Merge pull request 'release v2026.05.12.1: Discover surface + nav fixes + cache hygiene' (#42) from dev into main

Two unrelated issues, batched.

Full-player kebab → "Go to album/artist" still crashed with
_debugCheckDuplicatedPageKeys despite the prior onBeforeNavigate
fix. Cause: pop() and push() ran in the same frame, so go_router's
page-key reservation table briefly contained both /now-playing AND
the destination shell-child, tripping the duplicate-key assert.

Refactor: replace onBeforeNavigate with onNavigate(path), where the
host receives the path AFTER the sheet pops and owns the
navigation entirely. The full player wires:
  onNavigate: (path) async {
    await Navigator.of(context).maybePop();
    if (context.mounted) GoRouter.of(context).push(path);
  }
Awaiting the pop guarantees /now-playing is fully gone from the
navigator's page list before the push starts.

Mini player + track rows + everywhere else use the default (no
onNavigate) path that does context.push(path) inline — they're
already inside the ShellRoute, no race possible.

Restored alwaysRefresh: true on artistAlbumsProvider. Dropping it
in the cache-loop fix had a side effect: if drift's cachedAlbums
held only a subset of an artist's albums (user previously visited
just one album by them), the artist detail page rendered that
partial list forever — provider only fetched on empty drift, never
on partial drift. The metadata prefetcher only mass-warms
artistProvider (single row), so re-enabling SWR on artistAlbums
won't recreate the storm.

flutter_client/lib/app.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import 'cache/metadata_prefetcher.dart';
 import 'cache/prefetcher.dart';
 import 'cache/sync_controller.dart';
 import 'shared/routing.dart';
@@ -27,6 +28,11 @@ class _MinstrelAppState extends ConsumerState<MinstrelApp> {
       // ignore: unawaited_futures
       ref.read(syncControllerProvider.notifier).sync();
       ref.read(prefetcherProvider);
+      // Metadata prefetcher: when /api/home returns, fire background
+      // albumProvider/artistProvider reads for the top-N items in
+      // each section so subsequent taps are drift hits, not network
+      // round trips.
+      ref.read(metadataPrefetcherProvider);
     });
   }
 

flutter_client/lib/cache/adapters.dart

@@ -88,6 +88,12 @@ extension TrackRefDriftWrite on TrackRef {
 extension CachedPlaylistAdapter on CachedPlaylist {
   /// `ownerUsername` is server-derived; cache stores the userId only.
   /// Pass empty unless a join supplies it.
+  /// `coverUrl` is reconstructed deterministically from the playlist
+  /// id — the server serves the cached collage at this path
+  /// (handleGetPlaylistCover). Mirrors the album-cover trick. When
+  /// the server hasn't built a collage yet (system playlists with no
+  /// tracks at build time), the endpoint 404s and PlaylistCard's
+  /// ServerImage falls back to its slate placeholder.
   Playlist toRef({String ownerUsername = ''}) => Playlist(
         id: id,
         userId: userId,
@@ -96,7 +102,7 @@ extension CachedPlaylistAdapter on CachedPlaylist {
         isPublic: isPublic,
         systemVariant: systemVariant,
         trackCount: trackCount,
-        coverUrl: '', // server-derived; cache doesn't persist
+        coverUrl: '/api/playlists/$id/cover',
         ownerUsername: ownerUsername,
         createdAt: '',
         updatedAt: '',

flutter_client/lib/cache/audio_cache_manager.dart

@@ -83,6 +83,27 @@ class AudioCacheManager {
     return path;
   }
 
+  /// Registers a file already on disk in the cache index. Intended for
+  /// the streaming path (LockCachingAudioSource) which writes the file
+  /// itself; we need an index row so eviction can find and delete it
+  /// when usage exceeds the cap. `source` defaults to incidental so
+  /// stream-cached tracks are first to be evicted.
+  Future<void> registerStreamCache(
+    String trackId,
+    String path,
+    int sizeBytes, {
+    CacheSource source = CacheSource.incidental,
+  }) async {
+    await _db.into(_db.audioCacheIndex).insertOnConflictUpdate(
+          AudioCacheIndexCompanion.insert(
+            trackId: trackId,
+            path: path,
+            sizeBytes: sizeBytes,
+            source: source,
+          ),
+        );
+  }
+
   /// Removes a track from the index AND deletes the file.
   Future<void> unpin(String trackId) async {
     final row = await (_db.select(_db.audioCacheIndex)
@@ -96,13 +117,25 @@ class AudioCacheManager {
         .go();
   }
 
-  /// Total bytes used by the cache.
+  /// Total bytes used by the cache. Walks the cache directory directly
+  /// instead of summing the index, because the streaming-as-you-play
+  /// path (audio_handler's LockCachingAudioSource) writes files
+  /// without registering an index row. The index sum would always
+  /// understate (often to zero) for users who only stream.
   Future<int> usageBytes() async {
-    final result = await _db.customSelect(
+    final dir = Directory(await _tracksDir());
-      'SELECT COALESCE(SUM(size_bytes), 0) AS total FROM audio_cache_index',
+    if (!await dir.exists()) return 0;
-      readsFrom: {_db.audioCacheIndex},
+    var total = 0;
-    ).getSingle();
+    await for (final entity in dir.list(followLinks: false)) {
-    return result.read<int>('total');
+      if (entity is File) {
+        try {
+          total += await entity.length();
+        } catch (_) {
+          // Race against concurrent writes / deletes — just skip.
+        }
+      }
+    }
+    return total;
   }
 
   /// Evicts files until usage ≤ targetBytes. Eviction order:

flutter_client/lib/cache/cache_first.dart

@@ -19,6 +19,10 @@ import 'dart:async';
 
 import 'package:flutter/foundation.dart' show debugPrint;
 
+// `tag` parameter is preserved for future ad-hoc instrumentation.
+// Normal operation only logs failure paths so the per-screen log
+// noise stays low.
+
 /// Wraps the watch + cold-cache fallback pattern. Generic over:
 ///   D — the drift row type (or TypedResult for joins)
 ///   T — the result type the caller wants (e.g. `List<ArtistRef>`)
@@ -43,13 +47,9 @@ Stream<T> cacheFirst<D, T>({
   // refresh for this stream subscription, so we don't fire one on every
   // drift re-emission (otherwise the populate cycles forever).
   var revalidated = false;
-  void log(String msg) {
-    if (tag != null) debugPrint('cacheFirst[$tag]: $msg');
-  }
 
   await for (final rows in driftStream) {
     if (rows.isNotEmpty) {
-      log('drift hit (${rows.length} rows)');
       yield toResult(rows);
       // Stale-while-revalidate: yield cache immediately, then kick off
       // a REST refresh in the background. Drift watch() picks up the
@@ -62,20 +62,18 @@ Stream<T> cacheFirst<D, T>({
       }
       continue;
     }
-    log('drift miss; checking connectivity');
     if (await isOnline()) {
-      log('online; calling fetchAndPopulate');
       try {
         await fetchAndPopulate();
-        log('fetchAndPopulate done; awaiting drift re-emit');
         // The drift watch() stream re-emits with the populated rows on
         // the next loop iteration. Don't yield here.
       } catch (e, st) {
-        log('fetchAndPopulate failed: $e\n$st');
+        if (tag != null) {
+          debugPrint('cacheFirst[$tag]: fetchAndPopulate failed: $e\n$st');
+        }
         yield toResult(rows); // empty result; caller surfaces error
       }
     } else {
-      log('offline; yielding empty');
       yield toResult(rows); // empty result; offline
     }
   }

flutter_client/lib/cache/metadata_prefetcher.dart

@@ -0,0 +1,74 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../library/library_providers.dart';
+import '../models/home_data.dart';
+
+/// Pre-warms the drift cache for likely-tap targets. Conservative on
+/// purpose: only warms artistProvider rows (single row, single round
+/// trip per id) and only ever fires once per id per session. Album
+/// detail is NOT prewarmed — the albumProvider auto-fetches its track
+/// list when missing, and pre-warming N albums fans out N parallel
+/// "fetch tracks" round trips that compete with the user's actual
+/// playback request for bandwidth.
+class MetadataPrefetcher {
+  MetadataPrefetcher(this._ref) {
+    _ref.listen<AsyncValue<HomeData>>(homeProvider, (_, next) {
+      next.whenData(_warmHome);
+    });
+  }
+
+  final Ref _ref;
+
+  /// Per-session dedupe so re-rendering a screen (every UI rebuild
+  /// fires the data: callback) doesn't trigger N more fetches for
+  /// ids we've already warmed.
+  final Set<String> _warmedArtists = {};
+
+  /// Cap per section. Covers what fits on screen without scrolling.
+  static const _topN = 8;
+
+  /// Pre-warm artists. Albums are intentionally not pre-warmed —
+  /// see class comment.
+  void warmArtists(Iterable<String> ids) {
+    var n = 0;
+    for (final id in ids) {
+      if (id.isEmpty) continue;
+      if (!_warmedArtists.add(id)) continue; // already warmed
+      if (n++ >= _topN) break;
+      _swallow(_ref.read(artistProvider(id).future));
+    }
+  }
+
+  void _warmHome(HomeData h) {
+    final artistIds = <String>{};
+    for (final a in h.recentlyAddedAlbums.take(_topN)) {
+      if (a.artistId.isNotEmpty) artistIds.add(a.artistId);
+    }
+    for (final a in h.rediscoverAlbums.take(_topN)) {
+      if (a.artistId.isNotEmpty) artistIds.add(a.artistId);
+    }
+    for (final ar in h.rediscoverArtists.take(_topN)) {
+      if (ar.id.isNotEmpty) artistIds.add(ar.id);
+    }
+    for (final ar in h.lastPlayedArtists.take(_topN)) {
+      if (ar.id.isNotEmpty) artistIds.add(ar.id);
+    }
+    for (final t in h.mostPlayedTracks.take(_topN)) {
+      if (t.artistId.isNotEmpty) artistIds.add(t.artistId);
+    }
+    warmArtists(artistIds);
+  }
+
+  /// Discards the return value and any error from a fire-and-forget
+  /// provider read. We don't care about the value here — we only want
+  /// the side effect of writing drift.
+  void _swallow(Future<Object?> f) {
+    f.then<void>((_) {}).onError((_, __) {});
+  }
+}
+
+/// Read once at app start to activate the prefetcher (e.g. wire it
+/// from a top-level Consumer or main.dart container override).
+final metadataPrefetcherProvider = Provider<MetadataPrefetcher>((ref) {
+  return MetadataPrefetcher(ref);
+});

flutter_client/lib/library/artist_detail_screen.dart

@@ -92,10 +92,31 @@ class ArtistDetailScreen extends ConsumerWidget {
                 child: IconButton(
                   icon: Icon(Icons.play_arrow, color: fs.parchment),
                   onPressed: () async {
-                    final tracks = await ref.read(artistTracksProvider(id).future);
+                    try {
-                    if (tracks.isEmpty) return;
+                      final tracks =
-                    final shuffled = [...tracks]..shuffle();
+                          await ref.read(artistTracksProvider(id).future);
-                    ref.read(playerActionsProvider).playTracks(shuffled);
+                      if (tracks.isEmpty) {
+                        if (context.mounted) {
+                          ScaffoldMessenger.of(context).showSnackBar(
+                            const SnackBar(
+                                content: Text(
+                                    'No tracks found for this artist yet.')),
+                          );
+                        }
+                        return;
+                      }
+                      final shuffled = [...tracks]..shuffle();
+                      await ref
+                          .read(playerActionsProvider)
+                          .playTracks(shuffled);
+                    } catch (e) {
+                      debugPrint('artist_detail: play failed: $e');
+                      if (context.mounted) {
+                        ScaffoldMessenger.of(context).showSnackBar(
+                          SnackBar(content: Text("Couldn't start playback: $e")),
+                        );
+                      }
+                    }
                   },
                 ),
               ),
@@ -109,7 +130,8 @@ class ArtistDetailScreen extends ConsumerWidget {
           albums.when(
             error: (e, _) => Center(child: Text('$e', style: TextStyle(color: fs.error))),
             loading: () => const Padding(padding: EdgeInsets.all(16), child: Center(child: CircularProgressIndicator())),
-            data: (list) => LayoutBuilder(builder: (ctx, constraints) {
+            data: (list) {
+              return LayoutBuilder(builder: (ctx, constraints) {
               const cols = 3;
               const sidePad = 8.0;
               const gap = 8.0;
@@ -117,10 +139,11 @@ class ArtistDetailScreen extends ConsumerWidget {
                   (constraints.maxWidth - sidePad * 2 - gap * (cols - 1)) /
                       cols;
               // Card content: cover (cellW - 16) + 8 + title (≤2 lines
-              // ≈ 36) + small fudge. Artist line is suppressed in this
+              // ≈ 36) + slack. Artist line is suppressed in this
               // grid (showArtist: false) since the page header already
-              // names the artist.
+              // names the artist. Slack is generous on purpose — line-
-              final cellH = (cellW - 16) + 8 + 36 + 4;
+              // height variations would otherwise overflow by 1px.
+              final cellH = (cellW - 16) + 8 + 36 + 8;
               return GridView.builder(
                 shrinkWrap: true,
                 physics: const NeverScrollableScrollPhysics(),
@@ -144,7 +167,8 @@ class ArtistDetailScreen extends ConsumerWidget {
                   );
                 },
               );
-            }),
+            });
+            },
           ),
         ]);
 }

flutter_client/lib/library/home_screen.dart

@@ -135,7 +135,16 @@ List<_PlaylistRowItem> _buildPlaylistsRow(
       ? _RealPlaylist(forYou)
       : _PlaceholderPlaylist('For You', _variantFor('for-you', status)));
 
-  // Slots 2-4: Songs-like (real first, padded to 3).
+  // Slot 2: Discover. Server emits this with system_variant='discover'
+  // when the recommendation engine has eligible tracks; before then,
+  // show a placeholder in the same "building/pending" state machine
+  // as For-You.
+  final discover = findFirst((p) => p.systemVariant == 'discover');
+  out.add(discover != null
+      ? _RealPlaylist(discover)
+      : _PlaceholderPlaylist('Discover', _variantFor('discover', status)));
+
+  // Slots 3-5: Songs-like (real first, padded to 3).
   final songsLike = ownedAll
       .where((p) => p.systemVariant == 'songs_like_artist')
       .take(3)

flutter_client/lib/library/library_providers.dart

@@ -66,9 +66,10 @@ final artistProvider =
     isOnline: () async => (await ref
         .read(connectivityProvider.future)
         .timeout(const Duration(seconds: 3), onTimeout: () => true)),
-    // SWR: yield cache instantly on hit, refresh in the background so
+    // No alwaysRefresh: artist rows don't change frequently, and the
-    // the row catches up to server state without making the user wait.
+    // metadata prefetcher creates many subscriptions in parallel —
-    alwaysRefresh: true,
+    // each silently re-fetching once would saturate the request
+    // pipeline behind the user's actual playback request.
     tag: 'artist($id)',
   );
 });
@@ -100,6 +101,13 @@ final artistAlbumsProvider =
     isOnline: () async => (await ref
         .read(connectivityProvider.future)
         .timeout(const Duration(seconds: 3), onTimeout: () => true)),
+    // SWR: re-fetch the full album list on every visit. Without this,
+    // a previously-incomplete drift cache (e.g. user had only opened
+    // one album by this artist, so cachedAlbums had just that row)
+    // would render forever as a partial list. The prefetcher only
+    // warms artistProvider (single row), so this provider isn't
+    // mass-instantiated and the storm risk that motivated dropping
+    // alwaysRefresh elsewhere doesn't apply here.
     alwaysRefresh: true,
     tag: 'artistAlbums($artistId)',
   );
@@ -137,7 +145,6 @@ final artistTracksProvider =
     isOnline: () async => (await ref
         .read(connectivityProvider.future)
         .timeout(const Duration(seconds: 3), onTimeout: () => true)),
-    alwaysRefresh: true,
     tag: 'artistTracks($artistId)',
   );
 });
@@ -169,10 +176,7 @@ final albumProvider = StreamProvider.family<
   // Once-per-subscription guard so we don't re-fetch in a loop if the
   // server genuinely returns zero tracks (or if the fetch fails).
   var fetchAttempted = false;
-  // SWR revalidation guard — fire one background refresh per
+  // (revalidated flag removed; see SWR note below the yield.)
-  // subscription on the first complete cache hit, so the displayed
-  // data catches up to server state without making the user wait.
-  var revalidated = false;
 
   Future<bool> isOnline() async {
     try {
@@ -191,11 +195,9 @@ final albumProvider = StreamProvider.family<
   Future<bool> fetchAndPopulate() async {
     try {
       final api = await ref.read(libraryApiProvider.future);
-      debugPrint('albumProvider($albumId): calling getAlbum');
       final fresh = await api
           .getAlbum(albumId)
           .timeout(const Duration(seconds: 10));
-      debugPrint('albumProvider($albumId): got ${fresh.tracks.length} tracks, writing to drift');
       // Collect every artist mentioned by the album + its tracks so
       // the JOINs that drive both the album header and the track rows
       // have something to bind to. Without this, drift returns null
@@ -228,7 +230,6 @@ final albumProvider = StreamProvider.family<
         b.insertAllOnConflictUpdate(db.cachedTracks,
             fresh.tracks.map((t) => t.toDrift()).toList());
       });
-      debugPrint('albumProvider($albumId): drift write done; awaiting watch re-emit');
       return true;
     } catch (e, st) {
       debugPrint('albumProvider($albumId): cold-cache fetch failed: $e\n$st');
@@ -239,7 +240,6 @@ final albumProvider = StreamProvider.family<
   await for (final albumRows in albumQuery.watch()) {
     // Case 1: no album row at all → cold-fetch.
     if (albumRows.isEmpty) {
-      debugPrint('albumProvider($albumId): drift miss, attempting cold-cache fetch');
       if (fetchAttempted) {
         // Already tried and got nothing back.
         yield (
@@ -249,10 +249,7 @@ final albumProvider = StreamProvider.family<
         continue;
       }
       fetchAttempted = true;
-      final online = await isOnline();
+      if (!await isOnline()) {
-      debugPrint('albumProvider($albumId): online=$online');
-      if (!online) {
-        debugPrint('albumProvider($albumId): offline, yielding empty');
         yield (
           album: const AlbumRef(id: '', title: '', artistId: ''),
           tracks: const <TrackRef>[],
@@ -269,7 +266,6 @@ final albumProvider = StreamProvider.family<
       // On success, drift watch re-emits with rows; loop continues.
       continue;
     }
-    debugPrint('albumProvider($albumId): drift hit (${albumRows.length} rows)');
 
     final albumRow = albumRows.first;
     final album = albumRow.readTable(db.cachedAlbums).toRef(
@@ -284,7 +280,6 @@ final albumProvider = StreamProvider.family<
     // fetchAndPopulate so the album becomes complete; drift watch
     // re-emits and we land in the populated branch on the next pass.
     if (trackRows.isEmpty && !fetchAttempted) {
-      debugPrint('albumProvider($albumId): album hit but no tracks; fetching');
       fetchAttempted = true;
       if (await isOnline()) {
         final ok = await fetchAndPopulate();
@@ -303,15 +298,13 @@ final albumProvider = StreamProvider.family<
       );
     }).toList();
 
-    // SWR: first complete cache hit triggers one background refresh
+    // Note: NO SWR here on purpose. Prior code kicked a background
-    // so we don't show stale data indefinitely. Drift watch re-emits
+    // refresh on every first cache hit, which combined with the
-    // on success and the next iteration yields the fresh data.
+    // metadata prefetcher meant every prewarmed album id triggered
-    if (!revalidated && trackRows.isNotEmpty) {
+    // an extra fetch even when drift was already populated. Tracks
-      revalidated = true;
+    // and album metadata don't change on the same timescale as
-      if (await isOnline()) {
+    // playlists; a stale read is fine until the user invalidates
-        unawaited(fetchAndPopulate());
+    // (pull-to-refresh) or the album is genuinely re-fetched.
-      }
-    }
 
     yield (album: album, tracks: tracks);
   }

flutter_client/lib/library/library_screen.dart

@@ -5,6 +5,7 @@ import 'package:go_router/go_router.dart';
 import '../api/endpoints/library_lists.dart';
 import '../api/endpoints/likes.dart';
 import '../api/endpoints/me.dart';
+import '../cache/metadata_prefetcher.dart';
 import '../library/library_providers.dart' show dioProvider;
 import '../models/album.dart';
 import '../models/artist.dart';
@@ -207,7 +208,12 @@ class _ArtistsTab extends ConsumerWidget {
     return ref.watch(_libraryArtistsProvider).when(
           loading: () => const Center(child: CircularProgressIndicator()),
           error: (e, _) => Center(child: Text('$e', style: TextStyle(color: fs.error))),
-          data: (page) => page.items.isEmpty
+          data: (page) {
+            // Warm details for the first screenful so taps are instant.
+            ref
+                .read(metadataPrefetcherProvider)
+                .warmArtists(page.items.map((a) => a.id));
+            return page.items.isEmpty
               ? Center(child: Text("No artists yet — scan a library folder via the server's config.", style: TextStyle(color: fs.ash), textAlign: TextAlign.center))
               : RefreshIndicator(
                   onRefresh: () async {
@@ -247,7 +253,8 @@ class _ArtistsTab extends ConsumerWidget {
                       },
                     ),
                   ),
-                ),
+                );
+          },
         );
   }
 }
@@ -261,7 +268,8 @@ class _AlbumsTab extends ConsumerWidget {
     return ref.watch(_libraryAlbumsProvider).when(
           loading: () => const Center(child: CircularProgressIndicator()),
           error: (e, _) => Center(child: Text('$e', style: TextStyle(color: fs.error))),
-          data: (page) => page.items.isEmpty
+          data: (page) {
+            return page.items.isEmpty
               ? Center(child: Text("No albums yet — scan a library folder via the server's config.", style: TextStyle(color: fs.ash), textAlign: TextAlign.center))
               : RefreshIndicator(
                   onRefresh: () async {
@@ -280,8 +288,11 @@ class _AlbumsTab extends ConsumerWidget {
                             gap * (cols - 1)) /
                         cols;
                     // cover (cellW - 16) + gap (8) + 2-line title (~36)
-                    // + artist line (~16) + small fudge.
+                    // + artist line (~16) + slack. Slack is generous on
-                    final cellH = (cellW - 16) + 8 + 36 + 16 + 4;
+                    // purpose — line-height + font scaling variations
+                    // would otherwise overflow the cell by a pixel
+                    // (logged as a noisy RenderFlex warning).
+                    final cellH = (cellW - 16) + 8 + 36 + 16 + 8;
                     return NotificationListener<ScrollNotification>(
                       onNotification: (n) {
                         if (n.metrics.pixels >=
@@ -315,7 +326,8 @@ class _AlbumsTab extends ConsumerWidget {
                       ),
                     );
                   }),
-                ),
+                );
+          },
         );
   }
 }

flutter_client/lib/player/audio_handler.dart

@@ -12,12 +12,27 @@ import 'album_cover_cache.dart';
 
 class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandler {
   MinstrelAudioHandler() {
-    _player.playbackEventStream.listen(_broadcastState);
+    _player.playbackEventStream.listen(
+      _broadcastState,
+      // ExoPlayer surfaces stream errors (404, premature EOS, decoder
+      // failure, network drop) here. Without an error sink, the
+      // player just goes quiet — exactly the "starts then stops"
+      // symptom we hit.
+      onError: (Object e, StackTrace st) {
+        debugPrint('audio_handler: playbackEventStream error: $e\n$st');
+      },
+    );
     _player.currentIndexStream.listen(_onCurrentIndexChanged);
     // Re-broadcast on shuffle/repeat changes so the PlaybackState's
     // shuffleMode + repeatMode fields stay current for UI subscribers.
     _player.shuffleModeEnabledStream.listen((_) => _broadcastState(null));
     _player.loopModeStream.listen((_) => _broadcastState(null));
+    // Watch buffered-position so we can register stream-cached files
+    // in the audio cache index once they're fully downloaded. Without
+    // this, files written by LockCachingAudioSource never appear in
+    // the index and the eviction loop can't reclaim them.
+    _player.bufferedPositionStream
+        .listen((_) => unawaited(_maybeRegisterStreamCache()));
   }
 
   final AudioPlayer _player = AudioPlayer();
@@ -26,6 +41,33 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
   AlbumCoverCache? _coverCache;
   AudioCacheManager? _audioCacheManager;
 
+  /// Trackers to dedupe registration — once we've inserted an index row
+  /// for a trackId, don't repeat the work on every buffered-position
+  /// emit. Cleared on dispose only; surviving across queue rebuilds is
+  /// fine because the index is itself the source of truth.
+  final Set<String> _streamCacheRegistered = {};
+
+  /// Cached on first use so we don't hit the platform channel every
+  /// time the buffered-position stream emits (~200ms cadence).
+  String? _cacheDirPath;
+
+  /// True while _fillRemainingSources is doing backward-fill inserts
+  /// at index 0..initialIndex-1. Each insert shifts the player's
+  /// currentIndex (it tracks the actively-playing source through
+  /// list mutations), and the resulting _onCurrentIndexChanged
+  /// callbacks would push the wrong MediaItem onto the stream
+  /// (queue.value[shifted_idx] != actively-playing track). When
+  /// the fill completes, currentIndex == initialIndex, mediaItem
+  /// is already correct, and we re-enable normal listener behavior.
+  bool _suppressIndexUpdates = false;
+
+  /// Increments on every setQueueFromTracks call. The background
+  /// fill task captures the value at start and bails if the live
+  /// counter has moved on — without this, a stale fill will keep
+  /// addAudioSource'ing tracks from the previous playlist into the
+  /// new queue, leaving the player "locked" to a corrupted state.
+  int _queueGeneration = 0;
+
   /// Volume stream for UI subscribers. Mirrors the just_audio player's
   /// volume directly; set via setVolume(double).
   Stream<double> get volumeStream => _player.volumeStream;
@@ -49,32 +91,86 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
     _token = token;
     if (coverCache != null) _coverCache = coverCache;
     if (audioCacheManager != null) _audioCacheManager = audioCacheManager;
-    debugPrint('audio_handler.configure: baseUrl="$baseUrl" '
-        'tokenPresent=${token != null && token.isNotEmpty} '
-        'coverCachePresent=${_coverCache != null} '
-        'audioCachePresent=${_audioCacheManager != null}');
   }
 
   Future<void> setQueueFromTracks(List<TrackRef> tracks, {int initialIndex = 0}) async {
+    if (tracks.isEmpty) return;
+    final clampedInitial = initialIndex.clamp(0, tracks.length - 1);
+
+    // Bump the generation FIRST. Any in-flight _fillRemainingSources
+    // from a previous play will see the mismatch on its next gen
+    // check and stop calling player mutations — important so a stale
+    // fill doesn't append old-playlist tracks into the new queue.
+    final myGen = ++_queueGeneration;
+    // Reset suppress flag in case a prior backward-fill bailed on
+    // gen check before reaching its `finally`.
+    _suppressIndexUpdates = false;
+
+    // Populate the visible queue + current mediaItem immediately so
+    // the player UI reflects the user's tap before any source has
+    // been built. Source list at the just_audio layer fills in
+    // asynchronously below.
     final items = tracks.map(_toMediaItem).toList();
     queue.add(items);
-    if (items.isNotEmpty) {
+    mediaItem.add(items[clampedInitial]);
-      mediaItem.add(items[initialIndex.clamp(0, items.length - 1)]);
+
+    // Fast path: build only the initial source so the player can
+    // start. Remaining sources stream in via _fillRemainingSources()
+    // in the background — addAudioSource for next/auto-advance
+    // tracks, insertAudioSource for skipPrev tracks.
+    final initial = await _buildAudioSource(tracks[clampedInitial]);
+    if (myGen != _queueGeneration) {
+      debugPrint('audio_handler: superseded before setAudioSources (gen=$myGen)');
+      return;
     }
 
-    debugPrint('audio_handler.setQueueFromTracks: '
+    await _player.setAudioSources([initial], initialIndex: 0);
-        '_baseUrl="$_baseUrl" trackCount=${tracks.length}');
-    final sources = await Future.wait(tracks.map(_buildAudioSource));
 
-    await _player.setAudioSources(
-      sources,
-      initialIndex: initialIndex,
-    );
-
-    // Kick the cover fetch for the initial item — async, doesn't block
-    // playback. Subsequent track changes are handled by the
-    // currentIndexStream listener.
     unawaited(_loadArtForCurrentItem());
+    unawaited(_fillRemainingSources(tracks, clampedInitial, myGen));
+  }
+
+  /// Background fill of the rest of the just_audio source list after
+  /// the initial source is playing. Forward direction first (most
+  /// common skipNext target). Backward inserts shift the player's
+  /// currentIndex; we suppress _onCurrentIndexChanged side effects
+  /// for those so the mediaItem stream doesn't bounce to the wrong
+  /// queue entry.
+  ///
+  /// `gen` is the queue generation captured when this fill started.
+  /// Every loop iteration checks against _queueGeneration; if a
+  /// newer setQueueFromTracks has run (user tapped play on something
+  /// else), bail immediately so we don't pollute the new queue with
+  /// addAudioSource calls from this stale fill.
+  Future<void> _fillRemainingSources(
+      List<TrackRef> tracks, int initialIndex, int gen) async {
+    for (var i = initialIndex + 1; i < tracks.length; i++) {
+      if (gen != _queueGeneration) return;
+      try {
+        final src = await _buildAudioSource(tracks[i]);
+        if (gen != _queueGeneration) return;
+        await _player.addAudioSource(src);
+      } catch (e) {
+        debugPrint('audio_handler: forward fill failed for ${tracks[i].id}: $e');
+      }
+    }
+    if (initialIndex > 0) {
+      _suppressIndexUpdates = true;
+      try {
+        for (var i = 0; i < initialIndex; i++) {
+          if (gen != _queueGeneration) return;
+          final src = await _buildAudioSource(tracks[i]);
+          if (gen != _queueGeneration) return;
+          await _player.insertAudioSource(i, src);
+        }
+      } catch (e) {
+        debugPrint('audio_handler: backward fill failed: $e');
+      } finally {
+        // Only release the flag if we're still the active gen — a
+        // newer setQueueFromTracks already reset it for itself.
+        if (gen == _queueGeneration) _suppressIndexUpdates = false;
+      }
+    }
   }
 
   String _resolveStreamUrl(TrackRef t) {
@@ -103,7 +199,6 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
     if (mgr != null) {
       final path = await mgr.pathFor(t.id);
       if (path != null) {
-        debugPrint('audio_handler: cache hit for track.id=${t.id} → file://$path');
         return AudioSource.uri(Uri.file(path));
       }
     }
@@ -127,17 +222,14 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
     // pin / Download buttons cover the index path; LockCaching handles
     // the network optimization.
     if (mgr != null) {
-      final cacheDir = await getApplicationCacheDirectory();
+      _cacheDirPath ??= (await getApplicationCacheDirectory()).path;
-      final cacheFile = File('${cacheDir.path}/audio_cache/${t.id}.mp3');
+      final cacheFile = File('${_cacheDirPath!}/audio_cache/${t.id}.mp3');
-      debugPrint('audio_handler: cache miss for track.id=${t.id}, '
-          'using LockCachingAudioSource → ${cacheFile.path}');
       // ignore: experimental_member_use
       return LockCachingAudioSource(parsed,
           headers: headers, cacheFile: cacheFile);
     }
 
     // 3. No manager configured: plain network source (legacy path).
-    debugPrint('audio_handler: no cache manager; track.id=${t.id} → "$url"');
     return AudioSource.uri(parsed, headers: headers);
   }
 
@@ -184,8 +276,40 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
     );
   }
 
+  /// Once a track is fully buffered (LockCaching has written the whole
+  /// file to disk), insert an audio_cache_index row so the file shows
+  /// up to AudioCacheManager.evict() and clearAll(). No-op if the
+  /// cache manager isn't configured, no current track, the file isn't
+  /// fully buffered yet, the on-disk file is missing, or we already
+  /// registered this trackId during this subscription.
+  Future<void> _maybeRegisterStreamCache() async {
+    final mgr = _audioCacheManager;
+    if (mgr == null) return;
+    final current = mediaItem.value;
+    if (current == null) return;
+    final trackId = current.id;
+    if (_streamCacheRegistered.contains(trackId)) return;
+
+    final dur = _player.duration;
+    if (dur == null) return;
+    final buf = _player.bufferedPosition;
+    // 200ms slack for header bytes / encoding rounding.
+    if (buf < dur - const Duration(milliseconds: 200)) return;
+
+    _cacheDirPath ??= (await getApplicationCacheDirectory()).path;
+    final path = '${_cacheDirPath!}/audio_cache/$trackId.mp3';
+    final file = File(path);
+    if (!await file.exists()) return;
+    final size = await file.length();
+    if (size <= 0) return;
+
+    _streamCacheRegistered.add(trackId);
+    await mgr.registerStreamCache(trackId, path, size);
+  }
+
   void _onCurrentIndexChanged(int? idx) {
     if (idx == null) return;
+    if (_suppressIndexUpdates) return;
     // Push the new track's MediaItem onto the mediaItem stream so
     // the player UI rebuilds with the new title/artist/album/cover.
     // Without this, the bar and full player stayed pinned to whichever

flutter_client/lib/player/now_playing_screen.dart

@@ -113,20 +113,21 @@ class _NowPlayingScreenState extends ConsumerState<NowPlayingScreen> {
                           overflow: TextOverflow.ellipsis,
                         ),
                       ],
-                      const SizedBox(height: 32),
-                      _SeekRow(position: pos, duration: dur, fs: fs, ref: ref),
-                      const SizedBox(height: 24),
-                      _PrimaryControls(
-                        fs: fs,
-                        ref: ref,
-                        isPlaying: isPlaying,
-                      ),
                       const SizedBox(height: 24),
                       _SecondaryControls(
                         fs: fs,
                         actions: actions,
                         shuffleOn: shuffleOn,
                         repeatMode: repeatMode,
+                        media: media,
+                      ),
+                      const SizedBox(height: 8),
+                      _SeekRow(position: pos, duration: dur, fs: fs, ref: ref),
+                      const SizedBox(height: 24),
+                      _PrimaryControls(
+                        fs: fs,
+                        ref: ref,
+                        isPlaying: isPlaying,
                       ),
                       const SizedBox(height: 24),
                     ],
@@ -219,48 +220,14 @@ class _TitleRow extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    // Stack: title centered absolutely in the row; like + kebab pinned
+    // Title-only — like + kebab moved into _SecondaryControls above
-    // to the right edge. Padding on the title equals the actions' width
+    // the seek bar so they share the same row as shuffle/repeat/queue.
-    // so it stays optically centered without colliding with them.
+    return Text(
-    return SizedBox(
+      media.title,
-      height: 32,
+      style: TextStyle(color: fs.parchment, fontSize: 22),
-      child: Stack(
+      maxLines: 1,
-        alignment: Alignment.center,
+      overflow: TextOverflow.ellipsis,
-        children: [
+      textAlign: TextAlign.center,
-          Padding(
-            padding: const EdgeInsets.symmetric(horizontal: 64),
-            child: Text(
-              media.title,
-              style: TextStyle(color: fs.parchment, fontSize: 22),
-              maxLines: 1,
-              overflow: TextOverflow.ellipsis,
-              textAlign: TextAlign.center,
-            ),
-          ),
-          Positioned(
-            right: 0,
-            child: Row(
-              mainAxisSize: MainAxisSize.min,
-              children: [
-                LikeButton(kind: LikeKind.track, id: media.id, size: 22),
-                TrackActionsButton(
-                  track: TrackRef(
-                    id: media.id,
-                    title: media.title,
-                    albumId: (media.extras?['album_id'] as String?) ?? '',
-                    albumTitle: media.album ?? '',
-                    artistId: (media.extras?['artist_id'] as String?) ?? '',
-                    artistName: media.artist ?? '',
-                    durationSec: media.duration?.inSeconds ?? 0,
-                    streamUrl: '',
-                  ),
-                  hideQueueActions: true,
-                ),
-              ],
-            ),
-          ),
-        ],
-      ),
     );
   }
 }
@@ -365,17 +332,23 @@ class _PrimaryControls extends StatelessWidget {
   }
 }
 
+/// Action row sitting just above the seek bar. Holds shuffle / repeat
+/// / queue plus the like + kebab that used to live in the title row,
+/// so the title can sit truly centered above and this row carries
+/// every per-track action in one place.
 class _SecondaryControls extends StatelessWidget {
   const _SecondaryControls({
     required this.fs,
     required this.actions,
     required this.shuffleOn,
     required this.repeatMode,
+    required this.media,
   });
   final FabledSwordTheme fs;
   final PlayerActions actions;
   final bool shuffleOn;
   final AudioServiceRepeatMode repeatMode;
+  final MediaItem media;
 
   @override
   Widget build(BuildContext context) {
@@ -411,6 +384,31 @@ class _SecondaryControls extends StatelessWidget {
           icon: Icon(Icons.queue_music, color: fs.ash),
           onPressed: () => GoRouter.of(context).push('/queue'),
         ),
+        LikeButton(kind: LikeKind.track, id: media.id, size: 22),
+        TrackActionsButton(
+          track: TrackRef(
+            id: media.id,
+            title: media.title,
+            albumId: (media.extras?['album_id'] as String?) ?? '',
+            albumTitle: media.album ?? '',
+            artistId: (media.extras?['artist_id'] as String?) ?? '',
+            artistName: media.artist ?? '',
+            durationSec: media.duration?.inSeconds ?? 0,
+            streamUrl: '',
+          ),
+          hideQueueActions: true,
+          // /now-playing lives outside the ShellRoute. Pushing
+          // /artists/:id or /albums/:id (both shell-children) on top
+          // of it would make go_router try to mount a duplicate
+          // ShellRoute (the same _debugCheckDuplicatedPageKeys crash
+          // we hit before with /queue). Await our own pop fully
+          // before pushing the destination so go_router never sees
+          // both pages active in the same frame.
+          onNavigate: (path) async {
+            await Navigator.of(context).maybePop();
+            if (context.mounted) GoRouter.of(context).push(path);
+          },
+        ),
       ],
     );
   }

flutter_client/lib/playlists/playlist_detail_screen.dart

@@ -12,13 +12,26 @@ import '../theme/theme_extension.dart';
 import 'playlists_provider.dart';
 
 class PlaylistDetailScreen extends ConsumerWidget {
-  const PlaylistDetailScreen({required this.id, super.key});
+  const PlaylistDetailScreen({required this.id, this.seed, super.key});
   final String id;
 
+  /// Optional Playlist passed via go_router extra so the header
+  /// (title, cover, track count, play/download CTAs) can render
+  /// before the full detail fetch resolves. Same pattern as album
+  /// + artist nav hydration.
+  final Playlist? seed;
+
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final fs = Theme.of(context).extension<FabledSwordTheme>()!;
     final detail = ref.watch(playlistDetailProvider(id));
+
+    // Resolve the best playlist info available for the AppBar title.
+    final livePlaylist = detail.value?.playlist;
+    final headerName = (livePlaylist != null && livePlaylist.name.isNotEmpty)
+        ? livePlaylist.name
+        : (seed?.name ?? '');
+
     return Scaffold(
       backgroundColor: fs.obsidian,
       appBar: AppBar(
@@ -28,17 +41,21 @@ class PlaylistDetailScreen extends ConsumerWidget {
           icon: Icon(Icons.arrow_back, color: fs.parchment),
           onPressed: () => context.pop(),
         ),
-        title: detail.maybeWhen(
+        title: headerName.isEmpty
-          data: (d) => Text(
+            ? const SizedBox.shrink()
-            d.playlist.name,
+            : Text(
-            style: TextStyle(color: fs.parchment),
+                headerName,
-            overflow: TextOverflow.ellipsis,
+                style: TextStyle(color: fs.parchment),
-          ),
+                overflow: TextOverflow.ellipsis,
-          orElse: () => const SizedBox.shrink(),
+              ),
-        ),
       ),
       body: detail.when(
-        loading: () => const Center(child: CircularProgressIndicator()),
+        // Loading from a seed: render the header immediately + a
+        // small inline "loading tracks" hint, instead of an opaque
+        // full-screen spinner. The body fills in when tracks arrive.
+        loading: () => seed == null
+            ? const Center(child: CircularProgressIndicator())
+            : _SeedBody(playlist: seed!),
         error: (e, _) =>
             Center(child: Text('$e', style: TextStyle(color: fs.error))),
         data: (d) => _Body(detail: d),
@@ -47,6 +64,43 @@ class PlaylistDetailScreen extends ConsumerWidget {
   }
 }
 
+/// Loading-state body: renders just the header from the seed
+/// playlist + a "loading tracks…" placeholder. CTA buttons are
+/// hidden until the real track list arrives (they need playable
+/// refs to do anything useful).
+class _SeedBody extends StatelessWidget {
+  const _SeedBody({required this.playlist});
+  final Playlist playlist;
+
+  @override
+  Widget build(BuildContext context) {
+    final fs = Theme.of(context).extension<FabledSwordTheme>()!;
+    return ListView(children: [
+      Padding(
+        padding: const EdgeInsets.fromLTRB(16, 8, 16, 16),
+        child: Column(crossAxisAlignment: CrossAxisAlignment.start, children: [
+          if (playlist.description.isNotEmpty)
+            Padding(
+              padding: const EdgeInsets.only(bottom: 12),
+              child: Text(
+                playlist.description,
+                style: TextStyle(color: fs.ash, fontSize: 13),
+              ),
+            ),
+          Text(
+            '${playlist.trackCount} ${playlist.trackCount == 1 ? "track" : "tracks"}',
+            style: TextStyle(color: fs.ash, fontSize: 12),
+          ),
+        ]),
+      ),
+      const Padding(
+        padding: EdgeInsets.symmetric(vertical: 24),
+        child: Center(child: CircularProgressIndicator()),
+      ),
+    ]);
+  }
+}
+
 class _Body extends ConsumerWidget {
   const _Body({required this.detail});
   final PlaylistDetail detail;

flutter_client/lib/playlists/playlists_list_screen.dart

@@ -51,7 +51,7 @@ class PlaylistsListScreen extends ConsumerWidget {
                 final p = items[i];
                 return _PlaylistTile(
                   playlist: p,
-                  onTap: () => ctx.push('/playlists/${p.id}'),
+                  onTap: () => ctx.push('/playlists/${p.id}', extra: p),
                 );
               },
             ),
@@ -83,7 +83,11 @@ class _PlaylistTile extends StatelessWidget {
               color: fs.slate,
               child: playlist.coverUrl.isEmpty
                   ? Icon(Icons.queue_music, color: fs.ash)
-                  : ServerImage(url: playlist.coverUrl, fit: BoxFit.cover),
+                  : ServerImage(
+                      url: playlist.coverUrl,
+                      fit: BoxFit.cover,
+                      fallback: Icon(Icons.queue_music, color: fs.ash),
+                    ),
             ),
           ),
           const SizedBox(width: 12),

flutter_client/lib/playlists/playlists_provider.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:dio/dio.dart';
 import 'package:drift/drift.dart' as drift;
 import 'package:flutter/foundation.dart' show debugPrint;
 import 'package:flutter_riverpod/flutter_riverpod.dart';
@@ -39,12 +40,21 @@ final playlistsListProvider =
     fetchAndPopulate: () async {
       final api = await ref.read(playlistsApiProvider.future);
       final fresh = await api.list(kind: kind);
-      final ownedSysCount =
+
-          fresh.owned.where((p) => p.systemVariant != null).length;
+      // Reconcile: BuildSystemPlaylists rotates system-playlist UUIDs
-      debugPrint(
+      // every rebuild, so insertOrReplace alone leaves stale rows in
-          'playlistsListProvider($kind): wire returned owned=${fresh.owned.length} '
+      // drift. Tapping one of those stale tiles 404s. Delete every
-          '(system=$ownedSysCount) public=${fresh.public.length}');
+      // owned drift row whose id isn't in the fresh response, then
+      // upsert the fresh set.
+      final freshOwnedIds =
+          fresh.owned.map((p) => p.id).toSet();
       await db.batch((b) {
+        if (user != null) {
+          b.deleteWhere(db.cachedPlaylists, (t) {
+            return t.userId.equals(user.id) &
+                t.id.isNotIn(freshOwnedIds);
+          });
+        }
         for (final p in fresh.all) {
           b.insert(db.cachedPlaylists, p.toDrift(),
               mode: drift.InsertMode.insertOrReplace);
@@ -66,13 +76,6 @@ final playlistsListProvider =
           .where((r) => r.userId != user.id && r.isPublic)
           .map((r) => r.toRef())
           .toList();
-      final ownedSys = owned.where((p) => p.isSystem).length;
-      final driftSys = filtered.where((r) => r.systemVariant != null).length;
-      debugPrint(
-          'playlistsListProvider($kind): drift rows=${rows.length} '
-          'filtered=${filtered.length} (system=$driftSys) '
-          'owned=${owned.length} (system=$ownedSys) pub=${pub.length} '
-          'userId=${user.id}');
       return PlaylistsList(owned: owned, public: pub);
     },
     isOnline: () async => (await ref
@@ -138,18 +141,31 @@ final playlistDetailProvider =
   Future<bool> fetchAndPopulate() async {
     try {
       final api = await ref.read(playlistsApiProvider.future);
-      debugPrint('playlistDetailProvider($id): calling get');
       final fresh = await api.get(id).timeout(const Duration(seconds: 10));
-      debugPrint(
-          'playlistDetailProvider($id): got ${fresh.tracks.length} tracks, writing');
 
-      // Collect the artist + album rows referenced by these tracks so
+      // Collect the track + artist + album rows referenced by these
-      // the JOINs that build artistName/albumTitle in the row view
+      // playlist entries. Without writing the cachedTracks rows
-      // have something to bind to. Without this, system-playlist tracks
+      // themselves, the detail-screen JOIN against cachedTracks
-      // surface with empty artist/album columns.
+      // returns null on every row (only the playlist_tracks join
+      // succeeds), so the UI shows a list with empty titles and
+      // unplayable tracks.
+      final tracks = <String, _TrackRefRow>{};
       final artists = <String, ArtistRefRow>{};
       final albums = <String, AlbumRefRow>{};
       for (final t in fresh.tracks) {
+        final tId = t.trackId;
+        if (tId != null && tId.isNotEmpty) {
+          tracks.putIfAbsent(
+            tId,
+            () => _TrackRefRow(
+              id: tId,
+              title: t.title,
+              albumId: t.albumId ?? '',
+              artistId: t.artistId ?? '',
+              durationSec: t.durationSec,
+            ),
+          );
+        }
         final aId = t.artistId;
         final aName = t.artistName;
         if (aId != null && aId.isNotEmpty && aName.isNotEmpty) {
@@ -198,6 +214,25 @@ final playlistDetailProvider =
                 .toList(),
           );
         }
+        if (tracks.isNotEmpty) {
+          // Insert/update cachedTracks so the detail screen's JOIN
+          // produces real titles + durations. We don't have
+          // track_number / disc_number on the wire (PlaylistTrack
+          // omits them), so they default to 0 — UI doesn't surface
+          // them on this screen so it's fine.
+          b.insertAllOnConflictUpdate(
+            db.cachedTracks,
+            tracks.values
+                .map((t) => CachedTracksCompanion.insert(
+                      id: t.id,
+                      albumId: t.albumId,
+                      artistId: t.artistId,
+                      title: t.title,
+                      durationMs: drift.Value(t.durationSec * 1000),
+                    ))
+                .toList(),
+          );
+        }
         if (albums.isNotEmpty) {
           b.insertAllOnConflictUpdate(
             db.cachedAlbums,
@@ -212,10 +247,21 @@ final playlistDetailProvider =
           );
         }
       });
-      debugPrint(
-          'playlistDetailProvider($id): drift write done; awaiting watch re-emit');
       return true;
     } catch (e, st) {
+      // 404 = the playlist row in drift is stale (BuildSystemPlaylists
+      // rotates UUIDs on each rebuild, so old For-You / Songs-Like
+      // tiles can outlive the actual server-side playlist). Wipe the
+      // stale row + its track positions so the home tile disappears
+      // on next render and we don't keep trying.
+      if (e is DioException && e.response?.statusCode == 404) {
+        await db.batch((b) {
+          b.deleteWhere(
+              db.cachedPlaylistTracks, (t) => t.playlistId.equals(id));
+          b.deleteWhere(db.cachedPlaylists, (t) => t.id.equals(id));
+        });
+        return false;
+      }
       debugPrint('playlistDetailProvider($id): fetch failed: $e\n$st');
       return false;
     }
@@ -224,11 +270,9 @@ final playlistDetailProvider =
   // Once-per-subscription guard so an empty server response doesn't
   // cause repeated re-fetches.
   var fetchAttempted = false;
-  var revalidated = false;
 
   await for (final playlistRows in playlistQuery.watch()) {
     if (playlistRows.isEmpty) {
-      debugPrint('playlistDetailProvider($id): drift miss, cold-fetching');
       if (fetchAttempted) {
         yield emptyDetail();
         continue;
@@ -243,9 +287,6 @@ final playlistDetailProvider =
       continue;
     }
 
-    debugPrint(
-        'playlistDetailProvider($id): drift hit (${playlistRows.length} rows)');
-
     final playlist = playlistRows.first.toRef();
     final trackRows = await tracksQuery.get();
 
@@ -254,8 +295,6 @@ final playlistDetailProvider =
     // tracks for system playlists). Trigger the same fetch, drift
     // watch re-emits with populated tracks.
     if (trackRows.isEmpty && !fetchAttempted) {
-      debugPrint(
-          'playlistDetailProvider($id): playlist hit but no tracks; fetching');
       fetchAttempted = true;
       if (await isOnline()) {
         final ok = await fetchAndPopulate();
@@ -283,13 +322,12 @@ final playlistDetailProvider =
 
     yield PlaylistDetail(playlist: playlist, tracks: tracks);
 
-    // SWR: first complete cache hit kicks one background refresh.
+    // No SWR refresh here. The aggregate playlistsListProvider does
-    if (!revalidated && trackRows.isNotEmpty) {
+    // alwaysRefresh (system playlists rotate UUIDs), but per-detail
-      revalidated = true;
+    // refresh on every visit was multiplying with the prefetcher's
-      if (await isOnline()) {
+    // parallel fetches and starving user-initiated playback. Pull-
-        unawaited(fetchAndPopulate());
+    // to-refresh on the detail page invalidates the provider, which
-      }
+    // is the right path for an explicit refresh.
-    }
   }
 });
 
@@ -309,6 +347,21 @@ class AlbumRefRow {
   final String artistId;
 }
 
+class _TrackRefRow {
+  _TrackRefRow({
+    required this.id,
+    required this.title,
+    required this.albumId,
+    required this.artistId,
+    required this.durationSec,
+  });
+  final String id;
+  final String title;
+  final String albumId;
+  final String artistId;
+  final int durationSec;
+}
+
 final systemPlaylistsStatusProvider =
     FutureProvider<SystemPlaylistsStatus>((ref) async {
   final dio = await ref.watch(dioProvider.future);

flutter_client/lib/playlists/widgets/playlist_card.dart

@@ -21,7 +21,8 @@ class PlaylistCard extends StatelessWidget {
       child: Material(
         color: Colors.transparent,
         child: InkWell(
-          onTap: () => context.push('/playlists/${playlist.id}'),
+          onTap: () =>
+              context.push('/playlists/${playlist.id}', extra: playlist),
           child: Padding(
             padding: const EdgeInsets.symmetric(horizontal: 8),
             child: Column(crossAxisAlignment: CrossAxisAlignment.start, children: [
@@ -31,9 +32,19 @@ class PlaylistCard extends StatelessWidget {
                   width: 144,
                   height: 144,
                   color: fs.slate,
+                  // coverUrl is deterministic per playlist (see
+                  // CachedPlaylistAdapter.toRef). When the server's
+                  // collage isn't built yet, ServerImage's
+                  // errorBuilder shows the queue_music icon over the
+                  // slate background.
                   child: playlist.coverUrl.isEmpty
                       ? Icon(Icons.queue_music, color: fs.ash, size: 56)
-                      : ServerImage(url: playlist.coverUrl, fit: BoxFit.cover),
+                      : ServerImage(
+                          url: playlist.coverUrl,
+                          fit: BoxFit.cover,
+                          fallback:
+                              Icon(Icons.queue_music, color: fs.ash, size: 56),
+                        ),
                 ),
               ),
               const SizedBox(height: 8),

flutter_client/lib/shared/routing.dart

@@ -9,6 +9,7 @@ import '../library/album_detail_screen.dart';
 import '../library/artist_detail_screen.dart';
 import '../models/album.dart';
 import '../models/artist.dart';
+import '../models/playlist.dart';
 import '../discover/discover_screen.dart';
 import '../library/home_screen.dart';
 import '../library/library_screen.dart';
@@ -85,6 +86,14 @@ GoRouter buildRouter(Ref ref) {
           },
         ),
       ),
+      // /queue lives outside the ShellRoute too. Why: pushing /queue
+      // from /now-playing (which is also outside the shell) used to
+      // cause go_router to mount a second ShellRoute instance under
+      // the existing one, producing a duplicate page-key assertion
+      // (NavigatorState._debugCheckDuplicatedPageKeys). Top-level
+      // routes can stack on each other freely; shell-children can't
+      // when something on top of the shell is already routing.
+      GoRoute(path: '/queue', builder: (_, __) => const QueueScreen()),
       ShellRoute(
         builder: (ctx, state, child) => VersionGate(child: _ShellWithPlayerBar(child: child)),
         routes: [
@@ -105,7 +114,6 @@ GoRouter buildRouter(Ref ref) {
               seed: s.extra is AlbumRef ? s.extra as AlbumRef : null,
             ),
           ),
-          GoRoute(path: '/queue', builder: (_, __) => const QueueScreen()),
           GoRoute(path: '/search', builder: (_, __) => const SearchScreen()),
           GoRoute(path: '/library', builder: (_, __) => const LibraryScreen()),
           GoRoute(path: '/discover', builder: (_, __) => const DiscoverScreen()),
@@ -113,7 +121,10 @@ GoRouter buildRouter(Ref ref) {
           GoRoute(path: '/playlists', builder: (_, __) => const PlaylistsListScreen()),
           GoRoute(
             path: '/playlists/:id',
-            builder: (_, s) => PlaylistDetailScreen(id: s.pathParameters['id']!),
+            builder: (_, s) => PlaylistDetailScreen(
+              id: s.pathParameters['id']!,
+              seed: s.extra is Playlist ? s.extra as Playlist : null,
+            ),
           ),
           GoRoute(path: '/requests',         builder: (_, __) => const RequestsScreen()),
           GoRoute(path: '/admin',            builder: (_, __) => const AdminLandingScreen()),

flutter_client/lib/shared/widgets/track_actions/track_actions_button.dart

@@ -11,6 +11,7 @@ class TrackActionsButton extends StatelessWidget {
     super.key,
     required this.track,
     this.hideQueueActions = false,
+    this.onNavigate,
   });
 
   final TrackRef track;
@@ -19,6 +20,11 @@ class TrackActionsButton extends StatelessWidget {
   /// screen where the menu's track IS the currently-playing one.
   final bool hideQueueActions;
 
+  /// Forwarded to TrackActionsSheet.onNavigate. The host receives the
+  /// destination path AFTER the sheet has popped and is responsible
+  /// for navigating to it (typically: pop self first, then push).
+  final Future<void> Function(String path)? onNavigate;
+
   @override
   Widget build(BuildContext context) {
     final fs = Theme.of(context).extension<FabledSwordTheme>()!;
@@ -29,6 +35,7 @@ class TrackActionsButton extends StatelessWidget {
         context,
         track,
         hideQueueActions: hideQueueActions,
+        onNavigate: onNavigate,
       ),
     );
   }

flutter_client/lib/shared/widgets/track_actions/track_actions_sheet.dart

@@ -21,15 +21,27 @@ class TrackActionsSheet extends ConsumerWidget {
     super.key,
     required this.track,
     required this.hideQueueActions,
+    this.onNavigate,
   });
 
   final TrackRef track;
   final bool hideQueueActions;
 
+  /// Optional hook for "Go to album" / "Go to artist". Called with
+  /// the destination route path AFTER the sheet has popped. Lets
+  /// callers that live OUTSIDE the ShellRoute (e.g. the full player
+  /// at /now-playing) pop themselves first then push, so go_router
+  /// doesn't try to mount a second ShellRoute on top of the active
+  /// top-level route. When null, the sheet does its own
+  /// context.push, which is correct for surfaces already inside the
+  /// shell (mini player, track rows on detail screens, etc.).
+  final Future<void> Function(String path)? onNavigate;
+
   static Future<void> show(
     BuildContext context,
     TrackRef track, {
     bool hideQueueActions = false,
+    Future<void> Function(String path)? onNavigate,
   }) {
     return showModalBottomSheet<void>(
       context: context,
@@ -37,6 +49,7 @@ class TrackActionsSheet extends ConsumerWidget {
       builder: (_) => TrackActionsSheet(
         track: track,
         hideQueueActions: hideQueueActions,
+        onNavigate: onNavigate,
       ),
     );
   }
@@ -141,7 +154,12 @@ class TrackActionsSheet extends ConsumerWidget {
               label: 'Go to album',
               onTap: () {
                 Navigator.pop(context);
-                context.push('/albums/${track.albumId}');
+                final path = '/albums/${track.albumId}';
+                if (onNavigate != null) {
+                  onNavigate!(path);
+                } else {
+                  context.push(path);
+                }
               },
             ),
             _MenuItem(
@@ -150,7 +168,12 @@ class TrackActionsSheet extends ConsumerWidget {
               label: 'Go to artist',
               onTap: () {
                 Navigator.pop(context);
-                context.push('/artists/${track.artistId}');
+                final path = '/artists/${track.artistId}';
+                if (onNavigate != null) {
+                  onNavigate!(path);
+                } else {
+                  context.push(path);
+                }
               },
             ),
             const _Divider(),

internal/api/library.go

@@ -40,19 +40,28 @@ func (h *handlers) handleGetTrack(w http.ResponseWriter, r *http.Request) {
 // handleGetAlbum implements GET /api/albums/{id}. Returns the album plus its
 // tracks (ordered by disc/track number via the underlying query) with
 // duration summed from the track list — keeps one source of truth.
+//
+// Two DB round trips: the album+artist join and the per-user tracks
+// list. Down from three (separate album, artist, tracks) before
+// GetAlbumWithArtist landed.
 func (h *handlers) handleGetAlbum(w http.ResponseWriter, r *http.Request) {
 	q := dbq.New(h.pool)
-	album, apiErr := resolveByID(r, "id", q.GetAlbumByID, "album")
+	id, ok := requireURLUUID(w, r, "id")
-	if apiErr != nil {
+	if !ok {
-		writeErr(w, apiErr)
 		return
 	}
-	artist, err := q.GetArtistByID(r.Context(), album.ArtistID)
+	row, err := q.GetAlbumWithArtist(r.Context(), id)
 	if err != nil {
-		h.logger.Error("api: get album artist failed", "err", err)
+		if errors.Is(err, pgx.ErrNoRows) {
+			writeErr(w, apierror.NotFound("album"))
+			return
+		}
+		h.logger.Error("api: get album+artist failed", "err", err)
 		writeErr(w, apierror.InternalMsg("lookup failed", err))
 		return
 	}
+	album := row.Album
+	artistName := row.ArtistName
 	var userID pgtype.UUID
 	if user, ok := auth.UserFromContext(r.Context()); ok {
 		userID = user.ID
@@ -68,20 +77,24 @@ func (h *handlers) handleGetAlbum(w http.ResponseWriter, r *http.Request) {
 	refs := make([]TrackRef, 0, len(tracks))
 	durSec := 0
 	for _, t := range tracks {
-		ref := trackRefFrom(t, album.Title, artist.Name)
+		ref := trackRefFrom(t, album.Title, artistName)
 		refs = append(refs, ref)
 		durSec += ref.DurationSec
 	}
 	detail := AlbumDetail{
-		AlbumRef: albumRefFrom(album, artist.Name, len(tracks), durSec),
+		AlbumRef: albumRefFrom(album, artistName, len(tracks), durSec),
 		Tracks:   refs,
 	}
 	writeJSON(w, http.StatusOK, detail)
 }
 
 // handleGetArtist implements GET /api/artists/{id}. Returns artist + albums;
-// each album carries its own track_count (one count query per album, same
+// each album carries its own track_count.
-// pattern as subsonic). At M1 sizes (albums-per-artist << 100) this is fine.
+//
+// Down from 1 + 1 + N queries (artist, albums, per-album CountTracksByAlbum)
+// to 1 + 1 (artist, albums-with-track-count via correlated subquery).
+// On a 30-album artist that's ~32 round trips collapsed to 2 — the
+// difference between "feels slow" and "feels instant" on detail nav.
 func (h *handlers) handleGetArtist(w http.ResponseWriter, r *http.Request) {
 	q := dbq.New(h.pool)
 	artist, apiErr := resolveByID(r, "id", q.GetArtistByID, "artist")
@@ -89,25 +102,19 @@ func (h *handlers) handleGetArtist(w http.ResponseWriter, r *http.Request) {
 		writeErr(w, apiErr)
 		return
 	}
-	albums, err := q.ListAlbumsByArtist(r.Context(), artist.ID)
+	rows, err := q.ListAlbumsByArtistWithTrackCount(r.Context(), artist.ID)
 	if err != nil {
 		h.logger.Error("api: list albums by artist failed", "err", err)
 		writeErr(w, apierror.InternalMsg("lookup failed", err))
 		return
 	}
-	refs := make([]AlbumRef, 0, len(albums))
+	refs := make([]AlbumRef, 0, len(rows))
-	for _, a := range albums {
+	for _, row := range rows {
-		count, cerr := q.CountTracksByAlbum(r.Context(), a.ID)
-		if cerr != nil {
-			h.logger.Error("api: count tracks failed", "err", cerr)
-			writeErr(w, apierror.InternalMsg("lookup failed", cerr))
-			return
-		}
 		// durationSec=0: not aggregated for nested album lists per spec data flow.
-		refs = append(refs, albumRefFrom(a, artist.Name, int(count), 0))
+		refs = append(refs, albumRefFrom(row.Album, artist.Name, int(row.TrackCount), 0))
 	}
 	detail := ArtistDetail{
-		ArtistRef: artistRefFrom(artist, len(albums)),
+		ArtistRef: artistRefFrom(artist, len(rows)),
 		Albums:    refs,
 	}
 	writeJSON(w, http.StatusOK, detail)

internal/api/media.go

@@ -112,6 +112,12 @@ func (h *handlers) handleGetCover(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	w.Header().Set("Content-Type", imageContentType(path))
+	// Cover bytes change rarely (cover-source enrichment, manual rescan,
+	// rare MBID-driven re-fetch). One-day max-age + must-revalidate means
+	// clients skip the conditional GET for the bulk of a session, but
+	// stale art clears within 24h after a re-scan. ServeContent below
+	// still emits Last-Modified for the conditional path when needed.
+	w.Header().Set("Cache-Control", "public, max-age=86400, must-revalidate")
 	http.ServeContent(w, r, filepath.Base(path), info.ModTime(), f)
 }
 
@@ -140,5 +146,11 @@ func (h *handlers) handleGetStream(w http.ResponseWriter, r *http.Request) {
 	}
 	w.Header().Set("Content-Type", audioContentType(track.FileFormat))
 	w.Header().Set("Accept-Ranges", "bytes")
+	// Track bytes are immutable for a given track id (the scanner
+	// indexes by file_path; re-encoded files take new ids). One-year
+	// max-age + immutable lets the client cache (LockCachingAudioSource
+	// on the Flutter side, browser cache on web) skip even the
+	// conditional GET on repeat plays.
+	w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
 	http.ServeContent(w, r, filepath.Base(track.FilePath), info.ModTime(), f)
 }

internal/api/playlists.go

@@ -386,6 +386,11 @@ func (h *handlers) handleGetPlaylistCover(w http.ResponseWriter, r *http.Request
 		return
 	}
 	full := filepath.Join(h.dataDir, *detail.CoverPath)
+	// Playlist collages recompute when the playlist's tracks change
+	// (system playlists re-rendered on rebuild, user playlists when
+	// modified). 5 minutes is short enough for normal edits to feel
+	// fresh, long enough to skip repeat fetches during a session.
+	w.Header().Set("Cache-Control", "public, max-age=300, must-revalidate")
 	http.ServeFile(w, r, full)
 }
 

internal/db/dbq/albums.sql.go

@@ -168,6 +168,41 @@ func (q *Queries) GetAlbumCoverageRollup(ctx context.Context) (GetAlbumCoverageR
 	return i, err
 }
 
+const getAlbumWithArtist = `-- name: GetAlbumWithArtist :one
+SELECT albums.id, albums.title, albums.sort_title, albums.artist_id, albums.release_date, albums.mbid, albums.cover_art_path, albums.created_at, albums.updated_at, albums.cover_art_source, albums.cover_art_sources_version, artists.name AS artist_name
+FROM albums
+JOIN artists ON artists.id = albums.artist_id
+WHERE albums.id = $1
+`
+
+type GetAlbumWithArtistRow struct {
+	Album      Album
+	ArtistName string
+}
+
+// Combined fetch for /api/albums/{id}: returns the album row + the
+// joined artist name in a single round trip. Replaces a sequential
+// GetAlbumByID + GetArtistByID pair on the hot detail-page path.
+func (q *Queries) GetAlbumWithArtist(ctx context.Context, id pgtype.UUID) (GetAlbumWithArtistRow, error) {
+	row := q.db.QueryRow(ctx, getAlbumWithArtist, id)
+	var i GetAlbumWithArtistRow
+	err := row.Scan(
+		&i.Album.ID,
+		&i.Album.Title,
+		&i.Album.SortTitle,
+		&i.Album.ArtistID,
+		&i.Album.ReleaseDate,
+		&i.Album.Mbid,
+		&i.Album.CoverArtPath,
+		&i.Album.CreatedAt,
+		&i.Album.UpdatedAt,
+		&i.Album.CoverArtSource,
+		&i.Album.CoverArtSourcesVersion,
+		&i.ArtistName,
+	)
+	return i, err
+}
+
 const getAlbumsByIDs = `-- name: GetAlbumsByIDs :many
 SELECT id, title, sort_title, artist_id, release_date, mbid, cover_art_path, created_at, updated_at, cover_art_source, cover_art_sources_version FROM albums WHERE id = ANY($1::uuid[])
 `
@@ -389,6 +424,56 @@ func (q *Queries) ListAlbumsByArtist(ctx context.Context, artistID pgtype.UUID)
 	return items, nil
 }
 
+const listAlbumsByArtistWithTrackCount = `-- name: ListAlbumsByArtistWithTrackCount :many
+SELECT albums.id, albums.title, albums.sort_title, albums.artist_id, albums.release_date, albums.mbid, albums.cover_art_path, albums.created_at, albums.updated_at, albums.cover_art_source, albums.cover_art_sources_version,
+       (SELECT count(*) FROM tracks t WHERE t.album_id = albums.id)::bigint
+           AS track_count
+FROM albums
+WHERE albums.artist_id = $1
+ORDER BY release_date NULLS LAST, sort_title
+`
+
+type ListAlbumsByArtistWithTrackCountRow struct {
+	Album      Album
+	TrackCount int64
+}
+
+// Replaces the N+1 pattern in handleGetArtist (1 + N CountTracksByAlbum
+// per album). Returns each album joined with its track count via a
+// correlated subquery — single round trip regardless of album count.
+func (q *Queries) ListAlbumsByArtistWithTrackCount(ctx context.Context, artistID pgtype.UUID) ([]ListAlbumsByArtistWithTrackCountRow, error) {
+	rows, err := q.db.Query(ctx, listAlbumsByArtistWithTrackCount, artistID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []ListAlbumsByArtistWithTrackCountRow
+	for rows.Next() {
+		var i ListAlbumsByArtistWithTrackCountRow
+		if err := rows.Scan(
+			&i.Album.ID,
+			&i.Album.Title,
+			&i.Album.SortTitle,
+			&i.Album.ArtistID,
+			&i.Album.ReleaseDate,
+			&i.Album.Mbid,
+			&i.Album.CoverArtPath,
+			&i.Album.CreatedAt,
+			&i.Album.UpdatedAt,
+			&i.Album.CoverArtSource,
+			&i.Album.CoverArtSourcesVersion,
+			&i.TrackCount,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
 const listAlbumsByGenre = `-- name: ListAlbumsByGenre :many
 SELECT DISTINCT ON (albums.id) albums.id, albums.title, albums.sort_title, albums.artist_id, albums.release_date, albums.mbid, albums.cover_art_path, albums.created_at, albums.updated_at, albums.cover_art_source, albums.cover_art_sources_version
 FROM albums

internal/db/dbq/recommendation.sql.go

@@ -12,17 +12,19 @@ import (
 )
 
 const listLastPlayedArtistsForUser = `-- name: ListLastPlayedArtistsForUser :many
-SELECT a.id, a.name, a.sort_name, a.mbid, a.created_at, a.updated_at, a.artist_thumb_path, a.artist_fanart_path, a.artist_art_source, a.artist_art_sources_version,
+WITH user_plays AS (
-       cov.id        AS cover_album_id,
+    SELECT t.artist_id, max(pe.started_at) AS last_started
-       cnt.album_count::bigint AS album_count,
-       max_started.started_at::timestamptz AS last_played_at
-FROM artists a
-JOIN LATERAL (
-    SELECT max(pe.started_at) AS started_at
     FROM play_events pe
     JOIN tracks t ON t.id = pe.track_id
-    WHERE pe.user_id = $1 AND t.artist_id = a.id
+    WHERE pe.user_id = $1
-) max_started ON max_started.started_at IS NOT NULL
+    GROUP BY t.artist_id
+)
+SELECT a.id, a.name, a.sort_name, a.mbid, a.created_at, a.updated_at, a.artist_thumb_path, a.artist_fanart_path, a.artist_art_source, a.artist_art_sources_version,
+       cov.id AS cover_album_id,
+       cnt.album_count::bigint AS album_count,
+       up.last_started::timestamptz AS last_played_at
+FROM user_plays up
+JOIN artists a ON a.id = up.artist_id
 LEFT JOIN LATERAL (
     SELECT id FROM albums
     WHERE artist_id = a.id AND cover_art_path IS NOT NULL
@@ -32,7 +34,7 @@ LEFT JOIN LATERAL (
     SELECT count(*) AS album_count
     FROM albums WHERE artist_id = a.id
 ) cnt ON true
-ORDER BY max_started.started_at DESC, a.id
+ORDER BY up.last_started DESC, a.id
 LIMIT $2
 `
 
@@ -52,6 +54,15 @@ type ListLastPlayedArtistsForUserRow struct {
 // a derived cover_album_id via a representative-album lateral join (most
 // recent album that has cover_art_path set). album_count joined for the
 // ArtistRef wire shape.
+//
+// Earlier shape iterated `FROM artists a` and ran a LATERAL play_events
+// subquery per artist — O(total_artists) plan even for users with a
+// handful of plays. New shape aggregates the user's plays by artist
+// via the play_events → tracks join up front (uses
+// play_events_user_track_idx + tracks pkey lookups), then attaches
+// the artist row and lateral cover/count subqueries only for the
+// artists that actually appear. Distinct-artists set is small for a
+// typical user, so cost is bounded by play history not library size.
 func (q *Queries) ListLastPlayedArtistsForUser(ctx context.Context, arg ListLastPlayedArtistsForUserParams) ([]ListLastPlayedArtistsForUserRow, error) {
 	rows, err := q.db.Query(ctx, listLastPlayedArtistsForUser, arg.UserID, arg.Limit)
 	if err != nil {
@@ -87,24 +98,24 @@ func (q *Queries) ListLastPlayedArtistsForUser(ctx context.Context, arg ListLast
 }
 
 const listMostPlayedTracksForUser = `-- name: ListMostPlayedTracksForUser :many
+WITH plays AS (
+    SELECT track_id, count(*) AS cnt
+    FROM play_events
+    WHERE user_id = $1 AND was_skipped = false
+    GROUP BY track_id
+)
 SELECT t.id, t.title, t.album_id, t.artist_id, t.track_number, t.disc_number, t.duration_ms, t.file_path, t.file_size, t.file_format, t.bitrate, t.mbid, t.genre, t.added_at, t.updated_at,
        albums.title AS album_title,
        artists.name AS artist_name
-FROM tracks t
+FROM plays p
-JOIN albums  ON albums.id  = t.album_id
+JOIN tracks t   ON t.id = p.track_id
-JOIN artists ON artists.id = t.artist_id
+JOIN albums     ON albums.id  = t.album_id
-JOIN play_events pe ON pe.track_id = t.id
+JOIN artists    ON artists.id = t.artist_id
-WHERE pe.user_id = $1
+WHERE NOT EXISTS (
-  AND pe.was_skipped = false
+    SELECT 1 FROM lidarr_quarantine q
-  AND NOT EXISTS (
+    WHERE q.user_id = $1 AND q.track_id = t.id
-      SELECT 1 FROM lidarr_quarantine q
+)
-      WHERE q.user_id = $1 AND q.track_id = t.id
+ORDER BY p.cnt DESC, t.id
-  )
-GROUP BY t.id, t.title, t.album_id, t.artist_id, t.duration_ms, t.file_path,
-         t.file_format, t.file_size, t.bitrate, t.track_number, t.disc_number,
-         t.mbid, t.genre, t.added_at, t.updated_at,
-         albums.title, artists.name
-ORDER BY count(*) DESC, t.id
 LIMIT $2
 `
 
@@ -122,6 +133,11 @@ type ListMostPlayedTracksForUserRow struct {
 // M6a: top-N tracks by completed-play count for the user. was_skipped
 // excludes skips so a user spamming next doesn't fabricate a top track.
 // Quarantined tracks (per-user soft-hide from M5b) are filtered out.
+//
+// Aggregate play_events first (uses play_events_user_track_idx) and
+// join through tracks/albums/artists only for the survivors. Earlier
+// shape did the join across every play_event row before grouping —
+// O(plays) instead of O(distinct tracks).
 func (q *Queries) ListMostPlayedTracksForUser(ctx context.Context, arg ListMostPlayedTracksForUserParams) ([]ListMostPlayedTracksForUserRow, error) {
 	rows, err := q.db.Query(ctx, listMostPlayedTracksForUser, arg.UserID, arg.Limit)
 	if err != nil {

internal/db/queries/albums.sql

@@ -14,6 +14,26 @@ RETURNING *;
 -- name: GetAlbumByID :one
 SELECT * FROM albums WHERE id = $1;
 
+-- name: GetAlbumWithArtist :one
+-- Combined fetch for /api/albums/{id}: returns the album row + the
+-- joined artist name in a single round trip. Replaces a sequential
+-- GetAlbumByID + GetArtistByID pair on the hot detail-page path.
+SELECT sqlc.embed(albums), artists.name AS artist_name
+FROM albums
+JOIN artists ON artists.id = albums.artist_id
+WHERE albums.id = $1;
+
+-- name: ListAlbumsByArtistWithTrackCount :many
+-- Replaces the N+1 pattern in handleGetArtist (1 + N CountTracksByAlbum
+-- per album). Returns each album joined with its track count via a
+-- correlated subquery — single round trip regardless of album count.
+SELECT sqlc.embed(albums),
+       (SELECT count(*) FROM tracks t WHERE t.album_id = albums.id)::bigint
+           AS track_count
+FROM albums
+WHERE albums.artist_id = $1
+ORDER BY release_date NULLS LAST, sort_title;
+
 -- name: GetAlbumByArtistAndTitle :one
 -- Scanner uses this for the no-mbid dedupe path: resolve-or-create.
 SELECT * FROM albums WHERE artist_id = $1 AND title = $2 LIMIT 1;

internal/db/queries/recommendation.sql

@@ -206,24 +206,29 @@ LIMIT $3;
 -- M6a: top-N tracks by completed-play count for the user. was_skipped
 -- excludes skips so a user spamming next doesn't fabricate a top track.
 -- Quarantined tracks (per-user soft-hide from M5b) are filtered out.
+--
+-- Aggregate play_events first (uses play_events_user_track_idx) and
+-- join through tracks/albums/artists only for the survivors. Earlier
+-- shape did the join across every play_event row before grouping —
+-- O(plays) instead of O(distinct tracks).
+WITH plays AS (
+    SELECT track_id, count(*) AS cnt
+    FROM play_events
+    WHERE user_id = $1 AND was_skipped = false
+    GROUP BY track_id
+)
 SELECT sqlc.embed(t),
        albums.title AS album_title,
        artists.name AS artist_name
-FROM tracks t
+FROM plays p
-JOIN albums  ON albums.id  = t.album_id
+JOIN tracks t   ON t.id = p.track_id
-JOIN artists ON artists.id = t.artist_id
+JOIN albums     ON albums.id  = t.album_id
-JOIN play_events pe ON pe.track_id = t.id
+JOIN artists    ON artists.id = t.artist_id
-WHERE pe.user_id = $1
+WHERE NOT EXISTS (
-  AND pe.was_skipped = false
+    SELECT 1 FROM lidarr_quarantine q
-  AND NOT EXISTS (
+    WHERE q.user_id = $1 AND q.track_id = t.id
-      SELECT 1 FROM lidarr_quarantine q
+)
-      WHERE q.user_id = $1 AND q.track_id = t.id
+ORDER BY p.cnt DESC, t.id
-  )
-GROUP BY t.id, t.title, t.album_id, t.artist_id, t.duration_ms, t.file_path,
-         t.file_format, t.file_size, t.bitrate, t.track_number, t.disc_number,
-         t.mbid, t.genre, t.added_at, t.updated_at,
-         albums.title, artists.name
-ORDER BY count(*) DESC, t.id
 LIMIT $2;
 
 -- name: ListLastPlayedArtistsForUser :many
@@ -231,17 +236,28 @@ LIMIT $2;
 -- a derived cover_album_id via a representative-album lateral join (most
 -- recent album that has cover_art_path set). album_count joined for the
 -- ArtistRef wire shape.
-SELECT sqlc.embed(a),
+--
-       cov.id        AS cover_album_id,
+-- Earlier shape iterated `FROM artists a` and ran a LATERAL play_events
-       cnt.album_count::bigint AS album_count,
+-- subquery per artist — O(total_artists) plan even for users with a
-       max_started.started_at::timestamptz AS last_played_at
+-- handful of plays. New shape aggregates the user's plays by artist
-FROM artists a
+-- via the play_events → tracks join up front (uses
-JOIN LATERAL (
+-- play_events_user_track_idx + tracks pkey lookups), then attaches
-    SELECT max(pe.started_at) AS started_at
+-- the artist row and lateral cover/count subqueries only for the
+-- artists that actually appear. Distinct-artists set is small for a
+-- typical user, so cost is bounded by play history not library size.
+WITH user_plays AS (
+    SELECT t.artist_id, max(pe.started_at) AS last_started
     FROM play_events pe
     JOIN tracks t ON t.id = pe.track_id
-    WHERE pe.user_id = $1 AND t.artist_id = a.id
+    WHERE pe.user_id = $1
-) max_started ON max_started.started_at IS NOT NULL
+    GROUP BY t.artist_id
+)
+SELECT sqlc.embed(a),
+       cov.id AS cover_album_id,
+       cnt.album_count::bigint AS album_count,
+       up.last_started::timestamptz AS last_played_at
+FROM user_plays up
+JOIN artists a ON a.id = up.artist_id
 LEFT JOIN LATERAL (
     SELECT id FROM albums
     WHERE artist_id = a.id AND cover_art_path IS NOT NULL
@@ -251,7 +267,7 @@ LEFT JOIN LATERAL (
     SELECT count(*) AS album_count
     FROM albums WHERE artist_id = a.id
 ) cnt ON true
-ORDER BY max_started.started_at DESC, a.id
+ORDER BY up.last_started DESC, a.id
 LIMIT $2;
 
 -- name: ListRediscoverAlbumsForUser :many

web/src/routes/+page.svelte

@@ -39,6 +39,10 @@
     (systemPlaylistsQ.data?.owned ?? []).find((p) => p.system_variant === 'for_you') ?? null
   );
 
+  const discoverPlaylist = $derived(
+    (systemPlaylistsQ.data?.owned ?? []).find((p) => p.system_variant === 'discover') ?? null
+  );
+
   const songsLikePlaylists = $derived(
     (systemPlaylistsQ.data?.owned ?? [])
       .filter((p) => p.system_variant === 'songs_like_artist')
@@ -48,7 +52,7 @@
   const userPlaylists = $derived(userPlaylistsQ.data?.owned ?? []);
 
   type PlaceholderVariant = 'building' | 'failed' | 'pending' | 'seed-needed';
-  function placeholderVariant(slot: 'for-you' | 'songs-like'): PlaceholderVariant {
+  function placeholderVariant(slot: 'for-you' | 'discover' | 'songs-like'): PlaceholderVariant {
     const s = systemStatusQ.data;
     if (!s) return 'pending';
     if (s.in_flight) return 'building';
@@ -71,7 +75,16 @@
       out.push({ kind: 'placeholder', label: 'For You', variant: placeholderVariant('for-you') });
     }
 
-    // Slots 2-4: Songs-like (real first, padded with placeholders).
+    // Slot 2: Discover (real or placeholder). Server emits this with
+    // system_variant='discover' once the recommendation engine has
+    // eligible tracks.
+    if (discoverPlaylist) {
+      out.push({ kind: 'real', playlist: discoverPlaylist });
+    } else {
+      out.push({ kind: 'placeholder', label: 'Discover', variant: placeholderVariant('discover') });
+    }
+
+    // Slots 3-5: Songs-like (real first, padded with placeholders).
     for (let i = 0; i < 3; i++) {
       if (songsLikePlaylists[i]) {
         out.push({ kind: 'real', playlist: songsLikePlaylists[i] });

web/src/routes/page.test.ts

@@ -54,10 +54,11 @@ beforeEach(() => {
 afterEach(() => vi.clearAllMocks());
 
 describe('home Playlists section', () => {
-  test('renders 4 placeholder cards when no playlists exist', () => {
+  test('renders 5 placeholder cards when no playlists exist', () => {
+    // Slot layout: For-You, Discover, 3× Songs-like.
     render(Page);
     const placeholders = screen.queryAllByTestId('playlist-placeholder-card');
-    expect(placeholders).toHaveLength(4);
+    expect(placeholders).toHaveLength(5);
   });
 
   test('building status sets variant=building on placeholders', () => {
@@ -103,6 +104,8 @@ describe('home Playlists section', () => {
     render(Page);
     expect(screen.getByText('For You')).toBeInTheDocument();
     const placeholders = screen.queryAllByTestId('playlist-placeholder-card');
-    expect(placeholders).toHaveLength(3); // 3 songs-like slots
+    // 1 Discover + 3 Songs-like slots = 4 placeholders alongside the
+    // real For-You tile.
+    expect(placeholders).toHaveLength(4);
   });
 });