refactor: shared coalescer, profile-scoped prefs key, and form-error helper

lib/profiles/profile.dart

@@ -223,6 +223,23 @@ final RegExp _trailingHomeUserUuidPattern = RegExp(
   r'-([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}|[0-9a-fA-F]{16})$',
 );
 
+/// Prefs scope for a profile id: Plex Home profiles scope by their bare
+/// home-user uuid (`user_{uuid}_*`), other profiles by the full id.
+///
+/// Every `user_{scope}_{key}` prefs-key builder must apply this —
+/// [StorageService]'s `_migratePlexHomeUserScopes` relocates full-profile-id
+/// keys onto the uuid scope at every launch, so a builder that skips the
+/// normalization writes keys that vanish on the next restart (Trakt
+/// "unlinking" on hot restart was exactly this).
+String profileUserScope(String profileId) => parsePlexHomeProfileId(profileId)?.homeUserUuid ?? profileId;
+
+/// THE builder for profile-scoped prefs keys: `user_{scope}_{baseKey}`, or
+/// the bare [baseKey] for the empty (signed-out/account-level) scope.
+/// Pairs the `user_` prefix with [profileUserScope] in one place so no key
+/// builder can skip the normalization (see the warning above).
+String profileScopedPrefsKey(String userUuid, String baseKey) =>
+    userUuid.isEmpty ? baseKey : 'user_${profileUserScope(userUuid)}_$baseKey';
+
 /// Inverse of [plexHomeProfileId]. Returns `null` if [id] doesn't match the
 /// `plex-home-{accountConnectionId}-{homeUserUuid}` shape.
 ({String accountConnectionId, String homeUserUuid})? parsePlexHomeProfileId(String id) {

lib/screens/settings/add_jellyfin_screen.dart

@@ -574,10 +574,7 @@ class _AddJellyfinScreenState extends State<AddJellyfinScreen> with AsyncFormSta
           ),
         ],
       ],
-      if (errorText != null) ...[
-        const SizedBox(height: 12),
-        Text(errorText!, style: theme.textTheme.bodySmall?.copyWith(color: theme.colorScheme.error)),
-      ],
+      ...buildInlineError(theme),
     ];
   }
 
@@ -738,14 +735,7 @@ class _AddJellyfinScreenState extends State<AddJellyfinScreen> with AsyncFormSta
               label: Text(t.auth.quickConnectCancel),
             ),
           ),
-          if (errorText != null) ...[
-            const SizedBox(height: 16),
-            Text(
-              errorText!,
-              textAlign: TextAlign.center,
-              style: theme.textTheme.bodySmall?.copyWith(color: theme.colorScheme.error),
-            ),
-          ],
+          ...buildInlineError(theme, gap: 16, center: true),
         ],
       ),
     );

lib/screens/settings/add_plex_account_screen.dart

@@ -175,14 +175,7 @@ class _AddPlexAccountScreenState extends State<AddPlexAccountScreen> with AsyncF
                         ],
                       ),
                     ),
-                    if (errorText != null) ...[
-                      const SizedBox(height: 16),
-                      Text(
-                        errorText!,
-                        style: theme.textTheme.bodySmall?.copyWith(color: theme.colorScheme.error),
-                        textAlign: TextAlign.center,
-                      ),
-                    ],
+                    ...buildInlineError(theme, gap: 16, center: true),
                   ],
                 ),
               ),

lib/screens/settings/async_form_state_mixin.dart

@@ -1,4 +1,4 @@
-import 'package:flutter/widgets.dart';
+import 'package:flutter/material.dart';
 
 import '../../utils/app_logger.dart';
 
@@ -34,6 +34,19 @@ mixin AsyncFormStateMixin<T extends StatefulWidget> on State<T> {
     setState(() => _busy = value);
   }
 
+  /// Inline error text under a form. Spread into a children list:
+  /// `...buildInlineError(theme)`.
+  List<Widget> buildInlineError(ThemeData theme, {double gap = 12, bool center = false}) => [
+    if (errorText != null) ...[
+      SizedBox(height: gap),
+      Text(
+        errorText!,
+        style: theme.textTheme.bodySmall?.copyWith(color: theme.colorScheme.error),
+        textAlign: center ? TextAlign.center : null,
+      ),
+    ],
+  ];
+
   /// Set the error text directly (e.g. for synchronous validation failures
   /// or post-success rejections like a duplicate-account guard).
   void setErrorText(String? value) {

lib/screens/settings/edit_jellyfin_connection_screen.dart

@@ -124,10 +124,7 @@ class _EditJellyfinConnectionScreenState extends State<EditJellyfinConnectionScr
                       label: Text(t.common.save),
                     ),
                   ),
-                  if (errorText != null) ...[
-                    const SizedBox(height: 12),
-                    Text(errorText!, style: theme.textTheme.bodySmall?.copyWith(color: theme.colorScheme.error)),
-                  ],
+                  ...buildInlineError(theme),
                 ],
               ),
             ),

lib/services/storage_service.dart

@@ -96,12 +96,12 @@ class StorageService extends BaseSharedPreferencesService {
   /// full profile id is the scope.
   String? activeUserScope() => _activeUserScope();
 
-  String userScopeForProfileId(String profileId) => parsePlexHomeProfileId(profileId)?.homeUserUuid ?? profileId;
+  String userScopeForProfileId(String profileId) => profileUserScope(profileId);
 
   String? _activeUserScope() {
     final id = getActiveProfileId();
     if (id == null) return null;
-    return parsePlexHomeProfileId(id)?.homeUserUuid ?? id;
+    return profileUserScope(id);
   }
 
   /// Returns `'user_{scope}_'` for the active profile, or `''` if no

lib/services/trackers/future_coalescer.dart

@@ -12,4 +12,30 @@ class FutureCoalescer<T> {
     _inFlight = future;
     return future;
   }
+
+  /// Detach the in-flight future (it keeps running, but the next [run]
+  /// starts fresh instead of joining it). The identical-guard above keeps
+  /// the detached future's completion from clearing a newer slot.
+  void reset() {
+    _inFlight = null;
+  }
+}
+
+/// Keyed [FutureCoalescer]: one in-flight future per key. Used for the
+/// static per-identity re-auth/refresh maps (Trakt refresh-by-token, Seerr
+/// re-auth-by-instance) so concurrent 401s trigger one login each.
+class KeyedFutureCoalescer<K, T> {
+  final Map<K, Future<T>> _inFlight = {};
+
+  Future<T> run(K key, Future<T> Function() create) {
+    final existing = _inFlight[key];
+    if (existing != null) return existing;
+
+    late final Future<T> future;
+    future = create().whenComplete(() {
+      if (identical(_inFlight[key], future)) _inFlight.remove(key);
+    });
+    _inFlight[key] = future;
+    return future;
+  }
 }

lib/services/trackers/tracker_account_store.dart

@@ -1,3 +1,4 @@
+import '../../profiles/profile.dart';
 import '../base_shared_preferences_service.dart';
 import 'tracker_constants.dart';
 import 'tracker_session.dart';
@@ -25,7 +26,7 @@ class TrackerAccountStore {
 
   TrackerAccountStore._(this.service, this._baseKey);
 
-  String _scopedKey(String userUuid) => userUuid.isEmpty ? _baseKey : 'user_${userUuid}_$_baseKey';
+  String _scopedKey(String userUuid) => profileScopedPrefsKey(userUuid, _baseKey);
 
   Future<TrackerSession?> load(String userUuid) async {
     final prefs = await BaseSharedPreferencesService.sharedCache();

test/services/trackers/tracker_account_store_scope_test.dart

@@ -0,0 +1,54 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:plezy/profiles/profile.dart';
+import 'package:plezy/services/base_shared_preferences_service.dart';
+import 'package:plezy/services/trackers/tracker_account_store.dart';
+import 'package:plezy/services/trackers/tracker_constants.dart';
+import 'package:plezy/services/trackers/tracker_session.dart';
+
+import '../../test_helpers/prefs.dart';
+
+const _fullProfileId = 'plex-home-plex.e443d57860076fc3-e443d57860076fc3';
+const _homeUserUuid = 'e443d57860076fc3';
+
+TrackerSession _session() {
+  final now = DateTime.now().millisecondsSinceEpoch ~/ 1000;
+  return TrackerSession(accessToken: 'a', refreshToken: 'r', expiresAt: now + 86400, createdAt: now);
+}
+
+void main() {
+  setUp(resetSharedPreferencesForTest);
+
+  group('profile user scoping', () {
+    test('profileUserScope reduces Plex Home ids to the bare home-user uuid', () {
+      expect(profileUserScope(_fullProfileId), _homeUserUuid);
+      expect(profileUserScope(_homeUserUuid), _homeUserUuid);
+      expect(profileUserScope('local-abc'), 'local-abc');
+    });
+
+    test('profileScopedPrefsKey normalizes full profile ids to the uuid scope', () {
+      expect(profileScopedPrefsKey(_fullProfileId, 'trakt_session'), 'user_${_homeUserUuid}_trakt_session');
+      expect(profileScopedPrefsKey(_homeUserUuid, 'trakt_session'), 'user_${_homeUserUuid}_trakt_session');
+      expect(profileScopedPrefsKey('', 'trakt_session'), 'trakt_session');
+    });
+
+    /// Regression: sessions saved under the full profile id were relocated to
+    /// the uuid scope by StorageService's launch-time repair, so the next
+    /// hydrate (same full id) missed them — Trakt "unlinked" on every
+    /// restart. Save and load must agree on the uuid scope regardless of
+    /// which id form the caller passes.
+    test('store writes the uuid-scoped key and loads it from either id form', () async {
+      final store = trackerAccountStore(TrackerService.trakt);
+      await store.save(_fullProfileId, _session());
+
+      final prefs = await BaseSharedPreferencesService.sharedCache();
+      expect(prefs.getString('user_${_homeUserUuid}_trakt_session'), isNotNull);
+      expect(prefs.getString('user_${_fullProfileId}_trakt_session'), isNull);
+
+      expect(await store.load(_fullProfileId), isNotNull);
+      expect(await store.load(_homeUserUuid), isNotNull);
+
+      await store.clear(_fullProfileId);
+      expect(await store.load(_homeUserUuid), isNull);
+    });
+  });
+}