perf(metadata): bound bulk re-enrich concurrency

A large batch selection fired hundreds of simultaneous requests (each also
enqueuing a worker job). Run them in batches of BULK_CONCURRENCY.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/components/player/RadioController.tsx

@@ -8,6 +8,11 @@ import { pickToEntry } from '../../lib/radio';
 // the end of the queue.
 const LOOKAHEAD = 3;
 
+// Only the most recent tracks are sent as "don't repeat these" — bounding the
+// request so a long radio session doesn't ship an ever-growing exclude list
+// (and a huge NOT IN on the server). Recent-repeat avoidance is what matters.
+const EXCLUDE_WINDOW = 150;
+
 /**
  * Headless controller: while a radio drives the queue, top it up as it drains
  * (§6.5 / B6 infinite feed). Mounted once in AppShell. A failed prefetch just
@@ -34,7 +39,7 @@ export function RadioController() {
           fromLikes: radio.fromLikes,
           exploration: radio.exploration,
           count: 10,
-          excludeIds: entries.map((e) => e.trackId),
+          excludeIds: entries.slice(-EXCLUDE_WINDOW).map((e) => e.trackId),
         }).unwrap();
         if (res.picks.length > 0) {
           dispatch(appendToQueue(res.picks.map(pickToEntry)));

src/features/metadata-editor/MetadataEditorPage.tsx

@@ -65,6 +65,23 @@ function fieldStyle(): React.CSSProperties {
   return { width: '100%' };
 }
 
+// Cap how many bulk metadata ops run at once — a large selection would otherwise
+// fire hundreds of simultaneous requests (each also spins up a worker enqueue).
+const BULK_CONCURRENCY = 6;
+
+async function settleInBatches<T>(
+  items: T[],
+  limit: number,
+  op: (item: T) => Promise<unknown>,
+): Promise<PromiseSettledResult<unknown>[]> {
+  const results: PromiseSettledResult<unknown>[] = [];
+  for (let i = 0; i < items.length; i += limit) {
+    const batch = items.slice(i, i + limit);
+    results.push(...(await Promise.allSettled(batch.map(op))));
+  }
+  return results;
+}
+
 /**
  * `/tracks/:trackId/metadata` — A7 metadata editor: manual edits + AcoustID
  * match picker with a current-vs-proposed diff. `/metadata/batch` operates on a
@@ -723,7 +740,7 @@ function BatchEditor() {
     setBusy(true);
     setResult(null);
     const ids = [...selected];
-    const outcomes = await Promise.allSettled(ids.map(op));
+    const outcomes = await settleInBatches(ids, BULK_CONCURRENCY, op);
     const ok = outcomes.filter((o) => o.status === 'fulfilled').length;
     setResult({ ok, fail: ids.length - ok });
     setBusy(false);

src/hooks/useAudioPlayer.ts

@@ -31,38 +31,43 @@ export function useAudioPlayer() {
   // on demand; a cache miss transparently falls back to the original.
   const { data: settings } = useGetSettingsQuery();
   const streamQuality = settings?.streamQuality;
-  const isSetup = useRef(false);
-  // `ended` is registered once below; read the latest loop flag through a ref
-  // so the listener doesn't need to be re-bound on every queue change.
+  // `ended` reads the latest loop flag through a ref so the listener doesn't
+  // need re-binding on every queue change.
   const loopRef = useRef(queue.loop);
   loopRef.current = queue.loop;
+  // The track id the current <audio>.src points at — lets us tell a real track
+  // change (start at 0) from a same-track URL change (preserve position).
+  const loadedTrackRef = useRef<string | null>(null);
 
   useEffect(() => {
-    if (isSetup.current) return;
-    isSetup.current = true;
-
     const audio = getAudio();
-
-    audio.addEventListener('timeupdate', () => {
-      dispatch(setPosition(audio.currentTime));
-    });
-    audio.addEventListener('durationchange', () => {
-      dispatch(setDuration(audio.duration || 0));
-    });
-    audio.addEventListener('ended', () => {
+    // Named handlers + cleanup so a remount (React StrictMode, or the hook
+    // mounting elsewhere) can't leave duplicate listeners double-dispatching.
+    const onTime = () => dispatch(setPosition(audio.currentTime));
+    const onDuration = () => dispatch(setDuration(audio.duration || 0));
+    const onEnded = () => {
       if (loopRef.current) {
         audio.currentTime = 0;
         void audio.play();
       } else {
         dispatch(nextTrack());
       }
-    });
-    audio.addEventListener('pause', () => {
-      dispatch(pause());
-    });
-    audio.addEventListener('play', () => {
-      dispatch(resume());
-    });
+    };
+    const onPause = () => dispatch(pause());
+    const onPlay = () => dispatch(resume());
+
+    audio.addEventListener('timeupdate', onTime);
+    audio.addEventListener('durationchange', onDuration);
+    audio.addEventListener('ended', onEnded);
+    audio.addEventListener('pause', onPause);
+    audio.addEventListener('play', onPlay);
+    return () => {
+      audio.removeEventListener('timeupdate', onTime);
+      audio.removeEventListener('durationchange', onDuration);
+      audio.removeEventListener('ended', onEnded);
+      audio.removeEventListener('pause', onPause);
+      audio.removeEventListener('play', onPlay);
+    };
   }, [dispatch]);
 
   useEffect(() => {
@@ -70,8 +75,20 @@ export function useAudioPlayer() {
     const audio = getAudio();
     const url = getStreamUrl(player.currentTrackId, accessToken, streamQuality);
     if (audio.src !== url) {
+      // Same track, new URL (quality changed, or the access token was refreshed
+      // mid-play) → keep the playback position instead of restarting from 0.
+      const sameTrack = loadedTrackRef.current === player.currentTrackId;
+      const resumeAt = sameTrack ? audio.currentTime : 0;
       audio.src = url;
       audio.load();
+      loadedTrackRef.current = player.currentTrackId;
+      if (resumeAt > 0) {
+        const onMeta = () => {
+          audio.currentTime = resumeAt;
+          audio.removeEventListener('loadedmetadata', onMeta);
+        };
+        audio.addEventListener('loadedmetadata', onMeta);
+      }
     }
     if (player.isPlaying) {
       void audio.play();

src/store/slices/queue.ts

@@ -38,6 +38,12 @@ export interface QueueState {
   radio: RadioContext | null;
 }
 
+// An infinite radio keeps appending, so cap the backlog: once the queue grows
+// past QUEUE_CAP, drop the oldest *already-played* entries (never the current
+// track or the look-ahead), keeping at least KEEP_BEHIND for prev-navigation.
+const QUEUE_CAP = 300;
+const KEEP_BEHIND = 50;
+
 export const queueInitialState: QueueState = {
   entries: [],
   currentIndex: -1,
@@ -83,6 +89,17 @@ export const queueSlice = createSlice({
     },
     appendToQueue(state, action: PayloadAction<QueueEntry[]>) {
       state.entries.push(...action.payload);
+      if (state.entries.length > QUEUE_CAP) {
+        // Only trim entries safely behind the current one.
+        const drop = Math.min(
+          state.entries.length - QUEUE_CAP,
+          Math.max(0, state.currentIndex - KEEP_BEHIND),
+        );
+        if (drop > 0) {
+          state.entries.splice(0, drop);
+          state.currentIndex -= drop;
+        }
+      }
     },
     setExploration(state, action: PayloadAction<number>) {
       if (state.radio) state.radio.exploration = action.payload;