# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Repo identity and current state

The CMake project and binary are now named `reaper_reasampler`. This is **ReaSampler** — a per-project audio sample-bank capture tool that now builds TWO artifacts: the REAPER extension (`reaper_reasampler`) AND **ReaSampler 9000**, a Windows-only VST3 sampler instrument (`reasampler_9000.vst3`, `src/vst/`, second CMake target `reasampler_vst`, gated on the vendored `vendor/vst3sdk` submodule slice). The MPE modules (`mpe_model`, `mpe_view`) have been removed. M0–M8 are complete (bank_model, peaks, capture offline+realtime, persist, bank_panel, insert, capture action family, RealtimeRecordBackend, tail T1+T2+T1-followons). Phase B multi-bank (B1–B5, B-cap), Phase D1/D2 Design View (D1–D5, D2-W1–W3-B), Phase V versioning/beta-channel (V1/V3, V4), M10 provenance + re-capture from source, Phase R Reclaim (R1–R3: prune-reconcile core, dry-run shell, guarded deletion + action + panel button), M11 in full (batch capture, action-button strip + keybinding labels, conform-on-insert verified-extant, native OS drag-out), Phase L L1 (shared LICE drawing kit: `theme`/palette module, `component_geometry` geometry helpers, `draw_kit` shell, GDI DrawText retired in `bank_panel`), Phase L L2 (dock-panel layout redesign: `action_bar` pure task-grouped layout module, full M11-aware button inventory placed by task cluster, `bank_panel` redesigned through the L1 kit), Phase L L4 (dock-panel button layout enhancement: three-zone layout — top capture/placement/maintenance toolbar, bottom Design-View tagging/switching toolbar, footer narrow-toggle + Tail-button + Prune; `footer_bar` pure module + `footer_bar_tests`; `ActionCluster::Tagging`/`Switching` in `action_bar`), Phase L L5 (dock-panel button refinements: top-bar overflow menu for Batch Items/Batch Razor/Capture RT via `overflow_menu` pure module; custom LICE-kit hover-delay tooltips via `tooltip` pure module; four opposite-mode Item/Track tag buttons + Show Both on the bottom toolbar; Toggle + Activate-Arrange/Design buttons removed; grouping spacing widened — `mode_enable` pure opposite-mode enablement predicate), Phase L L6 (toolbar polish: single-row short-label button faces — keybinding micro sub-row removed from `ActionBarSlot`, keybinding now shown in hover tooltip as "`phrase — binding`"; Cancel RT moved from visible bar into the overflow menu — More (⋯) now lists Batch Items / Batch Razor / Capture RT / Cancel RT; visible top-bar cluster order Capture → Maintenance → Placement; toolbar height 40→28 px), Phase L L7 (capture ordering, card metadata, and selection styling: per-bank `SlotMap` (id→slot) in `bank_book` — gap-preserving persisted display order, `reorderSample`/`replaceSample`/`orderedSampleIds`/`reconcileSlots` mutators; `captureTimeSigNum`/`captureTimeSigDenom` stamped on `Sample` at capture via `TimeMap_GetTimeSigAtTime`; `card_drag` pure module — gesture precedence + SWELL stock cursor cues; `card_meta` pure module — bars.beats.subdivisions + s.ms formatters; `bank_panel` sparse-grid rendering with gap cells, drop dispatch + cursor cues, metadata overlay, tertiary-border selection), and Phase S (S1–S18 complete; S13 cross-artifact relay deferred): VST3 sampler instrument `reasampler_9000.vst3` — voice engine (`sampler_core`), zone payload (`sample_map`), pitch-preserve OLA (`pitch_shift`), bank change-detection (`bank_sync`), IPC bridge (`bridge_marshal`), editor UI modules (`editor_geometry`, `keyboard_strip`, `waveform_view`, `capture_browser`, `browser_scroll`, `note_entry`, `param_slider`, `embed_strip`), VST3 shells (`reasampler_processor`, `reasampler_editor`, `reasampler_embed`, `reaper_bridge` READ-ONLY bank consumer, `vst_entry`); extension additions: `instrument_drop` pure FX-button blob builder (S17), `assignment_request` pure ingest-assign wire (S8), `ingest` shell (S8: docked-panel drop → capture/import + assign), `instrument_drop_win` shell (S17: `TrackFX_AddByName` + vst_chunk inject, rollback on fail); `drag_out` extended with `InstrumentDrop` third gesture; S18 channel isolation forks VST3 binary to `reasampler_9000_beta.vst3` alongside the beta extension have all landed. M9 slots deferred indefinitely. The *discipline* — pure REAPER-free testable core split from REAPER-facing shells — is **preserved** throughout.

CONTEXT.md is the authoritative spec and build roadmap. Read it first for any non-trivial task. Every REAPER API name cited there is correct-by-intent; verify argument order, types, and flag values against `vendor/reaper-sdk/sdk/reaper_plugin_functions.h` before use.

## One-time submodule setup

    git submodule update --init

Vendors three submodules (see `.gitmodules`):
- `vendor/reaper-sdk` — `sdk/reaper_plugin.h`, `sdk/reaper_plugin_functions.h`, SWELL headers
- `vendor/WDL` — WDL utilities and the SWELL cross-platform Win32 layer
- `vendor/vst3sdk` — Steinberg VST3 SDK (Windows-only; requires a nested init after the top-level init):

      git submodule update --init vendor/vst3sdk
      cd vendor/vst3sdk && git submodule update --init pluginterfaces base public.sdk

  The VST3 target (`reasampler_vst`) is gated on `EXISTS .../pluginfactory.cpp` — configure quietly omits it if the slice is absent.

## Build and test

    cmake -B build -S .
    cmake --build build
    ctest --test-dir build

Key targets (see CMakeLists.txt for the full list):

| Target | Kind | Purpose |
|---|---|---|
| `bank_model_tests` | executable | Pure unit tests for `bank_model` — no REAPER, no DAW. |
| `peaks_tests` | executable | Pure unit tests for `peaks` — no REAPER, no DAW. |
| `capture_paths_tests` | executable | Pure unit tests for `capture_paths` — no REAPER, no DAW. |
| `view_mode_model_tests` | executable | Pure unit tests for `view_mode_model` — no REAPER, no DAW. |
| `view_tree_tests` | executable | Pure unit tests for `view_tree` — no REAPER, no DAW. |
| `mode_switch_tests` | executable | Pure unit tests for `mode_switch` — no REAPER, no DAW. |
| `bank_book_tests` | executable | Pure unit tests for `bank_book` — no REAPER, no DAW. |
| `wav_trim_tests` | executable | Pure unit tests for `wav_trim` — no REAPER, no DAW. |
| `owned_manifest_tests` | executable | Pure unit tests for `owned_manifest` — no REAPER, no DAW. |
| `app_version_tests` | executable | Pure unit tests for `app_version` — no REAPER, no DAW. |
| `provenance_tests` | executable | Pure unit tests for `provenance` — no REAPER, no DAW. |
| `prune_reconcile_tests` | executable | Pure unit tests for `prune_reconcile` — no REAPER, no DAW. |
| `prune_button_tests` | executable | Pure unit tests for `prune_button` — no REAPER, no DAW. |
| `batch_capture_tests` | executable | Pure unit tests for `batch_capture` — no REAPER, no DAW. |
| `action_buttons_tests` | executable | Pure unit tests for `action_buttons` — no REAPER, no DAW. |
| `drag_out_tests` | executable | Pure unit tests for `drag_out` — no REAPER, no DAW. |
| `theme_tests` | executable | Pure unit tests for `theme` — no REAPER, no DAW. |
| `component_geometry_tests` | executable | Pure unit tests for `component_geometry` — no REAPER, no DAW. |
| `action_bar_tests` | executable | Pure unit tests for `action_bar` — no REAPER, no DAW. |
| `footer_bar_tests` | executable | Pure unit tests for `footer_bar` — no REAPER, no DAW. |
| `overflow_menu_tests` | executable | Pure unit tests for `overflow_menu` — no REAPER, no DAW. |
| `mode_enable_tests` | executable | Pure unit tests for `mode_enable` — no REAPER, no DAW. |
| `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. |
| `instrument_drop_tests` | executable | Pure unit tests for `instrument_drop` (S17 FX-button blob) — no REAPER, no DAW. |
| `assignment_request_tests` | executable | Pure unit tests for `assignment_request` (S8 ingest-assign wire) — no REAPER, no DAW. |
| `sampler_core_tests` | executable | Pure unit tests for `sampler_core` (VST3 voice engine) — no REAPER, no DAW. |
| `editor_geometry_tests` | executable | Pure unit tests for `editor_geometry` (VST3 editor layout) — no REAPER, no DAW. |
| `bridge_marshal_tests` | executable | Pure unit tests for `bridge_marshal` (bridge read-decode) — no REAPER, no DAW. |
| `embed_strip_tests` | executable | Pure unit tests for `embed_strip` (VST3 embed layout, S6) — no REAPER, no DAW. |
| `sample_map_tests` | executable | Pure unit tests for `sample_map` (VST3 zone payload v5) — no REAPER, no DAW. |
| `capture_browser_tests` | executable | Pure unit tests for `capture_browser` (VST3 capture browser, S10) — no REAPER, no DAW. |
| `keyboard_strip_tests` | executable | Pure unit tests for `keyboard_strip` (VST3 keyboard strip) — no REAPER, no DAW. |
| `waveform_view_tests` | executable | Pure unit tests for `waveform_view` (VST3 waveform view) — no REAPER, no DAW. |
| `bank_sync_tests` | executable | Pure unit tests for `bank_sync` (VST3 generation change-detection, S9) — no REAPER, no DAW. |
| `browser_scroll_tests` | executable | Pure unit tests for `browser_scroll` (VST3 browser scroll, S12) — no REAPER, no DAW. |
| `note_entry_tests` | executable | Pure unit tests for `note_entry` (VST3 note entry, S12) — no REAPER, no DAW. |
| `param_slider_tests` | executable | Pure unit tests for `param_slider` (VST3 param slider, S12) — no REAPER, no DAW. |
| `reaper_reasampler` | loadable module | The REAPER extension binary (`.dll` / `.dylib` / `.so`). |
| `reasampler_vst` | loadable module | The VST3 sampler instrument (`reasampler_9000.vst3`); Windows-only, omitted if `vendor/vst3sdk` slice is absent. |

### Beta channel build (Phase V, V4)

To build the fully isolated beta binary (`reaper_reasampler_beta`), pass the channel flag at configure time:

    cmake -B build-beta -S . -DREASAMPLER_CHANNEL=beta
    cmake --build build-beta

The flag threads through `configure_file` → `version_generated.h` and fans out via `app_version` into the binary name, ext-state namespace (`"reasampler_beta"`), command-id prefix (`CEREBELLUM_REASAMPLER_BETA_`), action-name prefix (`"ReaSampler beta: "`), dock ident, and version display (`"0.9.01-beta"`). The default build (no flag) is byte-identical to the pre-V4 stable identity.

The VST3 target forks identically (S18 channel isolation): `REASAMPLER_CHANNEL=beta` produces `reasampler_9000_beta.vst3`; the default produces `reasampler_9000.vst3`. The beta VST pairs **only** with the beta extension — each channel carries its own per-channel VST3 class UID, preventing a saved instance from rebinding across channels.

### macOS / Linux: SWELL dialog resources

`src/resource.rc` must be pre-processed by SWELL's resgen once per platform:

    php vendor/WDL/WDL/swell/mac_resgen.php src/resource.rc   # macOS; Linux reuses the output

Add the generated file to the appropriate `APPLE` / Linux `target_sources` block in CMakeLists.txt. The SWS extension build is the canonical reference for this step.

### Install / reload

There is no hot-reload. Copy the built binary into REAPER's `UserPlugins/` folder (Options → Show REAPER resource path) and restart REAPER. Extensions load at startup only.

## Architecture: the load-bearing split

**Pure core (no REAPER types, unit-testable outside the DAW):**
- `bank_model` — `Sample` metadata struct + `BankIndex` (add/remove/query/tier/dedup-by-hash + JSON round-trip). Test it hard — it is the heart. `Sample` carries `captureTimeSigNum`/`captureTimeSigDenom` (L7: stamped at capture via `TimeMap_GetTimeSigAtTime`, refreshed on re-capture).
- `peaks` — waveform min/max bin computation from raw PCM. Fed a known signal, asserts envelope. Does not depend on REAPER's peak API.
- `view_mode_model` — Design View mode system: mode registry, GUID-keyed membership, folder-tree-aware visibility derivation, snapshot-based park/restore planner, JSON round-trip. Mirror of `bank_model` for the Design View phase.
- `view_tree` — pure `I_FOLDERDEPTH`→FolderTree helper for the Design View shell; no REAPER types at the boundary.
- `mode_switch` — REAPER-free segment layout + hit-test math for the bank_panel's Design View mode switch; divides a header rectangle into N equal segments and hit-tests a point to a segment. Mirror of `bank_grid`.
- `bank_book` — multi-bank registry (Phase B): an ordered set of banks (pool seeded as bank-zero + named banks), each wrapping a `BankIndex`. Owns create/rename/reorder/delete of named banks, pool privileges (un-deletable/un-renamable/un-evacuable, never zero banks) enforced in-model, active-bank id, index-only move/copy/remove of a sample between or from banks, `hashReferencedElsewhere` cross-bank reference query, JSON round-trip + legacy-`bank_index`→pool migration. Wraps `BankIndex` (bank_model untouched; no `bankId` on `Sample`). L7 adds: per-`Bank` gap-preserving **`SlotMap`** (id→slot) for deterministic display order — persisted inside the existing `"banks"` blob; `reorderSample` (insert-before-shift; same-slot = no-op), `replaceSample` (occupant index-removal via standard remove path + pool-guard inheritance; no-op on reject), `orderedSampleIds`, `reconcileSlots` (pre-L7 migration seeds dense insertion order on load).
- `owned_manifest` — owned-file manifest seam (Phase B B-cap): the set of project-relative files the capture path itself created, persisted under the `"owned_files"` ext-state key, so Phase R prune can distinguish the bank system's own orphans from hand-dropped files. Deliberately decoupled from `bank_book` — tracks files created, not index membership. Phase R (R1/R2) consumes it; no prune logic here.
- `app_version` — REAPER-free version/channel identity (Phase V, V1+V4): CMake-sourced semver constant (`appVersion()`), ext-state stamp value (`stampVersion()` — numeric triple only, no channel suffix), `parseVersion`/`versionLess`/`classifyWritingVersion`, and the full set of channel-derived identity accessors (`extStateNamespace()`, `commandIdPrefix()`, `actionDisplayPrefix()`, `binaryName()`, `dockTitle()`, `dockIdent()`, `channelCommandId()`, `channelActionName()`). All channel strings derive from the one `REASAMPLER_CHANNEL_IS_BETA` bit threaded in via `configure_file` → `version_generated.h`; no scattered `#ifdef`s in the shells.
- `wav_trim` — 32-bit-float WAV parse + header-aware truncate plan (RIFF/data size rewrite) for the realtime tail's PCM decay-scan trim (T2). Rejects WAVE_FORMAT_EXTENSIBLE with non-float SubFormat GUID. Depends on `peaks` for the `AudioSample` float alias.
- `provenance` — capture-recipe fingerprint (M10): build/encode/compare a `rsprov1` length-prefixed fingerprint of scope, exact range, tail, rate/channels, track GUIDs, and order-sensitive FX-chain identity; parse/compare for drift detection on re-capture. A thin reproducibility fingerprint — NOT a serialized chain to restore. Drives `BankIndex::updateInPlace` / `BankBook::updateSampleInPlace` (order-preserving, id-stable) on re-capture.
- `prune_reconcile` — Phase R pure prune core: `pruneOrphans(present, referenced, owned)` computes `(owned ∩ present) − referenced` (exact-string path match); `buildPruneReport` tallies count/bytes/display-capped file list; `pruneDeletePlan` produces the confirm-time staleness intersection (`confirmed ∩ freshOrphans`). REAPER-free, filesystem-free. The safety-critical "which files are orphans" decision — hard-tested here before any I/O exists. Also: `BankBook::referencedPaths()` additive const union query (all banks incl. pool, de-duped) added to `bank_book`.
- `prune_button` — Phase R pure layout/hit-test for the `bank_panel` footer Prune button: `computePruneButton` (right-anchored, suppressed gracefully when footer is too narrow) + `hitTestPruneButton`. Mirror of `mode_switch` / `tab_strip`.
- `batch_capture` — M11 pure batch-capture planner: maps a list of source ranges to ordinal capture units, drives per-unit capture via a shared `captureAndIndexOne` helper, and aggregates mixed results. No REAPER types at the boundary.
- `action_buttons` — M11 pure action-button strip layout/hit-test: divides a strip rect into N action buttons, min-width overflow-hiding, label formatting with "(unbound)" fallback, `ActionButtonRect` struct. Mirror of `mode_switch` / `bank_grid`.
- `drag_out` — M11 pure OS drag-out module: gesture-boundary decision (internal drag becomes OS-bound when the pointer leaves the panel client rect), path-list assembly with dedupe and missing-file skip. S17 adds a third gesture `InstrumentDrop`: pointer is outside the panel but still over the REAPER UI, and exactly one sample is selected — signals that the shell should execute an instrument-drop rather than a file-copy drag. No REAPER types at the boundary.
- `theme` — Phase L pure palette module (L1): role→color mapping via one constants block (DS-2 revised — REAPER-grey neutral ladder: `bg/base #2b2b2b` / `bg/panel #333333` / `bg/cell #3a3a3a` / `line/hairline #4a4a4a` / `text/primary #dcdcdc` / `text/dim #a8a8a8`; three-accent pastel system: `accent/primary` pastel lime `#B0E098` = live/active/selected, `accent/secondary` pastel teal `#84D6D0` + `accent/tertiary` pastel purple `#C2AAE8` = categorical distinctions, `accent/hot` lighter lime = hover/drag feedback); `Role` enum carries the three accent roles; `roleColor`/`roleColorState` updated (Active/Dragging/Focus → primary accent); `spectralColor` is a pastel three-stop sweep anchored on the three accents (lime → teal → purple); WCAG contrast-floor helpers; full interaction-state color model. No LICE or REAPER types.
- `component_geometry` — Phase L pure component geometry/hit-test helpers (L1): button/slider/list-row geometry + hover hit-test. No LICE or REAPER types. Mirror of `mode_switch`/`bank_grid`.
- `action_bar` — Phase L pure task-grouped action-bar layout/hit-test (L2 + L4): clusters (Capture / Placement / Maintenance / Tagging / Switching), per-button label rects, whole-trailing-button overflow, point→index hit-test. `ActionCluster::Tagging` and `ActionCluster::Switching` added in L4 for the bottom Design-View toolbar. No LICE or REAPER types. Mirror of `mode_switch`/`bank_grid`/`action_buttons`.
- `footer_bar` — Phase L pure footer layout/hit-test (L4): narrow `[Arrange|Design]` mode-toggle geometry + per-mode count label, Tail button, and Prune placement in the panel footer strip. No LICE or REAPER types. Mirror of `mode_switch` / `prune_button`.
- `overflow_menu` — Phase L pure overflow-menu-button geometry/reserve/hit-test (L5): right-anchored More (⋯) button rect computation and hit-test for the top-toolbar overflow. No LICE or REAPER types. Mirror of `prune_button`.
- `mode_enable` — Phase L pure opposite-mode enablement predicate (L5): given the active mode, computes per-button live/disabled state for the four Item/Track × Arrange/Design tag buttons on the bottom toolbar. No LICE or REAPER types.
- `tooltip` — Phase L pure tooltip placement + prefix-strip (L5): custom LICE-kit hover-delay tooltip geometry and text derivation — strips the `ReaSampler:` display prefix from the registered action phrase; tooltip box width clamped to the client rect. No LICE or REAPER types.
- `card_drag` — Phase L pure drag-gesture precedence + slot hit-test (L7): leave-client → OS drag-out; other-bank → move/copy; same-bank → reorder / Alt-over-occupied → replace. Returns the resolved gesture so the shell can map it to a SWELL stock cursor cue. Sparse `computeSlotRects` / `hitTestSlot`. No LICE or REAPER types. Mirror of `drag_out` / `prune_button`.
- `card_meta` — Phase L pure card-metadata formatters (L7): bars.beats.subdivisions from `lengthSeconds` + `captureTempo` + capture-time-signature stamp; seconds.milliseconds rounded. Both blank when the sample is unstamped. No LICE or REAPER types.
- `instrument_drop` — Phase S pure FX-button drop blob builder (S17): constructs the base64-encoded vst_chunk blob needed to inject a pre-configured `reasampler_9000` instrument via `TrackFX_AddByName` + chunk inject; reuses the VST3 serializer. All-or-nothing contract — caller rolls back via `TrackFX_Delete` on any failure. No REAPER types at the boundary.
- `assignment_request` — Phase S pure ingest-assign wire (S8): typed request record carrying the drop payload (file path, zone assignment hint) from the `ingest` shell through to the VST3 bridge. No REAPER types at the boundary.

**REAPER-facing shells:**
- `capture` — `ICaptureBackend` interface; `OfflineRenderBackend` (deterministic default) and `RealtimeRecordBackend`. Input: `CaptureRequest`. Output: finished file + populated `Sample` handed to `bank_model`.
- `insert` — placement via `InsertMedia`; conform-to-project-tempo is an explicit opt-in flag, never silent stretching.
- `bank_panel` — docked LICE-drawn grid: thumbnails, audition, multi-select, keyboard navigation; three-zone layout (L4/L5/L6): **top toolbar** = visible bar in cluster order Capture (Capture Item, Capture Track) → Maintenance (Re-capture) → Placement (Insert, Insert Conform) via `action_bar`, each button showing a single-row short label, firing via `NamedCommandLookup` + `Main_OnCommand`; a right-anchored **More (⋯) overflow menu button** (`overflow_menu`) opens a `TrackPopupMenu` listing Batch Items / Batch Razor / Capture RT / Cancel RT; **hover tooltips** (`tooltip`) show the full action name with the `ReaSampler:` prefix stripped plus the live keybinding ("`phrase — binding`" when bound, bare phrase when unbound), sourced from the registered action phrase + `kbd_getTextFromCmd`; toolbar height 28 px; **bottom toolbar** = four opposite-mode tag buttons (Item: Arrange / Item: Design / Track: Arrange / Track: Design — live only for the opposite of the active mode, `Disabled` otherwise via `mode_enable`) + set-apart Show Both (`VIEW_SHOW_BOTH`); Toggle and Activate-Arrange/Activate-Design buttons removed (actions stay registered); grouping `clusterGap` 24 / `buttonGap` 4; **footer** = narrow `[Arrange|Design]` toggle · per-mode count · Tail button (cycles tail on click, proper kit button states) · set-apart `warn` Prune (rightmost) via `footer_bar`; entire panel draws through the L1 kit by palette role with hover on interactive elements, single `KitColor→LICE_pixel` boundary via `draw_kit`; OS drag-out hook (M11) initiating an OS-level copy drag when the pointer leaves the panel client rect, via `drag_out` + `drag_out_win`. L7 adds: **grid renders in sparse slot order** (decorative empty-gap cells for unoccupied slots; every cell↔sample consumer remapped to id-based occupied-ordinal space — selection, keyboard nav with gap-skip arrows, audition, multi-select, delete/re-capture resolution, drags); **drop dispatch** (reorder / Alt-replace / move-copy) with one-Ctrl-Z undo, per-slot drop highlight (`accent/hot`, doubled outline for replace), SWELL stock cursor cues via `SetCursor` per the `card_drag` resolved gesture; **metadata overlay** (bars.beats bottom-left Micro, s.ms bottom-right ValueMono, `TextDim`, decorative); **selection = normal cell + `accent/tertiary` purple border**, inversion removed, focus ring distinct.
- `persist` — project ext state (`SetProjExtState` / `GetProjExtState`, namespace `"reasampler"`) ↔ `BankBook` JSON (`"banks"` key — L7: per-`Bank` `SlotMap` rides inside this blob; a pre-L7 blob with no slot data migrates via `reconcileSlots()` to dense insertion order on load) + `ViewModeModel` JSON (`"view_state"` key) + `TailSetting` JSON (`"tail_setting"` key) + `OwnedManifest` JSON (`"owned_files"` key) + writing-version stamp (`"version"` key, written via `stampVersion()` on every `saveToActiveProject()`); project-relative path resolution. A `projectconfig` hook (`BeginLoadProjectState(isUndo)`) triggers a deferred session reload on undo/redo so Ctrl-Z/redo visibly restores book/view/tail/manifest in-session. Hosts `ReaSamplerSession::pruneDryRun()` (read-only orphan enumeration via M4 project-relative resolution) and `pruneOrphanSet()` (full-set query for the R3 delete path); supplies `referencedPaths()` + `owned().paths()` to the `prune_reconcile` pure core.
- `view` — Design View shell: reads the folder tree via `view_tree`, snapshots flag values before parking, drives hide + CPU-park on inactive-mode leaves (`B_SHOWINTCP`/`B_SHOWINMIXER`/`B_MAINSEND`/`I_FXEN` + per-FX offline) and derived visibility on parents; restores from snapshot. Never touches master or `B_MUTE`/`I_SOLO`.
- `track_guid` — shared `MediaTrack*` → canonical GUID-string formatter; single source of truth for membership keys used by both the view shell and the actions layer.
- `provenance_shell` — FX-chain identity queries via `TrackFX_*` / `TakeFX_*` APIs; collects source-item paths and parent-detection inputs to feed the pure `provenance` fingerprint builder. Stamps `Sample.provenance` on capture when every resolving source item maps by exact normalized path (case-folded on Windows) to exactly one bank sample; ambiguous/mixed cases record nothing conservatively.
- `drag_out_win` — M11 OS drag-out shell: Windows OLE `DoDragDrop` / `CF_HDROP`, copy-only structurally (`DROPEFFECT_MOVE` not offered, no source-deletion path); macOS/Linux via `SWELL_InitiateDragDropOfFileList` (copy-semantics caveat documented — SWELL does not expose a drop-effect query). Driven by the `drag_out` pure module.
- `ingest` — Phase S ingest-through-the-bank shell (S8) on the EXTENSION side: three surfaces — (1) arrange capture→bank→assign (bindable action), (2) Media-Explorer import→bank→assign (bindable action, single-file via `MediaExplorerGetLastPlayedFileInfo`), (3) file drop onto the bank panel→bank→assign (multi-file, assigns the first). All three write the `assignment_request` ext-state wire; ingest NEVER inserts a timeline item.
- `instrument_drop_win` — Phase S FX-button drop shell (S17): (a) resolves a screen point to a track + its TCP FX-button hotspot via REAPER's hit-test API (`GetThingFromPoint`, `TrackFX_*`), and (b) on release adds a ReaSampler 9000 instance to that track and injects the dragged capture as its component state via `TrackFX_SetNamedConfigParm` "vst_chunk"; wraps the whole operation in one REAPER undo block. Never captures, never writes the bank, never inserts a timeline item.
- `draw_kit` — Phase L shared LICE draw shell (L1): `fillSurface` (micro-gradient + inner highlight/shadow), `drawButton`/`drawSlider`/`drawListRow`/`drawWaveform`, cached-font `text()` over four `LICE_CachedFont`s (kit-owned lifecycle), full interaction-state model, double-buffer preserved. Consumes `theme` + `component_geometry`. First consumer: `bank_panel` (GDI `DrawText` path retired in L1).
- `actions` — registers the capture/placement/slot action family, the Design View action family (toggle active mode, activate Arrange/Design, tag/untag selected tracks, show-both), the multi-bank action family (create/rename/reorder/delete bank, evacuate, activate, move/copy/remove selected samples), and the Phase R prune action (`BANK_PRUNE_FOLDER` — dry-run-first, confirm-with-manifest, then `pruneDeletePlan`-guarded deletion; **the ONLY file-deletion authority in the system**); routes each to the modules above via the `command_id`/`gaccel`/`hookcommand` contract. Every bank index verb wraps its mutation in a batched REAPER undo point (`Undo_BeginBlock2`/`EndBlock2`, `UNDO_STATE_MISCCFG`) so one bank operation is one Ctrl-Z. The prune action writes no ext state and opens no undo point (file deletion is not REAPER-undoable).

**VST3 instrument (`src/vst/`) — pure core:**
- `sampler_core` — Phase S voice engine (S1–S16): polyphonic voice allocation with bounded stealing; per-zone `ZonePlayParams` (PlayMode Gate/Trigger, AHDSR envelope times in frames, Trigger %-length + fades, pitch engine Varispeed/Preserve, AD pitch modulation envelope); repitch/interpolation from a root note with loop-point-aware sustain; no file I/O. No REAPER types at the boundary.
- `sample_map` — Phase S zone payload v5 (S3): zones keyed by note range; **wall-clock times stored as rate-free SECONDS, resolved against the live project rate — NO hardcoded sample rates in `src/`** (Daniel's standing ruling, load-bearing). JSON round-trip.
- `pitch_shift` — Phase S OLA pitch-preserve engine (S16): hand-rolled overlap-add pitch shifter for the Preserve playback mode; no third-party dependencies. No REAPER types at the boundary.
- `bank_sync` — Phase S generation change-detection + assignment-request consume (S9/S8): owns the yes/no decision logic — parses the generation stamp, decides whether it differs from what was last seen, decides whether a decoded assignment request is new-and-resolvable-and-worth-applying. The processor shell owns the cadence and side effects (reloadFromBank, setSelectedSampleId); this module owns only the maths so the rules are provable without a host. No REAPER types at the boundary.
- `bridge_marshal` — Phase S pure marshalling helper for the REAPER VST-host bridge read (S7): interprets the `GetProjExtState` int return against its filled buffer — the read-decode arithmetic split out of the `reaper_bridge` shell. The S1 string-scan JSON reader was retired in S4 when the instrument moved to the shared bank_book/bank_model JSON path. No IPC, no shared memory. No REAPER types at the boundary.
- `editor_geometry` — Phase S VST3 editor layout pure module (S1): defines the shared `Rect` type + `contains()` hit-test used across all editor geometry modules; provides the spike editor's `EditorLayout` (titleBar / button / canvas) and `layoutEditor(w,h)`. No REAPER or VST3 types at the boundary.
- `keyboard_strip` — Phase S piano-keyboard strip pure module: MIDI-note→key rect mapping, black/white key layout, hit-test, zone highlight overlay geometry. No REAPER or VST3 types at the boundary.
- `waveform_view` — Phase S waveform/marker geometry pure module (S11): maps a sample's full frame span [0, frameCount] linearly across a horizontal rect; generic named draggable markers (start, loop start, loop end) with drag-delta resolver, clamp, and zero-crossing snap. No REAPER or VST3 types at the boundary.
- `capture_browser` — Phase S capture browser pure module (S10): card-grid layout + bank-filter tab strip geometry and hit-test; knows only counts and rects — holds no sample data, draws nothing. Scroll is NOT here (S12 layers it over this module via `browser_scroll`). No REAPER or VST3 types at the boundary.
- `browser_scroll` — Phase S scroll + type-to-filter pure module (S12) layered over `capture_browser`: vertical scroll offset, max-offset clamp, visible-row window, scrollbar thumb rect, thumb-drag↔offset mapping; AND name-substring search (case-insensitive, composing with the bank filter). No REAPER or VST3 types at the boundary.
- `note_entry` — Phase S note-entry pure module (S12): parses a raw string into a clamped MIDI note [0,127] for zone low/high/root note editing; accepts plain decimal integers or note names (C4==60, DAW convention); out-of-range clamps, unparseable returns nullopt. No REAPER or VST3 types at the boundary.
- `param_slider` — Phase S parameter control-panel pure module (S12): lays out a vertical stack of fixed-height control rows in two shapes — TOGGLE (two-segment selector) and SLIDER (horizontal track with draggable 0..1 handle); maps normalized value to/from handle pixel; the shell owns domain-value conversion and control-id→engine-param binding. No REAPER or VST3 types at the boundary.
- `embed_strip` — Phase S embed-mode strip layout pure module (S6): compact single-row control layout for when the editor is embedded in the track FX chain. No REAPER or VST3 types at the boundary.

**VST3 instrument (`src/vst/`) — shells:**
- `reaper_bridge` — Phase S READ-ONLY bank consumer (S7): receives bank snapshots from the extension over the IPC bridge and exposes them to the VST3 processor/editor as a read-only view. **Never writes to the extension's bank** — this is a load-bearing invariant; no mutation path exists in this module.
- `reasampler_processor` — Phase S VST3 `SingleComponentEffect` shell: declares an event-input bus + stereo audio output bus, marshals host MIDI note-on/off into the VoiceEngine, renders audio via the loaded `sample_map` zones; owns the off-audio-thread `reloadFromBank` + atomic pointer swap so process() does no allocation, no file I/O, no bridge calls.
- `reasampler_editor` — Phase S VST3 `IPlugView` LICE editor shell (S10): subclasses `CPluginView`, hosts a LICE-drawn child window inside the host's IPlugView seat; default face is the capture browser (bank-filter tabs + card grid), then single-capture setup (keyboard strip + root marker), with opt-in zones panel (S10-Z). Accepts file drops and shows a drop affordance (S13 relay to the extension's ingest path is deferred — drop-onto-editor ingest is NOT shipped).
- `reasampler_embed` — Phase S embed shell (S6): implements `IReaperUIEmbedInterface` so the instrument draws a compact keymap/level strip INLINE in the track/mixer control panel (TCP/MCP), without a plugin-owned HWND — REAPER hands a LICE bitmap per paint; delegates layout/hit-test to `embed_strip`.
- `vst_entry` — Phase S VST3 entry point: `GetPluginFactory` export, class registration, channel-forked class UIDs (S18).

## REAPER extension contract (src/main.cpp)

- Exactly **one** translation unit defines `REAPERAPI_IMPLEMENT` — that is `main.cpp`. Every other `.cpp` includes `reaper_plugin_functions.h` without the define and gets `extern` declarations for the global API function pointers.
- REAPER dlopen()s any `reaper_*.dll|dylib|so` found in `UserPlugins/` and calls the `ReaperPluginEntry` export (produced by `REAPER_PLUGIN_ENTRYPOINT`). `rec->GetFunc` resolves API pointers; `rec->Register` plugs extension callbacks in.
- Action registration pattern (preserve this for all new actions):
  1. `rec->Register("command_id", (void*)"STABLE_FOREVER_STRING")` — mints a persistent command id. **Never change this string after shipping**; user keybindings key off it. Since Phase V (V4), ids and display names are composed via `channelCommandId(suffix)` and `channelActionName(phrase)` from `app_version` — the FOREVER-STABLE contract applies per channel (stable and beta each have their own permanent id family).
  2. `rec->Register("gaccel", &accel)` — puts the action in the Actions list.
  3. `rec->Register("hookcommand", ...)` — receives every action fired; claim only your own id, return `false` otherwise.
  4. On unload (`rec == nullptr`), mirror-unregister everything with the same strings prefixed by `'-'`.

## The load-bearing principle

**Capture and placement are separate acts.** Capturing audio writes a file to the bank and adds an index entry. It **never** puts an item in the arrange view. Placement is a distinct, on-demand action (`insert` module / `InsertMedia`). Any code path that auto-inserts a capture into the timeline violates the purpose of the tool and **must be rejected in review**.

## Precision invariants — required before any feature ships

- **Null test:** a dry offline capture of a range, re-inserted at its source position, nulls to silence against the source. Ship as a verification action.
- **Bit-identical repeats:** identical offline capture requests produce identical files.
- **Non-destructive:** capture never mutates source items or tracks; the realtime backend's temp track is created and removed cleanly, and source routing is restored.
- **Exact bounds:** no rounding of the requested range; no added silence unless a tail is explicitly requested; channel count preserved (no silent stereo fold).
- **Relative paths only** in the persisted `BankIndex`.
- **Capture FX scope:** two scopes only — item = item/take FX only; track = item FX + the selected track's own track FX. There is no master scope (to capture the master, render a track instead). For both scopes, the out-of-scope chain (ancestors + master track, plus the item's own track for item scope) has its FX, gain, and pan/width/pan-law/mode neutralized to unity — the master track is bypassed as out-of-scope chain, not captured as a scope. Range (time selection or razor) is orthogonal.