diff --git a/backend/app/backend.py b/backend/app/backend.py
index 6c919a7..22431e2 100644
--- a/backend/app/backend.py
+++ b/backend/app/backend.py
@@ -44,8 +44,8 @@ async def lifespan(app: FastAPI):
         agent_service = AIAgentService(checkpointer)
         await agent_service.initialize()
         
-        # 3. 创建历史查询服务
-        history_service = ThreadHistoryService(checkpointer.conn)
+        # 3. 创建历史查询服务（保持原有的 checkpointer 参数）
+        history_service = ThreadHistoryService(checkpointer)
         
         # 3.5 创建子图 Repositories
         contact_repo = ContactRepository(checkpointer.conn)