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Pydantic Should we cap the required_python version in v1? (Fix)

Fixed
Spec
Package
Pydantic
Fixed In
1.10.17
Affected Versions
1.10.16–3.13
Python
3.13
Verdict
Status
Fixed
Safe for prod
No
Risk
Medium
Last verified
2026-02-09
Own content ratio
0.27
#9663 ai auth duplicates llm serialization Updated: 2026-02-13
Issue #9663

The Fix

pip install pydantic==1.10.17

Based on closed pydantic/pydantic issue #9663 · PR/commit linked

Production note: This usually shows up under retries/timeouts. Treat it as a side-effect risk until you can verify behavior with a canary + real traffic.

Jump to Verify Open PR/Commit
@@ -1,130 +0,0 @@ @@ -1,130 +0,0 @@ -# NOTE This file aliases the pydantic namespace as pydantic.v1 for smoother v1 -> v2 transition -# flake8: noqa -import importlib
repro.py
FAILED tests/test_validators.py::test_make_generic_validator[fields0-_v_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields1-_v_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields2-_v_,_field_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields3-_v_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields4-_v_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields5-_v_,_field_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields6-_v_,_field_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields7-_v_,_config_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields8-_v_,_field_,_values_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields9-_cls_,_v_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields10-_cls_,_v_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields11-_cls_,_v_,_field_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields12-_cls_,_v_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields13-_cls_,_v_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields14-_cls_,_v_,_field_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields15-_cls_,_v_,_field_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields16-_cls_,_v_,_config_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields17-_cls_,_v_,_field_,_values_,_config_] - KeyError: 'testing_function' tests/test_validators.py ⨯ 96% █████████▋ ――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――― test_make_generic_validator[fields17-_cls_,_v_,_field_,_values_,_config_] ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――― fields = ['cls', 'val', 'field', 'values', 'config'], result = '_cls_,_v_,_field_,_values_,_config_' @pytest.mark.parametrize( 'fields,result', [ (['val'], '_v_'), (['foobar'], '_v_'), (['val', 'field'], '_v_,_field_'), (['val', 'config'], '_v_,_config_'), (['val', 'values'], '_v_,_values_'), (['val', 'field', 'config'], '_v_,_field_,_config_'), (['val', 'field', 'values'], '_v_,_field_,_values_'), (['val', 'config', 'values'], '_v_,_config_,_values_'), (['val', 'field', 'values', 'config'], '_v_,_field_,_values_,_config_'), (['cls', 'val'], '_cls_,_v_'), (['cls', 'foobar'], '_cls_,_v_'), (['cls', 'val', 'field'], '_cls_,_v_,_field_'), (['cls', 'val', 'config'], '_cls_,_v_,_config_'), (['cls', 'val', 'values'], '_cls_,_v_,_value ... (truncated) ...
verify
Re-run the failing test: pytest tests/test_private_attributes.py::test_private_attribute_annotation
fix.md
Option A — Upgrade to fixed release\npip install pydantic==1.10.17\nWhen NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.\n\n

Why This Fix Works in Production

  • Trigger: FAILED tests/test_private_attributes.py::test_private_attribute_annotation - AssertionError: assert {'__firstline...attributes__'} == {'__foo__'}
  • Mechanism: Mirrors modules in the `v1` namespace to fix typing and object resolution issues in Python versions greater than 3.11.
  • Why the fix works: Mirrors modules in the `v1` namespace to fix typing and object resolution issues in Python versions greater than 3.11. (first fixed release: 1.10.17).
Production impact:
  • If left unfixed, the same config can fail only in production (env differences), causing startup failures or partial feature outages.

Why This Breaks in Prod

  • Triggered by an upgrade/regression window: 1.10.16–3.13 breaks; 1.10.17 is the first fixed release.
  • Shows up under Python 3.13 in real deployments (not just unit tests).
  • Surfaces as: FAILED tests/test_private_attributes.py::test_private_attribute_annotation - AssertionError: assert {'__firstline...attributes__'} == {'__foo__'}

Proof / Evidence

  • GitHub issue: #9663
  • Fix PR: https://github.com/pydantic/pydantic/pull/9660
  • First fixed release: 1.10.17
  • Affected versions: 1.10.16–3.13
  • Reproduced locally: No (not executed)
  • Last verified: 2026-02-09
  • Confidence: 0.85
  • Did this fix it?: Yes (upstream fix exists)
  • Own content ratio: 0.27

Discussion

High-signal excerpts from the issue thread (symptoms, repros, edge-cases).

Jump to Sources Open on GitHub
“Home Assistant is on v1 because only some integrations have been updated (see https://github.com/home-assistant/core/issues/99218)”
@bdraco · 2024-06-17 · confirmation · source
“@vfazio, Thanks for organizing discussion around this issue”
@sydney-runkle · 2024-06-17 · source
“A decision should probably be made prior to a new tag. https://github.com/pydantic/pydantic/pull/9660 may be important enough to drive that to allow v1 users to adopt…”
@vfazio · 2024-06-17 · source
“For the Cython error: https://github.com/cython/cython/pull/6084”
@vfazio · 2024-06-17 · source

Failure Signature (Search String)

  • FAILED tests/test_private_attributes.py::test_private_attribute_annotation - AssertionError: assert {'__firstline...attributes__'} == {'__foo__'}

Error Message

Stack trace
error.txt
Error Message ------------- FAILED tests/test_private_attributes.py::test_private_attribute_annotation - AssertionError: assert {'__firstline...attributes__'} == {'__foo__'} FAILED tests/test_private_attributes.py::test_underscore_attrs_are_private - AssertionError: assert {'__firstline...attributes__'} == {'__foo__'} def test_private_attribute_annotation(): class Model(BaseModel): """The best model""" __foo__: str class Config: underscore_attrs_are_private = True assert Model.__slots__ == {'__foo__'} E AssertionError: assert {'__firstline...attributes__'} == {'__foo__'} E Extra items in the left set: E '__static_attributes__' E '__firstlineno__' E Use -v to get more diff tests/test_private_attributes.py:66: AssertionError tests/test_private_attributes.py ⨯ 55% █████▌ ――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――― test_underscore_attrs_are_private ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――― def test_underscore_attrs_are_private(): cla ... (truncated) ...

Minimal Reproduction

repro.py
FAILED tests/test_validators.py::test_make_generic_validator[fields0-_v_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields1-_v_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields2-_v_,_field_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields3-_v_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields4-_v_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields5-_v_,_field_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields6-_v_,_field_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields7-_v_,_config_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields8-_v_,_field_,_values_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields9-_cls_,_v_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields10-_cls_,_v_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields11-_cls_,_v_,_field_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields12-_cls_,_v_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields13-_cls_,_v_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields14-_cls_,_v_,_field_,_config_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields15-_cls_,_v_,_field_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields16-_cls_,_v_,_config_,_values_] - KeyError: 'testing_function' FAILED tests/test_validators.py::test_make_generic_validator[fields17-_cls_,_v_,_field_,_values_,_config_] - KeyError: 'testing_function' tests/test_validators.py ⨯ 96% █████████▋ ――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――― test_make_generic_validator[fields17-_cls_,_v_,_field_,_values_,_config_] ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――― fields = ['cls', 'val', 'field', 'values', 'config'], result = '_cls_,_v_,_field_,_values_,_config_' @pytest.mark.parametrize( 'fields,result', [ (['val'], '_v_'), (['foobar'], '_v_'), (['val', 'field'], '_v_,_field_'), (['val', 'config'], '_v_,_config_'), (['val', 'values'], '_v_,_values_'), (['val', 'field', 'config'], '_v_,_field_,_config_'), (['val', 'field', 'values'], '_v_,_field_,_values_'), (['val', 'config', 'values'], '_v_,_config_,_values_'), (['val', 'field', 'values', 'config'], '_v_,_field_,_values_,_config_'), (['cls', 'val'], '_cls_,_v_'), (['cls', 'foobar'], '_cls_,_v_'), (['cls', 'val', 'field'], '_cls_,_v_,_field_'), (['cls', 'val', 'config'], '_cls_,_v_,_config_'), (['cls', 'val', 'values'], '_cls_,_v_,_value ... (truncated) ...

Environment

  • Python: 3.13
  • Pydantic: 1

Fix Options (Details)

Option A — Upgrade to fixed release Safe default (recommended)

pip install pydantic==1.10.17

When NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.

Use when you can deploy the upstream fix. It is usually lower-risk than long-lived workarounds.

Fix reference: https://github.com/pydantic/pydantic/pull/9660

First fixed release: 1.10.17

Last verified: 2026-02-09. Validate in your environment.

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When NOT to Use This Fix

  • Do not use if it changes public behavior or if the failure cannot be reproduced.

Verify Fix

verify
Re-run the failing test: pytest tests/test_private_attributes.py::test_private_attribute_annotation

Did This Fix Work in Your Case?

Quick signal helps us prioritize which fixes to verify and improve.

Prevention

  • Add a CI check that diffs key outputs after upgrades (OpenAPI schema snapshots, JSON payload shapes, CLI output).
  • Upgrade behind a canary and run integration tests against the canary before 100% rollout.

Version Compatibility Table

VersionStatus
1.10.16 Broken
3.13 Broken
1.10.17 Fixed

Related Issues

No related fixes found.

Cluster: pydantic:configuration-error Pydantic hub Pydantic best practices All hubs All clusters
Related clusters: Data consistency OpenAPI schema Serialization

Sources

We don’t republish the full GitHub discussion text. Use the links above for context.

Source & Disclaimer: Analysis derived from GitHub Issue #9663. Not affiliated with the library maintainers. Verify before production use.