MS Cin-5: Drop per-server globals — engine owns the clients

Per-server web_server.py globals (plex_client / jellyfin_client /
navidrome_client / soulsync_library_client) are gone. The engine now
owns the per-server client instances; web_server.py constructs them
inline into the engine init and routes everything through
media_server_engine.client('<name>').

Multi-client consumers refactored to take the engine instead of
separate per-server kwargs:

- services/sync_service.py: PlaylistSyncService.__init__ now takes
  media_server_engine. Internal _get_active_media_client resolves the
  active server's client through self._engine.client(name) instead of
  the per-server self.X_client attributes.
- core/listening_stats_worker.py: ListeningStatsWorker takes
  media_server_engine. The plex/jellyfin/navidrome dispatch in _poll
  collapses to engine.client(active_server) (gated to those three
  servers — SoulSync standalone has no listening data).
- core/web_scan_manager.py: WebScanManager takes media_server_engine
  instead of the hand-keyed media_clients dict that drifted out of
  sync with the engine.
- core/discovery/sync.py: SyncDeps holds media_server_engine instead
  of plex_client / jellyfin_client. Playlist-image dispatch routes
  through engine.client(name).

Web_server.py:
- Per-server globals removed from the chained `= None` init line
  + their try/except construction blocks. Replaced with a
  _safe_init_media_client(factory, name) helper that captures
  per-server init failures + passes the resulting clients straight
  into the MediaServerEngine init dict.
- All construction sites (PlaylistSyncService, WebScanManager,
  ListeningStatsWorker, SyncDeps, library_check) updated to receive
  the engine instead of per-server clients.

Test fixtures (tests/discovery/test_discovery_sync.py) gain a
_FakeMediaServerEngine stub + the SyncDeps build helper passes
that instead of separate plex/jellyfin clients.

core/discovery/sync.py

@@ -39,8 +39,7 @@ class SyncDeps:
     """Bundle of cross-cutting deps the sync worker needs."""
     config_manager: Any
     sync_service: Any
-    plex_client: Any
-    jellyfin_client: Any
+    media_server_engine: Any
     automation_engine: Any
     run_async: Callable[..., Any]
     record_sync_history_start: Callable
@@ -227,8 +226,9 @@ def run_sync_task(playlist_id, playlist_name, tracks_json, automation_id=None, p
             
         # Check sync service components
         logger.info(f"   spotify_client: {sync_service.spotify_client is not None}")
-        logger.info(f"   deps.plex_client: {sync_service.plex_client is not None}")
-        logger.info(f"   deps.jellyfin_client: {sync_service.jellyfin_client is not None}")
+        _ms_engine = getattr(sync_service, '_engine', None)
+        logger.info(f"   plex_client: {(_ms_engine.client('plex') if _ms_engine else None) is not None}")
+        logger.info(f"   jellyfin_client: {(_ms_engine.client('jellyfin') if _ms_engine else None) is not None}")
         
         # Check media server connection before starting
         from config.settings import config_manager
@@ -404,11 +404,12 @@ def run_sync_task(playlist_id, playlist_name, tracks_json, automation_id=None, p
             try:
                 active_server = deps.config_manager.get_active_media_server()
                 logger.info(f"[PLAYLIST IMAGE] active_server={active_server}")
-                if active_server == 'plex' and deps.plex_client:
-                    ok = deps.plex_client.set_playlist_image(playlist_name, playlist_image_url)
+                _engine = deps.media_server_engine
+                if active_server == 'plex' and _engine and _engine.client('plex'):
+                    ok = _engine.client('plex').set_playlist_image(playlist_name, playlist_image_url)
                     logger.info(f"[PLAYLIST IMAGE] Plex upload result: {ok}")
-                elif active_server in ('jellyfin', 'emby') and deps.jellyfin_client:
-                    ok = deps.jellyfin_client.set_playlist_image(playlist_name, playlist_image_url)
+                elif active_server in ('jellyfin', 'emby') and _engine and _engine.client('jellyfin'):
+                    ok = _engine.client('jellyfin').set_playlist_image(playlist_name, playlist_image_url)
                     logger.info(f"[PLAYLIST IMAGE] Jellyfin upload result: {ok}")
                 # Navidrome doesn't support custom playlist images
             except Exception as img_err:

core/listening_stats_worker.py

@@ -19,13 +19,17 @@ logger = get_logger("listening_stats_worker")
 class ListeningStatsWorker:
     """Background worker that polls media servers for play data."""
 
-    def __init__(self, database, config_manager, plex_client=None,
-                 jellyfin_client=None, navidrome_client=None):
+    def __init__(self, database, config_manager, media_server_engine=None):
+        """Initialize the worker.
+
+        ``media_server_engine`` owns the per-server clients (Plex /
+        Jellyfin / Navidrome). The worker resolves the active server's
+        client through ``self._engine.client(name)`` instead of holding
+        per-server kwargs.
+        """
         self.db = database
         self.config_manager = config_manager
-        self.plex_client = plex_client
-        self.jellyfin_client = jellyfin_client
-        self.navidrome_client = navidrome_client
+        self._engine = media_server_engine
 
         # Worker state
         self.running = False
@@ -145,13 +149,11 @@ class ListeningStatsWorker:
         logger.info(f"Polling {active_server} for listening data...")
         self.current_item = f"Polling {active_server}..."
 
-        client = None
-        if active_server == 'plex' and self.plex_client:
-            client = self.plex_client
-        elif active_server == 'jellyfin' and self.jellyfin_client:
-            client = self.jellyfin_client
-        elif active_server == 'navidrome' and self.navidrome_client:
-            client = self.navidrome_client
+        client = self._engine.client(active_server) if self._engine else None
+        # SoulSync standalone has no listening data; only the three
+        # streaming servers contribute. Mirror the legacy guard here.
+        if active_server not in ('plex', 'jellyfin', 'navidrome'):
+            client = None
 
         if not client:
             logger.warning(f"No client available for active server: {active_server}")

core/web_scan_manager.py

@@ -19,16 +19,21 @@ class WebScanManager:
     - Progress tracking and status reporting
     """
 
-    def __init__(self, media_clients, delay_seconds: int = 60):
+    def __init__(self, media_server_engine, delay_seconds: int = 60):
         """
         Initialize the web scan manager.
 
         Args:
-            media_clients: Dict containing plex_client, jellyfin_client, navidrome_client
+            media_server_engine: MediaServerEngine that owns the per-server
+                clients. Replaces the legacy ``media_clients`` dict — the
+                manager now resolves the active server's client through
+                ``self._engine.client(name)`` instead of a hand-keyed
+                dict that drifted out of sync with the engine's source
+                of truth.
             delay_seconds: Debounce delay in seconds (default 60s)
         """
         self.delay = delay_seconds
-        self.media_clients = media_clients
+        self._engine = media_server_engine
         self._timer = None
         self._scan_in_progress = False
         self._downloads_during_scan = False
@@ -44,29 +49,19 @@ class WebScanManager:
         logger.info(f"WebScanManager initialized with {delay_seconds}s debounce delay")
 
     def _get_active_media_client(self):
-        """Get the active media client based on config settings"""
+        """Get the active media client through the engine."""
         try:
             from config.settings import config_manager
             active_server = config_manager.get_active_media_server()
 
-            server_client_map = {
-                'jellyfin': 'jellyfin_client',
-                'navidrome': 'navidrome_client',
-                'plex': 'plex_client',
-                'soulsync': 'soulsync_library_client',
-            }
-
-            # Try to get the configured active server
-            if active_server in server_client_map:
-                client_key = server_client_map[active_server]
-                client = self.media_clients.get(client_key)
-                if client and hasattr(client, 'is_connected') and client.is_connected():
-                    return client, active_server
-                else:
-                    logger.warning(f"{active_server.title()} client not connected — scan skipped")
-                    return None, None
+            if not self._engine:
+                logger.error("Web scan manager has no engine reference")
+                return None, None
 
-            logger.error("No active media server configured for scanning")
+            client = self._engine.client(active_server)
+            if client and hasattr(client, 'is_connected') and client.is_connected():
+                return client, active_server
+            logger.warning(f"{(active_server or 'unknown').title()} client not connected — scan skipped")
             return None, None
 
         except Exception as e:

services/sync_service.py

@@ -44,17 +44,31 @@ class SyncProgress:
     failed_tracks: int = 0
 
 class PlaylistSyncService:
-    def __init__(self, spotify_client: SpotifyClient, plex_client: PlexClient, soulseek_client: SoulseekClient, jellyfin_client: JellyfinClient = None, navidrome_client = None):
+    def __init__(self, spotify_client: SpotifyClient, soulseek_client: SoulseekClient, media_server_engine=None):
+        """Initialize the sync service.
+
+        ``media_server_engine`` is the central MediaServerEngine that owns
+        the per-server clients (Plex / Jellyfin / Navidrome / SoulSync).
+        Replaces the legacy per-server kwargs (plex_client / jellyfin_client
+        / navidrome_client) — all media-server access now goes through
+        ``self._engine.client(name)`` so swapping the active server doesn't
+        need a service rebuild.
+        """
         self.spotify_client = spotify_client
-        self.plex_client = plex_client
-        self.jellyfin_client = jellyfin_client
-        self.navidrome_client = navidrome_client
+        self._engine = media_server_engine
         self.soulseek_client = soulseek_client
         self.progress_callbacks = {}  # Playlist-specific progress callbacks
         self.syncing_playlists = set()  # Track multiple syncing playlists
         self._cancelled = False
         self.matching_engine = MusicMatchingEngine()
-    
+
+    def _media_client(self, name: str):
+        """Resolve a per-server client through the engine, or None when the
+        engine isn't wired (defensive — every production path passes one)."""
+        if self._engine is None:
+            return None
+        return self._engine.client(name)
+
     def _get_active_media_client(self, profile_id=None):
         """Get the active media client based on config settings.
 
@@ -68,26 +82,27 @@ class PlaylistSyncService:
             active_server = config_manager.get_active_media_server()
 
             if active_server == "jellyfin":
-                if not self.jellyfin_client:
+                client = self._media_client('jellyfin')
+                if not client:
                     logger.error("Jellyfin client not provided to sync service")
                     return None, "jellyfin"
-                # Apply per-profile Jellyfin library if set
                 if profile_id:
-                    self._apply_profile_library(profile_id, 'jellyfin', self.jellyfin_client)
-                return self.jellyfin_client, "jellyfin"
+                    self._apply_profile_library(profile_id, 'jellyfin', client)
+                return client, "jellyfin"
             elif active_server == "navidrome":
-                if not self.navidrome_client:
+                client = self._media_client('navidrome')
+                if not client:
                     logger.error("Navidrome client not provided to sync service")
                     return None, "navidrome"
-                return self.navidrome_client, "navidrome"
+                return client, "navidrome"
             else:  # Default to Plex
-                # Apply per-profile Plex library if set
-                if profile_id:
-                    self._apply_profile_library(profile_id, 'plex', self.plex_client)
-                return self.plex_client, "plex"
+                client = self._media_client('plex')
+                if profile_id and client:
+                    self._apply_profile_library(profile_id, 'plex', client)
+                return client, "plex"
         except Exception as e:
             logger.error(f"Error determining active media server: {e}")
-            return self.plex_client, "plex"  # Fallback to Plex
+            return self._media_client('plex'), "plex"  # Fallback to Plex
     
     def _apply_profile_library(self, profile_id, server_type, client):
         """Apply per-profile library selection to a media client if configured."""

tests/discovery/test_discovery_sync.py

@@ -35,6 +35,15 @@ class _FakeMediaClient:
         return self._connected
 
 
+class _FakeMediaServerEngine:
+    """Stand-in for MediaServerEngine — only the bits SyncDeps needs."""
+    def __init__(self, plex=None, jellyfin=None, navidrome=None):
+        self._clients = {'plex': plex, 'jellyfin': jellyfin, 'navidrome': navidrome}
+
+    def client(self, name):
+        return self._clients.get(name)
+
+
 class _FakeSyncService:
     def __init__(self, *, media_client=None, server_type='plex',
                  sync_result=None, raise_on_sync=None,
@@ -44,8 +53,12 @@ class _FakeSyncService:
         self._sync_result = sync_result or _FakeSyncResult()
         self._raise_on_sync = raise_on_sync
         self.spotify_client = object() if spotify_client else None
-        self.plex_client = object() if plex_client else None
-        self.jellyfin_client = object() if jellyfin_client else None
+        # The sync_service exposes the engine so the discovery worker
+        # can introspect per-server clients via self._engine.client(name).
+        self._engine = _FakeMediaServerEngine(
+            plex=object() if plex_client else None,
+            jellyfin=object() if jellyfin_client else None,
+        )
         self.progress_callback = None
         self.progress_playlist_name = None
         self.cleared_callbacks = []
@@ -130,8 +143,10 @@ def _build_deps(
     return ds.SyncDeps(
         config_manager=config or _FakeConfig(),
         sync_service=sync_service or _FakeSyncService(media_client=_FakeMediaClient()),
-        plex_client=plex or _FakePlex(),
-        jellyfin_client=jellyfin or _FakeJellyfin(),
+        media_server_engine=_FakeMediaServerEngine(
+            plex=plex or _FakePlex(),
+            jellyfin=jellyfin or _FakeJellyfin(),
+        ),
         automation_engine=automation or _FakeAutomationEngine(),
         run_async=run_async or _run_async_sync,
         record_sync_history_start=record_sync_history_start or (lambda **kw: None),

web_server.py

@@ -570,7 +570,7 @@ IS_SHUTTING_DOWN = False
 # Each client is initialized independently so one failure doesn't take down everything.
 # Previously, a single exception set ALL clients to None, breaking the entire app.
 logger.info("Initializing SoulSync services for Web UI...")
-spotify_client = plex_client = jellyfin_client = navidrome_client = soulsync_library_client = soulseek_client = tidal_client = matching_engine = sync_service = web_scan_manager = None
+spotify_client = soulseek_client = tidal_client = matching_engine = sync_service = web_scan_manager = None
 
 try:
     spotify_client = get_spotify_client()
@@ -578,42 +578,31 @@ try:
 except Exception as e:
     logger.error(f"  Spotify client failed to initialize: {e}")
 
-try:
-    plex_client = PlexClient()
-    logger.info("  Plex client initialized")
-except Exception as e:
-    logger.error(f"  Plex client failed to initialize: {e}")
-
-try:
-    jellyfin_client = JellyfinClient()
-    logger.info("  Jellyfin client initialized")
-except Exception as e:
-    logger.error(f"  Jellyfin client failed to initialize: {e}")
 
-try:
-    navidrome_client = NavidromeClient()
-    logger.info("  Navidrome client initialized")
-except Exception as e:
-    logger.error(f"  Navidrome client failed to initialize: {e}")
+def _safe_init_media_client(factory, name):
+    """Build a media-server client, capturing per-server init failures
+    so one broken server doesn't take the engine down with it."""
+    try:
+        instance = factory()
+        logger.info(f"  {name} client initialized")
+        return instance
+    except Exception as exc:
+        logger.error(f"  {name} client failed to initialize: {exc}")
+        return None
 
-try:
-    from core.soulsync_client import SoulSyncClient
-    soulsync_library_client = SoulSyncClient()
-    logger.info("  SoulSync library client initialized")
-except Exception as e:
-    logger.error(f"  SoulSync library client failed to initialize: {e}")
 
-# Build the MediaServerEngine on top of the per-client globals above.
-# Engine wraps the same instances — no double-init. Provides
-# ``engine.method()`` dispatch in place of the historic
-# ``if active_server == 'plex' / 'jellyfin' / ...`` chains.
+# Build the MediaServerEngine. The engine OWNS the per-server client
+# instances — no separate web_server.py globals (Cin's standard from
+# the download refactor: drop redundant access paths). All callers go
+# through media_server_engine.client('<name>').
 try:
     from core.media_server.engine import MediaServerEngine, set_media_server_engine
+    from core.soulsync_client import SoulSyncClient
     media_server_engine = MediaServerEngine(clients={
-        'plex':      plex_client,
-        'jellyfin':  jellyfin_client,
-        'navidrome': navidrome_client,
-        'soulsync':  soulsync_library_client,
+        'plex':      _safe_init_media_client(PlexClient, "Plex"),
+        'jellyfin':  _safe_init_media_client(JellyfinClient, "Jellyfin"),
+        'navidrome': _safe_init_media_client(NavidromeClient, "Navidrome"),
+        'soulsync':  _safe_init_media_client(SoulSyncClient, "SoulSync library"),
     })
     # Install as process-wide singleton so callers reaching via
     # get_media_server_engine() see the same instance web_server.py
@@ -644,7 +633,7 @@ except Exception as e:
     logger.error(f"  Matching engine failed to initialize: {e}")
 
 try:
-    sync_service = PlaylistSyncService(spotify_client, plex_client, soulseek_client, jellyfin_client, media_server_engine.client('navidrome'))
+    sync_service = PlaylistSyncService(spotify_client, soulseek_client, media_server_engine=media_server_engine)
     logger.info("  Playlist sync service initialized")
 except Exception as e:
     logger.error(f"  Playlist sync service failed to initialize: {e}")
@@ -669,13 +658,7 @@ if soulseek_client:
 
 # Initialize web scan manager for automatic post-download scanning
 try:
-    media_clients = {
-        'plex_client': plex_client,
-        'jellyfin_client': jellyfin_client,
-        'navidrome_client': navidrome_client,
-        'soulsync_library_client': soulsync_library_client,
-    }
-    web_scan_manager = WebScanManager(media_clients, delay_seconds=60)
+    web_scan_manager = WebScanManager(media_server_engine, delay_seconds=60)
     logger.info("  Web scan manager initialized")
 except Exception as e:
     logger.error(f"  Web scan manager failed to initialize: {e}")
@@ -6879,7 +6862,7 @@ def enhanced_search_library_check():
         data = request.get_json() or {}
         result = _search_library_check.check_library_presence(
             database=get_database(),
-            plex_client=plex_client,
+            plex_client=media_server_engine.client('plex') if media_server_engine else None,
             config_manager=config_manager,
             profile_id=get_current_profile_id(),
             albums=data.get('albums', []),
@@ -23266,8 +23249,7 @@ def _build_sync_deps():
     return _discovery_sync.SyncDeps(
         config_manager=config_manager,
         sync_service=sync_service,
-        plex_client=plex_client,
-        jellyfin_client=jellyfin_client,
+        media_server_engine=media_server_engine,
         automation_engine=automation_engine,
         run_async=run_async,
         record_sync_history_start=_record_sync_history_start,
@@ -32848,9 +32830,7 @@ try:
     listening_stats_worker = ListeningStatsWorker(
         database=listening_stats_db,
         config_manager=config_manager,
-        plex_client=plex_client,
-        jellyfin_client=jellyfin_client,
-        navidrome_client=navidrome_client,
+        media_server_engine=media_server_engine,
     )
     listening_stats_worker.start()
     logger.info("Listening stats worker initialized and started")