test_sync_dynamic_prompt_on_async_invoke() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_decorators.py lines 800–822

async def test_sync_dynamic_prompt_on_async_invoke() -> None:
    """Test that sync dynamic_prompt works when invoked via async path (.ainvoke).

    When a sync middleware is defined with @dynamic_prompt, it automatically creates
    both sync and async implementations. The async implementation delegates to the
    sync function, allowing the middleware to work in both sync and async contexts.
    """
    calls = []

    @dynamic_prompt
    def sync_prompt(request: ModelRequest) -> str:
        calls.append("sync_prompt")
        return "Sync prompt"

    agent = create_agent(model=FakeToolCallingModel(), middleware=[sync_prompt])

    # Sync dynamic_prompt now works in async path via delegation
    result = await agent.ainvoke({"messages": [HumanMessage("Hello")]})

    # The sync prompt function was called via async delegation
    assert calls == ["sync_prompt"]
    # The model executed with the custom prompt
    assert result["messages"][-1].content == "Sync prompt-Hello"