# pydantic.errors.ConfigError: model is immutable

- **ID:** `python/pydantic-model-config-immutable`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Attempting to modify a field of a model that has frozen=True in config, raising ConfigError.

## Version Compatibility

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

## Workarounds

1. **** (95% success)
   ```
   Remove frozen=True from model config
   ```
2. **** (90% success)
   ```
   Use model_copy(update={'field': new_value}) to create a new instance
   ```

## Dead Ends

- **** — Frozen models disallow attribute setting. (90% fail)
- **** — This works but doesn't modify original; may be acceptable. (40% fail)