fix(agent): map closed database worker to 503

tests/test_api_response.py

@@ -23,7 +23,10 @@ from app.factory import (
     localized_unhandled_exception_handler,
     localized_validation_exception_handler,
 )
-from app.application.database import DatabaseWorkerOverloadedError
+from app.application.database import (
+    DatabaseWorkerClosedError,
+    DatabaseWorkerOverloadedError,
+)
 from app.runtime.localization import LocaleHelper
 from app.runtime.config import settings
 from app.schemas.common import JsonData
@@ -67,6 +70,10 @@ def api_app() -> FastAPI:
         DatabaseWorkerOverloadedError,
         database_worker_overloaded_handler,
     )
+    app.add_exception_handler(
+        DatabaseWorkerClosedError,
+        database_worker_overloaded_handler,
+    )
     from fastapi.exceptions import RequestValidationError
 
     app.add_exception_handler(
@@ -125,6 +132,11 @@ def api_app() -> FastAPI:
         """模拟数据库短事务容量耗尽。"""
         raise DatabaseWorkerOverloadedError("worker full")
 
+    @app.get("/database-closed")
+    async def get_database_closed() -> None:
+        """模拟数据库 worker 在关闭态拒绝新任务。"""
+        raise DatabaseWorkerClosedError("worker closed")
+
     @app.get("/native", response_model=None)
     async def get_native_response() -> dict[str, bool]:
         """返回显式旁路的原生 JSON 协议。"""
@@ -219,6 +231,22 @@ async def test_database_worker_overload_is_retryable_service_unavailable(
     }
 
 
+async def test_database_worker_closed_is_retryable_service_unavailable(
+        api_app: FastAPI,
+):
+    """数据库 worker 关闭态应返回 503，而不是落入通用 500。"""
+    async with make_client(api_app) as client:
+        response = await client.get("/database-closed")
+
+    assert response.status_code == 503
+    assert response.headers["retry-after"] == "1"
+    assert response.json() == {
+        "success": False,
+        "message": "服务当前繁忙，请稍后重试",
+        "data": None,
+    }
+
+
 @pytest.mark.parametrize(
     "path",
     [