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Fix Pydantic v2 ORM Mode model_config Override Error

· 2 min read

TL;DR​

Pydantic v2 no longer supports class Config. Use model_config = ConfigDict(from_attributes=True) instead. If your model has a field named model_config, you must rename it to avoid conflict with the reserved attribute.

Problem Symptoms​

Error 1: class Config Not Working​

from pydantic import BaseModel

class AgentResponse(BaseModel):
    id: str
    name: str

    class Config:
        orm_mode = True  # v1 style
PydanticUserError: `orm_mode` is not a valid config option. Did you mean `from_attributes`?

Error 2: model_config Field Conflict​

class Agent(BaseModel):
    id: str
    model_config: dict  # Business field storing LLM config

    model_config = ConfigDict(from_attributes=True)
# TypeError: 'dict' object is not callable

Your model has a business field called model_config (storing LLM configuration), which conflicts with Pydantic v2's reserved name.

Root Cause​

1. Pydantic v2 Configuration Syntax Change​

Pydantic v2 uses model_config as the configuration attribute name, no longer supporting nested class Config:

Pydantic v1Pydantic v2
class Config: orm_mode = Truemodel_config = ConfigDict(from_attributes=True)
class Config: schema_extra = {...}model_config = ConfigDict(json_schema_extra={...})

2. model_config is a Reserved Name​

model_config is a special attribute in Pydantic v2 and cannot be used as a business field name simultaneously.

Solution​

1. Update ORM Mode Configuration​

from pydantic import BaseModel, ConfigDict

class AgentResponse(BaseModel):
    model_config = ConfigDict(from_attributes=True)  # New syntax

    id: str
    name: str

2. Rename Conflicting Field​

Rename the business field model_config to llm_config (or any non-reserved name):

# models/agent.py
class Agent(BaseModel):
    __tablename__ = "agent_agents"

    id: str
    llm_config: dict  # Renamed to avoid conflict

# schemas/agent.py
class AgentResponse(BaseModel):
    model_config = ConfigDict(from_attributes=True)

    agent_id: str
    llm_config: LlmConfig  # Keep consistent with model

3. Database Migration (If Needed)​

If the database column also needs renaming:

# alembic/versions/xxx_rename_model_config.py
def upgrade():
    op.alter_column('agent_agents', 'model_config', new_column_name='llm_config')

def downgrade():
    op.alter_column('agent_agents', 'llm_config', new_column_name='model_config')

FAQ​

Q: What did Pydantic v2 replace orm_mode with?​

A: It's now from_attributes=True, and the configuration syntax changed from class Config to model_config = ConfigDict(...).

Q: Why is my model_config field causing errors?​

A: model_config is a reserved attribute name in Pydantic v2 for configuring model behavior. If your business code has a field with the same name, you need to rename it.

Q: What other common ConfigDict options exist?​

A: from_attributes (ORM mode), json_schema_extra (schema extension), str_strip_whitespace (auto strip whitespace), validate_assignment (validate on assignment).