test_outer_command_messages_added_alongside_model() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_model_call_state_update.py lines 320–372

    def test_outer_command_messages_added_alongside_model(self) -> None:
        """Outer middleware's command messages are added alongside model messages."""
        execution_order: list[str] = []

        class OuterMiddleware(AgentMiddleware):
            def wrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], ModelResponse],
            ) -> ExtendedModelResponse:
                execution_order.append("outer-before")
                response = handler(request)
                execution_order.append("outer-after")
                return ExtendedModelResponse(
                    model_response=response,
                    command=Command(
                        update={"messages": [HumanMessage(content="Outer msg", id="outer-msg")]}
                    ),
                )

        class InnerMiddleware(AgentMiddleware):
            def wrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], ModelResponse],
            ) -> ModelResponse:
                execution_order.append("inner-before")
                response = handler(request)
                execution_order.append("inner-after")
                return response

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

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

        # Execution order: outer wraps inner
        assert execution_order == [
            "outer-before",
            "inner-before",
            "inner-after",
            "outer-after",
        ]

        # Model messages + outer command messages (additive)
        messages = result["messages"]
        assert len(messages) == 3
        assert messages[0].content == "Hi"
        assert messages[1].content == "Composed"
        assert messages[2].content == "Outer msg"