fix(node,hub): key music/media metadata lookups by file_id, not path

IndexEntry.path is the *folder* a file is in (indexer.py's
_virtual_dir docstring: "the directory a file appears in"), not the
file itself. GroupIndex.get_entry_by_path() treated it as if it named
one file, and every one of its four callers did too:
_do_music_meta_request, _do_media_meta_request, _do_tmdb_override, and
_admin_exec_tmdb_override. Any two files sharing a folder — an album is
one folder with many tracks, a season is one folder with many episodes
— collided: a lookup by path silently returned whichever entry the
index happened to iterate to first, regardless of which file the
client actually asked about.

Found live (2026-08-25): three unrelated albums ("High Tone - Various",
two "Le Peuple de l'Herbe" albums) all showed the same MusicBrainz
cover, because all their representative tracks happened to sit in one
"high_tone" folder alongside a track that legitimately matched that
cover. A force-reload didn't help — the bug is server-side, not a
stale client state.

Fixed by keying these four request/response pairs by `file_id` (the
entry's own content hash — already unique, already how every other
lookup in the system identifies a file) instead of `path`, both in the
wire messages (music_meta_req/resp, media_meta_req/resp, tmdb_override)
and in music-app.js/video-app.js's own hooks. GroupIndex.get_entry_by_path
is now unused and removed — GroupIndex.get_entry(file_id) already did
the right thing.

No test previously exercised either handler with two entries sharing a
folder — the only existing coverage (test_tmdb_override_policy.py) gave
each entry its own folder, so the bug never had a chance to show up.
Added that scenario there and in two new test files, all confirmed
failing against the pre-fix code before being confirmed green against
the fix.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013XSohfUQQiaE77qyFLgSv3

3 files changed, 51 insertions, 42 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/music-app.js b/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
index 298e259..ae482ad 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
@@ -131,21 +131,21 @@ function groupMusicEntries(entries, audioRoot) {
 
 // -- album cover, MusicBrainz fetched lazily and only when actually needed --
 
-function useMusicMeta(transportRef, path, active) {
+function useMusicMeta(transportRef, fileId, active) {
   const [meta, setMeta] = useState(null);
   useEffect(() => {
-    if (!active || !path) return;
+    if (!active || !fileId) return;
     let cancelled = false;
     (async () => {
       const transport = transportRef.current;
       if (!transport || !transport.connected) return;
       try {
-        const resp = await transport.fetchMusicMeta(path);
+        const resp = await transport.fetchMusicMeta(fileId);
         if (!cancelled) setMeta(resp);
       } catch { if (!cancelled) setMeta({ confidence: 0 }); }
     })();
     return () => { cancelled = true; };
-  }, [path, active]);
+  }, [fileId, active]);
   return meta;
 }
 
@@ -196,7 +196,7 @@ function AlbumCard({ album, transportRef, gekRef, musicbrainzEnabled, onOpen })
   // Only when nothing in the library already gives us a cover -- the common
   // case (a well-tagged rip with embedded art) needs no network call at all.
   const needsLookup = musicbrainzEnabled && !repTrack.thumb_hash;
-  const meta = useMusicMeta(transportRef, repTrack.path, needsLookup);
+  const meta = useMusicMeta(transportRef, repTrack.id, needsLookup);
   const coverHash = repTrack.thumb_hash || (meta && meta.cover_thumb_hash) || null;
 
   return html`
@@ -218,7 +218,7 @@ function AlbumCard({ album, transportRef, gekRef, musicbrainzEnabled, onOpen })
 function MusicDetailModal({ album, transportRef, gekRef, musicbrainzEnabled, onClose, onPlayQueue }) {
   const repTrack = album.tracks.find((tr) => tr.thumb_hash) || album.tracks[0];
   const needsLookup = musicbrainzEnabled && !repTrack.thumb_hash;
-  const meta = useMusicMeta(transportRef, repTrack.path, needsLookup);
+  const meta = useMusicMeta(transportRef, repTrack.id, needsLookup);
   const coverHash = repTrack.thumb_hash || (meta && meta.cover_thumb_hash) || null;
 
   return html`
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport.js b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
index 065ccc0..7535594 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
@@ -498,13 +498,17 @@ class MeshBayTransport {
 
   /**
    * TMDB metadata for one file (Videos app, docs/mediacenter.md §5.4).
-   * `path` is root+relpath, exactly what index_sync/index_delta already
-   * gave this browser — never a raw filesystem path constructed here.
+   * Keyed by the entry's own `id` (its content hash) — never a path: a
+   * path names the *folder* a file is in (indexer.py's `_virtual_dir`), so
+   * two files sharing a folder (any multi-episode season) would resolve to
+   * whichever entry the node's index happened to return first (found live
+   * via the Music app's identical bug, 2026-08-25 — see webrtc_server.py's
+   * `_do_media_meta_request`).
    * `confidence: 0` (no tmdb_id, no fields) means no confident match —
    * the caller falls back to a thumbnail-only card (§4.1), not an error.
    */
-  async fetchMediaMeta(path) {
-    const msg = await this._sendAndWait({ type: 'media_meta_req', v: '0.5', path });
+  async fetchMediaMeta(fileId) {
+    const msg = await this._sendAndWait({ type: 'media_meta_req', v: '0.6', file_id: fileId });
     if (msg.type === 'error') throw new Error(msg.detail);
     return msg;
   }
@@ -550,15 +554,16 @@ class MeshBayTransport {
    * override would let any member vandalize another show's metadata.
    * Applies to every file sharing the representative one's display_title,
    * not just the file the operator happened to be looking at (webrtc_
-   * server.py's _admin_exec_tmdb_override).
+   * server.py's _admin_exec_tmdb_override). Keyed by `fileId`, not a path
+   * — same reasoning as fetchMediaMeta above.
    */
-  async overrideTmdbMatch(path, tmdbId, mediaType, signFn) {
+  async overrideTmdbMatch(fileId, tmdbId, mediaType, signFn) {
     const msg = await this._sendAndWait({
-      type: 'tmdb_override', v: '0.6', path, tmdb_id: tmdbId, media_type: mediaType,
+      type: 'tmdb_override', v: '0.7', file_id: fileId, tmdb_id: tmdbId, media_type: mediaType,
     });
     if (msg.type === 'error') throw new Error(msg.detail);
     if (msg.type === 'admin_challenge') {
-      const subject = `path=${path},tmdb_id=${tmdbId},media_type=${mediaType}`;
+      const subject = `file_id=${fileId},tmdb_id=${tmdbId},media_type=${mediaType}`;
       return this._authorizeAdminOp(msg, 'tmdb_override', subject, signFn);
     }
     return msg;
@@ -668,15 +673,19 @@ class MeshBayTransport {
   }
 
   /**
-   * MusicBrainz metadata for one track's path (Music app, docs/musicbay.md
-   * §4.3) — same shape as fetchMediaMeta, minus a season/episode concept:
+   * MusicBrainz metadata for one track (Music app, docs/musicbay.md §4.3)
+   * — same shape as fetchMediaMeta, minus a season/episode concept:
    * album-level (release), resolved from the track's own artist/album
-   * fields already in the index. `confidence: 0` means no confident match
-   * (or MusicBrainz off for this group, or nothing configured) — the caller
-   * falls back to the embedded/no cover it already had, not an error.
+   * fields already in the index. Keyed by the track's own `id` (content
+   * hash), not a path — a path names the *folder* a track is in, and an
+   * album is one folder with many tracks in it; three unrelated albums
+   * shared one folder's track's cover before this fix (found live,
+   * 2026-08-25). `confidence: 0` means no confident match (or MusicBrainz
+   * off for this group, or nothing configured) — the caller falls back to
+   * the embedded/no cover it already had, not an error.
    */
-  async fetchMusicMeta(path) {
-    const msg = await this._sendAndWait({ type: 'music_meta_req', v: '0.8', path });
+  async fetchMusicMeta(fileId) {
+    const msg = await this._sendAndWait({ type: 'music_meta_req', v: '0.9', file_id: fileId });
     if (msg.type === 'error') throw new Error(msg.detail);
     return msg;
   }
@@ -1467,10 +1476,10 @@ class MeshBayTransport {
         _key: obj.type === 'file_req'
           ? `chunk:${obj.file_id}:${obj.chunk_index}`
           : obj.type === 'ping' ? `ping:${obj.token}`
-          : obj.type === 'media_meta_req' ? `media_meta:${obj.path}`
+          : obj.type === 'media_meta_req' ? `media_meta:${obj.file_id}`
           // Same reordering hazard as media_meta_req: an album grid fires
           // one music_meta_req per visible tile, several at a time.
-          : obj.type === 'music_meta_req' ? `music_meta:${obj.path}`
+          : obj.type === 'music_meta_req' ? `music_meta:${obj.file_id}`
           // Same reordering hazard as media_meta_req: a season-tab bar or a
           // search box can have more than one of these in flight at once.
           : obj.type === 'season_meta_req' ? `season_meta:${obj.tmdb_id}:${obj.season}`
@@ -1652,7 +1661,7 @@ class MeshBayTransport {
     // member_upload_ack/apps_enabled_ack above.
     if (msg.type === 'tmdb_override_ack' && this._onTmdbOverride) {
       this._onTmdbOverride({
-        path: msg.path || '', tmdbId: msg.tmdb_id || '', mediaType: msg.media_type || '',
+        fileId: msg.file_id || '', tmdbId: msg.tmdb_id || '', mediaType: msg.media_type || '',
       });
     }
 
@@ -1774,21 +1783,21 @@ class MeshBayTransport {
     }
 
     if (msg.type === 'media_meta_resp') {
-      const key = `media_meta:${msg.path}`;
+      const key = `media_meta:${msg.file_id}`;
       for (const [, handler] of this._pending) {
         if (handler._key === key) { handler.resolve(msg); return; }
       }
-      // Nobody asked for this path any more (tile scrolled out and a fresh
+      // Nobody asked for this file any more (tile scrolled out and a fresh
       // request superseded it, most likely) — must not fall through to the
       // oldest pending request, which would hand a different tile's promise
-      // a TMDB result for a path it never asked about.
+      // a TMDB result for a file it never asked about.
       return;
     }
 
     // Same reasoning as media_meta_resp: keyed, not arrival-order, and
     // "nobody's waiting any more" must not fall through either.
     if (msg.type === 'music_meta_resp') {
-      const key = `music_meta:${msg.path}`;
+      const key = `music_meta:${msg.file_id}`;
       for (const [, handler] of this._pending) {
         if (handler._key === key) { handler.resolve(msg); return; }
       }
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/video-app.js b/packages/meshbay-hub/src/meshbay_hub/static/video-app.js
index de61839..ce38b0e 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/video-app.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/video-app.js
@@ -190,43 +190,43 @@ function MediaThumb({
 // ── TMDB metadata, fetched once per visible tile ────────────────────────────
 
 // An operator correcting a wrong match (TmdbSearchOverlay below) changes
-// what `media_meta_req` returns for a path every already-mounted tile/modal
+// what `media_meta_req` returns for a file every already-mounted tile/modal
 // already has cached in its own useMediaMeta state — nothing would ever
-// refetch otherwise, since path/active don't change. Bumping this and
+// refetch otherwise, since fileId/active don't change. Bumping this and
 // telling every subscribed hook to redo its fetch is simpler than trying to
-// know which paths a given override actually affects (that's server-side
+// know which files a given override actually affects (that's server-side
 // knowledge — display_title grouping — this module doesn't have).
 const _mediaMetaListeners = new Set();
 function bumpMediaMetaGeneration() {
   for (const fn of _mediaMetaListeners) fn();
 }
 
-function useMediaMeta(transportRef, path, active) {
+function useMediaMeta(transportRef, fileId, active) {
   const [meta, setMeta] = useState(null);
   const [refetchToken, setRefetchToken] = useState(0);
 
   useEffect(() => {
     // Clears immediately (so the spinner shows right away, not only once
     // the new fetch resolves) and bumps the token, which re-runs the fetch
-    // effect below regardless of whether path/active changed at all.
+    // effect below regardless of whether fileId/active changed at all.
     const listener = () => { setMeta(null); setRefetchToken((n) => n + 1); };
     _mediaMetaListeners.add(listener);
     return () => _mediaMetaListeners.delete(listener);
   }, []);
 
   useEffect(() => {
-    if (!active || !path) return;
+    if (!active || !fileId) return;
     let cancelled = false;
     (async () => {
       const transport = transportRef.current;
       if (!transport || !transport.connected) return;
       try {
-        const resp = await transport.fetchMediaMeta(path);
+        const resp = await transport.fetchMediaMeta(fileId);
         if (!cancelled) setMeta(resp);
       } catch { if (!cancelled) setMeta({ confidence: 0 }); }
     })();
     return () => { cancelled = true; };
-  }, [path, active, refetchToken]);
+  }, [fileId, active, refetchToken]);
   return meta;
 }
 
@@ -266,7 +266,7 @@ function useSeasonMeta(transportRef, tmdbId, season, active) {
 // ── Mode A: poster grid ──────────────────────────────────────────────────────
 
 function PosterCard({ title, subtitle, repEntry, transportRef, gekRef, onOpen, groupKey, onMetaResolved }) {
-  const meta = useMediaMeta(transportRef, repEntry.path, true);
+  const meta = useMediaMeta(transportRef, repEntry.id, true);
   const confident = Boolean(meta && meta.confidence && meta.tmdb_id);
   const metaReady = meta !== null;
 
@@ -366,7 +366,7 @@ function buildSignFn(transportRef) {
 }
 
 function TmdbSearchOverlay({
-  initialQuery, mediaType, path, transportRef, gekRef, onClose, onApplied,
+  initialQuery, mediaType, fileId, transportRef, gekRef, onClose, onApplied,
 }) {
   const [query, setQuery] = useState(initialQuery || '');
   const [results, setResults] = useState(null); // null = not searched yet
@@ -398,14 +398,14 @@ function TmdbSearchOverlay({
     setError('');
     try {
       const signFn = buildSignFn(transportRef);
-      await transportRef.current.overrideTmdbMatch(path, tmdbId, mediaType, signFn);
+      await transportRef.current.overrideTmdbMatch(fileId, tmdbId, mediaType, signFn);
       bumpMediaMetaGeneration();
       onApplied();
     } catch (err) {
       setError(err.message);
       setApplying(false);
     }
-  }, [applying, path, mediaType, transportRef, onApplied]);
+  }, [applying, fileId, mediaType, transportRef, onApplied]);
 
   return html`
     <div class="video-overlay video-search-overlay" onClick=${(e) => {
@@ -554,7 +554,7 @@ function VideoDetailModal({
     </div>
     ${searching && html`
       <${TmdbSearchOverlay} initialQuery=${(confident && meta.title) || title} mediaType=${mediaType}
-        path=${repEntry.path} transportRef=${transportRef} gekRef=${gekRef}
+        fileId=${repEntry.id} transportRef=${transportRef} gekRef=${gekRef}
         onClose=${() => setSearching(false)}
         onApplied=${() => setSearching(false)} />
     `}
@@ -615,7 +615,7 @@ function PosterGrid({ movies, shows, transportRef, gekRef, onPreview, tmdbEnable
   }, [shows, metaByGroup]);
 
   const openDetail = (title, repEntry, show) => setDetail({ title, repEntry, show });
-  const detailMeta = useMediaMeta(transportRef, detail ? detail.repEntry.path : null, !!detail);
+  const detailMeta = useMediaMeta(transportRef, detail ? detail.repEntry.id : null, !!detail);
 
   return html`
     <div class="video-grid">