fix(sync): scope interval timer to file-based providers and drop unneeded migration

Guard the periodic sync interval timer behind a useIntervalTimer flag so it
only fires for file-based providers (WebDAV, LocalFile, Nextcloud). SuperSync
uses WebSocket push notifications and does not need polling.

Remove the syncFolderPath backwards-compatibility migration: master already
routes localFileSync settings to the credential store via PROP_MAP_TO_FORM,
so no real users have the path in global config.

src/app/imex/sync/sync-config.service.ts

@@ -3,7 +3,7 @@ import { SyncProviderManager } from '../../op-log/sync-providers/provider-manage
 import { GlobalConfigService } from '../../features/config/global-config.service';
 import { combineLatest, from, Observable, of } from 'rxjs';
 import { SyncConfig } from '../../features/config/global-config.model';
-import { first, switchMap, tap } from 'rxjs/operators';
+import { switchMap, tap } from 'rxjs/operators';
 import {
   CurrentProviderPrivateCfg,
   PrivateCfgByProviderId,
@@ -14,7 +14,6 @@ import { SyncLog } from '../../core/log';
 import { clearSessionKeyCache } from '../../op-log/encryption/encryption';
 import { SuperSyncPrivateCfg } from '../../op-log/sync-providers/super-sync/super-sync.model';
 import { SyncWrapperService } from './sync-wrapper.service';
-import { LocalFileSyncPrivateCfg } from '../../op-log/core/types/sync.types';
 
 // Maps sync providers to their corresponding form field in SyncConfig
 // Dropbox is null because it doesn't store settings in the form (uses OAuth)
@@ -103,19 +102,6 @@ export class SyncConfigService {
 
   private _lastSettings: SyncConfig | null = null;
 
-  constructor() {
-    // One-time startup migration: move syncFolderPath from legacy global config to credential
-    // store. Must run at startup (not only when sync settings UI is open) so that the app
-    // correctly finds the configured folder after a restart. Fixes: #5455 (Mac restart).
-    this._globalConfigService.sync$
-      .pipe(first((cfg) => !!cfg?.localFileSync?.syncFolderPath))
-      .subscribe((cfg) => {
-        this._migrateLegacyLocalFileSyncPath(cfg.localFileSync!.syncFolderPath!).catch(
-          (e) => SyncLog.err('SyncConfigService: LocalFile path migration failed', e),
-        );
-      });
-  }
-
   private _deriveEncryptionState(
     baseConfig: SyncConfig,
     currentProviderCfg: CurrentProviderPrivateCfg | null,
@@ -423,47 +409,4 @@ export class SyncConfigService {
       clearSessionKeyCache();
     }
   }
-
-  /**
-   * Migrates syncFolderPath from the legacy global config storage to SyncCredentialStore.
-   *
-   * Older versions stored the LocalFile sync folder path in globalConfig.sync.localFileSync.
-   * The current architecture stores it in SyncCredentialStore (IndexedDB 'sup-sync').
-   * This one-time migration preserves the user's configured folder across upgrades.
-   * Fixes: Mac forgets sync folder on restart (#5455).
-   */
-  private async _migrateLegacyLocalFileSyncPath(legacyPath: string): Promise<void> {
-    SyncLog.normal(
-      'SyncConfigService: Checking for legacy LocalFile syncFolderPath migration',
-    );
-    const provider = await this._providerManager.getProviderById(
-      SyncProviderId.LocalFile,
-    );
-    if (!provider) {
-      // Provider not registered (e.g. web build). Clear the stale field anyway so
-      // it never triggers migration again and doesn't silently persist.
-      SyncLog.warn(
-        'SyncConfigService: LocalFile provider not found during migration; clearing legacy field',
-      );
-    } else {
-      const existingCfg =
-        (await provider.privateCfg.load()) as LocalFileSyncPrivateCfg | null;
-      if (!existingCfg?.syncFolderPath) {
-        SyncLog.normal(
-          'SyncConfigService: Migrating LocalFile syncFolderPath from global config to credential store',
-        );
-        await provider.privateCfg.upsertPartial({
-          syncFolderPath: legacyPath,
-        } as LocalFileSyncPrivateCfg);
-      }
-    }
-    // Always clear the legacy path from global config so this migration never re-runs.
-    // Spread DEFAULT to avoid shallow-merge data loss on any other localFileSync fields.
-    this._globalConfigService.updateSection('sync', {
-      localFileSync: {
-        ...DEFAULT_GLOBAL_CONFIG.sync.localFileSync,
-        syncFolderPath: null,
-      },
-    });
-  }
 }

src/app/imex/sync/sync-trigger.service.ts

@@ -206,7 +206,10 @@ export class SyncTriggerService {
     shareReplay(1),
   );
 
-  getSyncTrigger$(syncInterval: number = SYNC_DEFAULT_AUDIT_TIME): Observable<unknown> {
+  getSyncTrigger$(
+    syncInterval: number = SYNC_DEFAULT_AUDIT_TIME,
+    useIntervalTimer = false,
+  ): Observable<unknown> {
     const _immediateSyncTrigger$: Observable<string> = IS_ANDROID_WEB_VIEW
       ? // ANDROID ONLY
         merge(
@@ -233,9 +236,11 @@ export class SyncTriggerService {
           this._onElectronResumeTrigger$,
           // Periodic interval timer: fires every syncInterval ms to detect external file
           // changes (e.g. Syncthing on Linux) even without user activity.
-          // Applies to Electron desktop and web/PWA (not Android, which has its own timer).
+          // Only for file-based providers — SuperSync uses WebSocket push and doesn't need polling.
           // Fixes: Linux auto-sync ignoring interval (#4783)
-          timer(syncInterval, syncInterval).pipe(mapTo('I_INTERVAL_TIMER')),
+          ...(useIntervalTimer
+            ? [timer(syncInterval, syncInterval).pipe(mapTo('I_INTERVAL_TIMER'))]
+            : []),
         );
     return merge(
       // once immediately

src/app/imex/sync/sync.effects.ts

@@ -135,10 +135,14 @@ export class SyncEffects {
             combineLatest([
               this._syncWrapperService.isEnabledAndReady$,
               this._syncWrapperService.syncInterval$,
+              this._syncWrapperService.syncProviderId$,
             ]).pipe(
-              switchMap(([isEnabledAndReady, syncInterval]) =>
+              switchMap(([isEnabledAndReady, syncInterval, providerId]) =>
                 isEnabledAndReady && syncInterval
-                  ? this._syncTriggerService.getSyncTrigger$(syncInterval)
+                  ? this._syncTriggerService.getSyncTrigger$(
+                      syncInterval,
+                      providerId !== SyncProviderId.SuperSync,
+                    )
                   : EMPTY,
               ),
             ),

src/main.ts

@@ -81,7 +81,6 @@ import { Log } from './app/core/log';
 import { OperationWriteFlushService } from './app/op-log/sync/operation-write-flush.service';
 import { PluginOAuthRedirectHandler } from './app/plugins/oauth/plugin-oauth-redirect.handler';
 import { OAuthCallbackHandlerService } from './app/imex/sync/oauth-callback-handler.service';
-import { SyncConfigService } from './app/imex/sync/sync-config.service';
 import { GlobalConfigService } from './app/features/config/global-config.service';
 import { LocaleDatePipe } from './app/ui/pipes/locale-date.pipe';
 import { DateTimeFormatService } from './app/core/date-time-format/date-time-format.service';
@@ -281,17 +280,6 @@ bootstrapApplication(AppComponent, {
       deps: [OAuthCallbackHandlerService],
       multi: true,
     },
-    // Ensure SyncConfigService is instantiated at bootstrap so the startup migration
-    // (syncFolderPath from global config → credential store) runs on every app launch,
-    // not only when the sync settings UI is opened. Fixes: #5455 (Mac restart).
-    {
-      provide: APP_INITIALIZER,
-      useFactory: (_svc: SyncConfigService) => {
-        return () => {};
-      },
-      deps: [SyncConfigService],
-      multi: true,
-    },
     // Note: ImmediateUploadService now initializes itself in constructor
     // after DataInitStateService.isAllDataLoadedInitially$ fires to avoid
     // race condition where upload attempts happen before sync config is loaded