diff --git a/backend/open_webui/env.py b/backend/open_webui/env.py
index 68c4272872..5936ad9939 100644
--- a/backend/open_webui/env.py
+++ b/backend/open_webui/env.py
@@ -388,6 +388,14 @@ try:
 except ValueError:
     REDIS_RESPONSE_STREAM_TTL = 3600
 
+# Seconds a task survives without a heartbeat. 0 disables expiry.
+try:
+    REDIS_TASK_TTL = int(os.getenv('REDIS_TASK_TTL', '300'))
+    if REDIS_TASK_TTL != 0 and REDIS_TASK_TTL < 60:
+        REDIS_TASK_TTL = 300
+except ValueError:
+    REDIS_TASK_TTL = 300
+
 REDIS_SENTINEL_HOSTS = os.getenv('REDIS_SENTINEL_HOSTS', '')
 REDIS_SENTINEL_PORT = os.getenv('REDIS_SENTINEL_PORT', '26379')
 
diff --git a/backend/open_webui/main.py b/backend/open_webui/main.py
index 0e77bd4fe0..e7c2915130 100644
--- a/backend/open_webui/main.py
+++ b/backend/open_webui/main.py
@@ -74,6 +74,7 @@ from open_webui.config import (
     seed_registered_defaults,
 )
 from open_webui.constants import ERROR_MESSAGES, TASKS
+from open_webui.utils.recurrence import RecurrenceEvaluationTimeout
 from open_webui.env import (
     USE_SLIM,
     AIOHTTP_CLIENT_SESSION_SSL,
@@ -107,6 +108,7 @@ from open_webui.env import (
     MAX_BODY_LOG_SIZE,
     # Redis
     REDIS_KEY_PREFIX,
+    REDIS_TASK_TTL,
     REDIS_URL,
     RESET_CONFIG_ON_START,
     SAFE_MODE,
@@ -202,6 +204,7 @@ from open_webui.tasks import (
     list_task_ids_by_item_id,
     list_tasks,
     redis_task_command_listener,
+    redis_task_heartbeat,
     stop_item_tasks,
     stop_task,
 )  # Import from tasks.py
@@ -388,6 +391,8 @@ async def lifespan(app: FastAPI):
 
     if app.state.redis is not None:
         app.state.redis_task_command_listener = asyncio.create_task(redis_task_command_listener(app))
+        if REDIS_TASK_TTL > 0:
+            app.state.redis_task_heartbeat = asyncio.create_task(redis_task_heartbeat(app))
 
     if WEBSOCKET_MANAGER == 'redis':
         app.state.redis_event_listener = asyncio.create_task(redis_event_listener())
@@ -478,6 +483,9 @@ async def lifespan(app: FastAPI):
     if hasattr(app.state, 'redis_task_command_listener'):
         app.state.redis_task_command_listener.cancel()
 
+    if hasattr(app.state, 'redis_task_heartbeat'):
+        app.state.redis_task_heartbeat.cancel()
+
     if hasattr(app.state, 'redis_event_listener'):
         app.state.redis_event_listener.cancel()
 
@@ -503,6 +511,12 @@ app = FastAPI(
     lifespan=lifespan,
 )
 
+
+@app.exception_handler(RecurrenceEvaluationTimeout)
+async def recurrence_timeout_handler(request: Request, exc: RecurrenceEvaluationTimeout):
+    return JSONResponse(status_code=400, content={'detail': str(exc)})
+
+
 # Used by readiness checks to gate traffic until startup work is done.
 app.state.startup_complete = False
 
diff --git a/backend/open_webui/models/automations.py b/backend/open_webui/models/automations.py
index 11a906670b..8c7f6089e3 100644
--- a/backend/open_webui/models/automations.py
+++ b/backend/open_webui/models/automations.py
@@ -312,6 +312,7 @@ class AutomationTable:
             rows = result.scalars().all()
 
             from open_webui.utils.automations import next_run_ns
+            from open_webui.utils.recurrence import RecurrenceEvaluationTimeout
 
             # Batch-fetch user timezones so rescheduling respects each
             # user's local timezone instead of falling back to server time.
@@ -323,13 +324,20 @@ class AutomationTable:
                 tz_result = await db.execute(select(User.id, User.timezone).where(User.id.in_(user_ids)))
                 timezone_by_user_id = {uid: tz for uid, tz in tz_result.all()}
 
+            claimed = []
             for row in rows:
+                try:
+                    next_run_at = await next_run_ns(row.data.get('rrule', ''), tz=timezone_by_user_id.get(row.user_id))
+                except RecurrenceEvaluationTimeout:
+                    log.warning('Skipping automation %s: recurrence evaluation timed out', row.id)
+                    continue
                 row.last_run_at = now_ns
-                row.next_run_at = next_run_ns(row.data.get('rrule', ''), tz=timezone_by_user_id.get(row.user_id))
+                row.next_run_at = next_run_at
+                claimed.append(row)
 
             await db.commit()
 
-            return [AutomationModel.model_validate(r) for r in rows]
+            return [AutomationModel.model_validate(r) for r in claimed]
 
 
 ####################
diff --git a/backend/open_webui/models/calendar.py b/backend/open_webui/models/calendar.py
index 3a3147a7ad..fd7390fcea 100644
--- a/backend/open_webui/models/calendar.py
+++ b/backend/open_webui/models/calendar.py
@@ -8,7 +8,7 @@ from open_webui.constants import ERROR_MESSAGES
 from open_webui.models.access_grants import AccessGrantModel, AccessGrants
 from open_webui.models.groups import Groups
 from open_webui.models.users import User, UserModel, UserResponse
-from pydantic import BaseModel, ConfigDict, Field, field_validator
+from pydantic import BaseModel, ConfigDict, Field
 from sqlalchemy import (
     JSON,
     BigInteger,
@@ -179,6 +179,20 @@ class CalendarUpdateForm(BaseModel):
     access_grants: Optional[list[dict]] = None
 
 
+async def validate_calendar_rrule(value: Optional[str]) -> None:
+    if value:
+        from open_webui.utils.recurrence import rrule_interval_seconds
+
+        try:
+            interval = await rrule_interval_seconds(value)
+        except ValueError:
+            raise
+        except Exception as e:
+            raise ValueError(ERROR_MESSAGES.AUTOMATION_INVALID_RRULE(e)) from e
+        if interval is not None and interval < MIN_CALENDAR_RRULE_INTERVAL_SECONDS:
+            raise ValueError(ERROR_MESSAGES.CALENDAR_RRULE_TOO_FREQUENT)
+
+
 class CalendarEventForm(BaseModel):
     calendar_id: str
     title: str
@@ -193,22 +207,6 @@ class CalendarEventForm(BaseModel):
     meta: Optional[dict] = None
     attendees: Optional[list[dict]] = None
 
-    @field_validator('rrule')
-    @classmethod
-    def reject_sub_daily_rrule(cls, value: Optional[str]) -> Optional[str]:
-        if value:
-            from open_webui.utils.automations import rrule_interval_seconds
-
-            try:
-                interval = rrule_interval_seconds(value)
-            except ValueError:
-                raise
-            except Exception as e:
-                raise ValueError(ERROR_MESSAGES.AUTOMATION_INVALID_RRULE(e))
-            if interval is not None and interval < MIN_CALENDAR_RRULE_INTERVAL_SECONDS:
-                raise ValueError(ERROR_MESSAGES.CALENDAR_RRULE_TOO_FREQUENT)
-        return value
-
 
 class CalendarEventUpdateForm(BaseModel):
     calendar_id: Optional[str] = None
@@ -225,22 +223,6 @@ class CalendarEventUpdateForm(BaseModel):
     is_cancelled: Optional[bool] = None
     attendees: Optional[list[dict]] = None
 
-    @field_validator('rrule')
-    @classmethod
-    def reject_sub_daily_rrule(cls, value: Optional[str]) -> Optional[str]:
-        if value:
-            from open_webui.utils.automations import rrule_interval_seconds
-
-            try:
-                interval = rrule_interval_seconds(value)
-            except ValueError:
-                raise
-            except Exception as e:
-                raise ValueError(ERROR_MESSAGES.AUTOMATION_INVALID_RRULE(e))
-            if interval is not None and interval < MIN_CALENDAR_RRULE_INTERVAL_SECONDS:
-                raise ValueError(ERROR_MESSAGES.CALENDAR_RRULE_TOO_FREQUENT)
-        return value
-
 
 class RSVPForm(BaseModel):
     status: str  # 'accepted' | 'declined' | 'tentative' | 'pending'
@@ -465,6 +447,7 @@ class CalendarEventTable:
     async def insert_new_event(
         self, user_id: str, form_data: CalendarEventForm, db: Optional[AsyncSession] = None
     ) -> Optional[CalendarEventModel]:
+        await validate_calendar_rrule(form_data.rrule)
         async with get_async_db_context(db) as db:
             now = int(time.time_ns())
             event = CalendarEvent(
@@ -695,6 +678,7 @@ class CalendarEventTable:
     async def update_event_by_id(
         self, id: str, form_data: CalendarEventUpdateForm, db: Optional[AsyncSession] = None
     ) -> Optional[CalendarEventModel]:
+        await validate_calendar_rrule(form_data.rrule)
         async with get_async_db_context(db) as db:
             result = await db.execute(select(CalendarEvent).filter(CalendarEvent.id == id))
             event = result.scalars().first()
diff --git a/backend/open_webui/models/chats.py b/backend/open_webui/models/chats.py
index 46131dc8e9..2af71fd944 100644
--- a/backend/open_webui/models/chats.py
+++ b/backend/open_webui/models/chats.py
@@ -2536,18 +2536,15 @@ class ChatTable:
         except Exception:
             return False
 
-    async def move_chats_by_user_id_and_folder_id(
+    async def move_chats_by_folder_id(
         self,
-        user_id: str,
         folder_id: str,
         new_folder_id: str | None,
         db: AsyncSession | None = None,
     ) -> bool:
         try:
             async with get_async_db_context(db) as session:
-                await session.execute(
-                    update(Chat).filter_by(user_id=user_id, folder_id=folder_id).values(folder_id=new_folder_id)
-                )
+                await session.execute(update(Chat).filter_by(folder_id=folder_id).values(folder_id=new_folder_id))
                 await session.commit()
 
                 return True
diff --git a/backend/open_webui/routers/automations.py b/backend/open_webui/routers/automations.py
index caf8879e28..4b44a8b8ed 100644
--- a/backend/open_webui/routers/automations.py
+++ b/backend/open_webui/routers/automations.py
@@ -87,7 +87,7 @@ async def check_automation_limits(request, user, rrule_str: str, db, is_create:
     if min_interval:
         min_interval = int(min_interval)
         if min_interval > 0:
-            interval = rrule_interval_seconds(rrule_str)
+            interval = await rrule_interval_seconds(rrule_str)
             if interval is not None and interval < min_interval:
                 raise HTTPException(
                     status_code=status.HTTP_400_BAD_REQUEST,
@@ -150,7 +150,7 @@ async def enrich_automation(automation: AutomationModel, db: AsyncSession, tz: s
     return AutomationResponse(
         **automation.model_dump(),
         last_run=last_run,
-        next_runs=next_n_runs_ns(automation.data['rrule'], tz=tz),
+        next_runs=await next_n_runs_ns(automation.data['rrule'], tz=tz),
     )
 
 
@@ -216,7 +216,7 @@ async def create_new_automation(
     await check_automation_folder_access(form_data.folder_id, user, db)
     await check_automation_channel_access(form_data, user, db)
     try:
-        validate_rrule(form_data.data.rrule, tz=user.timezone)
+        await validate_rrule(form_data.data.rrule, tz=user.timezone)
     except ValueError as e:
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST,
@@ -226,7 +226,7 @@ async def create_new_automation(
     await check_automation_limits(request, user, form_data.data.rrule, db, is_create=True)
 
     tz = user.timezone
-    automation = await Automations.insert(user.id, form_data, next_run_ns(form_data.data.rrule, tz=tz), db=db)
+    automation = await Automations.insert(user.id, form_data, await next_run_ns(form_data.data.rrule, tz=tz), db=db)
     response = await enrich_automation(automation, db, tz=tz)
     await publish_event(
         request,
@@ -276,7 +276,7 @@ async def update_automation_by_id(
     await check_automation_channel_access(form_data, user, db)
 
     try:
-        validate_rrule(form_data.data.rrule, tz=user.timezone)
+        await validate_rrule(form_data.data.rrule, tz=user.timezone)
     except ValueError as e:
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST,
@@ -286,7 +286,7 @@ async def update_automation_by_id(
     await check_automation_limits(request, user, form_data.data.rrule, db, is_create=False)
 
     tz = user.timezone
-    updated = await Automations.update_by_id(id, form_data, next_run_ns(form_data.data.rrule, tz=tz), db=db)
+    updated = await Automations.update_by_id(id, form_data, await next_run_ns(form_data.data.rrule, tz=tz), db=db)
     response = await enrich_automation(updated, db, tz=tz)
     await publish_event(
         request,
@@ -313,7 +313,7 @@ async def toggle_automation_by_id(
     await check_automations_permission(request, user)
     automation = await Automations.get_by_id(id, db=db)
     check_automation_access(automation, user)
-    toggled = await Automations.toggle(id, next_run_ns(automation.data['rrule'], tz=user.timezone), db=db)
+    toggled = await Automations.toggle(id, await next_run_ns(automation.data['rrule'], tz=user.timezone), db=db)
     response = await enrich_automation(toggled, db, tz=user.timezone)
     await publish_event(
         request,
diff --git a/backend/open_webui/routers/calendar.py b/backend/open_webui/routers/calendar.py
index f95be48e84..86d9824803 100644
--- a/backend/open_webui/routers/calendar.py
+++ b/backend/open_webui/routers/calendar.py
@@ -273,7 +273,10 @@ async def get_events(
 async def create_event(request: Request, form_data: CalendarEventForm, user: UserModel = Depends(get_verified_user)):
     await check_calendar_permission(request, user)
     await _check_calendar_access(form_data.calendar_id, user, 'write')
-    event = await CalendarEvents.insert_new_event(user.id, form_data)
+    try:
+        event = await CalendarEvents.insert_new_event(user.id, form_data)
+    except ValueError as e:
+        raise HTTPException(status_code=422, detail=str(e)) from e
     await publish_event(
         request,
         EVENTS.CALENDAR_EVENT_CREATED,
@@ -325,7 +328,10 @@ async def update_event(
     if form_data.calendar_id is not None and form_data.calendar_id != event.calendar_id:
         await _check_calendar_access(form_data.calendar_id, user, 'write')
 
-    updated = await CalendarEvents.update_event_by_id(event_id, form_data)
+    try:
+        updated = await CalendarEvents.update_event_by_id(event_id, form_data)
+    except ValueError as e:
+        raise HTTPException(status_code=422, detail=str(e)) from e
     if not updated:
         raise HTTPException(status_code=500, detail='Failed to update')
     await publish_event(
diff --git a/backend/open_webui/routers/folders.py b/backend/open_webui/routers/folders.py
index 9653a6d9b8..046a2d8834 100644
--- a/backend/open_webui/routers/folders.py
+++ b/backend/open_webui/routers/folders.py
@@ -704,8 +704,8 @@ async def delete_folder_by_id(
                 for folder_id in folder_ids:
                     if delete_contents:
                         await Chats.delete_chats_by_user_id_and_folder_id(folder_owner_id, folder_id, db=db)
-                    else:
-                        await Chats.move_chats_by_user_id_and_folder_id(folder_owner_id, folder_id, None, db=db)
+
+                    await Chats.move_chats_by_folder_id(folder_id, None, db=db)
 
                     # Clean up access grants for this folder
                     await AccessGrants.revoke_all_access('folder', folder_id, db=db)
diff --git a/backend/open_webui/tasks.py b/backend/open_webui/tasks.py
index 322cd32e60..05f622ef06 100644
--- a/backend/open_webui/tasks.py
+++ b/backend/open_webui/tasks.py
@@ -6,7 +6,7 @@ from uuid import uuid4
 
 from redis.asyncio import Redis
 
-from open_webui.env import REDIS_KEY_PREFIX, REDIS_RESPONSE_STREAM_TTL
+from open_webui.env import REDIS_KEY_PREFIX, REDIS_RESPONSE_STREAM_TTL, REDIS_TASK_TTL
 from open_webui.utils.json_codec import JSONCodec, dumps_bytes
 
 log = logging.getLogger(__name__)
@@ -66,13 +66,28 @@ async def redis_task_command_listener(app):
         reconnect_interval = min(reconnect_interval * 2, REDIS_PUBSUB_MAX_RECONNECT_INTERVAL)
 
 
+async def redis_task_heartbeat(app):
+    redis: Redis = app.state.redis
+    while True:
+        await asyncio.sleep(REDIS_TASK_TTL / 4)
+        try:
+            pipe = redis.pipeline(transaction=False)
+            for task_id in list(tasks):
+                # EXPIRE cannot recreate a task already removed by cleanup.
+                pipe.expire(f'{REDIS_TASKS_KEY}:{task_id}', REDIS_TASK_TTL)
+            await pipe.execute()
+        except Exception:
+            log.exception('Redis task heartbeat failed')
+
+
 ### ------------------------------
 ### REDIS-ENABLED HANDLERS
 ### ------------------------------
 
 
 async def redis_save_task(redis: Redis, task_id: str, item_id: str | None):
-    pipe = redis.pipeline()
+    pipe = redis.pipeline(transaction=False)
+    pipe.set(f'{REDIS_TASKS_KEY}:{task_id}', '1', ex=REDIS_TASK_TTL or None)
     pipe.hset(REDIS_TASKS_KEY, task_id, item_id or '')
     if item_id:
         pipe.sadd(f'{REDIS_ITEM_TASKS_KEY}:{item_id}', task_id)
@@ -80,25 +95,36 @@ async def redis_save_task(redis: Redis, task_id: str, item_id: str | None):
 
 
 async def redis_cleanup_task(redis: Redis, task_id: str, item_id: str | None):
-    pipe = redis.pipeline()
+    pipe = redis.pipeline(transaction=False)
+    pipe.delete(f'{REDIS_TASKS_KEY}:{task_id}')
     pipe.hdel(REDIS_TASKS_KEY, task_id)
     pipe.hdel(REDIS_RESPONSE_STREAMS_KEY, task_id)
     if item_id:
         pipe.srem(f'{REDIS_ITEM_TASKS_KEY}:{item_id}', task_id)
-        await pipe.execute()
-        # Remove the set key entirely if no tasks remain for this item
-        if await redis.scard(f'{REDIS_ITEM_TASKS_KEY}:{item_id}') == 0:
-            await redis.delete(f'{REDIS_ITEM_TASKS_KEY}:{item_id}')
-    else:
-        await pipe.execute()
+    await pipe.execute()
 
 
-async def redis_list_tasks(redis: Redis) -> list[str]:
-    return list(await redis.hkeys(REDIS_TASKS_KEY))
+async def redis_list_tasks(redis: Redis, item_id: str | None = None) -> list[str]:
+    task_ids = list(
+        await redis.smembers(f'{REDIS_ITEM_TASKS_KEY}:{item_id}')
+        if item_id is not None
+        else await redis.hkeys(REDIS_TASKS_KEY)
+    )
+    if not task_ids or REDIS_TASK_TTL == 0:
+        return task_ids
 
+    pipe = redis.pipeline(transaction=False)
+    for task_id in task_ids:
+        pipe.exists(f'{REDIS_TASKS_KEY}:{task_id}')
 
-async def redis_list_item_tasks(redis: Redis, item_id: str) -> list[str]:
-    return list(await redis.smembers(f'{REDIS_ITEM_TASKS_KEY}:{item_id}'))
+    active = []
+    for task_id, exists in zip(task_ids, await pipe.execute()):
+        if exists:
+            active.append(task_id)
+        else:
+            task_item_id = item_id if item_id is not None else await redis.hget(REDIS_TASKS_KEY, task_id)
+            await redis_cleanup_task(redis, task_id, task_item_id or None)
+    return active
 
 
 async def redis_send_command(redis: Redis, command: dict):
@@ -166,7 +192,7 @@ async def list_task_ids_by_item_id(redis, id):
     List all tasks associated with a specific ID.
     """
     if redis:
-        return await redis_list_item_tasks(redis, id)
+        return await redis_list_tasks(redis, id)
     return list(item_tasks.get(id, []))
 
 
diff --git a/backend/open_webui/tools/builtin.py b/backend/open_webui/tools/builtin.py
index 8dedd75c13..d80884d1cd 100644
--- a/backend/open_webui/tools/builtin.py
+++ b/backend/open_webui/tools/builtin.py
@@ -3768,7 +3768,7 @@ async def create_automation(
 
         # Validate the RRULE
         try:
-            validate_rrule(rrule, tz=user.timezone)
+            await validate_rrule(rrule, tz=user.timezone)
         except ValueError as e:
             return JSONCodec.dumps({'error': f'Invalid schedule: {e}'})
 
@@ -3794,7 +3794,7 @@ async def create_automation(
             is_active=True,
         )
 
-        automation = await Automations.insert(user_id, form, next_run_ns(rrule, tz=tz))
+        automation = await Automations.insert(user_id, form, await next_run_ns(rrule, tz=tz))
 
         return JSONCodec.dumps(
             {
@@ -3805,7 +3805,7 @@ async def create_automation(
                 'model_id': model_id,
                 'target': automation.data.get('target'),
                 'is_active': automation.is_active,
-                'next_runs': next_n_runs_ns(rrule, tz=tz),
+                'next_runs': await next_n_runs_ns(rrule, tz=tz),
             },
             ensure_ascii=False,
         )
@@ -3876,7 +3876,7 @@ async def update_automation(
         # Validate RRULE if changed
         if rrule is not None:
             try:
-                validate_rrule(new_rrule, tz=user.timezone)
+                await validate_rrule(new_rrule, tz=user.timezone)
             except ValueError as e:
                 return JSONCodec.dumps({'error': f'Invalid schedule: {e}'})
 
@@ -3898,7 +3898,7 @@ async def update_automation(
             is_active=automation.is_active,
         )
 
-        updated = await Automations.update_by_id(automation_id, form, next_run_ns(new_rrule, tz=tz))
+        updated = await Automations.update_by_id(automation_id, form, await next_run_ns(new_rrule, tz=tz))
 
         return JSONCodec.dumps(
             {
@@ -3909,7 +3909,7 @@ async def update_automation(
                 'model_id': new_model_id,
                 'target': updated.data.get('target'),
                 'is_active': updated.is_active,
-                'next_runs': next_n_runs_ns(new_rrule, tz=tz),
+                'next_runs': await next_n_runs_ns(new_rrule, tz=tz),
             },
             ensure_ascii=False,
         )
@@ -3977,7 +3977,7 @@ async def list_automations(
                     'rrule': rrule,
                     'is_active': item.is_active,
                     'last_run_at': item.last_run_at,
-                    'next_runs': next_n_runs_ns(rrule, tz=user.timezone if user else None),
+                    'next_runs': await next_n_runs_ns(rrule, tz=user.timezone if user else None),
                 }
             )
 
@@ -4024,7 +4024,7 @@ async def toggle_automation(
         rrule = automation.data.get('rrule', '')
         toggled = await Automations.toggle(
             automation_id,
-            next_run_ns(rrule, tz=user.timezone if user else None),
+            await next_run_ns(rrule, tz=user.timezone if user else None),
         )
 
         return JSONCodec.dumps(
diff --git a/backend/open_webui/utils/automations.py b/backend/open_webui/utils/automations.py
index 557e84ce13..54887467c0 100644
--- a/backend/open_webui/utils/automations.py
+++ b/backend/open_webui/utils/automations.py
@@ -20,12 +20,10 @@ import logging
 import os
 import random
 import time
-from datetime import datetime, timedelta
+from datetime import timedelta
 from typing import Optional
 from uuid import uuid4
-from zoneinfo import ZoneInfo
 
-from dateutil.rrule import HOURLY, MINUTELY, SECONDLY, rruleset, rrulestr
 from fastapi import Request
 from fastapi.security import HTTPAuthorizationCredentials
 from open_webui.constants import ERROR_MESSAGES
@@ -39,6 +37,13 @@ from open_webui.models.messages import MessageForm
 from open_webui.models.users import Users
 from open_webui.utils.auth import create_token
 from open_webui.utils.misc import parse_duration
+from open_webui.utils.recurrence import (
+    _resolve_tz,
+    next_n_runs_ns,
+    next_run_ns,
+    rrule_interval_seconds,
+    validate_rrule,
+)
 from open_webui.utils.task import prompt_template
 from open_webui.utils.terminals import get_terminal_server_url
 from starlette.datastructures import Headers
@@ -50,151 +55,6 @@ TIMER_POLL_INTERVAL = int(os.getenv('TIMER_POLL_INTERVAL', '1'))
 CALENDAR_ALERT_LOOKAHEAD_MINUTES = int(os.getenv('CALENDAR_ALERT_LOOKAHEAD_MINUTES', '10'))
 
 
-####################
-# RRULE Helpers
-####################
-
-
-def _resolve_tz(tz: str = None) -> Optional[ZoneInfo]:
-    """Safely resolve a timezone string to ZoneInfo.
-
-    Returns None (→ server-local fallback) when *tz* is empty, None,
-    or an unrecognised IANA key.  Logs a warning on bad keys so
-    misconfiguration is visible in the server logs.
-    """
-    if not tz:
-        return None
-    try:
-        return ZoneInfo(tz)
-    except (KeyError, Exception):
-        log.warning('Unknown timezone %r — falling back to server time', tz)
-        return None
-
-
-def _parse_rule(s: str, now: Optional[datetime] = None):
-    """Parse RRULE with clock-aligned DTSTART for sub-daily frequencies.
-
-    SECONDLY/MINUTELY/HOURLY rules use a fixed epoch DTSTART (2000-01-01 00:00)
-    so intervals snap to clock boundaries (e.g. every 5min = :00, :05, :10).
-    """
-    upper = s.upper()
-    if 'EXRULE' in upper:
-        raise ValueError('EXRULE is not supported in recurrence rules')
-
-    parsed = rrulestr(s, ignoretz=True)
-    rules = parsed._rrule if isinstance(parsed, rruleset) else [parsed]
-    if len(rules) > 1:
-        raise ValueError('only one RRULE is supported per recurrence rule')
-
-    rule = rules[0]
-    start = rule._dtstart.replace(tzinfo=None)
-    anchor = now or datetime.now()
-    parts = s.split()
-    stripped = '\n'.join(part for part in parts if not part.upper().startswith('DTSTART')) or s
-    has_dtstart = any(part.upper().startswith('DTSTART') for part in parts)
-    step = {
-        SECONDLY: timedelta(seconds=rule._interval),
-        MINUTELY: timedelta(minutes=rule._interval),
-        HOURLY: timedelta(hours=rule._interval),
-    }.get(rule._freq)
-
-    if step is None:
-        if not rule._dtstart.tzinfo:
-            return parsed
-        return rrulestr(stripped, dtstart=start, ignoretz=True)
-
-    if rule._interval < 1:
-        raise ValueError('RRULE INTERVAL must be a positive integer')
-    dtstart = None
-    if has_dtstart:
-        emitted = ((anchor - start) // step) if anchor > start else 0
-        emitted *= len(rule._byminute or (0,)) * len(rule._bysecond or (0,))
-        if emitted <= 100_000:
-            if rule._dtstart.tzinfo:
-                dtstart = start
-            else:
-                return parsed
-    if not has_dtstart or dtstart is None:
-        epoch = datetime(2000, 1, 1)
-        dtstart = epoch + ((anchor - epoch) // step) * step
-
-    return rrulestr(stripped, dtstart=dtstart, ignoretz=True)
-
-
-def validate_rrule(s: str, tz: str = None) -> None:
-    """Raise ValueError if the RRULE is malformed or exhausted.
-
-    When *tz* is provided the "now" reference uses the user's local
-    clock so that near-future schedules are not incorrectly rejected
-    on servers whose system clock is ahead (e.g. UTC vs US timezones).
-    """
-    upper = s.upper()
-    if 'COUNT=' in upper and 'DTSTART' not in upper:
-        raise ValueError(ERROR_MESSAGES.AUTOMATION_COUNT_REQUIRES_DTSTART)
-    zi = _resolve_tz(tz)
-    now = datetime.now(zi).replace(tzinfo=None) if zi else datetime.now()
-    try:
-        rule = _parse_rule(s, now)
-    except Exception as e:
-        raise ValueError(ERROR_MESSAGES.AUTOMATION_INVALID_RRULE(e))
-    if rule.after(now) is None:
-        raise ValueError(ERROR_MESSAGES.AUTOMATION_NO_FUTURE_RUNS)
-
-
-def next_run_ns(s: str, tz: str = None) -> Optional[int]:
-    """Next occurrence as epoch nanoseconds, respecting user timezone."""
-    zi = _resolve_tz(tz)
-    now = datetime.now(zi) if zi else datetime.now()
-    now_naive = now.replace(tzinfo=None)
-    dt = _parse_rule(s, now_naive).after(now_naive)
-    if dt is None:
-        return None
-    if zi:
-        dt = dt.replace(tzinfo=zi)
-    return int(dt.timestamp() * 1_000_000_000)
-
-
-def next_n_runs_ns(s: str, n: int = 5, tz: str = None) -> list[int]:
-    """Compute next N occurrences for UI preview.
-
-    Uses the user's timezone for the starting "now" so that the
-    preview matches the user's local clock (same as next_run_ns).
-    """
-    zi = _resolve_tz(tz)
-    result = []
-    now = datetime.now(zi).replace(tzinfo=None) if zi else datetime.now()
-    rule = _parse_rule(s, now)
-    dt = now
-    for _ in range(n):
-        dt = rule.after(dt)
-        if not dt:
-            break
-        if zi:
-            dt_tz = dt.replace(tzinfo=zi)
-            result.append(int(dt_tz.timestamp() * 1_000_000_000))
-        else:
-            result.append(int(dt.timestamp() * 1_000_000_000))
-    return result
-
-
-def rrule_interval_seconds(s: str) -> Optional[int]:
-    """Approximate interval between recurrences in seconds.
-
-    Returns None for one-shot (COUNT=1) schedules or rules
-    with fewer than two future occurrences.
-    """
-    s = '\n'.join(part for part in s.split() if not part.upper().startswith('DTSTART')) or s
-    now = datetime.now()
-    rule = _parse_rule(s, now)
-    first = rule.after(now)
-    if first is None:
-        return None
-    second = rule.after(first)
-    if second is None:
-        return None
-    return int((second - first).total_seconds())
-
-
 ############################
 # Worker Loop
 ############################
diff --git a/backend/open_webui/utils/recurrence.py b/backend/open_webui/utils/recurrence.py
new file mode 100644
index 0000000000..d5c2b6b1f2
--- /dev/null
+++ b/backend/open_webui/utils/recurrence.py
@@ -0,0 +1,171 @@
+"""Recurrence calculations isolated from application/DB imports for worker processes."""
+
+import logging
+from datetime import datetime, timedelta
+from typing import Optional
+from zoneinfo import ZoneInfo
+
+from anyio import fail_after, to_process
+from dateutil.rrule import HOURLY, MINUTELY, SECONDLY, rruleset, rrulestr
+from open_webui.constants import ERROR_MESSAGES
+
+log = logging.getLogger(__name__)
+RRULE_TIMEOUT_SECONDS = 2
+
+
+class RecurrenceEvaluationTimeout(ValueError):
+    """The evaluation budget expired; the schedule may still have occurrences."""
+
+
+def _resolve_tz(tz: str = None) -> Optional[ZoneInfo]:
+    """Safely resolve a timezone string to ZoneInfo.
+
+    Returns None (→ server-local fallback) when *tz* is empty, None,
+    or an unrecognised IANA key.  Logs a warning on bad keys so
+    misconfiguration is visible in the server logs.
+    """
+    if not tz:
+        return None
+    try:
+        return ZoneInfo(tz)
+    except (KeyError, Exception):
+        log.warning('Unknown timezone %r — falling back to server time', tz)
+        return None
+
+
+def _parse_rule(s: str, now: Optional[datetime] = None):
+    """Parse RRULE with clock-aligned DTSTART for sub-daily frequencies.
+
+    SECONDLY/MINUTELY/HOURLY rules use a fixed epoch DTSTART (2000-01-01 00:00)
+    so intervals snap to clock boundaries (e.g. every 5min = :00, :05, :10).
+    """
+    upper = s.upper()
+    if 'EXRULE' in upper:
+        raise ValueError('EXRULE is not supported in recurrence rules')
+
+    parsed = rrulestr(s, ignoretz=True)
+    rules = parsed._rrule if isinstance(parsed, rruleset) else [parsed]
+    if len(rules) > 1:
+        raise ValueError('only one RRULE is supported per recurrence rule')
+
+    rule = rules[0]
+    start = rule._dtstart.replace(tzinfo=None)
+    anchor = now or datetime.now()
+    parts = s.split()
+    stripped = '\n'.join(part for part in parts if not part.upper().startswith('DTSTART')) or s
+    has_dtstart = any(part.upper().startswith('DTSTART') for part in parts)
+    step = {
+        SECONDLY: timedelta(seconds=rule._interval),
+        MINUTELY: timedelta(minutes=rule._interval),
+        HOURLY: timedelta(hours=rule._interval),
+    }.get(rule._freq)
+
+    if step is None:
+        if not rule._dtstart.tzinfo:
+            return parsed
+        return rrulestr(stripped, dtstart=start, ignoretz=True)
+
+    if rule._interval < 1:
+        raise ValueError('RRULE INTERVAL must be a positive integer')
+    dtstart = None
+    if has_dtstart:
+        emitted = ((anchor - start) // step) if anchor > start else 0
+        emitted *= len(rule._byminute or (0,)) * len(rule._bysecond or (0,))
+        if emitted <= 100_000:
+            if rule._dtstart.tzinfo:
+                dtstart = start
+            else:
+                return parsed
+    if not has_dtstart or dtstart is None:
+        epoch = datetime(2000, 1, 1)
+        dtstart = epoch + ((anchor - epoch) // step) * step
+
+    return rrulestr(stripped, dtstart=dtstart, ignoretz=True)
+
+
+def _next_occurrences(s: str, now: datetime, n: int) -> list[datetime]:
+    rule = _parse_rule(s, now)
+    occurrences = []
+    for _ in range(n):
+        now = rule.after(now)
+        if now is None:
+            break
+        occurrences.append(now)
+    return occurrences
+
+
+async def _get_next_occurrences(s: str, now: datetime, n: int) -> list[datetime]:
+    # A result-count or date limit cannot bound work before the first match.
+    try:
+        with fail_after(RRULE_TIMEOUT_SECONDS):
+            return await to_process.run_sync(_next_occurrences, s, now, n, cancellable=True)
+    except TimeoutError as e:
+        raise RecurrenceEvaluationTimeout('Schedule took too long to evaluate; simplify its recurrence rule.') from e
+
+
+async def validate_rrule(s: str, tz: str = None) -> None:
+    """Raise ValueError if the RRULE is malformed or exhausted.
+
+    When *tz* is provided the "now" reference uses the user's local
+    clock so that near-future schedules are not incorrectly rejected
+    on servers whose system clock is ahead (e.g. UTC vs US timezones).
+    """
+    upper = s.upper()
+    if 'COUNT=' in upper and 'DTSTART' not in upper:
+        raise ValueError(ERROR_MESSAGES.AUTOMATION_COUNT_REQUIRES_DTSTART)
+    zi = _resolve_tz(tz)
+    now = datetime.now(zi).replace(tzinfo=None) if zi else datetime.now()
+    try:
+        occurrences = await _get_next_occurrences(s, now, 1)
+    except RecurrenceEvaluationTimeout:
+        raise
+    except Exception as e:
+        raise ValueError(ERROR_MESSAGES.AUTOMATION_INVALID_RRULE(e))
+    if not occurrences:
+        raise ValueError(ERROR_MESSAGES.AUTOMATION_NO_FUTURE_RUNS)
+
+
+async def next_run_ns(s: str, tz: str = None) -> Optional[int]:
+    """Next occurrence as epoch nanoseconds, respecting user timezone."""
+    zi = _resolve_tz(tz)
+    now = datetime.now(zi) if zi else datetime.now()
+    now_naive = now.replace(tzinfo=None)
+    occurrences = await _get_next_occurrences(s, now_naive, 1)
+    if not occurrences:
+        return None
+    dt = occurrences[0]
+    if zi:
+        dt = dt.replace(tzinfo=zi)
+    return int(dt.timestamp() * 1_000_000_000)
+
+
+async def next_n_runs_ns(s: str, n: int = 5, tz: str = None) -> list[int]:
+    """Compute next N occurrences for UI preview.
+
+    Uses the user's timezone for the starting "now" so that the
+    preview matches the user's local clock (same as next_run_ns).
+    """
+    zi = _resolve_tz(tz)
+    result = []
+    now = datetime.now(zi).replace(tzinfo=None) if zi else datetime.now()
+    for dt in await _get_next_occurrences(s, now, n):
+        if zi:
+            dt_tz = dt.replace(tzinfo=zi)
+            result.append(int(dt_tz.timestamp() * 1_000_000_000))
+        else:
+            result.append(int(dt.timestamp() * 1_000_000_000))
+    return result
+
+
+async def rrule_interval_seconds(s: str) -> Optional[int]:
+    """Approximate interval between recurrences in seconds.
+
+    Returns None for one-shot (COUNT=1) schedules or rules
+    with fewer than two future occurrences.
+    """
+    s = '\n'.join(part for part in s.split() if not part.upper().startswith('DTSTART')) or s
+    now = datetime.now()
+    occurrences = await _get_next_occurrences(s, now, 2)
+    if len(occurrences) < 2:
+        return None
+    return int((occurrences[1] - occurrences[0]).total_seconds())