fix: pin the waveform arbitration in a testable predicate, close round-4 review minors

Extracts resolveWaveformClaim (core/instrument/ui/spline_edit) so the shell's node/tab/marker click resolution is unit-tested directly, not just its input geometry; folds the staged-envelope node into it; fixes comment accuracy, a cost regression, and test fidelity issues.

src/core/instrument/engine/play_params.h

@@ -195,12 +195,10 @@ bool splineActive(const Play& p) {
            (p.filter.enabled && p.filterSpline.mode == EnvMode::Spline);
 }
 
-// The one enforcement of the rule above: forces `p` to Trigger the instant it goes
-// splineActive. Every path that can leave `p` in a state splineActive() would newly return true
-// for — resolving stored params toward the engine, or an editor control edit that can flip a
-// mode/enable toggle — routes through this, so none of them can reopen the Gate+spline hole
-// splineActive's own doc comment describes. Header-inline and allocation-free: play_params.h
-// sits on the per-voice-per-sample include path.
+// The one enforcement of splineActive's rule (see its doc above). Header-inline and
+// allocation-free: play_params.h sits on the per-voice-per-sample include path. Both callers —
+// resolvePlay (sample_map.cpp) and the editor's applyControl — route through here, so the two
+// cannot drift apart.
 template <class Play>
 void enforceGateUnavailableWhileDrawn(Play& p) {
     if (splineActive(p)) p.playMode = PlayMode::Trigger;

src/core/instrument/ui/CMakeLists.txt

@@ -24,10 +24,8 @@ reasampler_pure_library(waveform_view
     SOURCES waveform_view.cpp
     LINK PUBLIC editor_geometry peaks PRIVATE sample_bands)
 # sample_bands is linked directly here because the test exercises the lane metrics that
-# waveform_view does not re-export. velocity_curve is linked for the smallest-target-first
-# arbitration tests, which pin the geometric facts editor_input_waveform.cpp's node/tab/marker
-# resolution depends on (the shell itself has no test target).
-reasampler_test(waveform_view LINK waveform_view sample_bands velocity_curve)
+# waveform_view does not re-export.
+reasampler_test(waveform_view LINK waveform_view sample_bands)
 
 reasampler_pure_library(browser_scroll
     SOURCES browser_scroll.cpp
@@ -63,7 +61,12 @@ reasampler_test(deck_groups LINK deck_groups sample_bands)
 reasampler_pure_library(spline_edit
     SOURCES spline_edit.cpp
     LINK PUBLIC editor_geometry velocity_curve)
-reasampler_test(spline_edit LINK spline_edit)
+# waveform_view and sample_bands are linked for the test only: resolveWaveformClaim's
+# smallest-target-first tests build the real node/tab/marker geometry
+# editor_input_waveform.cpp's mouseDownWaveform composes (the shell that calls it has no test
+# target of its own), which needs waveform_view's marker/tab primitives and sample_bands'
+# kWaveformMinHeight floor.
+reasampler_test(spline_edit LINK spline_edit waveform_view sample_bands)
 
 reasampler_pure_library(curve_popup SOURCES curve_popup.cpp LINK PUBLIC editor_geometry)
 # velocity_curve is linked for the test only: the sheet's geometry is domain-agnostic, and

src/core/instrument/ui/spline_edit.cpp

@@ -26,4 +26,14 @@ VelocityCurve::Box splineOverlayBox(const OverlayArea& area) {
     return VelocityCurve::Box{area.rect.x, area.rect.y, area.rect.width, area.rect.height};
 }
 
+WaveformClaimant resolveWaveformClaim(const WaveformClaim& node, const WaveformClaim& tab,
+                                      const WaveformClaim& marker, SplineGesture gesture) {
+    if (gesture == SplineGesture::kControlLeft && node.hit) return WaveformClaimant::kNode;
+    if (node.hit && (!tab.hit || node.area <= tab.area) && (!marker.hit || node.area <= marker.area))
+        return WaveformClaimant::kNode;
+    if (tab.hit && (!marker.hit || tab.area <= marker.area)) return WaveformClaimant::kTab;
+    if (marker.hit) return WaveformClaimant::kMarker;
+    return WaveformClaimant::kNone;
+}
+
 }  // namespace reasampler::instrument::ui

src/core/instrument/ui/spline_edit.h

@@ -1,11 +1,13 @@
 // spline_edit.h — the point-editing grammar's CLICK resolution: add/grab/delete/toggle from a
-// single (x, y). Both spline consumers — the velocity-curve popup and the spline EG overlay —
-// route their mouse-down through it, so the two cannot drift into two click grammars. Two more
-// gesture rules complete the grammar but live in the shell (see the note near the bottom of this
-// file). Mirror of envelope_edit otherwise: decision logic only, no host types, no drawing.
+// single (x, y), plus resolveWaveformClaim, the waveform overlay's cross-affordance arbitration
+// (node vs. crossfade tab vs. marker). Both spline consumers — the velocity-curve popup and the
+// spline EG overlay — route their mouse-down through the click grammar, so the two cannot drift
+// apart. Decision logic only, no host types, no drawing; mirror of envelope_edit otherwise.
 
 #pragma once
 
+#include <cstdint>
+
 #include "core/instrument/engine/velocity_curve.h"
 #include "core/instrument/ui/editor_geometry.h"  // Rect / OverlayArea
 
@@ -51,4 +53,28 @@ VelocityCurve::Box splineOverlayBox(const OverlayArea& area);
 //   strictly in-box, since splineOverlayBox has no inset — editor_input_waveform.cpp's
 //   splineOverlayClick.
 
+// One arbitration candidate: whether the affordance was hit under the cursor, and its own
+// pick-target area (nominal, per its own module's constants — not the actual clipped pixel
+// count; see resolveWaveformClaim).
+struct WaveformClaim {
+    bool hit = false;
+    std::int64_t area = 0;
+};
+
+// Which affordance a waveform-overlay click claims.
+enum class WaveformClaimant { kNone, kNode, kTab, kMarker };
+
+// The overlay's cross-affordance arbitration: a contour node (or, mutually exclusively, a
+// staged envelope's drag node — both feed the same `node` slot), the loop crossfade tab, and a
+// marker's full-height column can all claim the same pixel. Hit gates a candidate out
+// entirely; among the ones that hit, the SMALLEST nominal area wins — the marker column is the
+// odd one out (its target is the whole overlay height), so it only wins where nothing narrower
+// also claims the click. Ties go to whichever is checked first: node, then tab, then marker —
+// no live geometry produces a tie except tab-vs-marker, which the tab correctly wins (see
+// editor_input_waveform.cpp's mouseDownWaveform for the live constants). A control-click has no
+// tab/marker meaning (they answer plain grabs only), so it resolves to the node whenever the
+// node is in the running, regardless of area.
+WaveformClaimant resolveWaveformClaim(const WaveformClaim& node, const WaveformClaim& tab,
+                                      const WaveformClaim& marker, SplineGesture gesture);
+
 }  // namespace reasampler::instrument::ui

src/shell/instrument/editor_input_waveform.cpp

@@ -39,88 +39,88 @@ bool ReaSamplerEditor::mouseDownWaveform(const FaceLayout& fl, int x, int y) {
                                       ? SplineGesture::kControlLeft
                                       : SplineGesture::kLeft;
 
-    // Envelope nodes first (they sit on top of the markers), then the wave markers. With no
-    // envelope overlay-active — or with its deck group's enable toggle off, which makes the
-    // same params' knobs inert — there are no grabbable nodes and the markers take every grab.
+    // The staged envelope's draggable node and the drawn contour's node are mutually exclusive
+    // (overlayEnvInert flips the staged one inert exactly when its envelope is in Spline mode),
+    // so at most one of the two hit-tests below is ever live for the same click — both feed the
+    // SAME arbitration slot below rather than either one getting its own check-order return.
     const double rate = liveSampleRate();
     const bool nodesLive =
         overlayEnv_ != OverlayEnv::kNone && !overlayEnvInert(overlayEnv_, gates);
+    NodeHit envNodeHit;
+    StageEnvelope env;
     if (rate > 0.0 && nodesLive) {
         const std::int64_t startFrame = params_.startPoint.value_or(0);
-        const StageEnvelope env = packEnvelope(overlayEnv_, params_.play, frames, startFrame);
+        env = packEnvelope(overlayEnv_, params_.play, frames, startFrame);
         const double totalSeconds = static_cast<double>(frames) / rate;
-        const NodeHit nh = nodeAtPoint(env, overlay, totalSeconds, x, y);
-        if (nh.hit) {
-            drag_ = DragKind::kEnvNode;
-            envNode_ = nh.node;
-            dragStartX_ = x;
-            dragStartY_ = y;
-            dragStartEnv_ = env;
-            dragSampleFrames_ = frames;
-            dragStartParams_ = params_;
-            return true;  // node moves once the cursor drags
-        }
+        envNodeHit = nodeAtPoint(env, overlay, totalSeconds, x, y);
     }
+
     const SetupMarkers m = pickedMarkers(frames);
     const std::int64_t markerFrames[3] = {m.start, m.loopStart, m.loopEnd};
 
-    // Three affordances can claim the same pixel: a contour node (a small fixed pick box), the
-    // crossfade tab (a small clipped top-strip tab), and a marker's full-height grab column
-    // (waveform_view.h's tab-vs-column split already keeps the tab apart from ITS OWN column;
-    // this is the cross-affordance case on top of that). Resolving by any fixed check order
-    // shadows whichever one loses the tie — this seam regressed twice from exactly that fix.
-    // Instead measure each claimant's own target area and let the SMALLEST hit win: the marker
-    // column is the odd one out (its target is the whole band height), so it only wins where
-    // nothing narrower also claims the pixel. Never add here (kAdd is only tried once nothing
-    // else has claimed the click, below).
-    struct Candidate {
-        bool hit = false;
-        std::int64_t area = 0;
-    };
-
-    Candidate node;
-    if (splineLive) {
+    // Three affordances can claim the same pixel: a node (the staged envelope's or the drawn
+    // contour's — a small fixed pick box either way), the crossfade tab (a small clipped
+    // top-strip tab), and a marker's full-height grab column (waveform_view.h's tab-vs-column
+    // split already keeps the tab apart from ITS OWN column; this is the cross-affordance case
+    // on top of that). resolveWaveformClaim (spline_edit.h) is the ONE arbitration: it measures
+    // each claimant's own NOMINAL target area and lets the smallest hit win, since a fixed check
+    // order shadows whichever one loses the tie — this seam regressed twice from exactly that
+    // fix. Never add here (kAdd is only tried once nothing else has claimed the click, below).
+    WaveformClaim node;
+    if (envNodeHit.hit) {
+        constexpr std::int64_t side = 2 * kNodeGrabRadius + 1;
+        node = {true, side * side};
+    } else if (splineLive) {
         const VelocityCurve::Box box = splineOverlayBox(overlay);
         // Also require strict in-box, matching splineOverlayClick's own narrowing (spline_edit.h's
         // grammar note) — otherwise this candidate could "win" the arbitration below for a click
         // splineOverlayClick would then refuse, silently swallowing it instead of falling through
         // to the tab/marker checks.
         if (contains(overlay.rect, x, y) && splineFor(overlayEnv_).pointAtPixel(box, x, y) >= 0) {
-            node.hit = true;
             constexpr std::int64_t side = 2 * kCurveNodeGrabRadius + 1;
-            node.area = side * side;
+            node = {true, side * side};
         }
     }
 
-    Candidate tab;
     const Rect tabRect =
         m.hasLoop ? markerHandleRect(overlay, frames, m.loopStart - m.crossfade) : Rect{};
-    if (m.hasLoop && contains(tabRect, x, y)) {
-        tab.hit = true;
-        tab.area = static_cast<std::int64_t>(tabRect.width) * tabRect.height;
-    }
+    const WaveformClaim tab = (m.hasLoop && contains(tabRect, x, y))
+                                  ? WaveformClaim{true, static_cast<std::int64_t>(tabRect.width) *
+                                                            tabRect.height}
+                                  : WaveformClaim{};
 
+    // Nominal, not actual: markerAtPoint clips the column at the overlay edges (a marker at
+    // frame 0 has 6 usable columns, not 11) and the node's fixed side clips too at a pick-box
+    // corner. Both overestimate in the direction that already produces the intended winner, so
+    // the arbitration runs on NOMINAL area, not the measured hit-testable pixel count.
     const int markerHit = markerAtPoint(overlay, frames, markerFrames, 3, x, y);
-    Candidate marker;
-    if (markerHit >= 0) {
-        marker.hit = true;
-        marker.area = static_cast<std::int64_t>(2 * kMarkerGrabWidth + 1) * overlay.rect.height;
-    }
+    const WaveformClaim marker =
+        (markerHit >= 0)
+            ? WaveformClaim{true, static_cast<std::int64_t>(2 * kMarkerGrabWidth + 1) *
+                                       overlay.rect.height}
+            : WaveformClaim{};
 
-    // Node checked before marker on an area tie so a degenerate (zero-height) overlay still
-    // prefers the node — unreachable in practice (sample_bands floors the band well above it),
-    // kept only so this arbitration has one well-defined answer for every input, not just the
-    // ones the current geometry constants happen to produce.
-    if (node.hit && (!tab.hit || node.area <= tab.area) && (!marker.hit || node.area <= marker.area)) {
-        return splineOverlayClick(overlay, x, y, gesture, /*addOnEmptySpace=*/false);
-    }
-    if (tab.hit && (!marker.hit || tab.area <= marker.area)) {
-        beginMarkerDrag(WaveMarker::kLoopXfade, m, frames, x);
-        return true;
-    }
-    if (marker.hit) {
-        beginMarkerDrag(static_cast<WaveMarker>(markerHit), m, frames, x);
-        return true;
+    switch (resolveWaveformClaim(node, tab, marker, gesture)) {
+        case WaveformClaimant::kNode:
+            if (envNodeHit.hit) {
+                drag_ = DragKind::kEnvNode;
+                envNode_ = envNodeHit.node;
+                dragStartX_ = x;
+                dragStartY_ = y;
+                dragStartEnv_ = env;
+                dragSampleFrames_ = frames;
+                dragStartParams_ = params_;
+                return true;  // node moves once the cursor drags
+            }
+            return splineOverlayClick(overlay, x, y, gesture, /*addOnEmptySpace=*/false);
+        case WaveformClaimant::kTab:
+            beginMarkerDrag(WaveMarker::kLoopXfade, m, frames, x);
+            return true;
+        case WaveformClaimant::kMarker:
+            beginMarkerDrag(static_cast<WaveMarker>(markerHit), m, frames, x);
+            return true;
+        case WaveformClaimant::kNone:
+            break;
     }
     // Nothing else wanted the click: now the drawn contour may take the empty space.
     if (splineLive) return splineOverlayClick(overlay, x, y, gesture, /*addOnEmptySpace=*/true);

src/shell/instrument/editor_session.cpp

@@ -186,8 +186,12 @@ ReaSamplerEditor::SetupMarkers ReaSamplerEditor::pickedMarkers(std::int64_t fram
     // Seed from the bank's intrinsic loop (fact about the file), then let the parameter set's
     // override win (the instrument's performance choice). Read the loop intrinsic from the
     // live bank blob (the same path selectSample uses); when that is not readable (extension
-    // absent / not yet parsed) the instance-owned ref carries the same intrinsics.
-    if (processor_) {
+    // absent / not yet parsed) the instance-owned ref carries the same intrinsics. Skipped
+    // entirely once an override is already set — it would just be overwritten below, and the
+    // bridge read + JSON parse it costs is real (mouseDownWaveform's arbitration calls this on
+    // every waveform click, not just marker grabs, to know whether a tab or marker candidate
+    // hits at all).
+    if (processor_ && !params_.loopOverride) {
         std::optional<SelectedSample> sel;
         auto banksJson =
             processor_->bridge().readReasamplerExtState(reasampler::kProjExtBanksKey);

tests/test_deck_groups.cpp

@@ -619,14 +619,14 @@ static bool sameLayout(const DeckLayout& a, const DeckLayout& b) {
 
 // A Spline excursion is fully reversible at the layout level: the mode forcing swaps the amp
 // and filter faces onto their wider cells and back, leaving no residue in the geometry. Driven
-// through splineActive and the editor's own forcing rule, so the deck cannot agree with a
-// forcing rule the shell does not use.
+// through the shared enforceGateUnavailableWhileDrawn helper, so the deck cannot agree with a
+// forcing rule the real callers do not use.
 static void testGateSplineGateRoundTripsToTheSameLayout() {
     PlayParams p;  // Gate, all three envelopes staged
     const DeckLayout before = layoutDeck(sampleDeckGroups(p.playMode), kPad, 0, kAvailAtMinWidth);
 
     p.ampSpline.mode = EnvMode::Spline;
-    if (splineActive(p)) p.playMode = PlayMode::Trigger;  // editor_controls' forcing, verbatim
+    enforceGateUnavailableWhileDrawn(p);  // the shared helper both real callers route through
     CHECK(p.playMode == PlayMode::Trigger);
     const DeckLayout drawn = layoutDeck(sampleDeckGroups(p.playMode), kPad, 0, kAvailAtMinWidth);
     // The excursion is real: the amp face's cells are strictly wider than Gate's.

tests/test_spline_edit.cpp

@@ -2,15 +2,22 @@
 // framework. Asserts the ONE point-editing grammar both spline consumers route through:
 // left-click grabs a node and adds in empty space, right-click deletes, control-click toggles
 // hard/smooth, and a click outside the mapping box resolves to nothing unless it lands on a
-// node's pick radius (so the popup's inset ring can grab but never add).
+// node's pick radius (so the popup's inset ring can grab but never add). Also
+// resolveWaveformClaim, the waveform overlay's node/tab/marker cross-affordance arbitration —
+// waveform_view is a test-only link so those tests can build the real geometry
+// editor_input_waveform.cpp's mouseDownWaveform composes.
 
 #include "../src/core/instrument/ui/spline_edit.h"
+#include "../src/core/instrument/ui/waveform_view.h"
+#include "../src/core/instrument/ui/sample_bands.h"  // kWaveformMinHeight
 
 #include <cstdio>
 
 using namespace reasampler::instrument::ui;
 using namespace reasampler::instrument::engine;
 
+static OverlayArea overlayOf(const Rect& r) { return OverlayArea{r}; }
+
 static int g_fail = 0;
 #define CHECK(cond) do { if(!(cond)) { \
     std::printf("FAIL line %d: %s\n", __LINE__, #cond); ++g_fail; } } while(0)
@@ -97,6 +104,159 @@ static void testOverlayBoxIsTheWholeArea() {
     CHECK(box.height == 200);
 }
 
+// --- Smallest-target-first: resolveWaveformClaim, the shell's own comparison chain -----
+//
+// editor_input_waveform.cpp's mouseDownWaveform resolves a click among a contour node (a fixed
+// pick box), the crossfade tab, and a marker's full-height column by calling
+// resolveWaveformClaim with each candidate's own target area; the smallest hit wins. These
+// tests build the real geometry over the pure primitives the shell composes, then feed it into
+// resolveWaveformClaim itself, so a reverted node-first/marker-first/tab-first ordering fails
+// them — pinning the mechanism, not just the input geometry it acts on. A realistic band height
+// (kWaveformMinHeight, the product's own floor) is used throughout so these numbers are the
+// worst case for the node, not a favourable one.
+static VelocityCurve::Box boxOf(const Rect& r) { return VelocityCurve::Box{r.x, r.y, r.width, r.height}; }
+
+constexpr std::int64_t kNodeSide = 2 * kCurveNodeGrabRadius + 1;
+constexpr std::int64_t kNodeArea = kNodeSide * kNodeSide;  // 169, fixed
+
+// Case (a): a fresh Spline default (rampDown) puts its endpoint 0 at (box.left, box.top) — the
+// exact pixel the start marker draws at frame 0. The node's fixed 169px pick box is far smaller
+// than a kWaveformMinHeight-tall marker column, so the endpoint stays reachable.
+static void testFreshRampDownEndpointBeatsTheStartMarkerAtFrameZero() {
+    const Rect a = Rect{20, 10, 1000, kWaveformMinHeight};
+    const OverlayArea overlay = overlayOf(a);
+    const std::int64_t frames = 100000;
+    const VelocityCurve contour = VelocityCurve::rampDown();
+    const VelocityCurve::Box box = boxOf(a);
+
+    CHECK(contour.pointAtPixel(box, a.x, a.y) == 0);  // endpoint 0 sits at (box.left, box.top)
+    const std::int64_t markers[1] = {0};
+    CHECK(markerAtPoint(overlay, frames, markers, 1, a.x, a.y) == 0);  // the coincidence
+
+    const std::int64_t markerArea =
+        static_cast<std::int64_t>(2 * kMarkerGrabWidth + 1) * a.height;  // 11 * band height
+    CHECK(kNodeArea < markerArea);  // the node wins: the endpoint stays a genuine grab target
+
+    const WaveformClaim node{true, kNodeArea};
+    const WaveformClaim marker{true, markerArea};
+    CHECK(resolveWaveformClaim(node, WaveformClaim{}, marker, SplineGesture::kLeft) ==
+          WaveformClaimant::kNode);
+}
+
+// Case (b): the crossfade tab at zero crossfade sits on loopStart's own pixel column; a node
+// dragged to value ~0.98 lands a couple of rows below the box top — inside the tab's own
+// top-strip band, where the review found the tab fully shadowed by a node-first pass.
+static void testCrossfadeTabBeatsAContourNodeNearItsTopStrip() {
+    const Rect a = Rect{20, 10, 1000, kWaveformMinHeight};
+    const OverlayArea overlay = overlayOf(a);
+    const std::int64_t frames = 100000;
+    const std::int64_t loopStart = 40000, crossfade = 0;  // zero crossfade -> tab sits on loopStart
+    const int mx = frameToX(overlay, frames, loopStart - crossfade);
+    const Rect tabRect = markerHandleRect(overlay, frames, loopStart - crossfade);
+    CHECK(!tabRect.empty());
+
+    const VelocityCurve::Box box = boxOf(a);
+    const int ny = a.y + 3;  // ~0.98 up a kWaveformMinHeight-tall box; inside the tab's top strip
+    VelocityCurve c = VelocityCurve::flat();
+    const VelocityPoint p = c.pointFromPixel(box, mx, ny);
+    c.addPoint(p.velocity, p.value);
+    CHECK(c.pointAtPixel(box, mx, ny) >= 0);
+    CHECK(contains(tabRect, mx, ny));  // the coincidence: both claim the same pixel
+
+    const std::int64_t tabArea = static_cast<std::int64_t>(tabRect.width) * tabRect.height;  // <= 110
+    CHECK(tabArea < kNodeArea);  // the tab wins: it stays the only affordance at zero crossfade
+
+    const WaveformClaim node{true, kNodeArea};
+    const WaveformClaim tab{true, tabArea};
+    CHECK(resolveWaveformClaim(node, tab, WaveformClaim{}, SplineGesture::kLeft) ==
+          WaveformClaimant::kTab);
+
+    // The residual the review names: the node keeps its OUTER columns, one pixel past the tab's
+    // clipped edge but still inside its own pick radius.
+    const int outerX = mx + kMarkerHandleHalfWidth + 1;
+    CHECK(!contains(tabRect, outerX, ny));
+    CHECK(c.pointAtPixel(box, outerX, ny) >= 0);
+}
+
+// Case (c): a contour node coincident with a loop marker. At kWaveformMinHeight (the product's
+// own floor) the column is already an order of magnitude larger than the node's fixed pick box,
+// so the node wins the shared pixel while the column stays reachable everywhere the node isn't.
+static void testContourNodeBeatsALoopMarkerAtTheirSharedPixelButNotElsewhere() {
+    const Rect a = Rect{20, 10, 1000, kWaveformMinHeight};
+    const OverlayArea overlay = overlayOf(a);
+    const std::int64_t frames = 100000;
+    const std::int64_t loopEnd = 70000;
+    const int mx = frameToX(overlay, frames, loopEnd);
+    const std::int64_t markers[1] = {loopEnd};
+
+    const VelocityCurve::Box box = boxOf(a);
+    const int ny = a.y + a.height / 2;  // mid-height, well clear of any tab
+    VelocityCurve c = VelocityCurve::flat();
+    const VelocityPoint p = c.pointFromPixel(box, mx, ny);
+    c.addPoint(p.velocity, p.value);
+    CHECK(c.pointAtPixel(box, mx, ny) >= 0);
+    CHECK(markerAtPoint(overlay, frames, markers, 1, mx, ny) == 0);  // the coincidence
+
+    const std::int64_t markerArea =
+        static_cast<std::int64_t>(2 * kMarkerGrabWidth + 1) * a.height;  // 11 * band height
+    CHECK(kNodeArea < markerArea);  // the node wins the shared pixel
+
+    const WaveformClaim node{true, kNodeArea};
+    const WaveformClaim marker{true, markerArea};
+    CHECK(resolveWaveformClaim(node, WaveformClaim{}, marker, SplineGesture::kLeft) ==
+          WaveformClaimant::kNode);
+
+    // A few rows clear of the node (outside its 13px pick box, still on the marker's column)
+    // the marker alone claims the click.
+    const int farY = ny + kCurveNodeGrabRadius + 4;
+    CHECK(c.pointAtPixel(box, mx, farY) < 0);
+    CHECK(markerAtPoint(overlay, frames, markers, 1, mx, farY) == 0);
+    CHECK(resolveWaveformClaim(WaveformClaim{}, WaveformClaim{}, marker, SplineGesture::kLeft) ==
+          WaveformClaimant::kMarker);
+}
+
+// The only live tie: the crossfade tab (<=110) can equal the node (169) only off-geometry, but
+// tab-vs-marker ties at overlay height 10 (kMarkerHandleHeight), where the tab's 11x10 strip
+// (110) equals a marker column's 11 * 10 (110) — the tab wins, matching check order.
+static void testTabWinsAGenuineTabVersusMarkerTie() {
+    CHECK(resolveWaveformClaim(WaveformClaim{}, WaveformClaim{true, 110}, WaveformClaim{true, 110},
+                               SplineGesture::kLeft) == WaveformClaimant::kTab);
+}
+
+// No claimant hit at all falls through to kNone — the caller's cue to let the drawn contour take
+// empty space (addOnEmptySpace) rather than starting any drag.
+static void testNoHitAnywhereFallsThroughToNone() {
+    CHECK(resolveWaveformClaim(WaveformClaim{}, WaveformClaim{}, WaveformClaim{}, SplineGesture::kLeft) ==
+          WaveformClaimant::kNone);
+}
+
+// A candidate that reports hit == false must never win merely because its (unused, default)
+// area of 0 looks "smallest" — hit gates a candidate out before its area is ever compared. Real
+// call sites never produce hit == false with area != 0, but the arbitration still owes one
+// well-defined answer to every input, not just the ones live geometry happens to produce.
+static void testAMissedCandidateNeverWinsOnADegenerateZeroArea() {
+    const WaveformClaim missedNode{false, 0};
+    const WaveformClaim tab{true, 50};
+    const WaveformClaim marker{true, 100};
+    CHECK(resolveWaveformClaim(missedNode, tab, marker, SplineGesture::kLeft) ==
+          WaveformClaimant::kTab);
+}
+
+// A control-click has no tab/marker meaning (only the node's hard/smooth toggle answers it), so
+// it resolves to the node whenever the node is in the running, even where a plain left-click at
+// the same pixel would hand the tab or marker the win on area alone.
+static void testControlClickAlwaysTakesTheNodeOverASmallerTabOrMarker() {
+    const WaveformClaim node{true, kNodeArea};
+    const WaveformClaim smallerTab{true, 50};  // would beat the node on a plain left-click
+    CHECK(resolveWaveformClaim(node, smallerTab, WaveformClaim{}, SplineGesture::kLeft) ==
+          WaveformClaimant::kTab);
+    CHECK(resolveWaveformClaim(node, smallerTab, WaveformClaim{}, SplineGesture::kControlLeft) ==
+          WaveformClaimant::kNode);
+    // No node in the running: control-click has nothing to fall back to, so the tab still wins.
+    CHECK(resolveWaveformClaim(WaveformClaim{}, smallerTab, WaveformClaim{},
+                               SplineGesture::kControlLeft) == WaveformClaimant::kTab);
+}
+
 int main() {
     testLeftClickOnANodeGrabsIt();
     testLeftClickInEmptySpaceAdds();
@@ -105,6 +265,15 @@ int main() {
     testOutsideTheBoxGrabsButNeverAdds();
     testDegenerateBoxResolvesToNothing();
     testOverlayBoxIsTheWholeArea();
+
+    testFreshRampDownEndpointBeatsTheStartMarkerAtFrameZero();
+    testCrossfadeTabBeatsAContourNodeNearItsTopStrip();
+    testContourNodeBeatsALoopMarkerAtTheirSharedPixelButNotElsewhere();
+    testTabWinsAGenuineTabVersusMarkerTie();
+    testNoHitAnywhereFallsThroughToNone();
+    testAMissedCandidateNeverWinsOnADegenerateZeroArea();
+    testControlClickAlwaysTakesTheNodeOverASmallerTabOrMarker();
+
     if (g_fail == 0) std::printf("spline_edit: all tests passed\n");
     return g_fail == 0 ? 0 : 1;
 }

tests/test_spline_egs.cpp

@@ -363,6 +363,33 @@ static void testFlatZeroFinalSegmentStillFreesTheVoiceEarly() {
     CHECK(!v.soundingNote());             // a genuine permanent terminus, not a mid-contour dip
 }
 
+// The timing, not just the fact: the case above is trivially "early" (a wholly-flat contour
+// frees on frame 0), which can't distinguish "frees early" from "frees at the right frame." This
+// fixture's final segment starts MID-sample, so the free must land there, not at frame 0 and not
+// at the sample's natural end. The breakpoint (phase 0.5495) is deliberately off every sampled
+// frame's exact phase (k/1000), so no sampled frame lands on the segment boundary itself and
+// which segment "owns" that frame is never ambiguous.
+static void testFlatZeroFinalSegmentFreesTheVoiceWhereItBeginsNotAtFrameZero() {
+    const double breakpointPhase = 0.5495;
+    const VelocityCurve contour = VelocityCurve::fromPoints(
+        {{xAt(0.0), 1.0}, {xAt(breakpointPhase), 0.0}, {xAt(1.0), 0.0}}, CurveDomain::Unipolar);
+    const std::size_t frames = 1000;
+    const SampleData s = splineAmpSample(frames, contour);
+
+    Voice v;
+    v.start(60, 100, s);
+    // Frames 0..549 (phase < breakpoint) sit on the declining first segment: still sounding.
+    for (std::size_t i = 0; i < 550; ++i) {
+        v.renderFrame();
+        CHECK(v.soundingNote());
+    }
+    // Frame 550 (phase 0.55) is the first sampled frame past the breakpoint, on the flat-zero
+    // final segment — this is where the early-free fires.
+    const double y550 = v.renderFrame();
+    CHECK(near(y550, 0.0, 1e-9));
+    CHECK(!v.soundingNote());
+}
+
 // --- 9. A fresh spline EG opens on the smooth y = 1 - x ----------------------
 
 static void testAFreshSplineEgDefaultsToTheSmoothDownwardSlope() {
@@ -532,6 +559,7 @@ int main() {
     testAContourReplaysProportionallyOnADifferentLengthSample();
     testTwoPointContourRisingFromZeroSoundsForItsFullSpan();
     testFlatZeroFinalSegmentStillFreesTheVoiceEarly();
+    testFlatZeroFinalSegmentFreesTheVoiceWhereItBeginsNotAtFrameZero();
     testAFreshSplineEgDefaultsToTheSmoothDownwardSlope();
     testGateIsUnavailableWhileASplineEgIsActiveAndReturnsAfterwards();
     testEnforceGateUnavailableWhileDrawnForcesTriggerOnBothRepresentations();

tests/test_waveform_view.cpp

@@ -13,7 +13,6 @@
 // stacked height, grabs reaching the lower lane); laneEnvelope (per-lane channel split).
 
 #include "../src/core/instrument/ui/waveform_view.h"
-#include "../src/core/instrument/engine/velocity_curve.h"  // kCurveNodeGrabRadius, VelocityCurve::pointAtPixel
 #include "../src/core/instrument/ui/sample_bands.h"  // kWaveformMinHeight, kLaneGap
 
 #include <cstddef>
@@ -22,7 +21,6 @@
 
 using namespace reasampler;
 using namespace reasampler::instrument::ui;
-using namespace reasampler::instrument::engine;
 using reasampler::audio::AudioSample;
 
 static int g_fail = 0;
@@ -386,102 +384,6 @@ static void testStartMarkerSharesTheHandleStripWhenItSitsAtTheFadeEdge() {
     CHECK(contains(markerHandleRect(overlayOf(a), 1000, fadeEdge), mx, topY));
 }
 
-// --- Smallest-target-first: the three-way coincidence with a spline contour node -------
-//
-// editor_input_waveform.cpp's mouseDownWaveform resolves a click among a contour node (a fixed
-// pick box), the crossfade tab, and a marker's full-height column by measuring each candidate's
-// own target area and letting the smallest win — this module can't exercise the shell's
-// arbitration itself (no shell test target wraps the editor), but it can pin the geometric facts
-// that arbitration depends on, over the pure primitives it composes. A realistic band height
-// (kWaveformMinHeight, the product's own floor) is used throughout so these numbers are the
-// worst case for the node, not a favourable one.
-static VelocityCurve::Box boxOf(const Rect& r) { return VelocityCurve::Box{r.x, r.y, r.width, r.height}; }
-
-// Case (a): a fresh Spline default (rampDown) puts its endpoint 0 at (box.left, box.top) — the
-// exact pixel the start marker draws at frame 0. The node's fixed 169px pick box is far smaller
-// than a kWaveformMinHeight-tall marker column, so the endpoint stays reachable.
-static void testFreshRampDownEndpointBeatsTheStartMarkerAtFrameZero() {
-    const Rect a = Rect{20, 10, 1000, kWaveformMinHeight};
-    const OverlayArea overlay = overlayOf(a);
-    const std::int64_t frames = 100000;
-    const VelocityCurve contour = VelocityCurve::rampDown();
-    const VelocityCurve::Box box = boxOf(a);
-
-    CHECK(contour.pointAtPixel(box, a.x, a.y) == 0);  // endpoint 0 sits at (box.left, box.top)
-    const std::int64_t markers[1] = {0};
-    CHECK(markerAtPoint(overlay, frames, markers, 1, a.x, a.y) == 0);  // the coincidence
-
-    constexpr std::int64_t nodeSide = 2 * kCurveNodeGrabRadius + 1;
-    constexpr std::int64_t nodeArea = nodeSide * nodeSide;  // 169, fixed
-    const std::int64_t markerArea =
-        static_cast<std::int64_t>(2 * kMarkerGrabWidth + 1) * a.height;  // 11 * band height
-    CHECK(nodeArea < markerArea);  // the node wins: the endpoint stays a genuine grab target
-}
-
-// Case (b): the crossfade tab at zero crossfade sits on loopStart's own pixel column; a node
-// dragged to value ~0.98 lands a couple of rows below the box top — inside the tab's own
-// top-strip band, where the review found the tab fully shadowed by a node-first pass.
-static void testCrossfadeTabBeatsAContourNodeNearItsTopStrip() {
-    const Rect a = Rect{20, 10, 1000, kWaveformMinHeight};
-    const OverlayArea overlay = overlayOf(a);
-    const std::int64_t frames = 100000;
-    const std::int64_t loopStart = 40000, crossfade = 0;  // zero crossfade -> tab sits on loopStart
-    const int mx = frameToX(overlay, frames, loopStart - crossfade);
-    const Rect tabRect = markerHandleRect(overlay, frames, loopStart - crossfade);
-    CHECK(!tabRect.empty());
-
-    const VelocityCurve::Box box = boxOf(a);
-    const int ny = a.y + 3;  // ~0.98 up a kWaveformMinHeight-tall box; inside the tab's top strip
-    VelocityCurve c = VelocityCurve::flat();
-    const VelocityPoint p = c.pointFromPixel(box, mx, ny);
-    c.addPoint(p.velocity, p.value);
-    CHECK(c.pointAtPixel(box, mx, ny) >= 0);
-    CHECK(contains(tabRect, mx, ny));  // the coincidence: both claim the same pixel
-
-    constexpr std::int64_t nodeSide = 2 * kCurveNodeGrabRadius + 1;
-    constexpr std::int64_t nodeArea = nodeSide * nodeSide;                  // 169, fixed
-    const std::int64_t tabArea = static_cast<std::int64_t>(tabRect.width) * tabRect.height;  // <= 110
-    CHECK(tabArea < nodeArea);  // the tab wins: it stays the only affordance at zero crossfade
-
-    // The residual the review names: the node keeps its OUTER columns, one pixel past the tab's
-    // clipped edge but still inside its own pick radius.
-    const int outerX = mx + kMarkerHandleHalfWidth + 1;
-    CHECK(!contains(tabRect, outerX, ny));
-    CHECK(c.pointAtPixel(box, outerX, ny) >= 0);
-}
-
-// Case (c): a contour node coincident with a loop marker. At kWaveformMinHeight (the product's
-// own floor) the column is already an order of magnitude larger than the node's fixed pick box,
-// so the node wins the shared pixel while the column stays reachable everywhere the node isn't.
-static void testContourNodeBeatsALoopMarkerAtTheirSharedPixelButNotElsewhere() {
-    const Rect a = Rect{20, 10, 1000, kWaveformMinHeight};
-    const OverlayArea overlay = overlayOf(a);
-    const std::int64_t frames = 100000;
-    const std::int64_t loopEnd = 70000;
-    const int mx = frameToX(overlay, frames, loopEnd);
-    const std::int64_t markers[1] = {loopEnd};
-
-    const VelocityCurve::Box box = boxOf(a);
-    const int ny = a.y + a.height / 2;  // mid-height, well clear of any tab
-    VelocityCurve c = VelocityCurve::flat();
-    const VelocityPoint p = c.pointFromPixel(box, mx, ny);
-    c.addPoint(p.velocity, p.value);
-    CHECK(c.pointAtPixel(box, mx, ny) >= 0);
-    CHECK(markerAtPoint(overlay, frames, markers, 1, mx, ny) == 0);  // the coincidence
-
-    constexpr std::int64_t nodeSide = 2 * kCurveNodeGrabRadius + 1;
-    constexpr std::int64_t nodeArea = nodeSide * nodeSide;  // 169, fixed
-    const std::int64_t markerArea =
-        static_cast<std::int64_t>(2 * kMarkerGrabWidth + 1) * a.height;  // 11 * band height
-    CHECK(nodeArea < markerArea);  // the node wins the shared pixel
-
-    // A few rows clear of the node (outside its 13px pick box, still on the marker's column)
-    // the marker alone claims the click.
-    const int farY = ny + kCurveNodeGrabRadius + 4;
-    CHECK(c.pointAtPixel(box, mx, farY) < 0);
-    CHECK(markerAtPoint(overlay, frames, markers, 1, mx, farY) == 0);
-}
-
 // --- Per-lane envelope content -------------------------------------------------
 
 static void testAsymmetricStereoLanesCarryDifferentContent() {
@@ -557,9 +459,6 @@ int main() {
     testMarkerHandleClipsIntoTheArea();
     testMarkerHandleOnDegenerateAreas();
     testStartMarkerSharesTheHandleStripWhenItSitsAtTheFadeEdge();
-    testFreshRampDownEndpointBeatsTheStartMarkerAtFrameZero();
-    testCrossfadeTabBeatsAContourNodeNearItsTopStrip();
-    testContourNodeBeatsALoopMarkerAtTheirSharedPixelButNotElsewhere();
 
     testAsymmetricStereoLanesCarryDifferentContent();
     testLaneEnvelopeRejectsOutOfRangeLane();