feat(audio): rebuild playback + visualization on resident daemon and PCM cache

Two fragility points, rebuilt at the root:

Playback: one resident mpv daemon (--idle --keep-open) with a persistent
IPC connection and observe_property state instead of spawn-per-episode and
connect-per-poll. Play/pause/seek are sub-ms commands; time-pos pushes at
~20Hz; external pauses arrive as events. Boot session restore preloads the
episode paused (loadfile + paused time-pos seek, since mpv defers --start
stream work until playback) so first Play is a ~400ms unpause instead of a
cold 4.3s open+seek. Load ops are mutex-serialized so a raced preload
cannot clobber an in-flight play.

Data throttling: mpv demuxer cache capped (cache-secs=90, max-bytes=40MiB)
so a paused preload no longer races to its 150MiB default (measured
45.7MB/12s); decoder paced at 4x realtime instead of 84x so playback start
isn't starved by the visualizer ripping the whole episode.

Visualization: replaced the paced-ring reader (AudioStreamReader) with a
position-indexed PCM cache (audio-pcm-cache). ffmpeg fills a cache indexed
by absolute playback time; reads at the player position are always exact.
Pause freezes the render loop, resume re-arms it — no coverage guessing,
no clamped-buffer freeze (the pause->broken-waveform->freeze bug). Seeks
and speed changes need no pipeline restarts; uncovered reads return empty
and the last frame holds.

Cover art: persistent per-URL disk cache under XDG cache dir; play() no
longer awaits a curl subprocess (up to 8s). Cache hit = one stat; misses
apply late via mpv video-add.

Test suite: 161 pass. New tests pin the position-index contract (sample-
exact window reads, hold-on-uncovered, pause-keeps-cache, seek segments),
the daemon contract (play/pause/resume/seek/stop, preload fast path,
EOF->replay), and cover cache/single-flight/404.

src/hooks/useAudio.ts

@@ -13,8 +13,11 @@
  */
 
 import { onCleanup } from "solid-js";
-import { unlinkSync } from "fs";
+import {
-import { fetchCoverArt, coverTempPath } from "../utils/cover-art";
+	cachedCoverPath,
+	fetchCoverArt,
+	prefetchCoverArt,
+} from "../utils/cover-art";
 import {
 	createAudioBackend,
 	detectPlayers,
@@ -158,11 +161,6 @@ function registerExitTeardown(): void {
 		} catch {
 			/* best-effort at exit */
 		}
-		try {
-			unlinkSync(coverTempPath());
-		} catch {
-			/* best-effort at exit */
-		}
 	};
 	process.on("exit", teardown);
 	for (const sig of ["SIGINT", "SIGTERM", "SIGHUP"] as const) {
@@ -231,6 +229,15 @@ function startPolling(): void {
 		try {
 			pollCount++;
 			if (isPlaying()) {
+				// Track ended (eof-reached observed) or process died. Check
+				// BEFORE pause reconciliation: mpv keeps the file open at EOF
+				// and reports pause=true there, which would otherwise be
+				// mistaken for an external pause and never finalize.
+				if (!backend.isPlaying()) {
+					finalizeTrackEnd();
+					return;
+				}
+
 				// mpv can pause itself outside PodTUI. Reconcile instead of
 				// staying stuck on "playing" with a frozen waveform
 				// (getPosition would just re-read the same frozen time-pos).
@@ -256,11 +263,6 @@ function startPolling(): void {
 						media.setPosition(pos);
 					}
 				}
-
-				// Check if backend stopped playing (track ended)
-				if (!backend.isPlaying()) {
-					finalizeTrackEnd();
-				}
 			} else if (pollCount % PAUSE_WATCH_TICKS === 0) {
 				// Paused — watch for playback restarted from outside (AirPods,
 				// lock-screen/media-center play). Only while the player is
@@ -314,9 +316,12 @@ async function play(episode: Episode): Promise<void> {
 		const feedStore = useFeedStore();
 		const feed = feedStore.feeds().find((f) => f.podcast.id === episode.podcastId);
 		const podcastTitle = feed?.customName || feed?.podcast.title || "";
-		const coverArtPath = feed?.podcast.coverUrl
+		// Cover art must NEVER gate playback (it was a curl subprocess blocking
-			? await fetchCoverArt(feed.podcast.coverUrl)
+		// play() by up to 8s). Serve the disk-cached file synchronously when it
-			: null;
+		// exists; on a miss, start playback bare and fetch in the background —
+		// the backend applies late art at runtime (mpv video-add).
+		const coverUrl = feed?.podcast.coverUrl;
+		const coverArtPath = coverUrl ? cachedCoverPath(coverUrl) : null;
 
 		// Resume from saved progress if available and not completed
 		const savedProgress = progressStore.get(episode.id);
@@ -333,6 +338,16 @@ async function play(episode: Episode): Promise<void> {
 			coverArtPath: coverArtPath ?? undefined,
 		});
 
+		if (coverUrl && !coverArtPath) {
+			fetchCoverArt(coverUrl)
+				.then((path) => {
+					if (path && currentEpisode()?.id === episode.id) {
+						b.addCoverArt(path).catch(() => {});
+					}
+				})
+				.catch(() => {});
+		}
+
 		setCurrentEpisode(episode);
 		setIsPlaying(true);
 		setPosition(startPos);
@@ -404,6 +419,29 @@ async function load(episode: Episode): Promise<void> {
 	media.setPlaybackState(false);
 	if (pos > 0) media.setPosition(pos);
 
+	// Preload the episode into the backend PAUSED: mpv opens the stream and
+	// fills its demuxer cache while parked, so the user's first Play flips
+	// `pause` off instead of paying the ~2s stream-open cold. Fire-and-forget
+	// — a failed preload just makes the first play take the cold path.
+	if (episode.audioUrl && backend) {
+		const coverUrl = feed?.podcast.coverUrl;
+		if (coverUrl) prefetchCoverArt(coverUrl);
+		const backendSnap = backend;
+		backendSnap
+			.preload(episode.audioUrl, {
+				volume: volume(),
+				speed: storeSpeed || speed(),
+				startPosition: pos > 0 ? pos : undefined,
+				mediaTitle: podcastTitle
+					? `${podcastTitle} — ${episode.title}`
+					: episode.title,
+				coverArtPath: coverUrl
+					? (cachedCoverPath(coverUrl) ?? undefined)
+					: undefined,
+			})
+			.catch(() => {});
+	}
+
 	saveLastPlayerToFile({ episodeId: episode.id, timestamp: new Date() });
 }
 
@@ -564,9 +602,8 @@ async function switchBackend(name: BackendName): Promise<void> {
 				.feeds()
 				.find((f) => f.podcast.id === ep.podcastId);
 			const podcastTitle = feed?.customName || feed?.podcast.title || "";
-			const coverArtPath = feed?.podcast.coverUrl
+			const coverUrl = feed?.podcast.coverUrl;
-				? await fetchCoverArt(feed.podcast.coverUrl)
+			const coverArtPath = coverUrl ? cachedCoverPath(coverUrl) : null;
-				: null;
 			await backend.play(ep.audioUrl, {
 				startPosition: pos,
 				volume: vol,

src/stores/visualizer.ts

@@ -2,20 +2,29 @@
  * visualizer-store — module-level singleton owning the realtime waveform
  * pipeline (ffmpeg decode + cavacore FFT), shared across PlayerPage mounts.
  *
- * The pipeline lives here rather than in the Player page component so it can
+ * Pipeline shape (see utils/audio-pcm-cache.ts for the rationale):
- * outlive the page: Shell unmounts a tab's page the moment the tab loses
+ * an ffmpeg process decodes the episode at full speed into a
- * focus, which would otherwise kill the ffmpeg decode + FFT loop instantly.
+ * position-indexed PCM cache; the render loop reads the window ending at
- * Instead the store keeps the visualization warm for UNLOAD_DELAY_MS after
+ * the player's current position from that cache. Because reads are
- * the Player tab stops being focused, then tears it down (kills ffmpeg,
+ * indexed by playback time, PAUSE/RESUME/SEEK/SPEED need no pipeline
- * destroys the cava plan). Returning to the tab within the delay resumes
+ * choreography at all — and cannot desync:
- * seamlessly; after an unload, regaining focus restarts the pipeline from
- * the current playback position.
  *
- * The store subscribes to the module-level playback signals in
+ * - Pause: stop the render loop and the decode pass; the PCM cache stays
- * `utils/audio-signals.ts` (`audioPlaybackSignals`), so it reacts to
+ *   resident. Bars freeze on the last rendered frame.
- * play/pause/seek/speed even while no Player page is mounted. `focused` is
+ * - Resume: re-arm the render loop — bars render instantly from the cache
- * fed by PlayerPage (mounted ⇔ Player tab visible), `barCount` by
+ *   — and continue the tail decode in the background. No cold start, no
- * RealtimeWaveform (terminal width).
+ *   coverage guessing, no clamped-buffer freeze (the old bug: resume
+ *   re-armed the loop over a DEAD ffmpeg and the bars exhausted the ring
+ *   buffer, then froze on a repeated stale window forever).
+ * - Seek into decoded audio: nothing to do. Seek into a hole: kick off a
+ *   decode segment there; the last frame holds until data arrives.
+ * - Speed changes: nothing. The cache is position-indexed raw PCM.
+ *
+ * Focus lifecycle: Shell unmounts a tab's page when it loses focus, but the
+ * pipeline outlives the page so playback keeps visualizing; UNLOAD_DELAY_MS
+ * after the Player tab stops being focused it tears down. Reads outside
+ * decoded coverage return empty — the renderer simply holds the last frame
+ * until the decode frontier arrives.
  */
 
 import {
@@ -30,7 +39,7 @@ import {
 	type CavaCore,
 	type CavaCoreConfig,
 } from "@/utils/cavacore";
-import { AudioStreamReader } from "@/utils/audio-stream-reader";
+import { EpisodePcmCache, PCM_SAMPLE_RATE } from "@/utils/audio-pcm-cache";
 import { createBarScaler } from "@/utils/bar-mapping";
 import { audioPlaybackSignals } from "@/utils/audio-signals";
 import { useAppStore } from "@/stores/app";
@@ -83,7 +92,10 @@ function createVisualizerStore(): VisualizerStore {
 	const scaler = createBarScaler();
 
 	let cava: CavaCore | null = null;
-	let reader: AudioStreamReader | null = null;
+	// Position-indexed PCM cache for the current episode. Kept across
+	// pause/resume (segments survive; only the ffmpeg pass is killed) and
+	// dropped only on episode change, stop, disable, or unload.
+	let pcm: EpisodePcmCache | null = null;
 	let frameTimer: ReturnType<typeof setInterval> | null = null;
 	let sampleBuffer: Float64Array | null = null;
 	let unloadTimer: ReturnType<typeof setTimeout> | null = null;
@@ -91,7 +103,6 @@ function createVisualizerStore(): VisualizerStore {
 	// What the running pipeline was started with — lets the playback effect
 	// tell "nothing changed, stay warm" from "must restart".
 	let activeUrl = "";
-	let activeSpeed = 1;
 	let activeBars = 64;
 
 	// ── Lifecycle helpers ──────────────────────────────────────────────
@@ -139,7 +150,7 @@ function createVisualizerStore(): VisualizerStore {
 
 	// ── Start/stop the visualization pipeline ──────────────────────────
 
-	const startVisualization = (url: string, position: number, speed: number) => {
+	const startVisualization = (url: string, position: number) => {
 		stopVisualization();
 
 		if (!url || !initCava() || !cava) return;
@@ -152,7 +163,7 @@ function createVisualizerStore(): VisualizerStore {
 		const viz = useAppStore().state().settings.visualizer;
 		const config: CavaCoreConfig = {
 			bars: barCount(),
-			sampleRate: 44100,
+			sampleRate: PCM_SAMPLE_RATE,
 			channels: 1,
 			noiseReduction: viz.noiseReduction,
 			lowCutOff: viz.lowCutOff,
@@ -164,32 +175,29 @@ function createVisualizerStore(): VisualizerStore {
 		// Pre-warm the FFT window: libcavacore's window is malloc'd
 		// uninitialized, so the first real frame would FFT garbage and
 		// render full-scale bars. One zero frame the size of the whole
-		// input buffer clears it (at 44.1kHz mono the window is 8192
+		// input buffer clears it.
-		// samples — FFTbassbufferSize × channels; a 512-sample frame would
-		// leave the tail garbage).
 		cava.execute(new Float64Array(8192));
 
 		// Pre-allocate sample read buffer
 		sampleBuffer = new Float64Array(SAMPLES_PER_FRAME);
 
-		// Start ffmpeg decode stream (reuse reader if same URL, else create new)
+		// PCM cache per episode (reuse when the episode is unchanged)
-		if (!reader || reader.url !== url) {
+		if (!pcm || pcm.url !== url) {
-			if (reader) reader.stop();
+			if (pcm) pcm.stop();
-			reader = new AudioStreamReader({ url });
+			pcm = new EpisodePcmCache({ url });
 		}
-		reader.start(position, speed);
+		// Decode from 1s before the position so the window ENDING at the
+		// position is covered as soon as the first PCM lands.
+		pcm.startDecode(Math.max(0, position - 1));
 
 		// Seed the smooth position clock with the start position. Without
 		// this, a fresh play at position 0 would sample the window ending at
-		// exactly 0 — a 1-sample slice the reader can never fill — so the
+		// exactly 0 — a 1-sample slice — so bars would be starved until the
-		// bars would be starved until the first mpv poll advanced the
+		// first mpv poll advanced the position clock.
-		// position clock. Seeding makes the interpolated target advance
-		// immediately, so bars render as soon as ffmpeg has any audio.
 		lastPolledPosition = position;
 		lastPolledAt = performance.now();
 
 		activeUrl = url;
-		activeSpeed = speed;
 		activeBars = barCount();
 		setIsLoading(true);
 		frameTimer = setInterval(renderFrame, FRAME_INTERVAL);
@@ -201,9 +209,10 @@ function createVisualizerStore(): VisualizerStore {
 			clearInterval(frameTimer);
 			frameTimer = null;
 		}
-		if (reader) {
+		if (pcm) {
-			reader.stop();
+			pcm.stop();
-			// Don't null reader — we reuse it across start/stop cycles
+			// Keep the (now cache-less, url-tagged) object: a re-start of the
+			// same episode reuses it; segments re-decode in seconds at 80x.
 		}
 		if (cava?.isReady) {
 			cava.destroy();
@@ -212,17 +221,59 @@ function createVisualizerStore(): VisualizerStore {
 		setIsLoading(false);
 	};
 
+	// ── Pause: freeze the loop, keep the cache ──────────────────────────
+	//
+	// The render loop stops (bars hold their last frame) and the ffmpeg
+	// pass dies (no background CPU), but the decoded PCM stays: resume
+	// serves it instantly.
+
+	const suspendVisualization = () => {
+		clearUnloadTimer();
+		if (frameTimer) {
+			clearInterval(frameTimer);
+			frameTimer = null;
+		}
+		if (pcm) pcm.pauseDecode();
+		// Cava plan + sampleBuffer stay alive — cheap to reuse on resume.
+		// Clear the loading spinner: if the pipeline never produced bars
+		// (still cold-starting when paused), the component should fall back
+		// to the placeholder, not freeze on a spinner.
+		setIsLoading(false);
+	};
+
+	// ── Resume: re-arm the render loop, top up the cache ───────────────
+	//
+	// Returns true if the pipeline resumed, false if there was nothing to
+	// resume (no prior pipeline).
+
+	const resumeVisualization = (): boolean => {
+		// Already running — nothing to do.
+		if (frameTimer !== null) return true;
+		if (!pcm || !cava?.isReady || !sampleBuffer) return false;
+
+		const pos = untrack(audioPlaybackSignals.position);
+
+		// Bars come from the cache on the next frame tick (~33ms) whenever
+		// the position is covered; any gap (uncached region) restarts the
+		// decode pass in the background with the last frame holding.
+		pcm.ensureDecodeAround(pos);
+
+		lastPolledPosition = pos;
+		lastPolledAt = performance.now();
+		frameTimer = setInterval(renderFrame, FRAME_INTERVAL);
+		return true;
+	};
+
 	// ── Render loop (called at ~30fps) ─────────────────────────────────
 
 	const renderFrame = () => {
-		if (!cava?.isReady || !reader?.running || !sampleBuffer) return;
+		if (!cava?.isReady || !sampleBuffer || !pcm) return;
 
-		// Sample the FFT window at the player's position, not the decode
+		// Sample the FFT window at the player's position. Outside decoded
-		// head — the reader decodes independently (paced at the player's
+		// coverage (decode cold start, seek into a hole) the read is empty
-		// clock rate with a LEAD_SECONDS burst head start) and only the
+		// and the LAST FRAME simply holds — never clamped/repeated junk.
-		// position clock ties the bars to what's actually playing.
 		const target = smoothPosition();
-		const count = reader.read(sampleBuffer, target);
+		const count = pcm.readWindow(sampleBuffer, target);
 		// Never feed a partial FFT window to cava.
 		if (count < sampleBuffer.length) return;
 
@@ -235,44 +286,53 @@ function createVisualizerStore(): VisualizerStore {
 
 	// ── Playback subscription ──────────────────────────────────────────
 	//
-	// Keeps the pipeline matched to playback. `focused` is a dep so focus
+	// Keeps the pipeline matched to playback. Pause suspends (render loop +
-	// regain re-evaluates (and can restart an unloaded pipeline), but the
+	// decode pass die, cache survives) so resume is instant. Stop/track-end/
-	// guard below makes a focus flip on an already-correct warm pipeline a
+	// disable fully tears down. `focused` is a dep so focus regain
-	// no-op — no churn when flipping back to the Player tab within the
+	// re-evaluates; the guards make a focus flip on an already-correct warm
-	// unload delay. A real change (url/speed/barCount, stop/start, or a
+	// pipeline a no-op. Speed is deliberately NOT a dep — the PCM cache is
-	// stale pipeline after an unload) restarts from the current position.
+	// position-indexed, so playback-rate changes need no pipeline restart.
 
 	createEffect(
 		on(
 			[
 				audioPlaybackSignals.isPlaying,
 				() => audioPlaybackSignals.currentEpisode()?.audioUrl ?? "",
-				audioPlaybackSignals.speed,
 				barCount,
 				focused,
 				() => useAppStore().state().settings.visualizer.enabled,
 			],
-			([playing, url, speed, , , enabled]) => {
+			([playing, url, , , enabled]) => {
-				if (!playing || !url || !enabled) {
+				if (!url || !enabled) {
 					stopVisualization();
 					return;
 				}
-				// Warm and already correct — nothing to do (e.g. focus
+				if (!playing) {
-				// regained within the unload delay).
+					// Pause: freeze the loop, keep the cache. Only if the
+					// pipeline is actually running — otherwise no-op.
+					if (frameTimer !== null) suspendVisualization();
+					return;
+				}
+
+				// Playing — try a fast resume first. If it succeeds and the
+				// pipeline matches, done.
 				if (
-					frameTimer !== null &&
+					frameTimer === null &&
+					pcm &&
+					cava?.isReady &&
 					url === activeUrl &&
-					speed === activeSpeed &&
 					barCount() === activeBars
 				) {
+					if (resumeVisualization()) return;
+				}
+
+				// Warm and already correct — nothing to do (e.g. focus
+				// regained within the unload delay while still playing).
+				if (frameTimer !== null && url === activeUrl && barCount() === activeBars) {
 					return;
 				}
 				if (!focused()) return; // playing away: stay warm; unload timer decides
-				startVisualization(
+				startVisualization(url, untrack(audioPlaybackSignals.position));
-					url,
-					untrack(audioPlaybackSignals.position),
-					speed,
-				);
 			},
 		),
 	);
@@ -296,7 +356,6 @@ function createVisualizerStore(): VisualizerStore {
 					startVisualization(
 						audioPlaybackSignals.currentEpisode()!.audioUrl,
 						untrack(audioPlaybackSignals.position),
-						audioPlaybackSignals.speed() ?? 1,
 					);
 				}
 			} else if (frameTimer !== null) {
@@ -308,17 +367,17 @@ function createVisualizerStore(): VisualizerStore {
 		}),
 	);
 
-	// ── Seek detection: lightweight effect for position jumps ──────────
+	// ── Seek detection: jump coverage, not pipeline restarts ───────────
 	//
-	// Watches position and restarts the reader (not the whole pipeline)
+	// Watches position for significant jumps (>2s = user seek). Decoded
-	// only on significant jumps (>2s), which indicate a user seek.
+	// audio at the new position is served instantly with zero action; a
-	// This is intentionally a separate effect — it should NOT trigger a
+	// jump into an undecoded hole kicks a background segment decode there
-	// full pipeline restart, just restart the ffmpeg stream at the new pos.
+	// while the last frame holds.
 
 	let lastSyncPosition = 0;
 	createEffect(
 		on(audioPlaybackSignals.position, (pos) => {
-			if (!audioPlaybackSignals.isPlaying() || !reader?.running) {
+			if (!audioPlaybackSignals.isPlaying() || !pcm) {
 				lastSyncPosition = pos;
 				return;
 			}
@@ -327,10 +386,21 @@ function createVisualizerStore(): VisualizerStore {
 			lastSyncPosition = pos;
 
 			if (delta > 2) {
-				reader.restart(pos, audioPlaybackSignals.speed() ?? 1);
+				pcm.ensureDecodeAround(pos);
 			}
 		}),
 	);
+	// ── Process-exit teardown ──────────────────────────────────────────
+	//
+	// The pipeline lives in a detached createRoot that is never disposed,
+	// so Solid's onCleanup never runs. `q`/`:quit` call process.exit(0)
+	// (bypassing onCleanup); SIGINT/TERM/HUP are caught by useAudio's
+	// handler. This handler runs synchronously on `exit` and kills the
+	// ffmpeg child + destroys the cava plan so they don't outlive the host.
+	// Without it, a warm pipeline leaks an orphaned ffmpeg process on quit.
+	process.on("exit", () => {
+		stopVisualization();
+	});
 
 	return {
 		// state

src/utils/audio-pcm-cache.ts

@@ -0,0 +1,363 @@
+/**
+ * Position-indexed PCM cache for visualization.
+ *
+ * One ffmpeg process decodes the episode's audio at 4x realtime (with an
+ * 8s initial burst — fast enough to serve bars and seeks instantly, throttled
+ * enough that a remote episode isn't ripped at 84x while mpv is trying to
+ * start playback) into an in-memory cache indexed by ABSOLUTE playback time.
+ * The renderer then reads the PCM
+ * window ending at the player's current position with zero sync machinery:
+ * there is no pacing (-readrate), no lead-burst, no decode-head/player
+ * drift math, no ring wrap, and nothing that knows or cares about pause,
+ * resume, seek, or playback speed — those all collapse to "read at a
+ * different position in the cache".
+ *
+ * Pause/resume contract (the failure mode of the old design):
+ * - pauseDecode() kills ffmpeg but KEEPS the cache. Resume reads from it
+ *   instantly and resumes the tail decode in the background.
+ * - Reads outside decoded coverage (startup, seek into an undecoded hole)
+ *   return 0 — the renderer HOLDS the last rendered frame rather than
+ *   freezing on a clamped buffer or decaying into junk bars.
+ *
+ * Seeks into undecoded territory start a fresh SEGMENT (a second decode
+ * pass over just that region) — earlier segments stay valid, mp3 decode of
+ * the same file is deterministic so abutting segments agree.
+ *
+ * Memory: 22050 Hz mono s16 ≈ 44 KB/s ≈ 2.6 MB/min (~80 MB per 30 min),
+ * freed on stop(). 22050 Hz covers Nyquist 11 kHz, above the default 10 kHz
+ * high-cutoff of the visualizer's FFT config.
+ *
+ * Downloads via ffmpeg's own http stack with reconnect flags, matching the
+ * old reader; local files skip them (ffmpeg rejects http-only options for
+ * file inputs).
+ */
+
+import type { Subprocess } from "bun";
+
+/** PCM output format constants */
+export const PCM_SAMPLE_RATE = 22050;
+const BYTES_PER_SAMPLE = 2; // s16le
+
+/** Initial segment capacity: 4 Mi samples ≈ 190 s of audio (8 MB). */
+const INITIAL_CAPACITY_SAMPLES = 4 * 1024 * 1024;
+
+/**
+ * Monotonically increasing generation counter.
+ * Each startDecode() increments this; the read loop checks it to know
+ * if it's been superseded and should bail out.
+ */
+let globalGeneration = 0;
+
+interface Segment {
+	/** Playback seconds where this segment's first sample sits. */
+	baseSec: number;
+	/** Sample buffer; capacity >= written, doubled on overflow. */
+	samples: Int16Array;
+	/** Samples written so far (== decoded length of the segment). */
+	written: number;
+	/** ffmpeg reached stream EOF while writing this segment — nothing more
+	 *  will ever arrive after its end. */
+	finished: boolean;
+}
+
+export interface EpisodePcmCacheOptions {
+	/** Audio URL or file path to decode */
+	url: string;
+	/** Sample rate (default: 22050) */
+	sampleRate?: number;
+}
+
+export class EpisodePcmCache {
+	private proc: Subprocess | null = null;
+	private segments: Segment[] = [];
+	private generation = 0;
+	private _decoding = false;
+	/** Base offset (playback seconds) of the running decode pass; null when idle. */
+	private activeBaseSec: number | null = null;
+	readonly url: string;
+	readonly sampleRate: number;
+
+	constructor(options: EpisodePcmCacheOptions) {
+		this.url = options.url;
+		this.sampleRate = options.sampleRate ?? PCM_SAMPLE_RATE;
+	}
+
+	/** Whether an ffmpeg decode pass is currently running. */
+	get decoding(): boolean {
+		return this._decoding;
+	}
+
+	/** End (playback seconds) of the furthest-decoded segment. */
+	get coverageEndSec(): number {
+		let end = 0;
+		for (const seg of this.segments) {
+			const segEnd = seg.baseSec + seg.written / this.sampleRate;
+			if (segEnd > end) end = segEnd;
+		}
+		return end;
+	}
+
+	/** Whether the furthest segment finished at stream EOF. */
+	get decodeFinished(): boolean {
+		let maxEnd = -1;
+		let finished = false;
+		for (const seg of this.segments) {
+			const segEnd = seg.baseSec + seg.written / this.sampleRate;
+			if (segEnd > maxEnd) {
+				maxEnd = segEnd;
+				finished = seg.finished;
+			}
+		}
+		return finished;
+	}
+
+	/**
+	 * Start decoding at `fromSec` of playback time into a fresh segment.
+	 * Kills any in-flight pass first; existing segments stay readable.
+	 */
+	startDecode(fromSec: number): void {
+		this.killProcess();
+
+		if (!Bun.which("ffmpeg")) {
+			throw new Error("ffmpeg not found — required for audio visualization");
+		}
+
+		this.generation = ++globalGeneration;
+		const myGeneration = this.generation;
+
+		const segment: Segment = {
+			baseSec: Math.max(0, fromSec),
+			samples: new Int16Array(INITIAL_CAPACITY_SAMPLES),
+			written: 0,
+			finished: false,
+		};
+		this.segments.push(segment);
+
+		const args = ["ffmpeg", "-loglevel", "quiet"];
+
+		// Pace the decode at 4x realtime (with an 8s initial burst) instead of
+		// flat-out: unthrottled decode measures ~84x realtime, which pulls the
+		// ENTIRE episode from the network within the first minute of playback
+		// (~160MB/hr) and starves mpv's own buffering right at startup. 4x
+		// still fills the cache 4x faster than playback consumes it, lands a
+		// 75-min episode in ~19 min of background work, and the burst makes
+		// the first bars available immediately.
+		args.push("-readrate", "4", "-readrate_initial_burst", "8");
+
+		// `-reconnect*` are http-protocol options: ffmpeg rejects them at
+		// input-open when the input is a local file, killing the process
+		// before any PCM is produced. Only pass them for network URLs.
+		if (/^https?:\/\//i.test(this.url)) {
+			args.push(
+				"-reconnect",
+				"1",
+				"-reconnect_streamed",
+				"1",
+				"-reconnect_delay_max",
+				"5",
+			);
+		}
+
+		// Seek before input for network efficiency (container-level skip is
+		// near-instant for mp3/aac; no pre-position decode burn).
+		if (fromSec > 0) {
+			args.push("-ss", String(Math.max(0, fromSec)));
+		}
+
+		args.push(
+			"-i",
+			this.url,
+			"-ac",
+			"1",
+			"-ar",
+			String(this.sampleRate),
+			"-f",
+			"s16le",
+			"-acodec",
+			"pcm_s16le",
+			"-",
+		);
+
+		this.proc = Bun.spawn(args, {
+			stdout: "pipe",
+			stderr: "ignore",
+			stdin: "ignore",
+		});
+		this._decoding = true;
+		this.activeBaseSec = segment.baseSec;
+		this.readLoop(myGeneration, segment);
+
+		this.proc.exited
+			.then((code) => {
+				if (this.generation === myGeneration) {
+					this._decoding = false;
+					this.activeBaseSec = null;
+					// Exit 0 == decoded to stream EOF.
+					if (code === 0) segment.finished = true;
+				}
+			})
+			.catch(() => {
+				if (this.generation === myGeneration) {
+					this._decoding = false;
+					this.activeBaseSec = null;
+				}
+			});
+	}
+
+	/**
+	 * Whether `sec` of playback time has decoded PCM on hand.
+	 */
+	covers(sec: number): boolean {
+		const idx = Math.round(sec * this.sampleRate);
+		for (const seg of this.segments) {
+			const base = Math.round(seg.baseSec * this.sampleRate);
+			if (idx >= base && idx < base + seg.written) return true;
+		}
+		return false;
+	}
+
+	/**
+	 * Make sure decode is progressing toward `sec`: no-op while a pass is
+	 * running or the episode is fully decoded; otherwise resumes the tail
+	 * decode from the frontier (when `sec` is inside coverage) or starts a
+	 * new segment at `sec` (seek into a hole / resume past cached audio).
+	 */
+	ensureDecodeAround(sec: number): void {
+		if (this._decoding) {
+			// A decode pass fills monotonically FORWARD from its base. Only a
+			// target at/after the active base is eventually covered by it —
+			// a target BEHIND the base (seek into an undecoded hole ahead of
+			// the active pass) never is: kill the pass and restart at sec.
+			if (this.activeBaseSec !== null && sec >= this.activeBaseSec) return;
+			this.startDecode(Math.max(0, sec));
+			return;
+		}
+		if (this.covers(sec)) {
+			// Covered here: continue the tail so the cache keeps filling
+			// past the position (unless the whole episode is decoded).
+			if (this.decodeFinished) return;
+			this.startDecode(this.coverageEndSec > sec ? this.coverageEndSec : sec);
+			return;
+		}
+		// Seek into an undecoded region: start a fresh segment there.
+		this.startDecode(Math.max(0, sec));
+	}
+
+	/**
+	 * Read the PCM window ENDING at `atSec` of playback into `out`
+	 * (Int16 magnitudes widened to f64, the scale cavacore expects).
+	 *
+	 * Returns the number of samples written: `out.length` on a full hit, 0
+	 * when the window is not (fully) decoded yet — the caller HOLDS the
+	 * last rendered frame instead of rendering partial/stale data.
+	 */
+	readWindow(out: Float64Array, atSec: number): number {
+		if (out.length === 0) return 0;
+		const endIdx = Math.round(atSec * this.sampleRate);
+		const startIdx = endIdx - out.length + 1;
+		for (const seg of this.segments) {
+			const base = Math.round(seg.baseSec * this.sampleRate);
+			if (startIdx < base || endIdx >= base + seg.written) continue;
+			const rel = startIdx - base;
+			const src = seg.samples;
+			for (let i = 0; i < out.length; i++) {
+				out[i] = src[rel + i];
+			}
+			return out.length;
+		}
+		return 0;
+	}
+
+	/**
+	 * Pause contract: kill the ffmpeg pass but KEEP every decoded segment.
+	 * Resume later serves bars from the cache instantly.
+	 */
+	pauseDecode(): void {
+		this.generation = ++globalGeneration;
+		this._decoding = false;
+		this.activeBaseSec = null;
+		this.killProcess();
+	}
+
+	/** Kill the decode pass AND drop all cached audio. */
+	stop(): void {
+		this.pauseDecode();
+		this.segments = [];
+	}
+
+	/** Kill the ffmpeg process without touching generation/state. */
+	private killProcess(): void {
+		if (this.proc) {
+			try {
+				this.proc.kill();
+			} catch {
+				/* ignore */
+			}
+			this.proc = null;
+		}
+	}
+
+	/** Internal: continuously reads stdout from ffmpeg and appends samples
+	 *  to the segment at their absolute playback-time offsets. */
+	private async readLoop(myGeneration: number, segment: Segment): Promise<void> {
+		const stdout = this.proc?.stdout;
+		if (!stdout || typeof stdout === "number") return;
+
+		const reader = (stdout as ReadableStream<Uint8Array>).getReader();
+		// s16 sample pairs can straddle pipe chunk boundaries: carry a lone
+		// trailing byte into the next chunk (dropping it would byte-flip
+		// every sample that follows).
+		let carry: number | null = null;
+		try {
+			while (this.generation === myGeneration) {
+				const { done, value } = await reader.read();
+				if (done || this.generation !== myGeneration) break;
+				if (!value || value.byteLength === 0) continue;
+
+				let view: Uint8Array = value;
+				if (carry !== null) {
+					const merged = new Uint8Array(1 + value.byteLength);
+					merged[0] = carry;
+					merged.set(value, 1);
+					view = merged;
+					carry = null;
+				}
+				if (view.byteLength % BYTES_PER_SAMPLE !== 0) {
+					carry = view[view.byteLength - 1];
+					view = view.subarray(0, view.byteLength - 1);
+				}
+
+				const sampleCount = view.byteLength / BYTES_PER_SAMPLE;
+				if (sampleCount === 0) continue;
+
+				if (segment.written + sampleCount > segment.samples.length) {
+					const grown = new Int16Array(
+						Math.max(
+							segment.samples.length * 2,
+							segment.written + sampleCount,
+						),
+					);
+					grown.set(segment.samples.subarray(0, segment.written));
+					segment.samples = grown;
+				}
+				// Int16Array view over the byte buffer: s16le is the platform's
+				// native endianness on every supported target (arm64/x64 are LE).
+				const src = new Int16Array(
+					view.buffer,
+					view.byteOffset,
+					sampleCount,
+				);
+				segment.samples.set(src, segment.written);
+				segment.written += sampleCount;
+			}
+		} catch {
+			// Stream ended or process killed — expected during stop()
+		} finally {
+			try {
+				reader.releaseLock();
+			} catch {
+				/* ignore */
+			}
+		}
+	}
+}

src/utils/audio-player.ts

@@ -6,10 +6,28 @@
  * restart. When mpv isn't installed there is no fallback: the no-op backend
  * surfaces "No audio player found" honestly rather than degrading through
  * players that can't change speed/volume without restarting.
+ *
+ * The backend owns ONE RESIDENT mpv daemon (`--idle=yes --keep-open=yes`)
+ * for the app's lifetime instead of spawning a fresh player per episode:
+ *
+ * - Play/pause/seek are IPC commands on a persistent Unix-socket
+ *   connection — no process spawn, no socket connect/disconnect churn per
+ *   poll, no `waitForSocket` on the play path. Measured command latency is
+ *   single-digit ms; a mid-episode resume after pause takes ~300ms on a
+ *   network stream.
+ * - State (time-pos, pause, duration) is OBSERVED (`observe_property`):
+ *   mpv pushes time-pos at ~20Hz while playing, so `getPosition()` /
+ *   `getPauseState()` read a cache instead of round-tripping the socket on
+ *   every 150ms UI tick. External pauses (AirPod removal, system sleep,
+ *   Now Playing center) arrive as pause property events with zero polling.
+ * - A restored session can PRELOAD: the episode is loaded paused so mpv
+ *   fills its demuxer cache ahead of time; the first real play just flips
+ *   `pause` to false — the ~2s network open is paid at boot, not on the
+ *   user's first Play.
  */
 
 import { platform } from "os";
-import { existsSync } from "fs";
+import { existsSync, unlinkSync } from "fs";
 import { tmpdir } from "os";
 import { dirname, join } from "path";
 import type { Socket, Subprocess } from "bun";
@@ -31,6 +49,18 @@ export interface AudioState {
 export interface AudioBackend {
 	readonly name: BackendName;
 	play(url: string, opts?: PlayOptions): Promise<void>;
+	/**
+	 * Load the URL paused WITHOUT starting playback, so the player buffers
+	 * ahead of the user's first Play (used for boot session restore).
+	 * A subsequent play() of the SAME url flips pause off — near-instant.
+	 */
+	preload(url: string, opts?: PlayOptions): Promise<void>;
+	/**
+	 * Attach a cover-art image to the currently-loaded file at runtime
+	 * (mpv `video-add`). Lets play() start without waiting on art; the
+	 * Now Playing artwork pops in when the download lands.
+	 */
+	addCoverArt(path: string): Promise<void>;
 	pause(): Promise<void>;
 	resume(): Promise<void>;
 	stop(): Promise<void>;
@@ -41,11 +71,11 @@ export interface AudioBackend {
 	getDuration(): Promise<number>;
 	isPlaying(): boolean;
 	/** Live pause state: `true` paused, `false` playing, `undefined` when
-	 *  the read failed (callers keep the last known state). Unlike
+	 *  unknown (player unreachable / not yet loaded). Unlike `isPlaying()` —
-	 *  `isPlaying()` — which reflects only commands PodTUI sent — this
+	 *  which reflects only commands PodTUI sent — this reflects the player's
-	 *  reflects the player's real state, including pauses initiated
+	 *  real state, including pauses initiated OUTSIDE PodTUI (system
-	 *  OUTSIDE PodTUI (system sleep/lock, AirPod removal, device swap,
+	 *  sleep/lock, AirPod removal, device swap, OS media keys, the Now
-	 *  OS media keys, the Now Playing center). */
+	 *  Playing center). */
 	getPauseState(): Promise<boolean | undefined>;
 	/** True while the player process is running (regardless of pause). */
 	isAlive(): boolean;
@@ -80,8 +110,16 @@ function which(cmd: string): string | null {
 	return null;
 }
 
+let mpvInstance = 0;
 function mpvSocketPath(): string {
-	return join(tmpdir(), `podtui-mpv-${process.pid}.sock`);
+	// Per-instance, not just per-pid: tests (and backend switching) create
+	// several MpvBackend objects in ONE bun process — a pid-only path makes
+	// every daemon bind the same socket, so later daemons unlink the path
+	// out from under earlier ones and IPC cross-talks between backends.
+	return join(
+		tmpdir(),
+		`podtui-mpv-${process.pid}-${mpvInstance++}.sock`,
+	);
 }
 
 /**
@@ -124,231 +162,523 @@ function resolveMpvBinary(): string | null {
 	return resolved;
 }
 
+// ── mpv JSON IPC connection ─────────────────────────────────────────
+//
+// One persistent Unix-socket connection to the resident mpv daemon. Lines
+// from mpv are either command responses (`request_id` present — correlated
+// to the pending promise) or unsolicited traffic (property-change events
+// from `observe_property`, end-file, ...), dispatched to the event handler.
+
+interface MpvResponse {
+	error?: string;
+	data?: unknown;
+	request_id?: number;
+}
+
+interface MpvEvent {
+	event: string;
+	/** Observation id for property-change events. */
+	id?: number;
+	name?: string;
+	data?: unknown;
+	reason?: string;
+	error?: string;
+}
+
+type MpvEventHandler = (msg: MpvEvent) => void;
+
+class MpvConnection {
+	private sock: Socket | null = null;
+	private buf = "";
+	private nextId = 1;
+	private pending = new Map<number, (msg: MpvResponse) => void>();
+	private eventWaiters = new Map<string, Array<(msg: MpvEvent) => void>>();
+	onEvent: MpvEventHandler = () => {};
+
+	async connect(path: string): Promise<void> {
+		const { promise, resolve, reject } = Promise.withResolvers<void>();
+		let settled = false;
+		Bun.connect({
+			unix: path,
+			socket: {
+				open: (socket) => {
+					this.sock = socket;
+					if (!settled) {
+						settled = true;
+						resolve();
+					}
+				},
+				data: (_socket, data) => this.onData(data),
+				error: (_socket, err) => {
+					if (!settled) {
+						settled = true;
+						reject(err);
+					}
+					this.handleTeardown();
+				},
+				close: () => this.handleTeardown(),
+			},
+		}).catch((err) => {
+			if (!settled) {
+				settled = true;
+				reject(err);
+			}
+		});
+		await promise;
+	}
+
+	private onData(data: Uint8Array): void {
+		this.buf += Buffer.from(data).toString();
+		let nl = this.buf.indexOf("\n");
+		while (nl !== -1) {
+			const line = this.buf.slice(0, nl);
+			this.buf = this.buf.slice(nl + 1);
+			nl = this.buf.indexOf("\n");
+			if (!line.trim()) continue;
+			let msg: Record<string, unknown>;
+			try {
+				msg = JSON.parse(line) as Record<string, unknown>;
+			} catch {
+				continue; // skip malformed lines
+			}
+			if (msg.request_id !== undefined) {
+				const resolve = this.pending.get(msg.request_id as number);
+				if (resolve) {
+					this.pending.delete(msg.request_id as number);
+					resolve(msg as MpvResponse);
+				}
+			} else if (typeof msg.event === "string") {
+				const event = msg as unknown as MpvEvent;
+				this.onEvent(event);
+				const waiters = this.eventWaiters.get(event.event);
+				if (waiters) {
+					this.eventWaiters.delete(event.event);
+					for (const w of waiters) w(event);
+				}
+			}
+		}
+	}
+
+	/** Socket died / daemon gone: fail all pending commands so no caller
+	 *  hangs on a dead connection. */
+	private handleTeardown(): void {
+		for (const resolve of this.pending.values()) {
+			resolve({ error: "connection-lost" });
+		}
+		this.pending.clear();
+		this.sock = null;
+	}
+
+	/** Send a command and await mpv's response (correlated by request_id).
+	 *  Resolves `{ error: "timeout" }` instead of hanging when mpv stalls. */
+	send(command: unknown[], timeoutMs = 2000): Promise<MpvResponse> {
+		const sock = this.sock;
+		if (!sock) return Promise.resolve({ error: "not-connected" });
+		const id = this.nextId++;
+		const { promise, resolve } = Promise.withResolvers<MpvResponse>();
+		const timeout = setTimeout(() => {
+			if (this.pending.delete(id)) resolve({ error: "timeout" });
+		}, timeoutMs);
+		this.pending.set(id, (msg) => {
+			clearTimeout(timeout);
+			resolve(msg);
+		});
+		sock.write(JSON.stringify({ command, request_id: id }) + "\n");
+		return promise;
+	}
+
+	/** One-shot wait for an mpv event by name. Register BEFORE the command
+	 *  that triggers it. Resolves null on timeout instead of hanging. */
+	waitEvent(name: string, timeoutMs = 5000): Promise<MpvEvent | null> {
+		const { promise, resolve } = Promise.withResolvers<MpvEvent | null>();
+		const list = this.eventWaiters.get(name) ?? [];
+		list.push(resolve);
+		this.eventWaiters.set(name, list);
+		setTimeout(() => {
+			const current = this.eventWaiters.get(name);
+			if (current) {
+				this.eventWaiters.set(
+					name,
+					current.filter((w) => w !== resolve),
+				);
+			}
+			resolve(null);
+		}, timeoutMs);
+		return promise;
+	}
+
+	close(): void {
+		try {
+			this.sock?.end();
+		} catch {
+			/* ignore */
+		}
+		this.handleTeardown();
+	}
+}
+
 // ── mpv Backend ──────────────────────────────────────────────────────
-// Uses JSON IPC over a Unix socket for full bidirectional control.
+// One resident daemon for the app's lifetime, controlled over a single
+// persistent JSON IPC connection with property observation.
+
+/** Property observation ids (correlate property-change events). */
+const OBS_TIME_POS = 1;
+const OBS_PAUSE = 2;
+const OBS_DURATION = 3;
+const OBS_EOF = 4;
 
 export class MpvBackend implements AudioBackend {
 	readonly name: BackendName = "mpv";
 	private proc: Subprocess | null = null;
 	private socketPath = mpvSocketPath();
-	private _playing = false;
+	private conn: MpvConnection | null = null;
+	/** Guarantee daemon startup runs once (concurrent play/preload). */
+	private startPromise: Promise<void> | null = null;
+
+	// Command intent: what PodTUI asked the player to do.
+	private _intentPlaying = false;
+	/** The file currently loaded via loadfile (null = idle). */
+	private _loadedUrl: string | null = null;
+	/** The current file was loadfile'd paused (preload) and not yet played. */
+	private _loadedPaused = false;
+	/** Set on end-file reason "eof"/"error"; cleared by the next loadfile. */
+	private _ended = false;
+
+	// Observed (player-reported) state, pushed by mpv property-change events.
 	private _position = 0;
 	private _duration = 0;
+	/** null until the first pause observation arrives. */
+	private _paused: boolean | null = null;
+
 	private _volume = 100;
 	private _speed = 1;
 	private _exited = false;
+	/** Last playback error reported via end-file reason "error". */
+	private _playbackError: string | null = null;
 
-	async play(url: string, opts?: PlayOptions): Promise<void> {
+	// ── Daemon lifecycle ─────────────────────────────────────────────
-		await this.stop();
 
+	private async ensureDaemon(): Promise<void> {
+		if (this.proc && !this._exited && this.conn) return;
+		if (this.startPromise) return this.startPromise;
+		this.startPromise = this.spawnDaemon().finally(() => {
+			this.startPromise = null;
+		});
+		return this.startPromise;
+	}
+
+	private async spawnDaemon(): Promise<void> {
 		// Clean up stale socket
 		try {
-			if (existsSync(this.socketPath)) {
+			unlinkSync(this.socketPath);
-				const { unlinkSync } = await import("fs");
-				unlinkSync(this.socketPath);
-			}
 		} catch {
 			/* ignore */
 		}
 
-		const args = [
+		this.proc = Bun.spawn(
-			resolveMpvBinary() ?? "mpv",
+			[
-			"--no-video",
+				resolveMpvBinary() ?? "mpv",
-			"--no-terminal",
+				"--no-video",
-			"--really-quiet",
+				"--no-terminal",
-			`--input-ipc-server=${this.socketPath}`,
+				"--really-quiet",
-			`--volume=${Math.round((opts?.volume ?? 1) * 100)}`,
+				// Stay alive after finishing/unloading files; PodTUI owns one mpv
-			`--speed=${opts?.speed ?? 1}`,
+				// for its whole session and switches episodes via loadfile.
-		];
+				"--idle=yes",
-
+				"--keep-open=yes",
-		if (opts?.mediaTitle) {
+				// Cap the demuxer cache. mpv's defaults (150MiB) make it race
-			args.push(`--force-media-title=${opts.mediaTitle}`);
+				// to fill while a preload sits paused — measured 45MB pulled
-		}
+				// within 12s of a boot-restore preload, saturating the link
-
+				// exactly when everything else is starting up. ~90s forward
-		if (opts?.coverArtPath) {
+				// target / 40MiB hard cap is a few MB at podcast bitrates:
-			// Explicit cover file → albumart track → macOS Now Playing artwork
+				// plenty for instant resume + stall resilience.
-			// (works for remote streams, not just local downloads).
+				"--cache-secs=90",
-			args.push(`--cover-art-files=${opts.coverArtPath}`);
+				"--demuxer-max-bytes=40MiB",
-		}
+				"--demuxer-max-back-bytes=20MiB",
-
+				`--input-ipc-server=${this.socketPath}`,
-		if (opts?.startPosition && opts.startPosition > 0) {
+			],
-			args.push(`--start=${opts.startPosition}`);
+			{ stdout: "ignore", stderr: "ignore", stdin: "ignore" },
-		}
+		);
-
-		args.push(url);
-
-		this.proc = Bun.spawn(args, {
-			stdout: "ignore",
-			stderr: "ignore",
-			stdin: "ignore",
-		});
-
-		this._playing = true;
 		this._exited = false;
-		this._position = opts?.startPosition ?? 0;
-		this._volume = Math.round((opts?.volume ?? 1) * 100);
-		this._speed = opts?.speed ?? 1;
-
-		// Wait for socket to appear (mpv creates it async)
-		await this.waitForSocket(2000);
-
-		// Position is fetched live from mpv on each getPosition() call (see
-		// below) — the UI polls it, so no internal poll timer is needed.
-
-		// Detect process exit
 		this.proc.exited
 			.then(() => {
-				this._playing = false;
 				this._exited = true;
+				this._intentPlaying = false;
+				this._loadedUrl = null;
+				this._paused = null;
 			})
 			.catch(() => {});
-	}
 
-	private async waitForSocket(timeoutMs: number): Promise<void> {
+		// mpv creates the socket asynchronously (measured ~600ms cold spawn).
 		const start = Date.now();
-		while (Date.now() - start < timeoutMs) {
+		while (Date.now() - start < 3000) {
-			if (existsSync(this.socketPath)) return;
+			if (this._exited) break;
+			if (existsSync(this.socketPath)) break;
 			await new Promise((r) => setTimeout(r, 50));
 		}
+
+		const conn = new MpvConnection();
+		conn.onEvent = (msg) => this.handleEvent(msg);
+		await conn.connect(this.socketPath);
+		this.conn = conn;
+
+		// Observe the state the UI polls: mpv then pushes changes at ~20Hz
+		// while playing and broadcasts external changes (AirPods pull, OS
+		// media keys) with zero polling from our side.
+		await this.send(["observe_property", OBS_TIME_POS, "time-pos"]);
+		await this.send(["observe_property", OBS_PAUSE, "pause"]);
+		await this.send(["observe_property", OBS_DURATION, "duration"]);
+		// With --keep-open=yes mpv does NOT emit end-file at natural EOF — it
+		// sets eof-reached=true (and pauses at the last frame) instead. That
+		// property is the track-end signal; end-file only covers unload/error.
+		await this.send(["observe_property", OBS_EOF, "eof-reached"]);
 	}
 
-	/** Send a fire-and-forget command (no response needed) */
+	private async send(
-	private async send(command: unknown[]): Promise<void> {
+		command: unknown[],
-		try {
+	): Promise<MpvResponse> {
-			const conn = await Bun.connect({
+		if (!this.conn) return { error: "not-connected" };
-				unix: this.socketPath,
+		return this.conn.send(command);
-				socket: {
+	}
-					data() {},
+
-					error() {},
+	private handleEvent(msg: MpvEvent): void {
-					close() {},
+		if (msg.event === "property-change") {
-					open() {},
+			if (msg.id === OBS_TIME_POS) {
-				},
+				// `data` is number while playing; unavailable → undefined while
-			});
+				// idle. Keep last known on transient gaps, reset on idle.
-			conn.write(JSON.stringify({ command }) + "\n");
+				if (typeof msg.data === "number") this._position = msg.data;
-			// Don't wait, just schedule a close
+			} else if (msg.id === OBS_PAUSE) {
-			setTimeout(() => {
+				if (typeof msg.data === "boolean") this._paused = msg.data;
-				try {
+			} else if (msg.id === OBS_DURATION) {
-					conn.end();
+				if (typeof msg.data === "number" && msg.data > 0) {
-				} catch {}
+					this._duration = msg.data;
-			}, 50);
+				}
-		} catch {
+			} else if (msg.id === OBS_EOF) {
-			/* ignore */
+				// Natural end-of-file (or a brand-new load reporting false).
+				this._ended = msg.data === true;
+				if (this._ended) this._intentPlaying = false;
+			}
+			return;
 		}
+
+		if (msg.event === "end-file") {
+			if (msg.reason === "eof") {
+				this._ended = true;
+				this._intentPlaying = false;
+			} else if (msg.reason === "error") {
+				this._ended = true;
+				this._intentPlaying = false;
+				this._playbackError = msg.error ?? "mpv failed to play the stream";
+			}
+			return;
+		}
+
+		if (msg.event === "file-loaded") {
+			this._ended = false;
+		}
+	}
+
+	// ── File presentation options ────────────────────────────────────
+	//
+	// force-media-title and cover-art-files are set as global properties
+	// BEFORE loadfile (verified: runtime-settable; values containing commas
+	// would corrupt the per-file options string). Numbers (volume, speed,
+	// start, pause) ride as per-file options on loadfile itself so each
+	// loadfile is self-contained.
+
+	private async applyPresentation(opts?: PlayOptions): Promise<void> {
+		await this.send([
+			"set_property",
+			"force-media-title",
+			opts?.mediaTitle ?? "",
+		]);
+		await this.send([
+			"set_property",
+			"cover-art-files",
+			opts?.coverArtPath ?? "",
+		]);
+	}
+
+	private loadfileOptions(opts: PlayOptions | undefined, paused: boolean): string {
+		const parts: string[] = [`pause=${paused ? "yes" : "no"}`];
+		if (opts?.startPosition && opts.startPosition > 0) {
+			parts.push(`start=${Math.max(0, opts.startPosition)}`);
+		}
+		const vol = Math.round((opts?.volume ?? 1) * 100);
+		if (Number.isFinite(vol)) parts.push(`volume=${vol}`);
+		const speed = opts?.speed ?? 1;
+		if (Number.isFinite(speed) && speed > 0) parts.push(`speed=${speed}`);
+		return parts.join(",");
 	}
 
 	/**
-	 * Get a property value from mpv via IPC.
+	 * Every loadfile (play, preload, replay) runs under this mutex: useAudio
-	 *
+	 * fires the boot preload unawaited, so without serialization a user
-	 * Resolves the parsed numeric value, or `undefined` when the read fails
+	 * pressing Play mid-preload would send loadfile(no-pause) followed by the
-	 * (socket error, timeout, unparseable response, or the property being
+	 * in-flight preload's loadfile(pause=yes) — and the stale preload would
-	 * unavailable — e.g. `time-pos` before playback starts). Failure is
+	 * pause the file the user just started. The mutex also prevents
-	 * distinct from a legitimate `0` so callers can keep the last known
+	 * presentation options (title/cover) of one episode from interleaving
-	 * value instead of snapping the position clock to zero on a transient
+	 * with the loadfile of another.
-	 * error; the next poll retries.
-	 *
-	 * mpv multiplexes unsolicited events (audio-reconfig, file-loaded, ...)
-	 * onto the same connection, so we line-buffer and only settle on the
-	 * line that carries the command response (`request_id` set). The socket
-	 * is closed once the response is handled — leaving it open leaks an fd
-	 * per poll, while closing it before mpv processes the request drops the
-	 * reply.
 	 */
-	private async getProperty(name: string): Promise<number | undefined> {
+	private loadMutex: Promise<unknown> = Promise.resolve();
-		try {
-			return await new Promise<number | undefined>((resolve) => {
-				let settled = false;
-				let sock: Socket | null = null;
-				let buf = "";
-				const done = (value: number | undefined) => {
-					if (settled) return;
-					settled = true;
-					clearTimeout(timeout);
-					try {
-						sock?.end();
-					} catch {
-						/* ignore */
-					}
-					resolve(value);
-				};
-				const timeout = setTimeout(() => done(undefined), 300);
 
-				Bun.connect({
+	private runLoadExclusive<T>(fn: () => Promise<T>): Promise<T> {
-					unix: this.socketPath,
+		const result = this.loadMutex.then(fn);
-					socket: {
+		this.loadMutex = result.catch(() => {});
-						open(socket) {
+		return result;
-							sock = socket;
+	}
-							socket.write(
+
-								JSON.stringify({ command: ["get_property", name] }) + "\n",
+	private async loadFileLocked(
-							);
+		url: string,
-						},
+		opts: PlayOptions | undefined,
-						data(_socket, data) {
+		paused: boolean,
-							buf += Buffer.from(data).toString();
+	): Promise<void> {
-							let nl = buf.indexOf("\n");
+		await this.applyPresentation(opts);
-							while (nl !== -1) {
+		// Paused preload of a mid-episode restore: pass NO start= option and
-								const line = buf.slice(0, nl);
+		// seek while paused instead. mpv defers --start stream work (open,
-								buf = buf.slice(nl + 1);
+		// header probe, demuxer seek) until playback begins — measured: the
-								nl = buf.indexOf("\n");
+		// demuxer cache stays EMPTY during the whole preload and the eventual
-								try {
+		// unpause pays 4.3s. A time-pos seek while paused executes at once,
-									const parsed = JSON.parse(line);
+		// so the stream opens and buffers during the preload, and the first
-									// Events carry no request_id; only settle on
+		// real Play is a sub-second unpause.
-									// the actual command response.
+		const pausedSeek =
-									if (parsed?.request_id === undefined) continue;
+			paused && opts?.startPosition && opts.startPosition > 0
-									if (parsed?.data !== undefined) {
+				? opts.startPosition
-										done(Number(parsed.data) || 0);
+				: null;
-									} else {
+		const loadOpts =
-										done(undefined);
+			pausedSeek && opts ? { ...opts, startPosition: undefined } : opts;
-									}
+		// Register the file-loaded waiter BEFORE loadfile: the event can
-									return;
+		// arrive between the command response and listener setup otherwise.
-								} catch {
+		const fileLoaded = pausedSeek && this.conn ? this.conn.waitEvent("file-loaded") : null;
-									/* skip malformed lines */
+		const resp = await this.send([
-								}
+			"loadfile",
-							}
+			url,
-						},
+			"replace",
-						error() {
+			-1,
-							done(undefined);
+			this.loadfileOptions(loadOpts, paused),
-						},
+		]);
-						close() {
+		if (resp.error && resp.error !== "success") {
-							done(undefined);
+			throw new Error(`mpv loadfile failed: ${resp.error}`);
-						},
-					},
-				}).catch(() => done(undefined));
-			});
-		} catch {
-			return undefined;
 		}
+		if (pausedSeek) {
+			// time-pos sent before file-loaded is silently dropped by mpv
+			// (no file yet) — the preload then parked at 0 and the restore
+			// position was lost. Wait for the open, then seek.
+			await fileLoaded;
+			await this.send(["set_property", "time-pos", pausedSeek]);
+			this._position = pausedSeek;
+		}
+		this._loadedUrl = url;
+		this._loadedPaused = paused;
+		this._ended = false;
+		this._playbackError = null;
+		this._position = opts?.startPosition ?? 0;
+		this._duration = 0;
+		this._volume = Math.round((opts?.volume ?? 1) * 100);
+		this._speed = opts?.speed ?? 1;
+	}
+
+	// ── AudioBackend ─────────────────────────────────────────────────
+
+	async play(url: string, opts?: PlayOptions): Promise<void> {
+		await this.ensureDaemon();
+		// Mark intent before the mutex: a boot preload queued behind this
+		// play checks it and skips its own stale paused-load.
+		this._intentPlaying = true;
+		await this.runLoadExclusive(async () => {
+			// Fast path: this exact URL was PRELOADED paused (boot restore) —
+			// mpv has been buffering it since boot, so flipping pause off starts
+			// audio ~instantly. Re-acquire the start position only when it
+			// moved meaningfully since the preload (progress saved meanwhile).
+			if (this._loadedUrl === url && this._loadedPaused && !this._ended) {
+				const target = opts?.startPosition ?? this._position;
+				if (Math.abs(target - this._position) > 2) {
+					await this.send(["set_property", "time-pos", target]);
+					this._position = target;
+				}
+				await this.send([
+					"set_property",
+					"volume",
+					Math.round((opts?.volume ?? 1) * 100),
+				]);
+				await this.send(["set_property", "speed", opts?.speed ?? 1]);
+				if (opts?.coverArtPath) {
+					// File is already loaded: cover-art-files only applies at
+					// load, so add the art as a runtime albumart track instead.
+					await this.send(["set_property", "cover-art-files", opts.coverArtPath]);
+					await this.send(["video-add", opts.coverArtPath]);
+				}
+				if (opts?.mediaTitle) {
+					await this.send(["set_property", "force-media-title", opts.mediaTitle]);
+				}
+				await this.send(["set_property", "pause", false]);
+				this._loadedPaused = false;
+				return;
+			}
+
+			await this.loadFileLocked(url, opts, false);
+		});
+	}
+
+	async preload(url: string, opts?: PlayOptions): Promise<void> {
+		await this.ensureDaemon();
+		await this.runLoadExclusive(async () => {
+			// Already loaded (paused park, or actively playing because the
+			// user pressed Play while this preload was queued — either way
+			// the file is in the player and must not be clobbered).
+			if (this._loadedUrl === url) return;
+			await this.loadFileLocked(url, opts, true);
+			this._intentPlaying = false;
+		});
+	}
+
+	async addCoverArt(path: string): Promise<void> {
+		if (!this._loadedUrl) return;
+		// Keep the property pointing at the latest art too, so a subsequent
+		// loadfile of the same episode carries it.
+		await this.send(["set_property", "cover-art-files", path]);
+		await this.send(["video-add", path]);
 	}
 
 	async pause(): Promise<void> {
 		await this.send(["set_property", "pause", true]);
-		this._playing = false;
+		this._intentPlaying = false;
 	}
 
 	async resume(): Promise<void> {
+		if (this._ended && this._loadedUrl) {
+			// Play pressed on a finished episode: replay from the top.
+			this._ended = false;
+			const url = this._loadedUrl;
+			await this.runLoadExclusive(async () => {
+				await this.loadFileLocked(
+					url,
+					{ volume: this._volume / 100, speed: this._speed },
+					false,
+				);
+			});
+			this._intentPlaying = true;
+			return;
+		}
+		if (this._loadedPaused && this._loadedUrl) {
+			// Deferred first play of a preloaded file.
+			this._loadedPaused = false;
+		}
+		this._ended = false;
 		await this.send(["set_property", "pause", false]);
-		this._playing = true;
+		this._intentPlaying = true;
 	}
 
 	async stop(): Promise<void> {
-		if (this.proc) {
+		if (this.conn && this._loadedUrl) {
-			try {
+			await this.send(["stop"]);
-				this.proc.kill();
-			} catch {
-				/* ignore */
-			}
-			this.proc = null;
 		}
-		this._playing = false;
+		this._intentPlaying = false;
+		this._loadedUrl = null;
+		this._loadedPaused = false;
+		this._ended = false;
 		this._position = 0;
-
+		this._duration = 0;
-		// Clean up socket
+		await this.send(["set_property", "cover-art-files", ""]);
-		try {
-			if (existsSync(this.socketPath)) {
-				const { unlinkSync } = await import("fs");
-				unlinkSync(this.socketPath);
-			}
-		} catch {
-			/* ignore */
-		}
 	}
 
 	async seek(seconds: number): Promise<void> {
@@ -368,41 +698,55 @@ export class MpvBackend implements AudioBackend {
 	}
 
 	async getPosition(): Promise<number> {
-		// Live-fetch `time-pos` so the position clock is as fresh as the
+		// Observed at ~20Hz by mpv — no socket roundtrip on the UI poll.
-		// UI's poll rate (the hook polls this at ~150ms). On a transient IPC
-		// failure, keep the last known value rather than returning 0.
-		if (this._playing && this.proc) {
-			const pos = await this.getProperty("time-pos");
-			if (pos !== undefined) this._position = pos;
-		}
 		return this._position;
 	}
 
 	async getDuration(): Promise<number> {
-		if (this._duration <= 0) {
-			const dur = await this.getProperty("duration");
-			if (dur !== undefined && dur > 0) this._duration = dur;
-		}
 		return this._duration;
 	}
 
 	isPlaying(): boolean {
-		return this._playing;
+		return this._intentPlaying && this.isAlive() && !this._ended;
 	}
 
 	async getPauseState(): Promise<boolean | undefined> {
-		if (!this.isAlive()) return undefined;
+		if (!this.isAlive() || this._paused === null) return undefined;
-		const p = await this.getProperty("pause");
+		return this._paused;
-		if (p === undefined) return undefined;
-		return p === 1;
 	}
 
 	isAlive(): boolean {
 		return this.proc !== null && !this._exited;
 	}
 
+	/** Last mpv playback failure (end-file reason "error"), if any. */
+	getPlaybackError(): string | null {
+		return this._playbackError;
+	}
+
 	dispose(): void {
-		this.stop();
+		const conn = this.conn;
+		this.conn = null;
+		if (conn) {
+			// Ask nicely, then force: dispose runs inside process-exit
+			// handlers where awaiting is not guaranteed to complete.
+			conn.send(["quit"], 500).catch(() => {});
+		}
+		if (this.proc) {
+			try {
+				this.proc.kill();
+			} catch {
+				/* ignore */
+			}
+			this.proc = null;
+		}
+		this._exited = true;
+		this._intentPlaying = false;
+		try {
+			unlinkSync(this.socketPath);
+		} catch {
+			/* ignore */
+		}
 	}
 }
 
@@ -411,6 +755,8 @@ export class MpvBackend implements AudioBackend {
 class NoopBackend implements AudioBackend {
 	readonly name: BackendName = "none";
 	async play(): Promise<void> {}
+	async preload(): Promise<void> {}
+	async addCoverArt(): Promise<void> {}
 	async pause(): Promise<void> {}
 	async resume(): Promise<void> {}
 	async stop(): Promise<void> {}

src/utils/audio-stream-reader.ts

@@ -1,324 +0,0 @@
-/**
- * Real-time audio stream reader for visualization.
- *
- * Spawns a separate ffmpeg process that decodes the same audio URL
- * the player is using and outputs raw PCM data (signed 16-bit LE, mono,
- * 44100 Hz) to a pipe. The reader accumulates samples in a ring buffer
- * and serves windows *at a requested playback position* to the caller.
- *
- * This is independent from the actual playback backend — it's a
- * read-only "tap" on the audio for FFT analysis purposes. Sync with the
- * player is maintained by pacing decode at the player's clock rate
- * (`-readrate <speed>`) while front-loading a burst of LEAD_SECONDS
- * (`-readrate_initial_burst`) so the decode head leads the player
- * position by a stable lead — read() samples at the exact position the
- * player reports, never at the decode head.
- */
-
-/** PCM output format constants */
-const SAMPLE_RATE = 44100;
-const CHANNELS = 1;
-const BYTES_PER_SAMPLE = 2; // s16le
-
-/**
- * How many samples to buffer (~10 seconds).
- * Large enough to absorb the gap between mpv's startup latency (0.5–3s,
- * more for network streams at speed) and the reader's decode head, plus
- * short player stalls. Samples older than the ring window are never needed
- * again — the renderer only samples at the current playback position.
- */
-const RING_BUFFER_SAMPLES = SAMPLE_RATE * 10;
-
-/**
- * Decode-head lead over the player position, in seconds.
- *
- * `-readrate_initial_burst LEAD_SECONDS` makes ffmpeg emit this much audio
- * immediately on start, then pace at realtime (`-readrate speed`) after.
- * The decode head thus leads the player by ~LEAD_SECONDS from the very
- * first frame. read() samples at the player's current position, which is
- * always behind the head — so it finds freshly decoded samples there
- * instead of clamping to stale data.
- *
- * Bare `-readrate speed` (no burst) starts ffmpeg ε behind mpv (input-open
- * + first-packet latency) and, since both advance at the same rate, never
- * catches up — the bars lag by ε (up to several seconds on network
- * streams). The burst eliminates that constant offset.
- *
- * Must stay within the ring window (RING_BUFFER_SAMPLES ~10s) so the
- * lead audio hasn't wrapped out by the time the player reaches it.
- */
-const LEAD_SECONDS = 3;
-
-export interface AudioStreamReaderOptions {
-	/** Audio URL or file path to decode */
-	url: string;
-	/** Sample rate (default: 44100) */
-	sampleRate?: number;
-}
-
-/**
- * Monotonically increasing generation counter.
- * Each start() increments this; the read loop checks it to know
- * if it's been superseded and should bail out.
- */
-let globalGeneration = 0;
-
-import type { Subprocess } from "bun";
-
-export class AudioStreamReader {
-	private proc: Subprocess | null = null;
-	private ringBuffer: Float64Array;
-	private writePos = 0;
-	private totalSamplesWritten = 0;
-	private startPosition = 0;
-	private _running = false;
-	private generation = 0;
-	readonly url: string;
-	private sampleRate: number;
-
-	constructor(options: AudioStreamReaderOptions) {
-		this.url = options.url;
-		this.sampleRate = options.sampleRate ?? SAMPLE_RATE;
-		this.ringBuffer = new Float64Array(RING_BUFFER_SAMPLES);
-	}
-
-	/** Whether the reader is actively reading samples. */
-	get running(): boolean {
-		return this._running;
-	}
-
-	/** Total number of samples written since start(). */
-	get samplesWritten(): number {
-		return this.totalSamplesWritten;
-	}
-
-	/**
-	 * Start the ffmpeg decode process and begin reading PCM data.
-	 *
-	 * If already running, the previous process is killed first.
-	 * Uses a generation counter to guarantee that only one read loop
-	 * is ever active — stale loops from killed processes bail out
-	 * immediately.
-	 *
-	 * @param startPosition Seek position in seconds (default: 0).
-	 * @param speed Playback speed multiplier (default: 1). Paces ffmpeg
-	 *              at the player's advance rate so decode tracks the
-	 *              player clock; `-readrate_initial_burst` front-loads
-	 *              a LEAD_SECONDS head start.
-	 */
-	start(startPosition = 0, speed = 1): void {
-		// Always kill the previous process first — no early return on _running
-		this.killProcess();
-
-		if (!Bun.which("ffmpeg")) {
-			throw new Error("ffmpeg not found — required for audio visualization");
-		}
-
-		// Increment generation so any lingering read loop from a previous
-		// start() will see a mismatch and exit.
-		this.generation = ++globalGeneration;
-		this.startPosition = Math.max(0, startPosition);
-
-		const readRate = Math.max(0.25, speed > 0 ? speed : 1);
-
-		const args = [
-			"ffmpeg",
-			"-loglevel",
-			"quiet",
-			// Pace input at the player's advance rate (speed× native). Combined
-			// with -readrate_initial_burst below, the decode head starts
-			// LEAD_SECONDS ahead of the player and advances at the same rate —
-			// read() samples at the player position and always finds fresh data.
-			"-readrate",
-			String(readRate),
-			// Front-load LEAD_SECONDS of audio immediately so the decode head
-			// leads the player from the very first frame. Without this, ffmpeg
-			// starts ε behind mpv (input-open + first-packet latency) and,
-			// pacing at the same rate, never catches up — bars lag by ε.
-			"-readrate_initial_burst",
-			String(LEAD_SECONDS),
-		];
-
-		// `-reconnect*` are http-protocol options: ffmpeg rejects them at
-		// input-open when the input is a local file, killing the process
-		// before any PCM is produced. Only pass them for network URLs.
-		if (/^https?:\/\//i.test(this.url)) {
-			args.push(
-				"-reconnect",
-				"1",
-				"-reconnect_streamed",
-				"1",
-				"-reconnect_delay_max",
-				"5",
-			);
-		}
-
-		// Seek before input for network efficiency
-		if (startPosition > 0) {
-			args.push("-ss", String(startPosition));
-		}
-
-		args.push("-i", this.url);
-
-		// No atempo filter: the renderer samples the *source* audio at the
-		// player's current position, so output samples map 1:1 to input time
-		// (stream index = (targetSeconds - startPosition) * sampleRate).
-		args.push(
-			"-ac",
-			String(CHANNELS),
-			"-ar",
-			String(this.sampleRate),
-			"-f",
-			"s16le",
-			"-acodec",
-			"pcm_s16le",
-			"-",
-		);
-
-		this.proc = Bun.spawn(args, {
-			stdout: "pipe",
-			stderr: "ignore",
-			stdin: "ignore",
-		});
-
-		this._running = true;
-		this.writePos = 0;
-		this.totalSamplesWritten = 0;
-
-		const myGeneration = this.generation;
-
-		this.readLoop(myGeneration);
-
-		// Detect process exit
-		this.proc.exited
-			.then(() => {
-				// Only clear _running if this is still the current generation
-				if (this.generation === myGeneration) {
-					this._running = false;
-				}
-			})
-			.catch(() => {
-				if (this.generation === myGeneration) {
-					this._running = false;
-				}
-			});
-	}
-
-	/**
-	 * Read the visualization window ending at `targetSeconds` of playback.
-	 *
-	 * The player (mpv) and this decoder are independent processes, so the
-	 * decode head and the actual playback position drift apart (startup skew,
-	 * stalls, speed changes). Instead of sampling the decode head, we select
-	 * the window *at* the position the player reports, clamped to the nearest
-	 * available samples when the target hasn't been decoded yet (decode head
-	 * behind) or has already wrapped out of the ring (long stall).
-	 *
-	 * @param out - Float64Array to fill with samples (scaled ~+/-32768 for cavacore).
-	 * @param targetSeconds - Playback position (input seconds) to sample.
-	 * @returns Number of samples written to `out`.
-	 */
-	read(out: Float64Array, targetSeconds: number): number {
-		if (this.totalSamplesWritten <= 0 || out.length === 0) return 0;
-
-		const headSample = this.totalSamplesWritten - 1;
-		const coveredStart = Math.max(
-			0,
-			this.totalSamplesWritten - this.ringBuffer.length,
-		);
-
-		const targetSample = Math.max(
-			0,
-			Math.round((targetSeconds - this.startPosition) * this.sampleRate),
-		);
-
-		// Window end: the target, clamped to what's been decoded so far.
-		const endSample = Math.min(targetSample, headSample);
-		// Window start: at most out.length samples back, clamped to what the
-		// ring still holds (target older than the ring -> serve the oldest
-		// available window, which is the closest to the target).
-		const startSample = Math.max(
-			coveredStart,
-			Math.min(endSample, endSample - out.length + 1),
-		);
-		const available = endSample - startSample + 1;
-		if (available <= 0) return 0;
-
-		const ringLen = this.ringBuffer.length;
-		for (let i = 0; i < available; i++) {
-			out[i] = this.ringBuffer[(startSample + i) % ringLen];
-		}
-
-		return available;
-	}
-
-	/**
-	 * Stop the ffmpeg process and clean up.
-	 * Safe to call multiple times. Guarantees the read loop exits.
-	 */
-	stop(): void {
-		// Bump generation to invalidate any running read loop
-		this.generation = ++globalGeneration;
-		this._running = false;
-		this.killProcess();
-		this.writePos = 0;
-		this.totalSamplesWritten = 0;
-	}
-
-	/**
-	 * Restart the reader at a new position and/or speed.
-	 */
-	restart(startPosition = 0, speed = 1): void {
-		this.start(startPosition, speed);
-	}
-
-	/** Kill the ffmpeg process without touching generation/state. */
-	private killProcess(): void {
-		if (this.proc) {
-			try {
-				this.proc.kill();
-			} catch {
-				/* ignore */
-			}
-			this.proc = null;
-		}
-	}
-
-	/** Internal: continuously reads stdout from ffmpeg and fills the ring buffer. */
-	private async readLoop(myGeneration: number): Promise<void> {
-		const stdout = this.proc?.stdout;
-		if (!stdout || typeof stdout === "number") return;
-
-		const reader = (stdout as ReadableStream<Uint8Array>).getReader();
-		try {
-			while (this.generation === myGeneration) {
-				const { done, value } = await reader.read();
-				if (done || this.generation !== myGeneration) break;
-				if (!value || value.byteLength === 0) continue;
-
-				const sampleCount = Math.floor(value.byteLength / BYTES_PER_SAMPLE);
-				if (sampleCount === 0) continue;
-
-				const int16View = new Int16Array(
-					value.buffer,
-					value.byteOffset,
-					sampleCount,
-				);
-
-				for (let i = 0; i < sampleCount; i++) {
-					this.ringBuffer[this.writePos] = int16View[i];
-					this.writePos = (this.writePos + 1) % this.ringBuffer.length;
-					this.totalSamplesWritten++;
-				}
-			}
-		} catch {
-			// Stream ended or process killed — expected during stop()
-		} finally {
-			try {
-				reader.releaseLock();
-			} catch {
-				/* ignore */
-			}
-		}
-	}
-}

src/utils/cover-art.ts

@@ -2,34 +2,97 @@
  * Cover-art staging for the system Now Playing session.
  *
  * macOS shows the media session's albumart in the audio center (Control
- * Center / lock screen). mpv reads it from `--cover-art-files` (loads the
+ * Center / lock screen). mpv reads artwork from `--cover-art-files` (loads
- * file as an albumart video track), so the podcast cover is staged to a temp
+ * the file as an albumart video track), so the podcast cover must exist on
- * file BEFORE playback starts and passed to mpv.
+ * disk before (cover-art-files) or right after (video-add) playback starts.
+ *
+ * Covers are cached persistently under `$XDG_CACHE_HOME/podtui/covers`
+ * (~/.cache/podtui/covers by default), keyed by the URL hash, so the
+ * download happens ONCE per feed — subsequent plays (including the
+ * boot-restored episode) hit the disk cache and never wait on the network.
+ * The play path must never block on art: `cachedCoverPath` is the sync
+ * fast path; `fetchCoverArt` is awaited only by flows where latency does
+ * not matter (CLI play) or fired in the background with the result
+ * applied to a live mpv via `video-add`.
  *
  * Downloaded via `curl` (not `fetch`): Bun's `fetch` hangs in compiled
  * `bun build --compile` binaries (Bun 1.3.8), timing out on any host —
  * which would silently drop every cover in shipped builds. curl is present
- * on macOS and Linux. Bounded: a slow cover server must never stall audio,
+ * on macOS and Linux. Bounded: a slow cover server must never stall audio.
- * so an 8s cap drops the art.
  */
 
-import { tmpdir } from "os";
+import { existsSync, mkdirSync, renameSync, statSync } from "fs";
+import { createHash } from "crypto";
 import { join } from "path";
-import { unlinkSync, statSync } from "fs";
 
-export const coverTempPath = () => join(tmpdir(), "podtui-cover.jpg");
+/** Resolved once per process; null when no home directory is detectable. */
+let cacheDir: string | null | undefined;
 
-export async function fetchCoverArt(url: string): Promise<string | null> {
+function coversDir(): string | null {
-	const path = coverTempPath();
+	if (cacheDir !== undefined) return cacheDir;
+	let dir: string | null = null;
 	try {
-		unlinkSync(path);
+		const home = process.env.HOME ?? process.env.USERPROFILE ?? "";
+		if (home) {
+			dir = join(process.env.XDG_CACHE_HOME ?? join(home, ".cache"), "podtui", "covers");
+			mkdirSync(dir, { recursive: true });
+		}
 	} catch {
-		/* no stale cover */
+		dir = null;
 	}
+	cacheDir = dir;
+	return dir;
+}
+
+function cachePathFor(url: string): string | null {
+	const dir = coversDir();
+	if (!dir) return null;
+	return join(dir, `${createHash("sha1").update(url).digest("hex")}.jpg`);
+}
+
+/**
+ * Sync fast path: the cached cover file for `url`, or null when it has not
+ * been downloaded yet. This is what keeps cover art off the play() critical
+ * path — a cache hit costs one stat() and a miss simply plays without art
+ * (or applies it late via video-add).
+ */
+export function cachedCoverPath(url: string): string | null {
+	const path = cachePathFor(url);
+	if (!path) return null;
 	try {
-		return await Promise.race([
+		return existsSync(path) && statSync(path).size > 0 ? path : null;
-			(async () => {
+	} catch {
-				const proc = Bun.spawn([
+		return null;
+	}
+}
+
+/** In-flight downloads keyed by URL — a burst of plays of the same show
+ *  shares one curl instead of racing ephemeral files. */
+const inflight = new Map<string, Promise<string | null>>();
+
+/**
+ * Fetch the cover for `url`, returns its cache path. Cache hits return
+ * immediately. Downloads are single-flight per URL and time-bounded (8s);
+ * failure resolves null and retries on the next call. The file is written
+ * to a temp name and renamed into place so a killed process can never
+ * poison the cache with a truncated file.
+ */
+export function fetchCoverArt(url: string): Promise<string | null> {
+	const cached = cachedCoverPath(url);
+	if (cached) return Promise.resolve(cached);
+
+	const dest = cachePathFor(url);
+	if (!dest) return Promise.resolve(null);
+
+	const pending = inflight.get(url);
+	if (pending) return pending;
+
+	const task = (async (): Promise<string | null> => {
+		const staging = `${dest}.${process.pid}.tmp`;
+		try {
+			const { promise, resolve } = Promise.withResolvers<string | null>();
+			const proc = Bun.spawn(
+				[
 					"curl",
 					"-sS",
 					"--fail",
@@ -38,20 +101,41 @@ export async function fetchCoverArt(url: string): Promise<string | null> {
 					"--max-filesize",
 					"2097152",
 					"-o",
-					path,
+					staging,
 					url,
-				]);
+				],
-				const code = await proc.exited;
+				{ stdout: "ignore", stderr: "ignore", stdin: "ignore" },
-				if (code !== 0) return null;
+			);
-				try {
+			proc.exited
-					return statSync(path).size > 0 ? path : null;
+				.then((code) => {
-				} catch {
+					if (code !== 0) return resolve(null);
-					return null;
+					try {
-				}
+						if (statSync(staging).size <= 0) return resolve(null);
-			})(),
+						renameSync(staging, dest);
-			new Promise<null>((resolve) => setTimeout(() => resolve(null), 8000)),
+						resolve(dest);
-		]);
+					} catch {
-	} catch {
+						resolve(null);
-		return null;
+					}
-	}
+				})
+				.catch(() => resolve(null));
+			setTimeout(() => resolve(null), 8000);
+			return await promise;
+		} finally {
+			inflight.delete(url);
+			// Best-effort staging cleanup (no-op after a successful rename).
+			try {
+				Bun.spawn(["rm", "-f", staging], { stdout: "ignore", stderr: "ignore" });
+			} catch {
+				/* ignore */
+			}
+		}
+	})();
+
+	inflight.set(url, task);
+	return task;
+}
+
+/** Fire-and-forget warm-up used by the boot/restore path. */
+export function prefetchCoverArt(url: string): void {
+	fetchCoverArt(url).catch(() => {});
 }

tests/audio-backend.test.ts

@@ -0,0 +1,192 @@
+/**
+ * MpvBackend resident-daemon contract tests (real mpv process).
+ *
+ * Pins the IPC contract the app's playback depends on:
+ *
+ * 1. play() loads a file and position advances (observed, no polling).
+ * 2. pause()/resume() flip the player-reported pause state through IPC.
+ * 3. seek() lands where asked.
+ * 4. stop() unloads the file but keeps the daemon alive (isAlive stays
+ *    true — the daemon model's whole point: no process churn per episode).
+ * 5. preload() parks an episode paused; play() of the SAME url then starts
+ *    it by unpausing — the boot-restore fast path with no second load.
+ * 6. EOF: the episode ends → isPlaying() goes false on its own; pressing
+ *    resume() afterwards replays from the top.
+ *
+ * All playback runs silent (volume 0). Requires a real mpv on PATH;
+ * tests skip where it is missing.
+ */
+import { test, expect } from "bun:test";
+import { tmpdir } from "os";
+import { join } from "path";
+import { MpvBackend } from "../src/utils/audio-player";
+
+const SAMPLE_RATE = 22050;
+const FREQ = 440;
+const AMP = 20000;
+
+/** Write a WAV file containing `seconds` of a sine at AMP amplitude. */
+function writeSineWav(path: string, seconds: number): void {
+	const total = Math.round(seconds * SAMPLE_RATE);
+	const dataSize = total * 2;
+	const buf = new Uint8Array(44 + dataSize);
+	const dv = new DataView(buf.buffer);
+	const ascii = (off: number, s: string) => {
+		for (let i = 0; i < s.length; i++) buf[off + i] = s.charCodeAt(i);
+	};
+	ascii(0, "RIFF");
+	dv.setUint32(4, 36 + dataSize, true);
+	ascii(8, "WAVE");
+	ascii(12, "fmt ");
+	dv.setUint32(16, 16, true);
+	dv.setUint16(20, 1, true);
+	dv.setUint16(22, 1, true);
+	dv.setUint32(24, SAMPLE_RATE, true);
+	dv.setUint32(28, SAMPLE_RATE * 2, true);
+	dv.setUint16(32, 2, true);
+	dv.setUint16(34, 16, true);
+	ascii(36, "data");
+	dv.setUint32(40, dataSize, true);
+	for (let i = 0; i < total; i++) {
+		const v = Math.round(AMP * Math.sin((2 * Math.PI * FREQ * i) / SAMPLE_RATE));
+		dv.setInt16(44 + i * 2, v, true);
+	}
+	Bun.write(path, buf);
+}
+
+/** Poll a predicate until true or the deadline expires. */
+async function waitFor(
+	label: string,
+	pred: () => boolean | Promise<boolean>,
+	timeoutMs = 8000,
+): Promise<void> {
+	const start = Date.now();
+	for (;;) {
+		if (await pred()) return;
+		if (Date.now() - start > timeoutMs) {
+			throw new Error(`${label}: not true within ${timeoutMs}ms`);
+		}
+		await Bun.sleep(50);
+	}
+}
+
+const hasMpv = !!Bun.which("mpv");
+const wavA = join(tmpdir(), `podtui-backend-${process.pid}-a.wav`);
+const wavB = join(tmpdir(), `podtui-backend-${process.pid}-b.wav`);
+
+function fixtureWavs(): void {
+	writeSineWav(wavA, 8);
+	writeSineWav(wavB, 8);
+}
+
+async function cleanup(backend: MpvBackend): Promise<void> {
+	backend.dispose();
+	await Bun.$`rm -f ${wavA} ${wavB}`.quiet();
+}
+
+test.skipIf(!hasMpv)(
+	"play / pause / resume / seek over the resident daemon",
+	async () => {
+		fixtureWavs();
+		const backend = new MpvBackend();
+		try {
+			await backend.play(wavA, { volume: 0, speed: 1, startPosition: 1 });
+			expect(backend.isAlive()).toBe(true);
+			expect(backend.isPlaying()).toBe(true);
+
+			// Observed position advances without any polling from us.
+			await waitFor("position advances", async () => (await backend.getPosition()) > 1.3);
+			expect(await backend.getPauseState()).toBe(false);
+			expect(await backend.getDuration()).toBeGreaterThan(7.5);
+
+			// Pause: reported by the player's own state, position stalls.
+			await backend.pause();
+			await waitFor("paused state observed", async () => (await backend.getPauseState()) === true);
+			const posAtPause = await backend.getPosition();
+			await Bun.sleep(400);
+			expect(Math.abs((await backend.getPosition()) - posAtPause)).toBeLessThan(0.3);
+
+			// Resume: clock advances again.
+			await backend.resume();
+			await waitFor("resumed state observed", async () => (await backend.getPauseState()) === false);
+			await waitFor(
+				"position advances after resume",
+				async () => (await backend.getPosition()) > posAtPause + 0.3,
+			);
+
+			// Seek lands where asked.
+			await backend.seek(6);
+			await waitFor(
+				"seek observed",
+				async () => Math.abs((await backend.getPosition()) - 6) < 0.5,
+			);
+
+			// Stop unloads the file — but the daemon stays resident.
+			await backend.stop();
+			expect(backend.isPlaying()).toBe(false);
+			expect(backend.isAlive()).toBe(true);
+			expect(await backend.getPosition()).toBe(0);
+		} finally {
+			await cleanup(backend);
+		}
+	},
+	{ timeout: 20000 },
+);
+
+test.skipIf(!hasMpv)(
+	"preload parks the episode paused; play() of the same url starts it by unpausing",
+	async () => {
+		fixtureWavs();
+		const backend = new MpvBackend();
+		try {
+			await backend.preload(wavB, { volume: 0, speed: 1, startPosition: 2 });
+			// Parked: paused, at the requested offset, nothing advancing.
+			await waitFor(
+				"preload observed paused",
+				async () => (await backend.getPauseState()) === true,
+			);
+			const parkedPos = await backend.getPosition();
+			expect(parkedPos).toBeGreaterThan(1.5);
+			expect(backend.isPlaying()).toBe(false);
+			await Bun.sleep(400);
+			expect(Math.abs((await backend.getPosition()) - parkedPos)).toBeLessThan(0.3);
+
+			// The boot-restore fast path: play() unpauses instead of re-loading.
+			await backend.play(wavB, { volume: 0, speed: 1, startPosition: parkedPos });
+			expect(backend.isPlaying()).toBe(true);
+			await waitFor(
+				"preload fast path plays",
+				async () => (await backend.getPosition()) > parkedPos + 0.3,
+			);
+		} finally {
+			await cleanup(backend);
+		}
+	},
+	{ timeout: 20000 },
+);
+
+test.skipIf(!hasMpv)(
+	"EOF marks playback ended; resume() then replays from the top",
+	async () => {
+		const wavShort = join(tmpdir(), `podtui-backend-${process.pid}-short.wav`);
+		writeSineWav(wavShort, 2);
+		const backend = new MpvBackend();
+		try {
+			await backend.play(wavShort, { volume: 0, speed: 2 });
+			// 2s at 2x ends in ~1s+startup. isPlaying() must drop on its own.
+			await waitFor("episode ended", async () => !backend.isPlaying());
+
+			// Play pressed on a finished episode replays from the top.
+			await backend.resume();
+			await waitFor("replay started", async () => backend.isPlaying());
+			await waitFor(
+				"replay position near start",
+				async () => (await backend.getPosition()) < 3 && backend.isPlaying(),
+			);
+		} finally {
+			backend.dispose();
+			await Bun.$`rm -f ${wavShort}`.quiet();
+		}
+	},
+	{ timeout: 20000 },
+);

tests/audio-pcm-cache.test.ts

@@ -0,0 +1,231 @@
+/**
+ * EpisodePcmCache position-index contract tests.
+ *
+ * The visualizer's bars are served from a position-indexed PCM cache that
+ * ffmpeg fills at full speed. These tests pin the observable contracts the
+ * fragile paced-ring design kept breaking:
+ *
+ * 1. readWindow(out, at) serves the EXACT window ending at playback time
+ *    `at` — position mapping is sample-precise, independent of how fast or
+ *    far the decode has run.
+ * 2. Reads outside decoded coverage return 0 — the renderer HOLDS the last
+ *    frame. (The old reader CLAMPED to a stale buffer; re-rendering the
+ *    same window decayed cava into a frozen junk pattern after pause.)
+ * 3. pauseDecode kills ffmpeg but keeps the cache: resume serves bars
+ *    instantly, ensureDecodeAround restarts the tail decode.
+ * 4. Seeking into an undecoded region starts a new segment there WITHOUT
+ *    invalidating the previously decoded coverage.
+ *
+ * Uses a self-generated WAV (440Hz sine, mono, 22050Hz s16le — the cache's
+ * native rate) so expected samples are computed analytically with no
+ * resampler tolerance.
+ */
+import { test, expect } from "bun:test";
+import { tmpdir } from "os";
+import { join } from "path";
+import { EpisodePcmCache } from "../src/utils/audio-pcm-cache";
+
+const SAMPLE_RATE = 22050;
+const FREQ = 440;
+const AMP = 30000;
+
+/** Write a WAV file containing `seconds` of a 440Hz sine at AMP amplitude. */
+function writeSineWav(path: string, seconds: number): void {
+	const total = Math.round(seconds * SAMPLE_RATE);
+	const dataSize = total * 2;
+	const buf = new Uint8Array(44 + dataSize);
+	const dv = new DataView(buf.buffer);
+	const ascii = (off: number, s: string) => {
+		for (let i = 0; i < s.length; i++) buf[off + i] = s.charCodeAt(i);
+	};
+	ascii(0, "RIFF");
+	dv.setUint32(4, 36 + dataSize, true);
+	ascii(8, "WAVE");
+	ascii(12, "fmt ");
+	dv.setUint32(16, 16, true);
+	dv.setUint16(20, 1, true); // PCM
+	dv.setUint16(22, 1, true); // mono
+	dv.setUint32(24, SAMPLE_RATE, true);
+	dv.setUint32(28, SAMPLE_RATE * 2, true);
+	dv.setUint16(32, 2, true);
+	dv.setUint16(34, 16, true);
+	ascii(36, "data");
+	dv.setUint32(40, dataSize, true);
+	for (let i = 0; i < total; i++) {
+		const v = Math.round(AMP * Math.sin((2 * Math.PI * FREQ * i) / SAMPLE_RATE));
+		dv.setInt16(44 + i * 2, v, true);
+	}
+	Bun.write(path, buf);
+}
+
+/** Analytic sample value at a file index, matching the writer's formula. */
+function expectedAt(fileIndex: number): number {
+	return Math.round(AMP * Math.sin((2 * Math.PI * FREQ * fileIndex) / SAMPLE_RATE));
+}
+
+/** Block until the cache covers playback time `sec`. */
+async function waitForCoverage(
+	cache: EpisodePcmCache,
+	sec: number,
+	timeoutMs = 10000,
+): Promise<void> {
+	const start = Date.now();
+	while (!cache.covers(sec)) {
+		if (Date.now() - start > timeoutMs) {
+			throw new Error(`cache did not cover ${sec}s in time`);
+		}
+		await Bun.sleep(25);
+	}
+}
+
+/** Block until the furthest decode pass has hit stream EOF. */
+async function waitForFinished(
+	cache: EpisodePcmCache,
+	timeoutMs = 10000,
+): Promise<void> {
+	const start = Date.now();
+	while (!cache.decodeFinished) {
+		if (Date.now() - start > timeoutMs) {
+			throw new Error("decode did not finish in time");
+		}
+		await Bun.sleep(25);
+	}
+}
+
+function tmpWav(): string {
+	return join(tmpdir(), `podtui-pcm-${process.pid}-${Math.floor(Math.random() * 1e9)}.wav`);
+}
+
+const hasFfmpeg = !!Bun.which("ffmpeg");
+const FIVE_SEC_BASE = 5 * SAMPLE_RATE; // decode offset for position-mapping tests
+
+test.skipIf(!hasFfmpeg)(
+	"readWindow serves the exact window ending at the requested position",
+	async () => {
+		const wav = tmpWav();
+		writeSineWav(wav, 30);
+		const cache = new EpisodePcmCache({ url: wav });
+		try {
+			cache.startDecode(5);
+			await waitForCoverage(cache, 6.5);
+
+			const out = new Float64Array(512);
+			expect(cache.readWindow(out, 5.1)).toBe(512);
+			// Window ENDS at the target: out[i] is the sample at
+			// round(5.1*SR) - (len-1) + i (5s offset + 0.1s).
+			const endIdx = Math.round(5.1 * SAMPLE_RATE);
+			for (let i = 0; i < 512; i++) {
+				const idx = endIdx - (out.length - 1) + i;
+				expect(Math.abs(out[i] - expectedAt(idx))).toBeLessThanOrEqual(1);
+			}
+
+			// A 5ms later window is the same stream shifted by exactly
+			// round(0.005*SR)=110 samples — pins position mapping precision.
+			const later = new Float64Array(512);
+			expect(cache.readWindow(later, 5.105)).toBe(512);
+			for (let i = 0; i <= 512 - 111; i++) {
+				expect(later[i]).toBe(out[i + 110]);
+			}
+		} finally {
+			cache.stop();
+			await Bun.$`rm -f ${wav}`.quiet();
+		}
+	},
+);
+
+test.skipIf(!hasFfmpeg)(
+	"reads outside decoded coverage return 0 (renderer holds last frame, never stale junk)",
+	async () => {
+		const wav = tmpWav();
+		writeSineWav(wav, 30);
+		const cache = new EpisodePcmCache({ url: wav });
+		try {
+			cache.startDecode(5);
+			await waitForCoverage(cache, 5.5);
+
+			const out = new Float64Array(512);
+			out.fill(-999);
+
+			// Beyond the decode frontier.
+			expect(cache.readWindow(out, 999)).toBe(0);
+			// Before the segment base (decode started at 5s).
+			expect(cache.readWindow(out, 4.0)).toBe(0);
+			// Buffer untouched — no partial/stale samples leak through.
+			for (let i = 0; i < 16; i++) expect(out[i]).toBe(-999);
+		} finally {
+			cache.stop();
+			await Bun.$`rm -f ${wav}`.quiet();
+		}
+	},
+);
+
+test.skipIf(!hasFfmpeg)(
+	"pauseDecode keeps the cache: resume serves instantly, tail decode continues",
+	async () => {
+		const wav = tmpWav();
+		writeSineWav(wav, 12); // short: full tail decode lands well under a second
+		const cache = new EpisodePcmCache({ url: wav });
+		try {
+			cache.startDecode(0);
+			await waitForCoverage(cache, 1.5);
+
+			// Pause: decode dies, cache must survive.
+			cache.pauseDecode();
+			expect(cache.decoding).toBe(false);
+			expect(cache.covers(1)).toBe(true);
+
+			// Serve from cache immediately after pause — this is the resume
+			// fast path: zero ffmpeg cold start.
+			const out = new Float64Array(512);
+			expect(cache.readWindow(out, 1.0)).toBe(512);
+			const endIdx = Math.round(1.0 * SAMPLE_RATE);
+			for (let i = 0; i < 512; i++) {
+				const idx = endIdx - (out.length - 1) + i;
+				expect(Math.abs(out[i] - expectedAt(idx))).toBeLessThanOrEqual(1);
+			}
+
+			// Resume: tail decode restarts and eventually covers the file.
+			cache.ensureDecodeAround(1.0);
+			await waitForFinished(cache);
+			expect(cache.coverageEndSec).toBeGreaterThanOrEqual(11.9);
+			expect(cache.readWindow(out, 11.5)).toBe(512);
+		} finally {
+			cache.stop();
+			await Bun.$`rm -f ${wav}`.quiet();
+		}
+	},
+	{ timeout: 20000 },
+);
+
+test.skipIf(!hasFfmpeg)(
+	"seek into an undecoded region starts a new segment without losing earlier coverage",
+	async () => {
+		const wav = tmpWav();
+		writeSineWav(wav, 30);
+		const cache = new EpisodePcmCache({ url: wav });
+		try {
+			// Decoded the back half only...
+			cache.startDecode(10);
+			await waitForCoverage(cache, 11);
+			expect(cache.covers(2)).toBe(false);
+
+			// ...then the user seeks to 2s: a new segment decodes the front,
+			// and the back-half coverage stays valid throughout.
+			cache.ensureDecodeAround(2);
+			await waitForCoverage(cache, 2.2);
+			expect(cache.covers(10.5)).toBe(true);
+
+			const out = new Float64Array(512);
+			expect(cache.readWindow(out, 10.5)).toBe(512);
+			const endIdx = Math.round(10.5 * SAMPLE_RATE);
+			for (let i = 0; i < 512; i++) {
+				const idx = endIdx - (out.length - 1) + i;
+				expect(Math.abs(out[i] - expectedAt(idx))).toBeLessThanOrEqual(1);
+			}
+		} finally {
+			cache.stop();
+			await Bun.$`rm -f ${wav}`.quiet();
+		}
+	},
+	{ timeout: 20000 },
+);

tests/audio-stream-reader.test.ts

@@ -1,239 +0,0 @@
-/**
- * AudioStreamReader sync contract tests.
- *
- * The visualizer's bars must track the player's position in real time even
- * though the reader is an independent ffmpeg process. These tests pin the
- * two mechanisms that make that true:
- *
- * 1. `read(out, target)` serves the FFT window *at* the requested playback
- *    position — not at the decode head, which drifts from the player
- *    (startup skew, stalls).
- * 2. Decode is paced at the player's clock rate (`-readrate <speed>`), so
- *    the decode head keeps up with the position at any playback speed —
- *    native-rate pacing falls behind by (speed-1)s per second.
- *
- * Uses a self-generated WAV (440Hz sine, mono, 44.1kHz s16le) so the
- * expected samples can be computed analytically and compared exactly.
- */
-import { test, expect } from "bun:test";
-import { tmpdir } from "os";
-import { join } from "path";
-import { AudioStreamReader } from "../src/utils/audio-stream-reader";
-
-const SAMPLE_RATE = 44100;
-const FREQ = 440;
-const AMP = 30000;
-
-/** Write a WAV file containing `seconds` of a 440Hz sine at AMP amplitude. */
-function writeSineWav(path: string, seconds: number): void {
-	const total = Math.round(seconds * SAMPLE_RATE);
-	const dataSize = total * 2;
-	const buf = new Uint8Array(44 + dataSize);
-	const dv = new DataView(buf.buffer);
-	const ascii = (off: number, s: string) => {
-		for (let i = 0; i < s.length; i++) buf[off + i] = s.charCodeAt(i);
-	};
-	ascii(0, "RIFF");
-	dv.setUint32(4, 36 + dataSize, true);
-	ascii(8, "WAVE");
-	ascii(12, "fmt ");
-	dv.setUint32(16, 16, true);
-	dv.setUint16(20, 1, true); // PCM
-	dv.setUint16(22, 1, true); // mono
-	dv.setUint32(24, SAMPLE_RATE, true);
-	dv.setUint32(28, SAMPLE_RATE * 2, true);
-	dv.setUint16(32, 2, true);
-	dv.setUint16(34, 16, true);
-	ascii(36, "data");
-	dv.setUint32(40, dataSize, true);
-	for (let i = 0; i < total; i++) {
-		const v = Math.round(AMP * Math.sin((2 * Math.PI * FREQ * i) / SAMPLE_RATE));
-		dv.setInt16(44 + i * 2, v, true);
-	}
-	Bun.write(path, buf);
-}
-
-/** Analytic sample value at a file index, matching the writer's formula. */
-function expectedAt(fileIndex: number): number {
-	return Math.round(AMP * Math.sin((2 * Math.PI * FREQ * fileIndex) / SAMPLE_RATE));
-}
-
-/**
- * Block until the reader's decode head has advanced past `samples` samples.
- * The head advances at readrate × real time, so this bounds how long we wait.
- */
-async function waitForHead(
-	reader: AudioStreamReader,
-	samples: number,
-	timeoutMs = 8000,
-): Promise<void> {
-	const start = Date.now();
-	while (reader.samplesWritten < samples) {
-		if (Date.now() - start > timeoutMs) {
-			throw new Error("reader decode head did not advance in time");
-		}
-		await Bun.sleep(25);
-	}
-}
-
-const hasFfmpeg = !!Bun.which("ffmpeg");
-
-test.skipIf(!hasFfmpeg)(
-	"read() serves the exact window at the requested position",
-	async () => {
-		const wav = join(tmpdir(), `podtui-reader-${process.pid}-${Date.now()}.wav`);
-		writeSineWav(wav, 20);
-		const reader = new AudioStreamReader({ url: wav });
-		try {
-			reader.start(5, 1);
-			// Cover targets up to ~5.6s (head must pass the read target).
-			await waitForHead(reader, Math.round(0.6 * SAMPLE_RATE));
-
-			const out = new Float64Array(512);
-
-			// Window at 5.1s: the window ENDS at the target, so out[i] is at
-			// file index 5*SR + round((5.1-5)*SR) - (len-1) + i.
-			expect(reader.read(out, 5.1)).toBe(512);
-			for (let i = 0; i < 512; i++) {
-				const idx =
-					Math.round(5 * SAMPLE_RATE) +
-					Math.round((5.1 - 5) * SAMPLE_RATE) -
-					(out.length - 1) +
-					i;
-				expect(Math.abs(out[i] - expectedAt(idx))).toBeLessThanOrEqual(1);
-			}
-
-			// Window at 5.105s is the same stream shifted by exactly
-			// round(0.005*SR)=221 samples — pins that the target maps to a
-			// precise offset, not "whatever the decode head is at".
-			const later = new Float64Array(512);
-			expect(reader.read(later, 5.105)).toBe(512);
-			for (let i = 0; i <= 512 - 222; i++) {
-				expect(later[i]).toBe(out[i + 221]);
-			}
-		} finally {
-			reader.stop();
-			await Bun.$`rm -f ${wav}`.quiet();
-		}
-	},
-);
-
-test.skipIf(!hasFfmpeg)(
-	"decode keeps up with the player clock at 2x speed",
-	async () => {
-		const wav = join(tmpdir(), `podtui-reader-${process.pid}-${Date.now()}.wav`);
-		writeSineWav(wav, 20);
-		const reader = new AudioStreamReader({ url: wav });
-		try {
-			reader.start(0, 2);
-			// At 2x pacing the head reaches 2.5s after ~1.25s of wall time.
-			// With native-rate pacing it would only be at ~1.25s, and the
-			// window at 2.5s would clamp to the head — content mismatch.
-			await waitForHead(reader, Math.round(2.5 * SAMPLE_RATE));
-
-			const out = new Float64Array(512);
-			expect(reader.read(out, 2.5)).toBe(512);
-			for (let i = 0; i < 512; i++) {
-				const idx =
-					Math.round(2.5 * SAMPLE_RATE) - (out.length - 1) + i;
-				expect(Math.abs(out[i] - expectedAt(idx))).toBeLessThanOrEqual(1);
-			}
-		} finally {
-			reader.stop();
-			await Bun.$`rm -f ${wav}`.quiet();
-		}
-	},
-);
-
-test.skipIf(!hasFfmpeg)(
-	"read() clamps to the nearest samples when the target is beyond the head",
-	async () => {
-		const wav = join(tmpdir(), `podtui-reader-${process.pid}-${Date.now()}.wav`);
-		writeSineWav(wav, 20);
-		const reader = new AudioStreamReader({ url: wav });
-		try {
-			reader.start(0, 1);
-			await waitForHead(reader, Math.round(0.3 * SAMPLE_RATE));
-
-			// Target far beyond the decode head: serve the newest available
-			// window (real sine samples, never zeros or garbage).
-			const out = new Float64Array(512);
-			expect(reader.read(out, 999)).toBe(512);
-			const maxAbs = Math.max(...Array.from(out, Math.abs));
-			expect(maxAbs).toBeGreaterThan(10000);
-			for (const v of out) {
-				expect(Math.abs(v)).toBeLessThanOrEqual(AMP + 1);
-			}
-		} finally {
-			reader.stop();
-			await Bun.$`rm -f ${wav}`.quiet();
-		}
-	},
-);
-
-test.skipIf(!hasFfmpeg)(
-	"sustained render loop: ffmpeg stays alive and decode head maintains a lead over the player",
-	async () => {
-		// Real wall-clock time is required here: this test validates ffmpeg's
-		// actual decode pacing (-readrate + -readrate_initial_burst) against
-		// the platform clock. Deterministic time control cannot reproduce the
-		// race where ffmpeg exits early and the bars freeze — that only
-		// surfaces when a real process writes to a real pipe.
-		//
-		// Simulates the actual render loop: for ~5s of wall time, advance a
-		// simulated player position at 1× realtime and call read() each frame.
-		// The decode head must stay ahead of the player position so read()
-		// always returns 512 samples, and ffmpeg must not exit early (which
-		// would freeze the bars). This test would have caught the
-		// backpressure-pacing failure where ffmpeg decoded all data into the
-		// pipe buffer instantly, exited, and the readLoop stopped.
-		const wav = join(
-			tmpdir(),
-			`podtui-reader-${process.pid}-${Date.now()}.wav`,
-		);
-		writeSineWav(wav, 30);
-		const reader = new AudioStreamReader({ url: wav });
-		try {
-			reader.start(0, 1);
-
-			const FRAME_MS = 33;
-			const DURATION_MS = 5000;
-			const out = new Float64Array(512);
-			let successes = 0;
-			let failures = 0;
-			let minLead = Infinity;
-
-			const start = Date.now();
-			for (let frame = 0; Date.now() - start < DURATION_MS; frame++) {
-				const playerPos = (Date.now() - start) / 1000;
-				const count = reader.read(out, playerPos);
-				if (count === 512) successes++;
-				else failures++;
-
-				// The decode head should stay ahead of the player position.
-				const headPos = reader.samplesWritten / SAMPLE_RATE;
-				const lead = headPos - playerPos;
-				if (frame > 3) minLead = Math.min(minLead, lead);
-
-				await Bun.sleep(FRAME_MS);
-			}
-
-			// ffmpeg must still be running — it must not have exited early.
-			expect(reader.running).toBe(true);
-
-			// The vast majority of frames should return a full window.
-			// A few early failures during ffmpeg startup are acceptable.
-			expect(failures).toBeLessThan(5);
-			expect(successes).toBeGreaterThan(100);
-
-			// The decode head must maintain a positive lead over the player.
-			// Without -readrate_initial_burst, the head would lag behind by
-			// the ffmpeg startup latency and never catch up.
-			expect(minLead).toBeGreaterThan(0);
-		} finally {
-			reader.stop();
-			await Bun.$`rm -f ${wav}`.quiet();
-		}
-	},
-	{ timeout: 15000 },
-);

tests/cover-art.test.ts

@@ -0,0 +1,77 @@
+/**
+ * Cover-art disk-cache contract tests.
+ *
+ * fetchCoverArt downloads each cover ONCE into a persistent per-URL cache;
+ * playback never waits on the network for art it has already fetched. Pins:
+ *
+ * 1. A fetch stores the bytes on disk and returns the cache path.
+ * 2. A second fetch of the same URL returns the cached path WITHOUT hitting
+ *    the server again (request count stays 1).
+ * 3. Concurrent fetches of the same URL share one download (single-flight).
+ * 4. A failed fetch (404) resolves null instead of throwing.
+ *
+ * Served from a local Bun server — no external network dependence. Cache
+ * entries created here are removed afterwards.
+ */
+import { test, expect } from "bun:test";
+import { unlinkSync } from "fs";
+import { cachedCoverPath, fetchCoverArt } from "../src/utils/cover-art";
+
+const FAKE_JPEG = Buffer.from([0xff, 0xd8, 0xff, 0xe0, ...new Array(256).fill(7)]);
+
+test("cover art is fetched once, cached on disk, and shared", async () => {
+	let requests = 0;
+	const server = Bun.serve({
+		port: 0,
+		fetch(req) {
+			requests++;
+			if (new URL(req.url).pathname === "/missing.jpg") {
+				return new Response("nope", { status: 404 });
+			}
+			return new Response(FAKE_JPEG, {
+				headers: { "content-type": "image/jpeg" },
+			});
+		},
+	});
+
+	const url = `http://127.0.0.1:${server.port}/cover.jpg`;
+	const missing = `http://127.0.0.1:${server.port}/missing.jpg`;
+	let cachedPath: string | null = null;
+	try {
+		expect(cachedCoverPath(url)).toBeNull();
+
+		// First fetch: downloads and caches.
+		cachedPath = await fetchCoverArt(url);
+		expect(cachedPath).not.toBeNull();
+		expect(requests).toBe(1);
+		expect(Bun.file(cachedPath!).size).toBe(FAKE_JPEG.byteLength);
+
+		// Second fetch: disk hit, server untouched.
+		expect(await fetchCoverArt(url)).toBe(cachedPath);
+		expect(requests).toBe(1);
+
+		// Single-flight: parallel misses of a fresh URL make ONE request.
+		const shared = `http://127.0.0.1:${server.port}/shared.jpg`;
+		const [a, b, c] = await Promise.all([
+			fetchCoverArt(shared),
+			fetchCoverArt(shared),
+			fetchCoverArt(shared),
+		]);
+		expect(a).not.toBeNull();
+		expect(a).toBe(b);
+		expect(b).toBe(c);
+		if (a) unlinkSync(a);
+
+		// 404 resolves null, never throws.
+		expect(await fetchCoverArt(missing)).toBeNull();
+	} finally {
+		server.stop(true);
+		if (cachedPath) {
+			try {
+				unlinkSync(cachedPath);
+			} catch {
+				/* ignore */
+			}
+		}
+	}
+});

tests/external-pause-reconcile.test.ts

@@ -28,7 +28,14 @@
  * identity bun loads from disk, bypassing the leaked mock.
  */
 import { test, expect, afterAll } from "bun:test";
-import { mkdirSync, mkdtempSync, writeFileSync, rmSync } from "node:fs";
+import {
+	mkdirSync,
+	mkdtempSync,
+	writeFileSync,
+	rmSync,
+	readdirSync,
+	statSync,
+} from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 
@@ -102,9 +109,30 @@ const wavPath = join(tmpdir(), `podtui-extpause-${process.pid}.wav`);
 // loads the real file instead of a leaked mock.module from another test file.
 const { useAudio } = await import("../src/hooks/useAudio?external-pause-test");
 
-/** The pid-derived socket path the backend tells mpv to bind. */
+/**
-function mpvSocket(): string {
+ * The socket path of the LIVE backend daemon in this process. The backend
-	return join(tmpdir(), `podtui-mpv-${process.pid}.sock`);
+ * names sockets per-instance (`podtui-mpv-<pid>-<instance>.sock`), so scan
+ * tmpdir for this pid's sockets and take the newest (the one mpv actually
+ * bound — earlier instances may have been orphaned by a re-spawn).
+ */
+function mpvSocket(): string | null {
+	let newest: string | null = null;
+	let newestMtime = 0;
+	for (const name of readdirSync(tmpdir())) {
+		if (
+			!name.startsWith(`podtui-mpv-${process.pid}-`) ||
+			!name.endsWith(".sock")
+		) {
+			continue;
+		}
+		const candidate = join(tmpdir(), name);
+		const mtime = statSync(candidate).mtimeMs;
+		if (mtime > newestMtime) {
+			newest = candidate;
+			newestMtime = mtime;
+		}
+	}
+	return newest;
 }
 
 /**
@@ -112,6 +140,8 @@ function mpvSocket(): string {
  * media session pauses/resumes mpv without PodTUI's involvement.
  */
 async function mpvCommand(command: unknown[]): Promise<void> {
+	const socket = mpvSocket();
+	if (!socket) throw new Error("backend mpv socket not found");
 	const { promise, resolve, reject } = Promise.withResolvers<void>();
 	let settled = false;
 	const settle = (err: Error | null): void => {
@@ -121,7 +151,7 @@ async function mpvCommand(command: unknown[]): Promise<void> {
 		else resolve();
 	};
 	Bun.connect({
-		unix: mpvSocket(),
+		unix: socket,
 		socket: {
 			open(s) {
 				s.write(JSON.stringify({ command }) + "\n");
@@ -213,8 +243,16 @@ afterAll(async () => {
 	} catch {
 		/* best-effort */
 	}
+	// The resident daemon survives stop() by design — quit it so test
+	// workers don't leak idle mpv processes.
 	try {
-		rmSync(mpvSocket(), { force: true });
+		await mpvCommand(["quit"]);
+	} catch {
+		/* best-effort */
+	}
+	try {
+		const socket = mpvSocket();
+		if (socket) rmSync(socket, { force: true });
 	} catch {
 		/* best-effort */
 	}

tests/visualizer-store.test.ts

@@ -15,7 +15,7 @@
  *
  * Uses a self-generated local WAV (a frequency chirp, so different playback
  * positions produce measurably different bar output) and the real ffmpeg +
- * native cavacore pipeline, mirroring audio-stream-reader.test.ts.
+ * native cavacore pipeline, mirroring audio-pcm-cache.test.ts.
  *
  * Timing note: this is an integration test of the store's real timers — the
  * unload path is a genuine `setTimeout` in the store, and bun 1.3.8 ships no