# pydantic.errors.ConfigError: default_factory must be a callable

- **ID:** `python/pydantic-field-default-factory-error`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The default_factory argument in Field is not a callable (e.g., a list or int), causing ConfigError.

## Version Compatibility

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

## Workarounds

1. **** (95% success)
   ```
   Use default_factory=list or lambda: []
   ```
2. **** (85% success)
   ```
   Use default=[] instead of default_factory
   ```

## Dead Ends

- **** — List is not callable, must be a function like list. (90% fail)
- **** — Lambda must be callable, but syntax errors possible. (60% fail)