test_async_command_adds_messages() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_model_call_state_update.py lines 253–279

    async def test_async_command_adds_messages(self) -> None:
        """awrap_model_call command adds messages alongside model response."""

        class AsyncAddMiddleware(AgentMiddleware):
            async def awrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], Awaitable[ModelResponse]],
            ) -> ExtendedModelResponse:
                response = await handler(request)
                custom = HumanMessage(content="Async custom", id="async-custom")
                return ExtendedModelResponse(
                    model_response=response,
                    command=Command(update={"messages": [custom]}),
                )

        model = GenericFakeChatModel(messages=iter([AIMessage(content="Async hello!")]))
        agent = create_agent(model=model, middleware=[AsyncAddMiddleware()])

        result = await agent.ainvoke({"messages": [HumanMessage(content="Hi")]})

        # Both model response and command messages are present (additive)
        messages = result["messages"]
        assert len(messages) == 3
        assert messages[0].content == "Hi"
        assert messages[1].content == "Async hello!"
        assert messages[2].content == "Async custom"