[viliamgonda]

What does this PR do?

Fixes langfuse/langfuse#19599

In LangchainCallbackHandler._get_error_level_and_status_message, ordinary exceptions only returned str(error) as the status message. For exceptions with an empty string representation (such as ValueError(), TimeoutError(), or custom exceptions without a message), the observation level was marked as "ERROR" but statusMessage remained empty (""), making the root exception type invisible in traces.

This change:

1. Updates _get_error_level_and_status_message to fall back to type(error).__name__ when str(error) is empty (str(error) or type(error).__name__), matching the existing fallback used for control flow exceptions.
2. Adds unit test test_error_without_message_uses_exception_type_as_status_message in tests/unit/test_langchain.py.

Type of change

• Bug fix
• New feature
• Breaking change
• Refactor
• Documentation update
• Tooling, CI, or repo maintenance

Verification

List the main commands you ran:

pytest tests/unit/test_langchain.py
ruff check langfuse/langchain/CallbackHandler.py tests/unit/test_langchain.py
ruff format --check langfuse/langchain/CallbackHandler.py tests/unit/test_langchain.py

Checklist

• I self-reviewed the diff using code_review.md.
• I added or updated tests for behavior changes.
• I updated docs, examples, or .env.template if needed.
• I did not hand-edit generated files; if generated files changed, I used the upstream regeneration path.
• I did not commit secrets or credentials.

Confidence Score: 5/5

This PR appears safe to merge.

Summary

Ordinary exceptions with empty messages now use their class name as the status message.

• LangChain traces name ordinary errors that have no message.

_{Reviews (1) · Last reviewed commit: "fix(langchain): fallback to exception cl..." · Reviewed by Greptile}

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