I'm also seeing this error:

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/langfuse/callback/langchain.py", line 627, in _parse_model_and_log_errors
    model_name = _extract_model_name(serialized, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/langfuse/extract_model.py", line 287, in _extract_model_name
    model = _extract_model_by_pattern("ChatAnthropic", serialized, "model")
  File "/usr/local/lib/python3.10/site-packages/langfuse/extract_model.py", line 342, in _extract_model_by_pattern
    extracted = _extract_model_with_regex(pattern, serialized["repr"])
KeyError: 'repr'

Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/langfuse/callback/langchain.py", line 627, in _parse_model_and_log_errors
    model_name = _extract_model_name(serialized, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/langfuse/extract_model.py", line 287, in _extract_model_name
    model = _extract_model_by_pattern("ChatAnthropic", serialized, "model")
  File "/usr/local/lib/python3.10/site-packages/langfuse/extract_model.py", line 342, in _extract_model_by_pattern
    extracted = _extract_model_with_regex(pattern, serialized["repr"])
KeyError: 'repr'