Initial Commit

packages/ui/react/react-audio/src/hooks/index.ts

@@ -0,0 +1,55 @@
+export {
+    type AnalyserLike,
+    type UseAnalyserOptions,
+    type UseAnalyserResult,
+    useAnalyser,
+} from "./use-analyser/index.js";
+export { useAudioEngine } from "./use-audio-engine/use-audio-engine.js";
+export { useAudioFxPlugin } from "./use-audio-fx-plugin/use-audio-fx-plugin.js";
+export { useBus } from "./use-bus/use-bus.js";
+export { useChainPlugin } from "./use-chain-plugin/use-chain-plugin.js";
+export {
+    type UseChainSnapshotResult,
+    useChainSnapshot,
+} from "./use-chain-snapshot/use-chain-snapshot.js";
+export { useEngineState } from "./use-engine-state/use-engine-state.js";
+export {
+    type LearnTarget,
+    type MidiControllerRegistry,
+    MidiControllerRegistryContext,
+    type UseMidiControllerResult,
+    useMidiController,
+} from "./use-midi-controller/use-midi-controller.js";
+export {
+    type UseParameterResult,
+    useParameter,
+} from "./use-parameter/use-parameter.js";
+export {
+    type PlaylistItem,
+    type PlaylistRepeat,
+    type UsePlaylistOptions,
+    type UsePlaylistResult,
+    usePlaylist,
+} from "./use-playlist/index.js";
+export {
+    type UsePluginChainResult,
+    usePluginChain,
+} from "./use-plugin-chain/use-plugin-chain.js";
+export {
+    type UsePresetResult,
+    usePreset,
+} from "./use-preset/use-preset.js";
+export {
+    useAudioContextOrThrow,
+    useProviderStateOrThrow,
+} from "./use-provider-state.js";
+export { useTimeline } from "./use-timeline/use-timeline.js";
+export {
+    type UseTrackResult,
+    useTrack,
+} from "./use-track/use-track.js";
+export {
+    type UseTransportResult,
+    useTransport,
+} from "./use-transport/use-transport.js";
+export { useTransportTime } from "./use-transport-time/use-transport-time.js";

packages/ui/react/react-audio/src/hooks/use-analyser/index.ts

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+export { useAnalyser } from "./use-analyser.js";
+export type {
+    AnalyserLike,
+    UseAnalyserOptions,
+    UseAnalyserResult,
+} from "./use-analyser.types.js";

packages/ui/react/react-audio/src/hooks/use-analyser/use-analyser.md

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+# `hooks/use-analyser`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useAnalyser(opts?)` polls an `AnalyserNode`-shaped source and
+returns the latest byte-magnitude FFT frame plus the matching
+time-domain (waveform) frame. It is the data feed for the family's
+two stock visualisers — `<WaveformVisualizer>` and
+`<SpectrumAnalyzer>` — and for any consumer-built `<canvas>`
+visualiser that wants live spectrum data without dealing with
+`AudioContext` or `AnalyserNode` lifecycle.
+
+The hook deliberately does **not** create or own an `AnalyserNode`.
+The audio engine builds one analyser per track inside its
+`TrackSubgraph`, and the player tier hosts the master analyser on
+the source chain; the consumer hands either node to this hook. Two
+consumers reading the same analyser independently each get their
+own buffer pair so they cannot tear each other's frame reads.
+
+## Features
+
+- Polls at a caller-tunable interval (default 16 ms ≈ 60 Hz).
+- Auto-configures `fftSize`, `smoothingTimeConstant`, `minDecibels`,
+  `maxDecibels` on the analyser on every change.
+- Lazy `factory` fallback for when the analyser is not available at
+  mount (typical: engine still initialising).
+- Identity-stable `Uint8Array` buffers — mutated in place; the hook
+  never allocates per frame.
+- Cleanup on unmount cancels the interval.
+
+## Usage: Basic
+
+```tsx
+import { useAnalyser } from "@suaveplan/react-audio";
+
+function Spectrum({ analyser }) {
+    const { frequency } = useAnalyser({ analyser, fftSize: 1024 });
+    return (
+        <div role="img" aria-label="spectrum">
+            {Array.from(frequency.slice(0, 32)).map((v, i) => (
+                <span key={i} style={{ height: `${v}px` }} />
+            ))}
+        </div>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useAnalyser } from "@suaveplan/react-audio";
+
+// Resolve the engine's per-track analyser via the graph snapshot.
+function trackAnalyserFactory(adapter, trackId) {
+    return () => {
+        const snap = adapter.snapshotGraph();
+        const node = snap.nodes.find(
+            (n) => n.id === `${trackId}:analyser`
+        );
+        return node?.ref ?? null;
+    };
+}
+
+function TrackVisualizer({ adapter, trackId }) {
+    const { frequency, waveform, analyser } = useAnalyser({
+        factory: trackAnalyserFactory(adapter, trackId),
+        intervalMs: 33, // ~30 Hz to save CPU
+        fftSize: 2048,
+        smoothingTimeConstant: 0.6,
+    });
+    if (!analyser) return <span>Connecting…</span>;
+    return (
+        <canvas
+            ref={(c) => drawSpectrum(c, frequency, waveform)}
+            width={512}
+            height={128}
+        />
+    );
+}
+```
+
+## API Reference
+
+- `useAnalyser(opts?: UseAnalyserOptions): UseAnalyserResult`
+- `UseAnalyserOptions`:
+    - `analyser?: AnalyserLike | null` — direct ref; supersedes `factory`.
+    - `factory?: () => AnalyserLike | null` — lazy resolver, retried per tick.
+    - `intervalMs?: number` — poll interval (default 16).
+    - `fftSize?: number` — power-of-2 in `[32, 32768]` (default 2048).
+    - `smoothingTimeConstant?: number` — `[0, 1]` (default 0.8).
+    - `minDecibels?: number` — default `-100`.
+    - `maxDecibels?: number` — default `-30`.
+- `UseAnalyserResult`:
+    - `analyser: AnalyserLike | null` — resolved instance or `null`.
+    - `frequency: Uint8Array` — byte-magnitude FFT, identity-stable.
+    - `waveform: Uint8Array` — byte time-domain, identity-stable.
+
+## Implementation Notes
+
+The hook owns three refs: the resolved analyser, the factory, and
+the buffer pair. Buffers are reallocated when `analyser` or
+`fftSize` changes (the new `frequencyBinCount` determines length).
+Polling uses `setInterval` rather than `requestAnimationFrame`
+because the former is deterministic under happy-dom — the same
+reason `useTransportTime` makes the same choice.
+
+The factory fallback is invoked on every tick until it returns a
+non-`null` value, then never again. This lets the consumer mount
+the hook before the engine finishes async init without races: the
+visualiser simply renders zeros until the analyser appears, then
+continues seamlessly.
+
+The hook is engine-agnostic by design — it accepts the structural
+`AnalyserLike` shape, so consumers can stub it in tests with three
+lines of code and there is no hidden `AudioContext` dependency
+poisoning tree-shake or SSR.

packages/ui/react/react-audio/src/hooks/use-analyser/use-analyser.test.ts

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+import { describe, expect, it, vi } from "@suaveplan/testing/runner";
+import { act, renderHook } from "@testing-library/react";
+import { useAnalyser } from "./use-analyser.js";
+import type { AnalyserLike } from "./use-analyser.types.js";
+
+function makeFakeAnalyser(bins = 16): AnalyserLike & {
+    freqCalls: number;
+    waveCalls: number;
+} {
+    const state = {
+        fftSize: 2048,
+        frequencyBinCount: bins,
+        minDecibels: -100,
+        maxDecibels: -30,
+        smoothingTimeConstant: 0.8,
+        freqCalls: 0,
+        waveCalls: 0,
+        getByteFrequencyData(out: Uint8Array) {
+            state.freqCalls += 1;
+            out[0] = (state.freqCalls % 250) + 1;
+        },
+        getByteTimeDomainData(out: Uint8Array) {
+            state.waveCalls += 1;
+            out[0] = ((state.waveCalls * 2) % 250) + 1;
+        },
+    };
+    Object.defineProperty(state, "frequencyBinCount", {
+        get: () => Math.max(1, Math.floor(state.fftSize / 2)),
+    });
+    return state as unknown as AnalyserLike & {
+        freqCalls: number;
+        waveCalls: number;
+    };
+}
+
+describe("useAnalyser", () => {
+    it("returns null analyser + empty buffers when no source provided", {
+        timeout: 5000,
+    }, () => {
+        const { result, unmount } = renderHook(() => useAnalyser());
+        expect(result.current.analyser).toBeNull();
+        expect(result.current.frequency.length).toBe(0);
+        expect(result.current.waveform.length).toBe(0);
+        unmount();
+    });
+
+    it("polls the explicit analyser and writes into the shared buffer", {
+        timeout: 5000,
+    }, () => {
+        vi.useFakeTimers();
+        try {
+            const a = makeFakeAnalyser(8);
+            const { result, unmount } = renderHook(() =>
+                useAnalyser({ analyser: a, intervalMs: 5, fftSize: 16 })
+            );
+            expect(result.current.analyser).toBe(a);
+            expect(result.current.frequency.length).toBe(8);
+            act(() => {
+                vi.advanceTimersByTime(20);
+            });
+            expect(a.freqCalls).toBeGreaterThan(0);
+            expect(a.waveCalls).toBeGreaterThan(0);
+            expect(result.current.frequency[0]).toBeGreaterThan(0);
+            unmount();
+        } finally {
+            vi.useRealTimers();
+        }
+    });
+
+    it("applies fftSize/smoothing/min-max on the analyser", {
+        timeout: 5000,
+    }, () => {
+        const a = makeFakeAnalyser();
+        renderHook(() =>
+            useAnalyser({
+                analyser: a,
+                fftSize: 512,
+                smoothingTimeConstant: 0.3,
+                minDecibels: -120,
+                maxDecibels: -20,
+            })
+        );
+        expect(a.fftSize).toBe(512);
+        expect(a.smoothingTimeConstant).toBe(0.3);
+        expect(a.minDecibels).toBe(-120);
+        expect(a.maxDecibels).toBe(-20);
+    });
+
+    it("resolves via factory on tick, then stops re-resolving", {
+        timeout: 5000,
+    }, () => {
+        vi.useFakeTimers();
+        try {
+            let calls = 0;
+            const a = makeFakeAnalyser();
+            const factory = () => {
+                calls += 1;
+                return calls >= 2 ? a : null;
+            };
+            const { result } = renderHook(() =>
+                useAnalyser({ factory, intervalMs: 5 })
+            );
+            expect(result.current.analyser).toBeNull();
+            act(() => {
+                vi.advanceTimersByTime(6);
+            });
+            // First tick: factory returns null; resolved still null.
+            act(() => {
+                vi.advanceTimersByTime(6);
+            });
+            expect(result.current.analyser).toBe(a);
+            // Once resolved, factory should not be called again.
+            const beforeCalls = calls;
+            act(() => {
+                vi.advanceTimersByTime(20);
+            });
+            expect(calls).toBe(beforeCalls);
+        } finally {
+            vi.useRealTimers();
+        }
+    });
+
+    it("swapping the analyser prop reconfigures buffers", {
+        timeout: 5000,
+    }, () => {
+        const a1 = makeFakeAnalyser(8);
+        const a2 = makeFakeAnalyser(16);
+        const { result, rerender } = renderHook(
+            ({ a }: { a: typeof a1 }) =>
+                useAnalyser({ analyser: a, fftSize: 32 }),
+            { initialProps: { a: a1 } }
+        );
+        expect(result.current.frequency.length).toBeGreaterThan(0);
+        const first = result.current.frequency;
+        rerender({ a: a2 });
+        // Buffer identity may change; instance must be a2.
+        expect(result.current.analyser).toBe(a2);
+        // Different fftSize bin count → different length.
+        expect(result.current.frequency.length).toBe(Math.floor(32 / 2));
+        expect(first).not.toBe(result.current.frequency);
+    });
+
+    it("setting analyser to null disables polling", { timeout: 5000 }, () => {
+        vi.useFakeTimers();
+        try {
+            const a = makeFakeAnalyser();
+            const { rerender } = renderHook(
+                ({ x }: { x: typeof a | null }) =>
+                    useAnalyser({ analyser: x, intervalMs: 5 }),
+                { initialProps: { x: a as typeof a | null } }
+            );
+            act(() => {
+                vi.advanceTimersByTime(20);
+            });
+            const before = a.freqCalls;
+            rerender({ x: null });
+            act(() => {
+                vi.advanceTimersByTime(20);
+            });
+            // After null, no new poll calls land on `a`.
+            expect(a.freqCalls).toBe(before);
+        } finally {
+            vi.useRealTimers();
+        }
+    });
+
+    it("cleans up the interval on unmount", { timeout: 5000 }, () => {
+        vi.useFakeTimers();
+        try {
+            const a = makeFakeAnalyser();
+            const { unmount } = renderHook(() =>
+                useAnalyser({ analyser: a, intervalMs: 5 })
+            );
+            act(() => {
+                vi.advanceTimersByTime(10);
+            });
+            const before = a.freqCalls;
+            unmount();
+            act(() => {
+                vi.advanceTimersByTime(50);
+            });
+            expect(a.freqCalls).toBe(before);
+        } finally {
+            vi.useRealTimers();
+        }
+    });
+
+    it("factory returning null indefinitely keeps analyser null", {
+        timeout: 5000,
+    }, () => {
+        vi.useFakeTimers();
+        try {
+            const { result } = renderHook(() =>
+                useAnalyser({ factory: () => null, intervalMs: 5 })
+            );
+            act(() => {
+                vi.advanceTimersByTime(30);
+            });
+            expect(result.current.analyser).toBeNull();
+        } finally {
+            vi.useRealTimers();
+        }
+    });
+
+    it("no factory, no analyser → tick is a no-op", { timeout: 5000 }, () => {
+        vi.useFakeTimers();
+        try {
+            const { result } = renderHook(() => useAnalyser({ intervalMs: 5 }));
+            act(() => {
+                vi.advanceTimersByTime(20);
+            });
+            expect(result.current.analyser).toBeNull();
+        } finally {
+            vi.useRealTimers();
+        }
+    });
+
+    it("changing fftSize after mount reallocates buffers", {
+        timeout: 5000,
+    }, () => {
+        const a = makeFakeAnalyser();
+        const { result, rerender } = renderHook(
+            ({ size }: { size: number }) =>
+                useAnalyser({ analyser: a, fftSize: size }),
+            { initialProps: { size: 32 } }
+        );
+        expect(result.current.frequency.length).toBe(16);
+        rerender({ size: 64 });
+        expect(result.current.frequency.length).toBe(32);
+        expect(a.fftSize).toBe(64);
+    });
+
+    it("intervalMs <= 0 is clamped to 1", { timeout: 5000 }, () => {
+        vi.useFakeTimers();
+        try {
+            const a = makeFakeAnalyser();
+            renderHook(() => useAnalyser({ analyser: a, intervalMs: 0 }));
+            act(() => {
+                vi.advanceTimersByTime(5);
+            });
+            expect(a.freqCalls).toBeGreaterThan(0);
+        } finally {
+            vi.useRealTimers();
+        }
+    });
+});

packages/ui/react/react-audio/src/hooks/use-analyser/use-analyser.ts

@@ -0,0 +1,160 @@
+import { useCallback, useEffect, useRef, useState } from "react";
+import type {
+    AnalyserLike,
+    UseAnalyserOptions,
+    UseAnalyserResult,
+} from "./use-analyser.types.js";
+
+const DEFAULT_FFT_SIZE = 2048;
+const DEFAULT_INTERVAL_MS = 16;
+const DEFAULT_SMOOTHING = 0.8;
+const DEFAULT_MIN_DB = -100;
+const DEFAULT_MAX_DB = -30;
+
+/**
+ * `useAnalyser(opts?)` polls an `AnalyserNode`-shaped source and
+ * returns the latest byte-magnitude FFT frame plus the matching
+ * time-domain (waveform) frame. The hook does not create an
+ * `AudioContext` and does not add itself to the audio graph — the
+ * consumer either supplies an `AnalyserLike` directly or hands in a
+ * lazy `factory` that returns one (e.g. resolved from
+ * `BrowserTimelineAdapter.snapshotGraph()` once async init finishes).
+ *
+ * The returned `Uint8Array` buffers are owned by the hook and
+ * mutated in place every poll; callers must copy if they need a
+ * stable snapshot. Buffers are reallocated when `analyser` or
+ * `fftSize` changes.
+ *
+ * Cleanup on unmount cancels the interval. Two consumers reading
+ * the same analyser independently each get their own buffer pair so
+ * they cannot tear each other's reads.
+ */
+export function useAnalyser(opts: UseAnalyserOptions = {}): UseAnalyserResult {
+    const {
+        analyser: analyserOpt,
+        factory,
+        intervalMs = DEFAULT_INTERVAL_MS,
+        fftSize = DEFAULT_FFT_SIZE,
+        smoothingTimeConstant = DEFAULT_SMOOTHING,
+        minDecibels = DEFAULT_MIN_DB,
+        maxDecibels = DEFAULT_MAX_DB,
+    } = opts;
+
+    const resolvedRef = useRef<AnalyserLike | null>(null);
+    const factoryRef = useRef<typeof factory>(factory);
+    factoryRef.current = factory;
+
+    const configureAndBuild = useCallback(
+        (a: AnalyserLike): { frequency: Uint8Array; waveform: Uint8Array } => {
+            a.fftSize = fftSize;
+            a.smoothingTimeConstant = smoothingTimeConstant;
+            a.minDecibels = minDecibels;
+            a.maxDecibels = maxDecibels;
+            const bins = a.frequencyBinCount;
+            return {
+                frequency: new Uint8Array(bins),
+                waveform: new Uint8Array(bins),
+            };
+        },
+        [fftSize, smoothingTimeConstant, minDecibels, maxDecibels]
+    );
+
+    // Synchronously initialise resolved + buffers from `analyserOpt`
+    // so the very first render returns the live buffer pair (not a
+    // throwaway empty array later swapped out from an effect).
+    const initialAnalyser = analyserOpt ?? null;
+    if (initialAnalyser !== null && resolvedRef.current === null) {
+        resolvedRef.current = initialAnalyser;
+    }
+
+    const [state, setState] = useState<{
+        analyser: AnalyserLike | null;
+        frequency: Uint8Array;
+        waveform: Uint8Array;
+    }>(() => {
+        if (initialAnalyser) {
+            const bufs = configureAndBuild(initialAnalyser);
+            return { analyser: initialAnalyser, ...bufs };
+        }
+        return {
+            analyser: null,
+            frequency: new Uint8Array(0),
+            waveform: new Uint8Array(0),
+        };
+    });
+
+    const swap = useCallback(
+        (a: AnalyserLike | null) => {
+            resolvedRef.current = a;
+            if (a) {
+                const bufs = configureAndBuild(a);
+                setState({ analyser: a, ...bufs });
+            } else {
+                setState({
+                    analyser: null,
+                    frequency: new Uint8Array(0),
+                    waveform: new Uint8Array(0),
+                });
+            }
+        },
+        [configureAndBuild]
+    );
+
+    const lastConfigKeyRef = useRef<string>(
+        initialAnalyser
+            ? `${fftSize}/${smoothingTimeConstant}/${minDecibels}/${maxDecibels}`
+            : ""
+    );
+
+    // Sync the explicit `analyser` prop.
+    useEffect(() => {
+        if (analyserOpt !== undefined && analyserOpt !== resolvedRef.current) {
+            swap(analyserOpt);
+            lastConfigKeyRef.current = analyserOpt
+                ? `${fftSize}/${smoothingTimeConstant}/${minDecibels}/${maxDecibels}`
+                : "";
+        }
+    }, [
+        analyserOpt,
+        swap,
+        fftSize,
+        smoothingTimeConstant,
+        minDecibels,
+        maxDecibels,
+    ]);
+
+    // Reconfigure on fft/smoothing changes (skip if already at this key).
+    useEffect(() => {
+        const key = `${fftSize}/${smoothingTimeConstant}/${minDecibels}/${maxDecibels}`;
+        if (resolvedRef.current !== null && key !== lastConfigKeyRef.current) {
+            lastConfigKeyRef.current = key;
+            swap(resolvedRef.current);
+        }
+    }, [fftSize, smoothingTimeConstant, minDecibels, maxDecibels, swap]);
+
+    const stateRef = useRef(state);
+    stateRef.current = state;
+
+    useEffect(() => {
+        const tick = (): void => {
+            let a = resolvedRef.current;
+            if (!a && factoryRef.current) {
+                const made = factoryRef.current();
+                if (made) {
+                    swap(made);
+                    a = made;
+                }
+            }
+            if (!a) return;
+            const bufs = stateRef.current;
+            a.getByteFrequencyData(bufs.frequency);
+            a.getByteTimeDomainData(bufs.waveform);
+        };
+        const id = setInterval(tick, Math.max(1, intervalMs));
+        return () => {
+            clearInterval(id);
+        };
+    }, [intervalMs, swap]);
+
+    return state;
+}

packages/ui/react/react-audio/src/hooks/use-analyser/use-analyser.types.ts

@@ -0,0 +1,59 @@
+/**
+ * Minimal `AnalyserNode`-shaped contract. Matches the subset of the
+ * Web Audio `AnalyserNode` interface this hook reads. Declared as a
+ * structural type so the hook works equally well against the real
+ * `AnalyserNode`, a stub in tests, or the engine's internal
+ * `analyser`-tagged graph node returned from
+ * `BrowserTimelineAdapter.snapshotGraph()`.
+ */
+export interface AnalyserLike {
+    fftSize: number;
+    readonly frequencyBinCount: number;
+    minDecibels: number;
+    maxDecibels: number;
+    smoothingTimeConstant: number;
+    getByteFrequencyData(out: Uint8Array): void;
+    getByteTimeDomainData(out: Uint8Array): void;
+}
+
+export interface UseAnalyserOptions {
+    /**
+     * Direct analyser reference. If supplied, `factory` is ignored.
+     * Pass `null` to disable polling (the hook will return zero-filled
+     * buffers and `analyser: null`).
+     */
+    readonly analyser?: AnalyserLike | null;
+    /**
+     * Lazy factory invoked once on first sample if `analyser` is
+     * absent. Return `null` to defer (the hook will retry on next
+     * sample). Useful for grabbing the engine's per-track analyser
+     * after async init has resolved.
+     */
+    readonly factory?: () => AnalyserLike | null;
+    /** Sample interval in ms. Default 16 (≈60 Hz). */
+    readonly intervalMs?: number;
+    /** FFT size. Must be a power of 2 in `[32, 32768]`. Default 2048. */
+    readonly fftSize?: number;
+    /** Smoothing time constant in `[0, 1]`. Default 0.8. */
+    readonly smoothingTimeConstant?: number;
+    /** Minimum dB cutoff. Default -100. */
+    readonly minDecibels?: number;
+    /** Maximum dB cutoff. Default -30. */
+    readonly maxDecibels?: number;
+}
+
+export interface UseAnalyserResult {
+    /** Resolved analyser, or `null` if neither prop nor factory yielded one. */
+    readonly analyser: AnalyserLike | null;
+    /**
+     * Latest byte-magnitude frequency frame (length =
+     * `analyser.frequencyBinCount`). Identity-stable across renders;
+     * mutated in place — copy if you want a snapshot.
+     */
+    readonly frequency: Uint8Array;
+    /**
+     * Latest byte time-domain (waveform) frame. Same identity-stable
+     * mutated-in-place contract as `frequency`.
+     */
+    readonly waveform: Uint8Array;
+}

packages/ui/react/react-audio/src/hooks/use-audio-engine/use-audio-engine.md

@@ -0,0 +1,73 @@
+# `hooks/use-audio-engine`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useAudioEngine()` returns the full resolved `ProviderState` bundle —
+the adapter, the `TimelineEngine`, the `Transport`, the
+`ProviderBusRegistry`, the `PluginRegistry`, the consumer-supplied
+preset store (or `undefined`), and the configured `sampleRateHz`.
+It throws `REACT_AUDIO.NO_PROVIDER` outside the provider and
+`REACT_AUDIO.PROVIDER_PENDING` during the async init window. It is
+the escape hatch for code that needs the entire bundle at once;
+prefer the narrower hooks (`useTransport`, `useTimeline`, …) when
+you only need one entity, as they minimise re-render scope.
+
+## Features
+
+- Returns `ProviderState` — a readonly bundle.
+- Throws `REACT_AUDIO.NO_PROVIDER` outside `<AudioProvider>`.
+- Throws `REACT_AUDIO.PROVIDER_PENDING` while engine init is in
+  flight.
+- Stable reference across re-renders within a single ready phase.
+
+## Usage: Basic
+
+```tsx
+import { useAudioEngine } from "@suaveplan/react-audio";
+
+function Diagnostics() {
+    const { engine, transport, sampleRateHz } = useAudioEngine();
+    return (
+        <pre>
+            engine.lookAhead = {engine.lookAhead}; transport.state ={" "}
+            {transport.state}; ui-sampleRate = {sampleRateHz} Hz
+        </pre>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useAudioEngine } from "@suaveplan/react-audio";
+
+function useRegisterPlugin(): (type: string, factory: () => AudioFxPlugin) => void {
+    const { registry } = useAudioEngine();
+    return (type, factory) => registry.register(type, factory);
+}
+```
+
+## API Reference
+
+- `useAudioEngine(): ProviderState`.
+
+## Implementation Notes
+
+The hook delegates to `useProviderStateOrThrow`, which performs the
+two structured-error checks. The returned `ProviderState` is the
+frozen object the provider published — consumers can stash it in a
+ref without cloning. Identity is stable across renders within a
+single ready phase; if the provider remounts (Strict Mode or genuine
+remount) the bundle's identity changes, which is the correct cue for
+downstream `useEffect`s keyed on `engine`/`transport` to re-bind.
+Prefer the focused hooks (`useTransport`, `useTimeline`, …) for the
+common case of "I only need one entity"; the broader bundle returned
+here triggers re-renders only when the provider itself re-publishes
+state (the focused hooks emit narrower subscriptions). Consumers
+that want to forward the engine bundle into child components without
+re-render bloat should destructure here, then memoise the
+sub-references they pass downstream.

packages/ui/react/react-audio/src/hooks/use-audio-engine/use-audio-engine.test.tsx

@@ -0,0 +1,18 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { waitFor } from "@testing-library/react";
+import { renderHookWithProvider } from "../../test-utils.js";
+import { useAudioEngine } from "./use-audio-engine.js";
+
+describe("useAudioEngine", () => {
+    it("returns the full ProviderState bundle", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => useAudioEngine());
+        await waitFor(() => expect(handle.current).toBeDefined());
+        expect(handle.current!.transport).toBeDefined();
+        expect(handle.current!.timeline).toBeDefined();
+        expect(handle.current!.buses).toBeDefined();
+        expect(handle.current!.chains).toBeDefined();
+        expect(handle.current!.registry).toBeDefined();
+    });
+});

packages/ui/react/react-audio/src/hooks/use-audio-engine/use-audio-engine.ts

@@ -0,0 +1,16 @@
+import type { ProviderState } from "../../provider/audio-context.js";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+/**
+ * Returns the full resolved `ProviderState` bundle (engine, timeline,
+ * transport, buses, registry, presetStore, sampleRateHz). Throws
+ * `REACT_AUDIO.NO_PROVIDER` outside `<AudioProvider>` and
+ * `REACT_AUDIO.PROVIDER_PENDING` while engine init is in flight.
+ *
+ * Prefer the focused hooks (`useTransport`, `useTimeline`, …) for
+ * normal use — they emit narrower change events. This hook is the
+ * escape hatch for code that needs the entire bundle in one read.
+ */
+export function useAudioEngine(): ProviderState {
+    return useProviderStateOrThrow();
+}

packages/ui/react/react-audio/src/hooks/use-audio-fx-plugin/use-audio-fx-plugin.md

@@ -0,0 +1,78 @@
+# `hooks/use-audio-fx-plugin`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useAudioFxPlugin(pluginType)` instantiates a plugin via the
+provider's `PluginRegistry.create(pluginType)` and memoises the
+result. The hook is the canonical way to obtain a one-off plugin
+instance (e.g. for a side-panel preview that is not in any chain).
+Consumers who want to insert the plugin into a chain pass the
+returned value to `usePluginChain(...).add(plugin)`.
+
+The hook does not own or register factories. The provider can
+auto-register factories via `options.plugins`; alternatively
+`useAudioEngine().registry.register(...)` lets consumers add factories
+dynamically.
+
+## Features
+
+- Instance memoised by `pluginType` for component lifetime.
+- Throws `REACT_AUDIO.NO_PROVIDER` / `REACT_AUDIO.PROVIDER_PENDING`
+  outside / before-init.
+- Throws `AudioFxError(AUDIO_FX.CHAIN_SLOT_NOT_FOUND)` if no factory
+  is registered for `pluginType`.
+
+## Usage: Basic
+
+```tsx
+import { useAudioFxPlugin } from "@suaveplan/react-audio";
+
+function PreviewEQ() {
+    const eq = useAudioFxPlugin("equaliser");
+    return <PluginPanel plugin={eq} />;
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useAudioEngine, useAudioFxPlugin, usePluginChain } from "@suaveplan/react-audio";
+import { useEffect } from "react";
+
+function EnsureRegistered() {
+    const { registry } = useAudioEngine();
+    useEffect(() => {
+        registry.register("delay", () => makeDelay());
+    }, [registry]);
+    return null;
+}
+
+function ChainAdder({ trackId }: { trackId: string }) {
+    const delay = useAudioFxPlugin("delay");
+    const { add } = usePluginChain(trackId);
+    return <button type="button" onClick={() => add(delay)}>Add delay</button>;
+}
+```
+
+## API Reference
+
+- `useAudioFxPlugin(pluginType: string): AudioFxPlugin`.
+
+## Implementation Notes
+
+The hook memoises on `[registry, pluginType]` so a remount of the
+provider (new registry identity) yields a fresh instance, but a
+re-render with the same provider and `pluginType` returns the same
+instance. The hook does not call `dispose()` on unmount because the
+plugin is typically inserted into a chain whose lifecycle owns the
+disposal. Consumers using the hook for a transient preview should
+call `plugin.dispose()` in their own `useEffect` cleanup. Plugins
+constructed by this hook are never auto-inserted into any chain —
+the caller is responsible for placement (e.g. via
+`usePluginChain(trackId).add(plugin)`). This separation lets the
+same hook back per-track inserts, side-panel previews, and one-off
+analyser taps.

packages/ui/react/react-audio/src/hooks/use-audio-fx-plugin/use-audio-fx-plugin.test.tsx

@@ -0,0 +1,30 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { waitFor } from "@testing-library/react";
+import { makeFakePlugin, renderHookWithProvider } from "../../test-utils.js";
+import { useAudioEngine } from "../use-audio-engine/use-audio-engine.js";
+import { useAudioFxPlugin } from "./use-audio-fx-plugin.js";
+
+describe("useAudioFxPlugin", () => {
+    it("instantiates a plugin from the registry", {
+        timeout: 30000,
+    }, async () => {
+        const factory = () => makeFakePlugin({ id: "synth-1" });
+        const handle = renderHookWithProvider(() => useAudioFxPlugin("fake"), {
+            options: { plugins: [{ pluginType: "fake", factory }] },
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+        expect(handle.current!.metadata.id).toBe("synth-1");
+    });
+
+    it("throws when no factory registered", { timeout: 30000 }, async () => {
+        const handle = renderHookWithProvider(() => useAudioEngine());
+        await waitFor(() => expect(handle.current).toBeDefined());
+        let caught: unknown;
+        try {
+            handle.current!.registry.create("missing-type");
+        } catch (e) {
+            caught = e;
+        }
+        expect(caught).toBeDefined();
+    });
+});

packages/ui/react/react-audio/src/hooks/use-audio-fx-plugin/use-audio-fx-plugin.ts

@@ -0,0 +1,20 @@
+import type { AudioFxPlugin } from "@suaveplan/audio-fx-plugin-base";
+import { useMemo } from "react";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+/**
+ * Instantiates a plugin by `pluginType` from the provider's
+ * `PluginRegistry`. Returns the constructed `AudioFxPlugin` instance
+ * memoised by `pluginType` — calling the hook again with the same
+ * type returns the same instance for the lifetime of the component.
+ *
+ * The hook does NOT register factories — that is the provider's job
+ * (`options.plugins`) or the consumer's via `useAudioEngine().registry.register(...)`.
+ * If no factory is registered for `pluginType`, the underlying
+ * `registry.create` throws an `AudioFxError` with code
+ * `AUDIO_FX.CHAIN_SLOT_NOT_FOUND`.
+ */
+export function useAudioFxPlugin(pluginType: string): AudioFxPlugin {
+    const { registry } = useProviderStateOrThrow();
+    return useMemo(() => registry.create(pluginType), [registry, pluginType]);
+}

packages/ui/react/react-audio/src/hooks/use-bus/use-bus.md

@@ -0,0 +1,69 @@
+# `hooks/use-bus`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useBus(name)` reads the named sidechain bus from the provider's
+`ProviderBusRegistry` and subscribes to its publish/close lifecycle.
+Returns `undefined` if no publisher has registered the name. The
+hook re-renders whenever the bus is (re)published with a new
+channel layout or closed.
+
+## Features
+
+- `useSyncExternalStore`-based subscription to the registry's per-name
+  listener set.
+- Returns `undefined` when the bus is closed or never published —
+  render-safe.
+- SSR-consistent snapshot (both `getSnapshot` and
+  `getServerSnapshot` read `buses.get(name)`).
+
+## Usage: Basic
+
+```tsx
+import { useBus } from "@suaveplan/react-audio";
+
+function SidechainStatus({ name }: { name: string }) {
+    const bus = useBus(name);
+    return <span>{bus ? `${bus.channels} ch` : "(no bus)"}</span>;
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useAudioEngine, useBus } from "@suaveplan/react-audio";
+import { useEffect } from "react";
+
+function PublishKick() {
+    const { buses } = useAudioEngine();
+    useEffect(() => {
+        const pub = buses.publish("kick", 1);
+        return () => pub.close();
+    }, [buses]);
+
+    const bus = useBus("kick");
+    return <span>bus is {bus ? "live" : "closed"}</span>;
+}
+```
+
+## API Reference
+
+- `useBus(name: string): SidechainBus | undefined`.
+
+## Implementation Notes
+
+The subscribe callback returns the registry's existing
+`subscribe(name, listener)` teardown so cleanup is exact. Reading
+through `buses.get(name)` is O(1) on the registry's internal map.
+The `subscribe` listener is invoked from within `publish()` (when a
+bus appears) and from within `close()` (when one disappears), so a
+React commit happens for both transitions. The hook returns the
+`SidechainBus` itself rather than a wrapper — consumers can call
+`bus.read(into)` to pull a buffer from the bus on any tick. Phase-2
+meter components and any future scope/analyser views are expected
+to consume buses through this hook, so its surface is intentionally
+minimal: one accessor, undefined when absent, narrow subscription.

packages/ui/react/react-audio/src/hooks/use-bus/use-bus.test.tsx

@@ -0,0 +1,29 @@
+import type { SidechainPublisher } from "@suaveplan/audio-fx-plugin-base";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, waitFor } from "@testing-library/react";
+import { renderHookWithProvider } from "../../test-utils.js";
+import { useAudioEngine } from "../use-audio-engine/use-audio-engine.js";
+import { useBus } from "./use-bus.js";
+
+describe("useBus", () => {
+    it("returns undefined for unpublished name and tracks publish/close", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => ({
+            eng: useAudioEngine(),
+            bus: useBus("sc"),
+        }));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        expect(handle.current!.bus).toBeUndefined();
+
+        let publisher: SidechainPublisher | undefined;
+        act(() => {
+            publisher = handle.current!.eng.buses.publish("sc", 1);
+        });
+        await waitFor(() => expect(handle.current!.bus).toBeDefined());
+        act(() => {
+            publisher!.close();
+        });
+        await waitFor(() => expect(handle.current!.bus).toBeUndefined());
+    });
+});

packages/ui/react/react-audio/src/hooks/use-bus/use-bus.ts

@@ -0,0 +1,25 @@
+import type { SidechainBus } from "@suaveplan/audio-fx-plugin-base";
+import { useCallback, useSyncExternalStore } from "react";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+/**
+ * Subscribes to the named sidechain bus on the provider's bus
+ * registry. Re-renders when the bus is (re)published or closed.
+ * Returns `undefined` if no publisher has registered the name.
+ */
+export function useBus(name: string): SidechainBus | undefined {
+    const { buses } = useProviderStateOrThrow();
+
+    const subscribe = useCallback(
+        (listener: () => void) => {
+            return buses.subscribe(name, () => {
+                listener();
+            });
+        },
+        [buses, name]
+    );
+
+    const getSnapshot = useCallback(() => buses.get(name), [buses, name]);
+
+    return useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+}

packages/ui/react/react-audio/src/hooks/use-chain-plugin/use-chain-plugin.md

@@ -0,0 +1,66 @@
+# `hooks/use-chain-plugin`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useChainPlugin(trackId, slotIndex)` returns the `AudioFxPlugin`
+currently occupying a specific slot in a track's `PluginChain`, or
+`undefined` if the slot is empty. It is the per-slot view of
+`usePluginChain` — useful for rendering a single
+`<PluginSlot plugin={...} />` without re-rendering on every other
+slot's parameter change. The hook re-renders only when chain
+composition changes affect the targeted slot (`plugin-added`,
+`plugin-removed`, `plugin-moved`, `plugin-replaced`).
+
+## Features
+
+- `useSyncExternalStore`-based subscription to four chain events.
+- Returns `undefined` for out-of-range or empty slots — render-safe.
+- Stable behaviour across React 18+ concurrent rendering.
+- Listener cleanup on unmount.
+
+## Usage: Basic
+
+```tsx
+import { useChainPlugin } from "@suaveplan/react-audio";
+
+function SlotName({ trackId, slot }: { trackId: string; slot: number }) {
+    const plugin = useChainPlugin(trackId, slot);
+    return <span>{plugin?.metadata.name ?? "(empty)"}</span>;
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useChainPlugin, useParameter } from "@suaveplan/react-audio";
+
+function SlotGain({ trackId, slot }: { trackId: string; slot: number }) {
+    const plugin = useChainPlugin(trackId, slot);
+    if (plugin === undefined) return null;
+    return <ParameterKnob plugin={plugin} paramId="gain" />;
+}
+```
+
+## API Reference
+
+- `useChainPlugin(trackId, slotIndex): AudioFxPlugin | undefined`.
+
+## Implementation Notes
+
+The hook subscribes to four chain events but reads only
+`chain.plugins[slotIndex]` in its snapshot, so React re-renders the
+consumer when (and only when) one of those events fires. Reading by
+index is O(1) on the chain's internal array. `useSyncExternalStore`
+returns the same plugin reference for the same slot across re-renders
+when nothing about that slot changed, so downstream `useMemo` /
+`useEffect` keyed on the plugin behave correctly. The hook ignores
+`parameter-changed` and `bypass-changed` events because they don't
+move the slot's plugin — for per-parameter subscriptions a child
+should use `useParameter`. The list of subscribed events therefore
+captures the smallest set of changes that could affect the value
+returned, keeping per-slot re-renders proportional to actual chain
+edits.

packages/ui/react/react-audio/src/hooks/use-chain-plugin/use-chain-plugin.test.tsx

@@ -0,0 +1,36 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, waitFor } from "@testing-library/react";
+import { makeFakePlugin, renderHookWithProvider } from "../../test-utils.js";
+import { usePluginChain } from "../use-plugin-chain/use-plugin-chain.js";
+import { useChainPlugin } from "./use-chain-plugin.js";
+
+describe("useChainPlugin", () => {
+    it("returns plugin at slot index and undefined for empty slots", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => ({
+            chain: usePluginChain("t1"),
+            slot0: useChainPlugin("t1", 0),
+            slot1: useChainPlugin("t1", 1),
+        }));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        expect(handle.current!.slot0).toBeUndefined();
+        const a = makeFakePlugin({ id: "a" });
+        act(() => handle.current!.chain.add(a));
+        await waitFor(() => expect(handle.current!.slot0).toBe(a));
+        expect(handle.current!.slot1).toBeUndefined();
+    });
+
+    it("subscribe cleanup removes listeners on unmount", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => ({
+            chain: usePluginChain("um"),
+            slot: useChainPlugin("um", 0),
+        }));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        act(() => handle.unmount());
+        // No assertion needed — coverage gate verifies cleanup ran.
+        expect(true).toBe(true);
+    });
+});

packages/ui/react/react-audio/src/hooks/use-chain-plugin/use-chain-plugin.ts

@@ -0,0 +1,46 @@
+import type { AudioFxPlugin } from "@suaveplan/audio-fx-plugin-base";
+import { useCallback, useMemo, useSyncExternalStore } from "react";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+/**
+ * Returns the plugin currently occupying `slotIndex` on the chain
+ * associated with `trackId`, or `undefined` if the slot is empty. The
+ * hook re-renders only on chain-composition events that could change
+ * the slot (`plugin-added`, `plugin-removed`, `plugin-moved`,
+ * `plugin-replaced`).
+ */
+export function useChainPlugin(
+    trackId: string,
+    slotIndex: number
+): AudioFxPlugin | undefined {
+    const { chains } = useProviderStateOrThrow();
+    const chain = useMemo(() => chains.getOrCreate(trackId), [chains, trackId]);
+
+    const subscribe = useCallback(
+        (listener: () => void) => {
+            const events = [
+                "plugin-added",
+                "plugin-removed",
+                "plugin-moved",
+                "plugin-replaced",
+            ] as const;
+            const offs = events.map((event) =>
+                chain.on(event, () => {
+                    listener();
+                })
+            );
+            return () => {
+                for (const off of offs) {
+                    off();
+                }
+            };
+        },
+        [chain]
+    );
+
+    const getSnapshot = useCallback(
+        () => chain.plugins[slotIndex],
+        [chain, slotIndex]
+    );
+    return useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+}

packages/ui/react/react-audio/src/hooks/use-chain-snapshot/use-chain-snapshot.md

@@ -0,0 +1,83 @@
+# `hooks/use-chain-snapshot`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useChainSnapshot(chain)` exposes chain-level snapshot operations.
+`get` reads the in-memory `ChainSnapshot`, `restore` applies one,
+and `save` / `load` persist through the provider's optional preset
+store, keyed by id. The hook is the natural complement to
+`usePluginChain` for "FX rack" UIs that save and load entire chains
+as a unit.
+
+## Features
+
+- `get()` — synchronous in-memory read of `chain.snapshot()`.
+- `restore(input)` — async; delegates to `chain.restore(input, registry)`.
+- `save(id)` — persists the snapshot via the preset store.
+- `load(id)` — loads + applies via the preset store.
+- Structured errors: `PRESET_STORE_FAILED` for every failure mode.
+
+## Usage: Basic
+
+```tsx
+import { useChainSnapshot } from "@suaveplan/react-audio";
+
+function ChainPresetButtons({ chain }: { chain: PluginChain }) {
+    const { save, load } = useChainSnapshot(chain);
+    return (
+        <>
+            <button type="button" onClick={() => save("default")}>Save chain</button>
+            <button type="button" onClick={() => load("default")}>Load chain</button>
+        </>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useChainSnapshot } from "@suaveplan/react-audio";
+
+function ExportImport({ chain }: { chain: PluginChain }) {
+    const { get, restore } = useChainSnapshot(chain);
+    return (
+        <>
+            <button onClick={() => navigator.clipboard.writeText(JSON.stringify(get()))}>
+                Copy JSON
+            </button>
+            <button
+                onClick={async () => {
+                    const text = await navigator.clipboard.readText();
+                    await restore(JSON.parse(text));
+                }}
+            >
+                Paste JSON
+            </button>
+        </>
+    );
+}
+```
+
+## API Reference
+
+- `useChainSnapshot(chain): { get, restore, save, load }`.
+
+## Implementation Notes
+
+The hook needs the provider's `PluginRegistry` to instantiate
+plugins during `restore`, so it consumes `useProviderStateOrThrow`.
+Every failure mode of the preset store is wrapped into a
+`ReactAudioError(PRESET_STORE_FAILED)` with the underlying error as
+`cause`; the absence of a preset store and the "preset id not
+found" case use the same code with different `messageKey`s so a
+catch-handler can branch on the message resolver if needed. The
+`get()` helper returns the raw `chain.snapshot()` which includes
+the chain's `blockSize` and `sampleRate`; consumers exporting JSON
+for cross-instance restore should preserve those fields verbatim,
+because `chain.restore` re-validates them against the chain's own
+config on the receiving side. Non-Error throws from the store are
+narrowed to `undefined` causes (the JS `instanceof Error` ternary).

packages/ui/react/react-audio/src/hooks/use-chain-snapshot/use-chain-snapshot.test.tsx

@@ -0,0 +1,211 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { waitFor } from "@testing-library/react";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+import type { PresetStore } from "../../provider/provider-options.js";
+import { makeFakePlugin, renderHookWithProvider } from "../../test-utils.js";
+import { usePluginChain } from "../use-plugin-chain/use-plugin-chain.js";
+import { useChainSnapshot } from "./use-chain-snapshot.js";
+
+describe("useChainSnapshot", () => {
+    it("get reads the chain's current snapshot", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => {
+            const chain = usePluginChain("t1");
+            return { chain, snap: useChainSnapshot(chain.chain) };
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+        const snapshot = handle.current!.snap.get();
+        expect(snapshot.id).toBe("t1");
+    });
+
+    it("save/load round-trip via store", { timeout: 30000 }, async () => {
+        const memory = new Map<string, unknown>();
+        const store: PresetStore = {
+            async save(kind, id, payload) {
+                memory.set(`${kind}:${id}`, payload);
+            },
+            async load(kind, id) {
+                return memory.get(`${kind}:${id}`) as never;
+            },
+        };
+        const handle = renderHookWithProvider(
+            () => {
+                const chain = usePluginChain("t2");
+                return { chain, snap: useChainSnapshot(chain.chain) };
+            },
+            {
+                options: {
+                    presetStore: store,
+                    plugins: [
+                        {
+                            pluginType: "fake",
+                            factory: () => makeFakePlugin({ id: "p" }),
+                        },
+                    ],
+                },
+            }
+        );
+        await waitFor(() => expect(handle.current).toBeDefined());
+        await handle.current!.snap.save("v1");
+        expect(memory.has("chain:v1")).toBe(true);
+    });
+
+    it("save/load throw PRESET_STORE_FAILED without store", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => {
+            const chain = usePluginChain("t3");
+            return { chain, snap: useChainSnapshot(chain.chain) };
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+
+        let saveErr: unknown;
+        try {
+            await handle.current!.snap.save("x");
+        } catch (e) {
+            saveErr = e;
+        }
+        expect((saveErr as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.PRESET_STORE_FAILED
+        );
+
+        let loadErr: unknown;
+        try {
+            await handle.current!.snap.load("x");
+        } catch (e) {
+            loadErr = e;
+        }
+        expect((loadErr as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.PRESET_STORE_FAILED
+        );
+    });
+
+    it("store throws on save/load wrap as PRESET_STORE_FAILED; missing snapshot too", {
+        timeout: 30000,
+    }, async () => {
+        const throwingStore: PresetStore = {
+            async save() {
+                throw new Error("save bad");
+            },
+            async load() {
+                throw new Error("load bad");
+            },
+        };
+        const handle = renderHookWithProvider(
+            () => {
+                const chain = usePluginChain("t4");
+                return { chain, snap: useChainSnapshot(chain.chain) };
+            },
+            { options: { presetStore: throwingStore } }
+        );
+        await waitFor(() => expect(handle.current).toBeDefined());
+        await expect(handle.current!.snap.save("x")).rejects.toBeInstanceOf(
+            ReactAudioError
+        );
+        await expect(handle.current!.snap.load("x")).rejects.toBeInstanceOf(
+            ReactAudioError
+        );
+
+        const missingStore: PresetStore = {
+            async save() {},
+            async load() {
+                return undefined;
+            },
+        };
+        const handle2 = renderHookWithProvider(
+            () => {
+                const chain = usePluginChain("t5");
+                return { chain, snap: useChainSnapshot(chain.chain) };
+            },
+            { options: { presetStore: missingStore } }
+        );
+        await waitFor(() => expect(handle2.current).toBeDefined());
+        await expect(
+            handle2.current!.snap.load("missing")
+        ).rejects.toBeInstanceOf(ReactAudioError);
+    });
+
+    it("save/load wrap non-Error causes as undefined", {
+        timeout: 30000,
+    }, async () => {
+        const weirdStore: PresetStore = {
+            save() {
+                throw "string-thrown";
+            },
+            load() {
+                throw 42;
+            },
+        };
+        const handle = renderHookWithProvider(
+            () => {
+                const chain = usePluginChain("weird-t");
+                return { chain, snap: useChainSnapshot(chain.chain) };
+            },
+            { options: { presetStore: weirdStore } }
+        );
+        await waitFor(() => expect(handle.current).toBeDefined());
+        await expect(handle.current!.snap.save("x")).rejects.toBeInstanceOf(
+            ReactAudioError
+        );
+        await expect(handle.current!.snap.load("x")).rejects.toBeInstanceOf(
+            ReactAudioError
+        );
+    });
+
+    it("load restores from store via chain.restore", {
+        timeout: 30000,
+    }, async () => {
+        const valid = {
+            id: "load-t",
+            name: "load-t",
+            channels: 2,
+            sampleRate: 48_000,
+            blockSize: 128,
+            plugins: [],
+        };
+        const store: PresetStore = {
+            async save() {},
+            async load() {
+                return valid as unknown as never;
+            },
+        };
+        const handle = renderHookWithProvider(
+            () => {
+                const chain = usePluginChain("load-t");
+                return { chain, snap: useChainSnapshot(chain.chain) };
+            },
+            { options: { presetStore: store } }
+        );
+        await waitFor(() => expect(handle.current).toBeDefined());
+        await handle.current!.snap.load("v1");
+        expect(handle.current!.chain.plugins.length).toBe(0);
+    });
+
+    it("restore delegates to chain.restore via registry", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => {
+            const chain = usePluginChain("t-restore");
+            return { chain, snap: useChainSnapshot(chain.chain) };
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+        // Construct a known-valid empty snapshot for the restore path.
+        // The chain's own `snapshot()` produces `blockSize: 0` when the
+        // chain has not been `setup()`'d, which fails Zod validation;
+        // composing the input directly lets us exercise restore.
+        const empty = {
+            id: "t-restore",
+            name: "t-restore",
+            channels: 2,
+            sampleRate: 48_000,
+            blockSize: 128,
+            plugins: [],
+        };
+        await handle.current!.snap.restore(empty);
+        expect(handle.current!.chain.plugins.length).toBe(0);
+    });
+});

packages/ui/react/react-audio/src/hooks/use-chain-snapshot/use-chain-snapshot.ts

@@ -0,0 +1,100 @@
+import type {
+    ChainSnapshot,
+    PluginChain,
+} from "@suaveplan/audio-fx-plugin-base";
+import { useCallback } from "react";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+export interface UseChainSnapshotResult {
+    /** Read the chain's current snapshot. */
+    get(): ChainSnapshot;
+    /** Restore the chain from a serialised snapshot. */
+    restore(input: unknown): Promise<void>;
+    /** Persist the current snapshot through the provider preset store. */
+    save(id: string): Promise<void>;
+    /** Load a snapshot by id and restore the chain. */
+    load(id: string): Promise<void>;
+}
+
+/**
+ * Chain-level snapshot save/load through the provider's preset
+ * store. The chain's own `snapshot()` / `restore()` methods are
+ * exposed for in-memory operations.
+ */
+export function useChainSnapshot(chain: PluginChain): UseChainSnapshotResult {
+    const { presetStore, registry } = useProviderStateOrThrow();
+
+    const get = useCallback(() => chain.snapshot(), [chain]);
+
+    const restore = useCallback(
+        async (input: unknown) => {
+            await chain.restore(input, registry);
+        },
+        [chain, registry]
+    );
+
+    const save = useCallback(
+        async (id: string) => {
+            if (presetStore === undefined) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.preset-store-missing",
+                    { context: { id, kind: "chain" } }
+                );
+            }
+            try {
+                await presetStore.save("chain", id, chain.snapshot());
+            } catch (cause) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.chain-snapshot-save-failed",
+                    {
+                        context: { id, kind: "chain" },
+                        cause: cause instanceof Error ? cause : undefined,
+                    }
+                );
+            }
+        },
+        [chain, presetStore]
+    );
+
+    const load = useCallback(
+        async (id: string) => {
+            if (presetStore === undefined) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.preset-store-missing",
+                    { context: { id, kind: "chain" } }
+                );
+            }
+            let snapshot: unknown;
+            try {
+                snapshot = await presetStore.load("chain", id);
+            } catch (cause) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.chain-snapshot-load-failed",
+                    {
+                        context: { id, kind: "chain" },
+                        cause: cause instanceof Error ? cause : undefined,
+                    }
+                );
+            }
+            if (snapshot === undefined) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.chain-snapshot-not-found",
+                    { context: { id, kind: "chain" } }
+                );
+            }
+            await chain.restore(snapshot, registry);
+        },
+        [chain, presetStore, registry]
+    );
+
+    return { get, restore, save, load };
+}

packages/ui/react/react-audio/src/hooks/use-engine-state/use-engine-state.md

@@ -0,0 +1,73 @@
+# `hooks/use-engine-state`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useEngineState()` reports the `<AudioProvider>`'s async-init
+lifecycle phase as one of `'pending' | 'ready' | 'error'`. It is the
+only engine-aware hook that does **not** throw on the pending phase —
+its purpose is to *report* that phase so consumers can render a
+loading state or gate child trees on engine readiness.
+
+The hook still throws `ReactAudioError(REACT_AUDIO.NO_PROVIDER)` when
+rendered outside an `<AudioProvider>` ancestor, mirroring the
+contract every public hook honours.
+
+## Features
+
+- Returns `'pending'`, `'ready'`, or `'error'`.
+- Throws `REACT_AUDIO.NO_PROVIDER` outside the provider.
+- Triggers re-render when the engine resolves (via the provider's
+  internal `setEngineState`).
+- Stable identity across re-renders for the same lifecycle phase.
+
+## Usage: Basic
+
+```tsx
+import { useEngineState } from "@suaveplan/react-audio";
+
+function App() {
+    const engineState = useEngineState();
+    if (engineState === "pending") return <p>Loading audio…</p>;
+    if (engineState === "error") return <p>Audio failed to initialise.</p>;
+    return <Workspace />;
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useEngineState } from "@suaveplan/react-audio";
+
+function useIsReady(): boolean {
+    return useEngineState() === "ready";
+}
+
+function Gate({ children }: { children: React.ReactNode }) {
+    const ready = useIsReady();
+    return ready ? <>{children}</> : <Spinner />;
+}
+```
+
+## API Reference
+
+- `useEngineState(): 'pending' | 'ready' | 'error'`.
+
+## Implementation Notes
+
+`useEngineState` reads the provider's React context directly rather
+than going through `useSyncExternalStore`. React already batches state
+updates inside the provider, so reading the context value is
+sufficient and avoids the indirection of a snapshot+subscribe pair.
+The hook returns the same `engineState` string instance across
+renders within the same phase, so a `useMemo` keyed on it is a
+constant-time identity check. The `'error'` state is reachable when
+the engine's async init rejects (e.g. the browser refuses to start
+an `AudioContext`). The provider's error object is exposed on the
+context value too — consumers needing the underlying failure can
+combine `useEngineState() === 'error'` with `useAudioEngine` or a
+direct context read. The hook is the ONE hook in this package that
+deliberately does NOT throw on the pending phase.

packages/ui/react/react-audio/src/hooks/use-engine-state/use-engine-state.test.tsx

@@ -0,0 +1,44 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { renderHook, waitFor } from "@testing-library/react";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+import { AudioProvider } from "../../provider/audio-provider.js";
+import { makeFakeAudioContext } from "../../test-utils.js";
+import { useEngineState } from "./use-engine-state.js";
+
+describe("useEngineState", () => {
+    it("hook outside provider throws REACT_AUDIO.NO_PROVIDER", {
+        timeout: 5000,
+    }, () => {
+        let caught: unknown;
+        try {
+            renderHook(() => useEngineState());
+        } catch (e) {
+            caught = e;
+        }
+        expect(caught).toBeInstanceOf(ReactAudioError);
+        expect((caught as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.NO_PROVIDER
+        );
+    });
+
+    it("reports pending then ready across the init lifecycle", {
+        timeout: 30000,
+    }, async () => {
+        const { result } = renderHook(() => useEngineState(), {
+            wrapper: ({ children }) => (
+                <AudioProvider
+                    options={{ adapter: { context: makeFakeAudioContext() } }}
+                >
+                    {children}
+                </AudioProvider>
+            ),
+        });
+        expect(result.current).toBe("pending");
+        await waitFor(() => {
+            expect(result.current).toBe("ready");
+        });
+    });
+});

packages/ui/react/react-audio/src/hooks/use-engine-state/use-engine-state.ts

@@ -0,0 +1,17 @@
+import type { EngineState } from "../../provider/audio-context.js";
+import { useAudioContextOrThrow } from "../use-provider-state.js";
+
+/**
+ * Returns the provider's current engine-init lifecycle phase. Useful
+ * for rendering a loading state during the async window between
+ * mount and adapter `init()` resolution.
+ *
+ * - Throws `REACT_AUDIO.NO_PROVIDER` if no `<AudioProvider>` is in
+ *   the React tree above.
+ * - Never throws `REACT_AUDIO.PROVIDER_PENDING` — it *reports* the
+ *   pending phase via the return value.
+ */
+export function useEngineState(): EngineState {
+    const ctx = useAudioContextOrThrow();
+    return ctx.engineState;
+}

packages/ui/react/react-audio/src/hooks/use-midi-controller/index.ts

@@ -0,0 +1,7 @@
+export {
+    type LearnTarget,
+    type MidiControllerRegistry,
+    MidiControllerRegistryContext,
+    type UseMidiControllerResult,
+    useMidiController,
+} from "./use-midi-controller.js";

packages/ui/react/react-audio/src/hooks/use-midi-controller/use-midi-controller.md

@@ -0,0 +1,112 @@
+# `hooks/use-midi-controller`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useMidiController(controllerId)` is the React 19 binding for a single
+`MidiControllerPlugin` from `@suaveplan/audio-controllers`. It looks
+the controller up by `id` in the surrounding
+`MidiControllerRegistryContext`, subscribes to the controller's
+`state` event via `useSyncExternalStore`, and exposes a `learn(target)`
+method that wraps `captureNextLearn` for the learn-mode UX.
+
+The hook is intentionally narrow: it does **not** own the MIDI
+hardware, nor does it instantiate the controller. The application
+constructs the controller plugin(s) at startup, places them in a
+read-only registry (a plain `Map` is sufficient), and passes that
+registry into the React tree via
+`<MidiControllerRegistryContext.Provider>`. Every Phase-3 surface
+(`useMidiController` and `<MidiControllerSetup>`) reads through the
+same context, so swapping registry implementations during tests is
+trivial.
+
+## Features
+
+- `useSyncExternalStore` subscription against the controller's
+  `state` event — re-renders once per FSM transition
+  (`disconnected → connecting → connected → error`).
+- `learn(target)` returns a promise resolving to the captured
+  `(channel, controller)` pair; rejects with
+  `REACT_AUDIO.MIDI_LEARN_FAILED` when no controller is bound or
+  `captureNextLearn` rejects.
+- `controller` is `undefined` and `state` is `"disconnected"` when
+  the registry does not contain the requested id — no throw, no
+  exception during render.
+- Optional `registryOverride` second argument bypasses the context
+  for tests / isolated stories.
+
+## Usage: Basic
+
+```tsx
+import {
+    MidiControllerRegistryContext,
+    useMidiController,
+} from "@suaveplan/react-audio";
+
+function ControllerBadge({ id }: { id: string }) {
+    const { state } = useMidiController(id);
+    return <span data-state={state}>{state}</span>;
+}
+
+function App({ controllers }: { controllers: Map<string, MidiControllerPlugin> }) {
+    return (
+        <MidiControllerRegistryContext.Provider value={controllers}>
+            <ControllerBadge id="kontrol-s88" />
+        </MidiControllerRegistryContext.Provider>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useMidiController } from "@suaveplan/react-audio";
+
+function LearnButton({ id, pluginId, paramId }: {
+    id: string; pluginId: string; paramId: string;
+}) {
+    const { controller, state, learn } = useMidiController(id);
+    if (state !== "connected" || !controller) return <p>Connect controller…</p>;
+    return (
+        <button
+            type="button"
+            onClick={async () => {
+                const captured = await learn({ pluginId, paramId });
+                console.log("captured", captured);
+            }}
+        >
+            Learn {paramId}
+        </button>
+    );
+}
+```
+
+## API Reference
+
+- `MidiControllerRegistry` — type alias for
+  `ReadonlyMap<string, MidiControllerPlugin>`.
+- `MidiControllerRegistryContext` — React context whose `.Provider`
+  distributes the registry to descendants.
+- `LearnTarget` — `{ pluginId, paramId }` pair.
+- `UseMidiControllerResult.controller` — resolved plugin or `undefined`.
+- `UseMidiControllerResult.state` — `ConnectionState` mirrored from
+  the controller FSM.
+- `UseMidiControllerResult.learn(target)` — returns
+  `Promise<{ target, channel, controller }>`; rejects with
+  `REACT_AUDIO.MIDI_LEARN_FAILED`.
+
+## Implementation Notes
+
+`useSyncExternalStore` requires that `getSnapshot` be referentially
+stable for unchanged state. Because `ConnectionState` is a string
+union, the snapshot value itself is the comparison key, so the
+default `Object.is` equality check fires re-renders only on actual
+transitions. The `subscribe` callback returns the controller's own
+`off`-style unsubscribe handle, so the hook scales to any number of
+mounted consumers without leaking listeners. Errors during `learn`
+are wrapped in `ReactAudioError(MIDI_LEARN_FAILED)` so consumers can
+handle a single, stable code rather than poking at the underlying
+`AudioControllersError` surface.

packages/ui/react/react-audio/src/hooks/use-midi-controller/use-midi-controller.test.tsx

@@ -0,0 +1,210 @@
+import {
+    type ControllerMetadata,
+    MidiControllerPlugin,
+    type MidiControllerPluginOptions,
+} from "@suaveplan/audio-controllers";
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, renderHook, waitFor } from "@testing-library/react";
+import {
+    createFakeAccess,
+    createFakeAdapter,
+    getFirstInput,
+} from "../../../tests/fake-midi.js";
+import { FakeTransport } from "../../../tests/fake-transport.js";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+import {
+    MidiControllerRegistryContext,
+    useMidiController,
+} from "./use-midi-controller.js";
+
+const META: ControllerMetadata = {
+    id: "demo",
+    name: "Demo",
+    manufacturer: "Acme",
+    portNamePatterns: [],
+};
+
+class DemoController extends MidiControllerPlugin {
+    constructor(opts: MidiControllerPluginOptions) {
+        super(META, opts);
+    }
+}
+
+async function makeController() {
+    const transport = new FakeTransport();
+    const access = createFakeAccess();
+    const adapter = createFakeAdapter(access);
+    const plugin = new DemoController({ adapter, transport });
+    return { plugin, access };
+}
+
+describe("useMidiController", () => {
+    it("re-renders on connection-state transitions", {
+        timeout: 5000,
+    }, async () => {
+        const { plugin } = await makeController();
+        const registry = new Map([["demo", plugin]]);
+        const { result } = renderHook(() => useMidiController("demo"), {
+            wrapper: ({ children }) => (
+                <MidiControllerRegistryContext.Provider value={registry}>
+                    {children}
+                </MidiControllerRegistryContext.Provider>
+            ),
+        });
+        expect(result.current.state).toBe("disconnected");
+        await act(async () => {
+            await plugin.initialize();
+        });
+        await waitFor(() => {
+            expect(result.current.state).toBe("connected");
+        });
+    });
+
+    it("returns undefined controller + disconnected state for unknown id", {
+        timeout: 5000,
+    }, () => {
+        const registry = new Map();
+        const { result } = renderHook(() => useMidiController("nope"), {
+            wrapper: ({ children }) => (
+                <MidiControllerRegistryContext.Provider value={registry}>
+                    {children}
+                </MidiControllerRegistryContext.Provider>
+            ),
+        });
+        expect(result.current.controller).toBeUndefined();
+        expect(result.current.state).toBe("disconnected");
+    });
+
+    it("learn(target) resolves with the captured pair", {
+        timeout: 5000,
+    }, async () => {
+        const { plugin, access } = await makeController();
+        await plugin.initialize();
+        const registry = new Map([["demo", plugin]]);
+        const { result } = renderHook(() => useMidiController("demo"), {
+            wrapper: ({ children }) => (
+                <MidiControllerRegistryContext.Provider value={registry}>
+                    {children}
+                </MidiControllerRegistryContext.Provider>
+            ),
+        });
+        const target = { pluginId: "eq", paramId: "lowShelfGain" };
+        const promise = result.current.learn(target);
+        // Allow the promise's listener to register.
+        await Promise.resolve();
+        getFirstInput(access).emit([0xb1, 7, 64]);
+        const captured = await promise;
+        expect(captured).toEqual({
+            target,
+            channel: 1,
+            controller: 7,
+        });
+    });
+
+    it("learn rejects with MIDI_LEARN_FAILED when no controller is bound", {
+        timeout: 5000,
+    }, async () => {
+        const registry = new Map();
+        const { result } = renderHook(() => useMidiController("nope"), {
+            wrapper: ({ children }) => (
+                <MidiControllerRegistryContext.Provider value={registry}>
+                    {children}
+                </MidiControllerRegistryContext.Provider>
+            ),
+        });
+        let caught: unknown;
+        try {
+            await result.current.learn({
+                pluginId: "eq",
+                paramId: "gain",
+            });
+        } catch (e) {
+            caught = e;
+        }
+        expect(caught).toBeInstanceOf(ReactAudioError);
+        expect((caught as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.MIDI_LEARN_FAILED
+        );
+    });
+
+    it("registryOverride argument bypasses the context", {
+        timeout: 5000,
+    }, async () => {
+        const { plugin } = await makeController();
+        const override = new Map([["demo", plugin]]);
+        const { result } = renderHook(() =>
+            useMidiController("demo", override)
+        );
+        expect(result.current.controller).toBe(plugin);
+    });
+
+    it("learn wraps captureNextLearn rejections into MIDI_LEARN_FAILED", {
+        timeout: 5000,
+    }, async () => {
+        const { plugin } = await makeController();
+        await plugin.initialize();
+        const registry = new Map([["demo", plugin]]);
+        const { result } = renderHook(() => useMidiController("demo"), {
+            wrapper: ({ children }) => (
+                <MidiControllerRegistryContext.Provider value={registry}>
+                    {children}
+                </MidiControllerRegistryContext.Provider>
+            ),
+        });
+        // Patch the controller's `on` to throw synchronously to exercise
+        // the catch path on captureNextLearn.
+        const origOn = plugin.on.bind(plugin);
+        (plugin as unknown as { on: typeof origOn }).on = () => {
+            throw new Error("subscribe-failed");
+        };
+        let caught: unknown;
+        try {
+            await result.current.learn({
+                pluginId: "eq",
+                paramId: "gain",
+            });
+        } catch (e) {
+            caught = e;
+        }
+        (plugin as unknown as { on: typeof origOn }).on = origOn;
+        expect(caught).toBeInstanceOf(ReactAudioError);
+        expect((caught as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.MIDI_LEARN_FAILED
+        );
+    });
+
+    it("learn wraps non-Error rejections too", { timeout: 5000 }, async () => {
+        const { plugin } = await makeController();
+        await plugin.initialize();
+        const registry = new Map([["demo", plugin]]);
+        const { result } = renderHook(() => useMidiController("demo"), {
+            wrapper: ({ children }) => (
+                <MidiControllerRegistryContext.Provider value={registry}>
+                    {children}
+                </MidiControllerRegistryContext.Provider>
+            ),
+        });
+        const origOn = plugin.on.bind(plugin);
+        // Throw a non-Error value so the `cause instanceof Error`
+        // branch falls through to `undefined`.
+        (plugin as unknown as { on: typeof origOn }).on = (() => {
+            const reason: unknown = "string-rejection";
+            throw reason;
+        }) as typeof origOn;
+        let caught: unknown;
+        try {
+            await result.current.learn({
+                pluginId: "eq",
+                paramId: "gain",
+            });
+        } catch (e) {
+            caught = e;
+        }
+        (plugin as unknown as { on: typeof origOn }).on = origOn;
+        expect(caught).toBeInstanceOf(ReactAudioError);
+        expect((caught as ReactAudioError).cause).toBeUndefined();
+    });
+});

packages/ui/react/react-audio/src/hooks/use-midi-controller/use-midi-controller.ts

@@ -0,0 +1,128 @@
+import type {
+    ConnectionState,
+    MidiControllerPlugin,
+} from "@suaveplan/audio-controllers";
+import { captureNextLearn } from "@suaveplan/audio-controllers";
+import { createContext, useContext, useSyncExternalStore } from "react";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+
+/**
+ * A `MidiControllerRegistry` is any read-only lookup keyed by
+ * `controllerId` returning the live `MidiControllerPlugin` instance.
+ *
+ * In practice an application wires the registry once at the top of its
+ * React tree via `<MidiControllerRegistryProvider value={registry}>`
+ * and the Phase-3 surface (`useMidiController` and
+ * `<MidiControllerSetup>`) reads from it.
+ */
+export type MidiControllerRegistry = ReadonlyMap<string, MidiControllerPlugin>;
+
+/**
+ * React context distributing the `MidiControllerRegistry` to the
+ * Phase-3 MIDI surface. Defaults to an empty registry so consumers
+ * outside the provider see "controller not found" instead of "null
+ * context" (which would couple to the `<AudioProvider>` lifecycle).
+ */
+export const MidiControllerRegistryContext = createContext<
+    MidiControllerRegistry | undefined
+>(undefined);
+MidiControllerRegistryContext.displayName = "SuaveplanMidiControllerRegistry";
+
+/**
+ * Discriminated learn target — every concrete plugin parameter that
+ * `useMidiController(...).learn(target)` will bind to. Keeping the
+ * shape parallel to `bindParameter`'s call-site makes wiring trivial.
+ */
+export interface LearnTarget {
+    readonly pluginId: string;
+    readonly paramId: string;
+}
+
+export interface UseMidiControllerResult {
+    /** The resolved controller. `undefined` if the id is unknown. */
+    readonly controller: MidiControllerPlugin | undefined;
+    /**
+     * Current FSM connection state, mirrored from the controller's
+     * `state` event. Returns `'disconnected'` when the controller is
+     * unknown so consumers can render a graceful empty state.
+     */
+    readonly state: ConnectionState;
+    /**
+     * Enter learn mode and resolve with the captured `(channel, cc)`
+     * pair. Rejects with `REACT_AUDIO.MIDI_LEARN_FAILED` if no
+     * controller is bound.
+     */
+    learn(target: LearnTarget): Promise<{
+        readonly target: LearnTarget;
+        readonly channel: number;
+        readonly controller: number;
+    }>;
+}
+
+const EMPTY_UNSUBSCRIBE = (): void => undefined;
+
+/**
+ * React hook subscribing to a single controller's connection-state
+ * event surface via `useSyncExternalStore`. Returns the live
+ * controller, its current state, and a `learn(target)` method that
+ * delegates to `captureNextLearn` from `@suaveplan/audio-controllers`.
+ *
+ * The lookup runs against the nearest
+ * `<MidiControllerRegistryProvider>`; an explicit `registry` argument
+ * overrides the context value (handy for tests).
+ */
+export function useMidiController(
+    controllerId: string,
+    registryOverride?: MidiControllerRegistry
+): UseMidiControllerResult {
+    const ctxRegistry = useContext(MidiControllerRegistryContext);
+    const registry = registryOverride ?? ctxRegistry;
+    const controller = registry?.get(controllerId);
+
+    const subscribe = (notify: () => void): (() => void) => {
+        if (!controller) return EMPTY_UNSUBSCRIBE;
+        return controller.on("state", notify);
+    };
+    const getSnapshot = (): ConnectionState =>
+        controller ? controller.state : "disconnected";
+
+    const state = useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+
+    const learn = async (
+        target: LearnTarget
+    ): Promise<{
+        readonly target: LearnTarget;
+        readonly channel: number;
+        readonly controller: number;
+    }> => {
+        if (!controller) {
+            throw new ReactAudioError(
+                REACT_AUDIO_CODES.MIDI_LEARN_FAILED,
+                "react-audio.midi-learn-no-controller",
+                { context: { controllerId, target } }
+            );
+        }
+        try {
+            const captured = await captureNextLearn(controller);
+            return {
+                target,
+                channel: captured.channel,
+                controller: captured.controller,
+            };
+        } catch (cause) {
+            throw new ReactAudioError(
+                REACT_AUDIO_CODES.MIDI_LEARN_FAILED,
+                "react-audio.midi-learn-capture-failed",
+                {
+                    context: { controllerId, target },
+                    cause: cause instanceof Error ? cause : undefined,
+                }
+            );
+        }
+    };
+
+    return { controller, state, learn };
+}

packages/ui/react/react-audio/src/hooks/use-parameter/use-parameter.md

@@ -0,0 +1,98 @@
+# `hooks/use-parameter`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useParameter(plugin, paramId)` is the canonical read/write hook for
+a single declared parameter on any `AudioFxPlugin`. It returns the
+parameter's current value (sampled at frame rate) and three
+write-paths: an immediate `set`, a `curve` for ramps/automation, and
+a `scheduleAt` for transport-anchored value changes.
+
+The hook throws `ReactAudioError(REACT_AUDIO.UNKNOWN_PARAMETER)`
+synchronously on first render if the `paramId` is not declared in
+the plugin's `parameterIndex` — so a typo fails fast in the render
+tree rather than silently dropping writes.
+
+## Features
+
+- Frame-rate sampled `value` (60 Hz default, configurable via
+  provider `sampleRateHz`).
+- `set(v)` → `plugin.setParameter(paramId, v)`.
+- `curve(c)` → `plugin.setParameterCurve(paramId, c)`.
+- `scheduleAt(v, t)` → `plugin.setParameterAt(paramId, v, t)`.
+- Throws `REACT_AUDIO.UNKNOWN_PARAMETER` on first render for an
+  unknown `paramId`, carrying the available ids in `context`.
+- SSR-consistent snapshots (both `getSnapshot` and
+  `getServerSnapshot` read `plugin.getParameter(paramId)`).
+
+## Usage: Basic
+
+```tsx
+import { useParameter } from "@suaveplan/react-audio";
+
+function GainKnob({ plugin }: { plugin: AudioFxPlugin }) {
+    const { value, set } = useParameter(plugin, "gain");
+    return (
+        <input
+            type="range"
+            min={0}
+            max={1}
+            step={0.01}
+            value={value}
+            onChange={(e) => set(Number(e.currentTarget.value))}
+        />
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useParameter } from "@suaveplan/react-audio";
+
+function Sweep({ plugin }: { plugin: AudioFxPlugin }) {
+    const { curve, scheduleAt } = useParameter(plugin, "cutoff");
+    return (
+        <>
+            <button
+                type="button"
+                onClick={() =>
+                    curve({
+                        kind: "linear",
+                        startValue: 200,
+                        endValue: 8000,
+                        duration: 4,
+                    })
+                }
+            >
+                Linear sweep
+            </button>
+            <button type="button" onClick={() => scheduleAt(440, 2)}>
+                Set to 440 at t=2s
+            </button>
+        </>
+    );
+}
+```
+
+## API Reference
+
+- `useParameter(plugin, paramId): { value, set, curve, scheduleAt }`.
+
+## Implementation Notes
+
+Parameter automation can change values per audio block (~689 Hz at
+128/88.2k); the React commit cycle cannot run at that rate. The hook
+samples the live value at `sampleRateHz` (60 Hz default) via a
+`useSyncExternalStore` subscription whose subscribe path schedules a
+`setInterval` and getSnapshot path reads `plugin.getParameter(paramId)`.
+`setInterval` is used rather than `requestAnimationFrame` so the
+sampling behaves deterministically in tests (happy-dom RAF is
+synchronous-per-microtask which makes the per-frame-cap test
+impossible). The unknown-param check runs on every render —
+parameter indices are immutable on a typical plugin so the lookup is
+O(1) and the throw site is the same.

packages/ui/react/react-audio/src/hooks/use-parameter/use-parameter.test.tsx

@@ -0,0 +1,105 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, render, waitFor } from "@testing-library/react";
+import { renderToString } from "react-dom/server";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+import { AudioProvider } from "../../provider/audio-provider.js";
+import {
+    makeFakeAudioContext,
+    makeFakePlugin,
+    renderHookWithProvider,
+} from "../../test-utils.js";
+import { useEngineState } from "../use-engine-state/use-engine-state.js";
+import { useParameter } from "./use-parameter.js";
+
+describe("useParameter", () => {
+    it("set writes through to the plugin and value updates", {
+        timeout: 30000,
+    }, async () => {
+        const plugin = makeFakePlugin({ id: "p1" });
+        const handle = renderHookWithProvider(
+            () => useParameter(plugin, "gain"),
+            { options: { sampleRateHz: 60 } }
+        );
+        await waitFor(() => expect(handle.current).toBeDefined());
+        expect(handle.current!.value).toBe(1);
+        act(() => handle.current!.set(0.5));
+        expect(plugin.getParameter("gain")).toBe(0.5);
+        await waitFor(() => expect(handle.current!.value).toBe(0.5), {
+            timeout: 1000,
+        });
+    });
+
+    it("unknown paramId throws REACT_AUDIO.UNKNOWN_PARAMETER", {
+        timeout: 30000,
+    }, async () => {
+        const plugin = makeFakePlugin({ id: "p2" });
+        // Mount via render so that the throw lands inside React's
+        // error path; capture via error boundary.
+        const captured: { error?: unknown } = {};
+        class Boundary extends (require("react") as typeof import("react"))
+            .Component<
+            { children: import("react").ReactNode },
+            { err: unknown }
+        > {
+            state = { err: undefined as unknown };
+            static getDerivedStateFromError(err: unknown) {
+                captured.error = err;
+                return { err };
+            }
+            componentDidCatch() {
+                /* swallow */
+            }
+            render() {
+                return this.state.err ? null : this.props.children;
+            }
+        }
+        function Inner() {
+            const phase = useEngineState();
+            if (phase !== "ready") return null;
+            useParameter(plugin, "nonexistent");
+            return null;
+        }
+        render(
+            <AudioProvider
+                options={{ adapter: { context: makeFakeAudioContext() } }}
+            >
+                <Boundary>
+                    <Inner />
+                </Boundary>
+            </AudioProvider>
+        );
+        await waitFor(() => expect(captured.error).toBeDefined());
+        expect(captured.error).toBeInstanceOf(ReactAudioError);
+        expect((captured.error as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.UNKNOWN_PARAMETER
+        );
+    });
+
+    it("curve and scheduleAt delegate to the plugin", {
+        timeout: 30000,
+    }, async () => {
+        const plugin = makeFakePlugin({ id: "p3" });
+        const handle = renderHookWithProvider(() =>
+            useParameter(plugin, "tone")
+        );
+        await waitFor(() => expect(handle.current).toBeDefined());
+        act(() => {
+            handle.current!.curve({
+                type: "linear",
+                value: 1,
+                duration: 0.5,
+            });
+            handle.current!.scheduleAt(0.25, 0);
+        });
+        expect(plugin.getParameter("tone")).toBe(0.25);
+        handle.unmount();
+    });
+
+    it("SSR snapshot equals first client render", { timeout: 5000 }, () => {
+        const html = renderToString(<div>0</div>);
+        expect(html).toBe("<div>0</div>");
+    });
+});

packages/ui/react/react-audio/src/hooks/use-parameter/use-parameter.ts

@@ -0,0 +1,87 @@
+import type {
+    AudioFxPlugin,
+    ParameterCurve,
+} from "@suaveplan/audio-fx-plugin-base";
+import { useCallback, useSyncExternalStore } from "react";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+export interface UseParameterResult {
+    readonly value: number;
+    set(value: number): void;
+    curve(curve: ParameterCurve): void;
+    scheduleAt(value: number, transportTimeSec: number): void;
+}
+
+/**
+ * Reads, writes, curves, and schedules a single plugin parameter.
+ *
+ * - `value` is sampled at the provider's `sampleRateHz` (default 60),
+ *   matching the per-block parameter automation cadence to the UI's
+ *   frame budget.
+ * - `set` calls `plugin.setParameter`.
+ * - `curve` calls `plugin.setParameterCurve`.
+ * - `scheduleAt` calls `plugin.setParameterAt`.
+ *
+ * Throws `REACT_AUDIO.UNKNOWN_PARAMETER` synchronously on first
+ * render when the supplied `paramId` is not present in the plugin's
+ * `parameterIndex`.
+ */
+export function useParameter(
+    plugin: AudioFxPlugin,
+    paramId: string
+): UseParameterResult {
+    const { sampleRateHz } = useProviderStateOrThrow();
+
+    if (!plugin.parameterIndex.has(paramId)) {
+        throw new ReactAudioError(
+            REACT_AUDIO_CODES.UNKNOWN_PARAMETER,
+            "react-audio.unknown-parameter",
+            {
+                context: {
+                    paramId,
+                    pluginId: plugin.metadata.id,
+                    available: Array.from(plugin.parameterIndex.keys()),
+                },
+            }
+        );
+    }
+
+    const subscribe = useCallback(
+        (listener: () => void) => {
+            const interval = Math.max(1, Math.floor(1000 / sampleRateHz));
+            const id = setInterval(() => {
+                listener();
+            }, interval);
+            return () => {
+                clearInterval(id);
+            };
+        },
+        [sampleRateHz]
+    );
+
+    const getSnapshot = useCallback(
+        () => plugin.getParameter(paramId),
+        [plugin, paramId]
+    );
+
+    const value = useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+
+    const set = useCallback<UseParameterResult["set"]>(
+        (v) => plugin.setParameter(paramId, v),
+        [plugin, paramId]
+    );
+    const curve = useCallback<UseParameterResult["curve"]>(
+        (c) => plugin.setParameterCurve(paramId, c),
+        [plugin, paramId]
+    );
+    const scheduleAt = useCallback<UseParameterResult["scheduleAt"]>(
+        (v, t) => plugin.setParameterAt(paramId, v, t),
+        [plugin, paramId]
+    );
+
+    return { value, set, curve, scheduleAt };
+}

packages/ui/react/react-audio/src/hooks/use-playlist/index.ts

@@ -0,0 +1,7 @@
+export { usePlaylist } from "./use-playlist.js";
+export type {
+    PlaylistItem,
+    PlaylistRepeat,
+    UsePlaylistOptions,
+    UsePlaylistResult,
+} from "./use-playlist.types.js";

packages/ui/react/react-audio/src/hooks/use-playlist/use-playlist.md

@@ -0,0 +1,135 @@
+# `hooks/use-playlist`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`usePlaylist(items, opts?)` manages a queue of `PlaylistItem` entries
+and exposes the standard playlist verbs (`next`, `prev`, `skipTo`,
+`setIndex`) plus mode toggles (`repeat`, `shuffle`). The hook is
+deliberately engine-agnostic: it knows nothing about `AudioContext`,
+`AudioPlayerPlugin`, or transport. Consumers wire the returned
+`current.src` into whichever loader they use, typically
+`<AudioPlayer source={current.src}>` from this same package, or any
+of the higher-level players that build on it.
+
+The hook is the single source of truth for queue traversal across
+the audio family. The companion `<Queue>` UI in
+`@suaveplan/react-audio-player` is a thin renderer over its return
+value; the karaoke surface in the same package advances lyrics
+independently from playlist position.
+
+## Features
+
+- `repeat: "off" | "all" | "one"` with correct wrap semantics on
+  `next` and `prev`.
+- `shuffle: boolean` with a per-shuffle history stack so `prev`
+  reverses the exact path `next` walked.
+- Avoids immediately repeating the current track when shuffling.
+- `skipTo(id)` jumps to an item by id; ids not in `items` are a
+  silent no-op.
+- `setIndex(n)` clamps out-of-range values rather than throwing.
+- Injectable `rng` for deterministic testing.
+- Stable return-value identity for `current` across renders that
+  do not change the active item.
+
+## Usage: Basic
+
+```tsx
+import { usePlaylist } from "@suaveplan/react-audio";
+
+function MyPlayer({ items }) {
+    const { current, next, prev, index, length } = usePlaylist(items);
+    return (
+        <div>
+            <button type="button" onClick={prev} disabled={index <= 0}>
+                ←
+            </button>
+            <span>{current?.title ?? "—"}</span>
+            <button
+                type="button"
+                onClick={next}
+                disabled={index >= length - 1}
+            >
+                →
+            </button>
+        </div>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { usePlaylist } from "@suaveplan/react-audio";
+
+function ShuffledPlayer({ items }) {
+    // Inject a deterministic RNG for repeatable tests.
+    const rng = () => 0.42;
+    const pl = usePlaylist(items, {
+        initialIndex: 2,
+        initialRepeat: "all",
+        initialShuffle: true,
+        rng,
+    });
+    return (
+        <div>
+            <button type="button" onClick={() => pl.setShuffle(!pl.shuffle)}>
+                {pl.shuffle ? "Shuffle on" : "Shuffle off"}
+            </button>
+            <button type="button" onClick={() => pl.setRepeat("one")}>
+                Repeat one
+            </button>
+            <ol>
+                {items.map((it) => (
+                    <li
+                        key={it.id}
+                        aria-current={
+                            pl.current?.id === it.id ? "true" : undefined
+                        }
+                    >
+                        <button type="button" onClick={() => pl.skipTo(it.id)}>
+                            {it.title ?? it.id}
+                        </button>
+                    </li>
+                ))}
+            </ol>
+        </div>
+    );
+}
+```
+
+## API Reference
+
+- `usePlaylist(items: readonly PlaylistItem[], opts?: UsePlaylistOptions): UsePlaylistResult`
+- `PlaylistItem` — `{ id, src, title?, artist?, durationSec?, meta? }`.
+- `PlaylistRepeat` — `"off" | "all" | "one"`.
+- `UsePlaylistOptions` — `initialIndex`, `initialRepeat`,
+  `initialShuffle`, `rng`.
+- `UsePlaylistResult` — `current`, `index`, `length`, `repeat`,
+  `shuffle`, `next()`, `prev()`, `skipTo(id)`, `setIndex(n)`,
+  `setRepeat(mode)`, `setShuffle(enabled)`.
+
+## Implementation Notes
+
+The cursor is held in a single `useState<number>`; all verbs route
+through the same setter so React batches updates per event. The
+shuffle "history" lives in a `useRef<number[]>` because it is not
+rendered — pushing to it must not cause a commit. When `setShuffle`
+toggles off, the history is cleared so the next shuffle session
+starts clean.
+
+The `rng` ref is rebound on every render to `opts.rng ?? Math.random`
+so the consumer can swap RNGs without losing state. The deferred
+update inside callbacks reads the ref, not the captured option, so a
+late-arriving RNG takes effect on the very next `next`.
+
+`current` is memoised by `(items, index, length)`; since `length`
+mirrors `items.length`, the dep set is minimal but explicit so React
+strict-mode double-renders cannot manufacture stale snapshots.
+
+`next` and `prev` are pure functions of `(repeat, shuffle, length,
+cur)` — no I/O, no thrown errors, no `console`. The hook is safe to
+mount under React's concurrent renderer without `useTransition`.

packages/ui/react/react-audio/src/hooks/use-playlist/use-playlist.test.ts

@@ -0,0 +1,192 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, renderHook } from "@testing-library/react";
+import { usePlaylist } from "./use-playlist.js";
+import type { PlaylistItem } from "./use-playlist.types.js";
+
+const ITEMS: readonly PlaylistItem[] = [
+    { id: "a", src: "a.mp3", title: "A" },
+    { id: "b", src: "b.mp3", title: "B" },
+    { id: "c", src: "c.mp3", title: "C" },
+];
+
+describe("usePlaylist", () => {
+    it("returns undefined current for empty items", { timeout: 5000 }, () => {
+        const { result } = renderHook(() => usePlaylist([]));
+        expect(result.current.current).toBeUndefined();
+        expect(result.current.index).toBe(-1);
+        expect(result.current.length).toBe(0);
+    });
+
+    it("next/prev step within range without wrap when repeat=off", {
+        timeout: 5000,
+    }, () => {
+        const { result } = renderHook(() => usePlaylist(ITEMS));
+        expect(result.current.current?.id).toBe("a");
+        act(() => result.current.next());
+        expect(result.current.index).toBe(1);
+        act(() => result.current.next());
+        act(() => result.current.next());
+        // At end, no further next.
+        expect(result.current.index).toBe(2);
+        act(() => result.current.prev());
+        expect(result.current.index).toBe(1);
+        act(() => result.current.prev());
+        act(() => result.current.prev());
+        expect(result.current.index).toBe(0);
+    });
+
+    it("repeat=all wraps both directions", { timeout: 5000 }, () => {
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, { initialRepeat: "all" })
+        );
+        act(() => result.current.prev());
+        expect(result.current.index).toBe(2);
+        act(() => result.current.next());
+        expect(result.current.index).toBe(0);
+    });
+
+    it("repeat=one holds the cursor", { timeout: 5000 }, () => {
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, { initialIndex: 1, initialRepeat: "one" })
+        );
+        act(() => result.current.next());
+        expect(result.current.index).toBe(1);
+        act(() => result.current.prev());
+        expect(result.current.index).toBe(1);
+    });
+
+    it("skipTo jumps by id; unknown id is a no-op", { timeout: 5000 }, () => {
+        const { result } = renderHook(() => usePlaylist(ITEMS));
+        act(() => result.current.skipTo("c"));
+        expect(result.current.current?.id).toBe("c");
+        act(() => result.current.skipTo("missing"));
+        expect(result.current.current?.id).toBe("c");
+    });
+
+    it("setIndex clamps out-of-range values", { timeout: 5000 }, () => {
+        const { result } = renderHook(() => usePlaylist(ITEMS));
+        act(() => result.current.setIndex(99));
+        expect(result.current.index).toBe(2);
+        act(() => result.current.setIndex(-5));
+        expect(result.current.index).toBe(0);
+    });
+
+    it("shuffle uses injected rng and avoids repeats", {
+        timeout: 5000,
+    }, () => {
+        // rng=0 picks index 0; since cur=0 it should skip to 1.
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, { initialShuffle: true, rng: () => 0 })
+        );
+        act(() => result.current.next());
+        expect(result.current.index).toBe(1);
+    });
+
+    it("shuffle prev pops history; next/prev round-trips", {
+        timeout: 5000,
+    }, () => {
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, {
+                initialShuffle: true,
+                rng: () => 0.6, // → floor(1.8) = 1
+            })
+        );
+        act(() => result.current.next());
+        expect(result.current.index).toBe(1);
+        act(() => result.current.prev());
+        expect(result.current.index).toBe(0);
+    });
+
+    it("shuffle prev with empty history picks a new index", {
+        timeout: 5000,
+    }, () => {
+        // rng=0.4 → floor(1.2) = 1; cur=0 ≠ pick, so picks 1.
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, {
+                initialShuffle: true,
+                rng: () => 0.4,
+            })
+        );
+        act(() => result.current.prev());
+        expect(result.current.index).toBe(1);
+    });
+
+    it("setShuffle off clears history; setShuffle on does not; setRepeat updates mode", {
+        timeout: 5000,
+    }, () => {
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, { rng: () => 0.6 })
+        );
+        act(() => result.current.setShuffle(true));
+        expect(result.current.shuffle).toBe(true);
+        act(() => result.current.next());
+        act(() => result.current.setShuffle(false));
+        expect(result.current.shuffle).toBe(false);
+        act(() => result.current.setRepeat("all"));
+        expect(result.current.repeat).toBe("all");
+    });
+
+    it("skipTo under shuffle pushes history; same-id skipTo does not", {
+        timeout: 5000,
+    }, () => {
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, { initialShuffle: true, rng: () => 0.6 })
+        );
+        act(() => result.current.skipTo("c")); // pushes 0
+        act(() => result.current.skipTo("c")); // same id, no push
+        act(() => result.current.prev());
+        expect(result.current.index).toBe(0);
+    });
+
+    it("setIndex under shuffle pushes history; same index does not", {
+        timeout: 5000,
+    }, () => {
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, { initialShuffle: true, rng: () => 0.6 })
+        );
+        act(() => result.current.setIndex(2));
+        act(() => result.current.setIndex(2));
+        act(() => result.current.prev());
+        expect(result.current.index).toBe(0);
+    });
+
+    it("empty items: next/prev/skipTo/setIndex no-op", {
+        timeout: 5000,
+    }, () => {
+        const { result } = renderHook(() => usePlaylist([]));
+        act(() => result.current.next());
+        act(() => result.current.prev());
+        act(() => result.current.skipTo("a"));
+        act(() => result.current.setIndex(0));
+        expect(result.current.index).toBe(-1);
+    });
+
+    it("shuffle with length=1 stays put on next", { timeout: 5000 }, () => {
+        const single: PlaylistItem[] = [{ id: "x", src: "x.mp3" }];
+        const { result } = renderHook(() =>
+            usePlaylist(single, { initialShuffle: true, rng: () => 0 })
+        );
+        act(() => result.current.next());
+        expect(result.current.index).toBe(0);
+    });
+
+    it("initialIndex out-of-range is clamped", { timeout: 5000 }, () => {
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, { initialIndex: 99 })
+        );
+        expect(result.current.index).toBe(2);
+    });
+
+    it("default rng falls back to Math.random when opts.rng absent", {
+        timeout: 5000,
+    }, () => {
+        const { result } = renderHook(() =>
+            usePlaylist(ITEMS, { initialShuffle: true })
+        );
+        // Just exercise the default-rng branch; result is non-deterministic
+        // but must be a valid index.
+        act(() => result.current.next());
+        expect(result.current.index).toBeGreaterThanOrEqual(0);
+        expect(result.current.index).toBeLessThan(ITEMS.length);
+    });
+});

packages/ui/react/react-audio/src/hooks/use-playlist/use-playlist.ts

@@ -0,0 +1,139 @@
+import { useCallback, useMemo, useRef, useState } from "react";
+import type {
+    PlaylistItem,
+    PlaylistRepeat,
+    UsePlaylistOptions,
+    UsePlaylistResult,
+} from "./use-playlist.types.js";
+
+/**
+ * Pure (no engine) playlist controller. Owns:
+ *   - cursor `index` (clamped to `[-1, items.length - 1]`),
+ *   - `repeat` mode (`off`/`all`/`one`),
+ *   - `shuffle` flag (next/prev pick a random untouched item),
+ *   - a per-shuffle "history" so `prev` actually reverses traversal.
+ *
+ * The hook is intentionally engine-agnostic — it knows nothing about
+ * `AudioPlayerPlugin` or transport. Consumers wire `current.src` to
+ * whichever loader they use (typically `<AudioPlayer source={...}>`).
+ */
+export function usePlaylist(
+    items: readonly PlaylistItem[],
+    opts: UsePlaylistOptions = {}
+): UsePlaylistResult {
+    const length = items.length;
+    const clamp = useCallback(
+        (n: number): number => {
+            if (length === 0) return -1;
+            if (n < 0) return 0;
+            if (n >= length) return length - 1;
+            return n;
+        },
+        [length]
+    );
+
+    const [index, setIndexState] = useState<number>(() =>
+        clamp(opts.initialIndex ?? 0)
+    );
+    const [repeat, setRepeatState] = useState<PlaylistRepeat>(
+        opts.initialRepeat ?? "off"
+    );
+    const [shuffle, setShuffleState] = useState<boolean>(
+        opts.initialShuffle ?? false
+    );
+
+    const rngRef = useRef<() => number>(opts.rng ?? Math.random);
+    rngRef.current = opts.rng ?? Math.random;
+
+    // History stack of shuffle-picked indices so `prev` reverses
+    // exactly what `next` did under shuffle.
+    const historyRef = useRef<number[]>([]);
+
+    const pickShuffle = useCallback((): number => {
+        if (length <= 1) return clamp(0);
+        // Avoid immediately repeating the current track.
+        let pick = Math.floor(rngRef.current() * length);
+        if (pick === index) pick = (pick + 1) % length;
+        return pick;
+    }, [length, index, clamp]);
+
+    const next = useCallback(() => {
+        if (length === 0) return;
+        setIndexState((cur) => {
+            if (repeat === "one") return cur;
+            if (shuffle) {
+                historyRef.current.push(cur);
+                return pickShuffle();
+            }
+            const candidate = cur + 1;
+            if (candidate >= length) return repeat === "all" ? 0 : cur;
+            return candidate;
+        });
+    }, [length, repeat, shuffle, pickShuffle]);
+
+    const prev = useCallback(() => {
+        if (length === 0) return;
+        setIndexState((cur) => {
+            if (repeat === "one") return cur;
+            if (shuffle) {
+                const popped = historyRef.current.pop();
+                if (popped !== undefined) return clamp(popped);
+                return pickShuffle();
+            }
+            const candidate = cur - 1;
+            if (candidate < 0) return repeat === "all" ? length - 1 : cur;
+            return candidate;
+        });
+    }, [length, repeat, shuffle, clamp, pickShuffle]);
+
+    const skipTo = useCallback(
+        (id: string) => {
+            const found = items.findIndex((it) => it.id === id);
+            if (found === -1) return;
+            setIndexState((cur) => {
+                if (shuffle && cur !== found) historyRef.current.push(cur);
+                return found;
+            });
+        },
+        [items, shuffle]
+    );
+
+    const setIndex = useCallback(
+        (n: number) => {
+            setIndexState((cur) => {
+                const next_ = clamp(n);
+                if (shuffle && cur !== next_) historyRef.current.push(cur);
+                return next_;
+            });
+        },
+        [clamp, shuffle]
+    );
+
+    const setRepeat = useCallback((mode: PlaylistRepeat) => {
+        setRepeatState(mode);
+    }, []);
+
+    const setShuffle = useCallback((enabled: boolean) => {
+        setShuffleState(enabled);
+        if (!enabled) historyRef.current = [];
+    }, []);
+
+    const current = useMemo<PlaylistItem | undefined>(
+        () => (index >= 0 && index < length ? items[index] : undefined),
+        [items, index, length]
+    );
+
+    return {
+        current,
+        index,
+        length,
+        repeat,
+        shuffle,
+        next,
+        prev,
+        skipTo,
+        setIndex,
+        setRepeat,
+        setShuffle,
+    };
+}

packages/ui/react/react-audio/src/hooks/use-playlist/use-playlist.types.ts

@@ -0,0 +1,55 @@
+/**
+ * A single entry in a playlist. The shape is intentionally minimal —
+ * the consumer carries whatever metadata it needs in `meta`, while
+ * `id` is the only field required by `usePlaylist` for diffing.
+ *
+ * `src` is the URL/Blob/asset reference the consumer hands to its
+ * own loader (e.g. `<AudioPlayer>`). `usePlaylist` does **not** load
+ * audio — it only manages the queue.
+ */
+export interface PlaylistItem {
+    readonly id: string;
+    readonly src: string;
+    readonly title?: string;
+    readonly artist?: string;
+    readonly durationSec?: number;
+    readonly meta?: Readonly<Record<string, unknown>>;
+}
+
+export type PlaylistRepeat = "off" | "all" | "one";
+
+export interface UsePlaylistOptions {
+    /** Initial cursor position. Default 0. Clamped to `[0, items.length - 1]`. */
+    readonly initialIndex?: number;
+    /** Initial repeat mode. Default `"off"`. */
+    readonly initialRepeat?: PlaylistRepeat;
+    /** Initial shuffle state. Default `false`. */
+    readonly initialShuffle?: boolean;
+    /**
+     * Optional deterministic RNG injection point — primarily for
+     * tests. Receives no arguments and returns a number in `[0, 1)`.
+     * Defaults to `Math.random` (re-bound per call, no captured ref).
+     */
+    readonly rng?: () => number;
+}
+
+export interface UsePlaylistResult {
+    /** Current item, or `undefined` if `items` is empty. */
+    readonly current: PlaylistItem | undefined;
+    /** Cursor position; `-1` when `items` is empty. */
+    readonly index: number;
+    /** Total item count. */
+    readonly length: number;
+    readonly repeat: PlaylistRepeat;
+    readonly shuffle: boolean;
+    /** Advance one position (wraps per `repeat`). */
+    next(): void;
+    /** Step back one position (wraps per `repeat`). */
+    prev(): void;
+    /** Jump to a specific item id; no-op if not in `items`. */
+    skipTo(id: string): void;
+    /** Jump to an absolute index; clamped to range. */
+    setIndex(index: number): void;
+    setRepeat(mode: PlaylistRepeat): void;
+    setShuffle(enabled: boolean): void;
+}

packages/ui/react/react-audio/src/hooks/use-plugin-chain/use-plugin-chain.md

@@ -0,0 +1,82 @@
+# `hooks/use-plugin-chain`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`usePluginChain(trackId)` returns a handle for the `PluginChain`
+associated with a track. The provider lazily creates the chain
+through its `ChainMap` on first call, so every consumer asking for
+the same track sees the same chain. The hook subscribes to the
+chain's composition events — `plugin-added`, `plugin-removed`,
+`plugin-moved`, `plugin-replaced`, `bypass-changed` — and re-renders
+the consumer when any of them fire. Listener cleanup on unmount is
+exact: the chain's listener count returns to the pre-mount baseline.
+
+## Features
+
+- Lazy per-track chain creation via the provider's `ChainMap`.
+- Re-renders on chain-composition events (5 events subscribed).
+- Stable `add` / `remove` / `move` / `replace` / `bypass` /
+  `snapshot` / `restore` callback identities across re-renders.
+- `restore(input)` delegates to `chain.restore(input, registry)`
+  using the provider's `PluginRegistry`.
+- Exact listener cleanup on unmount.
+
+## Usage: Basic
+
+```tsx
+import { usePluginChain } from "@suaveplan/react-audio";
+
+function ChainBar({ trackId, eq }: { trackId: string; eq: AudioFxPlugin }) {
+    const { plugins, add } = usePluginChain(trackId);
+    return (
+        <div>
+            <button type="button" onClick={() => add(eq)}>Add EQ</button>
+            <span>{plugins.length} plugin(s)</span>
+        </div>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { usePluginChain } from "@suaveplan/react-audio";
+
+function Reorderable({ trackId }: { trackId: string }) {
+    const { plugins, move, bypass, replace } = usePluginChain(trackId);
+    return (
+        <ul>
+            {plugins.map((plugin, index) => (
+                <li key={plugin.metadata.id}>
+                    <button onClick={() => move(index, Math.max(0, index - 1))}>↑</button>
+                    <button onClick={() => bypass(index, true)}>Bypass</button>
+                    <span>{plugin.metadata.id}</span>
+                </li>
+            ))}
+        </ul>
+    );
+}
+```
+
+## API Reference
+
+- `usePluginChain(trackId): UsePluginChainResult`.
+- `UsePluginChainResult = { chain, plugins, add, remove, move,
+  replace, bypass, snapshot, restore }`.
+
+## Implementation Notes
+
+The subscribe path registers a listener on each of the five
+composition events and returns a teardown that calls every
+`UnsubscribeFn`. Because the chain's `event-bus` increments and
+decrements listener counts symmetrically, the post-unmount listener
+count is exactly the pre-mount count. `replace` is implemented as
+`remove + add` at the same index because `PluginChain` does not
+currently expose a single-call `replace`; the chain emits a
+`plugin-removed` followed by a `plugin-added`, both of which the
+hook is subscribed to, so the consumer sees one composite re-render
+(React batches state updates within the same task).

packages/ui/react/react-audio/src/hooks/use-plugin-chain/use-plugin-chain.test.tsx

@@ -0,0 +1,103 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, waitFor } from "@testing-library/react";
+import { makeFakePlugin, renderHookWithProvider } from "../../test-utils.js";
+import { usePluginChain } from "./use-plugin-chain.js";
+
+describe("usePluginChain", () => {
+    it("adding a plugin re-renders the consumer with the new list", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => usePluginChain("track-a"));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        const eq = makeFakePlugin({ id: "eq-1" });
+        act(() => {
+            handle.current!.add(eq);
+        });
+        await waitFor(() => expect(handle.current!.plugins.length).toBe(1));
+        expect(
+            handle.current!.plugins[handle.current!.plugins.length - 1]
+        ).toBe(eq);
+    });
+
+    it("remove, move, bypass, replace work and emit events", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => usePluginChain("track-b"));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        const a = makeFakePlugin({ id: "a" });
+        const b = makeFakePlugin({ id: "b" });
+        const c = makeFakePlugin({ id: "c" });
+        act(() => {
+            handle.current!.add(a);
+            handle.current!.add(b);
+        });
+        await waitFor(() => expect(handle.current!.plugins.length).toBe(2));
+
+        act(() => handle.current!.move(0, 1));
+        await waitFor(() =>
+            expect(handle.current!.plugins[0]!.metadata.id).toBe("b")
+        );
+
+        act(() => handle.current!.bypass("a", true));
+
+        act(() => handle.current!.replace("a", c));
+        await waitFor(() =>
+            expect(
+                handle.current!.plugins.find((p) => p.metadata.id === "c")
+            ).toBeDefined()
+        );
+
+        // Cover the numeric-index branch of replace.
+        const d = makeFakePlugin({ id: "d" });
+        act(() => handle.current!.replace(0, d));
+        await waitFor(() =>
+            expect(handle.current!.plugins[0]!.metadata.id).toBe("d")
+        );
+
+        act(() => handle.current!.remove(0));
+        await waitFor(() => expect(handle.current!.plugins.length).toBe(1));
+
+        const snap = handle.current!.snapshot();
+        expect(snap.id).toBe("track-b");
+    });
+
+    it("restore delegates to chain.restore via the registry", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() =>
+            usePluginChain("restore-t")
+        );
+        await waitFor(() => expect(handle.current).toBeDefined());
+        const empty = {
+            id: "restore-t",
+            name: "restore-t",
+            channels: 2,
+            sampleRate: 48_000,
+            blockSize: 128,
+            plugins: [],
+        };
+        await handle.current!.restore(empty);
+        expect(handle.current!.plugins.length).toBe(0);
+    });
+
+    it("unmount removes every listener", { timeout: 30000 }, async () => {
+        const handle = renderHookWithProvider(() => usePluginChain("track-c"));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        const chain = handle.current!.chain;
+        const eventBus = (
+            chain as unknown as {
+                events: { listeners: Map<string, Set<unknown>> };
+            }
+        ).events;
+        const before = new Map<string, number>();
+        for (const [name, set] of eventBus.listeners) {
+            before.set(name, set.size);
+        }
+        act(() => {
+            handle.unmount();
+        });
+        for (const [name, set] of eventBus.listeners) {
+            expect(set.size).toBeLessThanOrEqual(before.get(name) ?? 0);
+        }
+    });
+});

packages/ui/react/react-audio/src/hooks/use-plugin-chain/use-plugin-chain.ts

@@ -0,0 +1,130 @@
+import type {
+    AudioFxPlugin,
+    ChainSnapshot,
+    PluginChain,
+} from "@suaveplan/audio-fx-plugin-base";
+import { useCallback, useMemo, useRef, useSyncExternalStore } from "react";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+export interface UsePluginChainResult {
+    readonly chain: PluginChain;
+    readonly plugins: ReadonlyArray<AudioFxPlugin>;
+    add(plugin: AudioFxPlugin, at?: number): void;
+    remove(idOrIndex: string | number): void;
+    move(from: number, to: number): void;
+    /**
+     * Replace the plugin at `idOrIndex` with `plugin`. Implemented
+     * atomically as remove + add at the same slot index.
+     */
+    replace(idOrIndex: string | number, plugin: AudioFxPlugin): void;
+    bypass(idOrIndex: string | number, bypassed: boolean): void;
+    snapshot(): ChainSnapshot;
+    restore(input: unknown): Promise<void>;
+}
+
+const REFLECT_EVENTS = [
+    "plugin-added",
+    "plugin-removed",
+    "plugin-moved",
+    "plugin-replaced",
+    "bypass-changed",
+] as const;
+
+/**
+ * Hook handle for the `PluginChain` associated with `trackId`. The
+ * chain is created lazily via the provider's `ChainMap` on first
+ * call. The hook subscribes to every chain-composition event and
+ * re-renders the consumer whenever one fires. Listener cleanup is
+ * exact on unmount.
+ */
+export function usePluginChain(trackId: string): UsePluginChainResult {
+    const { chains, registry } = useProviderStateOrThrow();
+    const chain = useMemo(() => chains.getOrCreate(trackId), [chains, trackId]);
+
+    // Cache the plugins array so `useSyncExternalStore.getSnapshot`
+    // returns an identity-stable reference between change events;
+    // returning a new array on every call makes React treat the store
+    // as unstable and tear the consuming subtree down (which would
+    // dispose the chain via the provider's effect cleanup).
+    const cacheRef = useRef<ReadonlyArray<AudioFxPlugin>>(chain.plugins);
+
+    const subscribe = useCallback(
+        (listener: () => void) => {
+            const onChange = () => {
+                cacheRef.current = chain.plugins;
+                listener();
+            };
+            const offs = REFLECT_EVENTS.map((event) =>
+                chain.on(event, onChange)
+            );
+            return () => {
+                for (const off of offs) {
+                    off();
+                }
+            };
+        },
+        [chain]
+    );
+
+    const getSnapshot = useCallback(() => cacheRef.current, []);
+    const plugins = useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+
+    const add = useCallback<UsePluginChainResult["add"]>(
+        (plugin, at) => {
+            chain.add(plugin, at);
+        },
+        [chain]
+    );
+    const remove = useCallback<UsePluginChainResult["remove"]>(
+        (idOrIndex) => {
+            chain.remove(idOrIndex);
+        },
+        [chain]
+    );
+    const move = useCallback<UsePluginChainResult["move"]>(
+        (from, to) => {
+            chain.move(from, to);
+        },
+        [chain]
+    );
+    const replace = useCallback<UsePluginChainResult["replace"]>(
+        (idOrIndex, plugin) => {
+            const slots = chain.plugins;
+            const index =
+                typeof idOrIndex === "number"
+                    ? idOrIndex
+                    : slots.findIndex((p) => p.metadata.id === idOrIndex);
+            chain.remove(idOrIndex);
+            chain.add(plugin, Math.max(0, index));
+        },
+        [chain]
+    );
+    const bypass = useCallback<UsePluginChainResult["bypass"]>(
+        (idOrIndex, bypassed) => {
+            chain.bypass(idOrIndex, bypassed);
+        },
+        [chain]
+    );
+    const snapshot = useCallback<UsePluginChainResult["snapshot"]>(
+        () => chain.snapshot(),
+        [chain]
+    );
+    const restore = useCallback<UsePluginChainResult["restore"]>(
+        async (input) => {
+            await chain.restore(input, registry);
+        },
+        [chain, registry]
+    );
+
+    return {
+        chain,
+        plugins,
+        add,
+        remove,
+        move,
+        replace,
+        bypass,
+        snapshot,
+        restore,
+    };
+}

packages/ui/react/react-audio/src/hooks/use-preset/use-preset.md

@@ -0,0 +1,81 @@
+# `hooks/use-preset`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`usePreset(plugin)` exposes plugin-level preset operations as
+React-friendly callbacks: `get` reads the current preset, `apply`
+writes one back, and `save` / `load` persist through the provider's
+optional preset store. The hook gates `save`/`load` on the presence
+of a store; if none is configured (or if the store throws), the hook
+raises `ReactAudioError(REACT_AUDIO.PRESET_STORE_FAILED)` carrying
+the offending id and the underlying cause.
+
+## Features
+
+- `get(): PresetSnapshot` — synchronous read.
+- `apply(preset): void` — synchronous write.
+- `save(id): Promise<void>` — async write through the preset store.
+- `load(id): Promise<void>` — async read + apply.
+- Structured errors: `PRESET_STORE_FAILED` for missing store, save
+  failure, load failure, and preset-not-found.
+
+## Usage: Basic
+
+```tsx
+import { usePreset } from "@suaveplan/react-audio";
+
+function PresetButtons({ plugin }: { plugin: AudioFxPlugin }) {
+    const { save, load } = usePreset(plugin);
+    return (
+        <>
+            <button type="button" onClick={() => save("default")}>Save</button>
+            <button type="button" onClick={() => load("default")}>Load</button>
+        </>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { usePreset } from "@suaveplan/react-audio";
+
+function ExportPreset({ plugin }: { plugin: AudioFxPlugin }) {
+    const { get } = usePreset(plugin);
+    return (
+        <button
+            type="button"
+            onClick={() => {
+                const preset = get();
+                navigator.clipboard.writeText(JSON.stringify(preset));
+            }}
+        >
+            Copy JSON
+        </button>
+    );
+}
+```
+
+## API Reference
+
+- `usePreset(plugin): { get, apply, save, load }`.
+
+## Implementation Notes
+
+The hook wraps each store interaction in a try/catch that converts
+underlying errors into `ReactAudioError(PRESET_STORE_FAILED)` with
+the original `Error` set as `cause`. The store is allowed to be
+undefined; consumers that don't need persistence omit it from
+provider options and use `get` / `apply` only. Promise rejections are
+deliberately wrapped (rather than re-thrown raw) so a single
+`error instanceof ReactAudioError` branch handles every failure path.
+The four failure modes — missing store, store-rejected save,
+store-rejected load, preset-not-found — share one code
+(`PRESET_STORE_FAILED`) but distinct `messageKey`s so an i18n layer
+can branch on the message resolver instead of the code. Non-Error
+values thrown by a store are narrowed to `undefined` causes so the
+wrapper Error remains type-safe.

packages/ui/react/react-audio/src/hooks/use-preset/use-preset.test.tsx

@@ -0,0 +1,169 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { waitFor } from "@testing-library/react";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+import type { PresetStore } from "../../provider/provider-options.js";
+import { makeFakePlugin, renderHookWithProvider } from "../../test-utils.js";
+import { usePreset } from "./use-preset.js";
+
+describe("usePreset", () => {
+    it("get/apply work without a preset store", {
+        timeout: 30000,
+    }, async () => {
+        const plugin = makeFakePlugin();
+        const handle = renderHookWithProvider(() => usePreset(plugin));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        const snapshot = handle.current!.get();
+        expect(snapshot.parameters.gain).toBe(1);
+        handle.current!.apply({
+            schemaVersion: 1,
+            pluginType: plugin.metadata.id,
+            parameters: { gain: 0.7, tone: 0.3 },
+        });
+        expect(plugin.getParameter("gain")).toBe(0.7);
+    });
+
+    it("save/load round-trip via store", { timeout: 30000 }, async () => {
+        const plugin = makeFakePlugin();
+        const memory = new Map<string, unknown>();
+        const store: PresetStore = {
+            async save(kind, id, payload) {
+                memory.set(`${kind}:${id}`, payload);
+            },
+            async load(kind, id) {
+                return memory.get(`${kind}:${id}`) as never;
+            },
+        };
+        const handle = renderHookWithProvider(() => usePreset(plugin), {
+            options: { presetStore: store },
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+        plugin.setParameter("gain", 0.42);
+        await handle.current!.save("p1");
+        plugin.setParameter("gain", 0.0);
+        await handle.current!.load("p1");
+        expect(plugin.getParameter("gain")).toBeCloseTo(0.42);
+    });
+
+    it("save throws REACT_AUDIO.PRESET_STORE_FAILED when no store", {
+        timeout: 30000,
+    }, async () => {
+        const plugin = makeFakePlugin();
+        const handle = renderHookWithProvider(() => usePreset(plugin));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        let caught: unknown;
+        try {
+            await handle.current!.save("x");
+        } catch (e) {
+            caught = e;
+        }
+        expect(caught).toBeInstanceOf(ReactAudioError);
+        expect((caught as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.PRESET_STORE_FAILED
+        );
+    });
+
+    it("load throws PRESET_STORE_FAILED for missing preset / save error / load error", {
+        timeout: 30000,
+    }, async () => {
+        const plugin = makeFakePlugin();
+        const store: PresetStore = {
+            async save() {
+                throw new Error("save broke");
+            },
+            async load() {
+                return undefined;
+            },
+        };
+        const handle = renderHookWithProvider(() => usePreset(plugin), {
+            options: { presetStore: store },
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+
+        let saveErr: unknown;
+        try {
+            await handle.current!.save("x");
+        } catch (e) {
+            saveErr = e;
+        }
+        expect((saveErr as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.PRESET_STORE_FAILED
+        );
+
+        let loadErr: unknown;
+        try {
+            await handle.current!.load("x");
+        } catch (e) {
+            loadErr = e;
+        }
+        expect((loadErr as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.PRESET_STORE_FAILED
+        );
+
+        // load with throwing store
+        const throwingStore: PresetStore = {
+            async save() {},
+            async load() {
+                throw new Error("load broke");
+            },
+        };
+        const handle2 = renderHookWithProvider(() => usePreset(plugin), {
+            options: { presetStore: throwingStore },
+        });
+        await waitFor(() => expect(handle2.current).toBeDefined());
+        let loadErr2: unknown;
+        try {
+            await handle2.current!.load("y");
+        } catch (e) {
+            loadErr2 = e;
+        }
+        expect((loadErr2 as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.PRESET_STORE_FAILED
+        );
+    });
+
+    it("save/load wrap non-Error causes as undefined", {
+        timeout: 30000,
+    }, async () => {
+        const plugin = makeFakePlugin();
+        const weirdStore: PresetStore = {
+            // Throw non-Error values to exercise the
+            // `cause instanceof Error ? cause : undefined` branch.
+            save() {
+                throw "string-thrown";
+            },
+            load() {
+                throw 42;
+            },
+        };
+        const handle = renderHookWithProvider(() => usePreset(plugin), {
+            options: { presetStore: weirdStore },
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+        await expect(handle.current!.save("x")).rejects.toBeInstanceOf(
+            ReactAudioError
+        );
+        await expect(handle.current!.load("x")).rejects.toBeInstanceOf(
+            ReactAudioError
+        );
+    });
+
+    it("load without store throws PRESET_STORE_FAILED", {
+        timeout: 30000,
+    }, async () => {
+        const plugin = makeFakePlugin();
+        const handle = renderHookWithProvider(() => usePreset(plugin));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        let caught: unknown;
+        try {
+            await handle.current!.load("x");
+        } catch (e) {
+            caught = e;
+        }
+        expect((caught as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.PRESET_STORE_FAILED
+        );
+    });
+});

packages/ui/react/react-audio/src/hooks/use-preset/use-preset.ts

@@ -0,0 +1,108 @@
+import type {
+    AudioFxPlugin,
+    PresetSnapshot,
+} from "@suaveplan/audio-fx-plugin-base";
+import { useCallback } from "react";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../../error-codes/error-codes.js";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+export interface UsePresetResult {
+    /** Read the plugin's current `PresetSnapshot`. */
+    get(): PresetSnapshot;
+    /** Apply a `PresetSnapshot` to the plugin. */
+    apply(preset: PresetSnapshot): void;
+    /**
+     * Persist the current preset through the provider's preset
+     * store, keyed by `id`. Throws
+     * `REACT_AUDIO.PRESET_STORE_FAILED` if no preset store is
+     * configured or the store rejects the write.
+     */
+    save(id: string): Promise<void>;
+    /**
+     * Load a preset by `id` from the provider's preset store and
+     * apply it to the plugin. Throws
+     * `REACT_AUDIO.PRESET_STORE_FAILED` if no preset store is
+     * configured or the store rejects the read.
+     */
+    load(id: string): Promise<void>;
+}
+
+/**
+ * Plugin-level preset save/load. Direct `get` / `apply` work
+ * without a preset store; `save` / `load` require one to be wired
+ * through provider options.
+ */
+export function usePreset(plugin: AudioFxPlugin): UsePresetResult {
+    const { presetStore } = useProviderStateOrThrow();
+
+    const get = useCallback(() => plugin.getPreset(), [plugin]);
+    const apply = useCallback(
+        (preset: PresetSnapshot) => plugin.applyPreset(preset),
+        [plugin]
+    );
+
+    const save = useCallback(
+        async (id: string) => {
+            if (presetStore === undefined) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.preset-store-missing",
+                    { context: { id, kind: "plugin" } }
+                );
+            }
+            try {
+                await presetStore.save("plugin", id, plugin.getPreset());
+            } catch (cause) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.preset-store-save-failed",
+                    {
+                        context: { id, kind: "plugin" },
+                        cause: cause instanceof Error ? cause : undefined,
+                    }
+                );
+            }
+        },
+        [plugin, presetStore]
+    );
+
+    const load = useCallback(
+        async (id: string) => {
+            if (presetStore === undefined) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.preset-store-missing",
+                    { context: { id, kind: "plugin" } }
+                );
+            }
+            let preset: PresetSnapshot | undefined;
+            try {
+                const result = await presetStore.load("plugin", id);
+                preset = result as PresetSnapshot | undefined;
+            } catch (cause) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.preset-store-load-failed",
+                    {
+                        context: { id, kind: "plugin" },
+                        cause: cause instanceof Error ? cause : undefined,
+                    }
+                );
+            }
+            if (preset === undefined) {
+                throw new ReactAudioError(
+                    REACT_AUDIO_CODES.PRESET_STORE_FAILED,
+                    "react-audio.preset-not-found",
+                    { context: { id, kind: "plugin" } }
+                );
+            }
+            plugin.applyPreset(preset);
+        },
+        [plugin, presetStore]
+    );
+
+    return { get, apply, save, load };
+}

packages/ui/react/react-audio/src/hooks/use-provider-state.md

@@ -0,0 +1,70 @@
+# `hooks/use-provider-state`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+Internal helpers shared across every public hook. They centralise the
+two structured-error throws every engine-dependent hook must perform:
+`REACT_AUDIO.NO_PROVIDER` when the consumer renders outside an
+`<AudioProvider>` ancestor, and `REACT_AUDIO.PROVIDER_PENDING` when
+the engine has not yet finished its async init. Keeping the throw
+logic in one file means there is exactly one place to audit the error
+contract.
+
+## Features
+
+- `useProviderStateOrThrow()` — returns the resolved `ProviderState`
+  or throws.
+- `useAudioContextOrThrow()` — returns the raw `AudioContextValue`
+  (without the pending check) for hooks like `useEngineState` that
+  need to *report* the lifecycle phase rather than throw on it.
+
+## Usage: Basic
+
+```ts
+import { useProviderStateOrThrow } from "@suaveplan/react-audio";
+
+function MyHook() {
+    const state = useProviderStateOrThrow();
+    return state.transport;
+}
+```
+
+## Usage: Advanced
+
+```ts
+import { useAudioContextOrThrow } from "@suaveplan/react-audio";
+
+function useReadyOrLoading(): "ready" | "loading" {
+    const ctx = useAudioContextOrThrow();
+    return ctx.engineState === "ready" ? "ready" : "loading";
+}
+```
+
+## API Reference
+
+- `useProviderStateOrThrow(): ProviderState` — throws
+  `REACT_AUDIO.NO_PROVIDER` outside provider; throws
+  `REACT_AUDIO.PROVIDER_PENDING` while engine init is pending.
+- `useAudioContextOrThrow(): AudioContextValue` — throws
+  `REACT_AUDIO.NO_PROVIDER` outside provider.
+
+## Implementation Notes
+
+`useContext` returns `null` as the "no provider" sentinel because the
+context's default value is `null`. The two helpers use a single
+discriminator check (`ctx === null`) for that path so the throw site
+is canonical. `useProviderStateOrThrow` additionally checks for
+`ctx.state === null` (the async init window) and throws
+`PROVIDER_PENDING` so engine-dependent hooks fail fast — consumers
+typically gate on `useEngineState() === 'ready'` before rendering
+those hooks' subtrees. The split into two helpers exists so
+`useEngineState` itself can read the phase without throwing on it —
+otherwise the consumer would have no way to discover "we're still
+initialising" without crashing the component tree. Both helpers
+register exactly one React hook (`useContext`) so any downstream hook
+can register additional `useCallback` / `useSyncExternalStore` calls
+unconditionally and stay compliant with the Rules of Hooks.

packages/ui/react/react-audio/src/hooks/use-provider-state.test.tsx

@@ -0,0 +1,68 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { renderHook } from "@testing-library/react";
+import {
+    REACT_AUDIO_CODES,
+    type ReactAudioError,
+} from "../error-codes/error-codes.js";
+import { AudioReactContext } from "../provider/audio-context.js";
+import {
+    useAudioContextOrThrow,
+    useProviderStateOrThrow,
+} from "./use-provider-state.js";
+
+describe("use-provider-state", () => {
+    it("useAudioContextOrThrow throws NO_PROVIDER outside provider", {
+        timeout: 5000,
+    }, () => {
+        let caught: unknown;
+        try {
+            renderHook(() => useAudioContextOrThrow());
+        } catch (e) {
+            caught = e;
+        }
+        expect((caught as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.NO_PROVIDER
+        );
+    });
+
+    it("useProviderStateOrThrow throws PROVIDER_PENDING when state is null", {
+        timeout: 5000,
+    }, () => {
+        let caught: unknown;
+        try {
+            renderHook(() => useProviderStateOrThrow(), {
+                wrapper: ({ children }) => (
+                    <AudioReactContext.Provider
+                        value={{
+                            state: null,
+                            engineState: "pending",
+                            error: null,
+                            version: 0,
+                        }}
+                    >
+                        {children}
+                    </AudioReactContext.Provider>
+                ),
+            });
+        } catch (e) {
+            caught = e;
+        }
+        expect((caught as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.PROVIDER_PENDING
+        );
+    });
+
+    it("useProviderStateOrThrow throws NO_PROVIDER outside provider", {
+        timeout: 5000,
+    }, () => {
+        let caught: unknown;
+        try {
+            renderHook(() => useProviderStateOrThrow());
+        } catch (e) {
+            caught = e;
+        }
+        expect((caught as ReactAudioError).code).toBe(
+            REACT_AUDIO_CODES.NO_PROVIDER
+        );
+    });
+});

packages/ui/react/react-audio/src/hooks/use-provider-state.ts

@@ -0,0 +1,57 @@
+import { useContext } from "react";
+import {
+    REACT_AUDIO_CODES,
+    ReactAudioError,
+} from "../error-codes/error-codes.js";
+import {
+    type AudioContextValue,
+    AudioReactContext,
+    type ProviderState,
+} from "../provider/audio-context.js";
+
+/**
+ * Internal helper: returns the resolved `ProviderState`, throwing
+ * `REACT_AUDIO.NO_PROVIDER` if rendered outside `<AudioProvider>`
+ * and `REACT_AUDIO.PROVIDER_PENDING` if the engine has not yet
+ * finished its async init.
+ *
+ * Implementation note: `useContext` is the only React hook called by
+ * this helper, so any downstream hook that uses it can register its
+ * own `useCallback`/`useMemo`/`useSyncExternalStore` hooks
+ * unconditionally without violating the Rules of Hooks. The throws
+ * happen *after* the context read, so the hook count is the same
+ * across the pending → ready transition.
+ */
+export function useProviderStateOrThrow(): ProviderState {
+    const ctx = useContext(AudioReactContext);
+    if (ctx === null) {
+        throw new ReactAudioError(
+            REACT_AUDIO_CODES.NO_PROVIDER,
+            "react-audio.no-provider"
+        );
+    }
+    if (ctx.state === null) {
+        throw new ReactAudioError(
+            REACT_AUDIO_CODES.PROVIDER_PENDING,
+            "react-audio.provider-pending",
+            { context: { engineState: ctx.engineState } }
+        );
+    }
+    return ctx.state;
+}
+
+/**
+ * Internal helper: returns the raw context value (without throwing
+ * on pending), throwing `REACT_AUDIO.NO_PROVIDER` if the consumer
+ * is outside `<AudioProvider>`. Used by `useEngineState`.
+ */
+export function useAudioContextOrThrow(): AudioContextValue {
+    const ctx = useContext(AudioReactContext);
+    if (ctx === null) {
+        throw new ReactAudioError(
+            REACT_AUDIO_CODES.NO_PROVIDER,
+            "react-audio.no-provider"
+        );
+    }
+    return ctx;
+}

packages/ui/react/react-audio/src/hooks/use-timeline/use-timeline.md

@@ -0,0 +1,74 @@
+# `hooks/use-timeline`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useTimeline()` returns the provider's single `TimelineEngine`
+instance, the canonical owner of timeline state — tracks, clips,
+selection, loop region, master volume, undo/redo. The engine exposes
+its own typed event surface (`engine.on(event, listener)`); consumers
+who want to *subscribe* to engine events should pair this hook with
+`useSyncExternalStore` and pass `engine.on(...)` as the subscribe
+callback. The hook itself returns the engine handle and does not
+trigger re-renders on engine state changes.
+
+## Features
+
+- Returns the `TimelineEngine` instance owned by the provider.
+- Stable identity across re-renders within a ready phase.
+- Throws `REACT_AUDIO.NO_PROVIDER` outside `<AudioProvider>`.
+- Throws `REACT_AUDIO.PROVIDER_PENDING` during async init.
+
+## Usage: Basic
+
+```tsx
+import { useTimeline } from "@suaveplan/react-audio";
+
+function AddTrackButton() {
+    const timeline = useTimeline();
+    return (
+        <button type="button" onClick={() => timeline.addTrack({ name: "New Track" })}>
+            Add track
+        </button>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useSyncExternalStore } from "react";
+import { useTimeline } from "@suaveplan/react-audio";
+
+function useTrackCount(): number {
+    const timeline = useTimeline();
+    return useSyncExternalStore(
+        (listener) => timeline.on("trackChange", listener as never),
+        () => timeline.getState().tracks.length,
+        () => timeline.getState().tracks.length
+    );
+}
+```
+
+## API Reference
+
+- `useTimeline(): TimelineEngine` — see
+  `@suaveplan/audio-timeline` for the full engine surface.
+
+## Implementation Notes
+
+The hook deliberately stops short of re-rendering on every engine
+event. The `TimelineEngine` has a rich change surface and re-rendering
+on every state delta would be expensive at chain scale. Consumers
+choose which events they care about and pair the engine handle with
+`useSyncExternalStore` for narrow subscriptions, paying only for the
+re-renders they want. Mutator methods (`addTrack`, `updateTrack`,
+`removeTrack`, `setTempo`, `setMasterVolume`, …) are exposed directly
+on the engine handle — callers wrap them in their own callbacks when
+they need referential stability across renders. For per-track state
+prefer `useTrack(id)`, which already wraps `useSyncExternalStore`
+against the timeline's `trackChange` event so its subscription is
+narrow by construction.

packages/ui/react/react-audio/src/hooks/use-timeline/use-timeline.test.tsx

@@ -0,0 +1,17 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, waitFor } from "@testing-library/react";
+import { renderHookWithProvider } from "../../test-utils.js";
+import { useTimeline } from "./use-timeline.js";
+
+describe("useTimeline", () => {
+    it("returns the TimelineEngine instance and supports addTrack", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => useTimeline());
+        await waitFor(() => expect(handle.current).toBeDefined());
+        act(() => {
+            handle.current!.addTrack({ name: "t1" });
+        });
+        expect(handle.current!.getState().tracks.length).toBeGreaterThan(0);
+    });
+});

packages/ui/react/react-audio/src/hooks/use-timeline/use-timeline.ts

@@ -0,0 +1,13 @@
+import type { TimelineEngine } from "@suaveplan/audio-timeline";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+/**
+ * Returns the provider's `TimelineEngine` instance. The engine
+ * exposes track / clip CRUD, transport controls, undo/redo, and a
+ * typed event surface (`engine.on(...)`); consumers wishing to
+ * subscribe to specific events should use `useSyncExternalStore`
+ * with `engine.on(...)` as the subscribe callback.
+ */
+export function useTimeline(): TimelineEngine {
+    return useProviderStateOrThrow().timeline;
+}

packages/ui/react/react-audio/src/hooks/use-track/use-track.md

@@ -0,0 +1,74 @@
+# `hooks/use-track`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useTrack(trackId)` subscribes to a single track on the
+`TimelineEngine` by id and re-renders only when that specific track
+changes. It returns the live `Track` snapshot (or `undefined` if no
+track has that id) plus pre-bound `update` / `remove` callbacks. The
+hook is the canonical way to render per-track UI without re-rendering
+on every other track's state change.
+
+## Features
+
+- Re-renders only on `trackChange` events for the same id.
+- Returns `undefined` for unknown ids — render-safe.
+- Stable `update` / `remove` identities across re-renders.
+- `useSyncExternalStore`-based subscription with SSR-consistent
+  snapshots.
+- Listener is removed on unmount.
+
+## Usage: Basic
+
+```tsx
+import { useTrack } from "@suaveplan/react-audio";
+
+function TrackName({ trackId }: { trackId: string }) {
+    const { track } = useTrack(trackId);
+    return <span>{track?.name ?? "(missing track)"}</span>;
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useTrack } from "@suaveplan/react-audio";
+
+function MuteToggle({ trackId }: { trackId: string }) {
+    const { track, update } = useTrack(trackId);
+    if (track === undefined) return null;
+    return (
+        <button
+            type="button"
+            aria-pressed={track.muted}
+            onClick={() => update({ muted: !track.muted })}
+        >
+            {track.muted ? "Unmute" : "Mute"}
+        </button>
+    );
+}
+```
+
+## API Reference
+
+- `useTrack(trackId): { track: Track | undefined, update, remove }`.
+
+## Implementation Notes
+
+The hook caches the resolved Track in a `ref` so
+`useSyncExternalStore.getSnapshot` is identity-stable between change
+events. Without that cache, `timeline.getState().tracks.find(...)`
+would build a new wrapper on every snapshot read; React 18+ treats
+that as an unstable store and tears the consuming subtree down on
+the next commit. Refresh fires on every `trackChange` from the
+timeline AND from local `update` / `remove` mutators — the
+underlying engine emits `trackChange` only for tracks STILL present
+in the list, so removing the last track of an id needs the mutator
+to update the cache directly. After removal the hook continues to
+render but `track` becomes `undefined`. Components consuming
+`update` / `remove` should expect those callbacks to settle
+synchronously; the next React commit reflects the change.

packages/ui/react/react-audio/src/hooks/use-track/use-track.test.tsx

@@ -0,0 +1,41 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, waitFor } from "@testing-library/react";
+import { renderHookWithProvider } from "../../test-utils.js";
+import { useTimeline } from "../use-timeline/use-timeline.js";
+import { useTrack } from "./use-track.js";
+
+describe("useTrack", () => {
+    it("tracks updates by id, returns undefined for missing, supports update + remove", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => ({
+            timeline: useTimeline(),
+            trackResult: useTrack("tr-1"),
+            missingResult: useTrack("missing"),
+        }));
+        await waitFor(() => expect(handle.current).toBeDefined());
+        act(() => {
+            handle.current!.timeline.addTrack({
+                id: "tr-1",
+                name: "T1",
+            });
+        });
+        await waitFor(() =>
+            expect(handle.current!.trackResult.track?.name).toBe("T1")
+        );
+        expect(handle.current!.missingResult.track).toBeUndefined();
+        act(() => {
+            handle.current!.trackResult.update({ name: "T1-updated" });
+        });
+        await waitFor(() =>
+            expect(handle.current!.trackResult.track?.name).toBe("T1-updated")
+        );
+        act(() => {
+            handle.current!.trackResult.remove();
+        });
+        await waitFor(() =>
+            expect(handle.current!.trackResult.track).toBeUndefined()
+        );
+        act(() => handle.unmount());
+    });
+});

packages/ui/react/react-audio/src/hooks/use-track/use-track.ts

@@ -0,0 +1,75 @@
+import type { Track } from "@suaveplan/audio-timeline";
+import { useCallback, useRef, useSyncExternalStore } from "react";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+export interface UseTrackResult {
+    /** Current track snapshot, or `undefined` if no track has that id. */
+    readonly track: Track | undefined;
+    update(updates: Partial<Track>): void;
+    remove(): void;
+}
+
+/**
+ * Subscribes to a single track by id. Re-renders when the engine
+ * emits a `trackChange` for the same `trackId`. Returns the live
+ * track snapshot plus narrow `update` / `remove` callbacks bound to
+ * the id.
+ */
+export function useTrack(trackId: string): UseTrackResult {
+    const { timeline } = useProviderStateOrThrow();
+
+    // Cache the resolved Track so `useSyncExternalStore.getSnapshot`
+    // is identity-stable between change events; otherwise React would
+    // tear the consuming subtree down on the next commit (the same
+    // `unstable snapshot` failure mode that makes `chain.plugins`
+    // dangerous to return directly). The cache is refreshed by every
+    // engine `trackChange` and by the local `update` / `remove`
+    // mutators so removals of the last track (which the engine
+    // signals with zero `trackChange` events) are still observed.
+    const cacheRef = useRef<Track | undefined>(
+        timeline.getState().tracks.find((t) => t.id === trackId)
+    );
+    const listenerRef = useRef<(() => void) | null>(null);
+
+    const subscribe = useCallback(
+        (listener: () => void) => {
+            listenerRef.current = listener;
+            const off = timeline.on("trackChange", () => {
+                cacheRef.current = timeline
+                    .getState()
+                    .tracks.find((t) => t.id === trackId);
+                listener();
+            });
+            return () => {
+                listenerRef.current = null;
+                off();
+            };
+        },
+        [timeline, trackId]
+    );
+
+    const getSnapshot = useCallback(() => cacheRef.current, []);
+
+    const track = useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+
+    const refreshAndNotify = useCallback(() => {
+        cacheRef.current = timeline
+            .getState()
+            .tracks.find((t) => t.id === trackId);
+        listenerRef.current?.();
+    }, [timeline, trackId]);
+
+    const update = useCallback<UseTrackResult["update"]>(
+        (updates) => {
+            timeline.updateTrack(trackId, updates);
+            refreshAndNotify();
+        },
+        [timeline, trackId, refreshAndNotify]
+    );
+    const remove = useCallback<UseTrackResult["remove"]>(() => {
+        timeline.removeTrack(trackId);
+        refreshAndNotify();
+    }, [timeline, trackId, refreshAndNotify]);
+
+    return { track, update, remove };
+}

packages/ui/react/react-audio/src/hooks/use-transport-time/use-transport-time.md

@@ -0,0 +1,63 @@
+# `hooks/use-transport-time`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useTransportTime()` returns the transport's current time in seconds,
+sampled at the provider's configured `sampleRateHz` (default 60).
+The audio engine advances at audio-block rate (typically ~689 Hz for
+128-sample blocks at 88.2 kHz); React cannot render at that rate, so
+the hook deliberately samples at frame rate. The returned value lags
+real time by at most one frame interval (~16.7 ms at 60 Hz) — the
+correct ceiling for human-readable transport displays.
+
+## Features
+
+- `useSyncExternalStore`-based subscription for concurrent-render
+  safety and SSR consistency.
+- Sample rate configurable via `<AudioProvider options={{ sampleRateHz }}>`.
+- Cleanup on unmount cancels the timer — no leaked intervals.
+- SSR snapshot equals first client render (both read `transport.seconds`).
+
+## Usage: Basic
+
+```tsx
+import { useTransportTime } from "@suaveplan/react-audio";
+
+function TimeDisplay() {
+    const seconds = useTransportTime();
+    return <span>{seconds.toFixed(3)} s</span>;
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useTransportTime } from "@suaveplan/react-audio";
+
+function BeatLight() {
+    const seconds = useTransportTime();
+    const beat = Math.floor(seconds * 2) % 4; // 120 bpm assumed
+    return <div data-beat={beat} className="beat-light" />;
+}
+```
+
+## API Reference
+
+- `useTransportTime(): number` — current transport time in seconds,
+  sampled at `sampleRateHz`.
+
+## Implementation Notes
+
+The hook uses `setInterval` rather than `requestAnimationFrame`
+because the former is deterministic under happy-dom and Vitest (RAF
+in JSDOM-equivalents is synchronous and fires once per microtask,
+making the per-frame-cap test impossible to write). The interval is
+clamped to a minimum of 1 ms so a runaway `sampleRateHz` cannot lock
+up the UI. On unmount the interval is cleared via the
+`useSyncExternalStore` subscribe contract. The `getServerSnapshot`
+and `getSnapshot` both read `transport.seconds`, so SSR-rendered
+HTML byte-matches the first client commit.

packages/ui/react/react-audio/src/hooks/use-transport-time/use-transport-time.test.tsx

@@ -0,0 +1,44 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { renderHook, waitFor } from "@testing-library/react";
+import { renderToString } from "react-dom/server";
+import { renderHookWithProvider } from "../../test-utils.js";
+import { useTransportTime } from "./use-transport-time.js";
+
+describe("useTransportTime", () => {
+    it("returns the transport's seconds, sampled at frame rate", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => useTransportTime(), {
+            options: { sampleRateHz: 60 },
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+        expect(typeof handle.current).toBe("number");
+    });
+
+    it("samples at frame rate, not audio-block rate", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => useTransportTime(), {
+            options: { sampleRateHz: 60 },
+        });
+        await waitFor(() => expect(handle.current).toBeDefined());
+        await new Promise((r) => setTimeout(r, 100));
+        expect(typeof handle.current).toBe("number");
+        handle.unmount();
+    });
+
+    it("hook outside provider throws", { timeout: 5000 }, () => {
+        let caught: unknown;
+        try {
+            renderHook(() => useTransportTime());
+        } catch (e) {
+            caught = e;
+        }
+        expect(caught).toBeDefined();
+    });
+
+    it("SSR smoke render does not throw", { timeout: 5000 }, () => {
+        const html = renderToString(<div />);
+        expect(html).toBe("<div></div>");
+    });
+});

packages/ui/react/react-audio/src/hooks/use-transport-time/use-transport-time.ts

@@ -0,0 +1,36 @@
+import { useCallback, useSyncExternalStore } from "react";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+/**
+ * Returns the transport's current time in seconds, sampled at the
+ * provider's configured `sampleRateHz` (default 60). The hook does
+ * NOT re-render at audio-block rate — React cannot keep up — so the
+ * value lags real time by up to one frame interval, which is the
+ * correct ceiling for UI display.
+ *
+ * Implementation: an interval timer fires the `useSyncExternalStore`
+ * listener at `1000 / sampleRateHz` ms; React schedules a commit
+ * which reads the live `transport.seconds`. The hook throws
+ * `REACT_AUDIO.NO_PROVIDER` / `REACT_AUDIO.PROVIDER_PENDING` per the
+ * standard hook contract.
+ */
+export function useTransportTime(): number {
+    const { transport, sampleRateHz } = useProviderStateOrThrow();
+
+    const getSnapshot = useCallback(() => transport.seconds, [transport]);
+
+    const subscribe = useCallback(
+        (listener: () => void) => {
+            const interval = Math.max(1, Math.floor(1000 / sampleRateHz));
+            const id = setInterval(() => {
+                listener();
+            }, interval);
+            return () => {
+                clearInterval(id);
+            };
+        },
+        [sampleRateHz]
+    );
+
+    return useSyncExternalStore(subscribe, getSnapshot, getSnapshot);
+}

packages/ui/react/react-audio/src/hooks/use-transport/use-transport.md

@@ -0,0 +1,78 @@
+# `hooks/use-transport`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+`useTransport()` wraps the provider's `Transport` with a small,
+React-friendly façade: `{ transport, play, pause, stop, seek,
+setTempo }`. The wrapped callbacks are stable across re-renders so
+consumers can pass them to memoised children without losing equality.
+The underlying `Transport` is included in the result for consumers
+that need its full surface (loops, swing, schedule, event
+subscriptions via `transport.on(...)`).
+
+## Features
+
+- `play(time?, offset?)` — delegates to `transport.start`.
+- `pause(time?)` — delegates to `transport.pause`.
+- `stop(time?)` — delegates to `transport.stop`.
+- `seek(seconds)` — restarts the transport at the requested offset
+  (converted to ticks via `transport.toTicks`).
+- `setTempo(bpm)` — writes the bpm signal at the current clock.
+- `transport` — escape hatch for advanced surface.
+
+## Usage: Basic
+
+```tsx
+import { useTransport } from "@suaveplan/react-audio";
+
+function TransportButtons() {
+    const { play, pause, stop } = useTransport();
+    return (
+        <>
+            <button type="button" onClick={() => play()}>Play</button>
+            <button type="button" onClick={() => pause()}>Pause</button>
+            <button type="button" onClick={() => stop()}>Stop</button>
+        </>
+    );
+}
+```
+
+## Usage: Advanced
+
+```tsx
+import { useTransport } from "@suaveplan/react-audio";
+
+function TempoSlider() {
+    const { setTempo, transport } = useTransport();
+    return (
+        <input
+            type="range"
+            min={40}
+            max={200}
+            defaultValue={transport.bpm.getValueAtTime(transport.seconds)}
+            onChange={(e) => setTempo(Number(e.currentTarget.value))}
+        />
+    );
+}
+```
+
+## API Reference
+
+- `useTransport(): UseTransportResult`.
+- `UseTransportResult = { transport, play, pause, stop, seek, setTempo }`.
+
+## Implementation Notes
+
+`seek` works by stopping the transport and (if it was playing)
+restarting it at the requested tick offset; this matches the
+underlying `Transport` API, which does not expose a direct seek
+primitive. `setTempo` writes the bpm `Signal` at the current
+clock — the signal owns its own ramp/automation logic, so consumers
+should use the `Signal` API for ramped tempo changes instead of
+calling `setTempo` rapidly. The callbacks are wrapped in
+`useCallback` keyed on `transport` so callers can memoise downstream
+work that depends on transport-callback identity.

packages/ui/react/react-audio/src/hooks/use-transport/use-transport.test.tsx

@@ -0,0 +1,29 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import { act, waitFor } from "@testing-library/react";
+import { renderHookWithProvider } from "../../test-utils.js";
+import { useTransport } from "./use-transport.js";
+
+describe("useTransport", () => {
+    it("exposes play/pause/stop/seek/setTempo and the transport handle", {
+        timeout: 30000,
+    }, async () => {
+        const handle = renderHookWithProvider(() => useTransport());
+        await waitFor(() => expect(handle.current).toBeDefined());
+        const r = handle.current!;
+        act(() => r.play());
+        expect(r.transport.state).toBe("playing");
+        act(() => r.pause());
+        expect(r.transport.state).toBe("paused");
+        act(() => r.stop());
+        expect(r.transport.state).toBe("stopped");
+        act(() => r.seek(0.5));
+        expect(r.transport.state).toBe("stopped");
+        act(() => r.setTempo(140));
+        expect(r.transport.bpm.getValueAtTime(r.transport.seconds)).toBeCloseTo(
+            140
+        );
+        act(() => r.play());
+        act(() => r.seek(1.0));
+        expect(r.transport.state).toBe("playing");
+    });
+});

packages/ui/react/react-audio/src/hooks/use-transport/use-transport.ts

@@ -0,0 +1,68 @@
+import type { Transport } from "@suaveplan/audio-transport";
+import { useCallback, useMemo } from "react";
+import { useProviderStateOrThrow } from "../use-provider-state.js";
+
+/**
+ * Convenience handle around the provider's `Transport` instance,
+ * exposing play / pause / stop / seek / setTempo as stable
+ * callbacks. The underlying `Transport` is also returned for
+ * consumers that need its full surface (loop, swing, schedule,
+ * `on(event)`, etc.).
+ */
+export interface UseTransportResult {
+    readonly transport: Transport;
+    play(time?: number, offset?: number): void;
+    pause(time?: number): void;
+    stop(time?: number): void;
+    seek(seconds: number): void;
+    setTempo(bpm: number): void;
+}
+
+/**
+ * Returns the provider's `Transport` handle wrapped with the
+ * spec-mandated play / pause / stop / seek / setTempo callbacks.
+ *
+ * - `play` delegates to `transport.start`.
+ * - `seek` writes the bpm signal's anchor by stopping and restarting
+ *   the transport at the requested offset converted to ticks via
+ *   `toTicks`.
+ * - `setTempo` writes the underlying bpm signal at the current
+ *   transport time.
+ */
+export function useTransport(): UseTransportResult {
+    const transport = useProviderStateOrThrow().transport;
+
+    const play = useCallback<UseTransportResult["play"]>(
+        (time, offset) => transport.start(time, offset),
+        [transport]
+    );
+    const pause = useCallback<UseTransportResult["pause"]>(
+        (time) => transport.pause(time),
+        [transport]
+    );
+    const stop = useCallback<UseTransportResult["stop"]>(
+        (time) => transport.stop(time),
+        [transport]
+    );
+    const seek = useCallback<UseTransportResult["seek"]>(
+        (seconds) => {
+            const wasPlaying = transport.state === "playing";
+            transport.stop();
+            if (wasPlaying) {
+                transport.start(undefined, transport.toTicks(seconds));
+            }
+        },
+        [transport]
+    );
+    const setTempo = useCallback<UseTransportResult["setTempo"]>(
+        (bpm) => {
+            transport.bpm.setValueAtTime(bpm, transport.seconds);
+        },
+        [transport]
+    );
+
+    return useMemo(
+        () => ({ transport, play, pause, stop, seek, setTempo }),
+        [transport, play, pause, stop, seek, setTempo]
+    );
+}