ai-agents-pydantic-compatibili-using-pydanticoutputparser-or-create-structured-ou-9aa5f6f6

THEN Downgrade langchain to 0.1.5, or ensure your output model inherits from pydantic.v1.BaseModel (via langchain's pydantic v1 compatibility layer) instead of pydantic v2 BaseModel.

from langchain.output_parsers import PydanticOutputParser
from pydantic import BaseModel

class TestModel(BaseModel):
    test_attribute: str

# This fails in langchain >=0.1.6
parser = PydanticOutputParser(pydantic_object=TestModel)

# Workaround: use pydantic v1 BaseModel
# from pydantic.v1 import BaseModel as BaseModelV1
# class TestModel(BaseModelV1):
#     test_attribute: str