test_wrap_tool_call_outer_intercepts_inner() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_tool_call.py lines 558–615

def test_wrap_tool_call_outer_intercepts_inner() -> None:
    """Test composition where outer middleware intercepts inner response."""
    call_log = []

    @wrap_tool_call(name="InterceptingOuter")
    def intercepting_outer(
        request: ToolCallRequest, handler: Callable[[ToolCallRequest], ToolMessage | Command[Any]]
    ) -> ToolMessage | Command[Any]:
        call_log.append("outer_before")
        handler(request)
        call_log.append("outer_after")

        # Return modified message
        return ToolMessage(
            content="Outer intercepted",
            tool_call_id=request.tool_call["id"],
            name=request.tool_call["name"],
        )

    @wrap_tool_call(name="InnerWrapper")
    def inner(
        request: ToolCallRequest, handler: Callable[[ToolCallRequest], ToolMessage | Command[Any]]
    ) -> ToolMessage | Command[Any]:
        call_log.append("inner_called")
        response = handler(request)
        call_log.append("inner_got_response")
        return response

    model = FakeToolCallingModel(
        tool_calls=[
            [ToolCall(name="search", args={"query": "test"}, id="1")],
            [],
        ]
    )

    agent = create_agent(
        model=model,
        tools=[search],
        middleware=[intercepting_outer, inner],
        checkpointer=InMemorySaver(),
    )

    result = agent.invoke(
        {"messages": [HumanMessage("Search")]},
        {"configurable": {"thread_id": "test"}},
    )

    # Both should be called, outer intercepts the response
    assert call_log == [
        "outer_before",
        "inner_called",
        "inner_got_response",
        "outer_after",
    ]

    tool_messages = [m for m in result["messages"] if isinstance(m, ToolMessage)]
    assert len(tool_messages) == 1
    assert "Outer intercepted" in tool_messages[0].content