test_custom_system_prompt_merges_correctly() — langchain Function Reference

Source Code

libs/partners/anthropic/tests/unit_tests/middleware/test_anthropic_tools.py lines 419–451

    def test_custom_system_prompt_merges_correctly(self) -> None:
        """Test custom system prompt merges with existing system message."""
        from langchain.agents.middleware.types import ModelRequest

        custom_prompt = "Custom instructions for memory tool."
        middleware = StateClaudeMemoryMiddleware(system_prompt=custom_prompt)

        existing_message = SystemMessage("Existing instructions.")
        request = ModelRequest(
            model=MagicMock(),
            messages=[],
            system_message=existing_message,
            tool_choice=None,
            tools=[],
            response_format=None,
            state={"messages": []},
            runtime=MagicMock(),
        )

        captured_request = None

        def handler(req: ModelRequest) -> MagicMock:
            nonlocal captured_request
            captured_request = req
            return MagicMock()

        middleware.wrap_model_call(request, handler)

        # Both prompts should be in the final message
        assert captured_request is not None
        assert captured_request.system_message is not None
        assert "Existing instructions." in captured_request.system_message.text
        assert custom_prompt in captured_request.system_message.text