# pydantic_core._pydantic_core.ValidationError: 1 validation error for RootModel[list[Item]]
  Input should be a valid list [type=list_type, input_value={'a': 1}, input_type=dict]

- **ID:** `python/pydantic-rootmodel-list`
- **Domain:** python
- **Category:** data_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

A RootModel[list[...]] received a dict. In v2, RootModel wraps the root value directly, so the input must be the list itself, not {'root': [...]}.

## Version Compatibility

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

## Workarounds

1. **** (95% success)
   ```
   from pydantic import RootModel
Items = RootModel[list[Item]]
Items.model_validate([{'a': 1}])
   ```
2. **** (90% success)
   ```
   from pydantic import TypeAdapter
ta = TypeAdapter(list[Item])
ta.validate_python([{'a': 1}])
   ```

## Dead Ends

- **** — v2 removed the implicit 'root' key; the model now expects the bare value. (70% fail)
- **** — __root__ is a v1 feature and raises PydanticUserError under v2. (75% fail)
- **** — Loses Pydantic validation and serialization hooks. (50% fail)