Pydantic Support Python 3.13 (Fix)

The Fix

pip install pydantic==2.8.0

Based on closed pydantic/pydantic issue #9668 · PR/commit linked

Jump to Verify Open PR/Commit

@@ -20,7 +20,7 @@ jobs:
       fail-fast: false
       matrix:
-        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
     steps:

repro.py

$ gh repo clone pydantic/pydantic
$ cd pydantic
$ python3.13 -m venv _e
$ . _e/bin/activate
(_e) $ UNSAFE_PYO3_SKIP_VERSION_CHECK=1 pip install -e .
(_e) $ pip install cloudpickle coverage[toml] dirty-equals eval-type-backport pytest pytest-mock pytest-pretty pytest-examples faker pytest-benchmark pytest-codspeed packaging
(_e) $ python -m pytest

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

fix.md

Option A — Upgrade to fixed release\npip install pydantic==2.8.0\nWhen NOT to use: This fix should not be used if the application requires compatibility with earlier Python versions without testing.\n\n

Why This Fix Works in Production

Trigger: - Fedora now has [Python 3.13 as the system Python](https://fedoraproject.org/wiki/Changes/Python3.13) in Rawhide, and [Fedora 41 will release with Python 3.13…
Mechanism: Adds support for Python 3.13, addressing compatibility issues and updating CI configurations.
Why the fix works: Adds support for Python 3.13, addressing compatibility issues and updating CI configurations. (first fixed release: 2.8.0).

Why This Breaks in Prod

Shows up under Python 3.13 in real deployments (not just unit tests).
Production symptom (often without a traceback): - Fedora now has [Python 3.13 as the system Python](https://fedoraproject.org/wiki/Changes/Python3.13) in Rawhide, and [Fedora 41 will release with Python 3.13 in October](https://fedorapeople.org/groups/schedule/f-41/f-41-all-tasks.html).

Proof / Evidence

GitHub issue: #9668
Fix PR: https://github.com/pydantic/pydantic/pull/9743
First fixed release: 2.8.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.58

Discussion

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

Jump to Sources Open on GitHub

“Definitely something we're prioritizing. I'll pull this in once we get the new version of pyo3 into pydantic-core with 3.13 support. Hoping to have this…”

@sydney-runkle · 2024-06-18 · source

“@musicinmybrain, Thanks for opening this feature request. Support for 3.13 is definitely something we want to do explicitly soon. I'll chat with the team re…”

@sydney-runkle · 2024-06-17 · source

Failure Signature (Search String)

- Fedora now has [Python 3.13 as the system Python](https://fedoraproject.org/wiki/Changes/Python3.13) in Rawhide, and [Fedora 41 will release with Python 3.13 in
- Test collection errors due to the `DeprecationWarning` from https://github.com/pydantic/pydantic/issues/9613.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
- Fedora now has [Python 3.13 as the system Python](https://fedoraproject.org/wiki/Changes/Python3.13) in Rawhide, and [Fedora 41 will release with Python 3.13 in October](https://fedorapeople.org/groups/schedule/f-41/f-41-all-tasks.html).
- Test collection errors due to the `DeprecationWarning` from https://github.com/pydantic/pydantic/issues/9613.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
- Fedora now has [Python 3.13 as the system Python](https://fedoraproject.org/wiki/Changes/Python3.13) in Rawhide, and [Fedora 41 will release with Python 3.13 in October](https://fedorapeople.org/groups/schedule/f-41/f-41-all-tasks.html).
- Test collection errors due to the `DeprecationWarning` from https://github.com/pydantic/pydantic/issues/9613.

Minimal Reproduction

repro.py

$ gh repo clone pydantic/pydantic
$ cd pydantic
$ python3.13 -m venv _e
$ . _e/bin/activate
(_e) $ UNSAFE_PYO3_SKIP_VERSION_CHECK=1 pip install -e .
(_e) $ pip install cloudpickle coverage[toml] dirty-equals eval-type-backport pytest pytest-mock pytest-pretty pytest-examples faker pytest-benchmark pytest-codspeed packaging
(_e) $ python -m pytest

Environment

Python: 3.13

Fix Options (Details)

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

pip install pydantic==2.8.0

When NOT to use: This fix should not be used if the application requires compatibility with earlier Python versions without testing.

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

Option D — Guard side-effects with OnceOnly Guardrail for side-effects

Mitigate duplicate external side-effects under retries/timeouts/agent loops by gating the operation before calling external systems.

Place OnceOnly between your code/agent and real side-effects (Stripe, emails, CRM, APIs).
Use a stable key per side-effect (e.g., customer_id + action + idempotency_key).
Fail-safe: configure fail-open vs fail-closed based on blast radius and spend risk.

Show example snippet (optional)

onceonly.py

from onceonly import OnceOnly
import os

once = OnceOnly(api_key=os.environ["ONCEONLY_API_KEY"], fail_open=True)

# Stable idempotency key per real side-effect.
# Use a request id / job id / webhook delivery id / Stripe event id, etc.
event_id = "evt_..."  # replace
key = f"stripe:webhook:{event_id}"

res = once.check_lock(key=key, ttl=3600)
if res.duplicate:
    return {"status": "already_processed"}

# Safe to execute the side-effect exactly once.
handle_event(event_id)

See OnceOnly SDK

When NOT to use: Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.

Fix reference: https://github.com/pydantic/pydantic/pull/9743

First fixed release: 2.8.0

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

When NOT to Use This Fix

This fix should not be used if the application requires compatibility with earlier Python versions without testing.
Do not use this to hide logic bugs or data corruption. Use it to block duplicate external side-effects and enforce tool permissions/spend caps.

Verify Fix

verify

Re-run the minimal reproduction on your broken version, then apply the fix and re-run.

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

Version	Status
2.8.0	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:serialization Pydantic hub Pydantic best practices All hubs All clusters

Related clusters: Configuration error Data consistency OpenAPI schema

Sources

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