fix(manifold): full-width input vector, dropped switches, MIDI churn, re-subscribe churn

Phase 2 (S10, L19, L18, L24).

- S10: EngineApi.inputVector() returned a freshly allocated [lastRawX, lastRawY]
  on every spine tick, so VCV bridged mode silently truncated gamepad/MIDI input
  to 2-D while the spine already held the full N-dim raw vector. It now returns
  spine.lastRawInputs (ArrayLike<number>, documented as a live reused buffer —
  copy, don't retain; VcvBackend already copies), and VcvBackend tracks and
  dead-zones the full length. Audit correction: "32-input head" is not a
  constant — 32 is DEFAULT_MODE_ML.inputSize, the over-provisioned default
  before any mode is chosen; real per-mode widths come from the schemas.
- L19: BackendManager.setActive silently dropped a switch requested while
  another was in flight. Now stores the latest requested id and re-runs it in
  the finally block (latest-caller-wins).
- L18: MIDI CC messages triggered a React state update plus a snapshot
  allocation each. notifyBindings now fires only when the binding LIST changes.
- L24: two ConsoleApp global-listener effects had no dependency array and so
  re-subscribed on every render, including every pointer frame. Both now read
  through a single ref assigned in the render body, matching the existing
  onMoveRef pattern. Audit correction: its suggested `[inputs]` dep would not
  have worked — useInputLayer returns a fresh object literal each call, so that
  dep changes every render too.

Regression tests: input-vector-truncation.test.ts, backend-manager-switch.test.ts
(a fake backend whose start() is held open, to make the in-flight switch real),
midi-notify-churn.test.ts (fail-before confirmed: 51 notifications vs 1).
L24 has no test — this repo has no DOM render harness to count re-subscriptions
against a mounted component; verified by reading and reference-stability tracing.

ALSO: manifold/package.json's test script named its test files explicitly
("bun test src tests/pipeline-golden.test.ts"), so the three new files were not
run by `bun run test` or CI — regression tests that never execute. Now a glob.
Deliberately `tests/*.test.ts` rather than `tests`: bun's discovery matches
*.spec.ts too, which would drag the Playwright e2e specs into the unit run
(verified — it fails). Unit tests go 9 -> 17.

Gates: run-all-tests.sh ALL GREEN.

manifold/package.json

@@ -9,7 +9,7 @@
     "build": "tsc --noEmit && vite build",
     "preview": "vite preview --port 4273",
     "typecheck": "tsc --noEmit",
-    "test": "bun test src tests/pipeline-golden.test.ts",
+    "test": "bun test src tests/*.test.ts",
     "test:e2e": "playwright test",
     "test:e2e:headed": "playwright test --headed"
   },

manifold/src/backends/manager.ts

@@ -31,11 +31,13 @@ export interface ManagerEngine {
   routedOutput(): Float32Array | null;
   audio: { setMuted(muted: boolean): void };
   /**
-   * Current control input vector (2-D for the fixed 2→N MLP). Optional — when
+   * Current FULL-width control input vector (one entry per active input axis
-   * present the VCV backend streams it to the module so the browser drives the
+   * — NOT fixed at 2-D). Optional — when present the VCV backend streams it
-   * module's inputs in bridged mode.
+   * to the module so the browser drives the module's inputs in bridged mode.
+   * May be a live reused buffer (ArrayLike) — the manager copies it straight
+   * through to `VcvBackend.setInputVector`, which itself copies.
    */
-  inputVector?(): ReadonlyArray<number>;
+  inputVector?(): ArrayLike<number>;
 }
 
 export class BackendManager {
@@ -46,6 +48,11 @@ export class BackendManager {
   private ctx: BackendContext | null = null;
   private unsub: (() => void) | null = null;
   private switching = false;
+  /** Latest id requested while a switch was already in flight (simplification
+   *  audit L19) — re-run once the in-flight switch settles, so a rapid double
+   *  click no longer silently drops the second request. Cleared before the
+   *  re-run so it can only ever chain one hop at a time (no unbounded loop). */
+  private pendingId: BackendId | null = null;
 
   private statusListeners = new Set<(id: BackendId, s: BackendStatus) => void>();
   private offBackendStatus: (() => void) | null = null;
@@ -126,19 +133,24 @@ export class BackendManager {
   /**
    * Switch the active backend. Tears down the old, starts the new, and applies
    * the synth audio gate. Idempotent for the same id.
+   *
+   * If a switch is already in flight, the request is NOT dropped: it is
+   * remembered as `pendingId` (the latest caller wins) and re-run once the
+   * in-flight switch's `finally` settles — see below.
    */
   async setActive(id: BackendId): Promise<void> {
-    if (this.activeId === id || this.switching) return;
+    if (this.activeId === id) return;
+    if (this.switching) {
+      this.pendingId = id;
+      return;
+    }
     this.switching = true;
     try {
       // Gate audio: only the synth mode drives sound.
       this.engine.audio.setMuted(id !== 'synth');
 
       const next = this.backends.get(id);
-      if (!next) {
+      if (!next) return;
-        this.switching = false;
-        return;
-      }
       if (this.active) {
         this.offBackendStatus?.();
         this.offBackendStatus = null;
@@ -154,6 +166,16 @@ export class BackendManager {
       this.emitStatus(id, next.status());
     } finally {
       this.switching = false;
+      // A newer request arrived mid-switch — chase it. Clearing `pendingId`
+      // BEFORE the recursive call (rather than in it) bounds this to one hop
+      // per settled switch: the only way to chain further is another NEW
+      // request arriving during that hop, which is the intended behaviour,
+      // not an infinite loop.
+      const pending = this.pendingId;
+      this.pendingId = null;
+      if (pending !== null && pending !== this.activeId) {
+        void this.setActive(pending);
+      }
     }
   }
 

manifold/src/backends/vcv-backend.ts

@@ -9,7 +9,9 @@
  * manifold/osc-bridge, default ws://localhost:8765, default module UDP 7001):
  *
  *   browser → module
- *     /nisps/input    <f…f>     the current 2-D input vector (drives the module)
+ *     /nisps/input    <f…f>     the current input vector, full net input
+ *                               arity (drives the module — NOT truncated to
+ *                               2-D; simplification audit S10)
  *     /nisps/output   <f…f>     per-output values (CV) — sent as params batch so
  *                               the bridge maps each to /nisps/<name>; the module
  *                               also derives its own outputs, but the browser
@@ -62,13 +64,18 @@ export class VcvBackend implements OutputBackend {
   private specs: VcvSpec[] = [];
   private sendRaw = false;
 
-  /** Latest input vector the browser is driving the module with (2-D). */
+  /** Latest input vector the browser is driving the module with (N-D — the
+   *  net's full input arity, not fixed at 2; simplification audit S10). */
   private inputVec: number[] = [0.5, 0.5];
 
   private lastSent: Float32Array = new Float32Array(0); // last normalised output
   private batch: Array<[string, number]> = []; // reused outer; entries reused
   private lastSendMs = 0;
-  private lastInputSent: [number, number] = [-1, -1];
+  /** Dead-zone sentinel per input axis, sized to `inputVec` (out-of-range -1
+   *  forces the first send). Tracks the FULL vector, not just the first two
+   *  axes, so a change in axis 2+ (gamepad/MIDI beyond the XY pair) still
+   *  triggers a resend instead of being silently swallowed. */
+  private lastInputSent: number[] = [];
 
   private gotModuleReply = false;
 
@@ -146,7 +153,7 @@ export class VcvBackend implements OutputBackend {
    * Set the input vector the browser drives the module with (bridged mode). The
    * next `send()` streams it to /nisps/input. Copied — caller may mutate.
    */
-  setInputVector(vec: ReadonlyArray<number>): void {
+  setInputVector(vec: ArrayLike<number>): void {
     if (this.inputVec.length !== vec.length) this.inputVec = new Array(vec.length);
     for (let i = 0; i < vec.length; i++) this.inputVec[i] = vec[i];
   }
@@ -171,11 +178,20 @@ export class VcvBackend implements OutputBackend {
     this.lastSendMs = now;
 
     // 1) Stream the current input vector so the browser drives the module.
-    const ix = this.inputVec[0] ?? 0.5;
+    //    Dead-zone over the FULL vector — any axis moving (not just the first
-    const iy = this.inputVec[1] ?? 0.5;
+    //    two) triggers a resend (simplification audit S10).
-    if (Math.abs(ix - this.lastInputSent[0]) >= DEAD_ZONE || Math.abs(iy - this.lastInputSent[1]) >= DEAD_ZONE) {
+    if (this.lastInputSent.length !== this.inputVec.length) {
-      this.lastInputSent[0] = ix;
+      this.lastInputSent = new Array(this.inputVec.length).fill(-1);
-      this.lastInputSent[1] = iy;
+    }
+    let inputChanged = false;
+    for (let i = 0; i < this.inputVec.length; i++) {
+      if (Math.abs(this.inputVec[i] - this.lastInputSent[i]) >= DEAD_ZONE) {
+        inputChanged = true;
+        break;
+      }
+    }
+    if (inputChanged) {
+      for (let i = 0; i < this.inputVec.length; i++) this.lastInputSent[i] = this.inputVec[i];
       // → bridge `input` verb → ONE multi-float message to /nisps/input.
       this.client.sendInput(this.inputVec);
     }

manifold/src/console/ConsoleApp.tsx

@@ -593,6 +593,40 @@ export function ConsoleApp() {
   const setParam = (i: number, patch: Partial<MFParam>) =>
     setParams((ps) => ps.map((p, j) => (j === i ? { ...p, ...patch } : p)));
 
+  // Ref-mirror of everything the two global-listener effects below close over
+  // that is NOT already React-stable (verdict/navigation handlers are plain
+  // consts re-created every render; `pos`/`inputs.inputMode` are per-render
+  // values). Assigned directly in the render body — same technique as
+  // `onMoveRef` in Manifold.tsx — so both effects can install their
+  // subscriptions ONCE ([] deps) instead of tearing down + re-subscribing on
+  // EVERY render (previously: no dep array at all, so both effects re-ran on
+  // every render — including every pointer frame `onReducedInput`/`setPos`
+  // drive; simplification audit L24). `setActive`/`setDepth`/`setSplit`/
+  // `setPos` are `useState` setters, which React guarantees are stable, so
+  // they're read directly and don't need mirroring here.
+  const liveRef = useRef({
+    perturb,
+    commit,
+    undo,
+    reroll,
+    onScratchNudge,
+    onPlace,
+    onPickLocation,
+    pos,
+    inputMode: inputs.inputMode,
+  });
+  liveRef.current = {
+    perturb,
+    commit,
+    undo,
+    reroll,
+    onScratchNudge,
+    onPlace,
+    onPickLocation,
+    pos,
+    inputMode: inputs.inputMode,
+  };
+
   // keyboard accelerators
   useEffect(() => {
     const onKey = (e: KeyboardEvent) => {
@@ -607,10 +641,10 @@ export function ConsoleApp() {
       };
       if (e.key === '1') {
         e.preventDefault();
-        perturb();
+        liveRef.current.perturb();
       } else if (e.key === '2') {
         e.preventDefault();
-        commit();
+        liveRef.current.commit();
       } else if (map[e.key]) {
         setActive((a) => (a === map[e.key] ? null : map[e.key]));
         setDepth('condensed');
@@ -626,15 +660,15 @@ export function ConsoleApp() {
         setSplit(0.5);
       } else if (e.key === ' ' || e.key === 'ArrowUp') {
         e.preventDefault();
-        commit();
+        liveRef.current.commit();
       } else if (e.key === 'ArrowDown') {
         e.preventDefault();
-        perturb();
+        liveRef.current.perturb();
-      } else if (e.key.toLowerCase() === 'z') undo();
+      } else if (e.key.toLowerCase() === 'z') liveRef.current.undo();
     };
     window.addEventListener('keydown', onKey);
     return () => window.removeEventListener('keydown', onKey);
-  });
+  }, []);
 
   // ---- Game-controller verdict bindings (inputs-spec) ---------------------
   // The gamepad's sticks already feed the input layer (→ engine); its BUTTONS
@@ -644,50 +678,57 @@ export function ConsoleApp() {
   //   (hold A, move the stick to a spot on the manifold, release to drop it).
   // MIDI note actions are surfaced too but left unbound (MIDI mode learns CCs
   // as INPUT axes; verdicts there stay on the on-screen / keyboard controls).
-  // The effect has no dep array (matching the keydown handler above) so each
+  // Deps are the two subscribe methods, not `inputs` itself: `inputs` is a
-  // binding closes over the latest verdict functions + live `pos`.
+  // fresh object literal every render (useInputLayer doesn't memoize its
+  // return value), so depending on the whole object would reintroduce the
+  // exact per-render resubscribe churn this fix removes. `onAction`/
+  // `onReducedInput` ARE stable (useCallback over a ref-held layer created
+  // once), so this genuinely installs once; everything that DOES vary
+  // per-render is read fresh through `liveRef` above.
   useEffect(() => {
     const unBtn = inputs.onAction((a) => {
       if (a.source !== 'gamepad') return;
       const phase = a.phase ?? 'press';
+      const live = liveRef.current;
       if (phase === 'press') {
         switch (a.id) {
           case 'button:4': // LB → thumbs-down
-            perturb();
+            live.perturb();
             break;
           case 'button:5': // RB → thumbs-up
-            commit();
+            live.commit();
             break;
           case 'button:2': // X → randomise / re-roll
-            reroll();
+            live.reroll();
             break;
           case 'button:3': // Y → nudge (scratchpad)
-            onScratchNudge();
+            live.onScratchNudge();
             break;
           case 'button:1': // B → undo
-            undo();
+            live.undo();
             break;
           case 'button:0': // A (down) → begin repositioning an example
-            onPlace();
+            live.onPlace();
             break;
         }
       } else if (phase === 'release' && a.id === 'button:0') {
         // A (up) → drop the example at the current (stick-driven) location.
-        onPickLocation(pos[0], pos[1]);
+        live.onPickLocation(live.pos[0], live.pos[1]);
       }
     });
     // Mirror the composed gamepad/MIDI position onto the on-screen manifold so
     // markers + readouts track the controller (the XY pad pushes its own pos).
     // The callback fires every rAF frame — only re-render when it actually moves.
     const unPos = inputs.onReducedInput((x, y) => {
-      if (inputs.inputMode === 'internal') return;
+      if (liveRef.current.inputMode === 'internal') return;
       setPos((prev) => (Math.abs(prev[0] - x) < 1e-3 && Math.abs(prev[1] - y) < 1e-3 ? prev : [x, y]));
     });
     return () => {
       unBtn();
       unPos();
     };
-  });
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [inputs.onAction, inputs.onReducedInput]);
 
   const onToggleAudio = () => {
     if (!engine) return;

manifold/src/engine/engine-api.ts

@@ -241,11 +241,14 @@ export class EngineApi {
   }
 
   /**
-   * Current control input vector (2-D for the fixed 2→N MLP). Used by the VCV
+   * Current FULL-width control input vector (one entry per active input axis,
-   * backend (via BackendManager) to drive the module's inputs over the bridge.
+   * up to the net's input arity — NOT fixed at 2). Live reused buffer — copy,
+   * don't retain. Used by the VCV backend (via BackendManager) to drive the
+   * module's inputs over the bridge without truncating gamepad/MIDI axes
+   * beyond the first two (simplification audit S10).
    */
-  inputVector(): ReadonlyArray<number> {
+  inputVector(): ArrayLike<number> {
-    return [this.spine.lastRawX, this.spine.lastRawY];
+    return this.spine.lastRawInputs;
   }
 
   /**

manifold/src/engine/spine.ts

@@ -88,8 +88,14 @@ export class Spine implements EngineSink {
   // Last raw input, so `EngineApi.process()` can re-tick after a weight change.
   lastRawX = 0.5;
   lastRawY = 0.5;
-  // Full last raw input vector (N-D) for re-ticking without losing extra axes.
+  /**
-  private lastRawInputs: Float32Array = new Float32Array(2);
+   * Full last raw input vector (N-D), so `process()`/`reprocess()` can re-tick
+   * without losing extra axes. Public + reused (live buffer — copy, don't
+   * retain): this is what `EngineApi.inputVector()` hands to the VCV backend
+   * so bridged mode drives the module's FULL input arity instead of the
+   * fixed 2-D pair `lastRawX`/`lastRawY` cover (simplification audit S10).
+   */
+  lastRawInputs: Float32Array = new Float32Array(2);
   private mlBuf: F32 = new Float32Array(126);
   private routedBuf: F32 | null = null;
 

manifold/src/inputs/midi-input-source.ts

@@ -216,6 +216,14 @@ export class WebMidiInputSource extends BaseSource {
    * Route an incoming CC: update a matching binding's value, or — if batch
    * learn is armed — capture it as a NEW axis (deduped). Learn stays armed so
    * the user can sweep their whole control surface in one pass.
+   *
+   * `notifyBindings()` fires ONLY when the binding LIST changes (a new axis
+   * captured here, or `clearBinding`/`clearAllBindings`) — NOT on every value
+   * update, which used to push a React state update + a fresh array snapshot
+   * per incoming CC message (simplification audit L18). `sample()` already
+   * pulls live values every input-layer tick; a consumer that wants a live
+   * per-binding readout (e.g. a meter) should read `getBindings()` on demand
+   * (poll/rAF) rather than rely on a notify-per-value-change contract.
    */
   private handleCc(number: number, channel: number, value: number): void {
     const existing = this.bindings.find(
@@ -223,7 +231,6 @@ export class WebMidiInputSource extends BaseSource {
     );
     if (existing) {
       existing.value = value;
-      this.notifyBindings();
       return;
     }
     if (this.learnArmed) {
@@ -232,14 +239,17 @@ export class WebMidiInputSource extends BaseSource {
     }
   }
 
-  /** Update a learned note axis's gate value (note bindings are not auto-learned). */
+  /**
+   * Update a learned note axis's gate value (note bindings are not
+   * auto-learned, so this never changes the binding LIST — see the
+   * notify-on-list-change contract on {@link handleCc}).
+   */
   private updateNote(number: number, channel: number, value: number): void {
     const existing = this.bindings.find(
       (b) => b.kind === 'note' && b.number === number && b.channel === channel,
     );
     if (existing) {
       existing.value = value;
-      this.notifyBindings();
     }
   }
 

manifold/tests/backend-manager-switch.test.ts

@@ -0,0 +1,130 @@
+/**
+ * BackendManager.setActive regression (simplification audit L19): a switch
+ * requested while another is already in flight must NOT be silently dropped.
+ * Run with `bun test tests/backend-manager-switch.test.ts` (see NOTE at the
+ * bottom of this file re: `bun run test` wiring).
+ */
+import { expect, test } from 'bun:test';
+import { BackendManager, type ManagerEngine } from '../src/backends/manager';
+import type { BackendContext, BackendStatus, OutputBackend } from '../src/backends/backend';
+import type { BackendId } from '../src/dock/output-state';
+
+function makeCtx(): BackendContext {
+  return { modeId: 'test', outputCount: 0, mappings: [], names: [] };
+}
+
+function makeEngine(): ManagerEngine {
+  return {
+    subscribe: () => () => {},
+    routedOutput: () => null,
+    audio: { setMuted: () => {} },
+  };
+}
+
+/** A fake backend whose `start()` can be held open until the test releases it,
+ *  so we can deterministically land a second `setActive` call WHILE the first
+ *  is still in flight. */
+class FakeBackend implements OutputBackend {
+  readonly id: BackendId;
+  startCalls = 0;
+  teardownCalls = 0;
+  private release: (() => void) | null = null;
+  private hold: boolean;
+
+  constructor(id: BackendId, hold = false) {
+    this.id = id;
+    this.hold = hold;
+  }
+
+  isAvailable(): boolean {
+    return true;
+  }
+
+  async start(_ctx: BackendContext): Promise<void> {
+    this.startCalls++;
+    if (this.hold) {
+      await new Promise<void>((resolve) => {
+        this.release = resolve;
+      });
+    }
+  }
+
+  /** Let a held `start()` resolve (simulates the backend becoming ready). */
+  releaseStart(): void {
+    this.release?.();
+    this.release = null;
+  }
+
+  async teardown(): Promise<void> {
+    this.teardownCalls++;
+  }
+
+  send(): void {}
+
+  status(): BackendStatus {
+    return { state: 'ready', message: 'fake' };
+  }
+
+  onStatusChange(): () => void {
+    return () => {};
+  }
+}
+
+test('a switch requested mid-switch is queued and applied, not dropped (L19)', async () => {
+  const midi = new FakeBackend('midi', /* hold */ true);
+  const osc = new FakeBackend('osc');
+  const manager = new BackendManager(makeEngine(), { midi, osc });
+  manager.setContext(makeCtx());
+
+  // Kick off a switch to 'midi' whose start() we hold open, simulating a
+  // switch genuinely in flight (e.g. an async backend.start()).
+  const first = manager.setActive('midi');
+
+  // While 'midi' is still starting, request 'osc'. Pre-fix this silently
+  // returned (BackendManager.setActive:131 `if (... || this.switching) return`)
+  // and 'osc' was never applied once 'midi' finished starting.
+  const second = manager.setActive('osc');
+
+  expect(manager.getActiveId()).toBe('midi'); // still mid-switch
+  midi.releaseStart();
+  await first;
+  await second;
+  // Give the queued re-run (kicked off in setActive's `finally`) a tick to
+  // settle — its own start() is not held, so one microtask flush suffices.
+  await Promise.resolve();
+  await Promise.resolve();
+
+  expect(manager.getActiveId()).toBe('osc');
+  expect(osc.startCalls).toBe(1);
+});
+
+test('rapid repeated switches to the SAME pending id only apply it once', async () => {
+  const midi = new FakeBackend('midi', /* hold */ true);
+  const osc = new FakeBackend('osc');
+  const manager = new BackendManager(makeEngine(), { midi, osc });
+  manager.setContext(makeCtx());
+
+  const first = manager.setActive('midi');
+  void manager.setActive('osc');
+  void manager.setActive('osc'); // repeated request for the same pending id
+  void manager.setActive('osc');
+
+  midi.releaseStart();
+  await first;
+  await Promise.resolve();
+  await Promise.resolve();
+  await Promise.resolve();
+
+  expect(manager.getActiveId()).toBe('osc');
+  // Only ONE extra switch should have actually run (no repeated re-queueing
+  // beyond the single pending slot — the infinite-loop guard).
+  expect(osc.startCalls).toBe(1);
+});
+
+// NOTE: `manifold/package.json`'s `test` script is `bun test src
+// tests/pipeline-golden.test.ts` — an explicit file list, not a directory
+// glob, so this file (like any other new file under tests/) is NOT picked up
+// by `bun run test` as currently wired. Verified directly with
+// `bun test tests/backend-manager-switch.test.ts`. Wiring `tests/` in as a
+// whole is a one-line package.json change outside this group's file scope
+// (see the handoff note in the accompanying report).

manifold/tests/input-vector-truncation.test.ts

@@ -0,0 +1,132 @@
+/**
+ * S10 regression (simplification audit): VCV bridged mode must drive the
+ * module with the FULL raw input vector, not just the first two axes.
+ *
+ * Two independent halves of the bug, tested separately:
+ *  (a) `Spine.lastRawInputs` — the buffer `EngineApi.inputVector()` now
+ *      delegates to directly — must hold every active axis, not just X/Y.
+ *      Before the fix this field was PRIVATE (`private lastRawInputs`) and
+ *      `EngineApi.inputVector()` returned a fresh `[lastRawX, lastRawY]`
+ *      2-element array, so this test would not even have compiled — a
+ *      stronger signal than a runtime failure. (`EngineApi` itself needs a
+ *      real loaded WASM module to construct, which this suite avoids per the
+ *      existing convention in tests/pipeline-golden.test.ts / wasm-load.ts —
+ *      "the ML surface is exercised elsewhere" — so this drives Spine
+ *      directly with a minimal fake `WasmIML`, which is exactly the surface
+ *      `EngineApi.inputVector()` now just forwards.)
+ *  (b) `VcvBackend.send()` must dead-zone over the FULL vector, not just
+ *      indices 0/1 — otherwise a change on axis 2+ (a gamepad stick or a
+ *      learned MIDI CC beyond the XY pair) is silently swallowed even once
+ *      `setInputVector` receives it.
+ *
+ * Run with `bun test tests/input-vector-truncation.test.ts` (see the NOTE at
+ * the bottom of tests/backend-manager-switch.test.ts re: `bun run test`
+ * wiring — the same applies here).
+ */
+import { expect, test } from 'bun:test';
+import { Spine } from '../src/engine/spine';
+import type { WasmIML } from '../src/engine/wasm-iml';
+import { VcvBackend } from '../src/backends/vcv-backend';
+import type { BackendContext, OutputMapping } from '../src/backends/backend';
+
+// ---- (a) Spine.lastRawInputs -------------------------------------------
+
+/** Minimal fake satisfying exactly the WasmIML surface `Spine` calls (see
+ *  spine.ts: attach/setInputs/reprocess). No real inference — just plumbing,
+ *  so this stays independent of the actual WASM build. */
+function makeFakeIml(outputSize = 8): WasmIML {
+  return {
+    architecture: { inputSize: 2, hidden: [0, 0, 0] as [number, number, number], outputSize, numLayers: 3 },
+    setInputConfig: () => {},
+    setOutputConfig: () => {},
+    setOutputFreezeMask: () => {},
+    resetInput: () => {},
+    resetOutput: () => {},
+    processInput: (x: number, y: number) => ({ x, y, frozen: false }),
+    setInput: () => {},
+    processInto: (buf: Float32Array) => buf.fill(0),
+    processOutput: () => {},
+  } as unknown as WasmIML;
+}
+
+test('Spine.lastRawInputs retains the FULL N-D raw input vector, not just X/Y', () => {
+  const spine = new Spine();
+  spine.attach(makeFakeIml(), null);
+  spine.setState({ inputSize: 5 });
+  spine.setInputs([0.1, 0.2, 0.3, 0.4, 0.5]);
+
+  // Compare through Float32Array on both sides — `lastRawInputs` is f32, so a
+  // plain f64 literal array would spuriously mismatch on rounding (e.g. 0.1 →
+  // 0.10000000149011612), not on the axis-count truncation this test targets.
+  expect(Array.from(spine.lastRawInputs)).toEqual(
+    Array.from(new Float32Array([0.1, 0.2, 0.3, 0.4, 0.5])),
+  );
+  // The old 2-D extraction (`[lastRawX, lastRawY]`) is still available for
+  // the 2-D pad path, but must not be what a 5-D-aware consumer reads.
+  expect(spine.lastRawInputs.length).toBeGreaterThan(2);
+});
+
+// ---- (b) VcvBackend full-length dead-zone -------------------------------
+
+function liveMapping(): OutputMapping {
+  return { state: 'live', muted: false, min: 0, max: 1, curve: 0.5, fixedValue: 0 };
+}
+
+function makeCtx(outputCount: number): BackendContext {
+  return {
+    modeId: 'test',
+    outputCount,
+    mappings: Array.from({ length: outputCount }, liveMapping),
+    names: Array.from({ length: outputCount }, (_, i) => `out${i}`),
+  };
+}
+
+/** Swap in a fake transport so `send()` runs without a real WebSocket. */
+function fakeClient() {
+  const sentInputs: number[][] = [];
+  return { connected: true, sendInput: (v: ReadonlyArray<number>) => sentInputs.push(Array.from(v)), sendParams: () => {}, sentInputs };
+}
+
+/** Push `send()`'s internal 50ms send-interval timer far into the past so the
+ *  throttle never blocks a test call regardless of how early in the process
+ *  lifetime `performance.now()` currently reads. */
+function unthrottle(vcv: VcvBackend): void {
+  (vcv as unknown as { lastSendMs: number }).lastSendMs = -1e9;
+}
+
+test('VcvBackend.send streams a 5-D input vector in full (not truncated to 2)', () => {
+  const vcv = new VcvBackend();
+  (vcv as unknown as { ctx: BackendContext }).ctx = makeCtx(4);
+  const client = fakeClient();
+  (vcv as unknown as { client: unknown }).client = client;
+  unthrottle(vcv);
+
+  vcv.setInputVector([0.1, 0.2, 0.9, 0.4, 0.55]);
+  vcv.send(new Float32Array(4));
+
+  expect(client.sentInputs).toEqual([[0.1, 0.2, 0.9, 0.4, 0.55]]);
+});
+
+test('VcvBackend.send dead-zones over the FULL vector — a change on axis 3 alone still resends', () => {
+  const vcv = new VcvBackend();
+  (vcv as unknown as { ctx: BackendContext }).ctx = makeCtx(4);
+  const client = fakeClient();
+  (vcv as unknown as { client: unknown }).client = client;
+  unthrottle(vcv);
+
+  vcv.setInputVector([0.5, 0.5, 0.5, 0.5]);
+  vcv.send(new Float32Array(4)); // first send always fires (sentinel init)
+  expect(client.sentInputs.length).toBe(1);
+
+  // Bypass the internal 50ms send-interval throttle for the second call.
+  unthrottle(vcv);
+
+  // Only axis index 3 moves; X/Y (indices 0/1) are unchanged. Before the S10
+  // fix, VcvBackend's dead-zone check only ever looked at indices 0/1, so
+  // this change would have been silently dropped — no resend.
+  vcv.setInputVector([0.5, 0.5, 0.5, 0.9]);
+  vcv.send(new Float32Array(4));
+
+  expect(client.sentInputs.length).toBe(2);
+  expect(client.sentInputs[1]).toEqual([0.5, 0.5, 0.5, 0.9]);
+});

manifold/tests/midi-notify-churn.test.ts

@@ -0,0 +1,86 @@
+/**
+ * L18 regression (simplification audit): `WebMidiInputSource` must notify
+ * `onBindingsChange` listeners only when the binding LIST changes (learn
+ * capture, clearBinding, clearAllBindings) — NOT on every incoming CC value
+ * update. Pre-fix, every CC message on an already-learned axis pushed a full
+ * bindings-array snapshot to every listener (a React state update per MIDI
+ * message in the real app, via useInputLayer.ts's `onBindingsChange`
+ * subscription).
+ *
+ * `onMessage` is private — there is no other public seam to feed synthetic
+ * MIDI bytes in, so this test invokes it through a narrow cast (a normal
+ * white-box technique for a class with no public message-injection API).
+ *
+ * Run with `bun test tests/midi-notify-churn.test.ts` (see the `bun run test`
+ * wiring note in tests/backend-manager-switch.test.ts — the same applies).
+ */
+import { expect, test } from 'bun:test';
+import { WebMidiInputSource } from '../src/inputs/midi-input-source';
+
+function ccMessage(cc: number, channel1based: number, value7bit: number): MIDIMessageEvent {
+  const statusByte = 0xb0 | ((channel1based - 1) & 0x0f);
+  return { data: new Uint8Array([statusByte, cc, value7bit]) } as unknown as MIDIMessageEvent;
+}
+
+function feedCc(midi: WebMidiInputSource, cc: number, channel: number, value7bit: number): void {
+  (midi as unknown as { onMessage(e: MIDIMessageEvent): void }).onMessage(ccMessage(cc, channel, value7bit));
+}
+
+test('repeated CC value updates on an EXISTING binding do not re-notify', () => {
+  const midi = new WebMidiInputSource();
+  let notifyCount = 0;
+  midi.onBindingsChange(() => {
+    notifyCount++;
+  });
+
+  midi.armLearn(true);
+  feedCc(midi, 74, 1, 10); // new axis captured — the list changed → 1 notify
+  expect(notifyCount).toBe(1);
+  midi.armLearn(false);
+
+  // Flood the SAME learned CC with 50 more value updates (the "wiggle a
+  // fader" case that used to flood React with one state update each).
+  for (let v = 0; v < 50; v++) feedCc(midi, 74, 1, v);
+
+  expect(notifyCount).toBe(1); // still just the one list-change notify
+  expect(midi.getBindings()[0].value).toBeCloseTo(49 / 127, 5); // value still latches
+});
+
+test('learn capture / clearBinding / clearAllBindings still notify (the list DID change)', () => {
+  const midi = new WebMidiInputSource();
+  let notifyCount = 0;
+  midi.onBindingsChange(() => {
+    notifyCount++;
+  });
+
+  midi.armLearn(true);
+  feedCc(midi, 1, 1, 10);
+  feedCc(midi, 2, 1, 20);
+  expect(notifyCount).toBe(2); // two NEW axes captured
+  midi.armLearn(false);
+
+  midi.clearBinding(0);
+  expect(notifyCount).toBe(3);
+  midi.clearAllBindings();
+  expect(notifyCount).toBe(4);
+});
+
+test('note gate updates never notify (no note binding can ever be created)', () => {
+  const midi = new WebMidiInputSource();
+  let notifyCount = 0;
+  midi.onBindingsChange(() => {
+    notifyCount++;
+  });
+
+  // Note ON then OFF, repeatedly — no path creates a 'note' binding, so the
+  // list never changes and this must never notify.
+  const noteOn = { data: new Uint8Array([0x90, 60, 100]) } as unknown as MIDIMessageEvent;
+  const noteOff = { data: new Uint8Array([0x80, 60, 0]) } as unknown as MIDIMessageEvent;
+  const inject = midi as unknown as { onMessage(e: MIDIMessageEvent): void };
+  for (let i = 0; i < 10; i++) {
+    inject.onMessage(noteOn);
+    inject.onMessage(noteOff);
+  }
+
+  expect(notifyCount).toBe(0);
+});