Discord report (CJFC, 2026-04-26): syncing a Spotify playlist to the
server overwrote anything manually added to the server-side playlist.
The fix adds a per-sync mode picker next to the Sync button on the
playlist details modal — Replace (default, current delete-recreate
behavior) or Append only (preserves existing tracks, only adds new
ones). Useful when the source platform caps playlist size and the
user is manually building beyond it on the server.
Implementation:
* New `append_to_playlist(name, tracks)` method on Plex / Jellyfin /
Navidrome clients. Each uses the server's NATIVE append API:
- Plex: `existing_playlist.addItems(new_tracks)`
- Jellyfin: `POST /Playlists/<id>/Items?Ids=...&UserId=...`
- Navidrome: Subsonic `updatePlaylist?songIdToAdd=...`
Falls back to `create_playlist` when the playlist doesn't exist
yet (first sync). No delete-recreate, no backup playlist created
(preserves playlist creation date + metadata + non-soulsync-managed
tracks).
* Dedup-by-server-native-id (ratingKey for Plex, GUID for Jellyfin,
song-id for Navidrome) — never re-adds a track already on the
playlist. Server-native identity, not fuzzy title+artist match,
so it can't false-collide.
* `sync_service.sync_playlist` accepts `sync_mode='replace'|'append'`
kwarg. Single if/else branch dispatches to `append_to_playlist` or
`update_playlist`. Threaded through `core/discovery/sync.run_sync_task`
and the `/api/sync/start` HTTP handler. Validation on the API rejects
unknown mode strings (defaults to 'replace').
* Frontend: per-playlist `<select id="sync-mode-${id}">` rendered next
to the Sync button in both modal renderers (sync-spotify.js for
Spotify playlists, sync-services.js for Deezer ARL playlists).
`startPlaylistSync` reads the select at click time; missing select
(other callers like discover.js) defaults to 'replace' so backward
compat preserved without per-call-site updates.
* SoulSync standalone has no playlist methods at all and the modal
hides the Sync button entirely on it via `_isSoulsyncStandalone` —
dispatch never reaches that path, no defensive fallback needed.
15 new tests pin per-server append behavior:
- missing playlist → create_playlist delegation
- dedup filtering (existing IDs skipped, only new tracks added)
- empty new-track set short-circuits without API call
- failure paths return False without raising
- contract listing (KNOWN_PER_SERVER_METHODS includes
'append_to_playlist'; Plex / Jellyfin / Navidrome all implement)
Plus tests/discovery/test_discovery_sync.py fake `sync_playlist`
fixture got `sync_mode='replace'` default to match the new signature
(was breaking after the kwarg add; now passing).
WHATS_NEW entry under new '2.6.0' block (hidden by
`_getLatestWhatsNewVersion` until next release bump).
Closes CJFC discord request.
Pre-review audit found premature abstraction + lying docstrings.
Cut what isn't used, made the rest match what's actually shipped.
(1) Engine: dropped 7 cross-server dispatch wrappers that had ZERO
production callers (ensure_connection / get_all_artists /
get_all_album_ids / search_tracks / trigger_library_scan /
is_library_scanning / get_library_stats / get_recently_added_albums).
Every consumer reaches the active client directly via
sync_service._get_active_media_client() or engine.client(name).
Engine surface shrinks to client(name) / active_client() /
active_server / is_connected() (the one wrapper that has callers —
4 dashboard status sites) / configured_clients() / reload_config().
~150 lines deleted, 5 dead-method tests removed.
(2) Contract Protocol body trimmed to match REQUIRED_METHODS exactly
(is_connected, ensure_connection, get_all_artists, get_all_album_ids).
The other 5 methods that were declared in the Protocol
"required" section weren't actually required — Plex doesn't
implement get_recently_added_albums, Jellyfin doesn't implement
search_tracks, SoulSync doesn't implement most of them. Static
contract now matches runtime conformance test. Optional methods
moved to a KNOWN_PER_SERVER_METHODS data-only listing with audited
per-server coverage notes — discoverability without false promises.
(3) Engine module docstring + __init__.py docstring no longer
overclaim "33+ chains collapsed" — only 4 uniform-shape chains
were collapsed; ~18 server-specific chains stay explicit per the
"lift what's truly shared" standard. Phrasing now matches reality.
(4) types.py docstring claimed TrackInfo.from_jellyfin_dict and
TrackInfo.from_navidrome_dict exist as classmethods. They don't —
only from_plex_track / from_plex_playlist do. Jellyfin and Navidrome
construct TrackInfo inline at their call sites today. Docstring
now honest about that + flags the lift as a clean followup.
(5) Engine line 95 comment "backward-compat for source-specific
reaches" was misleading — there is no legacy alternative being
preserved; engine.client(name) IS the canonical access pattern.
Section header rewritten.
Tests: 2121 pass (was 2126; -5 dead-method pin tests).
`core/media_server/` package with the Protocol contract that
every media server client (Plex, Jellyfin, Navidrome, SoulSync
standalone) satisfies, plus the registry that holds them.
Required methods conservatively limited to the four every server
truly implements today: is_connected, ensure_connection,
get_all_artists, get_all_album_ids. Other generic methods
(search_tracks, trigger_library_scan, get_recently_added_albums,
etc.) are listed as OPTIONAL — present on most servers but not
all (SoulSync has no library-scan API since it walks the filesystem
directly; Jellyfin uses a different search shape). Phase B's
engine adapters route around the gaps with per-server fallback
instead of forcing every client to declare a no-op stub.
Same registry shape as the download plugin registry — single
source of truth for which servers exist + name resolution. Adding
a 5th server (Subsonic, Emby, etc.) becomes one register call
plus the new client class.
5 conformance tests pin every server class implements every
required method. Plan doc at docs/media-server-engine-refactor-plan.md.
Pure additive — no consumer routes through the contract or
registry yet. Suite still green (1921 passed).
