# pydantic_core._pydantic_core.ValidationError: 1 validation error for Config
user_id
  Extra inputs are not permitted [type=extra_forbidden, input_value='abc123', input_type=str]

- **ID:** `python/pydantic-validation-error-extra-forbidden`
- **Domain:** python
- **Category:** data_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The model_config has extra='forbid' set, and the input data contains a field not declared in the model. Pydantic v2 defaults to 'ignore' but many projects set 'forbid' explicitly.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 2.x | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   from pydantic import BaseModel

class Config(BaseModel):
    user_id: str
    model_config = {'extra': 'forbid'}
   ```
2. **** (90% success)
   ```
   class Config(BaseModel):
    model_config = {'extra': 'ignore'}
   ```

## Dead Ends

- **** — Works for one schema but breaks when the same dict is validated against multiple models with different allowed fields. (50% fail)
- **** — Weakens validation across the entire app and may hide typos in field names. (65% fail)