# Backfill songs played from device storage

A web player's first actual playback of a YouTube video in a session reports its known title, artist/channel, duration and thumbnail to `POST /api/media/:id/meta`. Local OPFS playback therefore no longer depends on `/api/streams` being called. Offline plays are held in memory until the browser returns online. Uploads and edited copies are excluded. Playback never waits for the report.

The server accepts only 11-character YouTube IDs, bounded strings, numeric duration and approved HTTPS YouTube artwork (local catalog artwork maps to the canonical thumbnail). Bodies are capped at 8 KB. Reports are limited to 20 per IP per minute and 100 globally, with a maximum of 32 outstanding backfill fetches. A response contains `{ok, known, cache}`; `known` describes whether a media row existed before the report, and `cache` is ready, queued, downloading, validating, unavailable or busy. Metadata can be registered even when the cache volume is offline or the queue is busy.

Device hints fill missing media fields with an atomic SQLite merge; existing titles, artists, durations, art and richer metadata are retained. Catalog ingestion also fills gaps and queues the existing bounded thumbnail collector. Admin's song list includes metadata-only entries, so its lyric tools have a title and artist before downloading completes. Inclusion in that list does not imply cached media is ready; `cacheStatus` reports the actual state.

Missing copies use the normal low-priority automatic `ensureCached` job, including its deduplication, single fetch lane, yt-dlp path, validation, duration/backoff limits, LRU byte budget, disk guard and USB volume marker. No parallel downloader or cache directory is introduced. Existing copies and in-progress jobs are skipped. Download failure keeps song metadata; the usual cache retry policy applies on later sessions. Offline-volume and busy responses do not force a fetch or bypass safety limits.

Verification: server validation/merge/route tests, admin metadata-only listing test, frontend once-per-session/offline reporter tests, all frontend unit tests, app syntax and server build. On a real phone, play a previously unknown OPFS song, inspect `/api/admin/media`, then verify a normal media-cache job and lyrics lookup. Repeat the play to confirm no second report; also test with the server's cache volume unavailable.