UserContextMiddleware Class — langchain Architecture

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware_typing/test_middleware_typing.py lines 116–134

class UserContextMiddleware(AgentMiddleware[AgentState[Any], UserContext, Any]):
    """Middleware with correctly specified UserContext."""

    def before_model(
        self, state: AgentState[Any], runtime: Runtime[UserContext]
    ) -> dict[str, Any] | None:
        # Full type safety - IDE knows these fields exist
        _user_id: str = runtime.context["user_id"]
        _user_name: str = runtime.context["user_name"]
        return None

    def wrap_model_call(
        self,
        request: ModelRequest[UserContext],  # Correctly parameterized!
        handler: Callable[[ModelRequest[UserContext]], ModelResponse[Any]],
    ) -> ModelResponse[Any]:
        # request.runtime.context is UserContext - fully typed!
        _user_id: str = request.runtime.context["user_id"]
        return handler(request)