diff --git a/src/api/toolchain_routes.py b/src/api/toolchain_routes.py
index e8c1e92..39ed51d 100644
--- a/src/api/toolchain_routes.py
+++ b/src/api/toolchain_routes.py
@@ -50,7 +50,15 @@ router = APIRouter(tags=["toolchain"])
 _delivery_cache: Set[str] = set()
 _delivery_timestamps: List[Tuple[float, str]] = []
 _TTL_SECONDS = 7 * 24 * 3600
-_idempotency_lock = asyncio.Lock()
+_idempotency_lock: Optional[asyncio.Lock] = None
+
+
+def _get_idempotency_lock() -> asyncio.Lock:
+    """懒加载 asyncio.Lock，避免模块级创建时 event loop 不存在（Python 3.9）。"""
+    global _idempotency_lock
+    if _idempotency_lock is None:
+        _idempotency_lock = asyncio.Lock()
+    return _idempotency_lock
 
 
 def _is_duplicate(event: str, delivery: str,
@@ -1219,7 +1227,7 @@ async def gitea_webhook(
 
     # 2. 幂等检查（需要在 payload 解析后，以支持内容去重）
     if x_gitea_event and x_gitea_delivery:
-        async with _idempotency_lock:
+        async with _get_idempotency_lock():
             if _is_duplicate(x_gitea_event, x_gitea_delivery, payload):
                 logger.debug(
                     "Duplicate webhook: %s/%s",