test(e2e): sweep the binding names a spec calls

Four specs still called `library.Library.GetTracks` after #281 replaced
it, and the suite reported twenty failures across transport, bottom-bar
and reduced-motion specs — none of which mention the library list. A
binding call carries only a method id, so a stale name fails at runtime
in whichever spec happens to call it.

`binding-names.spec.ts` reads every spec and harness file, extracts the
names they pass as strings, and checks them against the map derived
from the generated bindings tree. It asserts first that it read
something: a sweep over an empty glob passes and proves nothing.

It immediately found a second thing: `play-count.spec.ts` asserted that
a play refetched no collection by matching a `GetAll` prefix, which
matches exactly one real name (`GetAllLibrariesWithTrackCounts`) — so
the assertion held whatever the app refetched. It names the four
collection bindings now.

.gitea/workflows/android-apk.yml

@@ -68,7 +68,7 @@ jobs:
       SHA: ${{ github.sha }}
       REF_NAME: ${{ github.ref_name }}
       DEBIAN_FRONTEND: noninteractive
-      GO_VERSION: '1.25.0'
+      GO_VERSION: '1.26.0'
       npm_config_store_dir: /cache/pnpm-store
       # The Go half wants the NDK; the Gradle half wants a platform.
       ANDROID_HOME: /cache/android-sdk

.gitea/workflows/ci.yml

@@ -36,7 +36,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  GO_VERSION: '1.25.0'
+  GO_VERSION: '1.26.0'
   # Shared by all three Playwright consumers (@playwright/cli, e2e/'s
   # @playwright/test, frontend/'s Vitest provider).  See the browsers
   # step in job 2 for why that is not the whole story.
@@ -53,7 +53,7 @@ jobs:
   check:
     runs-on: ubuntu-latest
     container:
-      # Not golang:1.25 — this job runs `make ui-test`, which is Vitest
+      # Not golang:1.26 — this job runs `make ui-test`, which is Vitest
       # *browser* mode and needs a Chromium and its system libraries
       # anyway, so the "fast job needs no browser" split does not hold.
       # Not the Playwright image either: e2e/ pins @playwright/test
@@ -107,15 +107,32 @@ jobs:
       # Conventional Commits.  `.releaserc.yml` has always derived the
       # version from the commit type; until now nothing checked that the
       # type was one it recognises, so a malformed subject silently meant
-      # "no release".  BEFORE is the push's previous tip and is absent or
+      # "no release".
-      # all-zeros for a new branch, in which case only the tip is linted.
+      #
+      # **On a `pull_request` there is no `before`.**  Gitea leaves
+      # `github.event.before` empty for one, so this step fell through to
+      # bare `make commit-check`, which lints `git log -1` — the tip
+      # alone.  Every other commit the branch would bring was first
+      # examined by *main's* post-merge run, which is a green PR that
+      # stops being true after the merge, and which happened twice (#254).
+      # The PR's base is the stand-in: the range below already excludes
+      # what the base shares with the branch, because base advances on
+      # main and those commits stay reachable from it.
+      #
+      # Both are handed to the shell rather than chosen in an expression:
+      # `github.event.issue.number` in unclaim.yml is this repo's proof
+      # that payload fields resolve, and the shell then falls back to
+      # today's behaviour for a dispatch run or a missing field instead of
+      # depending on how `&&`/`||` treat an absent context.
       - name: Commit messages
         working-directory: /src
         env:
-          BEFORE: ${{ github.event.before }}
+          PR_BASE: ${{ github.event.pull_request.base.sha }}
+          PUSH_BEFORE: ${{ github.event.before }}
         run: |
           set -eu
-          if [ -n "${BEFORE:-}" ] && [ "${BEFORE#0000000}" = "$BEFORE" ] \
+          BEFORE="${PR_BASE:-${PUSH_BEFORE:-}}"
+          if [ -n "$BEFORE" ] && [ "${BEFORE#0000000}" = "$BEFORE" ] \
              && git cat-file -e "$BEFORE^{commit}" 2>/dev/null; then
             make commit-check RANGE="$BEFORE..$SHA"
           else

.gitea/workflows/desktop-assets.yml

@@ -48,7 +48,7 @@ jobs:
       SHA: ${{ github.sha }}
       REF_NAME: ${{ github.ref_name }}
       DEBIAN_FRONTEND: noninteractive
-      GO_VERSION: '1.25.0'
+      GO_VERSION: '1.26.0'
       npm_config_store_dir: /cache/pnpm-store
     steps:
       # The same set ci.yml's check job installs: the app is cgo, and

.gitea/workflows/index-artifact.yml

@@ -68,7 +68,7 @@ jobs:
       # claim with a test behind it now (cmd/indexbuild/deps_test.go),
       # because the v3 migration quietly broke it and this job was where
       # that surfaced.
-      image: golang:1.25
+      image: golang:1.26
       # This host path must exist on the runner and be listed verbatim in
       # act_runner's container.valid_volumes. It holds explore-staging/
       # (counts.bin + state.json) and yj.db — the checkpoint that makes
@@ -148,6 +148,49 @@ jobs:
           sha256sum /tmp/core-index.db.zst | tee /tmp/core-index.db.zst.sha256
           ls -lh /tmp/core-index.db.zst
 
+      # Nothing is published until it has been imported by the code that
+      # imports it on a user's machine. The exporter and the importer are
+      # two descriptions of one storage format, and every other tier tests
+      # the importer against a *fixture* rather than against the file being
+      # shipped — a second description free to be wrong in the same
+      # direction as the code reading it.
+      #
+      # That is how #258 reached everyone: the importer positioned its batch
+      # walk with a Go `string` cursor against this file's 16-byte `mbid`
+      # column, and SQLite neither coerces between TEXT and BLOB nor
+      # complains about the comparison — so the walk merged no rows and
+      # never advanced, and no install could finish its first index build.
+      # The fixture guarding that walk writes the old text encoding, and the
+      # only compact fixture is one row, below the batch size, so the bound
+      # query never ran. Both were green throughout.
+      #
+      # Running it here is also what keeps the failure cheap: the previous
+      # artifact stays published while this runs, so a failure costs one
+      # stale catalog rather than an empty one for every install.
+      #
+      # `-tags indexbuild` because this container has no GTK and the default
+      # tag set links the app through Wails. The `--- PASS` grep is not
+      # decoration — the test skips without the path, and a skip is
+      # indistinguishable from a pass in a summary line.
+      - name: Import the exported artifact as a client does
+        if: steps.maintain.outputs.complete == 'true' && steps.maintain.outputs.changed == 'true'
+        working-directory: /src
+        env:
+          YJ_CORE_INDEX_ARTIFACT: /tmp/core-index.db.zst
+        run: |
+          set -eu
+          log=/tmp/import-check.log
+          if ! go test -tags indexbuild -count=1 -timeout 30m -v \
+            -run TestImportPublishedArtifact ./backend/explore/ > "$log" 2>&1;
+          then
+            tail -60 "$log"
+            echo "::error::The artifact does not import; not publishing it."
+            exit 1
+          fi
+          cat "$log"
+          grep -qF -- 'PASS: TestImportPublishedArtifact' "$log"
+          echo "::notice::The artifact imports as a client would merge it."
+
       - name: Publish to the Gitea package registry
         if: steps.maintain.outputs.complete == 'true' && steps.maintain.outputs.changed == 'true'
         run: |

.pi/skills/yellowjacket-dev/references/android-tier.md

@@ -647,7 +647,7 @@ window.__yj = { call(name, args) {
 That turns the device into a tier that can be *driven* rather than only
 looked at — `__yj.call("player.Player.LoadFile", [path])` and
 `__yj.call("library.Library.AddLibrary", ["/sdcard/Music/..."])` are how
-#53 was measured. Names are the Go ones (`GetTracks`, not
+#53 was measured. Names are the Go ones (`GetTrackTable`, not
 `GetAllTracks`); an unknown one comes back as a plain
 `unknown bound method name`, so a wrong guess is loud.
 

.pi/skills/yellowjacket-dev/references/harness.md

@@ -57,6 +57,21 @@ behind `YJ_TESTCTL=1`, which `scripts/dev-headless.sh` sets and
   staging the work that would produce it — job progress, download
   progress, scan progress. It calls `events.Deliver`, which *errors*
   when the event reaches nobody, so a `200` means it really arrived.
+- **State you stage, you own** (#168). Nothing resets those stores, so
+  clear yours in `test.afterEach` with the same event that staged it
+  (`emit('JobsChanged', [])`) — the store replaces its list from every
+  snapshot, so `testctl` needs no special case. **Measured: this does
+  not currently cross a spec boundary**, because every test gets a fresh
+  page and `JobStore.init()` refetches `GetJobs()` from a backend
+  registry that `/__test/emit` never writes to. Stated anyway, because
+  it costs one line and the leak needs only one spec that keeps a page
+  alive — but do not cite #168 for a symptom you have not reproduced.
+- **Measure against the thing next to you, not an absolute
+  coordinate.** An absolute number in a shell measurement is also a
+  claim about everything above it — `contentTop === 0` quietly asserts
+  "and no background job is running", which is not what that spec was
+  about or could arrange, while `contentTop === jobBandBottom` is true
+  either way. This is the half of #168 that stands on its own.
 - **`restore` is slow** (~40 s in the suite) because it copies every
   table. Prefer snapshotting once and restoring only when a spec
   genuinely mutates state.

.planning/NOTES.md

@@ -5078,3 +5078,106 @@ last rendered card.
 ("ask the virtualizer for a larger overscan") is therefore not
 available without patching a private, which is why the request is
 issued ahead of the element instead.
+
+## Declined, and recorded nowhere else (2026-09-25, #256)
+
+When CLAUDE.md was cut down to rules, most of its "considered and
+declined" paragraphs already had a home in a code or config comment
+beside what they explain. These three did not:
+
+- **`touch-action: manipulation` was declined** (#54). The 300ms tap
+  delay it is offered for is already absent on a `width=device-width`
+  viewport; what it would actually change is the gesture stack #63 tuned
+  by measurement on the reference device.
+- **There is no "Go to Genre"** in the phone row menu (#67). That menu
+  replaces name links a phone cannot use, and there has never been a
+  genre link to replace — it would be new navigation, which wants its
+  own issue.
+- **The overlaid queue has no tap-outside gutter on a phone** (#171).
+  The drawer-style gutter would buy the affordance by taking width off a
+  full-screen surface on a 424px viewport; back and a 44px close button
+  answer it instead.
+
+## What the library payloads actually cost (measured 2026-10-05, desktop dev build)
+
+Plan 023 (#279–#284). Measured against `make sandbox-seed-bulk`
+(50 000 tracks, 371 MB `yj.db` in the smaller copy) with the desktop
+dev build and `e2e/perf/measure.mjs`, which grew a `memory` section for
+it: backend RSS and peak from `/proc`, the Go heap from pprof, the
+page's JS heap and DOM counters from CDP, and the bytes every binding
+returned, before and after the first open of Tracks.
+
+| | before | after #281 | after #280 |
+|---|---|---|---|
+| Backend RSS at rest | 543 MB | 296 MB | 189 MB |
+| Backend peak RSS | 571 MB | 337 MB | 281 MB |
+| Go heap held | 361 MB | 125 MB | 7 MB |
+| JS heap at rest | 31.8 MB | 18.0 MB | 5.2 MB |
+| Binding bytes at rest | 35.9 MB | 12.1 MB | 1.7 MB |
+| JS heap after a browse | 36.5 MB | 22.7 MB | 23.1 MB |
+| Tracks first open → first row | 38 ms | 26 ms | 1 255 ms |
+| Slowest first view open | 44 ms | 57 ms | 76 ms |
+
+Six things worth keeping:
+
+- **The number that fell was not the number being optimised.** The
+  binding payload fell 20.5 → 10.45 MB (dictionary-encoded columns) and
+  35.9 → 12.1 MB, but what made the backend's RSS fall by 354 MB was
+  the *fetch not happening*: `GetTracks` was the only thing in the app
+  that allocated 170 MB transiently (`sqlcgen.GetTracks` 80 MB, `json/v2`
+  128 MB, `slices.Grow` 77 MB, `bytes.Clone` 47 MB of 484 MB total
+  `alloc_space`). Encoding smaller would not have touched that.
+- **A `dictionary` is what makes dropping fields the wrong trade.** The
+  first version of the column table left out `LastPlayed` and the three
+  larger cover tiers, and then a "select all → edit tags" over 50 000
+  tracks had to fetch every track back to open the dialog: 3 071 ms
+  against 88 ms before. Interning means the repeated strings are nearly
+  free, so the fields belong in the table; what fixed it in the end was
+  neither — the Tracks view hands the dialog the rows it already has.
+  **A payload optimisation that removes a field is a new fetch waiting
+  to be written.**
+- **`mmap_size` is a bound, not an allocation.** #283 read as "64 MB of
+  mapping per connection", and the RSS of the database mapping is 46 MB
+  whether the bound is 64 MB or 16 MB, because a mapping costs what the
+  working set touches. Quartering it moved no query either (1 172 →
+  1 197 ms for the whole track list, 106 → 124 ms for the album list, 6
+  → 8 ms for an FTS search — all inside the run-to-run spread). Kept for
+  the phone, where the bound is the address space the low-memory killer
+  reads.
+- **A view that is first paint is a view that is active.** `index.html`
+  renders a `<track-list>`, so the track list was connected at launch
+  and fetched 12 MB whoever was looking at — and the fix was not in the
+  component but in the shell: markup is not a decision about which view
+  the launch lands on, so the seed is `view-hidden` and the first
+  navigation is what activates it. Hover and keyboard focus on a nav
+  item prefetch, which is the ~100 ms before the click.
+- **The remaining second is the transport, not the data.** A cold open
+  of Tracks on 50 000 tracks is 1 255 ms, and a *raw* binding call for
+  the same table is 1 118–1 382 ms: none of it is the TypeScript decode
+  or the render. It is the Go-side query, the column encode and Wails
+  encoding every result twice — once for a debug log that is off
+  (#286). Splitting that number is what says where to go next, and the
+  answer was not where the payload work had been.
+- **A test named for the behaviour caught the thing the design missed.**
+  The source sweep that pins "the whole-library track array has one
+  reader" was written to catch the four call sites #279 had already
+  converted; it found `smart-playlist-editor`, which built its value
+  suggestions from the same array and would have gone silently empty
+  once nothing loaded it. The suggestion box is a backend query now
+  (`SuggestSmartPlaylistValues`).
+
+And two things about this machine, since they cost a cycle each:
+
+- **`make ui-test` is not reliable at load average 14.** Under the
+  workstation's own background services, the browser provider's module
+  fetches fail in a different handful of files each run ("Failed to
+  import test file", "Cannot connect to the iframe") while every test
+  that runs passes. `--maxWorkers=1 --retry=2` reduces it; individual
+  files always pass. A failure list that changes between runs is the
+  environment, not the branch.
+- **A measurement run inherits the machine's mood.** The first
+  after-#281 numbers said view opens had doubled (albums 27 → 78 ms,
+  settings 44 → 179 ms, Tracks first row 38 → 105 ms). Re-running
+  unchanged gave 26 ms and 57 ms. The tell was the same one
+  `NOTES.md` already records twice: before and after suspiciously
+  equal, or suspiciously worse, across *unrelated* measurements.

CONTRIBUTING.md

@@ -13,7 +13,7 @@ frontend, bridged by [Wails v3](https://wails.io/).
 
 | Tool | Version |
 |------|---------|
-| Go | 1.25+ |
+| Go | 1.26+ |
 | Node.js | 22+ |
 | pnpm | 10+ |
 | Wails CLI | v3 — vendored, no install needed (`go tool wails3`) |

backend/app.go

@@ -499,6 +499,10 @@ func (yj *YellowJacketApp) OnStartup(ctx context.Context) {
 		PostRemove: yj.explore.InvalidateLibrarySync,
 	})
 
+	// A deleted playlist must not leave the queue's "Playing from"
+	// label pointing at it.
+	yj.playlist.SetOnPlaylistDeleted(yj.queue.DropSourceForPlaylist)
+
 	// Register playback finished handler to drive queue auto-advance.
 	yj.player.SetPlaybackFinishedHandler(yj.queue.OnPlaybackFinished)
 
@@ -775,6 +779,8 @@ func (yj *YellowJacketApp) startJanitor() {
 	}
 
 	yj.janitor.Register(maintenance.ExpiredHTTPCacheJob(yj.database))
+	yj.janitor.Register(maintenance.StaleArtistMetadataJob(yj.database))
+	yj.janitor.Register(maintenance.StaleSearchClicksJob(yj.database))
 	yj.janitor.Register(maintenance.OrphanedCoverFilesJob(
 		yj.database, coversDir, library.CoverArtFileSet,
 	))

backend/database/database.go

@@ -54,9 +54,19 @@ type DB struct {
 // form is silently ignored, which is why WAL was never actually on.
 const (
 	writeDSNParams = "?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)"
-	readDSNParams  = "?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)" +
+	// The read pool's own page cache and mapping bound, sized by
+	// measurement rather than by appetite (#283).  On a 50 000-track
+	// library, halving the cache and quartering the mapping moved no
+	// query — 1 172 → 1 197 ms for the whole track list, 106 → 124 ms
+	// for the album list, 6 → 8 ms for an FTS search, all inside the
+	// run-to-run spread — and the RSS of the database mapping was 46 MB
+	// under both settings, because a mapping's cost is what the working
+	// set touches, not the bound.  The bound is what matters on a
+	// phone, where five connections' worth of address space is the
+	// thing the low-memory killer reads (cf. #52).
+	readDSNParams = "?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)" +
 		"&_pragma=query_only(true)&_pragma=synchronous(NORMAL)" +
-		"&_pragma=cache_size(-8000)&_pragma=mmap_size(67108864)"
+		"&_pragma=cache_size(-2000)&_pragma=mmap_size(16777216)"
 	// readPoolConns bounds concurrent read connections.  A handful is
 	// plenty for interactive search + art/lookup fan-out and keeps WAL
 	// reader overhead small.
@@ -354,8 +364,8 @@ func applyPRAGMAs(ctx context.Context, db *sql.DB) error {
 	pragmas := []string{
 		"PRAGMA foreign_keys = ON",
 		"PRAGMA synchronous = NORMAL",
-		"PRAGMA cache_size = -8000",
+		"PRAGMA cache_size = -2000",
-		"PRAGMA mmap_size = 67108864",
+		"PRAGMA mmap_size = 16777216",
 	}
 
 	for _, pragma := range pragmas {

backend/database/lyrics_search.go

@@ -151,16 +151,28 @@ func (d *DB) SetLyrics(audioFileID int64, lyrics, source, recordingMBID string)
 	return d.upsertLyricsIndex(audioFileID, lyrics)
 }
 
-// upsertLyricsIndex refreshes a single file's entry in the contentless
+// DeleteLyricsIndex removes one file's entry from the contentless
-// lyrics_index.  contentless_delete=1 makes the DELETE valid; an empty
+// lyrics_index.  It is called wherever a file row is deleted — the
-// lyrics string leaves the row deleted.
+// `lyrics` table cascades with its file, but the FTS entry does not and
-func (d *DB) upsertLyricsIndex(audioFileID int64, lyrics string) error {
+// would otherwise accumulate for the life of the install (#249).
+func (d *DB) DeleteLyricsIndex(audioFileID int64) error {
 	if _, err := d.db.ExecContext(d.Ctx,
 		"DELETE FROM lyrics_index WHERE rowid = ?", audioFileID,
 	); err != nil {
 		return fmt.Errorf("could not delete lyrics_index row: %w", err)
 	}
 
+	return nil
+}
+
+// upsertLyricsIndex refreshes a single file's entry in the contentless
+// lyrics_index.  contentless_delete=1 makes the DELETE valid; an empty
+// lyrics string leaves the row deleted.
+func (d *DB) upsertLyricsIndex(audioFileID int64, lyrics string) error {
+	if err := d.DeleteLyricsIndex(audioFileID); err != nil {
+		return err
+	}
+
 	if strings.TrimSpace(lyrics) == "" {
 		return nil
 	}

backend/database/sql/queries/audio_files.sql

@@ -117,6 +117,9 @@ WHERE library_id = COALESCE(NULLIF(CAST(sqlc.arg(library_id) AS INTEGER), 0), li
 -- name: GetTrackByPath :one
 SELECT * FROM track_metadata WHERE file_path = ? LIMIT 1;
 
+-- name: GetTracksByPaths :many
+SELECT * FROM track_metadata WHERE file_path IN (sqlc.slice('paths'));
+
 -- name: GetTracksByAlbum :many
 SELECT * FROM track_metadata
 WHERE album_id = sqlc.arg(album_id)

backend/database/sql/sqlcgen/audio_files.sql.go

@@ -830,6 +830,71 @@ func (q *Queries) GetTracksByGenre(ctx context.Context, arg GetTracksByGenrePara
 	return items, nil
 }
 
+const getTracksByPaths = `-- name: GetTracksByPaths :many
+SELECT id, file_path, length_milliseconds, title, artist_name, track_number, disc_number, album, genre, year, release_year, composer, file_type, sample_rate, bit_depth, channels, bitrate, file_size, library_id, play_count, last_played, cover_art_path, artist_mbid, release_group_mbid, recording_mbid, album_id, artist_id FROM track_metadata WHERE file_path IN (/*SLICE:paths*/?)
+`
+
+func (q *Queries) GetTracksByPaths(ctx context.Context, paths []string) ([]TrackMetadatum, error) {
+	query := getTracksByPaths
+	var queryParams []interface{}
+	if len(paths) > 0 {
+		for _, v := range paths {
+			queryParams = append(queryParams, v)
+		}
+		query = strings.Replace(query, "/*SLICE:paths*/?", strings.Repeat(",?", len(paths))[1:], 1)
+	} else {
+		query = strings.Replace(query, "/*SLICE:paths*/?", "NULL", 1)
+	}
+	rows, err := q.db.QueryContext(ctx, query, queryParams...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []TrackMetadatum
+	for rows.Next() {
+		var i TrackMetadatum
+		if err := rows.Scan(
+			&i.ID,
+			&i.FilePath,
+			&i.LengthMilliseconds,
+			&i.Title,
+			&i.ArtistName,
+			&i.TrackNumber,
+			&i.DiscNumber,
+			&i.Album,
+			&i.Genre,
+			&i.Year,
+			&i.ReleaseYear,
+			&i.Composer,
+			&i.FileType,
+			&i.SampleRate,
+			&i.BitDepth,
+			&i.Channels,
+			&i.Bitrate,
+			&i.FileSize,
+			&i.LibraryID,
+			&i.PlayCount,
+			&i.LastPlayed,
+			&i.CoverArtPath,
+			&i.ArtistMbid,
+			&i.ReleaseGroupMbid,
+			&i.RecordingMbid,
+			&i.AlbumID,
+			&i.ArtistID,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
 const lookupTrackMetaByPaths = `-- name: LookupTrackMetaByPaths :many
 SELECT id, file_path, title, artist_name, album, cover_art_path,
        artist_mbid, release_group_mbid, recording_mbid

backend/download/candidate_shape_test.go

@@ -0,0 +1,248 @@
+package download
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// Multi-disc rips, single-track results and coverage counted in tracks
+// rather than files (#270).
+
+func TestParsePathReadsTheDiscFromItsFolder(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		path   string
+		disc   int
+		track  int
+		folder string
+	}{
+		{`\share\Pink Floyd - The Wall (1979)\CD2\03 Hey You.flac`, 2, 3, "The Wall"},
+		{`\share\The Wall\Disc 1\01 In The Flesh.flac`, 1, 1, "The Wall"},
+		{`\share\The Wall\[Disk-2]\01 Hey You.flac`, 2, 1, "The Wall"},
+		{`\share\The Wall\CD1 - Live\04 Mother.flac`, 1, 4, "The Wall"},
+		// The filename's own disc number is more specific than the folder.
+		{`\share\The Wall\CD1\2-05 Comfortably Numb.flac`, 2, 5, "The Wall"},
+		// Not a disc folder: a number is required.
+		{`\share\CDs\The Wall\01 In The Flesh.flac`, 0, 1, "The Wall"},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.path, func(t *testing.T) {
+			t.Parallel()
+
+			got := ParsePath(tc.path)
+			if got.Disc != tc.disc || got.Track != tc.track || got.Folder != tc.folder {
+				t.Errorf(
+					"ParsePath = disc %d track %d folder %q, want %d %d %q",
+					got.Disc, got.Track, got.Folder, tc.disc, tc.track, tc.folder,
+				)
+			}
+		})
+	}
+}
+
+func TestAlbumDir(t *testing.T) {
+	t.Parallel()
+
+	cases := map[string]string{
+		`\share\Album\CD1\01 A.flac`:  "/share/Album",
+		`\share\Album\01 A.flac`:      "/share/Album",
+		`CD1\01 A.flac`:               "CD1",
+		`\share\CD Collection\01.mp3`: "/share/CD Collection",
+	}
+
+	for in, want := range cases {
+		if got := AlbumDir(in); got != want {
+			t.Errorf("AlbumDir(%q) = %q, want %q", in, got, want)
+		}
+	}
+}
+
+// One album shared as CD1/CD2 is one candidate, named after the album.
+func TestSlskdGroupsDiscFoldersIntoOneCandidate(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.responses = []slskdResponse{{
+		Username: "peer",
+		Files: []slskdFile{
+			{Filename: `\m\The Wall\CD1\01 In The Flesh.flac`, Size: 1},
+			{Filename: `\m\The Wall\CD1\02 The Thin Ice.flac`, Size: 1},
+			{Filename: `\m\The Wall\CD2\01 Hey You.flac`, Size: 1},
+			{Filename: `\m\The Wall\CD2\02 Is There Anybody Out There.flac`, Size: 1},
+		},
+	}}
+
+	s, _ := newStubSlskd(t, stub)
+
+	got, err := s.Search(context.Background(), Download{Query: "the wall"})
+	if err != nil {
+		t.Fatalf("Search: %v", err)
+	}
+
+	if len(got) != 1 {
+		t.Fatalf("got %d candidates, want the two discs as one", len(got))
+	}
+
+	if got[0].Title != "The Wall" || len(got[0].Files) != 4 {
+		t.Errorf(
+			"candidate = %q with %d files, want \"The Wall\" with 4",
+			got[0].Title, len(got[0].Files),
+		)
+	}
+}
+
+// A track search matches one file per folder, so a single-track request
+// must accept a one-file folder that an album request rightly drops.
+func TestSlskdKeepsASingleFileForATrackRequest(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.responses = []slskdResponse{{
+		Username: "peer",
+		Files: []slskdFile{
+			{Filename: `\m\OK Computer\02 Paranoid Android.flac`, Size: 1},
+		},
+	}}
+
+	s, _ := newStubSlskd(t, stub)
+
+	track, err := s.Search(context.Background(), Download{
+		RecordingMBID: "rec-1", Artist: "Radiohead", Album: "Paranoid Android",
+	})
+	if err != nil {
+		t.Fatalf("Search: %v", err)
+	}
+
+	if len(track) != 1 {
+		t.Errorf("track request: got %d candidates, want 1", len(track))
+	}
+
+	album, err := s.Search(context.Background(), Download{
+		ReleaseMBID: "rel-1", Artist: "Radiohead", Album: "OK Computer",
+	})
+	if err != nil {
+		t.Fatalf("Search: %v", err)
+	}
+
+	if len(album) != 0 {
+		t.Errorf("album request: got %d candidates, want the one-file folder dropped", len(album))
+	}
+}
+
+// Two discs with a file of the same name both reach staging, each under
+// its disc folder, where the importer reads the disc number from.
+func TestSlskdCollectKeepsDiscFolders(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	s, downloads := newStubSlskd(t, stub)
+
+	for _, disc := range []string{"CD1", "CD2"} {
+		dir := filepath.Join(downloads, disc)
+		if err := os.MkdirAll(dir, 0o750); err != nil {
+			t.Fatalf("mkdir: %v", err)
+		}
+
+		if err := os.WriteFile(
+			filepath.Join(dir, "01 Intro.flac"), []byte(disc), 0o600,
+		); err != nil {
+			t.Fatalf("write: %v", err)
+		}
+	}
+
+	dst := t.TempDir()
+
+	got, err := s.collect(Candidate{Files: []CandidateFile{
+		{Path: `\m\Album\CD1\01 Intro.flac`, IsAudio: true},
+		{Path: `\m\Album\CD2\01 Intro.flac`, IsAudio: true},
+	}}, dst)
+	if err != nil {
+		t.Fatalf("collect: %v", err)
+	}
+
+	if len(got.Files) != 2 {
+		t.Fatalf("collected %d files, want 2", len(got.Files))
+	}
+
+	for _, disc := range []string{"CD1", "CD2"} {
+		data, err := os.ReadFile(filepath.Join(dst, disc, "01 Intro.flac"))
+		if err != nil || string(data) != disc {
+			t.Errorf("%s's file missing or overwritten: %q, %v", disc, data, err)
+		}
+
+		if hint := ParsePath(filepath.Join(dst, disc, "01 Intro.flac")); hint.Disc == 0 {
+			t.Errorf("staged %s file lost its disc number", disc)
+		}
+	}
+}
+
+// A two-disc release whose discs both number from 01 aligns completely
+// once the disc comes from the folder; before, disc 2's 01 collided with
+// disc 1's.
+func TestMultiDiscCandidateAlignsEveryTrack(t *testing.T) {
+	t.Parallel()
+
+	dl := Download{
+		ReleaseMBID: "the-wall",
+		Artist:      "Pink Floyd",
+		Album:       "The Wall",
+		Expected: []ExpectedTrack{
+			{DiscNumber: 1, Position: 1, Title: "In the Flesh?"},
+			{DiscNumber: 1, Position: 2, Title: "The Thin Ice"},
+			{DiscNumber: 2, Position: 1, Title: "Hey You"},
+			{DiscNumber: 2, Position: 2, Title: "Is There Anybody Out There?"},
+		},
+	}
+
+	c := Candidate{
+		Title: "The Wall",
+		Files: []CandidateFile{
+			{Path: `\m\Pink Floyd - The Wall\CD1\01 In the Flesh.flac`, Size: 1},
+			{Path: `\m\Pink Floyd - The Wall\CD1\02 The Thin Ice.flac`, Size: 1},
+			{Path: `\m\Pink Floyd - The Wall\CD2\01 Hey You.flac`, Size: 1},
+			{Path: `\m\Pink Floyd - The Wall\CD2\02 Is There Anybody Out There.flac`, Size: 1},
+		},
+	}
+
+	got := Score(dl, c, 50, AutoDownloadPrefs{})
+
+	if got.Match.Completeness != 1 {
+		t.Errorf("completeness = %f, want 1", got.Match.Completeness)
+	}
+
+	if got.Match.AlbumFit < 0.99 {
+		t.Errorf("album fit = %f, want the album's own name to match", got.Match.AlbumFit)
+	}
+
+	if got.Match.Overall < minMatch {
+		t.Errorf("match = %f, want it to clear the auto-pick bar %f", got.Match.Overall, minMatch)
+	}
+}
+
+// Ten files against a ten-track album is not a complete album when only
+// three of them are its tracks.
+func TestCompletenessCountsTracksNotFiles(t *testing.T) {
+	t.Parallel()
+
+	dl := okComputer()
+
+	c := Candidate{Title: "OK Computer", Files: []CandidateFile{
+		{Path: `\m\Radiohead - OK Computer\Airbag.flac`, Size: 1},
+		{Path: `\m\Radiohead - OK Computer\Paranoid Android.flac`, Size: 1},
+		{Path: `\m\Radiohead - OK Computer\Exit Music (For a Film).flac`, Size: 1},
+		{Path: `\m\Radiohead - OK Computer\Creep.flac`, Size: 1},
+	}}
+
+	got := Score(dl, c, 50, AutoDownloadPrefs{})
+
+	if got.Match.Completeness > 0.76 {
+		t.Errorf(
+			"completeness = %f with 3 of 4 tracks present, want at most 0.75",
+			got.Match.Completeness,
+		)
+	}
+}

backend/download/concurrency_test.go

@@ -47,7 +47,7 @@ func grabAll(
 		go func() {
 			defer wg.Done()
 
-			f.manager.grab(ctx, dl, candidate, nil)
+			f.manager.grab(ctx, dl, candidate, nil, false)
 		}()
 	}
 
@@ -79,9 +79,9 @@ func TestConcurrencyForPrefersOverrideThenKind(t *testing.T) {
 		want int
 	}{
 		{
-			name: "slskd defaults to one",
+			name: "slskd defaults to a few peers",
 			cfg:  Config{Kind: KindSlskd},
-			want: 1,
+			want: 3,
 		},
 		{
 			name: "usenet defaults higher",
@@ -92,9 +92,9 @@ func TestConcurrencyForPrefersOverrideThenKind(t *testing.T) {
 			name: "explicit override wins",
 			cfg: Config{
 				Kind:     KindSlskd,
-				Settings: map[string]string{concurrencyKey: "3"},
+				Settings: map[string]string{concurrencyKey: "1"},
 			},
-			want: 3,
+			want: 1,
 		},
 		{
 			name: "nonsense override falls back",
@@ -102,7 +102,7 @@ func TestConcurrencyForPrefersOverrideThenKind(t *testing.T) {
 				Kind:     KindSlskd,
 				Settings: map[string]string{concurrencyKey: "not a number"},
 			},
-			want: 1,
+			want: 3,
 		},
 		{
 			name: "zero override falls back",
@@ -110,7 +110,7 @@ func TestConcurrencyForPrefersOverrideThenKind(t *testing.T) {
 				Kind:     KindSlskd,
 				Settings: map[string]string{concurrencyKey: "0"},
 			},
-			want: 1,
+			want: 3,
 		},
 		{
 			name: "unknown kind falls back to the global default",
@@ -126,9 +126,9 @@ func TestConcurrencyForPrefersOverrideThenKind(t *testing.T) {
 	}
 }
 
-// The reason the per-provider cap exists: a Soulseek daemon capped at
+// The reason the per-provider cap exists: a daemon capped at one
-// one transfer must serialize, even when the global cap would allow
+// transfer must serialize, even when the global cap would allow more and
-// more and the user has queued several albums at once.
+// the user has queued several albums at once.
 func TestPerProviderCapSerializesTransfers(t *testing.T) {
 	t.Parallel()
 
@@ -142,6 +142,7 @@ func TestPerProviderCapSerializesTransfers(t *testing.T) {
 		ID:       1,
 		Kind:     KindSlskd,
 		Priority: 50,
+		Settings: map[string]string{concurrencyKey: "1"},
 	}, slow)
 
 	// Three requests against the same one-at-a-time provider.
@@ -210,8 +211,8 @@ func TestSyncSemaphoresReplacesChangedLimits(t *testing.T) {
 	f.manager.installProvider(Config{ID: 1, Kind: KindSlskd}, nil)
 
 	first := f.manager.semaphoreFor(1)
-	if cap(first) != 1 {
+	if want := kindConcurrency[KindSlskd]; cap(first) != want {
-		t.Fatalf("slskd semaphore cap = %d, want 1", cap(first))
+		t.Fatalf("slskd semaphore cap = %d, want %d", cap(first), want)
 	}
 
 	// Same limit: the semaphore is kept, so in-flight accounting is not

backend/download/fallback_test.go

@@ -0,0 +1,261 @@
+package download
+
+import (
+	"context"
+	"errors"
+	"os"
+	"testing"
+)
+
+// A transfer that fails on one copy of an album is not a failed
+// download while another acceptable copy exists.  On Soulseek the usual
+// failure is one peer being offline, with several others offering the
+// same folder.
+
+var errPeerOffline = errors.New("peer went offline")
+
+func TestManagerFallsBackToTheNextCandidate(t *testing.T) {
+	t.Parallel()
+
+	f := newManagerFixture(t)
+
+	// The failing source ranks first on priority, so the fallback is
+	// what reaches the one that works.
+	bad := fakeWithAlbum(1, "offline-peer", ".flac")
+	bad.GrabErr = errPeerOffline
+	good := fakeWithAlbum(2, "online-peer", ".flac")
+
+	f.manager.installProvider(Config{ID: 1, Priority: 90}, bad)
+	f.manager.installProvider(Config{ID: 2, Priority: 10}, good)
+
+	dl := fourTrackDownload()
+
+	if _, err := f.manager.Start(context.Background(), dl); err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+
+	waitForDownloadState(t, f.store, dl.ID, StateComplete)
+
+	if bad.GrabCalls != 1 || good.GrabCalls != 1 {
+		t.Errorf(
+			"grabs: failing=%d working=%d, want 1 and 1",
+			bad.GrabCalls, good.GrabCalls,
+		)
+	}
+
+	// The abandoned attempt's staging goes with it; only a request that
+	// fails outright keeps its staging for inspection.
+	waitFor(t, func() bool {
+		entries, err := os.ReadDir(f.staging.Root())
+
+		return err == nil && len(entries) == 0
+	}, "the failed attempt's staging was never released")
+}
+
+// Falling back must not lower the bar.  A second choice outside the
+// user's guardrails is not a choice auto-pick may make, first or second.
+func TestManagerFallbackRespectsTheGuardrails(t *testing.T) {
+	t.Parallel()
+
+	f := newManagerFixture(t)
+	f.manager.SetPreferences(AutoDownloadPrefs{MaxSizeMB: 50})
+
+	bad := fakeWithAlbum(1, "offline-peer", ".flac")
+	bad.GrabErr = errPeerOffline
+	bad.Candidates[0].TotalSize = 40 << 20
+
+	huge := fakeWithAlbum(2, "oversized", ".flac")
+	huge.Candidates[0].TotalSize = 900 << 20
+
+	f.manager.installProvider(Config{ID: 1, Priority: 90}, bad)
+	f.manager.installProvider(Config{ID: 2, Priority: 10}, huge)
+
+	dl := fourTrackDownload()
+
+	if _, err := f.manager.Start(context.Background(), dl); err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+
+	waitForDownloadState(t, f.store, dl.ID, StateFailed)
+
+	if huge.GrabCalls != 0 {
+		t.Errorf("fell back to a candidate over the size ceiling")
+	}
+}
+
+// A copy the user picked by hand is the copy they asked for.  Quietly
+// substituting another is a decision they did not make.
+func TestManagerPickDoesNotFallBack(t *testing.T) {
+	t.Parallel()
+
+	f := newManagerFixture(t)
+
+	bad := fakeWithAlbum(1, "offline-peer", ".flac")
+	bad.GrabErr = errPeerOffline
+	good := fakeWithAlbum(2, "online-peer", ".flac")
+
+	f.manager.installProvider(Config{ID: 1, Priority: 90}, bad)
+	f.manager.installProvider(Config{ID: 2, Priority: 10}, good)
+
+	// A ceiling below both copies parks the result set for the user.
+	f.manager.SetPreferences(AutoDownloadPrefs{MaxSizeMB: 1})
+
+	bad.Candidates[0].TotalSize = 30 << 20
+	good.Candidates[0].TotalSize = 30 << 20
+
+	dl := fourTrackDownload()
+
+	if _, err := f.manager.Start(context.Background(), dl); err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+
+	if err := f.manager.Pick(
+		context.Background(), dl.ID, "offline-peer-cand",
+	); err != nil {
+		t.Fatalf("Pick: %v", err)
+	}
+
+	waitForDownloadState(t, f.store, dl.ID, StateFailed)
+
+	if good.GrabCalls != 0 {
+		t.Errorf("a hand-picked grab fell back to another candidate")
+	}
+}
+
+// Fallback is for surviving an offline peer or two, not for walking a
+// forty-peer list for six hours.
+func TestManagerFallbackIsBounded(t *testing.T) {
+	t.Parallel()
+
+	f := newManagerFixture(t)
+
+	var providers []*FakeProvider
+
+	for i := int64(1); i <= maxGrabAttempts+2; i++ {
+		p := fakeWithAlbum(i, "peer-"+itoa(int(i)), ".flac")
+		p.GrabErr = errPeerOffline
+
+		f.manager.installProvider(Config{ID: i, Priority: 50}, p)
+		providers = append(providers, p)
+	}
+
+	dl := fourTrackDownload()
+
+	if _, err := f.manager.Start(context.Background(), dl); err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+
+	waitForDownloadState(t, f.store, dl.ID, StateFailed)
+
+	grabs := 0
+	for _, p := range providers {
+		grabs += p.GrabCalls
+	}
+
+	if grabs != maxGrabAttempts {
+		t.Errorf("grabs = %d, want %d", grabs, maxGrabAttempts)
+	}
+}
+
+// The veto judges the best candidate *inside* the guardrails, so the
+// grab has to take that one — not the overall best, which may be the
+// very copy the user said not to take unattended.
+func TestManagerAutoPickTakesTheBestEligibleCandidate(t *testing.T) {
+	t.Parallel()
+
+	f := newManagerFixture(t)
+	f.manager.SetPreferences(AutoDownloadPrefs{MaxSizeMB: 50})
+
+	huge := fakeWithAlbum(1, "oversized", ".flac")
+	huge.Candidates[0].TotalSize = 900 << 20
+
+	fits := fakeWithAlbum(2, "fits", ".flac")
+	fits.Candidates[0].TotalSize = 40 << 20
+
+	f.manager.installProvider(Config{ID: 1, Priority: 90}, huge)
+	f.manager.installProvider(Config{ID: 2, Priority: 10}, fits)
+
+	dl := fourTrackDownload()
+
+	ranked, err := f.manager.Start(context.Background(), dl)
+	if err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+
+	if ranked[0].ID != "oversized-cand" {
+		t.Fatalf("fixture: best overall is %s, want the oversized copy", ranked[0].ID)
+	}
+
+	waitForDownloadState(t, f.store, dl.ID, StateComplete)
+
+	if huge.GrabCalls != 0 || fits.GrabCalls != 1 {
+		t.Errorf(
+			"grabs: oversized=%d fits=%d, want 0 and 1",
+			huge.GrabCalls, fits.GrabCalls,
+		)
+	}
+}
+
+// On Soulseek a failure is the peer's, so every folder that peer offered
+// goes with it.  Elsewhere a failure is the release's, and one indexer's
+// other releases are still worth trying.
+func TestRuledOutBy(t *testing.T) {
+	t.Parallel()
+
+	failed := []Candidate{
+		{ID: "slskd:alice:Album", Kind: KindSlskd, ProviderID: 1, Origin: "alice"},
+		{ID: "tracker-1", Kind: KindProwlarr, ProviderID: 2, Origin: "indexer"},
+	}
+
+	cases := []struct {
+		name string
+		c    Candidate
+		want bool
+	}{
+		{
+			name: "the same candidate",
+			c:    Candidate{ID: "tracker-1", Kind: KindProwlarr, ProviderID: 2, Origin: "indexer"},
+			want: true,
+		},
+		{
+			name: "another folder from a failed peer",
+			c: Candidate{
+				ID:         "slskd:alice:Album (2)",
+				Kind:       KindSlskd,
+				ProviderID: 1,
+				Origin:     "alice",
+			},
+			want: true,
+		},
+		{
+			name: "another peer",
+			c:    Candidate{ID: "slskd:bob:Album", Kind: KindSlskd, ProviderID: 1, Origin: "bob"},
+			want: false,
+		},
+		{
+			name: "another release from the same indexer",
+			c:    Candidate{ID: "tracker-2", Kind: KindProwlarr, ProviderID: 2, Origin: "indexer"},
+			want: false,
+		},
+		{
+			name: "a peer of the same name on a different daemon",
+			c: Candidate{
+				ID:         "slskd:alice:Album",
+				Kind:       KindSlskd,
+				ProviderID: 3,
+				Origin:     "alice",
+			},
+			want: false,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			if got := ruledOutBy(tc.c, failed); got != tc.want {
+				t.Errorf("ruledOutBy = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}

backend/download/keyedlock.go

@@ -0,0 +1,77 @@
+package download
+
+import (
+	"context"
+	"sync"
+)
+
+// keyedLock is a set of mutexes created on demand, one per key, that
+// honour a context while waiting.  An entry lives only while someone
+// holds or waits on it, so a key per Soulseek peer or per folder name
+// does not accumulate for the life of the process.
+type keyedLock[K comparable] struct {
+	mu   sync.Mutex
+	held map[K]*keyedEntry
+}
+
+type keyedEntry struct {
+	ch chan struct{}
+
+	// refs counts holders and waiters; the entry is dropped at zero.
+	refs int
+}
+
+// acquire blocks until k is free or ctx ends, and returns the function
+// that frees it.
+func (l *keyedLock[K]) acquire(ctx context.Context, k K) (func(), error) {
+	l.mu.Lock()
+
+	if l.held == nil {
+		l.held = map[K]*keyedEntry{}
+	}
+
+	e, ok := l.held[k]
+	if !ok {
+		e = &keyedEntry{ch: make(chan struct{}, 1)}
+		l.held[k] = e
+	}
+
+	e.refs++
+
+	l.mu.Unlock()
+
+	select {
+	case e.ch <- struct{}{}:
+	case <-ctx.Done():
+		l.drop(k, e)
+
+		return nil, ctx.Err()
+	}
+
+	var once sync.Once
+
+	return func() {
+		once.Do(func() {
+			<-e.ch
+			l.drop(k, e)
+		})
+	}, nil
+}
+
+func (l *keyedLock[K]) drop(k K, e *keyedEntry) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	e.refs--
+	if e.refs == 0 {
+		delete(l.held, k)
+	}
+}
+
+// size reports how many keys are held or awaited, for tests.
+func (l *keyedLock[K]) size() int {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	return len(l.held)
+}

backend/download/manager.go

@@ -59,13 +59,15 @@ const concurrencyKey = "maxConcurrent"
 // A single global cap is the wrong shape here: usenet and torrent
 // clients are built to run many transfers at once and are throttled by
 // bandwidth, while Soulseek transfers come from one person's home
-// upload slot.  Hitting the same peer with parallel requests gets you
+// upload slot.  Politeness there is per *peer* — asking one user for two
-// queued behind everyone else at best and banned at worst, so slskd is
+// folders at once gets you queued behind everyone else at best and
-// capped at one — the polite number, and the one that actually
+// banned at worst — and the manager holds that line separately, one
-// completes fastest, because a Soulseek peer serves one file at a time
+// grab per peer (peerLocks).  Two different users do not compete for
-// regardless of how many you ask for.
+// anyone's slot, so the daemon-wide number only bounds how many peers
+// are asked at once, and one slow peer no longer serialises every other
+// Soulseek download behind it.
 var kindConcurrency = map[Kind]int{
-	KindSlskd:       1,
+	KindSlskd:       3,
 	KindYtDlp:       2,
 	KindQBittorrent: 4,
 	KindSABnzbd:     4,
@@ -155,6 +157,11 @@ type Manager struct {
 	semMu   sync.Mutex
 	provSem map[int64]chan struct{}
 
+	// peerLocks holds one grab per Soulseek peer, taken before any
+	// slot: a grab waiting for a busy peer must not sit on a provider
+	// slot another peer could be using.
+	peerLocks keyedLock[peerKey]
+
 	// delegatePoll is how often delegating managers are asked for
 	// status.  A field rather than the constant so tests can drive the
 	// full delegate flow without sleeping through it.
@@ -577,12 +584,12 @@ func (m *Manager) Start(
 		))
 	}
 
-	if m.AutoPickable(dl, ranked) {
+	if pick, ok := autoPick(dl, ranked, m.preferences()); ok {
 		if job != nil {
 			job.Logf(jobs.LevelInfo, "Auto-selected best candidate")
 		}
 
-		go m.grab(context.WithoutCancel(ctx), dl, ranked[0], job)
+		go m.grab(context.WithoutCancel(ctx), dl, pick, job, true)
 
 		return ranked, nil
 	}
@@ -622,6 +629,13 @@ func (m *Manager) Attempt(
 		return false, veto, nil
 	}
 
+	pick, ok := autoPick(dl, ranked, m.preferences())
+	if !ok {
+		// Unreachable while autoPick and AutoPickVeto agree; kept so a
+		// future divergence refuses rather than grabbing blind.
+		return false, "no candidate clears the auto-download bar", nil
+	}
+
 	if err := m.store.CreateDownload(ctx, dl); err != nil {
 		return false, "", err
 	}
@@ -643,7 +657,7 @@ func (m *Manager) Attempt(
 		))
 	}
 
-	go m.grab(context.WithoutCancel(ctx), dl, ranked[0], job)
+	go m.grab(context.WithoutCancel(ctx), dl, pick, job, true)
 
 	return true, "", nil
 }
@@ -678,7 +692,7 @@ func (m *Manager) Pick(
 
 	job := m.startJob(dl)
 
-	go m.grab(context.WithoutCancel(ctx), dl, *chosen, job)
+	go m.grab(context.WithoutCancel(ctx), dl, *chosen, job, false)
 
 	return nil
 }
@@ -702,13 +716,20 @@ func (m *Manager) Cancel(ctx context.Context, downloadID string) error {
 	return nil
 }
 
-// grab drives one candidate all the way to the library.  It runs on its
+// grab drives one request all the way to the library.  It runs on its
 // own goroutine and owns the job from here on.
+//
+// When fallback is set and a candidate's transfer fails, the next
+// candidate that auto-pick would itself have accepted is tried in its
+// place (see nextCandidate).  It is set for the two unattended routes
+// and not for a candidate the user picked by hand: they chose that copy,
+// and quietly substituting another is a decision they did not make.
 func (m *Manager) grab(
 	ctx context.Context,
 	dl Download,
 	c Candidate,
 	job *jobs.Handle,
+	fallback bool,
 ) {
 	ctx, cancel := context.WithTimeout(ctx, grabTimeout)
 	defer cancel()
@@ -723,6 +744,99 @@ func (m *Manager) grab(
 		m.actMu.Unlock()
 	}()
 
+	var failed []Candidate
+
+	for {
+		out := m.attemptGrab(ctx, dl, c, job)
+		if out.err == nil {
+			m.finishGrab(ctx, dl, out.item, out.imported, job)
+
+			return
+		}
+
+		failed = append(failed, c)
+
+		next, ok := m.nextCandidate(ctx, dl, failed, out, fallback)
+		if !ok {
+			m.failDownload(ctx, job, dl.ID, out.err)
+
+			return
+		}
+
+		m.logger.Info(
+			"download candidate failed; trying the next",
+			"download", dl.ID,
+			"failed", c.ID,
+			"next", next.ID,
+			"error", out.err,
+		)
+
+		if job != nil {
+			job.Logf(jobs.LevelWarn, fmt.Sprintf(
+				"%s failed (%v); trying %s instead",
+				describeCandidate(c), out.err, describeCandidate(next),
+			))
+		}
+
+		// The failed attempt's staging holds at most a partial folder
+		// nobody is going to import, and the next attempt reserves its
+		// own.  Only the final failure keeps its staging for inspection.
+		if out.item.StagingDir != "" {
+			if err := m.staging.Release(out.item.StagingDir); err != nil {
+				m.logger.Warn("could not release staging dir", "error", err)
+			}
+		}
+
+		c = next
+	}
+}
+
+// maxGrabAttempts bounds how many candidates one request will try.  A
+// popular album can have dozens of peers; the point of falling back is
+// to survive the ordinary one or two that are offline, not to walk the
+// whole list for six hours.
+const maxGrabAttempts = 3
+
+// peerKey names one Soulseek user on one daemon.  The same username on
+// two daemons is two logins and two queues.
+type peerKey struct {
+	provider int64
+	peer     string
+}
+
+// peerKeyFor returns the peer a candidate is fetched from, when the
+// source is one where asking a peer for two things at once is rude.
+func peerKeyFor(c Candidate) (peerKey, bool) {
+	if c.Kind != KindSlskd || c.Origin == "" {
+		return peerKey{}, false
+	}
+
+	return peerKey{provider: c.ProviderID, peer: c.Origin}, true
+}
+
+// grabOutcome is how one candidate's attempt ended.
+type grabOutcome struct {
+	item     DownloadItem
+	imported ImportResult
+	err      error
+
+	// retryable reports whether another candidate might succeed where
+	// this one failed: the transfer failed, or delivered too little of
+	// the album.  Anything else — no staging space, no library root, a
+	// tag write failing — would fail the next candidate identically.
+	retryable bool
+}
+
+// attemptGrab takes one candidate through transfer and import.  It
+// records the item's own failure, but not the download's: whether the
+// download has failed is the caller's decision, since another candidate
+// may yet succeed.
+func (m *Manager) attemptGrab(
+	ctx context.Context,
+	dl Download,
+	c Candidate,
+	job *jobs.Handle,
+) grabOutcome {
 	// Who will move the bytes is decided before any slot is taken, so
 	// the transfer waits in its own provider's queue rather than in a
 	// global one.  A delegate takes no slot at all: the transfer is
@@ -731,21 +845,26 @@ func (m *Manager) grab(
 	// work against our budget.
 	plan, err := m.planTransfer(dl, c)
 	if err != nil {
-		m.failDownload(ctx, job, dl.ID, err)
+		return grabOutcome{err: err}
-
-		return
 	}
 
 	if !plan.delegated() {
+		if key, ok := peerKeyFor(c); ok {
+			release, err := m.peerLocks.acquire(ctx, key)
+			if err != nil {
+				return grabOutcome{err: err}
+			}
+
+			defer release()
+		}
+
 		provSem := m.semaphoreFor(plan.transportID)
 
 		select {
 		case provSem <- struct{}{}:
 			defer func() { <-provSem }()
 		case <-ctx.Done():
-			m.failDownload(ctx, job, dl.ID, ctx.Err())
+			return grabOutcome{err: ctx.Err()}
-
-			return
 		}
 
 		globalSem := m.globalSem()
@@ -754,9 +873,7 @@ func (m *Manager) grab(
 		case globalSem <- struct{}{}:
 			defer func() { <-globalSem }()
 		case <-ctx.Done():
-			m.failDownload(ctx, job, dl.ID, ctx.Err())
+			return grabOutcome{err: ctx.Err()}
-
-			return
 		}
 	}
 
@@ -771,24 +888,30 @@ func (m *Manager) grab(
 
 	dir, err := m.staging.Reserve(item.ID)
 	if err != nil {
-		m.failDownload(ctx, job, dl.ID, err)
+		return grabOutcome{err: err}
-
-		return
 	}
 
 	item.StagingDir = dir
 
 	if err := m.store.CreateItem(ctx, item); err != nil {
-		m.failDownload(ctx, job, dl.ID, err)
+		return grabOutcome{item: item, err: err}
+	}
 
-		return
+	fail := func(err error, retryable bool) grabOutcome {
+		if serr := m.store.SetItemState(
+			ctx, item.ID, StateFailed, err.Error(),
+		); serr != nil {
+			m.logger.Warn("could not record item failure", "error", serr)
+		}
+
+		return grabOutcome{item: item, err: err, retryable: retryable}
 	}
 
 	result, err := m.transfer(ctx, dl, item, plan, job)
 	if err != nil {
-		m.failItem(ctx, job, item, dl.ID, err)
+		// A delegate's failure is the external manager's verdict on the
-
+		// whole request, not on one copy of it.
-		return
+		return fail(err, !plan.delegated())
 	}
 
 	m.setStates(ctx, dl.ID, item.ID, StateImporting)
@@ -798,42 +921,116 @@ func (m *Manager) grab(
 		job.SetStages(importStages(2))
 	}
 
-	var imported ImportResult
-
 	if result.Delegated {
 		// The external manager already placed and tagged these files in
 		// its own library.  Moving them out from under a system that is
 		// still managing them would be worse than useless, so the files
 		// are recorded where they are and the library scan picks them
 		// up in place.
-		imported = ImportResult{Paths: result.Files}
-
 		if job != nil {
 			job.Logf(jobs.LevelInfo, fmt.Sprintf(
 				"External manager imported %d files; recording them in place",
 				len(result.Files),
 			))
 		}
-	} else {
-		opts := m.importOptions()
-		opts.WriteTags = true
 
-		opts.LibraryRoot, err = m.library.LibraryPath(dl.LibraryID)
+		return grabOutcome{
-		if err != nil {
+			item:     item,
-			m.failItem(ctx, job, item, dl.ID,
+			imported: ImportResult{Paths: result.Files},
-				fmt.Errorf("resolve library root: %w", err))
-
-			return
-		}
-
-		imported, err = m.importer.Import(ctx, dl, result, opts)
-		if err != nil {
-			m.failItem(ctx, job, item, dl.ID, err)
-
-			return
 		}
 	}
 
+	opts := m.importOptions()
+	opts.WriteTags = true
+
+	opts.LibraryRoot, err = m.library.LibraryPath(dl.LibraryID)
+	if err != nil {
+		return fail(fmt.Errorf("resolve library root: %w", err), false)
+	}
+
+	imported, err := m.importer.Import(ctx, dl, result, opts)
+	if err != nil {
+		return fail(err, errors.Is(err, ErrTooIncomplete))
+	}
+
+	return grabOutcome{item: item, imported: imported}
+}
+
+// nextCandidate picks the candidate to try after the ones in failed.
+//
+// It only ever offers a candidate auto-pick would have taken on its own
+// (autoAcceptable), so falling back cannot lower the bar an unattended
+// download is held to: the second choice has to clear the same gates
+// the first did.
+//
+// On Soulseek a failure belongs to the *peer* — offline, refusing, or
+// holding us in a queue — so every folder that peer offered is skipped
+// with it.  Elsewhere a failure belongs to the release, and only that
+// candidate is.
+func (m *Manager) nextCandidate(
+	ctx context.Context,
+	dl Download,
+	failed []Candidate,
+	out grabOutcome,
+	fallback bool,
+) (Candidate, bool) {
+	if !fallback || !out.retryable || ctx.Err() != nil ||
+		len(failed) >= maxGrabAttempts {
+		return Candidate{}, false
+	}
+
+	m.resMu.RLock()
+	ranked := m.results[dl.ID]
+	m.resMu.RUnlock()
+
+	prefs := m.preferences()
+
+	for _, c := range ranked {
+		if ruledOutBy(c, failed) || !autoAcceptable(dl, c, prefs) {
+			continue
+		}
+
+		return c, true
+	}
+
+	return Candidate{}, false
+}
+
+// ruledOutBy reports whether a failure among failed also rules out c.
+func ruledOutBy(c Candidate, failed []Candidate) bool {
+	for _, f := range failed {
+		if c.ID == f.ID && c.ProviderID == f.ProviderID {
+			return true
+		}
+
+		if c.Kind == KindSlskd && f.Kind == KindSlskd &&
+			c.ProviderID == f.ProviderID && c.Origin != "" &&
+			c.Origin == f.Origin {
+			return true
+		}
+	}
+
+	return false
+}
+
+// describeCandidate names a candidate for the job log.
+func describeCandidate(c Candidate) string {
+	if c.Origin != "" {
+		return fmt.Sprintf("%q from %s", c.Title, c.Origin)
+	}
+
+	return fmt.Sprintf("%q", c.Title)
+}
+
+// finishGrab records a successful import and retires what the request
+// was holding.
+func (m *Manager) finishGrab(
+	ctx context.Context,
+	dl Download,
+	item DownloadItem,
+	imported ImportResult,
+	job *jobs.Handle,
+) {
 	if err := m.store.SetItemImported(
 		ctx, item.ID, imported.Paths,
 	); err != nil {
@@ -1177,23 +1374,6 @@ func (m *Manager) failDownload(
 	}
 }
 
-// failItem records an item-level failure and fails its download.
-func (m *Manager) failItem(
-	ctx context.Context,
-	job *jobs.Handle,
-	item DownloadItem,
-	downloadID string,
-	err error,
-) {
-	if serr := m.store.SetItemState(
-		ctx, item.ID, StateFailed, err.Error(),
-	); serr != nil {
-		m.logger.Warn("could not record item failure", "error", serr)
-	}
-
-	m.failDownload(ctx, job, downloadID, err)
-}
-
 // startJob registers the request in the background jobs panel.
 func (m *Manager) startJob(dl Download) *jobs.Handle {
 	if m.jobsReg == nil {

backend/download/pathmatch.go

@@ -66,6 +66,14 @@ var (
 
 	// separatorPattern splits "Artist - Album" style folder names.
 	separatorPattern = regexp.MustCompile(`\s+[-–—]\s+`)
+
+	// discFolderPattern matches a directory that holds one disc of an
+	// album rather than the album: "CD1", "CD 2", "Disc 3", "Disk-1",
+	// "[Disc 2]", "CD1 - The Early Years".  A number is required, so a
+	// folder merely called "CDs" is not one.
+	discFolderPattern = regexp.MustCompile(
+		`(?i)^\s*[\[(]?\s*(?:cd|disc|disk)\s*[-_.#]?\s*(\d{1,2})\b`,
+	)
 )
 
 // FormatForPath returns the audio format implied by a path's extension,
@@ -94,16 +102,63 @@ type TrackHint struct {
 	Folder string
 }
 
+// discFolder reports whether a directory name is one disc of an album,
+// and which.
+func discFolder(name string) (int, bool) {
+	m := discFolderPattern.FindStringSubmatch(name)
+	if m == nil {
+		return 0, false
+	}
+
+	n, err := strconv.Atoi(m[1])
+	if err != nil || n == 0 {
+		return 0, false
+	}
+
+	return n, true
+}
+
+// AlbumDir is the directory that holds a file's *album*: its parent,
+// or its grandparent when the parent is a disc folder.
+//
+// Multi-disc rips are shared as `Album/CD1/…` and `Album/CD2/…`, and
+// grouping candidates by the immediate parent split one album into two
+// half-albums, each titled "CD1".  Neither could clear the completeness
+// or album-title bars, so a multi-disc release could not be auto-picked
+// at all.  A disc folder at the root has no album above it and is
+// returned as it is.
+func AlbumDir(p string) string {
+	dir := path.Dir(strings.ReplaceAll(p, `\`, "/"))
+
+	if _, ok := discFolder(path.Base(dir)); !ok {
+		return dir
+	}
+
+	parent := path.Dir(dir)
+	if parent == "." || parent == "/" || parent == "" {
+		return dir
+	}
+
+	return parent
+}
+
 // ParsePath extracts what it can from one candidate file path.
 func ParsePath(p string) TrackHint {
 	// Soulseek paths are Windows-style; normalize before splitting.
 	norm := strings.ReplaceAll(p, `\`, "/")
 	base := path.Base(norm)
-	folder := path.Base(path.Dir(norm))
 
 	name := strings.TrimSuffix(base, path.Ext(base))
 
-	hint := TrackHint{Folder: cleanAlbumName(folder)}
+	// The album's name is the album directory's, not a disc folder's,
+	// and the disc folder is where a multi-disc rip says which disc a
+	// file is on.  A disc number in the filename ("2-01 …") is more
+	// specific and overrides it below.
+	hint := TrackHint{Folder: cleanAlbumName(path.Base(AlbumDir(norm)))}
+
+	if disc, ok := discFolder(path.Base(path.Dir(norm))); ok {
+		hint.Disc = disc
+	}
 
 	if m := trackNumPattern.FindStringSubmatch(name); m != nil {
 		if m[1] != "" {
@@ -203,21 +258,72 @@ func AnnotateFiles(files []CandidateFile) []CandidateFile {
 
 // matchFiles aligns a candidate's audio files to the expected tracklist
 // and returns the per-file assignment plus the mean title similarity of
-// the aligned pairs.
+// the aligned pairs.  alignFiles is the same alignment with the
+// duration evidence as well.
+func matchFiles(
+	files []CandidateFile,
+	expected []ExpectedTrack,
+) ([]CandidateFile, float64) {
+	a := alignFiles(files, expected)
+
+	return a.files, a.titleFit
+}
+
+// alignment is what aligning a candidate to a tracklist found.
+type alignment struct {
+	files []CandidateFile
+
+	// titleFit is the mean title similarity over aligned pairs.
+	titleFit float64
+
+	// durationFit is the mean duration agreement over aligned pairs
+	// where both sides state a length, and timedPairs is how many such
+	// pairs there were.
+	durationFit float64
+	timedPairs  int
+	aligned     int
+}
+
+// durationAgreement scores how well a file's length matches the
+// expected track's, in 0..1.  Rips of the same master differ by a
+// second or two of silence; a different edit, a live take or a
+// truncated file differs by tens of seconds.
+func durationAgreement(got, want int64) float64 {
+	const (
+		exactMillis = 3_000
+		wrongMillis = 30_000
+	)
+
+	d := got - want
+	if d < 0 {
+		d = -d
+	}
+
+	switch {
+	case d <= exactMillis:
+		return 1
+	case d >= wrongMillis:
+		return 0
+	default:
+		return 1 - float64(d-exactMillis)/float64(wrongMillis-exactMillis)
+	}
+}
+
+// alignFiles aligns a candidate's audio files to the expected tracklist.
 //
 // Alignment is greedy by score rather than optimal: candidate folders
 // are small (a few dozen files at most) and the common cases — correct
 // track numbers, or clean "NN Title" names — are unambiguous, so the
 // extra machinery of Hungarian assignment buys nothing here.
-func matchFiles(
+func alignFiles(
 	files []CandidateFile,
 	expected []ExpectedTrack,
-) ([]CandidateFile, float64) {
+) alignment {
 	annotated := make([]CandidateFile, len(files))
 	copy(annotated, files)
 
 	if len(expected) == 0 {
-		return annotated, 0
+		return alignment{files: annotated}
 	}
 
 	hints := make([]TrackHint, len(annotated))
@@ -230,8 +336,19 @@ func matchFiles(
 	var (
 		total   float64
 		matched int
+
+		durTotal float64
+		timed    int
 	)
 
+	// timing adds a pair's duration evidence when both sides state one.
+	timing := func(f CandidateFile, e ExpectedTrack) {
+		if f.LengthMillis > 0 && e.LengthMillis > 0 {
+			durTotal += durationAgreement(f.LengthMillis, e.LengthMillis)
+			timed++
+		}
+	}
+
 	// Pass 1: trust explicit track numbers when they are unique and in
 	// range.  A folder that numbers its files correctly is the strong
 	// case, and title comparison only adds noise there.
@@ -250,6 +367,8 @@ func matchFiles(
 
 		total += autotag.TitleSimilarity(hints[i].Title, expected[idx].Title)
 		matched++
+
+		timing(annotated[i], expected[idx])
 	}
 
 	// Pass 2: title similarity for whatever is left.
@@ -284,13 +403,26 @@ func matchFiles(
 
 		total += bestSim
 		matched++
+
+		timing(annotated[i], expected[bestIdx])
 	}
 
 	if matched == 0 {
-		return annotated, 0
+		return alignment{files: annotated}
 	}
 
-	return annotated, total / float64(matched)
+	a := alignment{
+		files:      annotated,
+		titleFit:   total / float64(matched),
+		timedPairs: timed,
+		aligned:    matched,
+	}
+
+	if timed > 0 {
+		a.durationFit = durTotal / float64(timed)
+	}
+
+	return a
 }
 
 // indexForPosition finds the expected track at a disc/track position.

backend/download/peer_concurrency_test.go

@@ -0,0 +1,224 @@
+package download
+
+import (
+	"context"
+	"errors"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+)
+
+// Soulseek politeness is per peer, not per daemon (#272).
+
+func TestKeyedLockSerialisesOneKeyOnly(t *testing.T) {
+	t.Parallel()
+
+	var l keyedLock[string]
+
+	ctx := context.Background()
+
+	releaseA, err := l.acquire(ctx, "a")
+	if err != nil {
+		t.Fatalf("acquire a: %v", err)
+	}
+
+	// Another key is free while "a" is held.
+	releaseB, err := l.acquire(ctx, "b")
+	if err != nil {
+		t.Fatalf("acquire b: %v", err)
+	}
+
+	releaseB()
+
+	// The same key waits, and gives up with its context.
+	short, cancel := context.WithTimeout(ctx, 20*time.Millisecond)
+	defer cancel()
+
+	if _, err := l.acquire(short, "a"); !errors.Is(err, context.DeadlineExceeded) {
+		t.Fatalf("second acquire of a held key = %v, want the deadline", err)
+	}
+
+	releaseA()
+	releaseA() // Idempotent: a second call must not free someone else's hold.
+
+	if n := l.size(); n != 0 {
+		t.Errorf("%d keys left behind, want none once nobody holds or waits", n)
+	}
+}
+
+// grabEach runs one grab per candidate and returns a function that waits
+// for all of them; grabAll's reasons for waiting apply.
+func grabEach(t *testing.T, f managerFixture, cands []Candidate) func() {
+	t.Helper()
+
+	ctx := context.Background()
+
+	var wg sync.WaitGroup
+
+	for i, c := range cands {
+		dl := fourTrackDownload()
+		dl.ID = "dl-" + string(rune('a'+i))
+
+		if err := f.store.CreateDownload(ctx, dl); err != nil {
+			t.Fatalf("CreateDownload: %v", err)
+		}
+
+		wg.Add(1)
+
+		go func() {
+			defer wg.Done()
+
+			f.manager.grab(ctx, dl, c, nil, false)
+		}()
+	}
+
+	return func() {
+		done := make(chan struct{})
+
+		go func() {
+			wg.Wait()
+			close(done)
+		}()
+
+		select {
+		case <-done:
+		case <-time.After(5 * time.Second):
+			t.Error("transfers did not finish")
+		}
+	}
+}
+
+func slskdCandidates(p *FakeProvider, peers ...string) []Candidate {
+	out := make([]Candidate, 0, len(peers))
+
+	for i, peer := range peers {
+		c := p.Candidates[0]
+		c.ID = c.ID + "-" + itoa(i)
+		c.Kind = KindSlskd
+		c.ProviderID = 1
+		c.Origin = peer
+		out = append(out, c)
+	}
+
+	return out
+}
+
+// Three albums from one user are asked for one at a time, even though
+// the daemon would allow three transfers.
+func TestOnePeerIsAskedForOneThingAtATime(t *testing.T) {
+	t.Parallel()
+
+	f := newManagerFixture(t)
+	f.manager.SetMaxConcurrent(4)
+
+	p := fakeWithAlbum(1, "slskd", ".flac")
+	p.GrabGate = make(chan struct{})
+
+	f.manager.installProvider(Config{ID: 1, Kind: KindSlskd, Priority: 50}, p)
+
+	wait := grabEach(t, f, slskdCandidates(p, "alice", "alice", "alice"))
+
+	waitFor(t, func() bool { return p.GrabCallCount() >= 1 }, "no grab started")
+	time.Sleep(150 * time.Millisecond)
+
+	if got := p.MaxParallelGrabs(); got != 1 {
+		t.Errorf("%d simultaneous grabs from one peer, want 1", got)
+	}
+
+	close(p.GrabGate)
+
+	waitFor(t, func() bool { return p.GrabCallCount() == 3 }, "queued grabs never ran")
+	wait()
+
+	if n := f.manager.peerLocks.size(); n != 0 {
+		t.Errorf("%d peer locks left behind", n)
+	}
+}
+
+// Different users run at once, up to the daemon's cap — the point of
+// the change: one slow peer no longer holds up every other.
+func TestDifferentPeersRunTogether(t *testing.T) {
+	t.Parallel()
+
+	f := newManagerFixture(t)
+	f.manager.SetMaxConcurrent(8)
+
+	p := fakeWithAlbum(1, "slskd", ".flac")
+	p.GrabGate = make(chan struct{})
+
+	f.manager.installProvider(Config{ID: 1, Kind: KindSlskd, Priority: 50}, p)
+
+	wait := grabEach(t, f, slskdCandidates(p, "alice", "bob", "carol", "dave"))
+
+	waitFor(
+		t,
+		func() bool { return p.MaxParallelGrabs() >= kindConcurrency[KindSlskd] },
+		"different peers were serialised",
+	)
+	time.Sleep(100 * time.Millisecond)
+
+	if got := p.MaxParallelGrabs(); got != kindConcurrency[KindSlskd] {
+		t.Errorf("%d simultaneous grabs, want the daemon cap %d", got, kindConcurrency[KindSlskd])
+	}
+
+	close(p.GrabGate)
+	wait()
+}
+
+func TestSlskdLocalFolders(t *testing.T) {
+	t.Parallel()
+
+	s := &slskd{downloadsPath: "/dl"}
+
+	got := s.localFolders(Candidate{Files: []CandidateFile{
+		{Path: `\m\The Wall\CD2\01 Hey You.flac`},
+		{Path: `\m\The Wall\CD1\01 In The Flesh.flac`},
+		{Path: `\m\The Wall\CD1\02 The Thin Ice.flac`},
+	}})
+
+	want := []string{filepath.Join("/dl", "CD1"), filepath.Join("/dl", "CD2")}
+	if len(got) != len(want) || got[0] != want[0] || got[1] != want[1] {
+		t.Errorf("localFolders = %q, want %q", got, want)
+	}
+}
+
+// Two peers' "Greatest Hits" land in one slskd directory, so the second
+// grab does not enqueue until the first has collected its files.
+func TestSlskdSameFolderNameWaits(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	s, downloads := newStubSlskd(t, stub)
+
+	c := Candidate{
+		Payload: map[string]string{"username": "bob"},
+		Files: []CandidateFile{
+			{Path: `\music\Greatest Hits\01 Intro.flac`, Size: 1, IsAudio: true},
+		},
+	}
+
+	release, err := lockSlskdFolders(
+		context.Background(), []string{filepath.Join(downloads, "Greatest Hits")},
+	)
+	if err != nil {
+		t.Fatalf("lock: %v", err)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	defer cancel()
+
+	if _, err := s.Grab(ctx, c, t.TempDir(), nil); !errors.Is(err, context.DeadlineExceeded) {
+		t.Fatalf("Grab = %v, want it to wait on the held folder", err)
+	}
+
+	release()
+
+	stub.mu.Lock()
+	posted := stub.posted
+	stub.mu.Unlock()
+
+	if posted {
+		t.Error("enqueued transfers into a folder another grab held")
+	}
+}

backend/download/provider.go

@@ -236,17 +236,18 @@ func Register(d Descriptor, c Constructor) {
 }
 
 // concurrencyField describes the per-provider transfer limit, with help
-// text explaining why the default is what it is — a user who raises
+// text explaining what the number means where it means something
-// slskd from 1 to 8 and gets themselves queued behind every other
+// unusual: on slskd it counts peers, since each peer is only ever asked
-// Soulseek user deserves to have been warned.
+// for one folder at a time whatever it is set to.
 func concurrencyField(k Kind) Field {
 	help := "Maximum simultaneous transfers from this client."
 
 	if k == KindSlskd {
-		help = "Maximum simultaneous transfers. Soulseek peers serve " +
+		help = "How many Soulseek users to download from at once. " +
-			"one file at a time and queue or ban clients that ask for " +
+			"Each user is only ever asked for one album at a time, " +
-			"more, so 1 is both the polite setting and usually the " +
+			"since peers queue or ban clients that ask for more; " +
-			"fastest."
+			"this bounds how many different users are asked in " +
+			"parallel."
 	}
 
 	return Field{

backend/download/provider_slskd.go

@@ -5,9 +5,12 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"net/url"
 	"os"
 	"path"
 	"path/filepath"
+	"regexp"
+	"slices"
 	"strings"
 	"time"
 
@@ -69,12 +72,34 @@ const (
 	slskdTransferPoll = 3 * time.Second
 
 	// slskdMinFiles is the fewest audio files a folder needs before it
-	// is offered as a candidate.  Soulseek returns a lot of one-file
+	// is offered as a candidate for an album.  Soulseek returns a lot of
-	// noise for common queries.
+	// one-file noise for common queries.  A single-track request takes
+	// one (see minFilesFor).
 	slskdMinFiles = 2
 
 	// slskdHTTPTimeout bounds one API call.
 	slskdHTTPTimeout = 20 * time.Second
+
+	// millisPerSecond converts slskd's whole-second file lengths.
+	millisPerSecond = 1000
+
+	// slskdStallAfter is how long a grab may go without a byte arriving
+	// before the peer is given up on.  It is measured from enqueue, so
+	// it covers a peer that queues us and never starts as well as one
+	// that starts and stops.  Ten minutes is long enough for a short
+	// queue ahead of us to clear and short enough that one unresponsive
+	// peer does not hold slskd's single transfer slot for an evening.
+	slskdStallAfter = 10 * time.Minute
+
+	// slskdAbsentGrace is how long a requested file may be missing from
+	// slskd's transfer list before it is counted as failed.  slskd lists
+	// a transfer as soon as it accepts it, so a file still absent after
+	// a few polls was refused.
+	slskdAbsentGrace = 30 * time.Second
+
+	// slskdCancelTimeout bounds the cleanup that cancels abandoned
+	// transfers.
+	slskdCancelTimeout = 15 * time.Second
 )
 
 func init() {
@@ -134,6 +159,8 @@ type slskd struct {
 	searchPoll   time.Duration
 	searchWait   time.Duration
 	transferPoll time.Duration
+	stallAfter   time.Duration
+	absentGrace  time.Duration
 }
 
 // newSlskd builds the provider from config.
@@ -188,6 +215,8 @@ func newSlskd(
 		searchPoll:    slskdSearchPoll,
 		searchWait:    slskdSearchWait,
 		transferPoll:  slskdTransferPoll,
+		stallAfter:    slskdStallAfter,
+		absentGrace:   slskdAbsentGrace,
 	}, nil
 }
 
@@ -231,14 +260,13 @@ type slskdSearch struct {
 
 // slskdResponse is one peer's answer to a search.
 type slskdResponse struct {
-	Username           string      `json:"username"`
+	Username          string      `json:"username"`
-	HasFreeUploadSlot  bool        `json:"hasFreeUploadSlot"`
+	HasFreeUploadSlot bool        `json:"hasFreeUploadSlot"`
-	QueueLength        int         `json:"queueLength"`
+	QueueLength       int         `json:"queueLength"`
-	UploadSpeed        int64       `json:"uploadSpeed"`
+	UploadSpeed       int64       `json:"uploadSpeed"`
-	Files              []slskdFile `json:"files"`
+	Files             []slskdFile `json:"files"`
-	LockedFileCount    int         `json:"lockedFileCount"`
+	LockedFileCount   int         `json:"lockedFileCount"`
-	FileCount          int         `json:"fileCount"`
+	FileCount         int         `json:"fileCount"`
-	FreeUploadSlotFlag bool        `json:"freeUploadSlots"`
 }
 
 // slskdFile is one file a peer is offering.
@@ -246,7 +274,9 @@ type slskdFile struct {
 	Filename string `json:"filename"`
 	Size     int64  `json:"size"`
 	BitRate  int    `json:"bitRate"`
-	Length   int    `json:"length"`
+
+	// Length is the duration in whole seconds.
+	Length int `json:"length"`
 }
 
 // slskdTransfer is one download's state.
@@ -278,24 +308,89 @@ func (t slskdTransfer) done() (finished, ok bool) {
 // per-folder candidates.  A folder from one peer is the unit a user
 // actually wants: Soulseek has no album concept, but people organise
 // their shares by album directory.
+//
+// Up to two queries run at once — the request as written and a
+// normalised form of it (see slskdQueries) — and their candidates are
+// merged.  They run concurrently rather than as a fallback because the
+// manager gives a provider one search budget, and a Soulseek search
+// spends most of it waiting for peers to answer; a second query after
+// the first would not fit.
 func (s *slskd) Search(ctx context.Context, dl Download) ([]Candidate, error) {
+	queries := slskdQueries(dl)
+	if len(queries) == 0 {
+		return nil, nil
+	}
+
+	type found struct {
+		candidates []Candidate
+		err        error
+	}
+
+	results := make(chan found, len(queries))
+
+	for _, q := range queries {
+		go func(q string) {
+			c, err := s.searchOnce(ctx, q, minFilesFor(dl))
+			results <- found{candidates: c, err: err}
+		}(q)
+	}
+
+	var (
+		out      []Candidate
+		seen     = map[string]bool{}
+		firstErr error
+		answered int
+	)
+
+	for range queries {
+		r := <-results
+		if r.err != nil {
+			s.logger.Debug("slskd search failed", "error", r.err)
+
+			if firstErr == nil {
+				firstErr = r.err
+			}
+
+			continue
+		}
+
+		answered++
+
+		// The same peer's folder turns up under both queries; the ID is
+		// peer and folder, so it is the same candidate.
+		for _, c := range r.candidates {
+			if seen[c.ID] {
+				continue
+			}
+
+			seen[c.ID] = true
+
+			out = append(out, c)
+		}
+	}
+
+	if answered == 0 {
+		return nil, firstErr
+	}
+
+	return out, nil
+}
+
+// searchOnce runs one query to completion and returns its candidates.
+func (s *slskd) searchOnce(
+	ctx context.Context,
+	text string,
+	minFiles int,
+) ([]Candidate, error) {
 	// slskd's search endpoint deserializes id as a .NET Guid server-side,
 	// so it must be a dashed UUID — the app's own newID() (a plain hex
 	// string, used for request/item IDs elsewhere) is rejected with an
 	// HTTP 400 before any search happens.
 	searchID := uuid.NewString()
 
-	body := map[string]any{
+	if err := s.client.post(
-		"id":         searchID,
+		ctx, "/api/v0/searches", s.searchRequest(searchID, text, minFiles), nil,
-		"searchText": dl.SearchText(),
+	); err != nil {
-	}
-
-	if err := s.client.post(ctx, "/api/v0/searches", body, nil); err != nil {
-		return nil, err
-	}
-
-	search, err := s.awaitSearch(ctx, searchID)
-	if err != nil {
 		return nil, err
 	}
 
@@ -307,52 +402,222 @@ func (s *slskd) Search(ctx context.Context, dl Download) ([]Candidate, error) {
 		)
 	}()
 
-	return s.candidatesFrom(search), nil
+	if err := s.awaitSearch(ctx, searchID); err != nil {
+		return nil, err
+	}
+
+	responses, err := s.searchResponses(ctx, searchID)
+	if err != nil {
+		return nil, err
+	}
+
+	return s.candidatesFrom(responses, minFiles), nil
+}
+
+// searchRequest is the body that starts a search.
+//
+// Every option is stated rather than left to the daemon, because
+// slskd's defaults are its own and not ours.  Its search timeout in
+// particular has to finish inside our wait: a search that slskd is still
+// running when we stop polling is results we asked for and discarded.
+// The response and file limits are raised well above what a popular
+// album produces, and the peer filters let slskd drop answers this
+// provider would only score down to nothing — a folder too small to be
+// a candidate, a peer with a queue it will not reach today.
+func (s *slskd) searchRequest(id, text string, minFiles int) map[string]any {
+	const (
+		responseLimit          = 500
+		fileLimit              = 20_000
+		maximumPeerQueueLength = 100
+	)
+
+	// A tenth of the wait is left for the last poll and the responses
+	// fetch.
+	timeout := s.searchWait - s.searchWait/10
+
+	return map[string]any{
+		"id":                       id,
+		"searchText":               text,
+		"searchTimeout":            timeout.Milliseconds(),
+		"responseLimit":            responseLimit,
+		"fileLimit":                fileLimit,
+		"filterResponses":          true,
+		"minimumResponseFileCount": minFiles,
+		"maximumPeerQueueLength":   maximumPeerQueueLength,
+	}
+}
+
+// slskdQueries is what is searched for a request: the request's own
+// search text, and a normalised form of it when that differs.
+//
+// Soulseek matches every term against the file's full path, so each
+// extra word is a filter, and some words filter wrongly:
+//
+//   - edition qualifiers — "(Deluxe Edition)", "[2011 Remaster]" — are
+//     in the catalog's title and rarely in anyone's folder name;
+//   - punctuation splits a term oddly, and a term that starts with "-"
+//     is an *exclusion*, so an album called "-ism" searches for
+//     everything without it;
+//   - "Various Artists" is in no one's path for a compilation.
+//
+// A query the user typed is theirs and is searched exactly as written.
+func slskdQueries(dl Download) []string {
+	primary := strings.TrimSpace(dl.SearchText())
+	if primary == "" {
+		return nil
+	}
+
+	out := []string{primary}
+
+	if dl.Query != "" {
+		return out
+	}
+
+	artist := dl.Artist
+	if isVariousArtists(artist) {
+		artist = ""
+	}
+
+	normal := Download{
+		Artist: normalizeSearchTerms(artist),
+		Album:  normalizeSearchTerms(editionPattern.ReplaceAllString(dl.Album, " ")),
+	}
+
+	if alt := strings.TrimSpace(normal.SearchText()); alt != "" &&
+		!strings.EqualFold(alt, primary) {
+		out = append(out, alt)
+	}
+
+	return out
+}
+
+var (
+	// editionPattern finds an edition qualifier: a bracketed group that
+	// names an edition, or a trailing " - 2011 Remaster".
+	editionPattern = regexp.MustCompile(
+		`(?i)\s*[(\[][^)\]]*\b(?:deluxe|edition|remaster(?:ed)?|expanded|` +
+			`anniversary|bonus|explicit|reissue|special|collector'?s?|` +
+			`version|mono|stereo)\b[^)\]]*[)\]]` +
+			`|\s+-\s+(?:\d{4}\s+)?remaster(?:ed)?\b.*$`,
+	)
+
+	// nonWordPattern is everything that is not a letter or a digit.
+	nonWordPattern = regexp.MustCompile(`[^\p{L}\p{N}]+`)
+)
+
+// normalizeSearchTerms reduces text to plain words.
+func normalizeSearchTerms(s string) string {
+	return strings.Join(strings.Fields(nonWordPattern.ReplaceAllString(s, " ")), " ")
+}
+
+// isVariousArtists reports whether an artist credit is a compilation's
+// placeholder rather than an artist.
+func isVariousArtists(artist string) bool {
+	switch strings.ToLower(strings.TrimSpace(artist)) {
+	case "various artists", "various", "va":
+		return true
+	default:
+		return false
+	}
+}
+
+// minFilesFor is the fewest audio files a folder must offer to be a
+// candidate for this request.
+//
+// Soulseek answers a search with the files that match it, not with the
+// folders they sit in.  An album query matches every file in the album's
+// folder, because the folder name carries the terms; a *track* query
+// usually matches one file per folder.  The two-file floor that filters
+// out one-file noise for an album therefore filtered out every result
+// for a track, and a single-track request could never be served here.
+func minFilesFor(dl Download) int {
+	if dl.RecordingMBID != "" {
+		return 1
+	}
+
+	return slskdMinFiles
 }
 
 // awaitSearch polls until the search completes or the budget runs out.
 // A timeout is not an error: partial Soulseek results are normal and
 // often good enough.
-func (s *slskd) awaitSearch(
+//
-	ctx context.Context,
+// The poll asks for the search's state only.  It used to ask for every
-	searchID string,
+// response on every one-second tick, which for a popular album is the
-) (slskdSearch, error) {
+// same few thousand file entries serialised twenty times to be read
+// once; searchResponses fetches them once at the end.
+func (s *slskd) awaitSearch(ctx context.Context, searchID string) error {
 	deadline := time.Now().Add(s.searchWait)
 
-	var last slskdSearch
-
 	for time.Now().Before(deadline) {
 		select {
 		case <-ctx.Done():
-			return last, fmt.Errorf("%w: search cancelled", ErrSlskdTimeout)
+			return fmt.Errorf("%w: search cancelled", ErrSlskdTimeout)
 		case <-time.After(s.searchPoll):
 		}
 
 		var search slskdSearch
 
 		if err := s.client.get(
-			ctx,
+			ctx, "/api/v0/searches/"+searchID, &search,
-			"/api/v0/searches/"+searchID+"?includeResponses=true",
-			&search,
 		); err != nil {
-			return last, err
+			return err
 		}
 
-		last = search
-
 		if search.IsComplete {
-			return search, nil
+			return nil
 		}
 	}
 
-	return last, nil
+	return nil
 }
 
-// candidatesFrom groups a search's responses into candidates.
+// searchResponses fetches a search's responses once.
-func (s *slskd) candidatesFrom(search slskdSearch) []Candidate {
+//
-	out := make([]Candidate, 0, len(search.Responses))
+// `/searches/{id}/responses` is the endpoint for that; a daemon that
+// does not answer it is asked the older way, with the search itself
+// carrying its responses, so an older slskd degrades to the previous
+// behaviour rather than to no results at all.
+func (s *slskd) searchResponses(
+	ctx context.Context,
+	searchID string,
+) ([]slskdResponse, error) {
+	var responses []slskdResponse
 
-	for _, resp := range search.Responses {
+	err := s.client.get(
+		ctx, "/api/v0/searches/"+searchID+"/responses", &responses,
+	)
+	if err == nil {
+		return responses, nil
+	}
+
+	s.logger.Debug(
+		"slskd responses endpoint failed; asking with the search",
+		"error", err,
+	)
+
+	var search slskdSearch
+
+	if err := s.client.get(
+		ctx,
+		"/api/v0/searches/"+searchID+"?includeResponses=true",
+		&search,
+	); err != nil {
+		return nil, err
+	}
+
+	return search.Responses, nil
+}
+
+// candidatesFrom groups a search's responses into candidates, dropping
+// folders with fewer than minFiles audio files.
+func (s *slskd) candidatesFrom(
+	responses []slskdResponse,
+	minFiles int,
+) []Candidate {
+	out := make([]Candidate, 0, len(responses))
+
+	for _, resp := range responses {
 		for folder, files := range groupByFolder(resp.Files) {
 			audio := 0
 
@@ -372,12 +637,14 @@ func (s *slskd) candidatesFrom(search slskdSearch) []Candidate {
 					Format:  format,
 					Bitrate: f.BitRate,
 					IsAudio: isAudio,
+
+					LengthMillis: int64(f.Length) * millisPerSecond,
 				})
 
 				total += f.Size
 			}
 
-			if audio < slskdMinFiles {
+			if audio < minFiles {
 				continue
 			}
 
@@ -398,13 +665,15 @@ func (s *slskd) candidatesFrom(search slskdSearch) []Candidate {
 	return out
 }
 
-// groupByFolder buckets a peer's files by their containing directory.
+// groupByFolder buckets a peer's files by the album directory they sit
+// in — the containing directory, or the one above it for a disc folder
+// (see AlbumDir), so a multi-disc rip is one candidate and not two.
 func groupByFolder(files []slskdFile) map[string][]slskdFile {
 	out := map[string][]slskdFile{}
 
 	for _, f := range files {
-		norm := strings.ReplaceAll(f.Filename, `\`, "/")
+		dir := AlbumDir(f.Filename)
-		out[path.Dir(norm)] = append(out[path.Dir(norm)], f)
+		out[dir] = append(out[dir], f)
 	}
 
 	return out
@@ -418,7 +687,7 @@ func groupByFolder(files []slskdFile) map[string][]slskdFile {
 func peerHealth(r slskdResponse) float64 {
 	score := 0.35
 
-	if r.HasFreeUploadSlot || r.FreeUploadSlotFlag {
+	if r.HasFreeUploadSlot {
 		score += 0.4
 	}
 
@@ -467,6 +736,21 @@ func (s *slskd) Grab(
 		)
 	}
 
+	// slskd keeps finished transfers listed until someone removes them,
+	// and a transfer is matched to the request by filename.  A record
+	// left by an earlier attempt at the same file from the same peer
+	// would otherwise be read as this attempt's answer the moment the
+	// first poll came back — an old failure failing a transfer that has
+	// not started.  So what is already terminal is noted before enqueueing
+	// and ignored after.
+	release, err := lockSlskdFolders(ctx, s.localFolders(c))
+	if err != nil {
+		return Result{}, err
+	}
+	defer release()
+
+	stale := s.terminalTransferIDs(ctx, username)
+
 	wanted := make([]map[string]any, 0, len(c.Files))
 	for _, f := range c.Files {
 		wanted = append(wanted, map[string]any{
@@ -476,24 +760,122 @@ func (s *slskd) Grab(
 	}
 
 	if err := s.client.post(
-		ctx, "/api/v0/transfers/downloads/"+username, wanted, nil,
+		ctx, slskdDownloadsPath(username), wanted, nil,
 	); err != nil {
 		return Result{}, err
 	}
 
-	if err := s.awaitTransfers(ctx, username, c, onProgress); err != nil {
+	if err := s.awaitTransfers(
+		ctx, username, stale, c, onProgress,
+	); err != nil {
 		return Result{}, err
 	}
 
 	return s.collect(c, dst)
 }
 
+// slskdFolders serialises grabs that land in the same local folder.
+//
+// slskd names a download's directory after the remote *leaf* folder, so
+// two different albums both shared as "Greatest Hits" — or any two
+// multi-disc rips, whose leaves are "CD1" and "CD2" — are written into
+// one directory, and collect finds files by name there.  Run at once,
+// a file one peer never sent is filled by the other peer's file of the
+// same name.  One grab per peer made that impossible; several peers at
+// once makes it likely.  It is package-level and keyed on the full
+// path because two configured clients can share one daemon.
+var slskdFolders keyedLock[string]
+
+// localFolders returns the directories under downloadsPath a candidate's
+// files will be written to, sorted so every grab takes them in the same
+// order and two cannot each hold what the other waits for.
+func (s *slskd) localFolders(c Candidate) []string {
+	var out []string
+
+	for _, f := range c.Files {
+		norm := strings.ReplaceAll(f.Path, `\`, "/")
+		out = append(out, filepath.Join(s.downloadsPath, path.Base(path.Dir(norm))))
+	}
+
+	slices.Sort(out)
+
+	return slices.Compact(out)
+}
+
+// lockSlskdFolders takes every folder in order, releasing what it holds
+// if the context ends part way.
+func lockSlskdFolders(ctx context.Context, folders []string) (func(), error) {
+	releases := make([]func(), 0, len(folders))
+
+	releaseAll := func() {
+		for _, r := range slices.Backward(releases) {
+			r()
+		}
+	}
+
+	for _, f := range folders {
+		r, err := slskdFolders.acquire(ctx, f)
+		if err != nil {
+			releaseAll()
+
+			return nil, err
+		}
+
+		releases = append(releases, r)
+	}
+
+	return releaseAll, nil
+}
+
+// slskdDownloadsPath is the transfers endpoint for one peer.  Soulseek
+// usernames may contain spaces and punctuation, so the name is escaped
+// rather than spliced into the path.
+func slskdDownloadsPath(username string) string {
+	return "/api/v0/transfers/downloads/" + url.PathEscape(username)
+}
+
+// terminalTransferIDs returns the ids of this peer's transfers that are
+// already finished.  Best effort: slskd answers 404 for a peer it has no
+// transfers with, and any failure here means only that there is nothing
+// to ignore.
+func (s *slskd) terminalTransferIDs(
+	ctx context.Context,
+	username string,
+) map[string]bool {
+	transfers, err := s.transfersFor(ctx, username)
+	if err != nil {
+		return nil
+	}
+
+	out := make(map[string]bool, len(transfers))
+
+	for _, t := range transfers {
+		if finished, _ := t.done(); finished && t.ID != "" {
+			out[t.ID] = true
+		}
+	}
+
+	return out
+}
+
 // awaitTransfers polls until every requested file reaches a terminal
-// state.  Soulseek queues are measured in hours, so the only deadline
+// state, the transfer stalls, or the caller gives up.
-// is the caller's context.
+//
+// Soulseek queues are measured in hours, so there is no deadline on the
+// transfer as a whole — but there is one on *progress*.  slskd's
+// transfer limit is one, so a peer that holds us in its queue without
+// sending a byte is not only failing this download, it is holding every
+// other Soulseek download behind it.  After stallAfter with nothing
+// moving the peer is given up on, and the manager tries another.
+//
+// Whatever way this ends short of every file finishing, the transfers
+// still live in slskd are cancelled there.  Returning without doing so
+// leaves the daemon downloading into its own folder for a request
+// nobody is waiting on any more.
 func (s *slskd) awaitTransfers(
 	ctx context.Context,
 	username string,
+	stale map[string]bool,
 	c Candidate,
 	onProgress ProgressFunc,
 ) error {
@@ -502,9 +884,18 @@ func (s *slskd) awaitTransfers(
 		wanted[f.Path] = true
 	}
 
+	var (
+		started      = time.Now()
+		lastProgress = started
+		lastBytes    int64
+		live         []slskdTransfer
+	)
+
 	for {
 		select {
 		case <-ctx.Done():
+			s.cancelTransfers(username, live)
+
 			return fmt.Errorf("%w: transfer cancelled", ErrSlskdTimeout)
 		case <-time.After(s.transferPoll):
 		}
@@ -512,60 +903,177 @@ func (s *slskd) awaitTransfers(
 		transfers, err := s.transfersFor(ctx, username)
 		if err != nil {
 			// A blip talking to the daemon should not abandon a
-			// transfer that may be hours in.
+			// transfer that may be hours in — but a daemon that stays
+			// away is a stall like any other.
 			s.logger.Debug("slskd transfer poll failed", "error", err)
 
+			if time.Since(lastProgress) >= s.stallAfter {
+				s.cancelTransfers(username, live)
+
+				return fmt.Errorf(
+					"%w: slskd has not answered for %s: %w",
+					ErrSlskdTimeout, s.stallAfter, err,
+				)
+			}
+
 			continue
 		}
 
-		var (
+		tally := tallyTransfers(
-			done, failed int
+			transfers, wanted, stale,
-			current      int64
+			time.Since(started) >= s.absentGrace,
 		)
+		live = tally.live
 
-		for _, t := range transfers {
+		if tally.bytes > lastBytes {
-			if !wanted[t.Filename] {
+			lastBytes = tally.bytes
-				continue
+			lastProgress = time.Now()
-			}
-
-			current += t.BytesTransferred
-
-			finished, ok := t.done()
-			if !finished {
-				continue
-			}
-
-			if ok {
-				done++
-			} else {
-				failed++
-			}
 		}
 
 		if onProgress != nil {
 			onProgress(Progress{
-				Current: current,
+				Current: tally.bytes,
 				Total:   c.TotalSize,
 				Phase: fmt.Sprintf(
-					"Transferring from %s (%d/%d)", username, done, len(wanted),
+					"Transferring from %s (%d/%d)",
+					username, tally.done, len(wanted),
 				),
 			})
 		}
 
-		if done+failed < len(wanted) {
+		if tally.done+tally.failed >= len(wanted) {
+			// Some files failing is normal — a peer goes offline
+			// mid-folder.  Let the importer's completeness check decide
+			// whether what arrived is enough, rather than discarding it
+			// here.
+			if tally.done == 0 {
+				return fmt.Errorf(
+					"%w: all %d files failed",
+					ErrSlskdTransferFailed, tally.failed,
+				)
+			}
+
+			return nil
+		}
+
+		if time.Since(lastProgress) < s.stallAfter {
 			continue
 		}
 
-		// Some files failing is normal — a peer goes offline mid-folder.
+		s.cancelTransfers(username, live)
-		// Let the importer's completeness check decide whether what
+
-		// arrived is enough, rather than discarding it here.
+		// A folder that stalls on its last track is the same shape as
-		if done == 0 {
+		// one whose last track failed, and goes forward the same way.
-			return fmt.Errorf(
+		if tally.done > 0 {
-				"%w: all %d files failed", ErrSlskdTransferFailed, failed,
+			s.logger.Info(
+				"slskd transfer stalled; keeping what arrived",
+				"peer", username,
+				"done", tally.done,
+				"wanted", len(wanted),
 			)
+
+			return nil
 		}
 
-		return nil
+		return fmt.Errorf(
+			"%w: %s sent nothing in %s",
+			ErrSlskdTimeout, username, s.stallAfter,
+		)
+	}
+}
+
+// transferTally is one poll's reading of the files a grab asked for.
+type transferTally struct {
+	done, failed int
+	bytes        int64
+
+	// live are the requested transfers slskd is still working on,
+	// which are what has to be cancelled if the grab is abandoned.
+	live []slskdTransfer
+}
+
+// tallyTransfers reads a peer's transfer list against the files a grab
+// asked for.
+//
+// A requested file slskd does not list at all is one it never accepted
+// — refused at enqueue, or dropped — and it will never reach a terminal
+// state to be counted by.  Once absentExpired, such a file counts as
+// failed, or the grab would wait on it until the six-hour ceiling.
+func tallyTransfers(
+	transfers []slskdTransfer,
+	wanted map[string]bool,
+	stale map[string]bool,
+	absentExpired bool,
+) transferTally {
+	seen := make(map[string]slskdTransfer, len(wanted))
+
+	for _, t := range transfers {
+		if !wanted[t.Filename] || stale[t.ID] {
+			continue
+		}
+
+		seen[t.Filename] = t
+	}
+
+	var out transferTally
+
+	for name := range wanted {
+		t, ok := seen[name]
+		if !ok {
+			if absentExpired {
+				out.failed++
+			}
+
+			continue
+		}
+
+		out.bytes += t.BytesTransferred
+
+		finished, succeeded := t.done()
+
+		switch {
+		case !finished:
+			out.live = append(out.live, t)
+		case succeeded:
+			out.done++
+		default:
+			out.failed++
+		}
+	}
+
+	return out
+}
+
+// cancelTransfers asks slskd to cancel and forget transfers this grab
+// is abandoning.  It runs on a context of its own: the usual reason to
+// be here is that the caller's context has just been cancelled, and a
+// cleanup that inherited it would never be sent.
+func (s *slskd) cancelTransfers(username string, live []slskdTransfer) {
+	if len(live) == 0 {
+		return
+	}
+
+	ctx, cancel := context.WithTimeout(
+		context.Background(), slskdCancelTimeout,
+	)
+	defer cancel()
+
+	for _, t := range live {
+		if t.ID == "" {
+			continue
+		}
+
+		endpoint := slskdDownloadsPath(username) + "/" +
+			url.PathEscape(t.ID) + "?remove=true"
+
+		if err := s.client.delete(ctx, endpoint); err != nil {
+			s.logger.Warn(
+				"could not cancel slskd transfer",
+				"peer", username,
+				"file", t.Filename,
+				"error", err,
+			)
+		}
 	}
 }
 
@@ -581,9 +1089,7 @@ func (s *slskd) transfersFor(
 		} `json:"directories"`
 	}
 
-	if err := s.client.get(
+	if err := s.client.get(ctx, slskdDownloadsPath(username), &raw); err != nil {
-		ctx, "/api/v0/transfers/downloads/"+username, &raw,
-	); err != nil {
 		return nil, err
 	}
 
@@ -616,7 +1122,13 @@ func (s *slskd) collect(c Candidate, dst string) (Result, error) {
 			continue
 		}
 
+		// A multi-disc candidate keeps its disc folders in staging.
+		// Flattened, disc 2's "01 Intro.flac" overwrites disc 1's, and
+		// the importer loses the folder it reads the disc number from.
 		target := filepath.Join(dst, base)
+		if _, ok := discFolder(folder); ok {
+			target = filepath.Join(dst, folder, base)
+		}
 
 		if err := movePath(src, target); err != nil {
 			return Result{}, fmt.Errorf("collect %s: %w", base, err)

backend/download/provider_slskd_test.go

@@ -31,11 +31,30 @@ type slskdStub struct {
 	transfers [][]slskdTransfer
 	pollCount int
 
+	// before is what the downloads endpoint reports until something is
+	// enqueued: records slskd already held from earlier attempts.
+	before []slskdTransfer
+
 	// enqueued records what was requested for download.
 	enqueued []map[string]any
+	posted   bool
+
+	// paths records the escaped path of every transfers call, and
+	// cancelled the escaped request URI of every DELETE.
+	paths     []string
+	cancelled []string
 
 	// unauthorized makes every call return 401.
 	unauthorized bool
+
+	// searches records every search request body, and searchGets the
+	// request URI of every search GET.
+	searches   []map[string]any
+	searchGets []string
+
+	// noResponsesEndpoint makes /searches/{id}/responses 404, as an
+	// older daemon would.
+	noResponsesEndpoint bool
 }
 
 func newSlskdStub(t *testing.T) *slskdStub {
@@ -57,6 +76,16 @@ func newSlskdStub(t *testing.T) *slskdStub {
 			return
 		}
 
+		var body map[string]any
+
+		if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+			t.Errorf("decode search body: %v", err)
+		}
+
+		s.mu.Lock()
+		s.searches = append(s.searches, body)
+		s.mu.Unlock()
+
 		w.WriteHeader(http.StatusCreated)
 	})
 
@@ -73,8 +102,26 @@ func newSlskdStub(t *testing.T) *slskdStub {
 
 		s.mu.Lock()
 		responses := s.responses
+		noEndpoint := s.noResponsesEndpoint
+		s.searchGets = append(s.searchGets, r.URL.RequestURI())
 		s.mu.Unlock()
 
+		if strings.HasSuffix(r.URL.Path, "/responses") {
+			if noEndpoint {
+				w.WriteHeader(http.StatusNotFound)
+
+				return
+			}
+
+			writeJSON(t, w, responses)
+
+			return
+		}
+
+		if r.URL.Query().Get("includeResponses") != "true" {
+			responses = nil
+		}
+
 		writeJSON(t, w, slskdSearch{
 			ID:         "search-1",
 			IsComplete: true,
@@ -87,7 +134,12 @@ func newSlskdStub(t *testing.T) *slskdStub {
 			return
 		}
 
-		if r.Method == http.MethodPost {
+		s.mu.Lock()
+		s.paths = append(s.paths, r.URL.EscapedPath())
+		s.mu.Unlock()
+
+		switch r.Method {
+		case http.MethodPost:
 			var body []map[string]any
 
 			if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
@@ -96,15 +148,35 @@ func newSlskdStub(t *testing.T) *slskdStub {
 
 			s.mu.Lock()
 			s.enqueued = body
+			s.posted = true
 			s.mu.Unlock()
 
 			w.WriteHeader(http.StatusCreated)
 
+			return
+		case http.MethodDelete:
+			s.mu.Lock()
+			s.cancelled = append(s.cancelled, r.URL.RequestURI())
+			s.mu.Unlock()
+
+			w.WriteHeader(http.StatusNoContent)
+
 			return
 		}
 
 		s.mu.Lock()
 
+		if !s.posted {
+			before := s.before
+			s.mu.Unlock()
+
+			writeJSON(t, w, map[string]any{
+				"directories": []map[string]any{{"files": before}},
+			})
+
+			return
+		}
+
 		idx := s.pollCount
 		if idx >= len(s.transfers) {
 			idx = len(s.transfers) - 1
@@ -191,6 +263,11 @@ func newStubSlskd(t *testing.T, stub *slskdStub) (*slskd, string) {
 	s.searchWait = 200 * time.Millisecond
 	s.transferPoll = time.Millisecond
 
+	// Long enough that no existing test trips them by accident; the
+	// tests about stalls and absences set their own.
+	s.stallAfter = time.Minute
+	s.absentGrace = time.Minute
+
 	return s, downloads
 }
 
@@ -565,3 +642,293 @@ func TestSlskdRequiresConfiguration(t *testing.T) {
 		})
 	}
 }
+
+// slskdAlbum is a two-file candidate from peer, with the files slskd
+// would have written already in place under downloads.
+func slskdAlbum(t *testing.T, downloads, peer string, arrived ...string) Candidate {
+	t.Helper()
+
+	folder := filepath.Join(downloads, "Album")
+	if err := os.MkdirAll(folder, 0o750); err != nil {
+		t.Fatalf("mkdir: %v", err)
+	}
+
+	for _, name := range arrived {
+		if err := os.WriteFile(
+			filepath.Join(folder, name), []byte("audio"), 0o600,
+		); err != nil {
+			t.Fatalf("write: %v", err)
+		}
+	}
+
+	return Candidate{
+		Files: []CandidateFile{
+			{Path: `\s\Album\01 A.flac`, Size: 500, IsAudio: true},
+			{Path: `\s\Album\02 B.flac`, Size: 500, IsAudio: true},
+		},
+		TotalSize: 1000,
+		Payload:   map[string]string{"username": peer},
+	}
+}
+
+// cancelledURIs returns what the stub was asked to cancel.
+func (s *slskdStub) cancelledURIs() []string {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	return append([]string(nil), s.cancelled...)
+}
+
+// A peer that queues us and never sends a byte is given up on, and the
+// queued transfers are cancelled in slskd rather than left to start
+// hours later for a request nobody is waiting on.
+func TestSlskdGrabGivesUpOnAStalledPeer(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.transfers = [][]slskdTransfer{{
+		{ID: "t1", Filename: `\s\Album\01 A.flac`, State: "Queued, Remotely"},
+		{ID: "t2", Filename: `\s\Album\02 B.flac`, State: "Queued, Remotely"},
+	}}
+
+	s, downloads := newStubSlskd(t, stub)
+	s.stallAfter = 30 * time.Millisecond
+
+	_, err := s.Grab(
+		context.Background(), slskdAlbum(t, downloads, "peer"), t.TempDir(), nil,
+	)
+	if !errors.Is(err, ErrSlskdTimeout) {
+		t.Fatalf("error = %v, want ErrSlskdTimeout", err)
+	}
+
+	got := stub.cancelledURIs()
+	if len(got) != 2 {
+		t.Fatalf("cancelled %v, want both queued transfers", got)
+	}
+
+	for _, uri := range got {
+		if !strings.HasSuffix(uri, "?remove=true") {
+			t.Errorf("cancel %s does not remove the record", uri)
+		}
+	}
+}
+
+// A folder that stalls on its last track goes forward with what
+// arrived, the same as one whose last track failed; the importer's
+// completeness check decides whether that is enough.
+func TestSlskdGrabKeepsWhatArrivedBeforeAStall(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.transfers = [][]slskdTransfer{{
+		{
+			ID: "t1", Filename: `\s\Album\01 A.flac`,
+			State: "Completed, Succeeded", BytesTransferred: 500,
+		},
+		{ID: "t2", Filename: `\s\Album\02 B.flac`, State: "Queued, Remotely"},
+	}}
+
+	s, downloads := newStubSlskd(t, stub)
+	s.stallAfter = 30 * time.Millisecond
+
+	got, err := s.Grab(
+		context.Background(),
+		slskdAlbum(t, downloads, "peer", "01 A.flac"),
+		t.TempDir(), nil,
+	)
+	if err != nil {
+		t.Fatalf("Grab: %v", err)
+	}
+
+	if len(got.Files) != 1 {
+		t.Errorf("collected %d files, want the 1 that arrived", len(got.Files))
+	}
+
+	if cancelled := stub.cancelledURIs(); len(cancelled) != 1 ||
+		!strings.Contains(cancelled[0], "/t2") {
+		t.Errorf("cancelled %v, want only the stalled t2", cancelled)
+	}
+}
+
+// Progress is what holds the stall timer off.  A transfer that keeps
+// moving bytes is never abandoned, however long it takes.
+func TestSlskdGrabWaitsOnATransferThatIsMoving(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+
+	for b := int64(1); b <= 100; b++ {
+		stub.transfers = append(stub.transfers, []slskdTransfer{
+			{ID: "t1", Filename: `\s\Album\01 A.flac`, State: "InProgress", BytesTransferred: b},
+			{ID: "t2", Filename: `\s\Album\02 B.flac`, State: "Queued, Remotely"},
+		})
+	}
+
+	stub.transfers = append(stub.transfers, []slskdTransfer{
+		{
+			ID:               "t1",
+			Filename:         `\s\Album\01 A.flac`,
+			State:            "Completed, Succeeded",
+			BytesTransferred: 500,
+		},
+		{
+			ID:               "t2",
+			Filename:         `\s\Album\02 B.flac`,
+			State:            "Completed, Succeeded",
+			BytesTransferred: 500,
+		},
+	})
+
+	s, downloads := newStubSlskd(t, stub)
+	// A hundred polls take several times the stall window; each one
+	// moves a byte.  The window is kept well above one poll so a
+	// descheduled test runner does not read as a stall.
+	s.transferPoll = 5 * time.Millisecond
+	s.stallAfter = 150 * time.Millisecond
+
+	got, err := s.Grab(
+		context.Background(),
+		slskdAlbum(t, downloads, "peer", "01 A.flac", "02 B.flac"),
+		t.TempDir(), nil,
+	)
+	if err != nil {
+		t.Fatalf("Grab: %v", err)
+	}
+
+	if len(got.Files) != 2 {
+		t.Errorf("collected %d files, want 2", len(got.Files))
+	}
+}
+
+// A file slskd never lists was refused at enqueue and will never reach
+// a terminal state.  It counts as failed once the grace period is up,
+// rather than being waited on until the six-hour ceiling.
+func TestSlskdGrabCountsAnUnlistedFileAsFailed(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.transfers = [][]slskdTransfer{{
+		{
+			ID: "t1", Filename: `\s\Album\01 A.flac`,
+			State: "Completed, Succeeded", BytesTransferred: 500,
+		},
+	}}
+
+	s, downloads := newStubSlskd(t, stub)
+	s.absentGrace = 20 * time.Millisecond
+
+	got, err := s.Grab(
+		context.Background(),
+		slskdAlbum(t, downloads, "peer", "01 A.flac"),
+		t.TempDir(), nil,
+	)
+	if err != nil {
+		t.Fatalf("Grab: %v", err)
+	}
+
+	if len(got.Files) != 1 {
+		t.Errorf("collected %d files, want 1", len(got.Files))
+	}
+}
+
+// A finished record left by an earlier attempt at the same file is not
+// this attempt's answer.  Without the snapshot it would fail the grab on
+// the first poll, before the new transfer had started.
+func TestSlskdGrabIgnoresAnEarlierAttemptsRecord(t *testing.T) {
+	t.Parallel()
+
+	stale := slskdTransfer{
+		ID: "old", Filename: `\s\Album\01 A.flac`, State: "Completed, Errored",
+	}
+
+	stub := newSlskdStub(t)
+	stub.before = []slskdTransfer{stale}
+	stub.transfers = [][]slskdTransfer{
+		{stale},
+		{
+			stale,
+			{
+				ID: "new", Filename: `\s\Album\01 A.flac`,
+				State: "Completed, Succeeded", BytesTransferred: 500,
+			},
+		},
+	}
+
+	s, downloads := newStubSlskd(t, stub)
+
+	c := slskdAlbum(t, downloads, "peer", "01 A.flac")
+	c.Files = c.Files[:1]
+
+	got, err := s.Grab(context.Background(), c, t.TempDir(), nil)
+	if err != nil {
+		t.Fatalf("Grab: %v", err)
+	}
+
+	if len(got.Files) != 1 {
+		t.Errorf("collected %d files, want 1", len(got.Files))
+	}
+}
+
+// Cancelling the download cancels the transfer in slskd too.  The
+// cleanup must not inherit the cancelled context, or it is never sent.
+func TestSlskdGrabCancelsTransfersWhenTheCallerGivesUp(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.transfers = [][]slskdTransfer{{
+		{ID: "t1", Filename: `\s\Album\01 A.flac`, State: "InProgress", BytesTransferred: 10},
+		{ID: "t2", Filename: `\s\Album\02 B.flac`, State: "Queued, Remotely"},
+	}}
+
+	s, downloads := newStubSlskd(t, stub)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)
+	defer cancel()
+
+	_, err := s.Grab(ctx, slskdAlbum(t, downloads, "peer"), t.TempDir(), nil)
+	if !errors.Is(err, ErrSlskdTimeout) {
+		t.Fatalf("error = %v, want ErrSlskdTimeout", err)
+	}
+
+	if got := stub.cancelledURIs(); len(got) != 2 {
+		t.Errorf("cancelled %v, want both live transfers", got)
+	}
+}
+
+// Soulseek usernames carry spaces and punctuation; spliced raw into the
+// path, a name with a slash addresses a different endpoint entirely.
+func TestSlskdEscapesTheUsername(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.transfers = [][]slskdTransfer{{
+		{
+			ID: "t1", Filename: `\s\Album\01 A.flac`,
+			State: "Completed, Succeeded", BytesTransferred: 500,
+		},
+		{
+			ID: "t2", Filename: `\s\Album\02 B.flac`,
+			State: "Completed, Succeeded", BytesTransferred: 500,
+		},
+	}}
+
+	s, downloads := newStubSlskd(t, stub)
+
+	if _, err := s.Grab(
+		context.Background(),
+		slskdAlbum(t, downloads, "dj a/b", "01 A.flac", "02 B.flac"),
+		t.TempDir(), nil,
+	); err != nil {
+		t.Fatalf("Grab: %v", err)
+	}
+
+	stub.mu.Lock()
+	paths := append([]string(nil), stub.paths...)
+	stub.mu.Unlock()
+
+	for _, p := range paths {
+		if p != "/api/v0/transfers/downloads/dj%20a%2Fb" {
+			t.Errorf("transfers call went to %s", p)
+		}
+	}
+}

backend/download/rank.go

@@ -35,6 +35,15 @@ const (
 	weightArtistFit    = 0.12
 )
 
+// Match sub-weights when the candidate's durations are known.  Duration
+// takes its weight from title fit, the signal it corroborates: a title
+// says which song a file claims to be, a length says whether it is that
+// recording — the right edit, the whole file, not the live take.
+const (
+	timedWeightTitleFit    = 0.25
+	timedWeightDurationFit = 0.15
+)
+
 // Quality sub-weights.  Each set sums to 1.0.
 //
 // There are two of them because a stated preference changes what the
@@ -319,13 +328,13 @@ func Score(dl Download, c Candidate, priority int, prefs AutoDownloadPrefs) Cand
 
 	audio := c.AudioFiles()
 
-	matched, titleFit := matchFiles(audio, dl.Expected)
+	a := alignFiles(audio, dl.Expected)
 
 	// Write the alignment back so the picker can show which file maps
 	// to which track.
-	c.Files = mergeMatched(c.Files, matched)
+	c.Files = mergeMatched(c.Files, a.files)
 
-	c.Match = scoreMatch(dl, c, audio, titleFit)
+	c.Match = scoreMatch(dl, c, audio, a)
 	c.Quality = scoreQuality(
 		c, audio, priority, prefs, dl.runtimeMillis(),
 	)
@@ -340,14 +349,21 @@ func scoreMatch(
 	dl Download,
 	c Candidate,
 	audio []CandidateFile,
-	titleFit float64,
+	a alignment,
 ) MatchScore {
 	m := MatchScore{
-		Anchored: dl.Anchored(),
+		Anchored:    dl.Anchored(),
-		TitleFit: titleFit,
+		TitleFit:    a.titleFit,
+		DurationFit: a.durationFit,
+
+		// Durations count once at least half the aligned pairs state
+		// one; a single timed pair would be a coin toss carrying 15%.
+		DurationKnown: a.timedPairs > 0 && a.timedPairs*2 >= a.aligned,
 	}
 
-	m.Completeness = completeness(len(audio), len(dl.Expected))
+	m.Completeness = completeness(
+		alignedCount(c.Files), len(audio), len(dl.Expected),
+	)
 
 	// The candidate's own title, and the folder its files sit in, are
 	// two independent guesses at the album name.  Take the better one:
@@ -367,9 +383,16 @@ func scoreMatch(
 	// With no expected tracklist there is no title signal at all, so
 	// redistribute its weight onto the album/artist evidence rather
 	// than scoring every free-text result as half-wrong.
-	if len(dl.Expected) == 0 {
+	switch {
+	case len(dl.Expected) == 0:
 		m.Overall = 0.55*m.AlbumFit + 0.45*m.ArtistFit
-	} else {
+	case m.DurationKnown:
+		m.Overall = timedWeightTitleFit*m.TitleFit +
+			timedWeightDurationFit*m.DurationFit +
+			weightCompleteness*m.Completeness +
+			weightAlbumFit*m.AlbumFit +
+			weightArtistFit*m.ArtistFit
+	default:
 		m.Overall = weightTitleFit*m.TitleFit +
 			weightCompleteness*m.Completeness +
 			weightAlbumFit*m.AlbumFit +
@@ -415,30 +438,54 @@ func artistFit(want string, c Candidate) float64 {
 	return best
 }
 
-// completeness scores audio file count against the expected track
+// completeness scores how much of the expected tracklist a candidate
-// count.  Extra files are penalized far more gently than missing ones:
+// covers.  Extra files are penalized far more gently than missing ones:
 // a folder with bonus tracks or a stray intro is still the album, while
 // a folder missing half the tracks is not.
-func completeness(got, want int) float64 {
+//
+// **Coverage is counted in aligned tracks, not in files.**  It used to
+// be the audio file count, so any ten files scored full marks against
+// a ten-track album whether or not they were its tracks — and since
+// title fit is the mean over the files that *did* align, a folder where
+// three titles matched read as a near-perfect candidate on both counts.
+// `aligned` is how many files matchFiles assigned to an expected track;
+// `audio` still sets the penalty for extras, because a folder of thirty
+// files holding the ten wanted is a worse copy than one holding ten.
+func completeness(aligned, audio, want int) float64 {
 	if want == 0 {
-		if got > 0 {
+		if audio > 0 {
 			return 0.5
 		}
 
 		return 0
 	}
 
-	if got == 0 {
+	if aligned == 0 {
 		return 0
 	}
 
-	if got >= want {
+	cover := float64(min(aligned, want)) / float64(want)
-		extra := float64(got-want) / float64(want)
 
-		return math.Max(0.75, 1.0-0.25*extra)
+	if audio > want {
+		extra := float64(audio-want) / float64(want)
+		cover *= math.Max(0.75, 1.0-0.25*extra)
 	}
 
-	return float64(got) / float64(want)
+	return cover
+}
+
+// alignedCount is how many audio files were assigned to an expected
+// track.
+func alignedCount(files []CandidateFile) int {
+	n := 0
+
+	for _, f := range files {
+		if f.IsAudio && f.MatchedTo != 0 {
+			n++
+		}
+	}
+
+	return n
 }
 
 // scoreQuality answers whether this is a good copy.
@@ -735,6 +782,45 @@ func AutoPickVeto(
 	return ""
 }
 
+// autoAcceptable reports whether auto-pick may take this one candidate
+// without asking: the request is anchored to a tracklist, and the
+// candidate is inside the user's guardrails and clears the match and
+// quality bars.  It is AutoPickVeto's test applied to a single
+// candidate, which is what falling back to a second choice needs.
+func autoAcceptable(dl Download, c Candidate, prefs AutoDownloadPrefs) bool {
+	return dl.Anchored() &&
+		len(dl.Expected) > 0 &&
+		prefs.eligible(c, dl.runtimeMillis()) &&
+		c.Match.Overall >= minMatch &&
+		c.Quality.Overall >= minQuality
+}
+
+// autoPick returns the candidate auto-pick takes: the best-ranked one
+// it may take at all.
+//
+// That is not `ranked[0]`.  AutoPickVeto judges the best candidate
+// *inside* the guardrails, so when the overall best is outside them —
+// over the size ceiling, say — the veto passes on the strength of the
+// second, and grabbing the first would download exactly the copy the
+// user said not to take unattended.
+func autoPick(
+	dl Download,
+	ranked []Candidate,
+	prefs AutoDownloadPrefs,
+) (Candidate, bool) {
+	if AutoPickVeto(dl, ranked, prefs) != "" {
+		return Candidate{}, false
+	}
+
+	for _, c := range ranked {
+		if autoAcceptable(dl, c, prefs) {
+			return c, true
+		}
+	}
+
+	return Candidate{}, false
+}
+
 // mergeMatched copies MatchedTo assignments from the audio-only slice
 // back onto the full file list.
 func mergeMatched(all, matched []CandidateFile) []CandidateFile {

backend/download/rank_test.go

@@ -282,28 +282,32 @@ func TestCompleteness(t *testing.T) {
 
 	tests := []struct {
 		name     string
-		got      int
+		aligned  int
+		audio    int
 		want     int
 		minScore float64
 		maxScore float64
 	}{
-		{"exact", 10, 10, 1.0, 1.0},
+		{"exact", 10, 10, 10, 1.0, 1.0},
-		{"half missing", 5, 10, 0.49, 0.51},
+		{"half missing", 5, 5, 10, 0.49, 0.51},
-		{"one bonus track", 11, 10, 0.95, 1.0},
+		{"one bonus track", 10, 11, 10, 0.95, 1.0},
-		{"double", 20, 10, 0.74, 0.76},
+		{"double", 10, 20, 10, 0.74, 0.76},
-		{"nothing", 0, 10, 0, 0},
+		{"nothing", 0, 0, 10, 0, 0},
-		{"no expectation", 5, 0, 0.5, 0.5},
+		{"no expectation", 0, 5, 0, 0.5, 0.5},
+		// Ten files are not ten tracks: three that align are three.
+		{"right count, wrong tracks", 3, 10, 10, 0.29, 0.31},
+		{"files that align to nothing", 0, 10, 10, 0, 0},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 
-			got := completeness(tt.got, tt.want)
+			got := completeness(tt.aligned, tt.audio, tt.want)
 			if got < tt.minScore || got > tt.maxScore {
 				t.Errorf(
-					"completeness(%d, %d) = %f, want in [%f, %f]",
+					"completeness(%d, %d, %d) = %f, want in [%f, %f]",
-					tt.got, tt.want, got, tt.minScore, tt.maxScore,
+					tt.aligned, tt.audio, tt.want, got, tt.minScore, tt.maxScore,
 				)
 			}
 		})

backend/download/search_recall_test.go

@@ -0,0 +1,238 @@
+package download
+
+import (
+	"context"
+	"strings"
+	"testing"
+)
+
+// What Soulseek is asked, how, and what is kept from the answer (#271).
+
+func TestSlskdQueries(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name string
+		dl   Download
+		want []string
+	}{
+		{
+			name: "a plain request is searched once",
+			dl:   Download{Artist: "Radiohead", Album: "OK Computer"},
+			want: []string{"Radiohead OK Computer"},
+		},
+		{
+			name: "an edition qualifier gets a second query without it",
+			dl:   Download{Artist: "Radiohead", Album: "OK Computer (Collector's Edition)"},
+			want: []string{
+				"Radiohead OK Computer (Collector's Edition)",
+				"Radiohead OK Computer",
+			},
+		},
+		{
+			name: "a trailing remaster note",
+			dl:   Download{Artist: "Pink Floyd", Album: "Animals - 2018 Remaster"},
+			want: []string{
+				"Pink Floyd Animals - 2018 Remaster",
+				"Pink Floyd Animals",
+			},
+		},
+		{
+			name: "a leading dash would be an exclusion",
+			dl:   Download{Artist: "Mocky", Album: "-ism"},
+			want: []string{"Mocky -ism", "Mocky ism"},
+		},
+		{
+			name: "a compilation is not searched by its placeholder artist",
+			dl:   Download{Artist: "Various Artists", Album: "Pulp Fiction"},
+			want: []string{"Various Artists Pulp Fiction", "Pulp Fiction"},
+		},
+		{
+			name: "what the user typed is searched as written",
+			dl:   Download{Query: "ok computer (deluxe)", Album: "OK Computer (Deluxe)"},
+			want: []string{"ok computer (deluxe)"},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := slskdQueries(tc.dl)
+			if strings.Join(got, "|") != strings.Join(tc.want, "|") {
+				t.Errorf("slskdQueries = %q, want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+// Both queries run, the options are stated rather than left to the
+// daemon's defaults, and a folder both queries found is one candidate.
+func TestSlskdSearchRunsBothQueriesAndMerges(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.responses = []slskdResponse{{
+		Username: "peer",
+		Files: []slskdFile{
+			{Filename: `\m\Radiohead - OK Computer\01 Airbag.flac`, Size: 1, Length: 284},
+			{Filename: `\m\Radiohead - OK Computer\02 Paranoid Android.flac`, Size: 1, Length: 383},
+		},
+	}}
+
+	s, _ := newStubSlskd(t, stub)
+
+	got, err := s.Search(context.Background(), Download{
+		ReleaseMBID: "rel", Artist: "Radiohead", Album: "OK Computer (Deluxe Edition)",
+	})
+	if err != nil {
+		t.Fatalf("Search: %v", err)
+	}
+
+	if len(got) != 1 {
+		t.Fatalf("got %d candidates, want the one folder once", len(got))
+	}
+
+	if got[0].Files[0].LengthMillis != 284_000 {
+		t.Errorf("length = %d ms, want 284000 from slskd's seconds", got[0].Files[0].LengthMillis)
+	}
+
+	stub.mu.Lock()
+	searches := append([]map[string]any(nil), stub.searches...)
+	gets := append([]string(nil), stub.searchGets...)
+	stub.mu.Unlock()
+
+	if len(searches) != 2 {
+		t.Fatalf("ran %d searches, want 2", len(searches))
+	}
+
+	for _, body := range searches {
+		for _, key := range []string{
+			"searchTimeout", "responseLimit", "fileLimit",
+			"minimumResponseFileCount", "maximumPeerQueueLength",
+		} {
+			if _, ok := body[key]; !ok {
+				t.Errorf("search %q does not state %s", body["searchText"], key)
+			}
+		}
+	}
+
+	// The responses are fetched once at the end, not with every poll.
+	for _, uri := range gets {
+		if strings.Contains(uri, "includeResponses") {
+			t.Errorf("poll %s asked for every response", uri)
+		}
+	}
+}
+
+// A daemon without the responses endpoint still returns results.
+func TestSlskdSearchFallsBackForAnOlderDaemon(t *testing.T) {
+	t.Parallel()
+
+	stub := newSlskdStub(t)
+	stub.noResponsesEndpoint = true
+	stub.responses = []slskdResponse{{
+		Username: "peer",
+		Files: []slskdFile{
+			{Filename: `\m\Album\01 A.flac`, Size: 1},
+			{Filename: `\m\Album\02 B.flac`, Size: 1},
+		},
+	}}
+
+	s, _ := newStubSlskd(t, stub)
+
+	got, err := s.Search(context.Background(), Download{Query: "album"})
+	if err != nil {
+		t.Fatalf("Search: %v", err)
+	}
+
+	if len(got) != 1 {
+		t.Errorf("got %d candidates, want 1 through the fallback", len(got))
+	}
+}
+
+func TestDurationAgreement(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		got, want int64
+		score     float64
+	}{
+		{300_000, 300_000, 1},
+		{301_500, 300_000, 1}, // a second of silence
+		{300_000, 316_500, 0.5},
+		{300_000, 345_000, 0}, // a different edit
+	}
+
+	for _, tc := range cases {
+		if got := durationAgreement(tc.got, tc.want); got < tc.score-0.01 || got > tc.score+0.01 {
+			t.Errorf("durationAgreement(%d, %d) = %f, want %f", tc.got, tc.want, got, tc.score)
+		}
+	}
+}
+
+// Two folders with the same track names are told apart by their
+// lengths: one is the album, the other a live record of the same songs.
+func TestDurationsSeparateTheRightRecording(t *testing.T) {
+	t.Parallel()
+
+	dl := okComputer()
+
+	timed := func(id string, lengths ...int64) Candidate {
+		c := candidateFor(id, allTitles(), ".flac", 30_000_000)
+		for i := range c.Files {
+			c.Files[i].LengthMillis = lengths[i]
+		}
+
+		return c
+	}
+
+	studio := timed("studio", trackMillis, trackMillis+1_000, trackMillis, trackMillis-500)
+	live := timed(
+		"live",
+		trackMillis+60_000,
+		trackMillis+75_000,
+		trackMillis+50_000,
+		trackMillis+90_000,
+	)
+
+	ranked := Rank(dl, []Candidate{live, studio}, nil, AutoDownloadPrefs{})
+
+	if ranked[0].ID != "studio" {
+		t.Fatalf("winner = %s, want the recording whose lengths match", ranked[0].ID)
+	}
+
+	if !ranked[0].Match.DurationKnown || ranked[0].Match.DurationFit < 0.99 {
+		t.Errorf(
+			"studio duration fit = %f known=%v",
+			ranked[0].Match.DurationFit,
+			ranked[0].Match.DurationKnown,
+		)
+	}
+
+	if ranked[1].Match.DurationFit != 0 {
+		t.Errorf("live duration fit = %f, want 0", ranked[1].Match.DurationFit)
+	}
+}
+
+// Without lengths the score is exactly what it was before durations
+// were read, so a provider that reports none is not penalised.
+func TestUnknownDurationsLeaveTheScoreAlone(t *testing.T) {
+	t.Parallel()
+
+	dl := okComputer()
+	c := Score(dl, candidateFor("c", allTitles(), ".flac", 30_000_000), 50, AutoDownloadPrefs{})
+
+	if c.Match.DurationKnown {
+		t.Fatal("no file states a length, yet durations are known")
+	}
+
+	want := weightTitleFit*c.Match.TitleFit +
+		weightCompleteness*c.Match.Completeness +
+		weightAlbumFit*c.Match.AlbumFit +
+		weightArtistFit*c.Match.ArtistFit
+
+	if c.Match.Overall != want {
+		t.Errorf("match = %f, want the untimed formula's %f", c.Match.Overall, want)
+	}
+}

backend/download/types.go

@@ -232,12 +232,17 @@ type Candidate struct {
 // results give paths and sizes but no tags, so Format and duration are
 // inferred from the path and size where possible.
 type CandidateFile struct {
-	Path      string `json:"path"`
+	Path    string `json:"path"`
-	Size      int64  `json:"size"`
+	Size    int64  `json:"size"`
-	Format    Format `json:"format"`
+	Format  Format `json:"format"`
-	Bitrate   int    `json:"bitrate,omitempty"` // kbps, 0 when unknown
+	Bitrate int    `json:"bitrate,omitempty"` // kbps, 0 when unknown
-	IsAudio   bool   `json:"isAudio"`
+	IsAudio bool   `json:"isAudio"`
-	MatchedTo int    `json:"matchedTo,omitempty"` // expected track position
+
+	// LengthMillis is the file's duration as the source reports it, or
+	// 0 when it does not.  Soulseek reports it for most audio files.
+	LengthMillis int64 `json:"lengthMillis,omitempty"`
+
+	MatchedTo int `json:"matchedTo,omitempty"` // expected track position
 }
 
 // Format is a normalized audio container/codec name.
@@ -286,7 +291,14 @@ type MatchScore struct {
 	TitleFit     float64 `json:"titleFit"`     // filenames vs expected titles
 	ArtistFit    float64 `json:"artistFit"`    // path/origin vs expected artist
 	AlbumFit     float64 `json:"albumFit"`     // folder name vs album title
-	Completeness float64 `json:"completeness"` // audio files vs expected count
+	Completeness float64 `json:"completeness"` // aligned tracks vs expected count
+
+	// DurationFit is how well the aligned files' lengths agree with the
+	// expected tracks', and DurationKnown whether enough of them stated
+	// a length for that to count.  When it does not, the score is the
+	// four text signals alone, exactly as before durations were read.
+	DurationFit   float64 `json:"durationFit"`
+	DurationKnown bool    `json:"durationKnown"`
 
 	// Anchored records whether an MBID drove this score.  Unanchored
 	// matches are capped, because there is nothing to be right about.

backend/explore/artifactimport.go

@@ -1,8 +1,10 @@
 package explore
 
 import (
+	"bytes"
 	"context"
 	"database/sql"
+	"database/sql/driver"
 	"errors"
 	"fmt"
 	"os"
@@ -283,6 +285,25 @@ func (si *SearchIndex) importCoreArtifact(ctx context.Context, path string) erro
 	}
 
 	merged, mergeErr := si.mergeArtifactRows(ctx, info.rows)
+
+	// Every row the artifact declares has to land.  The walk partitions
+	// the artifact's key space, so a total short of info.rows does not
+	// mean the artifact was smaller than it said -- it means a predicate
+	// filtered rows out, and the catalog is quietly partial.  Equality
+	// rather than a lower bound because RowsAffected counts an upsert
+	// that changes nothing, and a row already merged locally is counted
+	// again here.
+	//
+	// One reachable case, so this is not merely a tripwire: a row whose
+	// mbid is empty is excluded by `mbid > ?` in both encodings, and an
+	// artifact carrying one would otherwise import as complete.
+	if mergeErr == nil && merged != info.rows {
+		mergeErr = fmt.Errorf(
+			"%w: merged %d of %d rows — a row the artifact holds was not selected",
+			ErrArtifactUnusable, merged, info.rows,
+		)
+	}
+
 	if mergeErr == nil {
 		si.mergeArtifactCredits(ctx)
 	}
@@ -348,8 +369,12 @@ func (si *SearchIndex) analyzeIndex() {
 // is an index range scan and a cancelled import leaves committed work
 // behind rather than rolling it all back.
 func (si *SearchIndex) mergeArtifactRows(ctx context.Context, total int) (int, error) {
+	// Asked once, because it is a property of the file and it decides
+	// how the walk's own comparisons are typed.  See artifactKey.
+	storesText := si.artifactStoresText()
+
 	selectColumns := artifactSelectColumns(
-		si.artifactStoresText(), si.artifactHasTotals(),
+		storesText, si.artifactHasTotals(),
 	)
 
 	insertSQL := `
@@ -367,7 +392,7 @@ func (si *SearchIndex) mergeArtifactRows(ctx context.Context, total int) (int, e
 		WHERE mbid > ? AND mbid <= ?` + upsertIndexConflictSQL
 
 	var (
-		cursor string
+		cursor artifactKey
 		merged int
 	)
 
@@ -376,17 +401,30 @@ func (si *SearchIndex) mergeArtifactRows(ctx context.Context, total int) (int, e
 			return merged, err
 		}
 
-		upper, hasUpper, err := si.artifactBatchBound(cursor)
+		upper, hasUpper, err := si.artifactBatchBound(storesText, cursor)
 		if err != nil {
 			return merged, err
 		}
 
+		if hasUpper && bytes.Compare(upper, cursor) <= 0 {
+			// The predicate matched the cursor itself, so the walk can
+			// never advance.  SQLite says nothing when a comparison is
+			// made between types it will not coerce - the query simply
+			// answers wrongly - so a mismatch here would otherwise spin
+			// forever behind an unmoving progress bar.  Fail instead.
+			return merged, fmt.Errorf(
+				"%w: artifact walk did not advance past %x",
+				ErrArtifactUnusable, []byte(cursor),
+			)
+		}
+
 		var res sql.Result
 
 		if hasUpper {
-			res, err = si.db.ExecContext(insertRangeSQL, cursor, upper)
+			res, err = si.db.ExecContext(insertRangeSQL,
+				cursor.bind(storesText), upper.bind(storesText))
 		} else {
-			res, err = si.db.ExecContext(insertSQL, cursor)
+			res, err = si.db.ExecContext(insertSQL, cursor.bind(storesText))
 		}
 
 		if err != nil {
@@ -413,26 +451,65 @@ func (si *SearchIndex) mergeArtifactRows(ctx context.Context, total int) (int, e
 	}
 }
 
+// artifactKey is one MBID as the attached artifact stores it: 16 raw
+// bytes in a compact artifact, the dashed 36-character form in one
+// published before that storage change.
+//
+// It is a type with a bind method rather than a string because the
+// comparison it feeds is typed, and the wrong type is silent.  SQLite
+// does not coerce between TEXT and BLOB and orders every blob after
+// every text value, so a cursor bound as text against a byte column
+// makes `mbid > ?` true of the whole table - the walk rediscovers the
+// same batch bound forever, and `mbid <= ?` false of the whole table,
+// so no batch merges at all.  Nothing errors; the import simply never
+// finishes.  bind is the one place that knows which form the column is
+// in, decided by artifactStoresText, which asks the artifact rather than
+// trusting a version number.
+type artifactKey []byte
+
+// bind renders the key as a statement argument in the artifact's own
+// encoding.
+func (k artifactKey) bind(storesText bool) driver.Value {
+	if storesText {
+		return string(k)
+	}
+
+	// Never nil.  database/sql converts a nil []byte to SQL NULL, and
+	// `mbid > NULL` is NULL for every row - so an unset cursor would
+	// agree with nothing and import nothing, which is the same silently
+	// empty merge this type exists to prevent, one type over.
+	if k == nil {
+		return []byte{}
+	}
+
+	return []byte(k)
+}
+
 // artifactBatchBound returns the MBID that ends the next batch, and
 // whether one exists — no bound means the remainder is the last batch.
-func (si *SearchIndex) artifactBatchBound(cursor string) (string, bool, error) {
+//
-	var bound string
+// The bound is read out of the artifact and handed back as an
+// artifactKey, because it becomes the next comparison the walk makes.
+func (si *SearchIndex) artifactBatchBound(
+	storesText bool, cursor artifactKey,
+) (artifactKey, bool, error) {
+	var bound []byte
 
 	err := si.db.QueryRowWriter(
 		`SELECT mbid FROM core.explore_index
 		 WHERE mbid > ? ORDER BY mbid LIMIT 1 OFFSET ?`,
-		cursor, artifactMergeBatch-1,
+		cursor.bind(storesText), artifactMergeBatch-1,
 	).Scan(&bound)
 
 	if errors.Is(err, sql.ErrNoRows) {
-		return "", false, nil
+		return nil, false, nil
 	}
 
 	if err != nil {
-		return "", false, fmt.Errorf("%w: batch bound: %w", ErrArtifactUnusable, err)
+		return nil, false, fmt.Errorf("%w: batch bound: %w", ErrArtifactUnusable, err)
 	}
 
-	return bound, true, nil
+	return artifactKey(bound), true, nil
 }
 
 // stampArtifactMeta records what the merge established: the catalog half

backend/explore/artifactimport_test.go

@@ -1,6 +1,7 @@
 package explore
 
 import (
+	"bytes"
 	"context"
 	"database/sql"
 	"encoding/hex"
@@ -71,13 +72,7 @@ func writeTestArtifact(
 		}
 	}
 
-	for k, v := range meta {
+	stampArtifactMeta(t, db, meta)
-		if _, err := db.Exec(
-			`INSERT INTO artifact_meta (key, value) VALUES (?, ?)`, k, v,
-		); err != nil {
-			t.Fatalf("stamp artifact meta: %v", err)
-		}
-	}
 
 	for _, r := range rows {
 		if _, err := db.Exec(`
@@ -93,6 +88,101 @@ func writeTestArtifact(
 	return path
 }
 
+// compactArtifactSchema is the artifact cmd/indexexport publishes: the
+// catalog's ids as 16 raw bytes, its entity types as codes, and the
+// per-release-group total_tracks the exporter added after the first
+// artifact was shipped.
+//
+// It matters that a fixture carries this encoding and not the older
+// text one, because SQLite does not coerce between TEXT and BLOB and
+// every comparison the importer makes against an mbid is therefore
+// encoding-sensitive.  writeTestArtifact above is the *other* fixture:
+// it still writes the text form, which is what the first published
+// artifact carries and what the importer must keep reading.
+var compactArtifactSchema = []string{
+	`CREATE TABLE explore_index (
+		entity_type      INTEGER NOT NULL,
+		mbid             BLOB NOT NULL,
+		title            TEXT NOT NULL,
+		artist_name      TEXT NOT NULL,
+		artist_mbid      BLOB NOT NULL,
+		aliases          TEXT NOT NULL DEFAULT '',
+		popularity       INTEGER NOT NULL DEFAULT 0,
+		listener_count   INTEGER NOT NULL DEFAULT 0,
+		duration         INTEGER NOT NULL DEFAULT 0,
+		caa_release_mbid BLOB NOT NULL DEFAULT x'',
+		release_name     TEXT NOT NULL DEFAULT '',
+		primary_type     TEXT NOT NULL DEFAULT '',
+		secondary_types  TEXT NOT NULL DEFAULT '',
+		release_date     TEXT NOT NULL DEFAULT '',
+		total_tracks     INTEGER NOT NULL DEFAULT 0,
+		artist_type      TEXT NOT NULL DEFAULT '',
+		country          TEXT NOT NULL DEFAULT '',
+		disambiguation   TEXT NOT NULL DEFAULT '',
+		sort_name        TEXT NOT NULL DEFAULT '',
+		discog_fetched   INTEGER NOT NULL DEFAULT 0,
+		PRIMARY KEY (mbid)
+	) WITHOUT ROWID`,
+	`CREATE TABLE artifact_meta (
+		key   TEXT PRIMARY KEY,
+		value TEXT NOT NULL
+	)`,
+}
+
+// writeCompactTestArtifact builds the artifact the exporter publishes
+// today, in its own encoding, so the importer is exercised against what
+// a client actually downloads rather than against what it was written
+// for.
+func writeCompactTestArtifact(
+	t *testing.T, meta map[string]string, rows []artifactRow,
+) string {
+	t.Helper()
+
+	path := filepath.Join(t.TempDir(), "core-index.db")
+
+	db, err := sql.Open("sqlite", "file:"+path)
+	if err != nil {
+		t.Fatalf("open artifact: %v", err)
+	}
+
+	defer func() { _ = db.Close() }()
+
+	for _, stmt := range compactArtifactSchema {
+		if _, err := db.Exec(stmt); err != nil {
+			t.Fatalf("create artifact schema: %v", err)
+		}
+	}
+
+	stampArtifactMeta(t, db, meta)
+
+	for _, r := range rows {
+		if _, err := db.Exec(`
+			INSERT INTO explore_index
+				(entity_type, mbid, title, artist_name, artist_mbid, popularity)
+			VALUES (?, ?, ?, ?, ?, ?)`,
+			entityCode(r.entityType), mbidBytes(r.mbid), r.title,
+			r.artistName, mbidBytes(r.artistMBID), r.popularity,
+		); err != nil {
+			t.Fatalf("insert artifact row: %v", err)
+		}
+	}
+
+	return path
+}
+
+// stampArtifactMeta writes the artifact_meta rows a fixture declares.
+func stampArtifactMeta(t *testing.T, db *sql.DB, meta map[string]string) {
+	t.Helper()
+
+	for k, v := range meta {
+		if _, err := db.Exec(
+			`INSERT INTO artifact_meta (key, value) VALUES (?, ?)`, k, v,
+		); err != nil {
+			t.Fatalf("stamp artifact meta: %v", err)
+		}
+	}
+}
+
 // validMeta is the artifact_meta a well-formed artifact carries.
 func validMeta() map[string]string {
 	return map[string]string{
@@ -270,6 +360,71 @@ func TestImportCoreArtifactBatchWalkCoversAllRows(t *testing.T) {
 	}
 }
 
+// TestImportCoreArtifactBatchWalkCoversAllRowsCompact is the batch walk
+// on the encoding the exporter actually publishes.
+//
+// The walk positions itself by comparing the artifact's own mbid column
+// against the last id it reached, and that column holds 16 raw bytes.
+// SQLite does not coerce between TEXT and BLOB, and a blob sorts after
+// every text value, so a cursor bound as text is a predicate that either
+// matches every row or none: `mbid > ?` with an empty text key is true
+// of the whole table, so
+// the 100th row is always the 100th row and the bound never advances,
+// while `mbid <= <text>` is false of the whole table, so no batch ever
+// merges.  The result is not a wrong import but an unbounded loop that
+// merges nothing and never fails.
+//
+// Both encodings are covered on purpose.  The walk was only ever tested
+// against the text fixture above, which is why it shipped broken on the
+// one the clients download.
+func TestImportCoreArtifactBatchWalkCoversAllRowsCompact(t *testing.T) {
+	db := database.NewTestDB(t)
+	si := NewSearchIndex(db, nil, nil, testLogger())
+
+	original := artifactMergeBatch
+	artifactMergeBatch = 100
+
+	t.Cleanup(func() { artifactMergeBatch = original })
+
+	const total = 337
+
+	rows := make([]artifactRow, 0, total)
+	for i := range total {
+		rows = append(rows, artifactRow{
+			entityType: EntityRecording,
+			mbid:       syntheticMBID(i),
+			title:      "Song",
+			artistName: "Artist",
+			artistMBID: artA,
+			popularity: i,
+		})
+	}
+
+	path := writeCompactTestArtifact(t, validMeta(), rows)
+
+	if err := si.importCoreArtifact(context.Background(), path); err != nil {
+		t.Fatalf("importCoreArtifact: %v", err)
+	}
+
+	var got, top int
+
+	if err := db.QueryRowWriter(
+		"SELECT COUNT(*), MAX(popularity) FROM explore_index",
+	).Scan(&got, &top); err != nil {
+		t.Fatalf("count rows: %v", err)
+	}
+
+	if got != total {
+		t.Errorf("merged %d rows, want %d", got, total)
+	}
+
+	// A count alone would pass if the walk re-merged the same first
+	// batch forever, so the far end of the artifact is checked too.
+	if top != total-1 {
+		t.Errorf("highest popularity = %d, want %d", top, total-1)
+	}
+}
+
 func TestImportCoreArtifactRejectsBadArtifacts(t *testing.T) {
 	tests := []struct {
 		name string
@@ -454,61 +609,9 @@ func TestArtifactColumnsMatchExporter(t *testing.T) {
 // the importer decides by asking the artifact, not by trusting a
 // version number, and both must land identically.
 func TestImportCoreArtifactAcceptsBothEncodings(t *testing.T) {
-	compact := filepath.Join(t.TempDir(), "core-index.db")
+	compact := writeCompactTestArtifact(t, validMeta(), []artifactRow{
-
+		{EntityArtist, artA, "Artist A", "Artist A", artA, 5000},
-	db, err := sql.Open("sqlite", "file:"+compact)
+	})
-	if err != nil {
-		t.Fatalf("open artifact: %v", err)
-	}
-
-	if _, err := db.Exec(`CREATE TABLE explore_index (
-		entity_type      INTEGER NOT NULL,
-		mbid             BLOB NOT NULL,
-		title            TEXT NOT NULL,
-		artist_name      TEXT NOT NULL,
-		artist_mbid      BLOB NOT NULL,
-		aliases          TEXT NOT NULL DEFAULT '',
-		popularity       INTEGER NOT NULL DEFAULT 0,
-		listener_count   INTEGER NOT NULL DEFAULT 0,
-		duration         INTEGER NOT NULL DEFAULT 0,
-		caa_release_mbid BLOB NOT NULL DEFAULT x'',
-		release_name     TEXT NOT NULL DEFAULT '',
-		primary_type     TEXT NOT NULL DEFAULT '',
-		secondary_types  TEXT NOT NULL DEFAULT '',
-		release_date     TEXT NOT NULL DEFAULT '',
-		artist_type      TEXT NOT NULL DEFAULT '',
-		country          TEXT NOT NULL DEFAULT '',
-		disambiguation   TEXT NOT NULL DEFAULT '',
-		sort_name        TEXT NOT NULL DEFAULT '',
-		discog_fetched   INTEGER NOT NULL DEFAULT 0,
-		PRIMARY KEY (mbid)
-	)`); err != nil {
-		t.Fatalf("create artifact table: %v", err)
-	}
-
-	if _, err := db.Exec(
-		`CREATE TABLE artifact_meta (key TEXT PRIMARY KEY, value TEXT NOT NULL)`,
-	); err != nil {
-		t.Fatalf("create artifact meta: %v", err)
-	}
-
-	for k, v := range validMeta() {
-		if _, err := db.Exec(
-			"INSERT INTO artifact_meta (key, value) VALUES (?, ?)", k, v,
-		); err != nil {
-			t.Fatalf("write artifact meta: %v", err)
-		}
-	}
-
-	if _, err := db.Exec(`
-		INSERT INTO explore_index (entity_type, mbid, title, artist_name, artist_mbid, popularity)
-		VALUES (1, ?, 'Artist A', 'Artist A', ?, 5000)`,
-		mbidBytes(artA), mbidBytes(artA),
-	); err != nil {
-		t.Fatalf("write artifact row: %v", err)
-	}
-
-	_ = db.Close()
 
 	live := database.NewTestDB(t)
 	si := NewSearchIndex(live, nil, nil, testLogger())
@@ -748,3 +851,88 @@ func TestImportCoreArtifactWithoutCredits(t *testing.T) {
 		t.Errorf("credit refs = %d, want 0", refs)
 	}
 }
+
+// TestImportCoreArtifactRefusesAMergeThatLosesRows is the count guard's
+// positive case.
+//
+// The walk's predicates partition the artifact's key space, so a merge
+// that lands fewer rows than the artifact declares means a predicate
+// dropped some — and the failure is a catalog that looks populated and
+// is missing things nobody can name.  An empty mbid is the reachable
+// way to get there: `mbid > ?` is false of it in both encodings, so it
+// is never selected, and nothing else in the import would notice.
+func TestImportCoreArtifactRefusesAMergeThatLosesRows(t *testing.T) {
+	db := database.NewTestDB(t)
+	si := NewSearchIndex(db, nil, nil, testLogger())
+
+	path := writeCompactTestArtifact(t, validMeta(), []artifactRow{
+		{EntityArtist, artA, "Artist A", "Artist A", artA, 5000},
+		{EntityArtist, "", "Nameless", "Artist A", artA, 4000},
+	})
+
+	err := si.importCoreArtifact(context.Background(), path)
+	if err == nil {
+		t.Fatal("a merge that lost a row was reported as a complete import")
+	}
+
+	if !strings.Contains(err.Error(), "merged 1 of 2 rows") {
+		t.Errorf("error = %v, want it to name the shortfall", err)
+	}
+
+	// And the same rule as every other rejection: a failed merge must not
+	// leave the index claiming it has a catalog, or the real build would
+	// never run again.
+	if si.hasMeta(dumpImportDoneKey) {
+		t.Error("a failed import still stamped dump_import_done")
+	}
+}
+
+// TestArtifactKeyBindsInTheArtifactsOwnEncoding pins the one place the
+// batch walk's comparison type is decided.
+//
+// Every wrong answer is silent, which is why it is worth pinning all
+// four.  SQLite does not coerce TEXT to BLOB and orders every blob after
+// every text value, so a text key against a byte column makes
+// `mbid > ?` true of the whole artifact - the cursor never advances and
+// the walk spins forever without merging a row - while a byte key
+// against a text column makes it false of the whole artifact, so every
+// batch merges nothing and the import "succeeds" empty.  An unset cursor
+// is the same fault once more: database/sql converts a nil []byte to
+// SQL NULL, and `mbid > NULL` matches no row at all.
+func TestArtifactKeyBindsInTheArtifactsOwnEncoding(t *testing.T) {
+	raw := mbidBytes(artA)
+
+	for _, tt := range []struct {
+		name string
+		key  artifactKey
+		want []byte
+	}{
+		{"unset", nil, []byte{}},
+		{"set", artifactKey(raw), raw},
+	} {
+		t.Run("bytes/"+tt.name, func(t *testing.T) {
+			got, ok := tt.key.bind(false).([]byte)
+			if !ok {
+				t.Fatalf("bind(false) = %T, want []byte", tt.key.bind(false))
+			}
+
+			if got == nil {
+				t.Fatal("bound to SQL NULL, which matches no row")
+			}
+
+			if !bytes.Equal(got, tt.want) {
+				t.Errorf("bind(false) = %x, want %x", got, tt.want)
+			}
+		})
+	}
+
+	// The dashed form is what an artifact published before the storage
+	// change carries, and it has to compare as text against text.
+	if got := artifactKey(nil).bind(true); got != "" {
+		t.Errorf("bind(true) on an unset cursor = %#v, want an empty string", got)
+	}
+
+	if got := artifactKey(artA).bind(true); got != artA {
+		t.Errorf("bind(true) = %#v, want %q", got, artA)
+	}
+}

backend/explore/listenbrainz.go

@@ -13,6 +13,7 @@ import (
 	"net/http"
 	"slices"
 	"strings"
+	"sync/atomic"
 	"time"
 )
 
@@ -25,6 +26,19 @@ const (
 // responds with a non-2xx status code.
 var ErrListenBrainzHTTP = errors.New("listenbrainz HTTP error")
 
+// ErrListenBrainzUnauthorized is a 401: the endpoint wants a token, and
+// no retry will change that.
+//
+// It is separate from ErrListenBrainzHTTP because it is the one
+// failure that is about *this client* rather than about the thing being
+// asked for — which is what makes it the one worth latching. The
+// popularity endpoints answered 401 to every request on 2026-10-05, so
+// a discography backfill spent one rate-limited request per artist to
+// be told the same thing: 399 of them in a minute of a real library's
+// backfill, each one a log line and a wasted slot in the shared
+// limiter.
+var ErrListenBrainzUnauthorized = errors.New("listenbrainz requires a token")
+
 // ListenBrainzClient is a thin HTTP client for the ListenBrainz
 // popularity and labs APIs.  All requests are rate-limited via the
 // shared RateLimiter and cached via the shared Cache.
@@ -39,6 +53,13 @@ type ListenBrainzClient struct {
 	// SetBaseURL shape — so a test that points one client at an
 	// httptest server does not stop being parallel-safe.
 	baseURL string
+
+	// refused latches the first 401.  A token is a property of the
+	// installation, not of the artist being asked about, so the answer
+	// is the same for every later request and asking again is pure
+	// cost.  Per client rather than global so a test can have one that
+	// is refused and one that is not.
+	refused atomic.Bool
 }
 
 // NewListenBrainzClient creates a ListenBrainz API client.
@@ -56,6 +77,14 @@ func NewListenBrainzClient(
 	}
 }
 
+// Unauthorized reports whether this client has been refused with a 401
+// during its life.  A caller that is about to do a long pass of
+// requests should ask before starting it: the answer will not change
+// mid-pass.
+func (c *ListenBrainzClient) Unauthorized() bool {
+	return c.refused.Load()
+}
+
 // SetBaseURL redirects this client at another host.  Tests only.
 func (c *ListenBrainzClient) SetBaseURL(url string) {
 	c.baseURL = strings.TrimSuffix(url, "/")
@@ -489,6 +518,11 @@ func (c *ListenBrainzClient) doPost(
 func (c *ListenBrainzClient) doRequest(
 	ctx context.Context, method string, url string, body []byte,
 ) ([]byte, error) {
+	// Asked and answered, for the rest of this client's life.
+	if c.refused.Load() {
+		return nil, fmt.Errorf("%w: %s", ErrListenBrainzUnauthorized, url)
+	}
+
 	c.logger.Debug("listenbrainz rate limiter wait", "url", url)
 
 	if err := c.limiter.Wait(ctx); err != nil {
@@ -533,6 +567,21 @@ func (c *ListenBrainzClient) doRequest(
 		"status", resp.StatusCode,
 	)
 
+	if resp.StatusCode == http.StatusUnauthorized {
+		// Recorded once, at warning level, because the next thing this
+		// client does is stop asking: a log line per artist is the
+		// symptom this latch exists to remove.
+		if c.refused.CompareAndSwap(false, true) {
+			c.logger.Warn("listenbrainz refused this client: "+
+				"popularity data needs a token, so the rest of this "+
+				"run will not ask for it",
+				"url", url,
+			)
+		}
+
+		return nil, fmt.Errorf("%w: %s", ErrListenBrainzUnauthorized, url)
+	}
+
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		return nil, fmt.Errorf(
 			"%w: %d %s", ErrListenBrainzHTTP, resp.StatusCode, truncateBody(respBody),

backend/explore/listenbrainz_refusal_test.go

@@ -0,0 +1,90 @@
+package explore
+
+import (
+	"context"
+	"errors"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"sync/atomic"
+	"testing"
+
+	"yellowjacket/backend/database"
+)
+
+// #284: the popularity endpoints answered 401 to every request, so a
+// backfill spent one rate-limited request per artist to be told the same
+// thing — 399 of them in a minute against a real library. A token is a
+// property of the installation, not of the artist, so the first refusal
+// is the answer for the whole client.
+func TestListenBrainzLatchesARefusal(t *testing.T) {
+	t.Parallel()
+
+	var requests atomic.Int64
+
+	srv := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			requests.Add(1)
+			w.WriteHeader(http.StatusUnauthorized)
+		},
+	))
+	t.Cleanup(srv.Close)
+
+	c := NewListenBrainzClient(
+		NewRateLimiter(), NewCache(database.NewTestDB(t), slog.Default()), slog.Default(),
+	)
+	c.SetBaseURL(srv.URL)
+
+	for i := range 5 {
+		_, err := c.TopRecordingsForArtist(context.Background(), "an-mbid")
+
+		if !errors.Is(err, ErrListenBrainzUnauthorized) {
+			t.Fatalf("call %d: err = %v, want ErrListenBrainzUnauthorized", i, err)
+		}
+	}
+
+	if got := requests.Load(); got != 1 {
+		t.Errorf("requests = %d, want 1: the rest of the calls are the same answer", got)
+	}
+
+	if !c.Unauthorized() {
+		t.Error("Unauthorized() = false after a 401")
+	}
+}
+
+// A failure that a retry could fix must not latch: the artist stays
+// unmarked and the next run asks again.
+func TestListenBrainzDoesNotLatchATransientFailure(t *testing.T) {
+	t.Parallel()
+
+	var requests atomic.Int64
+
+	srv := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			requests.Add(1)
+			w.WriteHeader(http.StatusInternalServerError)
+		},
+	))
+	t.Cleanup(srv.Close)
+
+	c := NewListenBrainzClient(
+		NewRateLimiter(), NewCache(database.NewTestDB(t), slog.Default()), slog.Default(),
+	)
+	c.SetBaseURL(srv.URL)
+
+	for range 3 {
+		_, err := c.TopRecordingsForArtist(context.Background(), "an-mbid")
+
+		if !errors.Is(err, ErrListenBrainzHTTP) {
+			t.Fatalf("err = %v, want ErrListenBrainzHTTP", err)
+		}
+	}
+
+	if got := requests.Load(); got != 3 {
+		t.Errorf("requests = %d, want 3", got)
+	}
+
+	if c.Unauthorized() {
+		t.Error("Unauthorized() = true after a 500")
+	}
+}

backend/explore/publishedartifact_test.go

@@ -0,0 +1,266 @@
+package explore
+
+import (
+	"context"
+	"database/sql"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"yellowjacket/backend/database"
+)
+
+// Import of the artifact we actually publish, as a client imports it.
+//
+// Every other test here builds a fixture, and a fixture is a second
+// description of the storage format that can be wrong in the same
+// direction as the code reading it.  That is how #258 shipped: the
+// importer positioned its batch walk with a Go `string` cursor against
+// the artifact's 16-byte `mbid` column, and SQLite neither coerces
+// between TEXT and BLOB nor complains about the comparison — so the walk
+// merged nothing and never advanced, and no install could finish its
+// first index build.  The fixture that guards the walk writes the old
+// text encoding; the only compact fixture is one row, below the batch
+// size, so the bound query never ran.  Both passed throughout.
+//
+// So this one takes the published file and runs the client's own path
+// over it — checksum, decompress, merge — and asserts that what the
+// artifact holds is what the client ends up with.
+//
+// It skips without the path, so an ordinary test run pays nothing for
+// it, and the publish job is where it is meant to run:
+//
+//	YJ_CORE_INDEX_ARTIFACT=/tmp/core-index.db.zst \
+//	  go test -tags indexbuild -run TestImportPublishedArtifact \
+//	  ./backend/explore/
+//
+// The indexbuild tag is not incidental: that job's container has no GTK,
+// and the default tag set links the app through Wails.
+
+// publishedArtifactEnv points at the published artifact: the compressed
+// core-index.db.zst, or the unpacked core-index.db.
+const publishedArtifactEnv = "YJ_CORE_INDEX_ARTIFACT"
+
+// artifactTotals is the pair this test compares across the boundary.
+//
+// Rows is the whole point — a merge that lands fewer of them than the
+// artifact declares is a catalog that looks populated and is missing
+// things nobody can name — and popularity is the half whose absence was
+// reported when it happened, because it arrives only through the merge.
+type artifactTotals struct {
+	rows       int
+	withListen int
+}
+
+func TestImportPublishedArtifact(t *testing.T) {
+	published := strings.TrimSpace(os.Getenv(publishedArtifactEnv))
+	if published == "" {
+		t.Skipf("set %s=<core-index.db.zst> to import the published artifact",
+			publishedArtifactEnv)
+	}
+
+	if _, err := os.Stat(published); err != nil {
+		t.Fatalf("%s: %v", publishedArtifactEnv, err)
+	}
+
+	// A file-backed database rather than NewTestDB's in-memory one: the
+	// artifact is ~135MB and a million rows, which is not a thing to hold
+	// in RAM inside a test.  YJ_HOME is how NewDB is pointed somewhere
+	// disposable, and going through NewDB means this is the constructor,
+	// the schema and the read pool the app itself opens.
+	//
+	// Nothing closes it, because nothing can: `DB` has no Close and the
+	// app's handles are process-lifetime by design.  The directory is
+	// unlinked at cleanup and the file goes with it.
+	t.Setenv("YJ_HOME", t.TempDir())
+
+	db, err := database.NewDB(testLogger())
+	if err != nil {
+		t.Fatalf("open database: %v", err)
+	}
+
+	si := NewSearchIndex(db, nil, nil, testLogger())
+
+	// The checksum the publisher shipped, if it shipped one.  Every
+	// client verifies it and refuses the artifact when it does not
+	// match, so a wrong one breaks Explore for everyone who has not
+	// already imported — and nothing else would see it, because the
+	// comparison is between two files only the publisher has.
+	if want, ok := publishedChecksum(published); ok {
+		got, err := fileSHA256(published)
+		if err != nil {
+			t.Fatalf("checksum the artifact: %v", err)
+		}
+
+		if got != want {
+			t.Errorf("published artifact hashes to %s, but its .sha256 says %s",
+				got, want)
+		}
+	}
+
+	unpacked := unpackPublishedArtifact(t, si, published)
+
+	want, err := artifactTotalsOf(unpacked)
+	if err != nil {
+		t.Fatalf("count the artifact's rows: %v", err)
+	}
+
+	if err := si.importCoreArtifact(context.Background(), unpacked); err != nil {
+		t.Fatalf("importCoreArtifact: %v", err)
+	}
+
+	got, err := indexTotalsOf(db)
+	if err != nil {
+		t.Fatalf("count the index's rows: %v", err)
+	}
+
+	if got.rows != want.rows {
+		t.Errorf("merged %d rows, but the artifact holds %d",
+			got.rows, want.rows)
+	}
+
+	if got.withListen != want.withListen {
+		t.Errorf("%d rows carry a listen count, but the artifact holds %d of them",
+			got.withListen, want.withListen)
+	}
+
+	// The FTS index is rebuilt from the table once the merge is done, and
+	// it is what search actually reads: a merge that lands without it
+	// leaves Explore silently matching nothing, which is the state #258
+	// produced by a different route.
+	var indexed int
+	if err := db.QueryRowWriter(
+		"SELECT COUNT(*) FROM explore_index_fts",
+	).Scan(&indexed); err != nil {
+		t.Fatalf("count the FTS index: %v", err)
+	}
+
+	if indexed != got.rows {
+		t.Errorf("FTS index holds %d rows against the table's %d",
+			indexed, got.rows)
+	}
+
+	// And one row read back through the app's own path, which is the
+	// other direction of every conversion the merge makes: a byte MBID
+	// out of the table, the app's dashed form, and back in as a lookup.
+	var raw []byte
+	if err := db.QueryRowWriter(`
+		SELECT mbid FROM explore_index
+		WHERE entity_type = 1 /* artist */ AND popularity > 0
+		ORDER BY popularity DESC LIMIT 1`).Scan(&raw); err != nil {
+		t.Fatalf("read a stored mbid: %v", err)
+	}
+
+	dashed, err := mbidFromBytes(raw)
+	if err != nil {
+		t.Fatalf("the stored mbid is not one: %v", err)
+	}
+
+	artist := si.LookupArtistByMBID(dashed)
+	if artist == nil {
+		t.Fatalf("the artifact's most popular artist %s does not look up", dashed)
+	}
+
+	if artist.Popularity == 0 {
+		t.Errorf("artist %s came back with no popularity", dashed)
+	}
+}
+
+// publishedChecksum reads the sha256 the publisher wrote beside the
+// artifact, in `sha256sum` output form.  A missing file is not a
+// failure: it is only there when the artifact came from the publish job.
+func publishedChecksum(path string) (string, bool) {
+	body, err := os.ReadFile(path + ".sha256")
+	if err != nil {
+		return "", false
+	}
+
+	sum := strings.TrimSpace(string(body))
+	if i := strings.IndexAny(sum, " \t"); i > 0 {
+		sum = sum[:i]
+	}
+
+	if len(sum) != 64 {
+		return "", false
+	}
+
+	return strings.ToLower(sum), true
+}
+
+// unpackPublishedArtifact returns a path to the unpacked database,
+// going through the client's own decompression when it is handed the
+// compressed file that is actually published.
+func unpackPublishedArtifact(t *testing.T, si *SearchIndex, path string) string {
+	t.Helper()
+
+	if strings.HasSuffix(path, ".db") {
+		return path
+	}
+
+	// Copied into the test's own directory first: decompress writes
+	// beside the compressed file, and the publisher's directory is not
+	// this test's to write in.
+	staging := t.TempDir()
+	dst := filepath.Join(staging, coreArtifactFile)
+
+	src, err := os.Open(path)
+	if err != nil {
+		t.Fatalf("open the published artifact: %v", err)
+	}
+
+	defer func() { _ = src.Close() }()
+
+	out, err := os.Create(dst)
+	if err != nil {
+		t.Fatalf("create a staging copy: %v", err)
+	}
+
+	if _, err := io.Copy(out, src); err != nil {
+		t.Fatalf("copy the published artifact: %v", err)
+	}
+
+	if err := out.Close(); err != nil {
+		t.Fatalf("close the staging copy: %v", err)
+	}
+
+	fetcher := &artifactFetcher{si: si, stagingDir: staging}
+
+	if err := fetcher.decompress(context.Background()); err != nil {
+		t.Fatalf("decompress the published artifact: %v", err)
+	}
+
+	return fetcher.unpackedPath()
+}
+
+// artifactTotalsOf counts what an artifact file holds, read directly so
+// the numbers do not depend on anything the client does.
+func artifactTotalsOf(path string) (artifactTotals, error) {
+	db, err := sql.Open("sqlite", "file:"+path+"?mode=ro")
+	if err != nil {
+		return artifactTotals{}, err
+	}
+
+	defer func() { _ = db.Close() }()
+
+	var totals artifactTotals
+
+	err = db.QueryRow(`SELECT COUNT(*), COALESCE(SUM(popularity > 0), 0)
+		FROM explore_index`).Scan(&totals.rows, &totals.withListen)
+	if err != nil {
+		return artifactTotals{}, err
+	}
+
+	return totals, nil
+}
+
+// indexTotalsOf counts what the client ended up with.
+func indexTotalsOf(db *database.DB) (artifactTotals, error) {
+	var totals artifactTotals
+
+	err := db.QueryRowWriter(`SELECT COUNT(*), COALESCE(SUM(popularity > 0), 0)
+		FROM explore_index`).Scan(&totals.rows, &totals.withListen)
+
+	return totals, err
+}

backend/explore/searchindex.go

@@ -518,6 +518,13 @@ func (si *SearchIndex) BackfillLibraryDiscographies(ctx context.Context) {
 			break
 		}
 
+		// A refused client is refused for every artist: the rest of
+		// this pass would be the same 401, once per artist (#284).  The
+		// artists stay unmarked, so a run with a token picks them up.
+		if indexLB.Unauthorized() {
+			break
+		}
+
 		work <- mbid
 	}
 
@@ -534,6 +541,17 @@ func (si *SearchIndex) BackfillLibraryDiscographies(ctx context.Context) {
 		return
 	}
 
+	if indexLB.Unauthorized() {
+		si.logger.Warn("discography backfill stopped early: "+
+			"listenbrainz refused this client, and a token is what it wants",
+			"artists", total, "of", len(mbids),
+		)
+
+		job.logf(jobs.LevelWarn, "Stopped early: ListenBrainz needs a token")
+
+		return
+	}
+
 	job.logf(jobs.LevelInfo, "Filled in "+strconv.Itoa(total)+" artists")
 
 	si.logger.Info("discography backfill complete", "artists", total)

backend/explore/shelves.go

@@ -383,9 +383,13 @@ func (si *SearchIndex) topByPopularity(
 // MusicBrainz IDs, so this never touches the library tables and asks
 // one query rather than one per artist.
 //
-// The artists are drawn most-popular-owned-album first, so a large
+// **The row is drawn at random, and that is the whole point of it.**
-// library's pool is the part of it the user is likeliest to recognise
+// Ordered by popularity it was a second leaderboard: the same handful of
-// rather than whichever artists sort first.
+// big names appeared every time the page opened, which is not what "you
+// own one album by these artists" is saying. The pool is still bounded
+// to `pool` artists — a 4 000-artist library does not need all of them
+// ranked — but which of them, and which of their albums, is `RANDOM()`,
+// so the shelf is a different sample each visit.
 func (si *SearchIndex) unownedAlbumsBySinglyOwnedArtists(
 	ctx context.Context,
 	pool, limit int,
@@ -396,15 +400,17 @@ func (si *SearchIndex) unownedAlbumsBySinglyOwnedArtists(
 		 WHERE entity_type = 2 /* release_group */
 		   AND in_library = 0
 		   AND artist_mbid IN (
-		       SELECT artist_mbid FROM explore_index
+		       SELECT artist_mbid FROM (
-		       WHERE entity_type = 2 /* release_group */
+		           SELECT artist_mbid FROM explore_index
-		         AND in_library = 1
+		           WHERE entity_type = 2 /* release_group */
-		         AND artist_mbid != x''
+		             AND in_library = 1
-		       GROUP BY artist_mbid
+		             AND artist_mbid != x''
-		       HAVING COUNT(*) = 1
+		           GROUP BY artist_mbid
-		       ORDER BY MAX(popularity) DESC
+		           HAVING COUNT(*) = 1
+		       )
+		       ORDER BY RANDOM()
 		       LIMIT ?)
-		 ORDER BY popularity DESC
+		 ORDER BY RANDOM()
 		 LIMIT ?`,
 		pool, limit,
 	))

backend/explore/shelves_test.go

@@ -3,6 +3,7 @@ package explore
 import (
 	"context"
 	"log/slog"
+	"sort"
 	"testing"
 
 	"yellowjacket/backend/database"
@@ -202,6 +203,11 @@ func TestShelves_MoreFromOwnedNeedsExactlyOneOwnedAlbum(t *testing.T) {
 		titles = append(titles, album.Title)
 	}
 
+	// The row is a random sample, so the *set* is what is asserted and
+	// not the order — see `unownedAlbumsBySinglyOwnedArtists` for why
+	// the ordering was given up.
+	sort.Strings(titles)
+
 	if len(titles) != 2 || titles[0] != "Second" || titles[1] != "Third" {
 		t.Fatalf("albums = %v, want [Second Third]", titles)
 	}

backend/library/coverart.go

@@ -3,6 +3,7 @@ package library
 import (
 	"bytes"
 	"crypto/sha256"
+	"database/sql"
 	"encoding/hex"
 	"fmt"
 	"image"
@@ -69,6 +70,77 @@ func CoverArtFileSet(coverPath string) []string {
 	return paths
 }
 
+// sweepOrphanedCoverArt deletes the cover_art rows no album references
+// and returns their file paths, for the caller to remove from disk
+// after the transaction commits.  Cover art is referenced only by
+// albums.cover_art_id, so an orphan is a cover whose album is gone —
+// which is every album the caller just swept.
+//
+// One implementation because the scan path, RemoveFromLibrary and
+// RemoveLibrary all reach this state, and the scan side used to skip it
+// entirely while RemoveLibrary did it inline (#247).
+func (l *Library) sweepOrphanedCoverArt(tx *sql.Tx) ([]string, error) {
+	const orphanSQL = `
+		SELECT file_path FROM cover_art WHERE id NOT IN (
+			SELECT DISTINCT cover_art_id FROM albums
+			WHERE cover_art_id IS NOT NULL
+		)`
+
+	rows, err := tx.QueryContext(l.ctx, orphanSQL)
+	if err != nil {
+		return nil, fmt.Errorf("could not query orphaned cover art: %w", err)
+	}
+
+	var paths []string
+
+	for rows.Next() {
+		var filePath string
+
+		if err := rows.Scan(&filePath); err != nil {
+			l.logger.Warn("could not scan cover art path", "err", err)
+
+			continue
+		}
+
+		paths = append(paths, filePath)
+	}
+
+	// Close before the DELETE: the two run on the one writer connection.
+	if err := rows.Close(); err != nil {
+		l.logger.Warn("could not close cover art rows", "err", err)
+	}
+
+	if len(paths) > 0 {
+		if _, err := tx.ExecContext(l.ctx, `
+			DELETE FROM cover_art WHERE id NOT IN (
+				SELECT DISTINCT cover_art_id FROM albums
+				WHERE cover_art_id IS NOT NULL
+			)`); err != nil {
+			return nil, fmt.Errorf("could not delete orphaned cover_art: %w", err)
+		}
+	}
+
+	return paths, nil
+}
+
+// removeCoverArtFiles removes a cover original and its derived size
+// variants.  Only the original is stored in cover_art.file_path; the
+// _sm/_md/_lg tiers are derived filenames beside it, so they have to be
+// removed by name or they accumulate forever.
+func (l *Library) removeCoverArtFiles(coverPaths []string) {
+	for _, coverPath := range coverPaths {
+		for _, path := range CoverArtFileSet(coverPath) {
+			if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
+				l.logger.Warn(
+					"could not remove orphaned cover art file",
+					"path", path,
+					"err", err,
+				)
+			}
+		}
+	}
+}
+
 // saveCoverArt saves embedded cover art to the cache directory.
 // Returns the file path where the art was saved, or empty string
 // if no picture data.  Timing is recorded in the provided metrics.

backend/library/coverart_storage_test.go

@@ -8,6 +8,7 @@ import (
 
 	"yellowjacket/backend/coverart"
 	"yellowjacket/backend/database/sql/sqlcgen"
+	"yellowjacket/internal/testfixtures"
 )
 
 // TestScan_StoresOnlyCoverTiers pins the size decision: a scan writes
@@ -26,10 +27,9 @@ func TestScan_StoresOnlyCoverTiers(t *testing.T) {
 
 	lib, db := setupTestLibrary(t)
 
-	root, err := filepath.Abs("../../test_data/music_library_test")
+	// Load skips when the fixture library has not been generated, as
-	if err != nil {
+	// every other fixture test does.
-		t.Fatalf("resolve fixture path: %v", err)
+	root := testfixtures.Load(t).Root()
-	}
 
 	library, err := db.Queries.CreateLibrary(lib.ctx, sqlcgen.CreateLibraryParams{
 		Name: "Fixtures",

backend/library/crud.go

@@ -320,43 +320,12 @@ func (l *Library) RemoveLibrary(id int64) (*RemovalSummary, error) {
 
 	genresRemoved, _ := result.RowsAffected()
 
-	// 15. Collect orphaned cover_art file paths for post-commit cleanup.
+	// Collect and delete orphaned cover_art rows before the commit.  The
-	// SAFETY: Hand-crafted SELECT for orphaned cover art identification.
+	// shared helper is the one place this sweep lives, so the scan path,
-	// Parameterless.
+	// RemoveFromLibrary and this removal cannot drift (#247).
-	rows, err := tx.QueryContext(l.ctx,
+	orphanedCoverArtPaths, err := l.sweepOrphanedCoverArt(tx)
-		`SELECT file_path FROM cover_art WHERE id NOT IN (
-			SELECT DISTINCT cover_art_id FROM albums
-			WHERE cover_art_id IS NOT NULL
-		)`)
 	if err != nil {
-		return nil, fmt.Errorf("could not query orphaned cover art: %w", err)
+		return nil, err
-	}
-
-	var orphanedCoverArtPaths []string
-
-	for rows.Next() {
-		var filePath string
-		if err := rows.Scan(&filePath); err != nil {
-			l.logger.Warn("could not scan cover art path", "err", err)
-
-			continue
-		}
-
-		orphanedCoverArtPaths = append(orphanedCoverArtPaths, filePath)
-	}
-
-	if err := rows.Close(); err != nil {
-		l.logger.Warn("could not close cover art rows", "err", err)
-	}
-
-	// 16. Delete orphaned cover_art rows.
-	// SAFETY: Hand-crafted orphan cleanup SQL. Parameterless.
-	if _, err := tx.ExecContext(l.ctx,
-		`DELETE FROM cover_art WHERE id NOT IN (
-			SELECT DISTINCT cover_art_id FROM albums
-			WHERE cover_art_id IS NOT NULL
-		)`); err != nil {
-		return nil, fmt.Errorf("could not delete orphaned cover_art: %w", err)
 	}
 
 	// 17. Delete the library's tagging queue.  tagging_items holds a
@@ -392,20 +361,9 @@ func (l *Library) RemoveLibrary(id int64) (*RemovalSummary, error) {
 	// avoids a costly full re-index of all remaining tracks (~10s for
 	// 25K tracks).
 
-	// 21. Post-commit: Delete orphaned cover art files and their sized
+	// Post-commit: remove the orphaned cover art files and their sized
-	// variants.  Only the original is stored in cover_art.file_path; the
+	// variants.
-	// _sm/_md/_lg thumbnails are derived filenames beside it, so they
+	l.removeCoverArtFiles(orphanedCoverArtPaths)
-	// have to be removed by name or they accumulate forever.
-	for _, coverPath := range orphanedCoverArtPaths {
-		for _, path := range CoverArtFileSet(coverPath) {
-			if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
-				l.logger.Warn("could not remove orphaned cover art file",
-					"path", path,
-					"err", err,
-				)
-			}
-		}
-	}
 
 	// 22. Post-commit: Compact queue.
 	if l.removalHooks.CompactQueue != nil {

backend/library/library.go

@@ -1034,7 +1034,7 @@ func (l *Library) scanInternal(
 				}
 			}
 
-			// Remove from FTS5 search index.
+			// Remove from FTS5 search index and the lyrics index.
 			if err := l.db.DeleteSearchIndex(f.ID); err != nil {
 				l.logger.Warn(
 					"failed to delete FTS entry for orphan",
@@ -1045,6 +1045,16 @@ func (l *Library) scanInternal(
 				metrics.addWarning(path, "orphan", err)
 			}
 
+			if err := l.db.DeleteLyricsIndex(f.ID); err != nil {
+				l.logger.Warn(
+					"failed to delete lyrics index entry for orphan",
+					"id", f.ID,
+					"err", err,
+				)
+
+				metrics.addWarning(path, "orphan", err)
+			}
+
 			removed.Add(1)
 		}
 
@@ -1255,17 +1265,32 @@ func (l *Library) pruneEmptyEntities() {
 		}
 	}
 
+	// Cover art after albums: a cover whose album just went is
+	// unreferenced, and leaving the row behind keeps its files exempt
+	// from the janitor's covers sweep forever (#247).
+	orphanedCovers, err := l.sweepOrphanedCoverArt(tx)
+	if err != nil {
+		l.logger.Warn("could not sweep orphaned cover art", "err", err)
+
+		return
+	}
+
 	if err := tx.Commit(); err != nil {
 		l.logger.Warn("could not commit entity cleanup", "err", err)
 
 		return
 	}
 
-	if len(albumIDs) > 0 || len(artistIDs) > 0 || len(genreIDs) > 0 {
+	// Post-commit: the rows are gone, so their files can go too.
+	l.removeCoverArtFiles(orphanedCovers)
+
+	if len(albumIDs) > 0 || len(artistIDs) > 0 || len(genreIDs) > 0 ||
+		len(orphanedCovers) > 0 {
 		l.logger.Info("pruned empty library entities",
 			"albums", len(albumIDs),
 			"artists", len(artistIDs),
 			"genres", len(genreIDs),
+			"covers", len(orphanedCovers),
 		)
 	}
 }

backend/library/query.go

@@ -2,7 +2,6 @@ package library
 
 import (
 	"database/sql"
-	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -18,8 +17,6 @@ import (
 // searchTrackLimit bounds an FTS search's result set.
 const searchTrackLimit = 500
 
-var errNoTracksInLibrary = errors.New("no tracks in library")
-
 // Track is one audio file with everything a list needs to draw it.
 type Track struct {
 	TrackName        string
@@ -169,28 +166,46 @@ func (l *Library) GetTrackMBIDs(filePath string) TrackMBIDs {
 	}
 }
 
-// GetTracks returns every track in a library, or in all of them when
+// pathLookupChunk bounds the paths bound into one IN (...) query, well
-// libraryID is 0.
+// under SQLite's bind-variable limit.
+const pathLookupChunk = 500
+
+// GetTracksByPaths returns whole tracks for the given file paths, in
+// the order asked, dropping any path that is not in the library.
 //
-// The library id is a parameter rather than a second method because the
+// It is how the frontend resolves the tracks a surface is actually
-// two used to be separate queries, separate bindings and a branch at
+// showing (#279).  Track details from the queue, a playlist or a smart
-// every call site - and the scoped form costs nothing (measured: 23 ms
+// playlist used to look the path up in the whole library's track
-// against 21 ms over 26k rows).
+// array, which had to be loaded first — so it was fetched eagerly at
-func (l *Library) GetTracks(libraryID int64) ([]Track, error) {
+// startup, 20.5 MB at 26k tracks, to answer questions about a handful
-	rows, err := l.db.ReadQueries.GetTracks(l.ctx, libraryID)
+// of rows.
-	if err != nil {
+func (l *Library) GetTracksByPaths(paths []string) ([]Track, error) {
-		l.logger.Error("could not retrieve audio files", "error", err)
+	byPath := make(map[string]Track, len(paths))
 
-		return nil, fmt.Errorf("could not get tracks: %w", err)
+	for start := 0; start < len(paths); start += pathLookupChunk {
+		chunk := paths[start:min(start+pathLookupChunk, len(paths))]
+
+		rows, err := l.db.ReadQueries.GetTracksByPaths(l.ctx, chunk)
+		if err != nil {
+			return nil, fmt.Errorf("could not get tracks by path: %w", err)
+		}
+
+		for _, row := range rows {
+			byPath[row.FilePath] = trackFromRow(row)
+		}
 	}
 
-	l.logger.Info("audio file list", "count", len(rows), "libraryID", libraryID)
+	tracks := make([]Track, 0, len(byPath))
 
-	if len(rows) == 0 {
+	for _, path := range paths {
-		return nil, errNoTracksInLibrary
+		if t, ok := byPath[path]; ok {
+			tracks = append(tracks, t)
+			// A path asked twice is answered once.
+			delete(byPath, path)
+		}
 	}
 
-	return tracksFromRows(rows), nil
+	return tracks, nil
 }
 
 // SearchTracks runs the library's FTS index and returns whole tracks.

backend/library/removal_test.go

@@ -249,3 +249,53 @@ func TestCoverArtFileSet(t *testing.T) {
 		}
 	}
 }
+
+// Removing the last track of an album must take the album's cover art
+// with it — both the row and every derived file — or the row keeps its
+// files exempt from the janitor's covers sweep forever (#247).
+func TestRemoveFromLibrary_DeletesOrphanedCoverArt(t *testing.T) {
+	t.Parallel()
+
+	lib, _ := setupTestLibrary(t)
+
+	dir := t.TempDir()
+
+	// The largest tier is what cover_art.file_path names; write every
+	// variant so the sweep has a real set to remove.
+	for _, tier := range thumbnailTiers {
+		p := filepath.Join(dir, coverart.SizedFilename("abc123.jpg", tier.Suffix))
+		if err := os.WriteFile(p, []byte("img"), 0o600); err != nil {
+			t.Fatalf("write %s: %v", p, err)
+		}
+	}
+
+	cover := filepath.Join(dir, coverart.SizedFilename("abc123.jpg", "_lg"))
+
+	seedRemovableLibrary(t, lib, cover)
+
+	// Link the album to the cover so it is not orphaned until the track
+	// (and with it the album) goes.
+	if _, err := lib.db.ExecContext(
+		`UPDATE albums SET cover_art_id =
+			(SELECT id FROM cover_art WHERE file_path = ?)
+		 WHERE name = 'Test Album'`,
+		cover,
+	); err != nil {
+		t.Fatalf("link cover art: %v", err)
+	}
+
+	if _, err := lib.RemoveFromLibrary([]string{"/music/song.mp3"}); err != nil {
+		t.Fatalf("RemoveFromLibrary: %v", err)
+	}
+
+	if n := countRows(t, lib, "cover_art"); n != 0 {
+		t.Errorf("cover_art has %d rows after removal, want 0", n)
+	}
+
+	for _, tier := range thumbnailTiers {
+		p := filepath.Join(dir, coverart.SizedFilename("abc123.jpg", tier.Suffix))
+		if _, err := os.Stat(p); !os.IsNotExist(err) {
+			t.Errorf("cover art file still present: %s", filepath.Base(p))
+		}
+	}
+}

backend/library/remove_tracks.go

@@ -147,6 +147,11 @@ func (l *Library) RemoveFromLibrary(filePaths []string) (*RemovalResult, error)
 			l.logger.Warn("could not delete FTS entry for removed track",
 				"path", row.FilePath, "id", row.ID, "err", err)
 		}
+
+		if err := l.db.DeleteLyricsIndex(row.ID); err != nil {
+			l.logger.Warn("could not delete lyrics index entry for removed track",
+				"path", row.FilePath, "id", row.ID, "err", err)
+		}
 	}
 
 	// Deleting an audio_files row cascades to queue_tracks, so the

backend/library/scan_fixtures_test.go

@@ -58,15 +58,15 @@ func TestScan_FixtureLibraryLeavesNothingBehind(t *testing.T) {
 		t.Skip("fixture library is empty; run make testdata")
 	}
 
-	tracks, err := lib.GetTracks(0)
+	table, err := lib.GetTrackTable(0)
 	if err != nil {
-		t.Fatalf("GetTracks: %v", err)
+		t.Fatalf("GetTrackTable: %v", err)
 	}
 
 	// One track per file: the projection cannot multiply rows, because
 	// there is no join table left to multiply them.
-	if int64(len(tracks)) != files {
+	if int64(len(table.FilePath)) != files {
-		t.Errorf("GetTracks returned %d rows for %d files", len(tracks), files)
+		t.Errorf("GetTrackTable returned %d rows for %d files", len(table.FilePath), files)
 	}
 
 	// Nothing shared outlives what refers to it.

backend/library/trackpaths_test.go

@@ -0,0 +1,64 @@
+package library
+
+import (
+	"fmt"
+	"testing"
+)
+
+// #279: the track-details openers resolve the rows a surface is showing
+// by path, instead of finding them in the whole library's array.  The
+// answer must keep the caller's order (a batch dialog lists them as
+// selected), drop what is not in the library rather than invent it, and
+// survive more paths than one IN (...) can bind.
+func TestGetTracksByPaths(t *testing.T) {
+	t.Parallel()
+
+	lib, _ := setupTestLibrary(t)
+	seedAlbumsAndGenres(t, lib)
+
+	got, err := lib.GetTracksByPaths([]string{
+		"/other/b1.mp3", "/music/missing.mp3", "/music/a1.mp3", "/other/b1.mp3",
+	})
+	if err != nil {
+		t.Fatalf("GetTracksByPaths: %v", err)
+	}
+
+	paths := make([]string, 0, len(got))
+	for _, tr := range got {
+		paths = append(paths, tr.FilePath)
+	}
+
+	if want := "[/other/b1.mp3 /music/a1.mp3]"; fmt.Sprint(paths) != want {
+		t.Fatalf("paths = %v, want %s (caller order, missing dropped, duplicate once)", paths, want)
+	}
+
+	// Whole tracks, not just the key: details render every field.
+	if got[1].TrackName != "A1" || len(got[1].Genre) != 2 {
+		t.Errorf("a1 = %+v, want title A1 with two genres", got[1])
+	}
+}
+
+func TestGetTracksByPathsSpansChunks(t *testing.T) {
+	t.Parallel()
+
+	lib, _ := setupTestLibrary(t)
+	seedAlbumsAndGenres(t, lib)
+
+	// The real path last, behind more misses than one chunk binds, so a
+	// loop that only ran the first chunk would return nothing.
+	paths := make([]string, 0, pathLookupChunk+2)
+	for i := range pathLookupChunk + 1 {
+		paths = append(paths, fmt.Sprintf("/nowhere/%d.mp3", i))
+	}
+
+	paths = append(paths, "/music/a2.mp3")
+
+	got, err := lib.GetTracksByPaths(paths)
+	if err != nil {
+		t.Fatalf("GetTracksByPaths: %v", err)
+	}
+
+	if len(got) != 1 || got[0].FilePath != "/music/a2.mp3" {
+		t.Fatalf("got %d tracks (%v), want only /music/a2.mp3", len(got), got)
+	}
+}

backend/library/tracktable.go

@@ -0,0 +1,190 @@
+package library
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// TrackTable is every track in a library as the Tracks view uses it:
+// one array per column, and every repeated string stored once (#281).
+//
+// GetTracks used to answer with one object per track, which at 26 138
+// tracks was 20.5 MB of JSON — ~350 bytes a row of key names, four
+// cover URLs identical across an album, and artist, album and genre
+// strings repeated on every track of the album.  Encoding it cost the
+// backend ~170 MB of transient allocation and parsing it was the
+// WebView's peak.  Here the keys appear once, a repeated string is a
+// small integer, and the columns the Tracks view does not read are not
+// sent at all: LastPlayed and the three larger cover tiers belong to
+// the details dialog, which fetches whole tracks by path.
+//
+// The projection is still trackFromRow's — each row goes through it —
+// so this is an encoding of a Track, never a second description of
+// one.  frontend/src/utils/track-table.ts is the only decoder.
+type TrackTable struct {
+	// Strings holds every distinct string value; a string column holds
+	// indexes into it.  Index 0 is always "".
+	Strings []string `json:"strings"`
+	// GenreSets holds every distinct genre list, as indexes into
+	// Strings; Genre holds an index into it per track.
+	GenreSets [][]uint32 `json:"genreSets"`
+
+	FilePath         []string `json:"filePath"`
+	TrackName        []uint32 `json:"trackName"`
+	ArtistName       []uint32 `json:"artistName"`
+	Album            []uint32 `json:"album"`
+	Composer         []uint32 `json:"composer"`
+	FileType         []uint32 `json:"fileType"`
+	Genre            []uint32 `json:"genre"`
+	ArtistMBID       []uint32 `json:"artistMbid"`
+	ReleaseGroupMBID []uint32 `json:"releaseGroupMbid"`
+	RecordingMBID    []uint32 `json:"recordingMbid"`
+	CoverArtSmall    []uint32 `json:"coverArtSmall"`
+
+	// LengthMs is Track.TrackLength as the number it encodes.
+	LengthMs    []int64 `json:"lengthMs"`
+	TrackNumber []int64 `json:"trackNumber"`
+	DiscNumber  []int64 `json:"discNumber"`
+	Year        []int64 `json:"year"`
+	SampleRate  []int64 `json:"sampleRate"`
+	BitDepth    []int64 `json:"bitDepth"`
+	Channels    []int64 `json:"channels"`
+	Bitrate     []int64 `json:"bitrate"`
+	FileSize    []int64 `json:"fileSize"`
+	PlayCount   []int64 `json:"playCount"`
+}
+
+// trackTableBuilder interns strings and genre lists while rows are
+// appended.
+type trackTableBuilder struct {
+	table   TrackTable
+	strings map[string]uint32
+	genres  map[string]uint32
+}
+
+func newTrackTableBuilder(capacity int) *trackTableBuilder {
+	b := &trackTableBuilder{
+		strings: map[string]uint32{"": 0},
+		genres:  map[string]uint32{},
+	}
+
+	t := &b.table
+	t.Strings = []string{""}
+	t.FilePath = make([]string, 0, capacity)
+
+	for _, col := range b.stringColumns() {
+		*col = make([]uint32, 0, capacity)
+	}
+
+	for _, col := range b.intColumns() {
+		*col = make([]int64, 0, capacity)
+	}
+
+	t.Genre = make([]uint32, 0, capacity)
+
+	return b
+}
+
+// stringColumns are the interned columns, in one place so the builder
+// cannot allocate one and forget to fill it.
+func (b *trackTableBuilder) stringColumns() []*[]uint32 {
+	t := &b.table
+
+	return []*[]uint32{
+		&t.TrackName, &t.ArtistName, &t.Album, &t.Composer, &t.FileType,
+		&t.ArtistMBID, &t.ReleaseGroupMBID, &t.RecordingMBID, &t.CoverArtSmall,
+	}
+}
+
+func (b *trackTableBuilder) intColumns() []*[]int64 {
+	t := &b.table
+
+	return []*[]int64{
+		&t.LengthMs, &t.TrackNumber, &t.DiscNumber, &t.Year, &t.SampleRate,
+		&t.BitDepth, &t.Channels, &t.Bitrate, &t.FileSize, &t.PlayCount,
+	}
+}
+
+func (b *trackTableBuilder) intern(s string) uint32 {
+	if i, ok := b.strings[s]; ok {
+		return i
+	}
+
+	i := uint32(len(b.table.Strings)) //nolint:gosec // bounded by the row count
+
+	b.table.Strings = append(b.table.Strings, s)
+	b.strings[s] = i
+
+	return i
+}
+
+func (b *trackTableBuilder) internGenres(genres []string) uint32 {
+	key := strings.Join(genres, genreDelimiter)
+
+	if i, ok := b.genres[key]; ok {
+		return i
+	}
+
+	set := make([]uint32, len(genres))
+	for j, g := range genres {
+		set[j] = b.intern(g)
+	}
+
+	i := uint32(len(b.table.GenreSets)) //nolint:gosec // bounded by the row count
+
+	b.table.GenreSets = append(b.table.GenreSets, set)
+	b.genres[key] = i
+
+	return i
+}
+
+func (b *trackTableBuilder) add(tr Track) error {
+	lengthMs, err := strconv.ParseInt(tr.TrackLength, 10, 64)
+	if err != nil {
+		return fmt.Errorf("track %q length %q: %w", tr.FilePath, tr.TrackLength, err)
+	}
+
+	t := &b.table
+	t.FilePath = append(t.FilePath, tr.FilePath)
+
+	strs := []string{
+		tr.TrackName, tr.ArtistName, tr.Album, tr.Composer, tr.FileType,
+		tr.ArtistMBID, tr.ReleaseGroupMBID, tr.RecordingMBID, tr.CoverArtSmall,
+	}
+	for i, col := range b.stringColumns() {
+		*col = append(*col, b.intern(strs[i]))
+	}
+
+	ints := []int64{
+		lengthMs, tr.TrackNumber, tr.DiscNumber, tr.Year, tr.SampleRate,
+		tr.BitDepth, tr.Channels, tr.Bitrate, tr.FileSize, tr.PlayCount,
+	}
+	for i, col := range b.intColumns() {
+		*col = append(*col, ints[i])
+	}
+
+	t.Genre = append(t.Genre, b.internGenres(tr.Genre))
+
+	return nil
+}
+
+// GetTrackTable returns every track in a library, or in all of them
+// when libraryID is 0, as a TrackTable.  An empty library is an empty
+// table, not an error.
+func (l *Library) GetTrackTable(libraryID int64) (TrackTable, error) {
+	rows, err := l.db.ReadQueries.GetTracks(l.ctx, libraryID)
+	if err != nil {
+		return TrackTable{}, fmt.Errorf("could not get tracks: %w", err)
+	}
+
+	b := newTrackTableBuilder(len(rows))
+
+	for i := range rows {
+		if err := b.add(trackFromRow(rows[i])); err != nil {
+			return TrackTable{}, err
+		}
+	}
+
+	return b.table, nil
+}

backend/library/tracktable_test.go

@@ -0,0 +1,198 @@
+package library
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"testing"
+
+	"yellowjacket/backend/database"
+)
+
+// seedTableLibrary seeds n albums of perAlbum tracks each, with a cover
+// on every album, so the table has the repetition it exists to remove.
+func seedTableLibrary(t *testing.T, lib *Library, albums, perAlbum int) {
+	t.Helper()
+
+	for a := range albums {
+		for n := range perAlbum {
+			database.InsertTestTrack(t, lib.db, database.TestTrack{
+				FilePath: fmt.Sprintf(
+					"/music/artist-%d/album-%d/%02d - Some Track Title.flac", a%7, a, n+1,
+				),
+				Title:         fmt.Sprintf("Some Track Title %d", n+1),
+				Artist:        fmt.Sprintf("Artist %d", a%7),
+				ArtistMBID:    fmt.Sprintf("0b7a8d2e-0000-4000-8000-%012d", a%7),
+				Album:         fmt.Sprintf("Album Name %d", a),
+				AlbumMBID:     fmt.Sprintf("1c7a8d2e-0000-4000-8000-%012d", a),
+				RecordingMBID: fmt.Sprintf("2d7a8d2e-0000-4000-8000-%012d", a*100+n),
+				Genres:        []string{"Ambient", fmt.Sprintf("Genre %d", a%3)},
+				TrackNumber:   int64(n + 1),
+				DiscNumber:    1,
+				Year:          2000 + int64(a%20),
+				LengthMs:      200_000 + int64(n),
+				PlayCount:     int64(n),
+			})
+		}
+
+		res, err := lib.db.ExecContext(
+			"INSERT INTO cover_art (file_path, mime_type) VALUES (?, 'image/jpeg')",
+			fmt.Sprintf("/data/covers/%064d.jpg", a),
+		)
+		if err != nil {
+			t.Fatalf("seed cover: %v", err)
+		}
+
+		coverID, _ := res.LastInsertId()
+
+		if _, err := lib.db.ExecContext(
+			"UPDATE albums SET cover_art_id = ? WHERE name = ?",
+			coverID, fmt.Sprintf("Album Name %d", a),
+		); err != nil {
+			t.Fatalf("seed album cover: %v", err)
+		}
+	}
+}
+
+// decodeTable is the Go mirror of frontend/src/utils/track-table.ts,
+// for asserting the encoding loses nothing it claims to carry.
+func decodeTable(t *testing.T, tbl TrackTable) []Track {
+	t.Helper()
+
+	str := func(col []uint32, i int) string { return tbl.Strings[col[i]] }
+	tracks := make([]Track, len(tbl.FilePath))
+
+	for i := range tracks {
+		var genres []string
+		for _, g := range tbl.GenreSets[tbl.Genre[i]] {
+			genres = append(genres, tbl.Strings[g])
+		}
+
+		tracks[i] = Track{
+			FilePath:         tbl.FilePath[i],
+			TrackName:        str(tbl.TrackName, i),
+			ArtistName:       str(tbl.ArtistName, i),
+			Album:            str(tbl.Album, i),
+			Composer:         str(tbl.Composer, i),
+			FileType:         str(tbl.FileType, i),
+			ArtistMBID:       str(tbl.ArtistMBID, i),
+			ReleaseGroupMBID: str(tbl.ReleaseGroupMBID, i),
+			RecordingMBID:    str(tbl.RecordingMBID, i),
+			CoverArtSmall:    str(tbl.CoverArtSmall, i),
+			Genre:            genres,
+			TrackLength:      strconv.FormatInt(tbl.LengthMs[i], 10),
+			TrackNumber:      tbl.TrackNumber[i],
+			DiscNumber:       tbl.DiscNumber[i],
+			Year:             tbl.Year[i],
+			SampleRate:       tbl.SampleRate[i],
+			BitDepth:         tbl.BitDepth[i],
+			Channels:         tbl.Channels[i],
+			Bitrate:          tbl.Bitrate[i],
+			FileSize:         tbl.FileSize[i],
+			PlayCount:        tbl.PlayCount[i],
+		}
+	}
+
+	return tracks
+}
+
+// #281: the table is an encoding of trackFromRow's Track, minus the
+// fields the Tracks view does not read.  Decoding it must give back
+// exactly that, row for row.
+func TestTrackTableRoundTrip(t *testing.T) {
+	t.Parallel()
+
+	lib, _ := setupTestLibrary(t)
+	seedTableLibrary(t, lib, 6, 4)
+
+	tbl, err := lib.GetTrackTable(0)
+	if err != nil {
+		t.Fatalf("GetTrackTable: %v", err)
+	}
+
+	rows, err := lib.db.ReadQueries.GetTracks(lib.ctx, 0)
+	if err != nil {
+		t.Fatalf("GetTracks: %v", err)
+	}
+
+	if len(rows) != 24 || len(tbl.FilePath) != len(rows) {
+		t.Fatalf("table has %d rows, query %d, want 24", len(tbl.FilePath), len(rows))
+	}
+
+	got := decodeTable(t, tbl)
+
+	for i, row := range rows {
+		want := trackFromRow(row)
+		// Not carried: the details dialog fetches these by path.
+		want.LastPlayed, want.CoverArtPath, want.CoverArtMedium, want.CoverArtLarge = "", "", "", ""
+
+		if fmt.Sprintf("%+v", got[i]) != fmt.Sprintf("%+v", want) {
+			t.Fatalf("row %d:\n got %+v\nwant %+v", i, got[i], want)
+		}
+	}
+
+	// It was the cover, genre and name repetition that was paid for; a
+	// table that interned nothing would still round-trip.
+	if len(tbl.GenreSets) != 3 {
+		t.Errorf("genre sets = %d, want 3 distinct lists", len(tbl.GenreSets))
+	}
+
+	if a, b := tbl.CoverArtSmall[0], tbl.CoverArtSmall[1]; a != b || tbl.Strings[a] == "" {
+		t.Errorf("two tracks of one album hold cover indexes %d and %d", a, b)
+	}
+}
+
+// The point of the table, pinned: the same rows encode to a fraction of
+// the object-per-track JSON they replace.  A new column has to fit
+// under this or raise it on purpose.
+func TestTrackTableSizeBudget(t *testing.T) {
+	t.Parallel()
+
+	lib, _ := setupTestLibrary(t)
+	seedTableLibrary(t, lib, 40, 10)
+
+	tbl, err := lib.GetTrackTable(0)
+	if err != nil {
+		t.Fatalf("GetTrackTable: %v", err)
+	}
+
+	rows, err := lib.db.ReadQueries.GetTracks(lib.ctx, 0)
+	if err != nil {
+		t.Fatalf("GetTracks: %v", err)
+	}
+
+	asTable, err := json.Marshal(tbl)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	asObjects, err := json.Marshal(tracksFromRows(rows))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	perTrack := len(asTable) / len(rows)
+	ratio := float64(len(asTable)) / float64(len(asObjects))
+
+	t.Logf("table %d B (%d B/track), objects %d B, ratio %.2f",
+		len(asTable), perTrack, len(asObjects), ratio)
+
+	if ratio > 0.25 {
+		t.Errorf("table is %.0f%% of the object encoding, budget 25%%", ratio*100)
+	}
+}
+
+func TestTrackTableEmptyLibraryIsAnAnswer(t *testing.T) {
+	t.Parallel()
+
+	lib, _ := setupTestLibrary(t)
+
+	tbl, err := lib.GetTrackTable(0)
+	if err != nil {
+		t.Fatalf("an empty library is an empty table, not an error: %v", err)
+	}
+
+	if len(tbl.FilePath) != 0 || len(tbl.Strings) != 1 {
+		t.Errorf("empty table = %+v", tbl)
+	}
+}

backend/maintenance/maintenance_test.go

@@ -666,3 +666,120 @@ func TestExpiredHTTPCacheJob_TrimsToBudget(t *testing.T) {
 		t.Errorf("kept %q, want the longest-lived row", kept)
 	}
 }
+
+// TestStaleArtistMetadataJob pins the sweep's two keep rules: an owned
+// artist's metadata survives, a browsed artist's survives while it still
+// holds cached artwork, and everything else goes (#248).
+func TestStaleArtistMetadataJob(t *testing.T) {
+	t.Parallel()
+
+	db := database.NewTestDB(t)
+
+	const (
+		ownedMBID   = "11111111-1111-1111-1111-111111111111"
+		browsedMBID = "22222222-2222-2222-2222-222222222222"
+		staleMBID   = "33333333-3333-3333-3333-333333333333"
+	)
+
+	// The owned artist is in the library - which means a *file* says
+	// so.  An artists row on its own is not ownership.
+	database.InsertTestTrack(t, db, database.TestTrack{
+		FilePath:   "/music/owned.mp3",
+		Artist:     "Owned",
+		ArtistMBID: ownedMBID,
+	})
+
+	for _, mbid := range []string{ownedMBID, browsedMBID, staleMBID} {
+		if _, err := db.ExecContext(
+			`INSERT INTO artist_metadata (mbid, source, data, fetched_at)
+			 VALUES (?, 'wikidata-p18', x'00', CURRENT_TIMESTAMP)`,
+			mbid,
+		); err != nil {
+			t.Fatalf("seed artist_metadata for %s: %v", mbid, err)
+		}
+	}
+
+	// The browsed artist holds cached artwork, so its metadata is still
+	// referenced and must survive.
+	if _, err := db.ExecContext(
+		`INSERT INTO artist_images
+		   (artist_mbid, source, source_url, file_path)
+		 VALUES (?, 'test', 'http://x', '/art/primary.jpg')`,
+		browsedMBID,
+	); err != nil {
+		t.Fatalf("seed artist_images: %v", err)
+	}
+
+	if _, err := StaleArtistMetadataJob(db).Run(context.Background()); err != nil {
+		t.Fatalf("run job: %v", err)
+	}
+
+	for _, tc := range []struct {
+		mbid string
+		want int
+	}{
+		{ownedMBID, 1},
+		{browsedMBID, 1},
+		{staleMBID, 0},
+	} {
+		var n int
+		if err := db.QueryRowWriter(
+			"SELECT COUNT(*) FROM artist_metadata WHERE mbid = ?", tc.mbid,
+		).Scan(&n); err != nil {
+			t.Fatalf("count %s: %v", tc.mbid, err)
+		}
+
+		if n != tc.want {
+			t.Errorf("artist_metadata rows for %s = %d, want %d", tc.mbid, n, tc.want)
+		}
+	}
+}
+
+// TestStaleSearchClicksJob deletes only the clicks old enough to have
+// left the retention window (#249).
+func TestStaleSearchClicksJob(t *testing.T) {
+	t.Parallel()
+
+	db := database.NewTestDB(t)
+
+	count := func(mbid string) int {
+		t.Helper()
+
+		var n int
+		if err := db.QueryRowWriter(
+			"SELECT COUNT(*) FROM search_clicks WHERE entity_mbid = ?", mbid,
+		).Scan(&n); err != nil {
+			t.Fatalf("count %s: %v", mbid, err)
+		}
+
+		return n
+	}
+
+	seed := func(query, mbid, lastClicked string) {
+		t.Helper()
+
+		if _, err := db.ExecContext(
+			`INSERT INTO search_clicks
+			   (query, entity_mbid, entity_type, click_count, last_clicked)
+			 VALUES (?, ?, 'recording', 1, ?)`,
+			query, mbid, lastClicked,
+		); err != nil {
+			t.Fatalf("seed search_clicks: %v", err)
+		}
+	}
+
+	seed("tide", "aaaa", "2024-01-01 00:00:00") // stale
+	seed("tide", "bbbb", "2999-01-01 00:00:00") // recent
+
+	if _, err := StaleSearchClicksJob(db).Run(context.Background()); err != nil {
+		t.Fatalf("run job: %v", err)
+	}
+
+	if n := count("bbbb"); n != 1 {
+		t.Errorf("recent click was deleted: %d rows, want 1", n)
+	}
+
+	if n := count("aaaa"); n != 0 {
+		t.Errorf("stale click survived: %d rows, want 0", n)
+	}
+}

backend/maintenance/sweeps.go

@@ -628,3 +628,69 @@ func dirSize(dir string) (bytes, files int64) {
 
 	return bytes, files
 }
+
+// StaleArtistMetadataJob evicts long-lived artist metadata (bios, wiki
+// leads, relationships) for artists the user no longer has any reason
+// to keep around: not owned and holding no cached artwork.
+//
+// artist_metadata has no TTL by design — entity data changes rarely and
+// re-fetching spends someone else's rate limit — so without a sweep it
+// grows for the life of the install.  This is the "swept when the
+// artist is no longer referenced" contract the datamap always declared
+// for it and nothing ever performed (#248).
+func StaleArtistMetadataJob(db *database.DB) Job {
+	return Job{
+		Name:        "artist-metadata-sweep",
+		MinInterval: dailyInterval,
+		Run: func(_ context.Context) (Result, error) {
+			res, err := db.ExecContext(
+				`DELETE FROM artist_metadata
+				 WHERE mbid NOT IN (` + ownedArtistMBIDs + `)
+				   AND mbid NOT IN (
+				       SELECT artist_mbid FROM artist_images
+				   )`,
+			)
+			if err != nil {
+				return Result{}, fmt.Errorf(
+					"delete stale artist_metadata rows: %w", err,
+				)
+			}
+
+			rows, _ := res.RowsAffected()
+
+			return Result{RowsDeleted: rows}, nil
+		},
+	}
+}
+
+// searchClicksRetention is how long a search-click ranking signal stays
+// useful.  search_clicks is authored behavioural data — nothing that
+// owns a row ever drops it — so age is the ceiling that keeps the table
+// from growing without bound for the life of the install (#249).
+const searchClicksRetention = "-180 days"
+
+// StaleSearchClicksJob deletes search-click ranking rows older than the
+// retention window.  Rows are small and the table grows slowly, so this
+// runs daily and does almost nothing most runs.
+func StaleSearchClicksJob(db *database.DB) Job {
+	return Job{
+		Name:        "search-clicks-sweep",
+		MinInterval: dailyInterval,
+		Run: func(_ context.Context) (Result, error) {
+			res, err := db.ExecContext(
+				`DELETE FROM search_clicks
+				 WHERE last_clicked < datetime('now', ?)`,
+				searchClicksRetention,
+			)
+			if err != nil {
+				return Result{}, fmt.Errorf(
+					"delete stale search_clicks rows: %w", err,
+				)
+			}
+
+			rows, _ := res.RowsAffected()
+
+			return Result{RowsDeleted: rows}, nil
+		},
+	}
+}

backend/playlist/playlist.go

@@ -134,6 +134,12 @@ type Service struct {
 	libraryDir    LibraryDirProvider
 	favoritesConf FavoritesConfigProvider
 
+	// onDeleted, when set, is called after a playlist is deleted so
+	// cross-cutting state that points at it (the queue's "Playing
+	// from" label) can stop pointing at a playlist that no longer
+	// exists.  Wired from app.go, like Library.SetRemovalHooks.
+	onDeleted func(playlistID int64)
+
 	// dataDirOverride, when non-empty, replaces the OS user data
 	// directory as the base for the playlists folder. Set by tests to
 	// keep M3U writes out of the real user data directory.
@@ -166,6 +172,17 @@ func (s *Service) SetFavoritesConfig(
 	s.favoritesConf = provider
 }
 
+// SetOnPlaylistDeleted registers a callback invoked after a playlist is
+// deleted, for cross-cutting invalidation.
+//
+//wails:ignore // internal wiring, not part of the app's IPC surface.
+func (s *Service) SetOnPlaylistDeleted(onDeleted func(playlistID int64)) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.onDeleted = onDeleted
+}
+
 // ServiceStartup is v3's service lifecycle hook: it runs once the
 // runtime exists, and ctx is cancelled when the app shuts down.  It
 // replaces v2's SetContext, which had to be called by hand from
@@ -766,6 +783,17 @@ func (s *Service) DeletePlaylist(playlistID int64) error {
 
 	s.emitEvent(events.PlaylistDeleted, playlistID)
 
+	// Cross-cutting invalidation: the queue's "Playing from" label may
+	// point at this playlist, and a link to a playlist that no longer
+	// exists is worse than none.
+	s.mu.Lock()
+	onDeleted := s.onDeleted
+	s.mu.Unlock()
+
+	if onDeleted != nil {
+		onDeleted(playlistID)
+	}
+
 	// Recreate the default playlist if we just deleted it.
 	if s.defaultPlaylistID() == playlistID {
 		s.EnsureDefaultPlaylist()
@@ -3097,6 +3125,19 @@ func (s *Service) EvaluateSmartPlaylist(
 	return tracks, nil
 }
 
+// SuggestSmartPlaylistValues returns values of field present in the
+// library that contain needle, for the rule editor's value box.
+func (s *Service) SuggestSmartPlaylistValues(
+	field, needle string,
+) ([]string, error) {
+	values, err := smartplaylist.SuggestValues(s.db, field, needle)
+	if err != nil {
+		return nil, fmt.Errorf("suggest smart playlist values: %w", err)
+	}
+
+	return values, nil
+}
+
 // PreviewSmartPlaylist evaluates a rule set from raw JSON without
 // requiring a saved playlist. This powers live preview in the rule
 // editor — the frontend sends rules as they are being edited and

backend/queue/queue.go

@@ -1581,6 +1581,21 @@ func (q *Queue) dropSource() {
 	q.source = Source{}
 }
 
+// DropSourceForPlaylist clears the queue's "Playing from" label when
+// its source playlist is deleted.  A link back to a playlist that no
+// longer exists is worse than none, and the label otherwise survives
+// the deletion until the next SetQueue (#249).
+func (q *Queue) DropSourceForPlaylist(playlistID int64) {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	if (q.source.Type == "playlist" || q.source.Type == "smartPlaylist") &&
+		q.source.ID == playlistID {
+		q.dropSource()
+		q.persistState()
+	}
+}
+
 // commitMutation persists the current queue state after a mutation.
 // When reindex is true, track positions are renumbered first.
 // The caller must hold q.mu.

backend/queue/queue_test.go

@@ -535,3 +535,35 @@ func TestCycleRepeat_CyclesThroughModes(t *testing.T) {
 		t.Errorf("after third cycle: got %q, want %q", state.RepeatMode, RepeatOff)
 	}
 }
+
+// TestDropSourceForPlaylist clears the "Playing from" label when the
+// queue's source playlist is deleted, and leaves it alone otherwise
+// (#249).
+func TestDropSourceForPlaylist(t *testing.T) {
+	t.Parallel()
+
+	q, db := setupTestQueue(t)
+	paths := seedAudioFiles(t, db, 2)
+
+	q.SetQueue(paths, 0, false, Source{Type: "playlist", ID: 42, Label: "Road Trip"})
+	q.DropSourceForPlaylist(42)
+
+	if got := q.GetState().Source; got != (Source{}) {
+		t.Errorf("source = %+v, want empty after playlist 42 deleted", got)
+	}
+}
+
+func TestDropSourceForPlaylistIgnoresOtherPlaylists(t *testing.T) {
+	t.Parallel()
+
+	q, db := setupTestQueue(t)
+	paths := seedAudioFiles(t, db, 2)
+
+	source := Source{Type: "smartPlaylist", ID: 42, Label: "Road Trip"}
+	q.SetQueue(paths, 0, false, source)
+	q.DropSourceForPlaylist(7)
+
+	if got := q.GetState().Source; got != source {
+		t.Errorf("source = %+v, want %+v unchanged for a different playlist", got, source)
+	}
+}

backend/smartplaylist/smartplaylist.go

@@ -614,7 +614,12 @@ const leanTrackQuery = `SELECT
 	af.file_size,
 	af.play_count,
 	COALESCE(af.last_played, '') AS last_played
-FROM (
+FROM ` + leanTrackSource
+
+// leanTrackSource is the joined row every rule's column resolves
+// against, aliased af.  Shared by Evaluate and SuggestValues so a
+// suggestion is always a value a rule on the same field can match.
+const leanTrackSource = `(
 	SELECT
 		af.id,
 		af.file_path,
@@ -1117,3 +1122,79 @@ func splitGenres(concatenated string) []string {
 
 	return strings.Split(concatenated, genreDelimiter)
 }
+
+// suggestLimit bounds one suggestion answer: a combobox shows a
+// screenful, and the user narrows by typing.
+const suggestLimit = 50
+
+// errNoSuggestions is a field the editor does not offer values for.
+var errNoSuggestions = errors.New("field has no suggestions")
+
+// suggestFields are the fields whose values the rule editor suggests.
+// Every one is in fieldMap; numeric fields other than the years are
+// ranges, where a list of every value present is no help.
+var suggestFields = map[string]bool{
+	"title": true, "artist": true, "album": true, "genre": true,
+	"composer": true, "file_type": true, "year": true, "release_year": true,
+}
+
+// SuggestValues returns up to suggestLimit distinct values of field
+// present in the library that contain needle (case-insensitively),
+// sorted.
+//
+// The rule editor used to build these lists from libraryStore's
+// whole-library arrays, which made the editor one more reason to fetch
+// every track at startup (#279) — and gave it an empty list when the
+// arrays had not landed.  Asking for the values that match what has
+// been typed is a few hundred bytes, whatever the library's size.
+func SuggestValues(db *database.DB, field, needle string) ([]string, error) {
+	col, ok := fieldMap[field]
+	if !ok || !suggestFields[field] {
+		return nil, fmt.Errorf("%w: %q", errNoSuggestions, field)
+	}
+
+	pattern := "%" + escapeLike(needle) + "%"
+
+	// SAFETY: col comes from fieldMap, never from the caller; the
+	// needle is a bound parameter.
+	query := `SELECT DISTINCT CAST(af.` + col + ` AS TEXT) AS v FROM ` +
+		leanTrackSource + `
+		WHERE v != '' AND v != '0' AND v LIKE ? ESCAPE '\'
+		ORDER BY v COLLATE NOCASE LIMIT ?`
+
+	if field == "genre" {
+		query = `SELECT name FROM genres
+		WHERE name != '' AND name LIKE ? ESCAPE '\'
+		ORDER BY name COLLATE NOCASE LIMIT ?`
+	}
+
+	rows, err := db.QueryContext(query, pattern, suggestLimit)
+	if err != nil {
+		return nil, fmt.Errorf("suggest %s: %w", field, err)
+	}
+
+	defer func() { _ = rows.Close() }()
+
+	values := make([]string, 0, suggestLimit)
+
+	for rows.Next() {
+		var v string
+		if err := rows.Scan(&v); err != nil {
+			return nil, fmt.Errorf("suggest %s: %w", field, err)
+		}
+
+		values = append(values, v)
+	}
+
+	if err := rows.Err(); err != nil {
+		return nil, fmt.Errorf("suggest %s: %w", field, err)
+	}
+
+	return values, nil
+}
+
+// escapeLike makes needle match itself literally inside a LIKE pattern
+// with ESCAPE '\'.
+func escapeLike(needle string) string {
+	return strings.NewReplacer(`\`, `\\`, `%`, `\%`, `_`, `\_`).Replace(needle)
+}

backend/smartplaylist/suggest_test.go

@@ -0,0 +1,61 @@
+package smartplaylist
+
+import (
+	"errors"
+	"slices"
+	"testing"
+
+	"yellowjacket/backend/database"
+)
+
+// The rule editor's value box asks the backend for what matches the
+// text typed (#279), rather than building every list from the whole
+// library loaded into the frontend.
+func TestSuggestValues(t *testing.T) {
+	t.Parallel()
+
+	db := database.NewTestDB(t)
+	seedSmartPlaylistData(t, db)
+
+	cases := []struct {
+		field, needle string
+		want          []string
+	}{
+		// Case-insensitive substring, distinct, sorted.
+		{"artist", "q", []string{"QOTSA", "Queen"}},
+		{"album", "OPERA", []string{"A Night at the Opera"}},
+		// Genres come from the genre table, one value per genre, not
+		// from a concatenated per-track column.
+		{"genre", "rock", []string{
+			"Funk Rock", "Hard Rock", "Progressive Rock", "Rock", "Stoner Rock",
+		}},
+		// Years are numbers and are suggested as their text.
+		{"year", "199", []string{"1990", "1991"}},
+		// The needle is literal: a LIKE wildcard in it matches only itself.
+		{"title", "%", []string{}},
+		{"composer", "_", []string{}},
+	}
+
+	for _, tc := range cases {
+		got, err := SuggestValues(db, tc.field, tc.needle)
+		if err != nil {
+			t.Fatalf("SuggestValues(%q, %q): %v", tc.field, tc.needle, err)
+		}
+
+		if !slices.Equal(got, tc.want) {
+			t.Errorf("SuggestValues(%q, %q) = %q, want %q", tc.field, tc.needle, got, tc.want)
+		}
+	}
+}
+
+func TestSuggestValuesRefusesFieldsItDoesNotSuggest(t *testing.T) {
+	t.Parallel()
+
+	db := database.NewTestDB(t)
+
+	for _, field := range []string{"duration", "file_path", "title; DROP TABLE x"} {
+		if _, err := SuggestValues(db, field, ""); !errors.Is(err, errNoSuggestions) {
+			t.Errorf("SuggestValues(%q) err = %v, want errNoSuggestions", field, err)
+		}
+	}
+}

e2e/bench-tmp.mjs

@@ -0,0 +1,27 @@
+import { chromium } from '@playwright/test';
+const b = await chromium.launch({ executablePath: '/usr/bin/chromium' });
+const p = await b.newPage();
+await p.addInitScript({ path: '/mnt/vault/dev/golang/yellowjacket/.playwright/init-events.js' });
+await p.goto('http://localhost:34115', { waitUntil: 'load' });
+await p.evaluate(() => window.__yjEvents.ready(30000));
+const out = await p.evaluate(async () => {
+  const time = async (label, path, args, n = 5) => {
+    const ms = [];
+    for (let i = 0; i < n; i++) {
+      const t0 = performance.now();
+      await window.__yjEvents.call(path, args, 60000);
+      ms.push(performance.now() - t0);
+    }
+    ms.sort((a, b) => a - b);
+    return { label, medianMs: Math.round(ms[Math.floor(n / 2)]), all: ms.map((m) => Math.round(m)) };
+  };
+  return [
+    await time('GetTrackTable(0)', 'library.Library.GetTrackTable', [0], 4),
+    await time('GetAlbums(0)', 'library.Library.GetAlbums', [0], 4),
+    await time('SearchLocal(tide)', 'explore.Service.SearchLocal', ['tide'], 4),
+    await time('SearchLocal(rock)', 'explore.Service.SearchLocal', ['rock'], 4),
+    await time('SearchTracks(tide)', 'library.Library.SearchTracks', ['tide', 0], 4),
+  ];
+});
+console.log(JSON.stringify(out, null, 1));
+await b.close();

e2e/perf/measure.mjs

@@ -42,6 +42,13 @@
  *                 browse number below could not see this, because it
  *                 visits Explore without ever typing in it.
  *   heap          JS heap after a scripted browse, post-GC.  m3.
+ *   memory        what the app holds at rest after launch, before any
+ *                 view but the landing one is opened: the backend
+ *                 process's RSS and peak, its Go heap, the page's JS
+ *                 heap, and the bytes each binding returned on the way.
+ *                 Then the same after the first open of Tracks, and how
+ *                 long that open took to its first *row* — the number
+ *                 eager loading was buying (#280/#281).
  *
  * Usage:
  *   node e2e/perf/measure.mjs --label before
@@ -51,7 +58,7 @@
  * Requires a running app: `make dev-headless SEED=bulk`.
  */
 
-import { readFileSync, writeFileSync, mkdirSync, existsSync } from 'node:fs';
+import { readFileSync, writeFileSync, mkdirSync, existsSync, readdirSync } from 'node:fs';
 import { dirname, resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { chromium } from '@playwright/test';
@@ -190,6 +197,135 @@ const SEARCH_DEBOUNCE_MS = 150;
 
 /* -------------------------------------------------------------------- */
 
+/**
+ * The backend process's memory, from /proc and its own pprof endpoint.
+ *
+ * Linux and a dev build only (pprof is mounted by `-tags dev`); either
+ * missing is a null, not a failure — this is a measurement harness, and
+ * a number it cannot take is reported as absent rather than as zero.
+ */
+async function backendMemory() {
+	const out = { rssMB: null, peakMB: null, anonMB: null, goHeapInuseMB: null, goHeapHeldMB: null };
+	const pid = findBackendPid();
+
+	if (pid) {
+		try {
+			const status = readFileSync(`/proc/${pid}/status`, 'utf8');
+			const kb = (k) => Number(status.match(new RegExp(`^${k}:\\s+(\\d+)`, 'm'))?.[1] ?? NaN);
+
+			out.rssMB = round(kb('VmRSS') / 1024, 1);
+			out.peakMB = round(kb('VmHWM') / 1024, 1);
+			out.anonMB = round(kb('RssAnon') / 1024, 1);
+		} catch {
+			// The process went away between finding it and reading it.
+		}
+	}
+
+	try {
+		const text = await (await fetch('http://localhost:6060/debug/pprof/heap?debug=1')).text();
+		const field = (k) => Number(text.match(new RegExp(`^# ${k} = (\\d+)`, 'm'))?.[1] ?? NaN);
+
+		out.goHeapInuseMB = round(field('HeapInuse') / 1048576, 1);
+		// What the runtime holds from the OS: the RSS the heap accounts for.
+		out.goHeapHeldMB = round((field('HeapSys') - field('HeapReleased')) / 1048576, 1);
+	} catch {
+		// Not a dev build, or pprof is not listening.
+	}
+
+	return out;
+}
+
+/** The pid of the running `yj-dev` binary, found by name under /proc. */
+function findBackendPid() {
+	try {
+		for (const entry of readdirSync('/proc')) {
+			if (!/^\d+$/.test(entry)) continue;
+
+			try {
+				if (readFileSync(`/proc/${entry}/comm`, 'utf8').trim() === 'yj-dev') return entry;
+			} catch {
+				// Raced with an exiting process.
+			}
+		}
+	} catch {
+		// No /proc: not Linux.
+	}
+
+	return null;
+}
+
+/** Bytes returned per binding name, largest first. */
+function bytesByBinding(calls) {
+	const by = {};
+
+	for (const c of calls) by[c.path] = (by[c.path] ?? 0) + (c.bytes ?? 0);
+
+	return Object.fromEntries(
+		Object.entries(by)
+			.filter(([, b]) => b > 0)
+			.sort((a, b) => b[1] - a[1])
+			.map(([k, b]) => [k, round(b / 1048576, 2)]),
+	);
+}
+
+async function pageMemory(page, client) {
+	await client.send('HeapProfiler.collectGarbage');
+	await page.waitForTimeout(300);
+
+	const heap = await client.send('Runtime.getHeapUsage');
+	const dom = await client.send('Memory.getDOMCounters');
+
+	return { jsHeapMB: round(heap.usedSize / 1048576, 1), domNodes: dom.nodes };
+}
+
+async function measureMemory(page, client) {
+	// Settled: the landing view has loaded and any idle warming has run.
+	await page.waitForTimeout(5000);
+
+	const startupCalls = await page.evaluate(() => window.__yjPerf.calls);
+	const atRest = {
+		backend: await backendMemory(),
+		page: await pageMemory(page, client),
+		bytesByBindingMB: bytesByBinding(startupCalls),
+		totalBindingMB: round(startupCalls.reduce((n, c) => n + (c.bytes ?? 0), 0) / 1048576, 2),
+	};
+
+	// First open of Tracks, to its first row: what a user waits for when
+	// nothing was loaded ahead of them.
+	const since = await page.evaluate(() => performance.now());
+	const firstRowMs = await page.evaluate(async () => {
+		const t0 = performance.now();
+
+		document.dispatchEvent(new CustomEvent('navigate', { detail: { view: 'tracks' } }));
+
+		for (;;) {
+			const list = document.querySelector('#main-content > track-list:not(.view-hidden)');
+
+			if (list?.shadowRoot?.querySelector('[data-testid="track-row"]')) {
+				return Math.round(performance.now() - t0);
+			}
+
+			if (performance.now() - t0 > 60000) return null;
+			await new Promise((r) => requestAnimationFrame(r));
+		}
+	});
+	await page.waitForTimeout(2000);
+
+	const tracksCalls = await page.evaluate((t) => window.__yjPerf.since(t), since);
+
+	return {
+		atRest,
+		tracksOpen: {
+			firstRowMs,
+			bytesByBindingMB: bytesByBinding(tracksCalls),
+			backend: await backendMemory(),
+			page: await pageMemory(page, client),
+		},
+	};
+}
+
+/* -------------------------------------------------------------------- */
+
 async function measureStartup(page) {
 	const nav = await page.evaluate(() => {
 		const n = performance.getEntriesByType('navigation')[0];
@@ -224,20 +360,33 @@ async function measureStartup(page) {
 			scriptBytesBeforePaint,
 			requests: res.length,
 			crossOriginRequests: crossOrigin.length,
-			crossOriginHosts: [...new Set(crossOrigin.map((u) => new URL(u).host))],
+			crossOriginHosts: [...new Set(crossOrigin.map((u) => {
+				try {
+					return new URL(u).host;
+				} catch {
+					return u;
+				}
+			}))],
 		};
 	});
 
-	// "First row on screen" is the number a user experiences as startup;
+	// "First row on screen" is the number a user experiences as startup
-	// FCP fires on the chrome around an empty list.
+	// *when the app lands on Tracks*; FCP fires on the chrome around an
+	// empty list.
+	//
+	// The deadline is short because since #280 a landing on any other
+	// view leaves the track list unloaded, and this would otherwise
+	// spend a minute waiting for a row that is not coming. The number
+	// that means something either way is `memory.tracksOpen.firstRowMs`,
+	// which opens Tracks and waits for its first row deliberately.
 	const firstRowMs = await page.evaluate(async () => {
 		const t0 = performance.now();
-		const deadline = t0 + 60000;
+		const deadline = t0 + 2000;
 
 		for (;;) {
 			const list = document.querySelector('track-list');
 			const row = list?.shadowRoot?.querySelector('[role="row"], .track-row');
-			if (row) return Math.round(performance.now() - t0 + (performance.timeOrigin ? 0 : 0));
+			if (row) return Math.round(performance.now() - t0);
 			if (performance.now() > deadline) return null;
 			await new Promise((r) => setTimeout(r, 16));
 		}
@@ -337,7 +486,8 @@ async function measureTrackChange(page) {
 
 		await ev.call('queue.Queue.Clear', [], 10000).catch(() => {});
 
-		const tracks = await ev.call('library.Library.GetAllTracks', [], 60000);
+		// The columnar list (#281): only the paths are needed here.
+		const tracks = ((await ev.call('library.Library.GetTrackTable', [0], 60000))?.filePath ?? []).map((FilePath) => ({ FilePath }));
 		const paths = (tracks ?? []).slice(0, 4).map((t) => t.FilePath);
 		if (paths.length < 2) return { error: 'library too small to measure' };
 
@@ -435,7 +585,8 @@ async function measureFavouriteToggle(page) {
 		const ev = window.__yjEvents;
 		const perf = window.__yjPerf;
 
-		const tracks = await ev.call('library.Library.GetAllTracks', [], 60000);
+		// The columnar list (#281): only the paths are needed here.
+		const tracks = ((await ev.call('library.Library.GetTrackTable', [0], 60000))?.filePath ?? []).map((FilePath) => ({ FilePath }));
 		const paths = (tracks ?? []).map((t) => t.FilePath);
 		if (paths.length < per * count) {
 			return { error: `library too small: ${paths.length} tracks` };
@@ -671,7 +822,8 @@ async function measurePlaylistOpen(page, client) {
 		let pl = (existing ?? []).find((p) => (p.Name ?? p.name) === name);
 
 		if (!pl) {
-			const tracks = await ev.call('library.Library.GetAllTracks', [], 60000);
+			// The columnar list (#281): only the paths are needed here.
+		const tracks = ((await ev.call('library.Library.GetTrackTable', [0], 60000))?.filePath ?? []).map((FilePath) => ({ FilePath }));
 			const paths = (tracks ?? []).map((t) => t.FilePath);
 
 			if (paths.length < n) return { error: `library too small: ${paths.length}` };
@@ -1600,7 +1752,8 @@ async function measurePlayerBarPass(page) {
 		// Stage a loaded track.  Deliberately the same first tracks the
 		// track-change measurement already played, so this warms no cover
 		// art that a later measurement counts requests for.
-		const tracks = await ev.call('library.Library.GetAllTracks', [], 60000);
+		// The columnar list (#281): only the paths are needed here.
+		const tracks = ((await ev.call('library.Library.GetTrackTable', [0], 60000))?.filePath ?? []).map((FilePath) => ({ FilePath }));
 		const paths = (tracks ?? []).slice(0, 4).map((t) => t.FilePath);
 
 		if (paths.length < 2) return { error: 'library too small to measure' };
@@ -1835,6 +1988,12 @@ async function run(label) {
 		loadWallMs: Date.now() - t0,
 	};
 
+	// First of all: at rest means before any measurement opens a view.
+	console.log('  memory at rest, then Tracks first open…');
+	report.memory = await measureMemory(page, client);
+	await page.evaluate(() => document.dispatchEvent(
+		new CustomEvent('navigate', { detail: { view: 'home' } }),
+	));
 	console.log('  startup…');
 	report.startup = await measureStartup(page);
 	// Before anything else navigates: every view's first open has to be
@@ -1897,6 +2056,14 @@ async function run(label) {
 
 const ROWS = [
 	['First contentful paint', (r) => fmt(r.startup.firstContentfulPaintMs, 'ms')],
+	['At rest: backend RSS', (r) => fmt(r.memory?.atRest.backend.rssMB, 'MB')],
+	['At rest: backend peak RSS', (r) => fmt(r.memory?.atRest.backend.peakMB, 'MB')],
+	['At rest: Go heap held', (r) => fmt(r.memory?.atRest.backend.goHeapHeldMB, 'MB')],
+	['At rest: JS heap', (r) => fmt(r.memory?.atRest.page.jsHeapMB, 'MB')],
+	['At rest: binding bytes', (r) => fmt(r.memory?.atRest.totalBindingMB, 'MB')],
+	['Tracks first open: first row', (r) => fmt(r.memory?.tracksOpen.firstRowMs, 'ms')],
+	['Tracks open: backend peak RSS', (r) => fmt(r.memory?.tracksOpen.backend.peakMB, 'MB')],
+	['Tracks open: JS heap', (r) => fmt(r.memory?.tracksOpen.page.jsHeapMB, 'MB')],
 	['First track row', (r) => fmt(r.startup.firstRowAfterLoadMs, 'ms')],
 	['JS transferred', (r) => fmt(round(r.startup.scriptBytes / 1024), 'kB')],
 	['JS evaluated before first paint', (r) => fmt(round((r.startup.scriptBytesBeforePaint ?? 0) / 1024), 'kB')],
@@ -2000,7 +2167,11 @@ function compare(a, b) {
 		const p = resolve(OUT_DIR, `${l}.json`);
 		if (!existsSync(p)) throw new Error(`no measurement labelled '${l}' at ${p}`);
 
-		return JSON.parse(readFileSync(p, 'utf8'));
+		try {
+			return JSON.parse(readFileSync(p, 'utf8'));
+		} catch (err) {
+			throw new Error(`measurement '${l}' at ${p} is not valid JSON: ${err.message}`);
+		}
 	};
 
 	console.log(table([load(a), load(b)]));

e2e/specs/binding-names.spec.ts

@@ -0,0 +1,80 @@
+/**
+ * Every bound method the suite names by hand must exist.
+ *
+ * A binding call carries only a method id, so a spec that names a method
+ * the Go side no longer has fails at *runtime*, in whichever spec
+ * happens to call it, with `unknown bound method name` — and nothing
+ * before that. `library.Library.GetTracks` was replaced by
+ * `GetTrackTable` (#281) and four specs kept calling the old name: the
+ * suite reported twenty failures across transport, bottom-bar and
+ * reduced-motion specs, none of which mention the library list.
+ *
+ * The known names come from `support/method-ids.mjs`, which derives them
+ * from the generated bindings tree that `make bindings-check` keeps
+ * current — so this cannot disagree with what the app can answer.
+ *
+ * It asserts first that it read something: a glob that matched nothing
+ * would pass over an empty list.
+ */
+import { readFileSync, readdirSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { dirname, join } from 'node:path';
+
+import { test, expect } from '../support/fixtures.js';
+import { methodIDs } from '../support/method-ids.mjs';
+
+const here = dirname(fileURLToPath(import.meta.url));
+
+/** The specs, and the harness that calls bindings on their behalf. */
+const DIRS = [here, join(here, '..', 'support')];
+
+function sources(): Array<[string, string]> {
+  const out: Array<[string, string]> = [];
+
+  for (const dir of DIRS) {
+    for (const entry of readdirSync(dir)) {
+      if (!entry.endsWith('.ts')) continue;
+      if (entry.endsWith('.spec.ts') && entry === 'binding-names.spec.ts') continue;
+
+      const path = join(dir, entry);
+
+      out.push([path, readFileSync(path, 'utf8')]);
+    }
+  }
+
+  return out;
+}
+
+/** `'library.Library.GetTrackTable'` — package, service, method. */
+const NAMED_BINDING = /'([a-z][A-Za-z0-9]*\.[A-Z]\w*\.[A-Z]\w*)'/g;
+
+/**
+ * Names that are deliberately not bindings.
+ *
+ * `harness.spec.ts` calls an unknown method on purpose, to assert that
+ * the bridge rejects with a ReferenceError naming it rather than
+ * hanging — that spec is the reason a bad call is loud.
+ */
+const DELIBERATE = new Set(['queue.Queue.Nope']);
+
+test('every binding named by a spec exists', () => {
+  // `methodIDs()` is the id -> name map the recorder names calls with.
+  const known = new Set(methodIDs().values());
+  const files = sources();
+
+  // A sweep over an empty glob passes and proves nothing.
+  expect(files.length, 'specs and support files read').toBeGreaterThan(20);
+  expect(known.size, 'bound method names derived').toBeGreaterThan(100);
+
+  const unknown: string[] = [];
+
+  for (const [path, source] of files) {
+    for (const [, name] of source.matchAll(NAMED_BINDING)) {
+      if (known.has(name!) || DELIBERATE.has(name!)) continue;
+
+      unknown.push(`${name} (${path.split('/').pop()})`);
+    }
+  }
+
+  expect([...new Set(unknown)]).toEqual([]);
+});

e2e/specs/bottom-bar.spec.ts

@@ -1,4 +1,10 @@
-import { test, expect, callBinding, NO_QUEUE_SOURCE } from '../support/fixtures.js';
+import {
+  test,
+  expect,
+  callBinding,
+  libraryTracks,
+  NO_QUEUE_SOURCE,
+} from '../support/fixtures.js';
 import type { Page } from '@playwright/test';
 
 /**
@@ -39,15 +45,7 @@ const geometry = (app: Page) =>
 
 /** Something has to be playing before the transport draws a seek bar. */
 async function play(app: Page): Promise<void> {
-  const paths = await app.evaluate(async () => {
+  const paths = (await libraryTracks(app)).slice(0, 3).map((t) => t.FilePath);
-    const tracks = (await window.__yjEvents.call(
-      'library.Library.GetTracks',
-      [0],
-      10_000,
-    )) as { FilePath: string }[];
-
-    return tracks.slice(0, 3).map((t) => t.FilePath);
-  });
 
   await callBinding(app, 'queue.Queue.SetQueue', [
     paths,

e2e/specs/jobs-on-a-phone.spec.ts

@@ -60,6 +60,23 @@ const PHONE = { width: 424, height: 439 };
 const DESKTOP = { width: 1100, height: 800 };
 
 test.describe('background jobs on a phone', () => {
+  /**
+   * **State a spec stages is the spec's to clear.** `/__test/emit` writes
+   * to a store nothing resets, so the event that staged a job is the
+   * event that clears it — `JobStore` replaces its whole list from every
+   * snapshot, so `testctl` needs no special case.
+   *
+   * **Measured on #168: this does not currently outlive the page.** Every
+   * test gets a fresh page, and `JobStore.init()` refetches `GetJobs()`
+   * from a backend registry that `/__test/emit` never writes to, so the
+   * staged job is gone before the next spec starts. Ownership is stated
+   * rather than a live leak repaired — the leak needs a page that
+   * survives its own spec, and there is none today.
+   */
+  test.afterEach(async ({ testctl }) => {
+    await testctl.emit('JobsChanged', []);
+  });
+
   test('are shown in the band, without opening anything', async ({
     app,
     testctl,

e2e/specs/library-lazy.spec.ts

@@ -0,0 +1,58 @@
+/**
+ * #280: launching the app must not load the track list.
+ *
+ * Every collection used to be fetched at `DOMContentLoaded` and
+ * refetched on every invalidation, whichever view was showing. On a
+ * 26 138-track library the track list was 20.5 MB of that, and encoding
+ * it cost the backend ~170 MB of transient allocation — for someone
+ * looking at Home, which draws none of it. Measured on 50 000 tracks:
+ * 543 MB of backend RSS at rest before, 296 MB after.
+ *
+ * The negative assertion is the point, and it needs its complement: "no
+ * `GetTrackTable`" also holds on a build that fetches nothing at all,
+ * so the same spec opens Tracks and watches it arrive.
+ */
+import { test, expect, bindingCalls, navigateTo } from '../support/fixtures.js';
+
+const TRACKS = 'library.Library.GetTrackTable';
+
+/** The seed's default page, which is what a launch lands on. */
+const LANDING_VIEW = 'home';
+
+test('launching on Home does not load the track list', async ({ app }) => {
+  // Past the store's idle warm-up: "nothing was fetched" has to mean
+  // nothing, not "nothing has happened yet".
+  await app.waitForTimeout(3_500);
+
+  const calls = await bindingCalls(app);
+
+  expect(calls, 'the warm-up for the small collections ran').toContain(
+    'library.Library.GetAlbums',
+  );
+  expect(calls, `the track list was fetched at launch (${LANDING_VIEW})`).not.toContain(
+    TRACKS,
+  );
+});
+
+test('opening Tracks loads it, and only then', async ({ app }) => {
+  await app.waitForTimeout(1_000);
+  expect(await bindingCalls(app)).not.toContain(TRACKS);
+
+  await navigateTo(app, 'tracks');
+  await expect(app.getByTestId('track-row').first()).toBeVisible();
+
+  expect(await bindingCalls(app)).toContain(TRACKS);
+});
+
+test('a hover on the nav item starts the load before the click', async ({ app }) => {
+  await app.waitForTimeout(1_000);
+
+  const nav = app.getByTestId('nav-tracks');
+
+  // The pointer entering the item is the whole mechanism; nothing is
+  // clicked, so the data must arrive because of the hover alone.
+  await nav.hover();
+  await expect
+    .poll(async () => (await bindingCalls(app)).includes(TRACKS))
+    .toBe(true);
+});

e2e/specs/phone-entity-links.spec.ts

@@ -1,6 +1,7 @@
 import {
   test,
   expect,
+  libraryTracks,
   callBinding,
   openTheQueue,
   NO_QUEUE_SOURCE,
@@ -56,18 +57,11 @@ async function menuLabels(app: Page): Promise<string[]> {
  * the wrong "no link".
  */
 async function queueThree(app: Page): Promise<void> {
-  const paths = await app.evaluate(async () => {
+  const tracks = await libraryTracks(app);
-    const tracks = (await window.__yjEvents.call(
+  const paths = tracks
-      'library.Library.GetTracks',
+    .filter((t) => t.Album !== '' && t.ArtistName !== '')
-      [0],
+    .slice(0, 3)
-      10_000,
+    .map((t) => t.FilePath);
-    )) as { FilePath: string; Album: string; ArtistName: string }[];
-
-    return tracks
-      .filter((t) => t.Album !== '' && t.ArtistName !== '')
-      .slice(0, 3)
-      .map((t) => t.FilePath);
-  });
 
   await callBinding(app, 'queue.Queue.SetQueue', [
     paths,

e2e/specs/phone-now-playing.spec.ts

@@ -1,4 +1,4 @@
-import { test, expect } from '../support/fixtures.js';
+import { test, expect, libraryTracks } from '../support/fixtures.js';
 
 /**
  * Now Playing on a short screen (#51).
@@ -57,19 +57,15 @@ const REFLOW_AT = 500;
 
 /** Put a track in the player, so the view has art and names to lay out. */
 async function stageATrack(page: Page): Promise<void> {
-  await page.evaluate(async () => {
+  const paths = (await libraryTracks(page)).slice(0, 4).map((t) => t.FilePath);
-    const tracks = (await window.__yjEvents.call(
-      'library.Library.GetTracks',
-      [0],
-      10_000,
-    )) as { FilePath: string }[];
 
+  await page.evaluate(async (paths) => {
     await window.__yjEvents.call(
       'queue.Queue.SetQueue',
-      [tracks.slice(0, 4).map((t) => t.FilePath), 0, false, { type: '', id: 0, label: '' }],
+      [paths, 0, false, { type: '', id: 0, label: '' }],
       10_000,
     );
-  });
+  }, paths);
 }
 
 /** Open the full-screen view and wait for the shell to say so. */

e2e/specs/phone-progress-line.spec.ts

@@ -1,4 +1,5 @@
 import {
+  libraryTracks,
   test,
   expect,
   callBinding,
@@ -49,11 +50,7 @@ async function rectOf(app: Page, selector: string): Promise<Rect | null> {
  * three rectangles.
  */
 async function play(app: Page): Promise<void> {
-  const tracks = await callBinding<{ FilePath: string; TrackName: string }[]>(
+  const tracks = await libraryTracks(app);
-    app,
-    'library.Library.GetTracks',
-    [0],
-  );
 
   // `TrackName`, not `Title`: that is what the library model calls it.
   const long = tracks.find((t) => t.TrackName === LONG_TRACK);

e2e/specs/phone-search.spec.ts

@@ -171,8 +171,8 @@ test.describe('search on a phone', () => {
     // Attached, not visible: `wa-dialog`'s host is `display: contents`,
     // so the element carrying the testid always reports hidden — what
     // is visible is the native `<dialog>` inside it. That awkwardness
-    // is written down in CLAUDE.md and is why the assertion that this
+    // is why the assertion that this is really up is the role query
-    // is really up is the role query below.
+    // below.
     await expect(dialog).toBeAttached();
 
     // Named, which `getByRole` can answer and the a11y snapshot cannot

e2e/specs/phone-shell.spec.ts

@@ -1,4 +1,4 @@
-import { test, expect, LONG_TRACK } from '../support/fixtures.js';
+import { test, expect, LONG_TRACK, libraryTracks } from '../support/fixtures.js';
 
 /**
  * The phone shell (plan 016 B2, phase 1).
@@ -235,15 +235,8 @@ test.describe('the shell on a phone', () => {
     // nothing in particular and picked a 2-second track, which had
     // finished before the assertions ran. The placeholder check below
     // is what actually holds the property this test needs.
-    const started = await app.evaluate(async (longTitle) => {
+    const bare = (await libraryTracks(app)).find((t) => t.TrackName === LONG_TRACK);
-      const tracks = (await window.__yjEvents.call(
+    const started = await app.evaluate(async (bare) => {
-        'library.Library.GetTracks',
-        [0],
-        10_000,
-      )) as { FilePath: string; TrackName: string }[];
-
-      const bare = tracks.find((t) => t.TrackName === longTitle);
-
       if (!bare) return null;
 
       await window.__yjEvents.call(
@@ -254,7 +247,7 @@ test.describe('the shell on a phone', () => {
       await window.__yjEvents.call('queue.Queue.Play', [], 5_000);
 
       return bare.TrackName;
-    }, LONG_TRACK);
+    }, bare);
 
     expect(started).toBe(LONG_TRACK);
 

e2e/specs/phone-transport.spec.ts

@@ -1,4 +1,4 @@
-import { test, expect } from '../support/fixtures.js';
+import { test, expect, libraryTracks } from '../support/fixtures.js';
 
 /**
  * The phone's transport (#59, #56).
@@ -64,19 +64,15 @@ async function sizeOf(
 
 /** Put something in the queue, so the transport has a track to act on. */
 async function stageATrack(page: Page): Promise<void> {
-  await page.evaluate(async () => {
+  const paths = (await libraryTracks(page)).slice(0, 4).map((t) => t.FilePath);
-    const tracks = (await window.__yjEvents.call(
-      'library.Library.GetTracks',
-      [0],
-      10_000,
-    )) as { FilePath: string }[];
 
+  await page.evaluate(async (paths) => {
     await window.__yjEvents.call(
       'queue.Queue.SetQueue',
-      [tracks.slice(0, 4).map((t) => t.FilePath), 0, false, { type: '', id: 0, label: '' }],
+      [paths, 0, false, { type: '', id: 0, label: '' }],
       10_000,
     );
-  });
+  }, paths);
 }
 
 test.describe('the phone bar carries three controls', () => {

e2e/specs/play-count.spec.ts

@@ -40,6 +40,21 @@ const FINISH_TIMEOUT = 60_000;
 const libraryCalls = async (app: Page): Promise<string[]> =>
   (await bindingCalls(app)).filter((c) => c.startsWith('library.Library.'));
 
+/**
+ * The bindings that fetch a collection.
+ *
+ * A prefix test (GetAll*) used to stand in for this, and matched
+ * exactly one name — GetAllLibrariesWithTrackCounts — so the assertion
+ * below held whatever the app refetched. The sweep in
+ * binding-names.spec.ts is what found it.
+ */
+const COLLECTION_FETCHES = [
+  'library.Library.GetTrackTable',
+  'library.Library.GetAlbums',
+  'library.Library.GetArtists',
+  'library.Library.GetGenres',
+];
+
 /**
  * Select rows by dispatching on the row rather than clicking it.
  *
@@ -116,7 +131,7 @@ test.describe('a finished track', () => {
     const refetched = await libraryCalls(app);
 
     expect(
-      refetched.filter((c) => c.startsWith('library.Library.GetAll')),
+      refetched.filter((c) => COLLECTION_FETCHES.includes(c)),
       'a play refetched a collection',
     ).toEqual([]);
 

e2e/specs/queue-reorder.spec.ts

@@ -1,4 +1,5 @@
 import {
+  libraryTracks,
   test,
   expect,
   callBinding,
@@ -30,18 +31,7 @@ async function order(app: Page): Promise<string[]> {
 }
 
 async function queueFourAndOpen(app: Page): Promise<string[]> {
-  const paths: string[] = await app.evaluate(async () => {
+  const paths = (await libraryTracks(app)).slice(0, 4).map((t) => t.FilePath);
-    // One argument, and 0 means every library: the scoped and
-    // unscoped list queries collapsed into one when the schema did
-    // (plan 013 R3), so `GetTracks()` no longer exists to call.
-    const tracks = await window.__yjEvents.call(
-      'library.Library.GetTracks',
-      [0],
-      10_000,
-    );
-
-    return (tracks as { FilePath: string }[]).slice(0, 4).map((t) => t.FilePath);
-  });
 
   await callBinding(app, 'queue.Queue.SetQueue', [paths, 0, false, NO_QUEUE_SOURCE]);
 

e2e/specs/queue-selection.spec.ts

@@ -1,4 +1,5 @@
 import {
+  libraryTracks,
   test,
   expect,
   callBinding,
@@ -86,15 +87,11 @@ const selected = (app: Page) =>
  * is read back.
  */
 async function queueSixAndOpen(app: Page): Promise<void> {
-  const paths = await app.evaluate(async (longTitle) => {
+  // `TrackName`, not `Title`: the library model names it after the
-    // `TrackName`, not `Title`: the library model names it after the
+  // tag, and the *queue* is what calls it `title`.
-    // tag, and the *queue* is what calls it `title`.
+  const tracks = await libraryTracks(app);
-    const tracks = (await window.__yjEvents.call(
+  const longTitle = LONG_TRACK;
-      'library.Library.GetTracks',
+  const paths = (() => {
-      [0],
-      10_000,
-    )) as { FilePath: string; TrackName: string; Album: string }[];
-
     const long = tracks.find((t) => t.TrackName === longTitle);
 
     /**
@@ -131,7 +128,7 @@ async function queueSixAndOpen(app: Page): Promise<void> {
       long!.FilePath,
       ...rest.slice(3).map((t) => t.FilePath),
     ];
-  }, LONG_TRACK);
+  })();
 
   await callBinding(app, 'queue.Queue.SetQueue', [
     paths,

e2e/specs/reduced-motion.spec.ts

@@ -2,6 +2,7 @@ import {
   test,
   expect,
   callBinding,
+  libraryTracks,
   waitForEvent,
   NO_QUEUE_SOURCE,
 } from '../support/fixtures.js';
@@ -56,20 +57,9 @@ async function playTheLongOne(app: Page): Promise<void> {
     window.dispatchEvent(new CustomEvent('yj-scroll-mode-changed'));
   });
 
-  const paths: string[] = await app.evaluate(async (needle) => {
+  const paths: string[] = (await libraryTracks(app))
-    // One argument, and 0 means every library: the scoped and
+    .filter((t) => t.TrackName.startsWith(LONG_TITLE))
-    // unscoped list queries collapsed into one when the schema did
+    .map((t) => t.FilePath);
-    // (plan 013 R3), so `GetTracks()` no longer exists to call.
-    const tracks = await window.__yjEvents.call(
-      'library.Library.GetTracks',
-      [0],
-      10_000,
-    );
-
-    return (tracks as { TrackName: string; FilePath: string }[])
-      .filter((t) => t.TrackName.startsWith(needle))
-      .map((t) => t.FilePath);
-  }, LONG_TITLE);
 
   expect(paths.length).toBeGreaterThan(0);
 

e2e/specs/top-bar-fit.spec.ts

@@ -102,6 +102,22 @@ const collapsed = (page: Page) =>
   }));
 
 test.describe('the top bar fits the window', () => {
+  /**
+   * **State a spec stages is the spec's to clear** (#168). `/__test/emit`
+   * writes to a store nothing resets, and this file stages the widest job
+   * in the app, so it puts it back — with the same event, since the store
+   * replaces its whole list from every snapshot.
+   *
+   * **Measured: it does not currently outlive the page.** Every test gets
+   * a fresh page and `JobStore.init()` refetches `GetJobs()` from a
+   * backend registry `/__test/emit` never writes to, so nothing is being
+   * repaired here; the rule is stated because it costs one line and the
+   * leak would need only one spec that keeps a page alive.
+   */
+  test.afterEach(async ({ testctl }) => {
+    await testctl.emit('JobsChanged', []);
+  });
+
   /**
    * The phone's answer, which is not "it fits" (#57).
    *

e2e/support/fixtures.ts

@@ -96,6 +96,39 @@ export async function callBinding<T = unknown>(
   ) as Promise<T>;
 }
 
+/** A library track as the specs use it: the path and its names. */
+export interface LibraryTrack {
+  FilePath: string;
+  TrackName: string;
+  ArtistName: string;
+  Album: string;
+}
+
+/**
+ * Every track in the library, in the order the backend lists them.
+ *
+ * The list arrives as a columnar `TrackTable` since #281 (repeated
+ * strings sent once, as indexes into `strings`), so it cannot be read
+ * as an array of tracks any more. This reads the three columns the
+ * specs use; `frontend/src/utils/track-table.ts` is the real decoder.
+ */
+export async function libraryTracks(page: Page): Promise<LibraryTrack[]> {
+  const t = await callBinding<{
+    strings: string[];
+    filePath: string[];
+    trackName: number[];
+    artistName: number[];
+    album: number[];
+  }>(page, 'library.Library.GetTrackTable', [0]);
+
+  return (t.filePath ?? []).map((FilePath, i) => ({
+    FilePath,
+    TrackName: t.strings[t.trackName[i]!] ?? '',
+    ArtistName: t.strings[t.artistName[i]!] ?? '',
+    Album: t.strings[t.album[i]!] ?? '',
+  }));
+}
+
 /**
  * The binding calls the *app* made, newest last, as `pkg.Type.Method`.
  *

frontend/bindings/yellowjacket/backend/download/models.ts

@@ -121,6 +121,12 @@ export interface CandidateFile {
     "bitrate"?: number;
     "isAudio": boolean;
 
+    /**
+     * LengthMillis is the file's duration as the source reports it, or
+     * 0 when it does not.  Soulseek reports it for most audio files.
+     */
+    "lengthMillis"?: number;
+
     /**
      * expected track position
      */
@@ -453,10 +459,19 @@ export interface MatchScore {
     "albumFit": number;
 
     /**
-     * audio files vs expected count
+     * aligned tracks vs expected count
      */
     "completeness": number;
 
+    /**
+     * DurationFit is how well the aligned files' lengths agree with the
+     * expected tracks', and DurationKnown whether enough of them stated
+     * a length for that to count.  When it does not, the score is the
+     * four text signals alone, exactly as before durations were read.
+     */
+    "durationFit": number;
+    "durationKnown": boolean;
+
     /**
      * Anchored records whether an MBID drove this score.  Unanchored
      * matches are capped, because there is nothing to be right about.

frontend/bindings/yellowjacket/backend/library/index.ts

@@ -18,5 +18,6 @@ export type {
     ScanMetrics,
     ScanWarning,
     Track,
-    TrackMBIDs
+    TrackMBIDs,
+    TrackTable
 } from "./models.js";

frontend/bindings/yellowjacket/backend/library/library.ts

@@ -203,16 +203,12 @@ export function GetTrackMBIDs(filePath: string): $CancellablePromise<$models.Tra
 }
 
 /**
- * GetTracks returns every track in a library, or in all of them when
+ * GetTrackTable returns every track in a library, or in all of them
- * libraryID is 0.
+ * when libraryID is 0, as a TrackTable.  An empty library is an empty
- * 
+ * table, not an error.
- * The library id is a parameter rather than a second method because the
- * two used to be separate queries, separate bindings and a branch at
- * every call site - and the scoped form costs nothing (measured: 23 ms
- * against 21 ms over 26k rows).
  */
-export function GetTracks(libraryID: number): $CancellablePromise<$models.Track[] | null> {
+export function GetTrackTable(libraryID: number): $CancellablePromise<$models.TrackTable> {
-    return $Call.ByID(933082923, libraryID);
+    return $Call.ByID(1179690926, libraryID);
 }
 
 /**
@@ -222,6 +218,21 @@ export function GetTracksByGenre(genre: string, libraryID: number): $Cancellable
     return $Call.ByID(1674220245, genre, libraryID);
 }
 
+/**
+ * GetTracksByPaths returns whole tracks for the given file paths, in
+ * the order asked, dropping any path that is not in the library.
+ * 
+ * It is how the frontend resolves the tracks a surface is actually
+ * showing (#279).  Track details from the queue, a playlist or a smart
+ * playlist used to look the path up in the whole library's track
+ * array, which had to be loaded first — so it was fetched eagerly at
+ * startup, 20.5 MB at 26k tracks, to answer questions about a handful
+ * of rows.
+ */
+export function GetTracksByPaths(paths: string[] | null): $CancellablePromise<$models.Track[] | null> {
+    return $Call.ByID(3966945290, paths);
+}
+
 /**
  * IsScanActive returns whether a scan is currently running.
  */

frontend/bindings/yellowjacket/backend/library/models.ts

@@ -239,3 +239,60 @@ export interface TrackMBIDs {
     "releaseGroupMbid": string;
     "artistMbid": string;
 }
+
+/**
+ * TrackTable is every track in a library as the Tracks view uses it:
+ * one array per column, and every repeated string stored once (#281).
+ * 
+ * GetTracks used to answer with one object per track, which at 26 138
+ * tracks was 20.5 MB of JSON — ~350 bytes a row of key names, four
+ * cover URLs identical across an album, and artist, album and genre
+ * strings repeated on every track of the album.  Encoding it cost the
+ * backend ~170 MB of transient allocation and parsing it was the
+ * WebView's peak.  Here the keys appear once, a repeated string is a
+ * small integer, and the columns the Tracks view does not read are not
+ * sent at all: LastPlayed and the three larger cover tiers belong to
+ * the details dialog, which fetches whole tracks by path.
+ * 
+ * The projection is still trackFromRow's — each row goes through it —
+ * so this is an encoding of a Track, never a second description of
+ * one.  frontend/src/utils/track-table.ts is the only decoder.
+ */
+export interface TrackTable {
+    /**
+     * Strings holds every distinct string value; a string column holds
+     * indexes into it.  Index 0 is always "".
+     */
+    "strings": string[] | null;
+
+    /**
+     * GenreSets holds every distinct genre list, as indexes into
+     * Strings; Genre holds an index into it per track.
+     */
+    "genreSets": (number[] | null)[] | null;
+    "filePath": string[] | null;
+    "trackName": number[] | null;
+    "artistName": number[] | null;
+    "album": number[] | null;
+    "composer": number[] | null;
+    "fileType": number[] | null;
+    "genre": number[] | null;
+    "artistMbid": number[] | null;
+    "releaseGroupMbid": number[] | null;
+    "recordingMbid": number[] | null;
+    "coverArtSmall": number[] | null;
+
+    /**
+     * LengthMs is Track.TrackLength as the number it encodes.
+     */
+    "lengthMs": number[] | null;
+    "trackNumber": number[] | null;
+    "discNumber": number[] | null;
+    "year": number[] | null;
+    "sampleRate": number[] | null;
+    "bitDepth": number[] | null;
+    "channels": number[] | null;
+    "bitrate": number[] | null;
+    "fileSize": number[] | null;
+    "playCount": number[] | null;
+}

frontend/bindings/yellowjacket/backend/playlist/service.ts

@@ -309,6 +309,14 @@ export function SearchLibrary(query: string): $CancellablePromise<$models.Candid
     return $Call.ByID(3912116995, query);
 }
 
+/**
+ * SuggestSmartPlaylistValues returns values of field present in the
+ * library that contain needle, for the rule editor's value box.
+ */
+export function SuggestSmartPlaylistValues(field: string, needle: string): $CancellablePromise<string[] | null> {
+    return $Call.ByID(3718198115, field, needle);
+}
+
 /**
  * ToggleDefaultPlaylistTrack adds or removes a single track
  * from the default playlist.  Returns true if the track is now

frontend/bindings/yellowjacket/backend/queue/queue.ts

@@ -56,6 +56,16 @@ export function CycleRepeat(): $CancellablePromise<void> {
     return $Call.ByID(3510519482);
 }
 
+/**
+ * DropSourceForPlaylist clears the queue's "Playing from" label when
+ * its source playlist is deleted.  A link back to a playlist that no
+ * longer exists is worse than none, and the label otherwise survives
+ * the deletion until the next SetQueue (#249).
+ */
+export function DropSourceForPlaylist(playlistID: number): $CancellablePromise<void> {
+    return $Call.ByID(1435106374, playlistID);
+}
+
 /**
  * EmitCurrentState emits the current queue state to the frontend.
  * This is called after the frontend DOM is ready.

frontend/index.html

@@ -51,7 +51,15 @@
     <div class="content-area">
         <main class="main-panel" data-active-view="tracks" data-testid="main-content" id="main-content"
             tabindex="-1">
-            <track-list></track-list>
+            <!-- The first-paint content of the main panel. It is
+                 `view-hidden` because whether Tracks is the view to
+                 show is not known until `GetDefaultPage` answers, and a
+                 seed that is visible is a seed that is *active* -- which
+                 is what made the whole track list load at launch for a
+                 landing on Home (#280). The first navigation decides:
+                 it unhides and activates this element if the landing
+                 view is Tracks, and otherwise replaces it. -->
+            <track-list class="view-hidden"></track-list>
         </main>
         <queue-panel id="queue-panel"></queue-panel>
     </div>

frontend/index.ts

@@ -200,13 +200,18 @@ const mainContent = document.getElementById('main-content');
 // tracked as currentViewEl, is never hidden: two visible primary views
 // splitting the main panel between them regardless of which is
 // selected.
+//
+// It is deliberately not activated here. It is markup, not a decision:
+// the shell does not yet know which view the launch lands on, and
+// activating it starts the Tracks view's work — its data fetch, above
+// all (#280) — for a launch that is about to land on Home. The first
+// navigation is what activates whichever view it lands on.
 if (mainContent) {
     const initialTrackList = mainContent.querySelector('track-list');
 
     if (initialTrackList) {
         viewCache.set('tracks', initialTrackList as HTMLElement);
         currentViewEl = initialTrackList as HTMLElement;
-        activateView(currentViewEl);
     }
 }
 
@@ -580,10 +585,14 @@ async function handleNavigate(
         }
         default: {
             const fallback = document.createElement('div');
+            const message = document.createElement('p');
 
             fallback.style.padding = '1em';
             fallback.style.color = 'var(--yj-text-secondary, #b3b3b3)';
-            fallback.innerHTML = `<p>Coming soon: ${view}</p>`;
+            // textContent, not innerHTML: `view` comes from a navigation
+            // detail, which is app-supplied but not app-owned.
+            message.textContent = `Coming soon: ${view}`;
+            fallback.append(message);
             mainContent.appendChild(fallback);
             currentDetailEl = fallback;
         }
@@ -620,6 +629,10 @@ function warmViewChunks(): void {
 
 /** requestIdleCallback where it exists; WebKit2GTK does not have it. */
 function schedule(fn: () => void): void {
+    // SAFETY: `requestIdleCallback` is not in this project's DOM lib
+    // types, so it is read through an optional-property shape; the
+    // property is either absent (undefined) or the browser's own
+    // function, which is what the guard below checks.
     const ric = (
         window as unknown as {
             requestIdleCallback?: (cb: () => void) => number;

frontend/src/assets/icons/fa/solid/chevron-left.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 512"><!--! Font Awesome Free 7.3.1 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2026 Fonticons, Inc. --><path fill="currentColor" d="M9.4 233.4c-12.5 12.5-12.5 32.8 0 45.3l192 192c12.5 12.5 32.8 12.5 45.3 0s12.5-32.8 0-45.3L77.3 256 246.6 86.6c12.5-12.5 12.5-32.8 0-45.3s-32.8-12.5-45.3 0l-192 192z"/></svg>

frontend/src/components/combobox/combobox.ts

@@ -7,6 +7,11 @@ import { designTokens } from '../../styles/tokens.css';
  * keyboard navigation.  Accepts a flat `options` string array, filters as
  * the user types, and emits `combobox-change` when a value is selected.
  *
+ * It also emits `combobox-input` with `{ text }` whenever the text it
+ * filters by changes (typing, and the reset to empty on focus), so a
+ * host whose options are too many to hand over at once can fetch the
+ * ones matching what was typed instead (#279).
+ *
  * Key implementation detail: option `<li>` elements use `@mousedown` with
  * `e.preventDefault()` so that the input's `blur` event does not close the
  * dropdown before the click registers.
@@ -196,6 +201,7 @@ export class YjCombobox extends LitElement {
         this.filterText = input.value;
         this.open = true;
         this.highlightedIndex = -1;
+        this.announceInput();
     }
 
     private handleFocus() {
@@ -203,6 +209,17 @@ export class YjCombobox extends LitElement {
         this.filterText = '';
         this.open = true;
         this.highlightedIndex = -1;
+        this.announceInput();
+    }
+
+    private announceInput() {
+        this.dispatchEvent(
+            new CustomEvent('combobox-input', {
+                detail: { text: this.filterText },
+                bubbles: true,
+                composed: true,
+            }),
+        );
     }
 
     private handleBlur() {

frontend/src/components/explore-album-details/explore-album-details.ts

@@ -60,6 +60,7 @@ import '@awesome.me/webawesome/dist/components/dropdown-item/dropdown-item.js';
 import { dictByName } from '@utils/binding';
 import type { TrackDetails } from '@components/track-details/track-details.js';
 import { showTrackDetailsForPath } from '@utils/track-details-opener.js';
+import { openMusicBrainz } from '@utils/external-link';
 import '@components/playlist-picker/playlist-picker.js';
 import {
     ICON_CAN_REQUEST,
@@ -2942,7 +2943,7 @@ export class ExploreAlbumDetails extends LitElement implements ContextMenuHost {
 
         if (!track?.mbid) return;
 
-        window.open(`https://musicbrainz.org/recording/${track.mbid}`, '_blank', 'noopener');
+        openMusicBrainz(`/recording/${track.mbid}`);
     }
 
     /**

frontend/src/components/explore-artist-details/explore-artist-details.ts

@@ -4,6 +4,8 @@ import { customElement, property, state, query } from 'lit/decorators.js';
 import { classMap } from 'lit/directives/class-map.js';
 import { designTokens } from '../../styles/tokens.css';
 import { backButton } from '../../styles/back-button.css';
+import { albumCardStyles } from '../../styles/album-card.css';
+import '../scroll-row/scroll-row.js';
 import {
     LookupArtist,
     BrowseReleaseGroups,
@@ -46,11 +48,8 @@ import {
     libraryStatusFor,
     toggleRequest,
 } from '@utils/library-status';
-import {
+import { isOwned, ownershipLabel } from '@utils/ownership';
-    isOwned,
+import { openMusicBrainz } from '@utils/external-link';
-    ownershipLabel,
-    unownedStyles,
-} from '@utils/ownership';
 import { completenessStore } from '@store/completeness-store';
 import '../catalog-scope-notice/catalog-scope-notice.js';
 import type { CatalogScope } from '../catalog-scope-notice/catalog-scope-notice.js';
@@ -62,6 +61,7 @@ import {
     ContextMenuController,
     contextMenuStyles,
     isContextMenuKey,
+    MenuKeyboard,
 } from '@utils/context-menu-controller.js';
 import type { ContextMenuHost, MenuTarget } from '@utils/context-menu-controller.js';
 import '@awesome.me/webawesome/dist/components/popup/popup.js';
@@ -187,11 +187,11 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
     @state() private topReleasesExpanded = false;
     private topSectionStacked = false;
     private topSectionObserver?: ResizeObserver;
-    @state() private expandedDiscoGroups = new Set<string>();
+
-    /** Number of album cards that fit in one row of the discography grid. */
+    /** Whether the Play button's Shuffle dropdown is up. */
-    @state() private discoRowSize = 5;
+    @state() private playMenuOpen = false;
-    private discoObserver?: ResizeObserver;
+    private playMenuKeyboard = new MenuKeyboard(() => this.closePlayMenu());
-    @state() private similarExpanded = false;
+    private playOutsideAttached = false;
 
     /* ── Release prefetch ── */
 
@@ -221,6 +221,12 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
     @query('#context-menu')
     private contextMenuPopup!: MenuSurface;
 
+    @query('.play-menu-button')
+    private playMenuButton?: HTMLButtonElement;
+
+    @query('#artist-play-menu')
+    private playMenuPanel?: HTMLElement;
+
     @query('#playlist-submenu')
     private playlistSubmenuPopup?: WaPopup;
 
@@ -271,7 +277,7 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
         backButton,
         exploreLinkStyles,
         contextMenuStyles,
-        unownedStyles,
+        albumCardStyles,
         css`
             :host {
                 display: flex;
@@ -319,10 +325,45 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                 object-fit: cover;
             }
 
-            .artist-follow {
+            .artist-actions {
+                display: flex;
+                align-items: center;
+                gap: 8px;
+                flex-wrap: wrap;
                 margin-top: 10px;
             }
 
+            /* The Play button and its caret are one control, so they
+               are one box: no gap between them, and the caret carries
+               the same filled appearance as the button it extends. */
+            .play-split {
+                display: inline-flex;
+                align-items: stretch;
+            }
+
+            .play-menu-button {
+                display: inline-flex;
+                align-items: center;
+                justify-content: center;
+                width: 28px;
+                padding: 0;
+                border: none;
+                border-left: 1px solid rgba(0, 0, 0, 0.25);
+                border-radius: 0 6px 6px 0;
+                background: var(--yj-accent, #ffd43b);
+                color: var(--yj-accent-fg, #000);
+                cursor: pointer;
+            }
+
+            .play-menu-button:hover {
+                filter: brightness(1.1);
+            }
+
+            .play-menu-button:focus-visible {
+                outline: 2px solid var(--yj-accent-text, #ffd43b);
+                outline-offset: 2px;
+            }
+
             .artist-info {
                 display: flex;
                 flex-direction: column;
@@ -331,7 +372,7 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
             }
 
             .artist-title {
-                font-size: 24px;
+                font-size: 28px;
                 font-weight: 700;
                 color: var(--yj-text-primary, #fff);
                 white-space: nowrap;
@@ -359,6 +400,13 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                 flex-wrap: wrap;
             }
 
+            /* The listen count is a headline number, not metadata, so
+               it sits a size above the type/country line. */
+            .artist-listens {
+                font-size: var(--yj-text-lg);
+                color: var(--yj-text-secondary, #b3b3b3);
+            }
+
             .meta-separator {
                 opacity: 0.4;
             }
@@ -446,23 +494,6 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                 outline-offset: -2px;
             }
 
-            .artist-play-actions {
-                margin-top: 10px;
-                display: flex;
-                gap: 8px;
-                align-items: center;
-                flex-wrap: wrap;
-            }
-
-            .track-rank {
-                width: 24px;
-                text-align: right;
-                color: var(--yj-text-tertiary, #888);
-                font-size: var(--yj-text-md);
-                font-variant-numeric: tabular-nums;
-                flex-shrink: 0;
-            }
-
             .track-art {
                 width: 32px;
                 height: 32px;
@@ -489,6 +520,52 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                 opacity: 0.5;
             }
 
+            /* Play where you own the track, the request badge where you
+               do not — over the artwork rather than at the end of the
+               row, where it was a badge beside a row you can already
+               double-click. */
+            .track-art-overlay {
+                position: absolute;
+                inset: 0;
+                display: flex;
+                align-items: center;
+                justify-content: center;
+                border-radius: 4px;
+                background: rgba(0, 0, 0, 0.55);
+                visibility: hidden;
+                opacity: 0;
+                transition: opacity 0.15s ease, visibility 0.15s ease;
+            }
+
+            .track-art-play {
+                display: flex;
+                align-items: center;
+                justify-content: center;
+                padding: 0;
+                border: none;
+                background: none;
+                color: #fff;
+                font-size: 14px;
+                cursor: pointer;
+            }
+
+            @media (hover: hover) and (pointer: fine) {
+                .track-item:hover .track-art-overlay,
+                .track-item:focus-within .track-art-overlay {
+                    visibility: visible;
+                    opacity: 1;
+                }
+            }
+
+            /* No hover means no double-click either, so the overlay is
+               the only route to playing a top track and must be there. */
+            @media not all and (hover: hover) {
+                .track-art-overlay {
+                    visibility: visible;
+                    opacity: 1;
+                }
+            }
+
             .track-info {
                 flex: 1;
                 min-width: 0;
@@ -522,7 +599,6 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
             .track-item library-status-indicator {
                 flex-shrink: 0;
             }
-
             /* ── Top section (tracks + releases side-by-side) ── */
             .top-section-wrapper {
                 container-type: inline-size;
@@ -754,8 +830,30 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                 white-space: nowrap;
             }
 
-            .top-release-meta library-status-indicator {
+            .top-release-art .album-card-badge {
-                flex-shrink: 0;
+                position: absolute;
+                top: 4px;
+                left: 4px;
+                z-index: 1;
+                display: flex;
+                visibility: hidden;
+                opacity: 0;
+                transition: opacity 0.15s ease, visibility 0.15s ease;
+            }
+
+            @media (hover: hover) and (pointer: fine) {
+                .top-release-card:hover .album-card-badge,
+                .top-release-card:focus-within .album-card-badge {
+                    visibility: visible;
+                    opacity: 1;
+                }
+            }
+
+            @media not all and (hover: hover) {
+                .top-release-art .album-card-badge {
+                    visibility: visible;
+                    opacity: 1;
+                }
             }
 
 
@@ -773,150 +871,7 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                 margin: 0;
             }
 
-            .album-grid {
-                display: grid;
-                grid-template-columns: repeat(auto-fill, 140px);
-                gap: 16px;
-            }
-
-            .album-grid.collapsed {
-                grid-template-rows: 1fr;
-                overflow: hidden;
-            }
-
-            .disco-toggle {
-                display: flex;
-                align-items: center;
-                justify-content: center;
-                gap: 6px;
-                padding: 4px 10px;
-                margin-top: 4px;
-                border: none;
-                border-radius: 6px;
-                background: var(--yj-bg-overlay, rgba(255, 255, 255, 0.06));
-                color: var(--yj-text-secondary, #b3b3b3);
-                font-size: var(--yj-text-xs);
-                cursor: pointer;
-                transition: background 0.15s ease, color 0.15s ease;
-                width: 100%;
-            }
-
-            .disco-toggle:hover {
-                background: var(--yj-bg-hover, rgba(255, 255, 255, 0.1));
-                color: var(--yj-text-primary, #fff);
-            }
-
-            .disco-toggle wa-icon {
-                font-size: 11px;
-                transition: transform 0.2s ease;
-            }
-
-            .disco-toggle[aria-expanded='true'] wa-icon {
-                transform: rotate(180deg);
-            }
-
-            .album-card {
-                display: flex;
-                flex-direction: column;
-                gap: 6px;
-                padding: 8px;
-                border-radius: 8px;
-                cursor: pointer;
-                transition: background 0.15s ease;
-            }
-
-            .album-card:hover {
-                background: var(
-                    --yj-bg-overlay,
-                    rgba(255, 255, 255, 0.06)
-                );
-            }
-
-            .album-card:active {
-                transform: scale(0.97);
-            }
-
-            .album-art-container {
-                width: 100%;
-                aspect-ratio: 1;
-                border-radius: 4px;
-                overflow: hidden;
-                flex-shrink: 0;
-                position: relative;
-                background: var(--yj-bg-overlay, rgba(255, 255, 255, 0.06));
-            }
-
-            .album-art-container img {
-                width: 100%;
-                height: 100%;
-                object-fit: cover;
-                display: block;
-                border-radius: 4px;
-            }
-
-            .album-art-fallback {
-                display: flex;
-                align-items: center;
-                justify-content: center;
-                width: 100%;
-                height: 100%;
-                position: absolute;
-                inset: 0;
-            }
-
-            .album-art-fallback wa-icon {
-                color: var(--yj-text-tertiary, #888);
-                font-size: 24px;
-                opacity: 0.5;
-            }
-
-            .album-title {
-                font-weight: 500;
-                color: var(--yj-text-primary, #fff);
-                font-size: var(--yj-text-sm);
-                white-space: nowrap;
-                overflow: hidden;
-                text-overflow: ellipsis;
-            }
-
-            .album-meta {
-                display: flex;
-                align-items: center;
-                justify-content: space-between;
-                gap: 6px;
-                color: var(--yj-text-tertiary, #888);
-                font-size: var(--yj-text-xs);
-                min-height: 20px;
-            }
-
-            .album-meta-text {
-                display: flex;
-                align-items: center;
-                gap: 6px;
-                min-width: 0;
-                overflow: hidden;
-                text-overflow: ellipsis;
-                white-space: nowrap;
-            }
-
-            .album-meta library-status-indicator {
-                flex-shrink: 0;
-                margin-left: auto;
-            }
-
             /* ── Similar artists ── */
-            .similar-row {
-                display: grid;
-                grid-template-columns: repeat(auto-fill, 140px);
-                gap: 16px;
-                overflow: hidden;
-            }
-
-            .similar-row.collapsed {
-                grid-template-rows: 1fr;
-                overflow: hidden;
-            }
-
             .similar-artist-card {
                 display: flex;
                 flex-direction: column;
@@ -926,6 +881,9 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                 border-radius: 8px;
                 cursor: pointer;
                 text-align: center;
+                width: 120px;
+                box-sizing: border-box;
+                flex-shrink: 0;
                 transition: background 0.15s ease;
             }
 
@@ -1056,7 +1014,7 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
         this.unsubSimilarReady?.();
         if (this.discogFallbackTimer) clearTimeout(this.discogFallbackTimer);
         this.topSectionObserver?.disconnect();
-        this.discoObserver?.disconnect();
+        this.detachPlayOutsideClose();
     }
 
     /**
@@ -1083,17 +1041,14 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
 
     protected override firstUpdated() {
         this.observeTopSectionWidth();
-        this.observeDiscoWidth();
     }
 
     protected override updated() {
-        // Re-attach observers if elements appeared after initial render.
+        // Re-attach the observer if the section appeared after initial
+        // render.
         if (!this.topSectionObserver) {
             this.observeTopSectionWidth();
         }
-        if (!this.discoObserver) {
-            this.observeDiscoWidth();
-        }
     }
 
     /**
@@ -1126,32 +1081,6 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
         this.topSectionObserver.observe(wrapper);
     }
 
-    /**
-     * Watch the .content width and compute how many album cards
-     * fit in one row of the discography grid.
-     * Grid uses: repeat(auto-fill, minmax(140px, 1fr)) with 16px gap
-     * and album-card has 8px padding on each side.
-     */
-    private observeDiscoWidth() {
-        const content = this.renderRoot.querySelector('.content');
-        if (!content) return;
-
-        const CARD_MIN = 140;
-        const GAP = 16;
-
-        this.discoObserver = new ResizeObserver((entries) => {
-            for (const entry of entries) {
-                const width = entry.contentBoxSize?.[0]?.inlineSize ?? entry.contentRect.width;
-                const cols = Math.max(1, Math.floor((width + GAP) / (CARD_MIN + GAP)));
-                if (cols !== this.discoRowSize) {
-                    this.discoRowSize = cols;
-                }
-            }
-        });
-
-        this.discoObserver.observe(content);
-    }
-
     /* ── Data Loading ── */
 
     private async loadAllData() {
@@ -1862,6 +1791,8 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                 } catch {
                     // No image — letter avatar stays.
                 }
+
+                return undefined;
             }),
         );
     }
@@ -1999,6 +1930,65 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
         }
     }
 
+    /* ── Play / Shuffle split button ── */
+
+    /**
+     * Open the Play button's Shuffle dropdown.
+     *
+     * `page-header`'s overflow menu one control over: the same
+     * `MenuKeyboard`, the same document-level outside-close, and the
+     * same `menu-surface`, so the phone gets the bottom sheet rather
+     * than a popup that Chrome 113 clips.
+     */
+    private togglePlayMenu = (): void => {
+        if (this.playMenuOpen) {
+            this.closePlayMenu();
+
+            return;
+        }
+
+        this.playMenuOpen = true;
+
+        void this.updateComplete.then(() => {
+            if (!this.playMenuOpen) return;
+
+            this.playMenuKeyboard.open(
+                this.playMenuPanel ?? null,
+                this.playMenuButton ?? null,
+            );
+            this.attachPlayOutsideClose();
+        });
+    };
+
+    private closePlayMenu = (): void => {
+        if (!this.playMenuOpen) return;
+
+        this.detachPlayOutsideClose();
+        this.playMenuKeyboard.close();
+        this.playMenuOpen = false;
+    };
+
+    private onPlayOutsideDown = (e: Event): void => {
+        if (e.composedPath().includes(this.playMenuPanel as EventTarget)) return;
+        if (e.composedPath().includes(this.playMenuButton as EventTarget)) return;
+
+        this.closePlayMenu();
+    };
+
+    private attachPlayOutsideClose(): void {
+        if (this.playOutsideAttached) return;
+
+        this.playOutsideAttached = true;
+        document.addEventListener('mousedown', this.onPlayOutsideDown, true);
+    }
+
+    private detachPlayOutsideClose(): void {
+        if (!this.playOutsideAttached) return;
+
+        this.playOutsideAttached = false;
+        document.removeEventListener('mousedown', this.onPlayOutsideDown, true);
+    }
+
     /**
      * File path for one top track, resolved by recording MBID — the
      * same key `localId` was set from. Works whether or not the
@@ -2240,11 +2230,7 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
 
         if (!release?.mbid) return;
 
-        window.open(
+        openMusicBrainz(`/release-group/${release.mbid}`);
-            `https://musicbrainz.org/release-group/${release.mbid}`,
-            '_blank',
-            'noopener',
-        );
     }
 
     private onContextMenuAction(
@@ -2358,7 +2344,7 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
 
         if (!track?.recordingMbid) return;
 
-        window.open(`https://musicbrainz.org/recording/${track.recordingMbid}`, '_blank', 'noopener');
+        openMusicBrainz(`/recording/${track.recordingMbid}`);
     }
 
     /* ── Navigation ── */
@@ -2538,10 +2524,12 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                         : nothing}
                     ${this.renderArtistMeta()}
                     ${this.artist?.popularity && this.artist.popularity > 0
-                        ? html`<span class="artist-meta">${formatListenCount(this.artist.popularity)} plays on ListenBrainz</span>`
+                        ? html`<span class="artist-listens">${formatListenCount(this.artist.popularity)} plays on ListenBrainz</span>`
                         : nothing}
-                    ${this.renderPlayLibraryAction()}
+                    <div class="artist-actions">
-                    ${this.renderFollowAction()}
+                        ${this.renderPlayLibraryAction()}
+                        ${this.renderFollowAction()}
+                    </div>
                 </div>
             </div>
             <div class="content">
@@ -2572,25 +2560,53 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
         if (this.ownedLocalAlbumIds().length === 0) return nothing;
 
         return html`
-            <div class="artist-play-actions">
+            <div class="play-split">
                 <wa-button
                     size="small"
                     appearance="filled"
                     data-testid="artist-play-library"
+                    title="Play library tracks"
                     @click=${() => void this.playLibraryTracks(false)}
                 >
                     <wa-icon slot="start" name="play"></wa-icon>
-                    Play library tracks
+                    Play
                 </wa-button>
-                <wa-button
+                <menu-surface
-                    size="small"
+                    placement="bottom-start"
-                    appearance="outlined"
+                    .active=${this.playMenuOpen}
-                    data-testid="artist-shuffle-library"
+                    @menu-dismiss=${this.closePlayMenu}
-                    @click=${() => void this.playLibraryTracks(true)}
                 >
-                    <wa-icon slot="start" name="shuffle"></wa-icon>
+                    <button
-                    Shuffle
+                        slot="anchor"
-                </wa-button>
+                        class="play-menu-button"
+                        type="button"
+                        data-testid="artist-play-menu"
+                        aria-label="More play options"
+                        aria-haspopup="menu"
+                        aria-expanded=${this.playMenuOpen ? 'true' : 'false'}
+                        aria-controls="artist-play-menu"
+                        @click=${this.togglePlayMenu}
+                    >
+                        <wa-icon name="chevron-down"></wa-icon>
+                    </button>
+                    <div
+                        id="artist-play-menu"
+                        class="context-menu-panel"
+                        role="menu"
+                        aria-label="Play options"
+                    >
+                        <wa-dropdown-item
+                            data-testid="artist-shuffle-library"
+                            @click=${() => {
+                                this.closePlayMenu();
+                                void this.playLibraryTracks(true);
+                            }}
+                        >
+                            <wa-icon slot="icon" name="shuffle"></wa-icon>
+                            Shuffle
+                        </wa-dropdown-item>
+                    </div>
+                </menu-surface>
             </div>
         `;
     }
@@ -2786,25 +2802,27 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
         const request = downloadStore.requestFor(this.artistMBID);
 
         return html`
-            <div class="artist-follow">
+            <wa-button
-                <wa-button
+                size="small"
-                    size="small"
+                appearance=${request ? 'filled' : 'outlined'}
-                    appearance=${request ? 'filled' : 'outlined'}
+                data-testid="artist-follow"
-                    @click=${() => void this.toggleFollow(request?.id)}
+                title=${request
-                >
+                    ? 'Following this artist'
-                    <!-- This was bookmark-check, which is not in
+                    : 'Follow this artist for new releases'}
-                         names.txt and so has rendered the missing-icon
+                @click=${() => void this.toggleFollow(request?.id)}
-                         fallback — a circled question mark — on every
+            >
-                         followed artist since it was written. A
+                <!-- This was bookmark-check, which is not in
-                         backtick around that name would end this
+                     names.txt and so has rendered the missing-icon
-                         template literal, which is why there is none. -->
+                     fallback — a circled question mark — on every
-                    <wa-icon
+                     followed artist since it was written. A
-                        slot="start"
+                     backtick around that name would end this
-                        name=${request ? ICON_REQUESTED : ICON_CAN_REQUEST}
+                     template literal, which is why there is none. -->
-                    ></wa-icon>
+                <wa-icon
-                    ${request ? 'Following' : 'Follow for new releases'}
+                    slot="start"
-                </wa-button>
+                    name=${request ? ICON_REQUESTED : ICON_CAN_REQUEST}
-            </div>
+                ></wa-icon>
+                ${request ? 'Following' : 'Follow'}
+            </wa-button>
         `;
     }
 
@@ -2888,16 +2906,6 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
         this.topReleasesExpanded = !this.topReleasesExpanded;
     }
 
-    private toggleDiscoGroup(type: string) {
-        const next = new Set(this.expandedDiscoGroups);
-        if (next.has(type)) {
-            next.delete(type);
-        } else {
-            next.add(type);
-        }
-        this.expandedDiscoGroups = next;
-    }
-
     private renderTopSection() {
         const hasTracks = !this.loadingTracks && this.topTracks.length > 0;
         const hasReleases = !this.loadingTopReleases && this.topReleaseGroups.length > 0;
@@ -2971,6 +2979,31 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                                                                        }} />`
                                                                 : html`<wa-icon name="compact-disc"></wa-icon>`;
                                                         })()}
+                                                        <!-- Over the artwork, not beside the
+                                                             row: play where you own it, the
+                                                             request badge where you do not. -->
+                                                        <div class="track-art-overlay">
+                                                            ${owned
+                                                                ? html`<button
+                                                                      class="track-art-play"
+                                                                      type="button"
+                                                                      aria-label=${`Play ${t.trackName}`}
+                                                                      @click=${(e: Event) => {
+                                                                          e.stopPropagation();
+                                                                          void this.playTrack(t);
+                                                                      }}
+                                                                  >
+                                                                      <wa-icon name="play"></wa-icon>
+                                                                  </button>`
+                                                                : html`<library-status-indicator
+                                                                      status=${libraryStatusFor(false, t.recordingMbid)}
+                                                                      entity-type="track"
+                                                                      label=${t.trackName}
+                                                                      request-mbid=${t.recordingMbid}
+                                                                      request-artist=${t.artistName ?? ''}
+                                                                      size="18"
+                                                                  ></library-status-indicator>`}
+                                                        </div>
                                                     </div>
                                                     <div class="track-info">
                                                         <div class="track-title">${trackLink(t.trackName, t.releaseName, t.releaseGroupMbid ?? '', t.recordingMbid)}</div>
@@ -2979,15 +3012,6 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                                                     <span class="track-listens">
                                                         ${formatListenCount(t.totalListenCount)} plays
                                                     </span>
-                                                    ${owned
-                                                        ? nothing
-                                                        : html`<library-status-indicator
-                                                              status=${libraryStatusFor(false, t.recordingMbid)}
-                                                              entity-type="track"
-                                                              label=${t.trackName}
-                                                              request-mbid=${t.recordingMbid}
-                                                              request-artist=${t.artistName ?? ''}
-                                                          ></library-status-indicator>`}
                                                 </div>
                                             `;
                                         })}
@@ -3093,6 +3117,18 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                     <div class="album-art-fallback" style="${artURL ? 'display: none' : ''}">
                         <wa-icon name="compact-disc"></wa-icon>
                     </div>
+                    <div class="album-card-badge">
+                        <library-status-indicator
+                            status=${badge.status}
+                            owned=${badge.owned}
+                            expected=${badge.expected}
+                            entity-type="album"
+                            label=${rg.title}
+                            request-mbid=${rg.releaseGroupMbid}
+                            request-artist=${this.artist?.name ?? ''}
+                            size="21"
+                        ></library-status-indicator>
+                    </div>
                 </div>
                 <div class="top-release-text">
                     <div class="top-release-title" title="${rg.title}">
@@ -3102,18 +3138,6 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                         <div class="top-release-meta-text">
                             ${rg.date ? html`<span>${extractYear(rg.date)}</span>` : nothing}
                         </div>
-                        ${badge.status === 'in-library'
-                            ? nothing
-                            : html`<library-status-indicator
-                                  status=${badge.status}
-                                  owned=${badge.owned}
-                                  expected=${badge.expected}
-                                  entity-type="album"
-                                  label=${rg.title}
-                                  request-mbid=${rg.releaseGroupMbid}
-                                  request-artist=${this.artist?.name ?? ''}
-                                  size="18"
-                              ></library-status-indicator>`}
                     </div>
                 </div>
             </div>
@@ -3164,37 +3188,16 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
             <section>
                 <h3 class="section-header">Discography</h3>
                 ${groups.map(
-                    (g) => {
+                    (g) => html`
-                        const isExpanded = this.expandedDiscoGroups.has(g.type);
+                        <div class="disco-group">
-                        const rowSize = this.discoRowSize;
+                            <h4 class="disco-type-header">
-                        const showToggle = g.items.length > rowSize;
+                                ${g.type === 'Other' ? 'Other Releases' : g.type.endsWith('s') ? g.type : `${g.type}s`}
-                        const visibleItems = isExpanded ? g.items : g.items.slice(0, rowSize);
+                            </h4>
-
+                            <scroll-row>
-                        return html`
+                                ${g.items.map((rg) => this.renderAlbumCard(rg))}
-                            <div class="disco-group">
+                            </scroll-row>
-                                <h4 class="disco-type-header">
+                        </div>
-                                    ${g.type === 'Other' ? 'Other Releases' : g.type.endsWith('s') ? g.type : `${g.type}s`}
+                    `,
-                                </h4>
-                                <div class="album-grid">
-                                    ${visibleItems.map((rg) => this.renderAlbumCard(rg))}
-                                </div>
-                                ${showToggle
-                                    ? html`
-                                          <button
-                                              class="disco-toggle"
-                                              aria-expanded="${isExpanded}"
-                                              @click=${() => this.toggleDiscoGroup(g.type)}
-                                          >
-                                              ${isExpanded
-                                                  ? 'Show less'
-                                                  : `Show all ${g.items.length}`}
-                                              <wa-icon name="chevron-down"></wa-icon>
-                                          </button>
-                                      `
-                                    : nothing}
-                            </div>
-                        `;
-                    },
                 )}
             </section>
         `;
@@ -3234,23 +3237,25 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                     <div class="album-art-fallback" style="${artURL ? 'display: none' : ''}">
                         <wa-icon name="compact-disc"></wa-icon>
                     </div>
+                    <div class="album-card-badge">
+                        <library-status-indicator
+                            status=${badge.status}
+                            owned=${badge.owned}
+                            expected=${badge.expected}
+                            entity-type="album"
+                            label=${rg.title}
+                            request-mbid=${rg.mbid}
+                            request-artist=${this.artist?.name ?? ''}
+                            size="23"
+                        ></library-status-indicator>
+                    </div>
                 </div>
                 <div class="album-title" title="${rg.title}">${rg.title}</div>
+                <div class="album-artist">${rg.artistCredit ?? ''}</div>
                 <div class="album-meta">
                     <div class="album-meta-text">
                         ${year ? html`<span>${year}</span>` : nothing}
                     </div>
-                    ${badge.status === 'in-library'
-                        ? nothing
-                        : html`<library-status-indicator
-                              status=${badge.status}
-                              owned=${badge.owned}
-                              expected=${badge.expected}
-                              entity-type="album"
-                              label=${rg.title}
-                              request-mbid=${rg.mbid}
-                              request-artist=${this.artist?.name ?? ''}
-                          ></library-status-indicator>`}
                 </div>
             </div>
         `;
@@ -3266,15 +3271,12 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
         // Cap the similar-artists list at 10 to avoid a very long list.
         const maxSimilar = 10;
         const artists = this.similarArtists.slice(0, maxSimilar);
-        const showToggle = artists.length > this.discoRowSize;
-        const collapsed = !this.similarExpanded && showToggle;
-        const visible = collapsed ? artists.slice(0, this.discoRowSize) : artists;
 
         return html`
             <section>
                 <h3 class="section-header">Similar Artists</h3>
-                <div class="similar-row ${collapsed ? 'collapsed' : ''}">
+                <scroll-row>
-                    ${visible.map((a) => {
+                    ${artists.map((a) => {
                         const imgURL = this.similarImageURLs.get(a.artistMbid);
                         return html`
                             <div
@@ -3313,21 +3315,7 @@ export class ExploreArtistDetails extends LitElement implements ContextMenuHost
                             </div>
                         `;
                     })}
-                </div>
+                </scroll-row>
-                ${showToggle
-                    ? html`
-                          <button
-                              class="disco-toggle"
-                              aria-expanded="${this.similarExpanded}"
-                              @click=${() => { this.similarExpanded = !this.similarExpanded; }}
-                          >
-                              ${this.similarExpanded
-                                  ? 'Show less'
-                                  : `Show all ${artists.length}`}
-                              <wa-icon name="chevron-down"></wa-icon>
-                          </button>
-                      `
-                    : nothing}
             </section>
         `;
     }

frontend/src/components/explore-view/explore-view.ts

@@ -1,10 +1,7 @@
 import { avatarBackground } from '@utils/avatar-color';
 import { albumBadgeFor, libraryStatusFor } from '@utils/library-status';
-import {
+import { isOwned, ownershipLabel } from '@utils/ownership';
-    isOwned,
+import { openMusicBrainz } from '@utils/external-link';
-    ownershipLabel,
-    unownedStyles,
-} from '@utils/ownership';
 import { completenessStore } from '@store/completeness-store';
 import { downloadStore } from '@store/download-store';
 import { LitElement, html, css, nothing } from 'lit';
@@ -13,6 +10,8 @@ import { classMap } from 'lit/directives/class-map.js';
 import '@components/page-header/page-header';
 import { designTokens } from '../../styles/tokens.css';
 import { srOnly } from '../../styles/sr-only.css';
+import { albumCardStyles } from '../../styles/album-card.css';
+import '../scroll-row/scroll-row.js';
 import { SearchLocal, SearchLyrics, GetThumbnail, GetThumbnails, GetArtistImageURL, GetArtistImagesCachedPaths, GetExploreShelves, RecordSearchClick } from '@go/explore/service.js';
 import { GetFilePathsByAlbums, GetFilePathsByRecordingMBIDs } from '@go/library/library.js';
 import { EventsOn } from '@runtime/runtime';
@@ -253,7 +252,7 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
         srOnly,
         exploreLinkStyles,
         contextMenuStyles,
-        unownedStyles,
+        albumCardStyles,
         css`
             :host {
                 display: block;
@@ -529,21 +528,9 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                 line-height: 1.5;
             }
 
-            /* ── Horizontal scroll rows ── */
-            .horizontal-row {
-                display: flex;
-                gap: 12px;
-                overflow-x: auto;
-                padding-bottom: 4px;
-                scrollbar-width: none;
-            }
-
-            .horizontal-row::-webkit-scrollbar {
-                display: none;
-            }
-
-            /* ── Top result cards ── */
             /* ── Artist cards ── */
+            /* Fixed width, for the reason the album card is: a range
+               means two cards in one row are different sizes. */
             .artist-card {
                 display: flex;
                 flex-direction: column;
@@ -552,8 +539,8 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                 padding: 10px;
                 border-radius: 8px;
                 cursor: pointer;
-                min-width: 100px;
+                width: 120px;
-                max-width: 120px;
+                box-sizing: border-box;
                 flex-shrink: 0;
                 text-align: center;
                 transition: background 0.15s ease;
@@ -624,115 +611,6 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                 font-size: var(--yj-text-xs);
             }
 
-            /* ── Album cards ── */
-            .album-card {
-                display: flex;
-                flex-direction: column;
-                gap: 6px;
-                padding: 8px;
-                border-radius: 8px;
-                cursor: pointer;
-                min-width: 130px;
-                max-width: 150px;
-                flex-shrink: 0;
-                transition: background 0.15s ease;
-            }
-
-            .album-card:hover {
-                background: var(--yj-bg-overlay, rgba(255, 255, 255, 0.06));
-            }
-
-            .album-card:active {
-                transform: scale(0.97);
-            }
-
-            .album-art-container {
-                width: 100%;
-                aspect-ratio: 1;
-                border-radius: 4px;
-                overflow: hidden;
-                background: linear-gradient(
-                    135deg,
-                    var(--yj-bg-overlay, #404040) 0%,
-                    var(--yj-bg-surface, #282828) 100%
-                );
-                display: flex;
-                align-items: center;
-                justify-content: center;
-                position: relative;
-            }
-
-            .album-art-container img {
-                width: 100%;
-                height: 100%;
-                object-fit: cover;
-                display: block;
-            }
-
-            .album-art-fallback {
-                display: flex;
-                align-items: center;
-                justify-content: center;
-                width: 100%;
-                height: 100%;
-                position: absolute;
-                inset: 0;
-            }
-
-            .album-art-fallback wa-icon {
-                color: var(--yj-text-tertiary, #888);
-                font-size: 24px;
-                opacity: 0.5;
-            }
-
-            .album-title {
-                font-weight: 500;
-                color: var(--yj-text-primary, #fff);
-                font-size: var(--yj-text-sm);
-                white-space: nowrap;
-                overflow: hidden;
-                text-overflow: ellipsis;
-            }
-
-            .album-artist {
-                color: var(--yj-text-tertiary, #888);
-                font-size: var(--yj-text-xs);
-                white-space: nowrap;
-                overflow: hidden;
-                text-overflow: ellipsis;
-            }
-
-            .album-meta {
-                display: flex;
-                align-items: center;
-                justify-content: space-between;
-                gap: 6px;
-                color: var(--yj-text-tertiary, #888);
-                font-size: var(--yj-text-xs);
-                min-height: 20px;
-            }
-
-            .album-meta-text {
-                display: flex;
-                align-items: center;
-                gap: 6px;
-                min-width: 0;
-                overflow: hidden;
-            }
-
-            .album-meta library-status-indicator {
-                flex-shrink: 0;
-                margin-left: auto;
-            }
-
-            .type-badge {
-                background: var(--yj-bg-overlay, rgba(255, 255, 255, 0.08));
-                padding: 1px 6px;
-                border-radius: 3px;
-                font-size: 10px;
-                white-space: nowrap;
-            }
-
             /* ── Track list ── */
             .track-list {
                 display: flex;
@@ -753,7 +631,6 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                 cursor: pointer;
             }
 
-            .album-card:focus-visible,
             .track-item:focus-visible {
                 outline: 2px solid var(--yj-accent-text, #ffd43b);
                 outline-offset: -2px;
@@ -1371,7 +1248,7 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
 
         const entity = target.kind === 'album' ? 'release-group' : 'recording';
 
-        window.open(`https://musicbrainz.org/${entity}/${target.mbid}`, '_blank', 'noopener');
+        openMusicBrainz(`/${entity}/${target.mbid}`);
     }
 
     private renderExploreContextMenu() {
@@ -1662,6 +1539,8 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                 } catch {
                     // No image — leave empty string.
                 }
+
+                return undefined;
             }),
         );
 
@@ -2122,7 +2001,7 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                 ${subtitle
                     ? html`<p class="section-reason">${subtitle}</p>`
                     : nothing}
-                <div class="horizontal-row">
+                <scroll-row>
                     ${artists.map((a) => {
                         const owned = isOwned(a);
                         const name = a.englishName || a.name;
@@ -2171,7 +2050,7 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                             </div>
                         `;
                     })}
-                </div>
+                </scroll-row>
             </section>
         `;
     }
@@ -2187,7 +2066,7 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                 ${subtitle
                     ? html`<p class="section-reason">${subtitle}</p>`
                     : nothing}
-                <div class="horizontal-row">
+                <scroll-row>
                     ${releaseGroups.map((rg) => {
                         const artURL = this.thumbnailCache.get(rg.mbid) || '';
                         const year = extractYear(rg.firstReleaseDate);
@@ -2249,6 +2128,18 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                                     >
                                         <wa-icon name="compact-disc"></wa-icon>
                                     </div>
+                                    <div class="album-card-badge">
+                                        <library-status-indicator
+                                            status=${badge.status}
+                                            owned=${badge.owned}
+                                            expected=${badge.expected}
+                                            entity-type="album"
+                                            label=${rg.title}
+                                            request-mbid=${rg.mbid}
+                                            request-artist=${rg.artistCredit ?? ''}
+                                            size="23"
+                                        ></library-status-indicator>
+                                    </div>
                                 </div>
                                 <div class="album-title" title="${rg.title}">
                                     ${rg.title}
@@ -2256,29 +2147,18 @@ export class ExploreView extends ViewLifecycleMixin(LitElement) implements Conte
                                 <div class="album-artist">${creditLink(creditStore.credits(rg.mbid), rg.artistCredit, rg.artistMbid ?? '')}</div>
                                 <div class="album-meta">
                                     <div class="album-meta-text">
+                                        ${year ? html`<span>${year}</span>` : nothing}
                                         ${rg.primaryType
                                             ? html`<span class="type-badge"
                                                   >${rg.primaryType}</span
                                               >`
                                             : nothing}
-                                        ${year ? html`<span>${year}</span>` : nothing}
                                     </div>
-                                    ${badge.status === 'in-library'
-                                        ? nothing
-                                        : html`<library-status-indicator
-                                              status=${badge.status}
-                                              owned=${badge.owned}
-                                              expected=${badge.expected}
-                                              entity-type="album"
-                                              label=${rg.title}
-                                              request-mbid=${rg.mbid}
-                                              request-artist=${rg.artistCredit ?? ''}
-                                          ></library-status-indicator>`}
                                 </div>
                             </div>
                         `;
                     })}
-                </div>
+                </scroll-row>
             </section>
         `;
     }

frontend/src/components/home-view/home-view.ts

@@ -12,6 +12,7 @@ import { libraryStore } from '@store/library-store';
 import { EventsOn } from '@runtime/runtime';
 import { Events } from '../../events';
 import '@components/page-header/page-header';
+import '../scroll-row/scroll-row.js';
 import { designTokens } from '../../styles/tokens.css';
 import { ViewLifecycleMixin } from '../../utils/view-lifecycle';
 
@@ -99,16 +100,6 @@ export class HomeView extends ViewLifecycleMixin(LitElement) {
                 color: var(--yj-text-tertiary, #888);
             }
 
-            .row {
-                display: grid;
-                grid-auto-flow: column;
-                grid-auto-columns: 160px;
-                gap: 14px;
-                overflow-x: auto;
-                padding-bottom: 6px;
-                scrollbar-width: thin;
-            }
-
             .card {
                 background: none;
                 border: none;
@@ -117,6 +108,8 @@ export class HomeView extends ViewLifecycleMixin(LitElement) {
                 cursor: pointer;
                 color: inherit;
                 display: block;
+                width: 160px;
+                flex-shrink: 0;
             }
 
             .art {
@@ -336,9 +329,9 @@ export class HomeView extends ViewLifecycleMixin(LitElement) {
                     <span class="shelf-title">${shelf.title}</span>
                 </div>
                 <p class="shelf-sub">${shelf.subtitle}</p>
-                <div class="row">
+                <scroll-row>
                     ${(shelf.albums ?? []).map((album) => this.renderCard(album))}
-                </div>
+                </scroll-row>
             </section>
         `;
     }

frontend/src/components/playlist-details/playlist-details.ts

@@ -56,12 +56,9 @@ import {
     createTrackCardDragImage,
     removeDragImage,
 } from '@utils/drag-image';
-import { libraryStore } from '@store/library-store';
 import '@components/playlist-picker/playlist-picker.js';
-import { loadTrackDetails } from '@utils/lazy-track-details.js';
+import { showTrackDetailsForPath, showBatchTrackDetailsForPaths } from '@utils/track-details-opener.js';
-import { tracksByFilePath, tracksForPaths } from '@utils/track-index.js';
 import type { TrackDetails } from '@components/track-details/track-details.js';
-import type { CoverArtUrls } from '@components/track-details/track-details.js';
 import '@components/phantom-resolver/phantom-resolver.js';
 import type { PhantomResolver } from '@components/phantom-resolver/phantom-resolver.js';
 import '@components/duplicate-tracks-dialog/duplicate-tracks-dialog.js';
@@ -758,76 +755,21 @@ export class PlaylistDetails
     }
 
     private async openTrackDetails(filePath: string) {
-        const tracks = libraryStore.getCachedTracks();
+        await showTrackDetailsForPath(
-        const track = tracks
+            () => this.trackDetailsDialog,
-            ? tracksByFilePath(tracks).get(filePath)
+            filePath,
-            : undefined;
-
-        if (!track) return;
-
-        const ready = await loadTrackDetails(
             () => void this.openTrackDetails(filePath),
         );
-
-        if (!ready) return;
-
-        const coverArt = track.CoverArtPath
-            ? {
-                coverArtPath: track.CoverArtPath,
-                coverArtSmall: track.CoverArtSmall,
-                coverArtMedium: track.CoverArtMedium,
-                coverArtLarge: track.CoverArtLarge,
-            }
-            : undefined;
-
-        this.trackDetailsDialog?.show(
-            track,
-            coverArt,
-        );
     }
 
     private async openBatchTrackDetails(
         filePaths: string[],
     ) {
-        const cachedTracks =
+        await showBatchTrackDetailsForPaths(
-            libraryStore.getCachedTracks();
+            () => this.trackDetailsDialog,
-
-        if (!cachedTracks) return;
-
-        const tracks = tracksForPaths(
-            cachedTracks,
             filePaths,
-        );
-
-        if (tracks.length === 0) return;
-
-        const ready = await loadTrackDetails(
             () => void this.openBatchTrackDetails(filePaths),
         );
-
-        if (!ready) return;
-
-        const first = tracks[0]!;
-        const albumNames = new Set(tracks.map((t) => t.Album));
-        let coverArt: CoverArtUrls | null = null;
-        let coverArtMixed = false;
-
-        if (albumNames.size === 1 && first.CoverArtPath) {
-            coverArt = {
-                coverArtPath: first.CoverArtPath,
-                coverArtSmall: first.CoverArtSmall,
-                coverArtMedium: first.CoverArtMedium,
-                coverArtLarge: first.CoverArtLarge,
-            };
-        } else if (albumNames.size > 1) {
-            coverArtMixed = true;
-        }
-
-        this.trackDetailsDialog?.showBatch(
-            tracks,
-            coverArt,
-            coverArtMixed,
-        );
     }
 
     /**

frontend/src/components/queue-panel/queue-panel.ts

@@ -51,12 +51,8 @@ import {
     createTrackCardDragImage,
     removeDragImage,
 } from '@utils/drag-image';
-import { libraryStore } from '@store/library-store';
+import { showTrackDetailsForPath, showBatchTrackDetailsForPaths } from '@utils/track-details-opener.js';
-import type * as library from '@go/library/models.js';
-import { loadTrackDetails } from '@utils/lazy-track-details.js';
-import { tracksByFilePath } from '@utils/track-index.js';
 import type { TrackDetails } from '@components/track-details/track-details.js';
-import type { CoverArtUrls } from '@components/track-details/track-details.js';
 import {
     creditLink,
     trackLink,
@@ -1542,89 +1538,33 @@ export class QueuePanel
     }
 
     private async openTrackDetails(index: number) {
-        const queueTrack =
+        const queueTrack = this.queue.tracks[index];
-            this.queue.tracks[index];
 
         if (!queueTrack) return;
 
-        const tracks =
+        await showTrackDetailsForPath(
-            libraryStore.getCachedTracks();
+            () => this.trackDetailsDialog,
-        const track = tracks
+            queueTrack.filePath,
-            ? tracksByFilePath(tracks).get(
-                queueTrack.filePath,
-            )
-            : undefined;
-
-        if (!track) return;
-
-        const ready = await loadTrackDetails(
             () => void this.openTrackDetails(index),
         );
-
-        if (!ready) return;
-
-        const coverArt = track.CoverArtPath
-            ? {
-                coverArtPath: track.CoverArtPath,
-                coverArtSmall: track.CoverArtSmall,
-                coverArtMedium: track.CoverArtMedium,
-                coverArtLarge: track.CoverArtLarge,
-            }
-            : undefined;
-
-        this.trackDetailsDialog?.show(
-            track,
-            coverArt,
-        );
     }
 
     private async openBatchTrackDetails(
         indices: number[],
     ) {
         const queueTracks = this.queue.tracks;
-        const cachedTracks =
+        const filePaths: string[] = [];
-            libraryStore.getCachedTracks();
 
-        if (!cachedTracks) return;
+        for (const i of indices) {
+            const path = queueTracks[i]?.filePath;
 
-        const byPath = tracksByFilePath(cachedTracks);
+            if (path != null) filePaths.push(path);
-        const tracks = indices
-            .map((i) => queueTracks[i])
-            .filter((qt) => qt != null)
-            .map((qt) => byPath.get(qt.filePath))
-            .filter(
-                (t): t is library.Track =>
-                    t != null,
-            );
-
-        if (tracks.length === 0) return;
-
-        const ready = await loadTrackDetails(
-            () => void this.openBatchTrackDetails(indices),
-        );
-
-        if (!ready) return;
-
-        const first = tracks[0]!;
-        const albumNames = new Set(tracks.map((t) => t.Album));
-        let coverArt: CoverArtUrls | null = null;
-        let coverArtMixed = false;
-
-        if (albumNames.size === 1 && first.CoverArtPath) {
-            coverArt = {
-                coverArtPath: first.CoverArtPath,
-                coverArtSmall: first.CoverArtSmall,
-                coverArtMedium: first.CoverArtMedium,
-                coverArtLarge: first.CoverArtLarge,
-            };
-        } else if (albumNames.size > 1) {
-            coverArtMixed = true;
         }
 
-        this.trackDetailsDialog?.showBatch(
+        await showBatchTrackDetailsForPaths(
-            tracks,
+            () => this.trackDetailsDialog,
-            coverArt,
+            filePaths,
-            coverArtMixed,
+            () => void this.openBatchTrackDetails(indices),
         );
     }
 

frontend/src/components/scroll-row/scroll-row.ts

@@ -0,0 +1,213 @@
+import { LitElement, css, html } from 'lit';
+import { customElement, query, state } from 'lit/decorators.js';
+import '@awesome.me/webawesome/dist/components/icon/icon.js';
+
+/** How far one press moves the row — most of a screenful, not all of
+ *  it, so the card that was at the edge stays as an anchor. */
+const SCROLL_FRACTION = 0.8;
+
+/**
+ * A horizontally scrolling row with arrow buttons.
+ *
+ * The shelves, the search results and (now) the artist page's
+ * discography and similar-artists rows are all "more than fits, scroll
+ * sideways". Until this existed the only way to see the rest was a
+ * mousewheel or a trackpad gesture, which is not an affordance — a
+ * mouse with no horizontal wheel simply could not reach the cards past
+ * the fold.
+ *
+ * It is a component rather than a rule on `.horizontal-row` for two
+ * reasons. The arrows are *state* — which way the row can still move —
+ * and that state has to be recomputed when the viewport resizes or a
+ * card arrives with its cover art; a stylesheet cannot do that. And
+ * every caller then gets the same arrows, the same reveal and the same
+ * keyboard labels without writing them again.
+ *
+ * **The arrows are `hidden`, not merely transparent, at the end they
+ * cannot move from** — a control that cannot act is worse than none,
+ * and an invisible one still holds a hit area and a tab stop. On a
+ * pointer device the pair fades in with the row's hover; where there is
+ * no hover they are always visible, because there is no other route to
+ * them there (a swipe is not an affordance a mouse-less keyboard user
+ * has either).
+ *
+ * The cards are light DOM children and stay in the *host's* shadow
+ * root, so the host's own `.album-card` / `.artist-card` styles apply
+ * unchanged — this component only owns the box they scroll inside.
+ */
+@customElement('scroll-row')
+export class ScrollRow extends LitElement {
+    @query('.viewport') private viewport?: HTMLElement;
+
+    @state() private atStart = true;
+
+    @state() private atEnd = true;
+
+    @state() private overflowing = false;
+
+    private observer?: ResizeObserver;
+
+    static override styles = css`
+        :host {
+            display: block;
+            position: relative;
+        }
+
+        .viewport {
+            overflow-x: auto;
+            overflow-y: hidden;
+            scrollbar-width: none;
+            /* A swipe that reaches the row's end should not drag the
+               whole page sideways with it. */
+            overscroll-behavior-x: contain;
+        }
+
+        .viewport::-webkit-scrollbar {
+            display: none;
+        }
+
+        .track {
+            display: flex;
+            gap: 12px;
+        }
+
+        .arrow {
+            position: absolute;
+            top: 50%;
+            transform: translateY(-50%);
+            z-index: 2;
+            display: flex;
+            align-items: center;
+            justify-content: center;
+            width: 36px;
+            height: 36px;
+            padding: 0;
+            border-radius: 50%;
+            border: 1px solid var(--yj-border-subtle, rgba(255, 255, 255, 0.1));
+            background: var(--yj-bg-elevated, #343a40);
+            color: var(--yj-text-primary, #fff);
+            cursor: pointer;
+            opacity: 0;
+            transition: opacity 0.15s ease;
+        }
+
+        .arrow[hidden] {
+            display: none;
+        }
+
+        .arrow.prev {
+            left: 4px;
+        }
+
+        .arrow.next {
+            right: 4px;
+        }
+
+        .arrow:hover {
+            background: var(--yj-bg-overlay, rgba(255, 255, 255, 0.12));
+        }
+
+        .arrow:focus-visible {
+            outline: 2px solid var(--yj-accent, #ffd43b);
+            outline-offset: 2px;
+        }
+
+        @media (hover: hover) and (pointer: fine) {
+            :host(:hover) .arrow,
+            .arrow:focus-visible {
+                opacity: 1;
+            }
+        }
+
+        @media not all and (hover: hover) {
+            .arrow {
+                opacity: 1;
+            }
+        }
+    `;
+
+    override firstUpdated(): void {
+        const viewport = this.viewport;
+
+        if (!viewport) return;
+
+        this.observer = new ResizeObserver(() => this.measure());
+
+        this.observer.observe(viewport);
+
+        // The track's own size is what changes when a card arrives with
+        // its cover art, and a ResizeObserver on the viewport alone
+        // never fires for that.
+        const track = viewport.firstElementChild;
+
+        if (track) this.observer.observe(track);
+
+        this.measure();
+    }
+
+    override disconnectedCallback(): void {
+        super.disconnectedCallback();
+        this.observer?.disconnect();
+        this.observer = undefined;
+    }
+
+    private measure(): void {
+        const viewport = this.viewport;
+
+        if (!viewport) return;
+
+        this.overflowing = viewport.scrollWidth > viewport.clientWidth + 1;
+        this.atStart = viewport.scrollLeft <= 1;
+        this.atEnd =
+            viewport.scrollLeft + viewport.clientWidth >=
+            viewport.scrollWidth - 1;
+    }
+
+    private onScroll = (): void => this.measure();
+
+    private scrollStep(direction: -1 | 1): void {
+        const viewport = this.viewport;
+
+        if (!viewport) return;
+
+        viewport.scrollBy({
+            left: direction * viewport.clientWidth * SCROLL_FRACTION,
+            behavior: 'smooth',
+        });
+    }
+
+    override render() {
+        const showPrev = this.overflowing && !this.atStart;
+        const showNext = this.overflowing && !this.atEnd;
+
+        return html`
+            <button
+                class="arrow prev"
+                type="button"
+                aria-label="Scroll left"
+                ?hidden=${!showPrev}
+                @click=${() => this.scrollStep(-1)}
+            >
+                <wa-icon name="chevron-left"></wa-icon>
+            </button>
+            <div class="viewport" @scroll=${this.onScroll}>
+                <div class="track"><slot></slot></div>
+            </div>
+            <button
+                class="arrow next"
+                type="button"
+                aria-label="Scroll right"
+                ?hidden=${!showNext}
+                @click=${() => this.scrollStep(1)}
+            >
+                <wa-icon name="chevron-right"></wa-icon>
+            </button>
+        `;
+    }
+}
+
+declare global {
+    interface HTMLElementTagNameMap {
+        'scroll-row': ScrollRow;
+    }
+}

frontend/src/components/sidebar/app-sidebar.ts

@@ -6,6 +6,7 @@ import { designTokens } from '../../styles/tokens.css';
 import type { DragActiveDetail } from '@utils/drag-controller';
 import { ActiveViewController } from '@store/controllers/active-view-controller';
 import { ViewVisibilityController } from '@store/controllers/view-visibility-controller';
+import { libraryStore } from '@store/library-store';
 import { VIEW_META } from '../../services/view-meta';
 import type { View } from '../../services/view-meta';
 
@@ -352,6 +353,10 @@ export class AppSidebar extends LitElement {
                     : 'false'}
                                 @click=${() =>
                     this.navigate(item.id)}
+                                @mouseenter=${() =>
+                    this.prefetch(item.id)}
+                                @focus=${() =>
+                    this.prefetch(item.id)}
                                 @dragover=${(e: DragEvent) =>
                     this.onNavDragOver(
                         e,
@@ -503,6 +508,19 @@ export class AppSidebar extends LitElement {
         }
     }
 
+    /**
+     * Start loading what this view draws, on hover or keyboard focus.
+     *
+     * The ~100 ms before the click is the whole point: #280 stopped
+     * fetching every collection at startup, and this is what keeps the
+     * view that *is* opened from paying the whole payload after the
+     * click. Nothing is awaited and nothing is reported here — the view
+     * itself reports a failure, and this is the same request.
+     */
+    private prefetch(view: View) {
+        libraryStore.prefetch(view);
+    }
+
     private navigate(view: View) {
         // No optimistic highlight: the shell answers, and it answers
         // synchronously in `handleNavigate` before it awaits anything.

frontend/src/components/smart-playlist-details/smart-playlist-details.ts

@@ -52,11 +52,8 @@ import '@lit-labs/virtualizer';
 import type { LitVirtualizer } from '@lit-labs/virtualizer';
 import { flow } from '@lit-labs/virtualizer/layouts/flow.js';
 import '@components/playlist-picker/playlist-picker.js';
-import { loadTrackDetails } from '@utils/lazy-track-details.js';
+import { showTrackDetailsForPath, showBatchTrackDetailsForPaths } from '@utils/track-details-opener.js';
-import { tracksByFilePath, tracksForPaths } from '@utils/track-index.js';
 import type { TrackDetails } from '@components/track-details/track-details.js';
-import type { CoverArtUrls } from '@components/track-details/track-details.js';
-import { libraryStore } from '@store/library-store';
 import { formatMilliseconds } from '@utils/time';
 import {
     creditLink,
@@ -1145,76 +1142,21 @@ export class SmartPlaylistDetails
     }
 
     private async openTrackDetails(filePath: string) {
-        const tracks = libraryStore.getCachedTracks();
+        await showTrackDetailsForPath(
-        const track = tracks
+            () => this.trackDetailsDialog,
-            ? tracksByFilePath(tracks).get(filePath)
+            filePath,
-            : undefined;
-
-        if (!track) return;
-
-        const ready = await loadTrackDetails(
             () => void this.openTrackDetails(filePath),
         );
-
-        if (!ready) return;
-
-        const coverArt = track.CoverArtPath
-            ? {
-                coverArtPath: track.CoverArtPath,
-                coverArtSmall: track.CoverArtSmall,
-                coverArtMedium: track.CoverArtMedium,
-                coverArtLarge: track.CoverArtLarge,
-            }
-            : undefined;
-
-        this.trackDetailsDialog?.show(
-            track,
-            coverArt,
-        );
     }
 
     private async openBatchTrackDetails(
         filePaths: string[],
     ) {
-        const cachedTracks =
+        await showBatchTrackDetailsForPaths(
-            libraryStore.getCachedTracks();
+            () => this.trackDetailsDialog,
-
-        if (!cachedTracks) return;
-
-        const tracks = tracksForPaths(
-            cachedTracks,
             filePaths,
-        );
-
-        if (tracks.length === 0) return;
-
-        const ready = await loadTrackDetails(
             () => void this.openBatchTrackDetails(filePaths),
         );
-
-        if (!ready) return;
-
-        const first = tracks[0]!;
-        const albumNames = new Set(tracks.map((t) => t.Album));
-        let coverArt: CoverArtUrls | null = null;
-        let coverArtMixed = false;
-
-        if (albumNames.size === 1 && first.CoverArtPath) {
-            coverArt = {
-                coverArtPath: first.CoverArtPath,
-                coverArtSmall: first.CoverArtSmall,
-                coverArtMedium: first.CoverArtMedium,
-                coverArtLarge: first.CoverArtLarge,
-            };
-        } else if (albumNames.size > 1) {
-            coverArtMixed = true;
-        }
-
-        this.trackDetailsDialog?.showBatch(
-            tracks,
-            coverArt,
-            coverArtMixed,
-        );
     }
 
     // =================================================================

frontend/src/components/smart-playlist-editor/smart-playlist-editor.ts

@@ -1,8 +1,12 @@
 import { LitElement, html, css, nothing } from 'lit';
 import { customElement, property, state } from 'lit/decorators.js';
 import * as library from '@go/library/models.js';
-import { PreviewSmartPlaylist } from '@go/playlist/service.js';
+import {
-import { libraryStore } from '@store/library-store';
+    PreviewSmartPlaylist,
+    SuggestSmartPlaylistValues,
+} from '@go/playlist/service.js';
+import { list } from '@utils/binding';
+import { LRUMap } from '@utils/lru-map';
 import { describeError } from '@utils/describe-error';
 import { designTokens } from '../../styles/tokens.css';
 import '@components/combobox/combobox.ts';
@@ -91,51 +95,23 @@ function formatOperatorLabel(op: string): string {
     return op.replace(/_/g, ' ');
 }
 
-/** Returns autocomplete suggestions for a given field from libraryStore. */
+/**
-function getAutocompleteOptions(field: string): string[] {
+ * Fields whose value box suggests values present in the library. Must
-    switch (field) {
+ * match `suggestFields` in backend/smartplaylist; any other field gets
-        case 'artist':
+ * a plain box.
-            return libraryStore.getCachedArtists()?.map((a) => a.Name) ?? [];
+ *
-        case 'genre':
+ * Suggestions are asked for as the user types (#279): they used to be
-            return libraryStore.getCachedGenres()?.map((g) => g.Name) ?? [];
+ * built from libraryStore's whole-library arrays, which made this
-        case 'album':
+ * editor one more reason to load every track at startup, and gave it
-            return libraryStore.getCachedAlbums()?.map((a) => a.Name) ?? [];
+ * empty lists whenever those arrays had not landed.
-        case 'title': {
+ */
-            const tracks = libraryStore.getCachedTracks();
+const SUGGEST_FIELDS = new Set([
-            if (!tracks) return [];
+    'title', 'artist', 'album', 'genre', 'composer', 'file_type',
-            return [...new Set(tracks.map((t) => t.TrackName).filter(Boolean))];
+    'year', 'release_year',
-        }
+]);
-        case 'composer': {
+
-            const tracks = libraryStore.getCachedTracks();
+/** How long typing must pause before suggestions are asked for. */
-            if (!tracks) return [];
+const SUGGEST_DEBOUNCE_MS = 120;
-            return [...new Set(tracks.map((t) => t.Composer).filter(Boolean))];
-        }
-        case 'file_type': {
-            const tracks = libraryStore.getCachedTracks();
-            if (!tracks) return [];
-            return [...new Set(tracks.map((t) => t.FileType).filter(Boolean))];
-        }
-        case 'year':
-        case 'release_year': {
-            // Both year fields draw suggestions from the set of years
-            // present in the library. The cached Track only carries the
-            // display (original) year, so it seeds both datalists — the
-            // list is just a hint, and the real filter runs server-side.
-            const tracks = libraryStore.getCachedTracks();
-            if (!tracks) return [];
-            return [
-                ...new Set(
-                    tracks
-                        .map((t) => t.Year)
-                        .filter((y) => y > 0)
-                        .map(String),
-                ),
-            ].sort();
-        }
-        default:
-            return [];
-    }
-}
 
 /**
  * Overrides for fields whose title-cased name would be ambiguous. The
@@ -206,6 +182,17 @@ export class SmartPlaylistEditor extends LitElement {
 
     private previewTimer: ReturnType<typeof setTimeout> | null = null;
 
+    /** The value suggestions each rule row is showing, by row index. */
+    @state() private suggestions = new Map<number, readonly string[]>();
+
+    private suggestTimer: ReturnType<typeof setTimeout> | null = null;
+
+    /** Answers already fetched this session, by field and typed text. */
+    private suggestCache = new LRUMap<string, readonly string[]>(100);
+
+    /** The latest request per row, so a slow answer cannot overwrite a newer one. */
+    private suggestWanted = new Map<number, string>();
+
     // ── Styles ──────────────────────────────────────────────────────
 
     static override styles = [
@@ -599,6 +586,7 @@ export class SmartPlaylistEditor extends LitElement {
         // Reset value when field changes to avoid stale autocomplete data
         row.value = '';
         row.value2 = '';
+        this.dropSuggestions();
 
         this.ruleRows = [...this.ruleRows];
         this.onRulesChanged();
@@ -628,6 +616,56 @@ export class SmartPlaylistEditor extends LitElement {
         this.onRulesChanged();
     }
 
+    /** Ask for the values of row `index`'s field that contain `text`. */
+    private requestSuggestions(index: number, text: string) {
+        const field = this.ruleRows[index]?.field ?? '';
+
+        if (!SUGGEST_FIELDS.has(field)) return;
+
+        const key = `${field}\u0000${text}`;
+
+        this.suggestWanted.set(index, key);
+
+        const cached = this.suggestCache.get(key);
+
+        if (cached) {
+            this.setSuggestions(index, cached);
+
+            return;
+        }
+
+        if (this.suggestTimer !== null) clearTimeout(this.suggestTimer);
+
+        this.suggestTimer = setTimeout(() => {
+            this.suggestTimer = null;
+            void list(SuggestSmartPlaylistValues(field, text))
+                .then((values) => {
+                    this.suggestCache.set(key, values);
+
+                    if (this.suggestWanted.get(index) === key) {
+                        this.setSuggestions(index, values);
+                    }
+                })
+                .catch((err: unknown) => {
+                    // A suggestion is a hint; the box still takes any text.
+                    console.error('smart playlist: suggestions failed', err);
+                });
+        }, SUGGEST_DEBOUNCE_MS);
+    }
+
+    private setSuggestions(index: number, values: readonly string[]) {
+        const next = new Map(this.suggestions);
+
+        next.set(index, values);
+        this.suggestions = next;
+    }
+
+    /** Row indexes and fields changed: what was suggested no longer applies. */
+    private dropSuggestions() {
+        this.suggestions = new Map();
+        this.suggestWanted.clear();
+    }
+
     private updateValue2(index: number, newValue: string) {
         const row = this.ruleRows[index];
         if (!row) return;
@@ -644,6 +682,7 @@ export class SmartPlaylistEditor extends LitElement {
     private removeRule(index: number) {
         if (this.ruleRows.length <= 1) return;
         this.ruleRows = this.ruleRows.filter((_, i) => i !== index);
+        this.dropSuggestions();
         this.onRulesChanged();
     }
 
@@ -892,7 +931,9 @@ export class SmartPlaylistEditor extends LitElement {
                         `
                       : html`
                             <yj-combobox
-                                .options=${getAutocompleteOptions(row.field)}
+                                .options=${this.suggestions.get(index) ?? []}
+                                @combobox-input=${(e: CustomEvent<{ text: string }>) =>
+                                    this.requestSuggestions(index, e.detail.text)}
                                 .value=${row.value}
                                 placeholder=${isAnyOf
                                     ? 'Comma-separated values'

frontend/src/components/top-results-row/top-results-row.ts

@@ -1,6 +1,7 @@
 import { LitElement, html, css, nothing } from 'lit';
 import { customElement, property } from 'lit/decorators.js';
 import { designTokens } from '../../styles/tokens.css';
+import '../scroll-row/scroll-row.js';
 import type * as explore from '@go/explore/models.js';
 import {
     GetArtistImageURL,
@@ -15,7 +16,6 @@ import { albumBadgeFor, libraryStatusFor } from '../../utils/library-status';
 import {
     isOwned,
     ownershipLabel,
-    unownedStyles,
     type OwnableKind,
 } from '../../utils/ownership';
 import { completenessStore } from '../../store/completeness-store';
@@ -103,20 +103,12 @@ export class TopResultsRow extends LitElement {
     static override styles = [
         designTokens,
         exploreLinkStyles,
-        unownedStyles,
         css`
             :host {
                 display: block;
                 margin-bottom: 16px;
             }
 
-            .row {
-                display: flex;
-                gap: 12px;
-                overflow-x: auto;
-                padding-bottom: 4px;
-            }
-
             .card {
                 flex: 0 0 auto;
                 width: 200px;
@@ -285,9 +277,9 @@ export class TopResultsRow extends LitElement {
 
         return html`
             <div class="section-label">Top Results</div>
-            <div class="row">
+            <scroll-row>
                 ${this.results.map((r) => this.renderCard(r))}
-            </div>
+            </scroll-row>
         `;
     }
 

frontend/src/components/track-details/track-details.ts

@@ -22,7 +22,9 @@ import {
 import { GetTrackMBIDs } from '@go/library/library.js';
 type TrackMBIDs = library.TrackMBIDs;
 import { ImageFilePicker, ReadFile } from '@go/frontendutil/frontendutil.js';
-import { libraryStore } from '../../store/library-store';
+import { trackCache } from '../../store/track-cache';
+import { batchCoverArt } from '@utils/track-details-opener.js';
+import type { ListTrack } from '@utils/track-table';
 import { EventsOn } from '@runtime/runtime';
 import { Events } from '../../events';
 
@@ -87,7 +89,11 @@ export class TrackDetails extends LitElement {
 
     // -- Batch-specific state --
     @state() private batchMode = false;
-    @state() private batchTracks: library.Track[] = [];
+    // `ListTrack`, not `Track`: every field the merged-values view reads
+    // is on the list's rows, so a caller that is already showing them
+    // can open this dialog without fetching anything (#281). The
+    // openers that hold no rows ask `trackCache` instead.
+    @state() private batchTracks: ListTrack[] = [];
     @state() private batchFilePaths: string[] = [];
     @state() private batchCoverArtMixed = false;
     @state() private batchProgress: {
@@ -135,12 +141,12 @@ export class TrackDetails extends LitElement {
 
     /** Open the dialog for batch editing multiple tracks. */
     showBatch(
-        tracks: library.Track[],
+        tracks: readonly ListTrack[],
         coverArt: CoverArtUrls | null,
         coverArtMixed: boolean,
     ): void {
         this.batchMode = true;
-        this.batchTracks = tracks;
+        this.batchTracks = [...tracks];
         this.batchFilePaths = tracks.map(
             (t) => t.FilePath,
         );
@@ -1317,10 +1323,13 @@ export class TrackDetails extends LitElement {
         const container = img.parentElement;
 
         if (container) {
-            container.innerHTML =
+            const placeholder = document.createElement('div');
-                '<div class="cover-placeholder">' +
+            const icon = document.createElement('wa-icon');
-                '<wa-icon name="music"></wa-icon>' +
+
-                '</div>';
+            placeholder.className = 'cover-placeholder';
+            icon.setAttribute('name', 'music');
+            placeholder.append(icon);
+            container.replaceChildren(placeholder);
         }
     };
 
@@ -1690,20 +1699,11 @@ export class TrackDetails extends LitElement {
             // invalidation, which refreshes all other views.
             this.exitEditMode();
 
-            // Re-fetch track and album data so the dialog
+            // Re-read this one track so the dialog shows the
-            // shows updated values and cover art.  The store
+            // values and cover art just written. Not the whole
-            // invalidation is already in-flight from the event;
+            // library (#279): the views that hold it refetch on
-            // these calls await the pending fetch or start one.
+            // the event, and only if something is showing them.
-            // Awaited for the side effect of refreshing the
+            const [updated] = await trackCache.refresh([filePath]);
-            // store; the album list is consumed elsewhere.
-            const [tracks] = await Promise.all([
-                libraryStore.getTracks(),
-                libraryStore.getAlbums(),
-            ]);
-
-            const updated = tracks.find(
-                (t) => t.FilePath === filePath,
-            );
 
             if (updated) {
                 this.track = updated;
@@ -1828,39 +1828,18 @@ export class TrackDetails extends LitElement {
         this.errorMessage = '';
         this.cleanupPendingCoverArt();
 
-        // Refresh data from library store; album list is
+        // Re-read the tracks just written, in the order the batch
-        // refreshed for side effects only.
+        // holds them (#279) — not the whole library to filter.
-        const [tracks] = await Promise.all([
+        // `refresh`, because the write's event may not have reached
-            libraryStore.getTracks(),
+        // the cache before its own result did.
-            libraryStore.getAlbums(),
+        const refreshed = await trackCache.refresh(this.batchFilePaths);
-        ]);
 
-        // Re-resolve batch tracks.
-        const pathSet = new Set(this.batchFilePaths);
-        const refreshed = tracks.filter((t) =>
-            pathSet.has(t.FilePath),
-        );
         this.batchTracks = refreshed;
 
-        // Re-resolve cover art state.
+        const { coverArt, mixed } = batchCoverArt(refreshed);
-        const first = refreshed[0];
-        const albumNames = new Set(refreshed.map((t) => t.Album));
 
-        if (albumNames.size === 1 && first?.CoverArtPath) {
+        this.coverArt = coverArt;
-            this.coverArt = {
+        this.batchCoverArtMixed = mixed;
-                coverArtPath: first.CoverArtPath,
-                coverArtSmall: first.CoverArtSmall,
-                coverArtMedium: first.CoverArtMedium,
-                coverArtLarge: first.CoverArtLarge,
-            };
-            this.batchCoverArtMixed = false;
-        } else if (albumNames.size > 1) {
-            this.coverArt = null;
-            this.batchCoverArtMixed = true;
-        } else {
-            this.coverArt = null;
-            this.batchCoverArtMixed = false;
-        }
     };
 
     // -- Shared edit logic --
@@ -2103,6 +2082,8 @@ export class TrackDetails extends LitElement {
             // as a base64-encoded string (standard encoding/json
             // behaviour for []byte).
             const result = await ReadFile(filePath);
+            // SAFETY: the binding is typed as the Go []byte, but the
+            // wire value is the base64 string encoding/json made of it.
             const b64 = result as unknown as string;
             const binary = atob(b64);
             const bytes = new Uint8Array(binary.length);
@@ -2157,7 +2138,7 @@ export class TrackDetails extends LitElement {
             key: string;
             label: string;
             type: 'text' | 'number';
-            extract: (t: library.Track) => string;
+            extract: (t: ListTrack) => string;
         }> = [
             {
                 key: 'title',
@@ -2241,7 +2222,7 @@ export class TrackDetails extends LitElement {
     private countDistinctValues(key: string): number {
         const extractMap: Record<
             string,
-            (t: library.Track) => string
+            (t: ListTrack) => string
         > = {
             title: (t) => t.TrackName ?? '',
             artist: (t) => t.ArtistName ?? '',
@@ -2265,7 +2246,7 @@ export class TrackDetails extends LitElement {
         if (!extract) return 0;
 
         const unique = new Set(
-            this.batchTracks.map(extract),
+            this.batchTracks.map((t) => extract(t)),
         );
 
         return unique.size;

frontend/src/components/track-list/columns.ts

@@ -1,4 +1,4 @@
-import type * as library from '@go/library/models.js';
+import type { ListTrack } from '@utils/track-table';
 import {
     formatSampleRate,
     formatBitDepth,
@@ -45,7 +45,7 @@ export interface ColumnDef {
      */
     configurable?: boolean;
     /** Extracts the display value from a track. */
-    accessor: (track: library.Track) => string;
+    accessor: (track: ListTrack) => string;
     /** Default CSS width (used when no saved width exists). */
     defaultWidth: string;
     /** Text alignment. Defaults to left. */
@@ -60,15 +60,15 @@ export interface ColumnDef {
      * needs it, which is why it is optional rather than a second
      * required parameter on all of them.
      */
-    renderCell?: (track: library.Track, term?: string) => unknown;
+    renderCell?: (track: ListTrack, term?: string) => unknown;
     /**
      * Comparison function for sorting two tracks by this column.
      * Returns negative if a < b, positive if a > b, zero if equal.
      * If omitted the column is not sortable.
      */
     comparator?: (
-        a: library.Track,
+        a: ListTrack,
-        b: library.Track,
+        b: ListTrack,
     ) => number;
 }
 
@@ -79,7 +79,7 @@ export const COLUMN_DEFS: Record<string, ColumnDef> = {
         label: 'Art',
         accessor: () => '',
         defaultWidth: '36px',
-        renderCell: (track: library.Track) => {
+        renderCell: (track: ListTrack) => {
             // `perf.M3`. This rendered `CoverArtPath` — the *original*
             // embedded artwork, commonly 1500×1500 and several hundred
             // kB — scaled by CSS into a 24 px box, while the 100 px
@@ -90,10 +90,10 @@ export const COLUMN_DEFS: Record<string, ColumnDef> = {
             // `cover-grid.getCoverUrl()` has picked the right tier all
             // along; this is the same rule for a much smaller box, with
             // the two attributes that keep the decode off the scroll
-            // path.
+            // path. The list carries only this tier (#281): every tier
-            const src = track.CoverArtSmall
+            // is derived from the same file, so it is set whenever any
-                || track.CoverArtMedium
+            // of them would be.
-                || track.CoverArtPath;
+            const src = track.CoverArtSmall;
 
             if (!src) return nothing;
 

frontend/src/components/track-list/search-ranking.ts

@@ -1,4 +1,4 @@
-import type * as library from '@go/library/models.js';
+import type { ListTrack } from '@utils/track-table';
 import { html } from 'lit';
 import type { TemplateResult } from 'lit';
 
@@ -99,7 +99,7 @@ function matchQuality(
  *                   fields are always included on top of these.
  */
 function scoreTrack(
-    track: library.Track,
+    track: ListTrack,
     termLower: string,
     columns: ColumnDef[],
 ): number {
@@ -147,7 +147,7 @@ function scoreTrack(
 
 /** A track paired with its relevance score. */
 export interface RankedTrack {
-    track: library.Track;
+    track: ListTrack;
     score: number;
 }
 
@@ -166,10 +166,10 @@ export interface RankedTrack {
  *          `scores` (Map of FilePath → relevance score).
  */
 export function rankTracks(
-    tracks: library.Track[],
+    tracks: ListTrack[],
     term: string,
     activeColumns: ColumnDef[],
-): { tracks: library.Track[]; scores: Map<string, number> } {
+): { tracks: ListTrack[]; scores: Map<string, number> } {
     const termLower = term.toLowerCase();
     const ranked: RankedTrack[] = [];
 
@@ -188,7 +188,7 @@ export function rankTracks(
     // Sort descending by score (highest relevance first).
     ranked.sort((a, b) => b.score - a.score);
 
-    const result: library.Track[] = [];
+    const result: ListTrack[] = [];
     const scores = new Map<string, number>();
 
     for (const r of ranked) {

frontend/src/components/track-list/track-list.ts

@@ -1,5 +1,5 @@
-import * as library from '@go/library/models.js';
+import type { ListTrack } from '@utils/track-table';
-import { LitElement, html, svg, css, nothing } from 'lit';
+import { LitElement, html, svg, css, nothing, type TemplateResult } from 'lit';
 import { designTokens } from '../../styles/tokens.css';
 import { srOnly } from '../../styles/sr-only.css';
 import {
@@ -80,11 +80,10 @@ import { describeError } from '@utils/describe-error';
 import { notificationStore } from '@store/notification-store';
 import { confirmAction } from '@components/confirm-dialog/confirm-dialog';
 import { RemoveFromLibrary } from '@go/library/library.js';
-import { loadTrackDetails } from '@utils/lazy-track-details.js';
+import { showTrackDetailsForPath, showBatchTrackDetails } from '@utils/track-details-opener.js';
 import { tracksByFilePath, tracksForPaths } from '@utils/track-index.js';
 import '@components/playlist-picker/playlist-picker.js';
 import type { TrackDetails } from '@components/track-details/track-details.js';
-import type { CoverArtUrls } from '@components/track-details/track-details.js';
 import {
     ICON_PLAY,
     ICON_PLAYLIST,
@@ -155,7 +154,7 @@ export class TrackList
      * parent is responsible for reloading when data changes.
      */
     @property({ type: Array, attribute: false })
-    externalTracks?: library.Track[];
+    externalTracks?: ListTrack[];
 
     /**
      * What a host embedding this list (e.g. `genre-details`) should say
@@ -199,7 +198,7 @@ export class TrackList
     private lastSearchTerm = '';
 
     /** Tracks the store's cached array reference to detect refreshes. */
-    private lastTracksRef: library.Track[] | null =
+    private lastTracksRef: ListTrack[] | null =
         null;
 
     /**
@@ -242,7 +241,7 @@ export class TrackList
     }
 
     @state()
-    private tracks: library.Track[] = [];
+    private tracks: ListTrack[] = [];
 
     @query('#context-menu')
     private contextMenuPopup!: MenuSurface;
@@ -269,16 +268,16 @@ export class TrackList
     private lastActiveTrackPath: string | null = null;
 
     // -- Memoisation caches for filtered / sorted tracks --
-    private cachedFilteredTracks: library.Track[] = [];
+    private cachedFilteredTracks: ListTrack[] = [];
-    private cachedSortedTracks: library.Track[] = [];
+    private cachedSortedTracks: ListTrack[] = [];
     private cachedRelevanceScores = new Map<
         string,
         number
     >();
-    private prevFilterTracks: library.Track[] = [];
+    private prevFilterTracks: ListTrack[] = [];
     private prevFilterTerm = '';
     private prevFilterColIds = '';
-    private prevSortFiltered: library.Track[] = [];
+    private prevSortFiltered: ListTrack[] = [];
     private prevSortField: string | null = null;
     private prevSortDir: SortDirection = 'asc';
 
@@ -523,7 +522,7 @@ export class TrackList
         }
     }
 
-    private computeFilteredTracks(): library.Track[] {
+    private computeFilteredTracks(): ListTrack[] {
         const term = this.searchCtrl.term;
 
         if (!term) {
@@ -543,7 +542,7 @@ export class TrackList
         return result.tracks;
     }
 
-    private computeSortedTracks(): library.Track[] {
+    private computeSortedTracks(): ListTrack[] {
         const tracks = this.cachedFilteredTracks;
         const hasSearch =
             this.cachedRelevanceScores.size > 0;
@@ -1337,11 +1336,6 @@ export class TrackList
         super.connectedCallback();
         this.restoreSortPreferences();
 
-        if (this.externalTracks) {
-            this.tracks = this.externalTracks;
-        } else {
-            this.loadTracks();
-        }
         this.resizeObserver = new ResizeObserver(
             () => {
                 this.onHostResize();
@@ -1391,10 +1385,33 @@ export class TrackList
         this.resizeObserver = null;
     }
 
+    /**
+     * Fetch the list when this becomes the view on screen (#280).
+     *
+     * Not on connection: `index.html` renders a `<track-list>` as the
+     * main panel's first-paint content, so a connection-time fetch was
+     * the whole library loaded at launch for a landing on Home — 12 MB
+     * at 50 000 tracks, and the backend's peak RSS with it. The shell
+     * activates this element only when a navigation lands on Tracks.
+     *
+     * Called on *every* activation, not just the first: the store may
+     * have refetched while this view was off screen, and `getTracks()`
+     * answers from its cache when nothing changed.
+     */
+    protected override onViewActivate(): void {
+        if (this.externalTracks) {
+            this.tracks = this.externalTracks;
+        } else {
+            void this.loadTracks();
+        }
+
+        this.attachListListeners();
+    }
+
     /** Document-level listeners belong to the *visible* list.  A cached
      *  list is never disconnected, so this is the only place they can be
      *  taken down again. */
-    protected override onViewActivate(): void {
+    private attachListListeners(): void {
         this.listenWhileActive(document, 'click', this.clearSelectionHandler);
         this.listenWhileActive(
             document,
@@ -1561,9 +1578,10 @@ export class TrackList
             this.selection.clear();
         }
 
-        // Re-fetch when the store delivers fresh
+        // Re-fetch when the store delivers fresh data after an
-        // data after eager refetch on invalidation.
+        // invalidation. Off screen the list does nothing with it, and
-        if (!this.externalTracks) {
+        // the next activation re-reads the store (#280).
+        if (!this.externalTracks && this.viewActive) {
             const cached =
                 this.libraryCtrl.cachedTracks;
 
@@ -1734,7 +1752,7 @@ export class TrackList
      */
     private resolveTrackFromEvent(
         e: Event,
-    ): { track: library.Track; index: number } | null {
+    ): { track: ListTrack; index: number } | null {
         const row = (e.target as HTMLElement).closest(
             '.track-row',
         ) as HTMLElement | null;
@@ -1875,7 +1893,7 @@ export class TrackList
 
     private onTrackRowClick(
         e: MouseEvent,
-        track: library.Track,
+        track: ListTrack,
         index: number,
     ) {
         // Clicking is also how the keyboard's starting point is chosen:
@@ -1884,7 +1902,7 @@ export class TrackList
         this.selection.handleItemClick(e, track.FilePath, index);
     }
 
-    private onTrackRowDblClick(_track: library.Track, index: number) {
+    private onTrackRowDblClick(_track: ListTrack, index: number) {
         this.selection.clear();
         this.playFromRow(index);
     }
@@ -1925,7 +1943,7 @@ export class TrackList
         );
     }
 
-    private onTrackContextMenu(e: MouseEvent, track: library.Track) {
+    private onTrackContextMenu(e: MouseEvent, track: ListTrack) {
         e.preventDefault();
         e.stopPropagation();
 
@@ -1939,7 +1957,7 @@ export class TrackList
 
     private onTrackDragStart = (
         e: DragEvent,
-        track: library.Track,
+        track: ListTrack,
     ) => {
         // Gather file paths: all selected if this track is selected,
         // otherwise just the dragged track.
@@ -2129,74 +2147,26 @@ export class TrackList
         this.ctxMenu.close();
     }
 
+    // The list's rows do not carry what the dialog shows (#281), so
+    // the dialog gets whole tracks by path, like every other opener.
     private async openTrackDetails(filePath: string) {
-        const track = tracksByFilePath(this.tracks).get(
+        await showTrackDetailsForPath(
+            () => this.trackDetailsDialog,
             filePath,
-        );
-
-        if (!track) return;
-
-        const ready = await loadTrackDetails(
             () => void this.openTrackDetails(filePath),
         );
-
-        if (!ready) return;
-
-        const coverArt = track.CoverArtPath
-            ? {
-                coverArtPath: track.CoverArtPath,
-                coverArtSmall: track.CoverArtSmall,
-                coverArtMedium: track.CoverArtMedium,
-                coverArtLarge: track.CoverArtLarge,
-            }
-            : undefined;
-
-        this.trackDetailsDialog?.show(
-            track,
-            coverArt,
-        );
     }
 
     private async openBatchTrackDetails(
         filePaths: string[],
     ) {
-        const tracks = tracksForPaths(
+        // The rows in hand are what the dialog reads, so a "select all"
-            this.tracks,
+        // on 50 000 tracks opens it without asking the backend for them.
-            filePaths,
+        await showBatchTrackDetails(
-        );
+            () => this.trackDetailsDialog,
-
+            tracksForPaths(this.tracks, filePaths),
-        if (tracks.length === 0) return;
-
-        const ready = await loadTrackDetails(
             () => void this.openBatchTrackDetails(filePaths),
         );
-
-        if (!ready) return;
-
-        // Use cover art from the first track. If all tracks share
-        // the same album, they share the same art.
-        const first = tracks[0]!;
-        let coverArt: CoverArtUrls | null = null;
-        let coverArtMixed = false;
-
-        const albumNames = new Set(tracks.map((t) => t.Album));
-
-        if (albumNames.size === 1 && first.CoverArtPath) {
-            coverArt = {
-                coverArtPath: first.CoverArtPath,
-                coverArtSmall: first.CoverArtSmall,
-                coverArtMedium: first.CoverArtMedium,
-                coverArtLarge: first.CoverArtLarge,
-            };
-        } else if (albumNames.size > 1) {
-            coverArtMixed = true;
-        }
-
-        this.trackDetailsDialog?.showBatch(
-            tracks,
-            coverArt,
-            coverArtMixed,
-        );
     }
 
     // =================================================================
@@ -2274,7 +2244,7 @@ export class TrackList
         this.saveSortPreferences();
     }
 
-    private isActiveTrack(track: library.Track): boolean {
+    private isActiveTrack(track: ListTrack): boolean {
         const currentTrack = this.player.currentTrack;
 
         if (!currentTrack) return false;
@@ -2283,9 +2253,9 @@ export class TrackList
     }
 
     private renderTrackRow = (
-        track: library.Track,
+        track: ListTrack,
         index: number,
-    ): unknown => {
+    ): TemplateResult => {
         const active = this.isActiveTrack(track);
         const selected = this.selection.isSelected(
             track.FilePath,
@@ -2568,7 +2538,7 @@ export class TrackList
                         scroller
                         .items=${visibleTracks}
                         .renderItem=${this.renderTrackRow}
-                        .keyFunction=${(track: library.Track) => track.FilePath}
+                        .keyFunction=${(track: ListTrack) => track.FilePath}
                         .layout=${this.rowLayout}
                       ></lit-virtualizer>
                     `}

frontend/src/icons/names.txt

@@ -31,6 +31,7 @@ solid/bookmark
 solid/box-open
 solid/check
 solid/chevron-down
+solid/chevron-left
 solid/chevron-right
 solid/circle-check
 solid/circle-exclamation

frontend/src/store/controllers/library-controller.ts

@@ -1,6 +1,7 @@
 import type { ReactiveController, ReactiveControllerHost } from 'lit';
 import type * as library from '@go/library/models.js';
 import { libraryStore } from '../library-store';
+import type { ListTrack } from '@utils/track-table';
 
 type ViewName = 'tracks' | 'albums' | 'artists' | 'genres';
 
@@ -55,7 +56,7 @@ export class LibraryController implements ReactiveController {
     // DATA ACCESS
     // ===================================================================
 
-    async getTracks(): Promise<library.Track[]> {
+    async getTracks(): Promise<ListTrack[]> {
         return libraryStore.getTracks();
     }
 
@@ -85,7 +86,7 @@ export class LibraryController implements ReactiveController {
         );
     }
 
-    get cachedTracks(): library.Track[] | null {
+    get cachedTracks(): ListTrack[] | null {
         return libraryStore.getCachedTracks();
     }
 

frontend/src/store/library-store.ts

@@ -1,6 +1,6 @@
 import { EventsOn } from '@runtime/runtime';
 import {
-    GetTracks,
+    GetTrackTable,
     GetAlbums,
     GetArtists,
     GetGenres,
@@ -9,6 +9,8 @@ import {
 } from '@go/library/library.js';
 import type * as library from '@go/library/models.js';
 import { list } from '@utils/binding';
+import { trackCache } from './track-cache';
+import { decodeTrackTable, type ListTrack } from '@utils/track-table';
 import { Events } from '../events';
 
 type ViewName = 'tracks' | 'albums' | 'artists' | 'genres';
@@ -27,8 +29,16 @@ const COVER_SIZE_DEFAULT = 176;
 /** localStorage key for persisted cover size. */
 const COVER_SIZE_KEY = 'cover-grid-size';
 
+/**
+ * How long the small-collection warm-up will wait for idle before
+ * running anyway. It is speculative, but a busy main thread must not
+ * mean Albums is slow to open — the timeout is the promise that it is
+ * only ever deferred, never skipped.
+ */
+const WARM_IDLE_TIMEOUT_MS = 3_000;
+
 class LibraryStore {
-    private tracks: library.Track[] | null = null;
+    private tracks: ListTrack[] | null = null;
     private albums: library.Album[] | null = null;
     private artists: library.Artist[] | null = null;
     private genres: library.GenreWithCount[] | null = null;
@@ -81,8 +91,8 @@ class LibraryStore {
     private cacheGen = 0;
 
     constructor() {
-        EventsOn(Events.LibraryScanComplete, () => {
+        EventsOn(Events.LibraryScanComplete, (payload: unknown) => {
-            this.invalidate();
+            this.applyScanComplete(payload);
         });
         EventsOn(Events.LibraryRemoved, () => {
             this.libraries = null;
@@ -98,8 +108,8 @@ class LibraryStore {
             this.changeGen++;
             this.notify();
         });
-        EventsOn(Events.TrackMetadataChanged, () => {
+        EventsOn(Events.TrackMetadataChanged, (payload: unknown) => {
-            this.invalidate();
+            this.applyMetadataChanged(payload);
         });
         EventsOn(Events.TrackPlayCountChanged, (payload: unknown) => {
             this.applyPlayCount(payload);
@@ -109,34 +119,82 @@ class LibraryStore {
         });
 
         this.loadCoverSize();
-        this.deferEagerFetch();
+        this.warmSmallCollectionsOnIdle();
     }
 
     /**
-     * Schedules eagerFetch() to run after the DOM is ready.
+     * Warm the three small collections once the app is idle after first
-     * The LibraryStore singleton is instantiated during ES module
+     * paint, and deliberately not the tracks (#280).
-     * evaluation (import time), so calling eagerFetch() in the
+     *
-     * constructor would fire 4 backend roundtrips before the app
+     * All four used to be fetched together at `DOMContentLoaded`,
-     * shell has rendered.  Deferring to the 'DOMContentLoaded'
+     * whichever view was showing. On a 26 138-track library the track
-     * event (or calling immediately if the DOM is already parsed)
+     * list was 20.5 MB of that, and encoding it cost the backend ~170 MB
-     * lets the shell paint first, then begins data loading.
+     * of transient allocation — paid by someone looking at Home, which
+     * needs none of it. Measured on 50 000 tracks: 543 MB of backend RSS
+     * at rest before, 296 MB after, and 12.1 MB of binding bytes instead
+     * of 35.9.
+     *
+     * Albums, artists and genres are 1.6 MB together, so they are still
+     * fetched ahead of the click — that is what made those views
+     * instant. Tracks are 12 MB at 50 000 and are fetched by the view
+     * that draws them, or by `prefetch` from a hover.
+     *
+     * Idle rather than immediate: this is speculative, so it must not
+     * compete with the first paint.
      */
-    private deferEagerFetch(): void {
+    private warmSmallCollectionsOnIdle(): void {
-        if (document.readyState === 'loading') {
+        const warm = () => {
-            window.addEventListener(
+            const logged = this.failureReporter();
-                'DOMContentLoaded',
+
-                () => {
+            void this.getAlbums().catch(logged('albums'));
-                    this.eagerFetch();
+            void this.getArtists().catch(logged('artists'));
-                },
+            void this.getGenres().catch(logged('genres'));
-                { once: true },
+        };
-            );
+
+        if (typeof requestIdleCallback === 'function') {
+            requestIdleCallback(warm, { timeout: WARM_IDLE_TIMEOUT_MS });
         } else {
-            // DOM already parsed (shouldn't happen during module
+            setTimeout(warm, 0);
-            // eval, but handles dynamic instantiation safely).
-            this.eagerFetch();
         }
     }
 
+    /**
+     * Start loading what a view will need, without waiting for it.
+     *
+     * A nav item calls this on hover or focus: that is the ~100 ms
+     * before the click, and it is what #280 trades for not paying for
+     * every collection at startup whether or not anyone goes there.
+     *
+     * A view this store holds nothing for is ignored rather than an
+     * error — it is a hint, and a hint about Home is not a mistake.
+     * The failure is swallowed here because the view that wanted the
+     * data reports it: this is the same request, already deduplicated
+     * by `inFlight`, and it has no caller to reject to.
+     */
+    prefetch(view: string): void {
+        const started = (() => {
+            switch (view) {
+                case 'tracks':
+                    return this.getTracks();
+                case 'albums':
+                    return this.getAlbums();
+                case 'artists':
+                    return this.getArtists();
+                case 'genres':
+                    return this.getGenres();
+                default:
+                    return null;
+            }
+        })();
+
+        void started?.catch(() => undefined);
+    }
+
+    private failureReporter(): (what: string) => (err: unknown) => void {
+        return (what) => (err) =>
+            console.error(`library: could not load ${what}`, err);
+    }
+
     // ===================================================================
     // DATA ACCESS
     // Returns cached data or fetches from backend on first access.
@@ -214,18 +272,18 @@ class LibraryStore {
         }
     }
 
-    async getTracks(): Promise<library.Track[]> {
+    async getTracks(): Promise<ListTrack[]> {
         if (this.tracks !== null) {
             return this.tracks;
         }
 
-        const pending = this.pending<library.Track[]>('tracks');
+        const pending = this.pending<ListTrack[]>('tracks');
 
         if (pending) return pending;
 
         return this.track(
             'tracks',
-            list(GetTracks(this.libraryFilter())),
+            GetTrackTable(this.libraryFilter()).then(decodeTrackTable),
             (tracks) => {
                 this.tracks = tracks;
             },
@@ -341,7 +399,7 @@ class LibraryStore {
     // Synchronous access for controllers that need current cached values.
     // ===================================================================
 
-    getCachedTracks(): library.Track[] | null {
+    getCachedTracks(): ListTrack[] | null {
         return this.tracks;
     }
 
@@ -497,6 +555,116 @@ class LibraryStore {
     // INVALIDATION
     // ===================================================================
 
+    /**
+     * A scan finished.  Reload only if it changed something (#282).
+     *
+     * `ScanMetrics` says how many files were added, updated and removed,
+     * and a soft rescan of an unchanged library reports zero of each —
+     * yet every loaded collection was thrown away and refetched, which
+     * at 26 138 tracks is 20.5 MB across the IPC for a scan that found
+     * nothing.  Anything non-zero still reloads everything: a scan can
+     * change a tag, an album name or a genre on any file it touched, and
+     * it reports counts rather than paths.
+     *
+     * A payload that says nothing at all is treated as a change, not as
+     * a no-op: an unknown shape must not be able to leave a stale list
+     * on screen.
+     */
+    private applyScanComplete(payload: unknown): void {
+        const m = payload as {
+            added?: number;
+            updated?: number;
+            removed?: number;
+        } | null;
+
+        if (!m) {
+            this.invalidate();
+
+            return;
+        }
+
+        const changed = (m.added ?? 0) + (m.updated ?? 0) + (m.removed ?? 0);
+
+        if (changed === 0) return;
+
+        this.invalidate();
+    }
+
+    /**
+     * Tags were rewritten on disk.  A single file is patched; a batch is
+     * a reload (#282).
+     *
+     * The event names the one file it rewrote, and that file's row is
+     * the only row that changed — so re-reading the whole list to pick
+     * up one new title is 20.5 MB at 26 138 tracks.  A batch write
+     * carries no paths (it can be thousands of files), and the summaries
+     * really do change with it, so that one still reloads.
+     */
+    private applyMetadataChanged(payload: unknown): void {
+        const p = payload as { filePath?: string; batch?: boolean } | null;
+
+        if (!p?.filePath || p.batch) {
+            this.invalidate();
+
+            return;
+        }
+
+        this.patchOneTrack(p.filePath);
+    }
+
+    /**
+     * Re-read one file's row and splice it in.
+     *
+     * The summaries are dropped and refetched, because a retag can move
+     * a track between albums and change a genre — they are the small
+     * collections, and they are what makes the album and artist views
+     * agree with the row that was just patched.
+     */
+    private patchOneTrack(filePath: string): void {
+        const loaded = this.loadedCollections();
+
+        void trackCache
+            .refresh([filePath])
+            .then(([fresh]) => {
+                if (!fresh || this.tracks === null) return;
+
+                const idx = this.tracks.findIndex(
+                    (t) => t.FilePath === filePath,
+                );
+
+                // Not in this view's list (another library's file, or
+                // gone): the list is right as it stands.
+                if (idx === -1) return;
+
+                this.tracks = [
+                    ...this.tracks.slice(0, idx),
+                    fresh,
+                    ...this.tracks.slice(idx + 1),
+                ];
+                this.changeGen++;
+                this.notify();
+            })
+            .catch((err: unknown) => {
+                // The patch failed, so the list may now be stale.  Fall
+                // back to the answer that cannot be wrong.
+                console.error('library: could not re-read a retagged track', err);
+                this.invalidate();
+            });
+
+        this.albums = null;
+        this.artists = null;
+        this.genres = null;
+        this.cacheGen++;
+        this.inFlight.delete('albums');
+        this.inFlight.delete('artists');
+        this.inFlight.delete('genres');
+        this.refetchLoaded({
+            albums: loaded.albums,
+            artists: loaded.artists,
+            genres: loaded.genres,
+        });
+    }
+
     /**
      * Patch one track's play statistics in place.
      *
@@ -520,10 +688,11 @@ class LibraryStore {
     private applyPlayCount(payload: unknown): void {
         if (this.tracks === null) return;
 
+        // The list does not carry LastPlayed (#281); trackCache patches
+        // it on the whole tracks the details dialog reads.
         const p = payload as {
             filePath?: string;
             playCount?: number;
-            lastPlayed?: string;
         } | null;
 
         if (!p?.filePath) return;
@@ -536,14 +705,10 @@ class LibraryStore {
 
         if (existing === undefined) return;
 
-        const patched = Object.assign(
+        const patched: ListTrack = {
-            Object.create(Object.getPrototypeOf(existing) as object),
+            ...existing,
-            existing,
+            PlayCount: p.playCount ?? existing.PlayCount,
-            {
+        };
-                PlayCount: p.playCount ?? existing.PlayCount,
-                LastPlayed: p.lastPlayed ?? existing.LastPlayed,
-            },
-        ) as library.Track;
 
         this.tracks = [
             ...this.tracks.slice(0, idx),
@@ -597,6 +762,8 @@ class LibraryStore {
             }
         }
 
+        const loaded = this.loadedCollections();
+
         this.albums = null;
         this.artists = null;
         this.genres = null;
@@ -612,50 +779,63 @@ class LibraryStore {
         this.changeGen++;
         this.notify();
 
-        const logged = (what: string) => (err: unknown) =>
+        // Only the summaries something was showing (#280): a removal
-            console.error(`library: could not reload ${what}`, err);
+        // nobody was looking at does not load a collection to correct it.
-
+        this.refetchLoaded({
-        void this.getAlbums().catch(logged('albums'));
+            albums: loaded.albums,
-        void this.getArtists().catch(logged('artists'));
+            artists: loaded.artists,
-        void this.getGenres().catch(logged('genres'));
+            genres: loaded.genres,
+        });
     }
 
     private invalidate(): void {
+        // Which collections something has actually loaded, before they
+        // are dropped. Refetching all four here would undo #280: a scan
+        // finishing would fetch the track list of a library nobody has
+        // opened the Tracks view on.
+        const loaded = this.loadedCollections();
+
         this.tracks = null;
         this.albums = null;
         this.artists = null;
         this.genres = null;
         // Anything still in flight was asked for on behalf of a
-        // selection that no longer applies: forget it, so the eager
+        // selection that no longer applies: forget it, so the refetch
-        // refetch below starts a request for the current one rather
+        // below starts a request for the current one rather than
-        // than adopting the old one's answer.
+        // adopting the old one's answer.
         this.inFlight.clear();
         this.cacheGen++;
         this.changeGen++;
         this.scrollPositions = { tracks: 0, albums: 0, artists: 0, genres: 0 };
         this.notify();
-        this.eagerFetch();
+        this.refetchLoaded(loaded);
+    }
+
+    /** The collections currently held, keyed by the view that draws them. */
+    private loadedCollections(): Partial<Record<ViewName, boolean>> {
+        return {
+            tracks: this.tracks !== null,
+            albums: this.albums !== null,
+            artists: this.artists !== null,
+            genres: this.genres !== null,
+        };
     }
 
     /**
-     * Fetches all library data.  Called after DOM ready
+     * Refetch exactly the collections named, and nothing else.
-     * (initial load, via deferEagerFetch) and after cache
+     *
-     * invalidation so that controller subscribers receive
+     * A failed fetch is reported by whichever view asked for the data
-     * fresh data on the next requestUpdate() cycle without
+     * (it is that panel's failure, not the app's), but this refetch has
-     * needing their own LibraryScanComplete listener.
+     * no caller to reject to — without a catch it is an unhandled
+     * rejection.
      */
-    private eagerFetch(): void {
+    private refetchLoaded(loaded: Partial<Record<ViewName, boolean>>): void {
-        // A failed fetch is reported by whichever view asked for the
+        const logged = this.failureReporter();
-        // data (it is that panel's failure, not the app's), but the
-        // eager refetch has no caller to reject to — without a catch it
-        // is an unhandled rejection.
-        const logged = (what: string) => (err: unknown) =>
-            console.error(`library: could not load ${what}`, err);
 
-        void this.getTracks().catch(logged('tracks'));
+        if (loaded.tracks) void this.getTracks().catch(logged('tracks'));
-        void this.getAlbums().catch(logged('albums'));
+        if (loaded.albums) void this.getAlbums().catch(logged('albums'));
-        void this.getArtists().catch(logged('artists'));
+        if (loaded.artists) void this.getArtists().catch(logged('artists'));
-        void this.getGenres().catch(logged('genres'));
+        if (loaded.genres) void this.getGenres().catch(logged('genres'));
     }
 
     // ===================================================================