diff --git a/AGENT_HANDOFF.md b/AGENT_HANDOFF.md
index f95136b..a5ddec3 100644
--- a/AGENT_HANDOFF.md
+++ b/AGENT_HANDOFF.md
@@ -135,6 +135,27 @@ Do not touch:
 
 ## Current Handoff
 
+Agent: Claude Code (Opus 4.8)
+Date/time: 2026-05-30T17:30:00+02:00
+Task: Fix user-reported bug — "RESETTA TUTTI I DATI" (reset all data) in Settings wiped shifts locally but, for users with an active (authenticated) account, all deleted shifts reappeared on reload because the reset never propagated to Firestore; the realtime `onSnapshot` listeners restored them.
+Status: done. Committed and pushed to `claude/firebase-data-reset-sync-fOJuQ` (this is a web session whose explicit task is to deliver the fix on that branch).
+Root cause: `ShiftService.deleteAllShifts()` only called `userDataService.setState(EMPTY_SHIFT_DATA_STATE)` — a local-only wipe. The Firestore docs under `users/{uid}/{shiftSeries,manualShifts,shiftOverrides}` were never deleted, so on the next reload `FirestoreUserDataService.start()` re-hydrated them and `UserDataService`'s effect mirrored them back to local state. `deleteUserDataTree` existed but was wired only into account deletion.
+Fix (3 source files):
+- `firestore-user-data.service.ts`: new `clearShiftData(uid)` — batch-deletes only the three shift collections (`shiftSeries`, `manualShifts`, `shiftOverrides`), deliberately leaving `devices`/`profile`/`settings` intact (unlike `deleteUserDataTree`, which is the full account-deletion nuke).
+- `user-data.service.ts`: new `clearAll()` — sets local state to EMPTY synchronously, then, when authenticated, awaits `firestore.clearShiftData(uid)`.
+- `shift.service.ts`: `deleteAllShifts()` now calls `void this.userDataService.clearAll()` instead of `setState(EMPTY...)`.
+No-resurrection reasoning: local wipe is synchronous; the `UserDataService` effect tracks `firestore.state()` (not local `_state`), so the local empty isn't overwritten until the cloud delete's snapshot fires empty too → consistent. Account-deletion path (`clearLocalAccountData`) is unaffected: it runs after `deleteAccount()` (which already calls `deleteUserDataTree` + `deleteUser`), so by then auth is no longer authenticated and `clearAll` issues no redundant cloud delete.
+Files changed: `src/services/firestore-user-data.service.ts` (+spec), `src/services/user-data.service.ts` (+spec), `src/services/shift.service.ts`, `AGENT_HANDOFF.md` (this block).
+Tests red: none.
+Tests green: full Jest suite 689/689 (was 686; +3 new: `clearShiftData` collection-scope test, `clearAll` authenticated + guest tests); `npm run lint` clean; `npm run build` OK.
+Open concerns:
+- Behavior verified by unit tests + build only; no authenticated browser/E2E run (Firestore deletion path requires a real logged-in session). Recommend a quick manual check on a real account: add shifts → reset → reload → confirm they stay gone.
+- The environment's `grep -n` line numbers were unreliable this session (shell output layer glitching); all edits were verified by re-reading file content, not by trusting line numbers.
+Next agent starts from: fix is on `claude/firebase-data-reset-sync-fOJuQ`. If the user wants it in production it must be merged to `main` (triggers Cloudflare Pages deploy).
+Do not touch: do not delete `web9.png` (local-only, ignored).
+
+---
+
 Agent: Claude Code (Opus 4.7)
 Date/time: 2026-05-25T00:15:00+02:00
 Task: Create `update.md` — a maintenance/update schedule documenting every dependency/framework/native group to re-check every 30/60 days, with cadence table, exact commands, and a check log. User-requested, doc-only.
diff --git a/src/services/firestore-user-data.service.spec.ts b/src/services/firestore-user-data.service.spec.ts
index 172708c..302fde2 100644
--- a/src/services/firestore-user-data.service.spec.ts
+++ b/src/services/firestore-user-data.service.spec.ts
@@ -442,6 +442,37 @@ describe('FirestoreUserDataService', () => {
       );
     });
 
+    it('deletes only the shift data collections in clearShiftData, leaving devices/profile/settings intact', async () => {
+      const service = TestBed.inject(FirestoreUserDataService);
+      (firestore.getDocs as jest.Mock).mockResolvedValue({
+        docs: [{ ref: 'ref-1' }, { ref: 'ref-2' }],
+      });
+
+      await service.clearShiftData('uid-1');
+
+      // 3 collections (shiftSeries, manualShifts, shiftOverrides) * 2 docs each = 6 deletes.
+      // No devices/profile/settings deletes so the account stays alive.
+      expect(batch.delete).toHaveBeenCalledTimes(6);
+      expect(batch.commit).toHaveBeenCalledTimes(1);
+      expect(firestore.getDocs).toHaveBeenCalledTimes(3);
+      expect(firestore.collection).toHaveBeenCalledWith(
+        expect.anything(),
+        'users/uid-1/shiftSeries'
+      );
+      expect(firestore.collection).toHaveBeenCalledWith(
+        expect.anything(),
+        'users/uid-1/manualShifts'
+      );
+      expect(firestore.collection).toHaveBeenCalledWith(
+        expect.anything(),
+        'users/uid-1/shiftOverrides'
+      );
+      expect(firestore.collection).not.toHaveBeenCalledWith(
+        expect.anything(),
+        'users/uid-1/devices'
+      );
+    });
+
     it('deletes all user data collections and profile/settings in deleteUserDataTree', async () => {
       const service = TestBed.inject(FirestoreUserDataService);
       (firestore.getDocs as jest.Mock).mockResolvedValue({
diff --git a/src/services/firestore-user-data.service.ts b/src/services/firestore-user-data.service.ts
index 0b451a5..966b524 100644
--- a/src/services/firestore-user-data.service.ts
+++ b/src/services/firestore-user-data.service.ts
@@ -180,6 +180,22 @@ export class FirestoreUserDataService {
     await batch.commit();
   }
 
+  /**
+   * Clears all shift data (series, manual shifts and overrides) for the user
+   * while leaving the device registry, profile and settings intact. Backs the
+   * "reset all data" action so the deletion propagates to the cloud and is not
+   * restored by the realtime listeners on the next reload.
+   */
+  async clearShiftData(uid: string): Promise<void> {
+    const db = this.firebase.firestore;
+    const batch = writeBatch(db);
+    for (const path of ['shiftSeries', 'manualShifts', 'shiftOverrides']) {
+      const snapshot = await getDocs(collection(db, `users/${uid}/${path}`));
+      snapshot.docs.forEach(document => batch.delete(document.ref));
+    }
+    await batch.commit();
+  }
+
   async deleteUserDataTree(uid: string): Promise<void> {
     const db = this.firebase.firestore;
     const batch = writeBatch(db);
diff --git a/src/services/shift.service.ts b/src/services/shift.service.ts
index eaf3079..df9ac08 100755
--- a/src/services/shift.service.ts
+++ b/src/services/shift.service.ts
@@ -696,7 +696,7 @@ export class ShiftService {
 
   deleteAllShifts(): void {
     void this.notificationService.cancelAllNotifications();
-    this.userDataService.setState(EMPTY_SHIFT_DATA_STATE);
+    void this.userDataService.clearAll();
   }
 
   exportBackupPayload(): string {
diff --git a/src/services/user-data.service.spec.ts b/src/services/user-data.service.spec.ts
index 42ac0fe..835a6ec 100644
--- a/src/services/user-data.service.spec.ts
+++ b/src/services/user-data.service.spec.ts
@@ -21,6 +21,7 @@ describe('UserDataService', () => {
     upsertShiftOverride: jest.Mock;
     applyBatch: jest.Mock;
     removeDevice: jest.Mock;
+    clearShiftData: jest.Mock;
   };
 
   beforeEach(() => {
@@ -41,6 +42,7 @@ describe('UserDataService', () => {
       upsertShiftOverride: jest.fn().mockResolvedValue(undefined),
       applyBatch: jest.fn().mockResolvedValue(undefined),
       removeDevice: jest.fn().mockResolvedValue(undefined),
+      clearShiftData: jest.fn().mockResolvedValue(undefined),
     };
 
     TestBed.resetTestingModule();
@@ -162,6 +164,46 @@ describe('UserDataService', () => {
     });
   });
 
+  describe('clearAll', () => {
+    const nonEmpty: ShiftDataState = {
+      schemaVersion: 2,
+      shiftSeries: [],
+      manualShifts: [
+        {
+          id: 'm-clear',
+          title: 'To be cleared',
+          start: '2026-03-01T08:00:00.000Z',
+          end: '2026-03-01T16:00:00.000Z',
+          color: 'sky',
+          createdAt: '2026-03-01T00:00:00.000Z',
+          updatedAt: '2026-03-01T00:00:00.000Z',
+        },
+      ],
+      shiftOverrides: [],
+    };
+
+    it('clears local state and deletes cloud shift data when authenticated', async () => {
+      authMock.state.set({ mode: 'authenticated', uid: 'uid-abc' });
+      const service = TestBed.inject(UserDataService);
+      service.setState(nonEmpty);
+
+      await service.clearAll();
+
+      expect(service.state()).toEqual(EMPTY_SHIFT_DATA_STATE);
+      expect(firestoreMock.clearShiftData).toHaveBeenCalledWith('uid-abc');
+    });
+
+    it('clears local state without touching Firestore in guest mode', async () => {
+      const service = TestBed.inject(UserDataService);
+      service.setState(nonEmpty);
+
+      await service.clearAll();
+
+      expect(service.state()).toEqual(EMPTY_SHIFT_DATA_STATE);
+      expect(firestoreMock.clearShiftData).not.toHaveBeenCalled();
+    });
+  });
+
   describe('mutate', () => {
     it('mutates state locally in guest mode without calling Firestore', async () => {
       const service = TestBed.inject(UserDataService);
diff --git a/src/services/user-data.service.ts b/src/services/user-data.service.ts
index 2737d75..7db36f2 100644
--- a/src/services/user-data.service.ts
+++ b/src/services/user-data.service.ts
@@ -39,6 +39,19 @@ export class UserDataService {
     this._state.set(next);
   }
 
+  /**
+   * Clears all shift data locally and, when authenticated, deletes it from
+   * Firestore as well. Without the cloud deletion the realtime listeners would
+   * restore the wiped shifts on the next reload.
+   */
+  async clearAll(): Promise<void> {
+    this._state.set(EMPTY_SHIFT_DATA_STATE);
+    const auth = this.auth.state();
+    if (auth.mode === 'authenticated' && auth.uid) {
+      await this.firestore.clearShiftData(auth.uid);
+    }
+  }
+
   /** Removes a device from the cloud registry, freeing one installation slot. */
   async removeDevice(deviceId: string): Promise<void> {
     const auth = this.auth.state();