每次任务执行时用 _make_session() 创建独立的 engine + session，用完 eng.dispose() 释放，彻底避免 loop 冲突。

backend/task_scheduler/app/tasks/signin_tasks.py

@@ -26,7 +26,7 @@ from sqlalchemy import select
 
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), "../../.."))
 
-from shared.models.base import AsyncSessionLocal
+from shared.models.base import Base
 from shared.models.task import Task
 from shared.models.account import Account
 from shared.models.signin_log import SigninLog
@@ -38,6 +38,23 @@ from ..config import settings
 
 logger = logging.getLogger(__name__)
 
+
+def _make_session():
+    """
+    每次创建新的 engine + session，避免 Celery worker fork 后
+    复用主进程 event loop 绑定的连接池导致 'Future attached to a different loop' 错误。
+    """
+    from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
+    from sqlalchemy.orm import sessionmaker
+
+    engine_kwargs: dict = {"echo": False}
+    if "sqlite" not in shared_settings.DATABASE_URL:
+        engine_kwargs.update(pool_size=5, max_overflow=10, pool_pre_ping=True)
+
+    eng = create_async_engine(shared_settings.DATABASE_URL, **engine_kwargs)
+    factory = sessionmaker(eng, class_=AsyncSession, expire_on_commit=False)
+    return factory, eng
+
 WEIBO_HEADERS = {
     "User-Agent": (
         "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 "
@@ -117,7 +134,9 @@ async def _async_check_due():
     now = datetime.now()
     submitted = 0
 
-    async with AsyncSessionLocal() as session:
+    SessionFactory, eng = _make_session()
+    try:
+        async with SessionFactory() as session:
             stmt = (
                 select(Task, Account)
                 .join(Account, Task.account_id == Account.id)
@@ -126,6 +145,8 @@ async def _async_check_due():
             )
             result = await session.execute(stmt)
             pairs = result.all()
+    finally:
+        await eng.dispose()
 
     for task, account in pairs:
         try:
@@ -212,7 +233,9 @@ async def _async_do_signin(account_id: str) -> Dict[str, Any]:
     """直接操作数据库和微博 API 完成签到"""
     import httpx
 
-    async with AsyncSessionLocal() as session:
+    SessionFactory, eng = _make_session()
+    try:
+        async with SessionFactory() as session:
             stmt = select(Account).where(Account.id == account_id)
             result = await session.execute(stmt)
             account = result.scalar_one_or_none()
@@ -279,6 +302,8 @@ async def _async_do_signin(account_id: str) -> Dict[str, Any]:
                 "failed": failed,
                 "total_topics": len(topics),
             }
+    finally:
+        await eng.dispose()
 
 
 async def _fetch_topics(cookies: Dict[str, str]) -> List[dict]: