Pydantic `pydantic` work plan for Sydney Runkle: October

The Fix

pip install pydantic==2.10.0

Based on closed pydantic/pydantic issue #10561 · PR/commit linked

Production note: Watch p95/p99 latency and retry volume; timeouts can turn into retry storms and duplicate side-effects.

Open PR/Commit

@@ -11,6 +11,7 @@
     from ..dataclasses import PydanticDataclass
     from ..main import BaseModel
+    from ..type_adapter import TypeAdapter

fix.md

Option A — Upgrade to fixed release\npip install pydantic==2.10.0\nWhen NOT to use: Do not use this fix if backward compatibility with older versions is required.\n\n

Why This Fix Works in Production

Trigger: Performance issues leading to slow response times in applications using pydantic.
Mechanism: Refactor namespace logic for annotations evaluation to improve performance and support edge cases
Why the fix works: Refactor namespace logic for annotations evaluation to improve performance and support edge cases. (first fixed release: 2.10.0).

Production impact:

If left unfixed, tail latency can spike under load and surface as timeouts/retries (amplifying incident impact).

Why This Breaks in Prod

Refactor namespace logic for annotations evaluation to improve performance and support edge cases
Production symptom (often without a traceback): Performance issues leading to slow response times in applications using pydantic.

Proof / Evidence

GitHub issue: #10561
Fix PR: https://github.com/pydantic/pydantic/pull/10537
First fixed release: 2.10.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.75
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.82

Discussion

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

Jump to Sources Open on GitHub

“Much of this will roll over to next week - ended up doing more logfire work than expected + minor bug fixes here on pydantic.…”

@sydney-runkle · 2024-10-11 · source

Failure Signature (Search String)

Performance issues leading to slow response times in applications using pydantic.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Performance issues leading to slow response times in applications using pydantic.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Performance issues leading to slow response times in applications using pydantic.

What Broke

Performance issues leading to slow response times in applications using pydantic.

Why It Broke

Refactor namespace logic for annotations evaluation to improve performance and support edge cases

Fix Options (Details)

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

pip install pydantic==2.10.0

When NOT to use: Do not use this fix if backward compatibility with older versions is required.

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/10537

First fixed release: 2.10.0

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

When NOT to Use This Fix

Do not use this fix if backward compatibility with older versions is required.

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
2.10.0	Fixed

Related Issues

No related fixes found.

Cluster: pydantic:latency 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.

Pydantic `pydantic` work plan for Sydney Runkle: October 7th - October 11th, 2024 (Fix)