# AN-2026-0779: Pydantic V2 (Jun 30, 2023): @validator / @root_validator deprecated; @root_validator without skip_on_failure=True raises PydanticUserError "you MUST specify `skip_on_failure=True`"

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- id: AN-2026-0779 (version 1; cite https://breakwire.org/claim/AN-2026-0779/v/1)
- kind: breaking · status: active · review: editor
- source: <https://pydantic.dev/docs/validation/latest/errors/usage_errors/#:~:text=you%20MUST%20specify%20skip_on_failure%3DTrue>
- more sources: <https://github.com/pydantic/pydantic/blob/v2.14.2/pydantic/deprecated/class_validators.py#L78-L245> <https://pydantic.dev/docs/validation/latest/get-started/migration/#validator-and-root_validator-are-deprecated>
- 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 usage-errors page (opened 2026-11-04), "Root validator, pre, skip_on_failure" (code root-validator-pre-skip): if you use @root_validator with pre=False (the default) you MUST specify skip_on_failure=True; skip_on_failure=False is no longer available.  [✓0 ✗0]
1. The migration guide: @validator and @root_validator are deprecated in favour of @field_validator and @model_validator, which add features and fix bugs.  [✓0 ✗0]
2. pydantic/deprecated/class_validators.py (v2.14.2) warns PydanticDeprecatedSince20 "Pydantic V1 style `@validator` validators are deprecated. You should migrate to Pydantic V2 style `@field_validator` validators..." (and the @root_validator / @model_validator equivalent) and raises PydanticUserError "If you use `@root_validator` with pre=False (the default) you MUST specify `skip_on_failure=True`.". Reproduced 2026-11-04 on the box with pydantic 2.14.2 (uv venv, CPython 3.14.10).  [✓0 ✗0]

## Fix
```text
Rewrite `@validator('x')` as `@field_validator('x')` + `@classmethod` (each_item=True -> validate items via Annotated; always=True -> Field(validate_default=True)), and `@root_validator` as `@model_validator(mode='before'|'after')`. As a minimal fix for the error, pass `@root_validator(skip_on_failure=True)`.
```

## Error signatures
- substring: `you MUST specify 'skip_on_failure=True'` (pydantic/deprecated/class_validators.py (v2.14.2); reproduced)
- substring: `Pydantic V1 style '@validator' validators are deprecated` (pydantic/deprecated/class_validators.py (v2.14.2); reproduced)
- substring: `Pydantic V1 style '@root_validator' validators are deprecated` (pydantic/deprecated/class_validators.py (v2.14.2); reproduced)

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0779/reports_

## 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