diff --git a/web/routers/tasks.py b/web/routers/tasks.py
index e26b54b..a8beef5 100644
--- a/web/routers/tasks.py
+++ b/web/routers/tasks.py
@@ -12,6 +12,7 @@
 这些端点读写 core.state 的共享任务表（与任务执行侧同一批对象），因此
 看到的是同一份任务状态。
 """
+import asyncio
 import time
 from typing import Annotated, Any
 
@@ -27,6 +28,7 @@ from core.state import (
     REQUEST_STATS,
     STATS_LOCK,
 )
+from services import tasks as services_tasks
 from web import ratelimit
 from web.deps import SiteUser, require_login
 from web.request_utils import (
@@ -40,18 +42,6 @@ LoginUser = Annotated[SiteUser, Depends(require_login)]
 
 
 
-def _touch_device(device_id: str) -> None:
-    """记录设备心跳（与 core.state 的 DEVICE_LAST_SEEN 共享）。"""
-    device_id = str(device_id or '')[:64]
-    if not device_id:
-        return
-    with DEVICE_LAST_SEEN_LOCK:
-        if len(DEVICE_LAST_SEEN) >= 5000:
-            for d in sorted(DEVICE_LAST_SEEN, key=lambda k: DEVICE_LAST_SEEN.get(k, 0.0))[:2500]:
-                DEVICE_LAST_SEEN.pop(d, None)
-        DEVICE_LAST_SEEN[device_id] = time.time()
-
-
 def _owned_by(task: dict[str, Any], user: SiteUser) -> bool:
     return int(task.get('user_id') or 0) == int(user.id)
 
@@ -183,7 +173,7 @@ async def task_heartbeat(user: LoginUser, request: Request):
     device_id = str(data.get('device_id') or '').strip()[:64]
     if not device_id:
         return error('缺少 device_id 参数')
-    _touch_device(device_id)
+    await asyncio.to_thread(services_tasks._touch_device, device_id)
     resumed = 0
     with DOWNLOAD_TASKS_LOCK:
         for task in DOWNLOAD_TASKS.values():
@@ -209,7 +199,7 @@ async def task_list(user: LoginUser, request: Request):
     device_id = str(data.get('device_id') or '').strip()[:64]
     if not device_id:
         return error('缺少 device_id 参数')
-    _touch_device(device_id)
+    await asyncio.to_thread(services_tasks._touch_device, device_id)
     my_tasks = []
     with DOWNLOAD_TASKS_LOCK:
         for tid, task in DOWNLOAD_TASKS.items():