unicode_renderingTier 1 · 70% confidence

observability-unicode-rendering-after-upgrading-langfuse-to-a-version-including-pr-421a310b

agent: observability

When does this happen?

IF After upgrading Langfuse to a version including PR #8326 (circa Aug 5-6, 2025), the trace table summary view displays Unicode escape sequences (e.g., \u0421) instead of actual Cyrillic or other non-ASCII characters.

How others solved it

THEN In the backend Python code, change the `_serialize` function in `langfuse/_client/attributes.py` to call `json.dumps(obj, cls=EventSerializer, ensure_ascii=False)` instead of the default (which escapes non-ASCII). Ensure the frontend cell renderer does not double-escape the truncated JSON string. A temporary workaround is to monkey-patch that function in your deployment.

def _serialize(obj: Any) -> Optional[str]:
    return json.dumps(obj, cls=EventSerializer, ensure_ascii=False) if obj is not None else None

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