[devin-ai-integration]

Summary

messages_to_dict (the dict/str/LangChain -> Discussion boundary used by reproducibility_agent replay) had no test, including the recently patched LangChain role_map fallback. Adds unit tests in tests/llm/test_llm_utils.py covering every branch:

• dict passthrough and bare-string -> {"role": "<unknown role>"}
• LangChain message with convert_message_to_dict available (monkeypatched)
• LangChain fallback with convert_message_to_dict set to None, parametrized over human -> user, ai -> assistant, system -> system, and an unmapped tool -> tool (guards against the old hardcoded 'user')
• ValueError on an unsupported object

LangChain is not installed in this env, so the tests monkeypatch llm_utils.LangchainBaseMessage to a local FakeLangchainMessage (.type / .content) to exercise the branch deterministically.

Devin-Org: engineering

Link to Devin session: https://app.devin.ai/sessions/6d82f0caa4c445eca0a304dedd7d6168
Open in Devin Desktop: https://app.devin.ai/desktop/session/6d82f0caa4c445eca0a304dedd7d6168?variant=devin

[devin-ai-integration]

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