Pydantic Pyrefly integration? (Fix)

The Fix

pip install pydantic==2.11.8

Based on closed pydantic/pydantic issue #12125 · PR/commit linked

Open PR/Commit

@@ -231,6 +231,9 @@ jobs:
       run: make test-typechecking-mypy
 
+    - name: Run typechecking integration tests (Pyrefly)
+      run: make test-typechecking-pyrefly
+

fix.md

Option A — Upgrade to fixed release\npip install pydantic==2.11.8\nWhen NOT to use: This fix should not be used if Pyrefly is not required for type checking.\n\n

Why This Fix Works in Production

Trigger: No production failures reported; this is an enhancement.
Mechanism: Integration of Pyrefly into Pydantic's type checking test suite was necessary for compatibility
Why the fix works: Integrates Pyrefly into Pydantic's type checking test suite, ensuring compatibility with multiple type checkers. (first fixed release: 2.11.8).

Why This Breaks in Prod

Integration of Pyrefly into Pydantic's type checking test suite was necessary for compatibility
Production symptom (often without a traceback): No production failures reported; this is an enhancement.

Proof / Evidence

GitHub issue: #12125
Fix PR: https://github.com/pydantic/pydantic/pull/12127
First fixed release: 2.11.8
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.81

Discussion

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

Jump to Sources Open on GitHub

“Hello @rchen152, that would be great. PR welcomed!”

@Viicos · 2025-08-05 · source

“Awesome! I opened https://github.com/pydantic/pydantic/pull/12127.”

@rchen152 · 2025-08-05 · source

Failure Signature (Search String)

No production failures reported; this is an enhancement.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
No production failures reported; this is an enhancement.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
No production failures reported; this is an enhancement.

What Broke

No production failures reported; this is an enhancement.

Why It Broke

Integration of Pyrefly into Pydantic's type checking test suite was necessary for compatibility

Fix Options (Details)

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

pip install pydantic==2.11.8

When NOT to use: This fix should not be used if Pyrefly is not required for type checking.

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/12127

First fixed release: 2.11.8

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

When NOT to Use This Fix

This fix should not be used if Pyrefly is not required for type checking.

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
2.11.8	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:other 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.