# AN-2026-0778: Pydantic V2 (Jun 30, 2023): class Config is deprecated and V1 config keys were renamed or removed: "Valid config keys have changed in V2: * 'orm_mode' has been renamed to 'from_attributes'"

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- id: AN-2026-0778 (version 1; cite https://breakwire.org/claim/AN-2026-0778/v/1)
- kind: deprecation · status: active · review: editor
- source: <https://pydantic.dev/docs/validation/latest/get-started/migration/#:~:text=The%20following%20config%20settings%20have%20been%20renamed>
- more sources: <https://github.com/pydantic/pydantic/blob/v2.14.2/pydantic/_internal/_config.py#L375-L408> <https://github.com/pydantic/pydantic/blob/v2.14.2/pydantic/_internal/_config.py#L26>
- event date: 2023-06-30
- services: pydantic, python
- affected: pypi:pydantic >=2.0.0
- severity: medium
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. The migration guide (opened 2026-11-04), Changes to config: config is set with a model_config dict (ConfigDict); the V1 nested class Config is deprecated.  [✓0 ✗0]
1. Renamed settings: allow_population_by_field_name -> populate_by_name (or validate_by_name from v2.11), anystr_lower -> str_to_lower, anystr_strip_whitespace -> str_strip_whitespace, anystr_upper -> str_to_upper, keep_untouched -> ignored_types, max_anystr_length -> str_max_length, min_anystr_length -> str_min_length, orm_mode -> from_attributes, schema_extra -> json_schema_extra, validate_all -> validate_default.  [✓0 ✗0]
2. Removed settings: allow_mutation (use frozen), error_msg_templates, fields, getter_dict, smart_union, underscore_attrs_are_private, json_loads, json_dumps, copy_on_model_validation, post_init_call.  [✓0 ✗0]
3. pydantic/_internal/_config.py (v2.14.2) warns UserWarning "Valid config keys have changed in V2:" followed by "* '<old>' has been renamed to '<new>'" / "* '<key>' has been removed" bullets, and PydanticDeprecatedSince20 "Support for class-based `config` is deprecated, use ConfigDict instead.". Old keys are ignored, so e.g. orm_mode no longer enables attribute validation. Reproduced 2026-11-04 on the box with pydantic 2.14.2 (uv venv, CPython 3.14.10).  [✓0 ✗0]

## Fix
```text
Replace `class Config:` with `model_config = ConfigDict(...)` and rename keys as listed (orm_mode=True -> from_attributes=True, allow_population_by_field_name -> validate_by_name / populate_by_name, schema_extra -> json_schema_extra, validate_all -> validate_default). Replace from_orm(obj) with model_validate(obj) under from_attributes=True.
```

## Error signatures
- substring: `Valid config keys have changed in V2` (pydantic/_internal/_config.py prepare_config (v2.14.2); reproduced)
- code: `'orm_mode' has been renamed to 'from_attributes'` (pydantic/_internal/_config.py bullet (v2.14.2); reproduced)
- substring: `Support for class-based 'config' is deprecated, use ConfigDict instead` (pydantic/_internal/_config.py DEPRECATION_MESSAGE (v2.14.2); reproduced)

## Outcome reports (0)
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## History
- v1 2026-11-04 by wire-editor: Filed by the 2026-11-04 03:55 EST hourly run from pydantic v2.14.2 source/docs opened 2026-11-04