test_summarization_middleware_find_safe_cutoff_preserves_ai_tool_pair() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/implementations/test_summarization.py lines 1057–1089

def test_summarization_middleware_find_safe_cutoff_preserves_ai_tool_pair() -> None:
    """Test `_find_safe_cutoff` preserves AI/Tool message pairs together."""
    middleware = SummarizationMiddleware(
        model=MockChatModel(), trigger=("messages", 10), keep=("messages", 3)
    )

    # Messages list: [Human, AI, Tool, Tool, Tool, Human]
    messages: list[AnyMessage] = [
        HumanMessage(content="msg1"),
        AIMessage(
            content="ai",
            tool_calls=[
                {"name": "tool1", "args": {}, "id": "call1"},
                {"name": "tool2", "args": {}, "id": "call2"},
                {"name": "tool3", "args": {}, "id": "call3"},
            ],
        ),
        ToolMessage(content="result1", tool_call_id="call1"),
        ToolMessage(content="result2", tool_call_id="call2"),
        ToolMessage(content="result3", tool_call_id="call3"),
        HumanMessage(content="msg2"),
    ]

    # Target cutoff index is len(messages) - messages_to_keep = 6 - 3 = 3
    # Index 3 is a ToolMessage, we move back to index 1 to include AIMessage
    cutoff = middleware._find_safe_cutoff(messages, messages_to_keep=3)
    assert cutoff == 1

    # With messages_to_keep=2, target cutoff index is 6 - 2 = 4
    # Index 4 is a ToolMessage, we move back to index 1 to include AIMessage
    # This preserves the AI + Tools + Human, more than requested but valid
    cutoff = middleware._find_safe_cutoff(messages, messages_to_keep=2)
    assert cutoff == 1