test_inner_command_propagated_through_composition() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_model_call_state_update.py lines 374–425

    def test_inner_command_propagated_through_composition(self) -> None:
        """Inner middleware's ExtendedModelResponse command is propagated.

        When inner middleware returns ExtendedModelResponse, its command is
        captured before normalizing to ModelResponse at the composition boundary
        and collected into the final result.
        """

        class OuterMiddleware(AgentMiddleware):
            def wrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], ModelResponse],
            ) -> ModelResponse:
                # Outer sees a ModelResponse from handler (inner's ExtendedModelResponse
                # was normalized at the composition boundary)
                response = handler(request)
                assert isinstance(response, ModelResponse)
                return response

        class InnerMiddleware(AgentMiddleware):
            def wrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], ModelResponse],
            ) -> ExtendedModelResponse:
                response = handler(request)
                return ExtendedModelResponse(
                    model_response=response,
                    command=Command(
                        update={
                            "messages": [
                                HumanMessage(content="Inner msg", id="inner"),
                            ]
                        }
                    ),
                )

        model = GenericFakeChatModel(messages=iter([AIMessage(content="Hello")]))
        agent = create_agent(
            model=model,
            middleware=[OuterMiddleware(), InnerMiddleware()],
        )

        result = agent.invoke({"messages": [HumanMessage("Hi")]})

        # Model messages + inner command messages (additive)
        messages = result["messages"]
        assert len(messages) == 3
        assert messages[0].content == "Hi"
        assert messages[1].content == "Hello"
        assert messages[2].content == "Inner msg"