fix: close review findings on the velocity-curve deck and bipolar curves

Cancels the curve-node drag whenever the popup closes so Esc mid-drag can't alias the amp curve; generalizes CurveTarget routing to one switch; fixes stale/overstated comments; clamps a pre-v12 depth fold; adds deck-inertness and filter-fold test coverage.

src/core/instrument/CLAUDE.md

@@ -262,7 +262,7 @@ anything for a trigger shape.
   - `voice_engine.h` / `voice_engine.cpp` — `VoiceEngine`: note routing, bounded-stealing allocation, user-parameterized voice count (1–32, default 16), `VoiceMode` Poly/Mono (last-note held-note stack, `MonoTrigger` Retrigger/Legato), two-tier panic (CC 123 = all-notes-off release, CC 120 = immediate hard-stop including Trigger one-shots), and the block render loops. Preview injects a synthetic note-on at the loaded capture's root note into the main `VoiceEngine` — no dedicated `PreviewCard`; preview obeys polyphony/mono/voice-stealing/envelopes.
 - `engine/loop/` — the sustain loop's ONE validity/clamp fold (`resolveLoop`) plus its pre-seam crossfade geometry and the editor's default handle span; see `engine/loop/CLAUDE.md`. The voice folds it once at note-on; the crossfade weight is header-inline because it rides the per-sample read.
 - `pitch_shift` — hand-rolled **correlation-aligned SOLA** (splice-overlap-add) pitch shifter for the Preserve playback mode: one active read tap chases the write head at the shift ratio; each splice jump is refined by a cross-correlation search so the new read point is waveform-aligned, then old and new taps are crossfaded (raised-cosine, amplitude-complementary). Replaces the prior dual-tap OLA whose fixed half-window tap offset caused anti-phase cancellation on many source frequencies. **GA2:** ring buffer **primed with the actual upcoming source** at note-on (was zero-filled) → gap-free frame-0 onset, ~25 ms Preserve onset latency eliminated (Preserve now speaks on frame 0, matching Varispeed), and real-content-bounded tail (last-window tail-truncation gone). No third-party dependencies; RT-discipline: no allocation in `process()`.
-- `velocity_curve` — the pure velocity transfer curve shared by all THREE destinations: `VelocityCurve` evaluated by a Fritsch–Carlson monotone cubic Hermite spline (no overshoot). `eval(velocity)` called once per note-on. It carries its own y `CurveDomain`: UNIPOLAR [0,1] is the amp's GAIN, defaulting to `flat()` (y=1, every velocity→unity — a deliberate non-back-compat replacement of the old fixed `velocity/127` path, Daniel-approved); BIPOLAR [−1,1] is the signed modulation depth for pitch and filter, defaulting to `zero()` so velocity modulates neither until a curve is drawn. A bipolar curve is BOTH the shape and the amount — there is no depth control behind it, which is why the filter's `velAmount` retired into it. eval is HOMOGENEOUS in y (scaling every knot by k scales the curve by k exactly); the codec's pre-v12 lift rests on that.
+- `velocity_curve` — the pure velocity transfer curve shared by all THREE destinations: `VelocityCurve` evaluated by a Fritsch–Carlson monotone cubic Hermite spline (no overshoot). `eval(velocity)` called once per note-on. It carries its own y `CurveDomain`: UNIPOLAR [0,1] is the amp's GAIN, defaulting to `flat()` (y=1, every velocity→unity — a deliberate non-back-compat replacement of the old fixed `velocity/127` path, Daniel-approved); BIPOLAR [−1,1] is the signed modulation depth for pitch and filter, defaulting to `zero()` so velocity modulates neither until a curve is drawn. A bipolar curve is BOTH the shape and the amount — there is no depth control behind it, which is why the filter's `velAmount` retired into it. eval's homogeneity in y (see `velocity_curve.h`) is what the codec's pre-v12 lift rests on.
 - `master_gain` — pure dB↔linear taper math (FB1): normalized [0,1] ↔ dB ↔ linear for the post-mixer master gain control (−∞…+24 dB, norm 0 = true silence, unity ≈ 0.714). Shared by the editor knob and the processor multiply so the needle, persisted value, and audio multiply cannot drift.
 
 ### `map/`

src/core/instrument/engine/velocity_curve.cpp

@@ -43,7 +43,8 @@ int valueToY(const VelocityCurve::Box& box, double value, CurveDomain d) {
 
 VelocityCurve VelocityCurve::flat() {
     VelocityCurve c;
-    c.points_ = {{kVelMin, kCurveYMax}, {kVelMax, kCurveYMax}};
+    const double n = curveNeutral(CurveDomain::Unipolar);
+    c.points_ = {{kVelMin, n}, {kVelMax, n}};
     return c;
 }
 
@@ -56,7 +57,8 @@ VelocityCurve VelocityCurve::linear() {
 VelocityCurve VelocityCurve::zero() {
     VelocityCurve c;
     c.domain_ = CurveDomain::Bipolar;
-    c.points_ = {{kVelMin, 0.0}, {kVelMax, 0.0}};
+    const double n = curveNeutral(CurveDomain::Bipolar);
+    c.points_ = {{kVelMin, n}, {kVelMax, n}};
     return c;
 }
 

src/core/instrument/engine/velocity_curve.h

@@ -25,8 +25,10 @@ enum class CurveDomain { Unipolar, Bipolar };
 
 constexpr double curveYMin(CurveDomain d) { return d == CurveDomain::Bipolar ? -1.0 : 0.0; }
 
-// The value that changes nothing in each domain — unity gain, or zero modulation. Every
-// defensive fallback lands here so a corrupt blob loses the shaping rather than inventing one.
+// The value that changes nothing in each domain — unity gain, or zero modulation. THE one home
+// for that value: eval()'s own empty-curve fallback reads it directly, and flat()/zero() (what
+// fromPoints' sub-2-point fallback constructs) are built from it too, so a corrupt blob always
+// loses the shaping rather than inventing one, however the fallback is reached.
 constexpr double curveNeutral(CurveDomain d) { return d == CurveDomain::Bipolar ? 0.0 : 1.0; }
 
 // A raw-constructed point is NOT auto-clamped (the mutators own that invariant) — build curves
@@ -45,7 +47,10 @@ inline constexpr int kCurveNodeGrabRadius = 6;
 // slope, so the spline reproduces linear()'s straight line to within ~1e-15. The two endpoints
 // (velocity 0 and 127) are load-bearing: they keep eval total over the domain and are never
 // deletable. eval is HOMOGENEOUS in y — scaling every knot's value by k scales the whole curve
-// by k exactly, which is what lets the codec fold a retired depth control into stored knots.
+// by k TO WITHIN DOUBLE ROUNDING (the Hermite basis and the Fritsch-Carlson tangent are exactly
+// degree-1 homogeneous in real arithmetic; `fl(k*b) - fl(k*a)` isn't bit-identical to
+// `k*(b-a)`), which is what lets the codec (component_state_io.h's v12 pre-lift) fold a retired
+// depth control into stored knots and still sound identical.
 class VelocityCurve {
 public:
     // flat() (endpoints (0,1)/(127,1), every velocity -> unity) is the unipolar default — see
@@ -117,6 +122,12 @@ public:
     bool equals(const VelocityCurve& other, double eps = 1e-9) const;
 
 private:
+    // Private: an implicit-default curve is empty (no endpoints) and Unipolar, so a stray
+    // default-construction wouldn't fail loudly — it would eval() to unity gain everywhere,
+    // or a full +/-1 (a full-scale transpose / wide-open filter) if ever read as bipolar. Build
+    // through flat()/linear()/zero()/fromPoints(), all of which establish the endpoint invariant.
+    VelocityCurve() = default;
+
     // Always X-ordered with an endpoint at 0 and 127; constructors + deserialize establish the
     // invariant, mutators preserve it.
     std::vector<VelocityPoint> points_;

src/core/instrument/map/component_state_io.h

@@ -90,18 +90,21 @@ namespace reasampler::instrument::map {
 // prefix and lifts to 0 — the hard seam it always played.
 //
 // v12 (CURRENT WRITE FORMAT) is v11 PLUS the velocity->PITCH transfer curve (count + points,
-// the same shape as v7's), appended after the loop crossfade. It also RE-INTERPRETS two frozen
-// slots inside the v9 filter tail — the byte shape is untouched, only the meaning at v12+:
+// the same shape as v7's), appended after the loop crossfade. Its y is a normalized fraction
+// of kVelocityPitchRangeSemitones (play_params.h) — a full-scale constant that lives OUTSIDE
+// this frozen ladder, so retuning it re-tunes every saved v12 project's pitch-curve throw. It
+// also RE-INTERPRETS two frozen slots inside the v9 filter tail — the byte shape is untouched,
+// only the meaning at v12+:
 //   * the filter's velocity curve is now BIPOLAR [-1,+1] and is the whole velocity->cutoff
 //     amount, not a [0,1] shape scaled by a separate depth;
 //   * the retired filter velAmount slot is written as a constant 1.0 and ignored on read.
 // PRE-v12 LIFT: the stored [0,1] filter curve has every knot's y multiplied by that blob's
-// velAmount and is re-read as bipolar. eval is homogeneous in y, so the lifted curve evaluates
-// to exactly velAmount * oldCurve(v) — the product the voice used to compute per note — and a
-// pre-v12 project sounds identical. A pre-v12 blob carries no pitch curve at all and lifts to
-// the bipolar flat-at-zero default, which transposes nothing. A DOWNGRADE to a pre-v12 binary
-// reads the constant 1.0 depth against a curve whose negative half clamps away, so it
-// reproduces the curve's positive half only.
+// velAmount and is re-read as bipolar. eval is homogeneous in y to within double rounding (see
+// velocity_curve.h), so the lifted curve evaluates to velAmount * oldCurve(v) — the product the
+// voice used to compute per note — and a pre-v12 project sounds identical. A pre-v12 blob
+// carries no pitch curve at all and lifts to the bipolar flat-at-zero default, which transposes
+// nothing. A DOWNGRADE to a pre-v12 binary reads the constant 1.0 depth against a curve whose
+// negative half clamps away, so it reproduces the curve's positive half only.
 //
 // The two int64 slots the v5 play tail spends on the RETIRED Trigger fade pair are frozen in
 // shape and still read: a pre-v10 blob's fade-in/fade-out become the Trigger AHD that replaced

src/core/instrument/map/params_payload.cpp

@@ -140,8 +140,13 @@ void readFilterTail(ByteReader& r, InstrumentParams& p, bool preVelocityVersion)
     f.env.decaySeconds   = bitsToDouble(r.u64());
     f.env.sustainLevel   = bitsToDouble(r.u64());
     f.env.releaseSeconds = bitsToDouble(r.u64());
+    // velAmount feeds a MULTIPLIER on the stored curve's knots (below), not a param the engine
+    // clamps on its own — the UI never dials it outside [-1,1] (deckBipolarFromNorm), so a
+    // corrupt-but-finite blob value outside that range must clamp here rather than silently
+    // scaling the lifted curve past what fromPoints' own [-1,1] box-clamp would then truncate.
     const double velFold =
-        preVelocityVersion ? (std::isfinite(velAmount) ? velAmount : 0.0) : 1.0;
+        preVelocityVersion ? std::clamp(std::isfinite(velAmount) ? velAmount : 0.0, -1.0, 1.0)
+                            : 1.0;
     readCurveTail(r, f.velocityCurve, reasampler::instrument::engine::CurveDomain::Bipolar,
                   velFold);
 }

src/core/instrument/ui/deck_groups.cpp

@@ -238,6 +238,36 @@ bool overlayEnvInert(OverlayEnv env, bool pitchEnvEnabled, bool filterEnabled) {
     return false;  // unreachable for a valid enumerator; silences a warning.
 }
 
+bool deckKnobInert(DeckParam id, bool pitchEnvEnabled, bool filterEnabled) {
+    switch (id) {
+        case DeckParam::kPitchEnvAttack:
+        case DeckParam::kPitchEnvHold:
+        case DeckParam::kPitchEnvDecay:
+        case DeckParam::kPitchEnvDepth:
+            return !pitchEnvEnabled;
+        case DeckParam::kFilterMorph:
+        case DeckParam::kFilterCutoff:
+        case DeckParam::kFilterQ:
+        case DeckParam::kFilterDrive:
+        case DeckParam::kFilterModAmt:
+        case DeckParam::kFilterKeyTrack:
+        // The filter's velocity curve sits in the VELOCITY group but is a filter parameter:
+        // it goes inert with every other one, so no surface can reach a param the knobs can't.
+        case DeckParam::kFilterVelCurve:
+        case DeckParam::kFilterEnvAttack:
+        case DeckParam::kFilterEnvHold:
+        case DeckParam::kFilterEnvDecay:
+        case DeckParam::kFilterEnvSustain:
+        case DeckParam::kFilterEnvRelease:
+        case DeckParam::kFilterTrigAttack:
+        case DeckParam::kFilterTrigHold:
+        case DeckParam::kFilterTrigDecay:
+            return !filterEnabled;
+        default:
+            return false;
+    }
+}
+
 bool liveCommitFor(LiveDragKind kind, int paramId) {
     switch (kind) {
         case LiveDragKind::kDeckKnob:

src/core/instrument/ui/deck_groups.h

@@ -96,8 +96,10 @@ enum DeckGroupId {
 };
 
 // Which velocity curve a deck cell edits, or kNone when the control is an ordinary knob. THE
-// one place the three curve cells are named, so paint (draw a curve thumbnail, not a dial),
-// hit-test (open a popup, not start a drag) and the popup's own title all read from it.
+// one place a control id resolves to a curve target — paint (draw a curve thumbnail, not a
+// dial) and hit-test (open a popup, not start a drag) both read this predicate rather than
+// re-deriving which ids are curve cells. What each resolved target then shows (which stored
+// curve, which title) is a separate switch — see the shell's curveFor/curveTitle.
 enum class CurveTarget { kNone, kAmp, kPitch, kFilter };
 CurveTarget curveTargetFor(int controlId);
 
@@ -163,6 +165,13 @@ OverlayEnv nextOverlaySelection(OverlayEnv current, int radioId);
 // a param a knob couldn't (envelope_edit.h). Amp has no enable toggle and is never inert.
 bool overlayEnvInert(OverlayEnv env, bool pitchEnvEnabled, bool filterEnabled);
 
+// Whether a deck knob cell is drawn-but-dead: the pitch envelope's four knobs while it is
+// disabled, and the filter group's tone/modulation knobs (plus its VELOCITY cell, a filter
+// parameter that just sits in that group) while the filter is disabled. Every other id is
+// always live. Mirrors overlayEnvInert's group-toggle-gates-its-knobs shape for the deck's own
+// mouse-down/paint (the shell's deckKnobDisabled is a thin int-id wrapper over this).
+bool deckKnobInert(DeckParam id, bool pitchEnvEnabled, bool filterEnabled);
+
 // The deck's BIPOLAR knob law: 0.5 of the knob's travel is zero depth, the ends are -1 and
 // +1. Exact inverses, and exact at the centre detent (0.5 -> 0 -> 0.5), so a knob parked at
 // centre can never persist a hair of modulation. Out-of-range norm clamps to the endpoints.

src/core/instrument/ui/sample_bands.h

@@ -20,7 +20,7 @@ inline constexpr int kEditorMinWidth = 840;
 inline constexpr int kEditorMinHeight = 620;
 
 // Chrome band: the toolbar row (title + nav) stacked over the control row (piano strip,
-// preview, velocity knob, curve button, channel toggle). sample_chrome partitions it.
+// preview, velocity knob, channel toggle). sample_chrome partitions it.
 inline constexpr int kTitleHeight = 26;
 inline constexpr int kChromeRowHeight = 52;
 

src/shell/instrument/editor_controls.cpp

@@ -53,7 +53,9 @@ namespace {
 // The ceiling is READ from the overlay's schematic scale rather than restated: the AHDSR
 // schematic anchors a maxed knob at the canvas edge, which only holds while the two agree.
 constexpr double kEnvTimeMaxSeconds = instrument::ui::kGateStageMaxSeconds;
-constexpr double kPitchDepthMaxSemis = 24.0;          // pitch depth throw: +/-24 st, centered
+// Pitch depth throw: +/-kVelocityPitchRangeSemitones, centered. The one throw the pitch
+// envelope's peak and the velocity->pitch curve's full scale both speak (play_params.h).
+constexpr double kPitchDepthMaxSemis = kVelocityPitchRangeSemitones;
 constexpr double kKeyTrackMax = 2.0;                 // key-track slider ceiling (0..200%)
 
 // The raw stored curve exponent for a curve-dial control id, read DIRECTLY off the field —
@@ -510,21 +512,43 @@ void ReaSamplerEditor::unpackEnvelope(OverlayEnv which, const StageEnvelope& env
     }
 }
 
-const VelocityCurve& ReaSamplerEditor::editedCurve() const {
-    switch (curvePopup_) {
+const VelocityCurve& ReaSamplerEditor::curveFor(CurveTarget target) const {
+    switch (target) {
         case CurveTarget::kPitch:  return params_.play.pitchVelocityCurve;
         case CurveTarget::kFilter: return params_.play.filter.velocityCurve;
         case CurveTarget::kAmp:
         case CurveTarget::kNone:
-            // kNone only reaches here from a paint/hover racing the close; the amp curve is a
-            // valid, harmless read rather than a branch every caller would have to repeat.
+            // kNone reads as amp — a valid, harmless choice for a target-agnostic caller (a
+            // disabled deck cell still needs SOME curve to draw). editedCurve()'s mutable
+            // overload below refuses kNone rather than relying on this fallback to protect amp.
             return params_.velocityCurve;
     }
     return params_.velocityCurve;
 }
 
+VelocityCurve& ReaSamplerEditor::curveFor(CurveTarget target) {
+    return const_cast<VelocityCurve&>(std::as_const(*this).curveFor(target));
+}
+
+const VelocityCurve& ReaSamplerEditor::editedCurve() const { return curveFor(curvePopup_); }
+
 VelocityCurve& ReaSamplerEditor::editedCurve() {
-    return const_cast<VelocityCurve&>(std::as_const(*this).editedCurve());
+    // Refuses kNone rather than aliasing amp (see curvePopup_'s declaration for why); should be
+    // unreachable now that every writer of kNone also cancels the drag, but this is the second,
+    // independent line of defense.
+    if (curvePopup_ == CurveTarget::kNone) {
+        static VelocityCurve sink = VelocityCurve::flat();
+        return sink;
+    }
+    return curveFor(curvePopup_);
+}
+
+void ReaSamplerEditor::closeCurvePopup() {
+    curvePopup_ = CurveTarget::kNone;
+    if (drag_ == DragKind::kCurveNode) {
+        drag_ = DragKind::kNone;
+        curvePointIndex_ = -1;
+    }
 }
 
 void ReaSamplerEditor::applyParamControl(int id, double value, int segment) {

src/shell/instrument/editor_input_browse.cpp

@@ -131,9 +131,12 @@ void ReaSamplerEditor::onMouseWheel(int delta) {
 
 void ReaSamplerEditor::onSearchChar(unsigned int ch) {
     // The curve popup: Esc dismisses (checked first — the popup is modal over the face, and
-    // the Browse search cannot hold focus under it).
+    // the Browse search cannot hold focus under it). Esc reaches here unconditionally
+    // (editor_platform's WM_CHAR routing), including mid-drag on a curve node — closeCurvePopup
+    // cancels that drag too, or a subsequent WM_MOUSEMOVE would resolve editedCurve() with the
+    // popup already closed.
     if (curvePopup_ != CurveTarget::kNone && ch == 27) {
-        curvePopup_ = CurveTarget::kNone;
+        closeCurvePopup();
         invalidate();
         return;
     }

src/shell/instrument/editor_input_curve.cpp

@@ -23,7 +23,7 @@ bool ReaSamplerEditor::handlePopupMouseDown(int w, int h, int x, int y) {
     if (curvePopup_ == CurveTarget::kNone) return false;
     const CurvePopupLayout pl = computeCurvePopup(w, h);
     if (contains(pl.close, x, y)) {
-        curvePopup_ = CurveTarget::kNone;
+        closeCurvePopup();
         invalidate();
         return true;
     }
@@ -32,7 +32,7 @@ bool ReaSamplerEditor::handlePopupMouseDown(int w, int h, int x, int y) {
         return true;
     }
     if (popupOutsideSheet(pl, x, y) && drag_ == DragKind::kNone) {
-        curvePopup_ = CurveTarget::kNone;
+        closeCurvePopup();
         invalidate();
     }
     return true;

src/shell/instrument/editor_input_deck.cpp

@@ -17,33 +17,10 @@ using namespace reasampler::ui;
 using namespace reasampler::instrument::ui;
 
 bool ReaSamplerEditor::deckKnobDisabled(int id) const {
-    switch (static_cast<ParamControl>(id)) {
-        case ParamControl::kPitchEnvAttack:
-        case ParamControl::kPitchEnvHold:
-        case ParamControl::kPitchEnvDecay:
-        case ParamControl::kPitchEnvDepth:
-            return !params_.play.pitchEnv.enabled;
-        case ParamControl::kFilterMorph:
-        case ParamControl::kFilterCutoff:
-        case ParamControl::kFilterQ:
-        case ParamControl::kFilterDrive:
-        case ParamControl::kFilterModAmt:
-        case ParamControl::kFilterKeyTrack:
-        // The filter's velocity curve sits in the VELOCITY group but is a filter parameter:
-        // it goes inert with every other one, so no surface can reach a param the knobs can't.
-        case ParamControl::kFilterVelCurve:
-        case ParamControl::kFilterEnvAttack:
-        case ParamControl::kFilterEnvHold:
-        case ParamControl::kFilterEnvDecay:
-        case ParamControl::kFilterEnvSustain:
-        case ParamControl::kFilterEnvRelease:
-        case ParamControl::kFilterTrigAttack:
-        case ParamControl::kFilterTrigHold:
-        case ParamControl::kFilterTrigDecay:
-            return !params_.play.filter.enabled;
-        default:
-            return false;
-    }
+    // Thin int-id wrapper over the pure, CTest-covered predicate — see deckKnobInert
+    // (deck_groups.h) for which cells go inert and why.
+    return deckKnobInert(static_cast<DeckParam>(id), params_.play.pitchEnv.enabled,
+                         params_.play.filter.enabled);
 }
 
 bool ReaSamplerEditor::mouseDownDeck(const FaceLayout& fl, int x, int y) {

src/shell/instrument/editor_paint_chrome.cpp

@@ -1,7 +1,7 @@
 // editor_paint_chrome.cpp — the CHROME band's painter: the toolbar row (product title +
-// live readout, then the control run — preview, preview-velocity knob, curve button,
-// Mono|Stereo, Browse) over the strip row, which the piano strip has to itself. Windows-only;
-// all rects come from the pure sample_chrome interior and the pure keyboard_strip geometry.
+// live readout, then the control run — preview, preview-velocity knob, Mono|Stereo, Browse)
+// over the strip row, which the piano strip has to itself. Windows-only; all rects come from
+// the pure sample_chrome interior and the pure keyboard_strip geometry.
 
 #include "shell/instrument/reasampler_editor.h"
 
@@ -140,8 +140,9 @@ void ReaSamplerEditor::paintChrome(LICE_IBitmap* bmp, const FaceLayout& fl, bool
         drawButton(bmp, box, nullptr, st, /*warn=*/false);
         const PreviewGlyph g = previewGlyph(cr.preview);
         if (!g.empty()) {
-            const LICE_pixel ink =
-                toLice(roleColor(active ? Role::BgBase : Role::TextPrimary));
+            // Same surface as the button label, so the glyph tracks drawButton's own rule
+            // (buttonLabelRole) rather than a second copy of it that could desync from the kit.
+            const LICE_pixel ink = toLice(roleColor(buttonLabelRole(st)));
             LICE_FillTriangle(bmp, g.leftX, g.topY, g.leftX, g.bottomY, g.apexX, g.apexY,
                               ink, 1.0f, 0);
         }

src/shell/instrument/editor_paint_curve.cpp

@@ -17,19 +17,6 @@ using namespace reasampler::instrument::ui;  // popup geometry
 
 namespace {
 
-// The curve a VELOCITY cell shows. Mirrors editedCurve's routing for the popup's own target;
-// a cell draws whichever curve it opens, whether or not the popup is up.
-const VelocityCurve& curveFor(const InstrumentParams& p, CurveTarget target) {
-    switch (target) {
-        case CurveTarget::kPitch:  return p.play.pitchVelocityCurve;
-        case CurveTarget::kFilter: return p.play.filter.velocityCurve;
-        case CurveTarget::kAmp:
-        case CurveTarget::kNone:
-            return p.velocityCurve;
-    }
-    return p.velocityCurve;
-}
-
 const char* curveTitle(CurveTarget target) {
     switch (target) {
         case CurveTarget::kPitch:  return "VELOCITY -> PITCH";
@@ -56,7 +43,7 @@ void ReaSamplerEditor::paintCurveButton(LICE_IBitmap* bmp, const Rect& r, CurveT
                                 ? roleColor(Role::AccentPrimary)
                                 : roleColor(Role::LineHairline);
     LICE_DrawRect(bmp, r.x, r.y, r.width - 1, r.height - 1, toLice(border), 1.0f, 0);
-    const VelocityCurve& curve = curveFor(params_, target);
+    const VelocityCurve& curve = curveFor(target);
     const int inset = 3;
     const VelocityCurve::Box mini{r.x + inset, r.y + inset, r.width - 2 * inset,
                                   r.height - 2 * inset};

src/shell/instrument/editor_paint_deck.cpp

@@ -179,7 +179,7 @@ void ReaSamplerEditor::paintDeck(LICE_IBitmap* bmp, const FaceLayout& fl) {
                 paintCurveButton(bmp, c.knob, curveCell, disabled,
                                  !disabled && isHovered(HoverKind::kControl, c.id));
                 kitTextCentered(bmp, c.label, knobName(static_cast<ParamControl>(c.id)),
-                                Font::Micro, disabled ? Role::LineHairline : Role::TextDim);
+                                Font::Micro, Role::TextDim);
                 continue;
             }
             const bool dragging = (drag_ == DragKind::kDeckKnob && dragParamId_ == c.id);

src/shell/instrument/editor_session.cpp

@@ -72,7 +72,7 @@ void ReaSamplerEditor::refreshFromBank() {
     monoTrigger_ = processor_->monoTrigger();
     // A refresh that emptied the selection closes the curve popup — an open-but-invisible
     // modal would otherwise swallow clicks on the empty state.
-    if (selectedId_.empty()) curvePopup_ = CurveTarget::kNone;
+    if (selectedId_.empty()) closeCurvePopup();
     // Drop a filter that names a bank no longer present.
     if (!activeFilterBankId_.empty()) {
         bool found = false;

src/shell/instrument/reasampler_editor.h

@@ -150,7 +150,7 @@ private:
 
     // --- Band painters (one TU each, mirroring the input side) ---
     // Chrome: title band + Browse nav + the control row (root strip, preview, velocity knob,
-    // curve button, channel toggle).
+    // channel toggle).
     void paintChrome(LICE_IBitmap* bmp, const FaceLayout& fl, bool empty);
     // The hovered piano key's note-name chip. Drawn after every band — it overhangs the
     // chrome into whatever is below it.
@@ -459,11 +459,22 @@ private:
     // delta from this anchor, so a grab never jumps the value.
     double dragKnobStartValue_ = 0.0;
 
-    // Which velocity curve the popup is editing; kNone = closed. Never persisted.
+    // Which velocity curve the popup is editing; kNone = closed. Never persisted. Every writer
+    // of kNone must also cancel a live curve-node drag (closeCurvePopup does both) — an Esc
+    // mid-drag that closed the popup without cancelling the drag used to leave editedCurve()'s
+    // mutable overload aliasing the amp curve underneath an in-flight pitch/filter drag.
     CurveTarget curvePopup_ = CurveTarget::kNone;
-    // The parameter-set curve `curvePopup_` names. Both overloads exist because every edit
-    // path needs the mutable one and paint needs the const one; routing through this ONE
-    // switch is what keeps the three curves on a single popup/draw/hit-test code path.
+    void closeCurvePopup();
+
+    // THE one switch from a CurveTarget to the parameter-set curve it names — paint (button
+    // thumbnails, for every target) and edit (editedCurve, for curvePopup_ specifically) both
+    // route through it, so a fourth curve or a moved field is a one-place edit.
+    const VelocityCurve& curveFor(CurveTarget target) const;
+    VelocityCurve& curveFor(CurveTarget target);
+
+    // The curve curvePopup_ names — curveFor(curvePopup_), typed as its own pair because every
+    // edit path needs the mutable overload and paint needs the const one. The mutable overload
+    // refuses kNone (a closed popup has nothing open to edit) rather than aliasing amp.
     VelocityCurve& editedCurve();
     const VelocityCurve& editedCurve() const;
 

src/shell/panel/draw_kit.cpp

@@ -214,14 +214,15 @@ void drawButton(LICE_IBitmap* bmp, const KitButtonBox& button, const char* label
                    radius, toLice(borderCol), drawAlpha(borderCol), 0, true);
 
     if (label && *label) {
-        // Active fill is the accent — label goes in bg/base for contrast; else text/primary.
-        const Role textRole = (state == InteractionState::Active)
-                                  ? Role::BgBase
-                                  : Role::TextPrimary;
-        text(bmp, b, label, Font::Label, textRole, Align::Center);
+        text(bmp, b, label, Font::Label, buttonLabelRole(state), Align::Center);
     }
 }
 
+Role buttonLabelRole(InteractionState state) {
+    // Active fill is the accent — the mark goes in bg/base for contrast; else text/primary.
+    return state == InteractionState::Active ? Role::BgBase : Role::TextPrimary;
+}
+
 void drawSlider(LICE_IBitmap* bmp, const SliderGeometry& geom, InteractionState state) {
     if (!bmp || geom.track.empty()) return;
 

src/shell/panel/draw_kit.h

@@ -87,6 +87,11 @@ void fillSurface(LICE_IBitmap* bmp, const KitBox& box, Role role, InteractionSta
 void drawButton(LICE_IBitmap* bmp, const KitButtonBox& button, const char* label,
                 InteractionState state, bool warn);
 
+// THE ink role drawButton's own label draws in, for `state` (see draw_kit.cpp). A non-text
+// button mark (e.g. a drawn glyph, not text()) that needs to sit legibly on a drawButton
+// surface should call this rather than re-deriving the rule.
+Role buttonLabelRole(InteractionState state);
+
 // A horizontal slider: track groove, accent-filled portion up to the handle, and the
 // handle itself. `geom` is the pure SliderGeometry the caller computed.
 void drawSlider(LICE_IBitmap* bmp, const SliderGeometry& geom, InteractionState state);

tests/test_component_state_io.cpp

@@ -859,21 +859,36 @@ static void testPriorPayloadVersionsLiftToAHardSeam() {
     in.params.play.pitchVelocityCurve = reasampler::instrument::engine::VelocityCurve::fromPoints(
         {VelocityPoint{0.0, 0.5}, VelocityPoint{127.0, 1.0}},
         reasampler::instrument::engine::CurveDomain::Bipolar);
+    // The filter's pre-v12 depth fold (see testPreV12FilterVelocityDepthFoldsIntoTheCurve for
+    // the single-version proof); planted here too so EVERY version that carries a filter tail
+    // (v9..v11) is walked, not just v11 — the fold's branch condition is pv < kParamsVelocityVersion.
+    in.params.play.filter.enabled = true;
+    in.params.play.filter.modAmount = -0.6251953125;  // distinct, exactly representable anchor
+    const reasampler::instrument::engine::VelocityCurve filterShape =
+        reasampler::instrument::engine::VelocityCurve::fromPoints(
+            {VelocityPoint{0.0, 0.0}, VelocityPoint{64.0, 0.25}, VelocityPoint{127.0, 1.0}},
+            reasampler::instrument::engine::CurveDomain::Bipolar);
+    in.params.play.filter.velocityCurve = filterShape;
+    constexpr double kPlantedDepth = -0.75;
 
     struct Case {
         std::uint32_t pv;
         std::size_t cut;
         bool keepsCurveTail;
+        bool keepsFilterTail;
     };
     const Case cases[] = {
-        {11, kVelocityTailBytes, true},
-        {10, kVelocityTailBytes + kLoopTailBytes, true},
-        {9, kVelocityTailBytes + kLoopTailBytes + kCurveTailBytes, false},
-        {8, kVelocityTailBytes + kLoopTailBytes + kCurveTailBytes + kFilterTailBytes, false},
+        {11, kVelocityTailBytes, true, true},
+        {10, kVelocityTailBytes + kLoopTailBytes, true, true},
+        {9, kVelocityTailBytes + kLoopTailBytes + kCurveTailBytes, false, true},
+        {8, kVelocityTailBytes + kLoopTailBytes + kCurveTailBytes + kFilterTailBytes, false, false},
     };
     for (const Case& c : cases) {
-        const ComponentState out =
-            deserializeComponentState(payloadDowngradedTo(in, c.pv, c.cut), 48000.0);
+        std::vector<std::uint8_t> bytes = payloadDowngradedTo(in, c.pv, c.cut);
+        if (c.keepsFilterTail) {
+            plantPreV12FilterDepth(bytes, in.params.play.filter.modAmount, kPlantedDepth);
+        }
+        const ComponentState out = deserializeComponentState(bytes, 48000.0);
         // The span itself has been in the format since v2 and must survive untouched.
         CHECK(out.params.loopOverride && out.params.loopOverride->hasLoop);
         CHECK(out.params.loopOverride && out.params.loopOverride->start == 2000);
@@ -889,6 +904,20 @@ static void testPriorPayloadVersionsLiftToAHardSeam() {
         // And the cut landed on the tail boundary the ladder claims, not somewhere inside it.
         CHECK(out.params.play.adsr.attackCurve ==
               (c.keepsCurveTail ? 4.0 : reasampler::util::kCurveNeutral));
+        // The filter's own velocity curve: folded by the planted depth where the tail survives
+        // (v9..v11), the off/neutral default where it was cut away entirely (v8).
+        if (c.keepsFilterTail) {
+            CHECK(out.params.play.filter.enabled);
+            for (int v = 0; v <= 127; ++v) {
+                CHECK(std::fabs(out.params.play.filter.velocityCurve.eval(v) -
+                                kPlantedDepth * filterShape.eval(v)) < 1e-12);
+            }
+        } else {
+            CHECK(!out.params.play.filter.enabled);
+            for (int v = 0; v <= 127; ++v) {
+                CHECK(out.params.play.filter.velocityCurve.eval(v) == 0.0);
+            }
+        }
     }
 }
 

tests/test_curve_popup.cpp

@@ -8,6 +8,7 @@
 
 #include "../src/core/instrument/engine/velocity_curve.h"
 
+#include <algorithm>
 #include <cstdio>
 
 using namespace reasampler;
@@ -89,10 +90,14 @@ static void testOutsideSheetDismissTest() {
 // the popup's real geometry, because that is what makes one popup code path legitimate.
 static void testTheSameCurveBoxHostsBothDomains() {
     const CurvePopupLayout pl = computeCurvePopup(840, 620);
-    // The shell insets this rect before mapping; the inset is uniform, so any box inside the
-    // curveBox exercises the same relationship. Use the rect itself.
-    const VelocityCurve::Box box{pl.curveBox.x, pl.curveBox.y, pl.curveBox.width,
-                                 pl.curveBox.height};
+    // The editor never maps against the raw curveBox — shell/instrument/editor_internal.h's
+    // curveBoxFromRect insets it first (kVelCurveInset == 14, mirrored here since this pure
+    // target cannot link the shell). Applying it, not the raw rect, is what exercises the
+    // actual box shape paint/hit-test/drag agree on.
+    constexpr int kInset = 14;
+    const VelocityCurve::Box box{pl.curveBox.x + kInset, pl.curveBox.y + kInset,
+                                 std::max(0, pl.curveBox.width - 2 * kInset),
+                                 std::max(0, pl.curveBox.height - 2 * kInset)};
     CHECK(box.width > 1 && box.height > 1);
 
     const VelocityCurve amp = VelocityCurve::flat();
@@ -105,12 +110,15 @@ static void testTheSameCurveBoxHostsBothDomains() {
     CHECK(amp.pixelFromPoint(box, {0.0, 0.0}).y == bottom);
     CHECK(mod.pixelFromPoint(box, {0.0, 1.0}).y == top);
     CHECK(mod.pixelFromPoint(box, {0.0, -1.0}).y == bottom);
-    // ...so value 0 is the FLOOR for the amp curve and the MIDLINE for a modulation curve.
-    CHECK(mod.pixelFromPoint(box, {0.0, 0.0}).y == (top + bottom) / 2);
+    // ...so value 0 is the FLOOR for the amp curve and the MIDLINE for a modulation curve. The
+    // expected row replicates valueToY's own HALF-UP rounding on the inverted fraction (velocity_
+    // curve.cpp) rather than a plain integer bisection of top/bottom: the two agree only when
+    // box.height-1 is even, so a naive (top+bottom)/2 silently depends on this box's parity.
+    const int midY = top + static_cast<int>(0.5 * static_cast<double>(box.height - 1) + 0.5);
+    CHECK(mod.pixelFromPoint(box, {0.0, 0.0}).y == midY);
 
     // And a click at the vertical centre adds a point at 0 in the bipolar editor, at 0.5 in
     // the unipolar one — one hit-test path, two correct answers.
-    const int midY = (top + bottom) / 2;
     CHECK(mod.pointFromPixel(box, box.left, midY).value == 0.0);
     CHECK(amp.pointFromPixel(box, box.left, midY).value > 0.49);
     CHECK(amp.pointFromPixel(box, box.left, midY).value < 0.51);

tests/test_deck_groups.cpp

@@ -459,11 +459,29 @@ static void testOverlayIsInertExactlyWhenItsGroupToggleIsOff() {
     CHECK(!overlayEnvInert(OverlayEnv::kNone, false, false));
 }
 
+// A deck knob goes inert exactly with its group's own enable toggle — including the filter's
+// VELOCITY cell, which sits in the VELOCITY group visually but is a filter parameter and must
+// go inert with the rest of the filter (the reachable-through-the-deck route mouseDownDeck
+// checks before ever routing a curve-cell click to the popup).
+static void testDeckKnobIsInertExactlyWithItsGroupsEnableToggle() {
+    CHECK(deckKnobInert(DeckParam::kFilterVelCurve, /*pitchEnv=*/true, /*filter=*/false));
+    CHECK(!deckKnobInert(DeckParam::kFilterVelCurve, true, true));
+    CHECK(deckKnobInert(DeckParam::kFilterCutoff, true, false));
+    CHECK(!deckKnobInert(DeckParam::kFilterCutoff, true, true));
+    CHECK(deckKnobInert(DeckParam::kPitchEnvDepth, /*pitchEnv=*/false, true));
+    CHECK(!deckKnobInert(DeckParam::kPitchEnvDepth, true, true));
+    // The amp's own velocity cell and every ordinary control are never inert here — inertness
+    // is a filter/pitch-env-group-only concept.
+    CHECK(!deckKnobInert(DeckParam::kAmpVelCurve, false, false));
+    CHECK(!deckKnobInert(DeckParam::kAttack, false, false));
+}
+
 int main() {
     testOverlaySelectionIsExclusiveAcrossTheThreeEnvelopeDecks();
     testClickingTheActiveOverlayRadioClearsToNone();
     testANonRadioIdLeavesTheOverlaySelectionAlone();
     testOverlayIsInertExactlyWhenItsGroupToggleIsOff();
+    testDeckKnobIsInertExactlyWithItsGroupsEnableToggle();
     testEveryDeckControlIsClassifiedLiveOrReloading();
     testOnlyALiveControlsDragTakesTheLiveTier();
     testDeckReadsPitchThenFilterThenAmpLeftToRight();