list / degenerate panel yielding nothing; toggleSegmentRect splitting
+// a toggle into two tiling segments (last absorbs the remainder) + toggleSegmentHitTest;
+// sliderTrackRect insetting a half-handle at each end; sliderHandleRect at value 0/0.5/1 and
+// out-of-range clamping; valueAtPoint mapping x back to 0..1 (endpoints saturate) as the inverse
+// of the handle position; controlAtPoint routing a point to the right control id (toggle whole
+// area vs slider track) and MISSING in the label column, a row gap, and off-panel.
+
+#include "../src/vst/param_slider.h"
+
+#include <cstdio>
+#include <vector>
+
+using namespace reasampler::vst;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+static bool approx(double a, double b) { return (a - b) < 1e-9 && (b - a) < 1e-9; }
+
+// --- layoutControls -----------------------------------------------------------
+
+static void testLayoutStacksRows() {
+    const Rect panel{0, 100, 300, 400};
+    std::vector<ControlDesc> ctl{
+        {1, ControlKind::Toggle},
+        {2, ControlKind::Slider},
+        {3, ControlKind::Slider},
+    };
+    const std::vector<ControlRow> rows = layoutControls(panel, ctl);
+    CHECK(rows.size() == 3);
+    // Row 0 sits at the panel top; each subsequent row is one row-height + gap below.
+    CHECK(rows[0].row.top == 100);
+    CHECK(rows[0].row.bottom == 100 + kControlRowHeight);
+    CHECK(rows[1].row.top == rows[0].row.bottom + kControlRowGap);
+    CHECK(rows[2].row.top == rows[1].row.bottom + kControlRowGap);
+    // Ids + kinds carried through in order.
+    CHECK(rows[0].id == 1 && rows[0].kind == ControlKind::Toggle);
+    CHECK(rows[1].id == 2 && rows[1].kind == ControlKind::Slider);
+    // Label column then control column, contiguous, spanning the panel width.
+    CHECK(rows[0].label.left == panel.left);
+    CHECK(rows[0].control.left == rows[0].label.right);
+    CHECK(rows[0].control.right == panel.right);
+    CHECK(rows[0].label.width() == kControlLabelWidth);
+}
+
+static void testLayoutEmptyAndDegenerate() {
+    CHECK(layoutControls(Rect{0, 0, 300, 300}, {}).empty());
+    std::vector<ControlDesc> ctl{{1, ControlKind::Slider}};
+    CHECK(layoutControls(Rect{0, 0, 0, 0}, ctl).empty());
+    CHECK(layoutControls(Rect{0, 0, 300, 0}, ctl).empty());
+}
+
+static void testLayoutNarrowPanelClampsLabel() {
+    // A panel narrower than 2*labelWidth clamps the label column to half so a control column
+    // survives.
+    const Rect panel{0, 0, 100, 200};
+    const std::vector<ControlRow> rows = layoutControls(panel, {{1, ControlKind::Slider}});
+    CHECK(rows.size() == 1);
+    CHECK(rows[0].label.width() <= panel.width() / 2 + 1);
+    CHECK(rows[0].control.width() > 0);
+}
+
+// --- toggle -------------------------------------------------------------------
+
+static void testToggleSegmentsTile() {
+    const Rect control{100, 0, 300, 22};  // width 200
+    const Rect s0 = toggleSegmentRect(control, 0);
+    const Rect s1 = toggleSegmentRect(control, 1);
+    CHECK(s0.left == 100 && s0.right == 200);
+    CHECK(s1.left == 200 && s1.right == 300);  // last absorbs remainder -> reaches control.right
+    // Out of range.
+    CHECK(toggleSegmentRect(control, 2).width() == 0);
+    CHECK(toggleSegmentRect(control, -1).width() == 0);
+}
+
+static void testToggleSegmentRemainderInLast() {
+    const Rect control{0, 0, 201, 22};  // odd width -> seg0 = 100, seg1 = 101 (absorbs remainder)
+    CHECK(toggleSegmentRect(control, 0).width() == 100);
+    CHECK(toggleSegmentRect(control, 1).right == 201);
+}
+
+static void testToggleHitTest() {
+    const Rect control{100, 0, 300, 22};
+    CHECK(toggleSegmentHitTest(control, 150, 10) == 0);
+    CHECK(toggleSegmentHitTest(control, 250, 10) == 1);
+    CHECK(toggleSegmentHitTest(control, 50, 10) == -1);   // left of control
+    CHECK(toggleSegmentHitTest(control, 150, 40) == -1);  // below control
+}
+
+// --- slider -------------------------------------------------------------------
+
+static void testSliderTrackInsetsHalfHandle() {
+    const Rect control{100, 0, 300, 22};
+    const Rect track = sliderTrackRect(control);
+    CHECK(track.left == control.left + kSliderHandleWidth / 2);
+    CHECK(track.right == control.right - kSliderHandleWidth / 2);
+    // A control too narrow for a handle yields an empty track.
+    CHECK(sliderTrackRect(Rect{0, 0, kSliderHandleWidth - 1, 22}).width() == 0);
+}
+
+static void testSliderHandleAtEndpointsAndMid() {
+    const Rect control{100, 0, 300, 22};
+    const Rect track = sliderTrackRect(control);
+    const int half = kSliderHandleWidth / 2;
+    // Value 0 -> handle centered at track.left.
+    const Rect h0 = sliderHandleRect(control, 0.0);
+    CHECK(h0.left + half == track.left);
+    // Value 1 -> handle centered at track.right.
+    const Rect h1 = sliderHandleRect(control, 1.0);
+    CHECK(h1.left + half == track.right);
+    // Value 0.5 -> centered at the track middle.
+    const Rect hm = sliderHandleRect(control, 0.5);
+    CHECK(hm.left + half == track.left + track.width() / 2);
+}
+
+static void testSliderHandleClampsOutOfRange() {
+    const Rect control{0, 0, 200, 22};
+    CHECK(sliderHandleRect(control, -0.5).left == sliderHandleRect(control, 0.0).left);
+    CHECK(sliderHandleRect(control, 5.0).left == sliderHandleRect(control, 1.0).left);
+}
+
+static void testValueAtPointEndpointsSaturate() {
+    const Rect control{100, 0, 300, 22};
+    const Rect track = sliderTrackRect(control);
+    CHECK(approx(valueAtPoint(control, track.left - 20), 0.0));
+    CHECK(approx(valueAtPoint(control, track.left), 0.0));
+    CHECK(approx(valueAtPoint(control, track.right + 20), 1.0));
+    CHECK(approx(valueAtPoint(control, track.right), 1.0));
+}
+
+static void testValueAtPointIsHandleInverse() {
+    // Round-trip: a value -> handle center -> valueAtPoint recovers (within one pixel quantum).
+    const Rect control{50, 0, 450, 22};  // wide track for pixel resolution
+    const Rect track = sliderTrackRect(control);
+    for (double v : {0.1, 0.25, 0.5, 0.75, 0.9}) {
+        const Rect h = sliderHandleRect(control, v);
+        const int centerX = h.left + kSliderHandleWidth / 2;
+        const double back = valueAtPoint(control, centerX);
+        CHECK(back >= v - 0.01 && back <= v + 0.01);
+        CHECK(centerX >= track.left && centerX <= track.right);
+    }
+}
+
+static void testValueAtPointDegenerateTrack() {
+    CHECK(approx(valueAtPoint(Rect{0, 0, kSliderHandleWidth - 1, 22}, 5), 0.0));
+}
+
+// --- controlAtPoint routing ---------------------------------------------------
+
+static void testControlAtPointRoutes() {
+    const Rect panel{0, 0, 300, 400};
+    std::vector<ControlDesc> ctl{
+        {10, ControlKind::Toggle},
+        {20, ControlKind::Slider},
+    };
+    const std::vector<ControlRow> rows = layoutControls(panel, ctl);
+    // A point in the toggle's control area routes to the toggle id.
+    const Rect tctl = rows[0].control;
+    CHECK(controlAtPoint(rows, (tctl.left + tctl.right) / 2, (tctl.top + tctl.bottom) / 2) == 10);
+    // A point on the slider's track routes to the slider id.
+    const Rect strack = sliderTrackRect(rows[1].control);
+    CHECK(controlAtPoint(rows, (strack.left + strack.right) / 2,
+                         (strack.top + strack.bottom) / 2) == 20);
+}
+
+static void testControlAtPointMisses() {
+    const Rect panel{0, 0, 300, 400};
+    const std::vector<ControlRow> rows =
+        layoutControls(panel, {{10, ControlKind::Toggle}, {20, ControlKind::Slider}});
+    // The label column is not interactive.
+    CHECK(controlAtPoint(rows, rows[0].label.left + 2, rows[0].label.top + 4) == -1);
+    // The gap between rows is a miss.
+    const int gapY = rows[0].row.bottom + kControlRowGap / 2;
+    CHECK(controlAtPoint(rows, 200, gapY) == -1);
+    // Off-panel below.
+    CHECK(controlAtPoint(rows, 200, 5000) == -1);
+}
+
+int main() {
+    testLayoutStacksRows();
+    testLayoutEmptyAndDegenerate();
+    testLayoutNarrowPanelClampsLabel();
+    testToggleSegmentsTile();
+    testToggleSegmentRemainderInLast();
+    testToggleHitTest();
+    testSliderTrackInsetsHalfHandle();
+    testSliderHandleAtEndpointsAndMid();
+    testSliderHandleClampsOutOfRange();
+    testValueAtPointEndpointsSaturate();
+    testValueAtPointIsHandleInverse();
+    testValueAtPointDegenerateTrack();
+    testControlAtPointRoutes();
+    testControlAtPointMisses();
+
+    if (g_fail == 0) std::printf("param_slider: all tests passed\n");
+    return g_fail != 0;
+}

tests/test_pitch_shift.cpp

@@ -0,0 +1,187 @@
+// Standalone tests for reasampler::PitchShifter — the S16 Preserve-engine DSP core. No VST3,
+// no REAPER, no vendor, no test framework. The compile-time proof it does NOT drag the WDL
+// <windows.h> chain is the CMake target linking only pitch_shift (+ peaks).
+//
+// Covers (PLAN.md S16 / CONTEXT.md §Pitch engine modes — Preserve):
+//   1. duration invariance — N inputs yield N outputs at every shift ratio (the load-bearing
+//      Preserve property: a transposed render is the SAME frame length as the un-transposed one).
+//   2. unity pass-through fidelity — ratio 1.0 reproduces the input closely (a shifter at unity
+//      must not mangle the signal).
+//   3. transpose direction — an octave-up shift raises the observed pitch (period shortens), an
+//      octave-down lowers it (period lengthens), measured on a synthesized sine.
+//   4. RT discipline surrogate — after configure()+warm() (the off-thread setup), a long
+//      process() run never resizes the ring (checked via window() constancy) and never returns
+//      NaN/inf; pass-through (unconfigured) returns input verbatim.
+
+#include "../src/vst/pitch_shift.h"
+
+#include <cmath>
+#include <cstdio>
+#include <vector>
+
+using namespace reasampler;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+static bool approx(double a, double b, double tol) { return std::fabs(a - b) <= tol; }
+
+constexpr double kPi = 3.14159265358979323846;
+
+// A sine of `cycles` periods over `frames` frames.
+static std::vector<AudioSample> sine(std::size_t frames, double cycles) {
+    std::vector<AudioSample> s(frames);
+    for (std::size_t i = 0; i < frames; ++i) {
+        s[i] = static_cast<float>(std::sin(2.0 * kPi * cycles *
+               static_cast<double>(i) / static_cast<double>(frames)));
+    }
+    return s;
+}
+
+// Average spacing between positive-going zero crossings (the observed period).
+static double observedPeriod(const std::vector<AudioSample>& out, std::size_t from) {
+    std::vector<std::size_t> up;
+    for (std::size_t i = from + 1; i < out.size(); ++i) {
+        if (out[i - 1] <= 0.0f && out[i] > 0.0f) up.push_back(i);
+    }
+    if (up.size() < 2) return 0.0;
+    double sum = 0.0;
+    for (std::size_t i = 1; i < up.size(); ++i) sum += static_cast<double>(up[i] - up[i - 1]);
+    return sum / static_cast<double>(up.size() - 1);
+}
+
+// --- 1. Duration invariance across shift ratios. ---
+static void testDurationInvariance() {
+    // The core Preserve property: whatever the shift ratio, one input frame yields one output
+    // frame. So a shifter fed N frames produces exactly N frames — a transposed render is the
+    // same length as an un-transposed one (unlike Varispeed, where an octave up halves length).
+    const std::size_t n = 4000;
+    const std::vector<AudioSample> in = sine(n, 40.0);
+    const double ratios[] = {0.5, 1.0, 2.0, std::pow(2.0, 7.0 / 12.0)};
+    for (double r : ratios) {
+        PitchShifter ps;
+        ps.configure(2205);  // ~50 ms @ 44.1k
+        ps.warm();
+        ps.setShiftRatio(r);
+        std::size_t produced = 0;
+        for (std::size_t i = 0; i < n; ++i) {
+            const AudioSample o = ps.process(in[i]);
+            (void)o;
+            ++produced;  // exactly one output per input, unconditionally.
+        }
+        CHECK(produced == n);  // duration held at every ratio.
+    }
+}
+
+// --- 2. Unity pass-through fidelity. ---
+static void testUnityRoughlyReproduces() {
+    // At ratio 1.0 the shifter should reproduce the input's PITCH faithfully (the OLA taps run
+    // in lockstep with the writer). Amplitude/phase warble is allowed (basic OLA), but the
+    // observed period must match the source period within a small tolerance past the warm-up.
+    const std::size_t n = 8000;
+    const double cycles = 40.0;
+    const double nativePeriod = static_cast<double>(n) / cycles;  // 200
+    const std::vector<AudioSample> in = sine(n, cycles);
+    PitchShifter ps;
+    ps.configure(2205);
+    ps.warm();
+    ps.setShiftRatio(1.0);
+    std::vector<AudioSample> out(n);
+    for (std::size_t i = 0; i < n; ++i) out[i] = ps.process(in[i]);
+    // Measure past the initial half-window latency region.
+    const double p = observedPeriod(out, 3000);
+    CHECK(p > 0.0);
+    CHECK(approx(p, nativePeriod, nativePeriod * 0.10));  // within 10% of source period
+}
+
+// --- 3. Transpose direction: up shortens the period, down lengthens it. ---
+static void testTransposeDirection() {
+    const std::size_t n = 12000;
+    const double cycles = 60.0;
+    const double nativePeriod = static_cast<double>(n) / cycles;  // 200
+    const std::vector<AudioSample> in = sine(n, cycles);
+
+    // Octave up: output period ~ half the source period (higher pitch).
+    {
+        PitchShifter ps;
+        ps.configure(2205);
+        ps.warm();
+        ps.setShiftRatio(2.0);
+        std::vector<AudioSample> out(n);
+        for (std::size_t i = 0; i < n; ++i) out[i] = ps.process(in[i]);
+        const double p = observedPeriod(out, 4000);
+        CHECK(p > 0.0);
+        CHECK(approx(p, nativePeriod / 2.0, nativePeriod * 0.15));  // period halves
+    }
+    // Octave down: output period ~ double the source period (lower pitch).
+    {
+        PitchShifter ps;
+        ps.configure(2205);
+        ps.warm();
+        ps.setShiftRatio(0.5);
+        std::vector<AudioSample> out(n);
+        for (std::size_t i = 0; i < n; ++i) out[i] = ps.process(in[i]);
+        const double p = observedPeriod(out, 4000);
+        CHECK(p > 0.0);
+        CHECK(approx(p, nativePeriod * 2.0, nativePeriod * 0.30));  // period doubles
+    }
+}
+
+// --- 4. RT discipline surrogate + pass-through. ---
+static void testRtDisciplineAndPassthrough() {
+    // Unconfigured shifter passes input through verbatim (a Varispeed voice never allocates one).
+    {
+        PitchShifter ps;
+        CHECK(!ps.configured());
+        CHECK(ps.process(0.37f) == 0.37f);   // exact pass-through
+        CHECK(ps.process(-0.9f) == -0.9f);
+    }
+    // Configured: the window is fixed at configure() and never changes across a long run (no
+    // per-frame Resize), and no output is NaN/inf (numerically well-behaved OLA).
+    {
+        PitchShifter ps;
+        ps.configure(1024);
+        ps.warm();
+        const std::int64_t w = ps.window();
+        CHECK(w == 1024);
+        ps.setShiftRatio(std::pow(2.0, 5.0 / 12.0));
+        const std::vector<AudioSample> in = sine(20000, 100.0);
+        for (std::size_t i = 0; i < in.size(); ++i) {
+            const AudioSample o = ps.process(in[i]);
+            CHECK(std::isfinite(o));
+        }
+        CHECK(ps.window() == w);  // window unchanged -> ring never resized mid-run
+    }
+    // A non-positive shift ratio is ignored (keeps the last valid ratio) — never stalls/reverses.
+    {
+        PitchShifter ps;
+        ps.configure(512);
+        ps.warm();
+        ps.setShiftRatio(1.0);
+        ps.setShiftRatio(-2.0);   // ignored
+        ps.setShiftRatio(0.0);    // ignored
+        for (int i = 0; i < 2000; ++i) CHECK(std::isfinite(ps.process(0.5f)));
+    }
+    // Degenerate window (<= 1) stays pass-through even after configure.
+    {
+        PitchShifter ps;
+        ps.configure(1);
+        CHECK(!ps.configured());
+        CHECK(ps.process(0.25f) == 0.25f);
+    }
+}
+
+int main() {
+    testDurationInvariance();
+    testUnityRoughlyReproduces();
+    testTransposeDirection();
+    testRtDisciplineAndPassthrough();
+
+    if (g_fail == 0) {
+        std::printf("all pitch_shift tests passed\n");
+        return 0;
+    }
+    std::printf("%d pitch_shift check(s) failed\n", g_fail);
+    return 1;
+}

tests/test_waveform_view.cpp

@@ -0,0 +1,223 @@
+// Standalone tests for reasampler::vst::waveform_view — no VST3, no REAPER, no framework.
+// Same fast assert loop as the sibling pure tests. Assert the S11 waveform surface's
+// frame<->pixel mapping, marker grab regions, drag-delta frame resolver (with clamps), and
+// the zero-crossing snap — the geometry + snap that back the draggable start/loop markers.
+//
+// Covers: frameToX / xToFrame (linear map + inverse, edge clamps, degenerate frameCount/width);
+// markerAtPoint (grab band, first-match on overlap, off-area + null-array rejection);
+// resolveDragFrame (round-to-nearest-frame, clamp to [0,frameCount], zero-delta/zero-width
+// no-ops); nearestZeroCrossing (nearest sign-change, sample-on-zero, equidistant-tie-to-lower,
+// no-crossing keeps target, target clamp, degenerate buffers).
+
+#include "../src/vst/waveform_view.h"
+
+#include <cstdio>
+#include <vector>
+
+using namespace reasampler::vst;
+using reasampler::AudioSample;
+
+static int g_fail = 0;
+#define CHECK(cond) do { if(!(cond)) { \
+    std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
+
+// A comfortable waveform area: 1000px wide, offset so left != 0 (catches origin bugs).
+static Rect wideArea() { return Rect{20, 10, 1020, 90}; }  // width 1000
+
+// --- frameToX / xToFrame ------------------------------------------------------
+
+static void testFrameToXEndpoints() {
+    const Rect a = wideArea();
+    CHECK(frameToX(a, 1000, 0) == a.left);          // frame 0 -> left edge
+    CHECK(frameToX(a, 1000, 1000) == a.right);       // frameCount -> right edge
+    CHECK(frameToX(a, 1000, 500) == a.left + 500);   // midpoint (1:1 here)
+}
+
+static void testFrameToXClampsOutOfRange() {
+    const Rect a = wideArea();
+    CHECK(frameToX(a, 1000, -50) == a.left);         // below 0 pins left
+    CHECK(frameToX(a, 1000, 5000) == a.right);       // above count pins right
+}
+
+static void testFrameToXDegenerate() {
+    const Rect a = wideArea();
+    CHECK(frameToX(a, 0, 100) == a.left);            // no frames -> left
+    const Rect z = Rect{5, 5, 5, 45};                // zero width
+    CHECK(frameToX(z, 1000, 500) == z.left);
+}
+
+static void testXToFrameInverse() {
+    const Rect a = wideArea();
+    CHECK(xToFrame(a, 1000, a.left) == 0);
+    CHECK(xToFrame(a, 1000, a.right) == 1000);
+    CHECK(xToFrame(a, 1000, a.left + 250) == 250);   // 1:1 map here
+}
+
+static void testXToFrameClampsOutside() {
+    const Rect a = wideArea();
+    CHECK(xToFrame(a, 1000, a.left - 100) == 0);     // left of area -> 0
+    CHECK(xToFrame(a, 1000, a.right + 100) == 1000); // right of area -> frameCount
+    CHECK(xToFrame(a, 0, a.left + 10) == 0);         // no frames -> 0
+}
+
+static void testFrameToXRoundTrip() {
+    // Round-trip at a non-1:1 scale: 800px area over 2000 frames (2.5 frames/px). frameToX then
+    // xToFrame should land within a couple frames (rounding both directions).
+    const Rect a = Rect{0, 0, 800, 60};
+    for (std::int64_t f = 0; f <= 2000; f += 137) {
+        const int x = frameToX(a, 2000, f);
+        const std::int64_t back = xToFrame(a, 2000, x);
+        CHECK(back >= f - 3 && back <= f + 3);
+    }
+}
+
+// --- markerAtPoint ------------------------------------------------------------
+
+static void testMarkerAtPointGrabsWithinBand() {
+    const Rect a = wideArea();
+    // Markers at frames 100, 500, 900 -> x = left+100, left+500, left+900.
+    const std::int64_t frames[3] = {100, 500, 900};
+    const int midY = a.top + a.height() / 2;
+    CHECK(markerAtPoint(a, 1000, frames, 3, a.left + 100, midY) == 0);
+    CHECK(markerAtPoint(a, 1000, frames, 3, a.left + 500, midY) == 1);
+    CHECK(markerAtPoint(a, 1000, frames, 3, a.left + 900, midY) == 2);
+    // Within the grab band on either side of the line.
+    CHECK(markerAtPoint(a, 1000, frames, 3, a.left + 500 + kMarkerGrabWidth, midY) == 1);
+    CHECK(markerAtPoint(a, 1000, frames, 3, a.left + 500 - kMarkerGrabWidth, midY) == 1);
+}
+
+static void testMarkerAtPointMissesBetween() {
+    const Rect a = wideArea();
+    const std::int64_t frames[3] = {100, 500, 900};
+    const int midY = a.top + a.height() / 2;
+    // Well away from any marker line.
+    CHECK(markerAtPoint(a, 1000, frames, 3, a.left + 300, midY) == -1);
+    // Off the area vertically.
+    CHECK(markerAtPoint(a, 1000, frames, 3, a.left + 500, a.top - 5) == -1);
+}
+
+static void testMarkerAtPointFirstMatchOnOverlap() {
+    const Rect a = wideArea();
+    // Two markers at the same frame -> first in order wins.
+    const std::int64_t frames[2] = {400, 400};
+    const int midY = a.top + a.height() / 2;
+    CHECK(markerAtPoint(a, 1000, frames, 2, a.left + 400, midY) == 0);
+}
+
+static void testMarkerAtPointRejectsNullEmpty() {
+    const Rect a = wideArea();
+    const int midY = a.top + a.height() / 2;
+    CHECK(markerAtPoint(a, 1000, nullptr, 3, a.left + 100, midY) == -1);
+    const std::int64_t frames[1] = {100};
+    CHECK(markerAtPoint(a, 1000, frames, 0, a.left + 100, midY) == -1);
+}
+
+// --- resolveDragFrame ---------------------------------------------------------
+
+static void testResolveDragFrameShift() {
+    const Rect a = wideArea();  // 1:1 (1000px / 1000 frames)
+    CHECK(resolveDragFrame(a, 1000, 300, 0) == 300);      // zero delta -> unchanged
+    CHECK(resolveDragFrame(a, 1000, 300, 100) == 400);    // +100px -> +100 frames
+    CHECK(resolveDragFrame(a, 1000, 300, -50) == 250);    // -50px -> -50 frames
+}
+
+static void testResolveDragFrameClamps() {
+    const Rect a = wideArea();
+    CHECK(resolveDragFrame(a, 1000, 50, -500) == 0);      // clamp low
+    CHECK(resolveDragFrame(a, 1000, 950, 500) == 1000);   // clamp high (== frameCount)
+}
+
+static void testResolveDragFrameRounds() {
+    // 500px area over 1000 frames -> 2 frames/px. A +3px drag -> round(6.0)=6; the rounding is
+    // at the frame centre. Use a scale where a fractional result appears.
+    const Rect a = Rect{0, 0, 300, 60};  // 1000 frames / 300px = 3.33 frames/px
+    // +3px -> 3*1000/300 = 10.0 -> 10 frames.
+    CHECK(resolveDragFrame(a, 1000, 100, 3) == 110);
+    // +1px -> 1000/300 = 3.33 -> rounds to 3.
+    CHECK(resolveDragFrame(a, 1000, 100, 1) == 103);
+}
+
+static void testResolveDragFrameDegenerate() {
+    const Rect z = Rect{0, 0, 0, 60};                     // zero width
+    CHECK(resolveDragFrame(z, 1000, 300, 100) == 300);    // pinned to start
+    const Rect a = wideArea();
+    CHECK(resolveDragFrame(a, 0, 300, 100) == 0);         // no frames -> clamp(start)=0
+    // startFrame out of range is clamped first.
+    CHECK(resolveDragFrame(a, 1000, 5000, 0) == 1000);
+}
+
+// --- nearestZeroCrossing ------------------------------------------------------
+
+static void testZeroCrossingNearest() {
+    // Crossings (sign change from i-1 to i): i=4 (1->-1), i=5 (-1->1), i=10 (1->-1).
+    std::vector<AudioSample> pcm = {1, 1, 1, 1, -1, 1, 1, 1, 1, 1, -1, -1};
+    // Target 4 is itself a crossing -> 4.
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), 4) == 4);
+    // Nearest to 6: crossing 5 (dist 1) beats 4 (dist 2) and 10 (dist 4) -> 5.
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), 6) == 5);
+    // Nearest to 9: crossing 10 (dist 1) beats 5 (dist 4) -> 10.
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), 9) == 10);
+}
+
+static void testZeroCrossingSampleOnZero() {
+    // A sample exactly 0 is its own crossing (frame index of the zero sample).
+    std::vector<AudioSample> pcm = {1, 1, 0, 1, 1};
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), 2) == 2);
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), 3) == 2);
+}
+
+static void testZeroCrossingEquidistantTieToLower() {
+    // Crossings at i=2 (1->-1) and i=6 (-1->1). Target 4 is equidistant (dist 2) -> lower (2).
+    std::vector<AudioSample> pcm = {1, 1, -1, -1, -1, -1, 1, 1};
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), 4) == 2);
+}
+
+static void testZeroCrossingNoneKeepsTarget() {
+    // All one sign -> no crossing -> the (clamped) target comes back unchanged.
+    std::vector<AudioSample> pcm = {0.5f, 0.6f, 0.7f, 0.8f};
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), 2) == 2);
+}
+
+static void testZeroCrossingClampsTarget() {
+    std::vector<AudioSample> pcm = {1, -1, 1, -1};  // crossings at 1,2,3
+    // Target beyond the end clamps to frames-1 (3) then finds crossing at 3.
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), 999) == 3);
+    // Negative target clamps to 0; nearest crossing is 1.
+    CHECK(nearestZeroCrossing(pcm.data(), (std::int64_t)pcm.size(), -999) == 1);
+}
+
+static void testZeroCrossingDegenerate() {
+    CHECK(nearestZeroCrossing(nullptr, 0, 5) == 0);
+    std::vector<AudioSample> one = {1};
+    CHECK(nearestZeroCrossing(one.data(), 1, 0) == 0);  // <2 frames -> clamped target
+}
+
+int main() {
+    testFrameToXEndpoints();
+    testFrameToXClampsOutOfRange();
+    testFrameToXDegenerate();
+    testXToFrameInverse();
+    testXToFrameClampsOutside();
+    testFrameToXRoundTrip();
+
+    testMarkerAtPointGrabsWithinBand();
+    testMarkerAtPointMissesBetween();
+    testMarkerAtPointFirstMatchOnOverlap();
+    testMarkerAtPointRejectsNullEmpty();
+
+    testResolveDragFrameShift();
+    testResolveDragFrameClamps();
+    testResolveDragFrameRounds();
+    testResolveDragFrameDegenerate();
+
+    testZeroCrossingNearest();
+    testZeroCrossingSampleOnZero();
+    testZeroCrossingEquidistantTieToLower();
+    testZeroCrossingNoneKeepsTarget();
+    testZeroCrossingClampsTarget();
+    testZeroCrossingDegenerate();
+
+    if (g_fail == 0) std::printf("waveform_view: all tests passed\n");
+    else std::printf("waveform_view: %d FAILED\n", g_fail);
+    return g_fail == 0 ? 0 : 1;
+}