fix(mobile): queue the track-page lineup from the hero Play button

[dylanjeffers]

The bug

When you press the big Play button at the top of a track-detail screen on mobile, it should queue up the related-tracks lineup that the same screen renders below — Remixes / More By <artist> / You Might Also Like — so playback continues past the hero track. Today it doesn't: the queue is exactly one item and playback stops at the end of the hero.

Every other lineup-driven screen on mobile (feed, profile tracks/reposts, library) does this correctly because its play interactions go through TrackLineup, which builds a multi-track playFrom queue with a querySource. The track screen's hero Play button bypasses TrackLineup entirely and dispatches its own playFrom.

Before

packages/mobile/src/screens/track-screen/TrackScreenDetailsTile.tsx:

dispatch(
  playbackActions.playFrom({
    tracks: [{ trackId, source: 'TRACK_TRACKS' }],
    startIndex: 0,
    querySource: null
  })
)

After

Subscribe to the same useTrackPageLineup hook that TrackScreenLineup already uses to render the sections below the track, and build the queue from trackIds:

const { trackIds: lineupTrackIds } = useTrackPageLineup(
  { trackId },
  { enabled: !!isReachable }   // mirror the gate on <TrackScreenLineup> in TrackScreen.tsx
)

// inside play():
const hasLineup =
  !isPreview &&
  lineupTrackIds.length > 1 &&
  lineupTrackIds[0] === trackId

const tracks: PlaybackTrack[] = hasLineup
  ? [
      { trackId, source: 'TRACK_TRACKS' },
      ...lineupTrackIds.slice(1).map((id) => ({
        trackId: id,
        source: 'TRACK_PAGE_MORE_BY'
      }))
    ]
  : [{ trackId, source: 'TRACK_TRACKS' }]

dispatch(
  playbackActions.playFrom({
    tracks,
    startIndex: 0,
    querySource: hasLineup
      ? { queryKey: [...getTrackPageLineupQueryKey(trackId)] }
      : null
  })
)

Why these specific source strings

• Hero stays 'TRACK_TRACKS' so its uid (makeStableUid(Kind.TRACKS, track_id, 'TRACK_TRACKS') from TrackScreen.tsx) still matches the queue entry, and the hero's own play-button state continues to derive correctly from the playback selectors.
• Related tracks use 'TRACK_PAGE_MORE_BY' because that is the source TrackScreenLineup already hands TrackLineup for all four sections (renderRemixParentSection, renderRemixesSection, renderMoreBySection, renderRecommendedSection). When auto-advance reaches a related track, the corresponding tile down the page highlights as currently-playing.

Why useTrackPageLineup here doesn't double-fetch

tanquery shares query data by key. TrackScreenLineup already subscribes via useTrackPageLineup({ trackId }); adding a second subscription in TrackScreenDetailsTile for the same trackId hits the same cache entry. The enabled: !!isReachable matches the truthiness check {isReachable ? <TrackScreenLineup>... in TrackScreen.tsx so we don't fire the network fetch when offline.

Edge cases

Case	Behavior
Preview button (isPreview === true)	Falls back to single-track queue. Preview is intentionally a one-track, no-auto-advance gesture.
Fast tap before lineup loads	lineupTrackIds.length <= 1 → falls back to single-track queue (today's behavior).
Offline	enabled: !!isReachable keeps the hook from firing → lineupTrackIds stays empty → single-track queue (today's behavior). The lineup section also doesn't render below in this state, so there's nothing to queue anyway.
lineupTrackIds[0] somehow isn't the hero	Defensive bail-out → single-track queue. Shouldn't happen — useTrackPageLineup always pushes the hero at index 0 and sets indices.mainTrackIndex = 0 — but the guard costs nothing.

Verification

• tsc --noEmit clean in packages/mobile.
• Manual: open a track, press Play → hero plays. Let it end → next track plays from More By or You Might Also Like, and the matching tile down the page highlights as playing.
• Manual: tap a track tile in the More By / You Might Also Like sections → still plays from that point in the same queue (unchanged from before).
• Manual: tap Preview on a gated track → plays the preview only, no auto-advance (unchanged from before).
• Manual: airplane-mode → tap Play → still plays the hero track as a single-track queue, no error, no extra fetch (lineup section is also hidden by isReachable).
• Manual: NowPlayingDrawer → Up Next list shows the related tracks queued after the hero.

🤖 Generated with Claude Code

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