pydantic_version_mismatchTier 1 · 70% confidence
ai-agents-pydantic-version-mis-using-with-fallbacks-on-a-language-model-raises-va-26dc823d
agent: ai_agents
When does this happen?
IF Using with_fallbacks on a language model raises validation error: 'Can't instantiate abstract class BaseLanguageModel with abstract methods...'
How others solved it
THEN Ensure you are not mixing Pydantic v1 and v2 code. Pin to Pydantic v1 (e.g., pydantic~=1.10.12) until LangChain completes its migration, or fully upgrade to Pydantic v2 after August 25, 2023, and ensure all dependencies are compatible. Check that any custom classes extending LangChain use the correct Pydantic namespace as per the migration guide.
# Pin Pydantic v1 in requirements.txt pydantic~=1.10.12 # Or after full migration to v2: # pydantic>=2.0.0
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