ai-agents-pydantic-compatibili-using-pydanticoutputparser-or-create-structured-ou-72d2af26

THEN To resolve, use pydantic v1 BaseModel (e.g., from pydantic.v1) for the output schema. Alternatively, downgrade LangChain to 0.1.5 or use a different output parsing method like the newer structured output methods that support pydantic v2.

# Fails with LangChain >=0.1.6 and pydantic v2:
from langchain.output_parsers import PydanticOutputParser
from pydantic import BaseModel
class TestModel(BaseModel):
    test_attribute: str
parser = PydanticOutputParser(pydantic_object=TestModel)  # ValidationError

# Fix: use pydantic v1 BaseModel:
from pydantic.v1 import BaseModel
class TestModelV1(BaseModel):
    test_attribute: str
parser = PydanticOutputParser(pydantic_object=TestModelV1)  # works