Pydantic Only support one config specification location in

The Fix

pip install pydantic==1.10.19

Based on closed pydantic/pydantic issue #10371 · PR/commit linked

Open PR/Commit

@@ -90,6 +90,7 @@ def complete_dataclass(
     raise_errors: bool = True,
     types_namespace: dict[str, Any] | None,
+    _force_build: bool = False,
 ) -> bool:
     """Finish building a pydantic dataclass.

fix.md

Option A — Upgrade to fixed release\npip install pydantic==1.10.19\nWhen NOT to use: This fix should not be used if multiple configuration sources are intended.\n\n

Why This Fix Works in Production

Trigger: Users experienced unexpected behavior due to conflicting configuration specifications.
Mechanism: The configuration was specified in both the `@dataclass` decorator and the `__pydantic_config__` attribute
Why the fix works: Warns if configuration is specified on both the `@dataclass` decorator and the `__pydantic_config__` attribute, addressing issue #10371. (first fixed release: 1.10.19).

Why This Breaks in Prod

The configuration was specified in both the `@dataclass` decorator and the `__pydantic_config__` attribute
Production symptom (often without a traceback): Users experienced unexpected behavior due to conflicting configuration specifications.

Proof / Evidence

GitHub issue: #10371
Fix PR: https://github.com/pydantic/pydantic/pull/10313
First fixed release: 1.10.19
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.79

Discussion

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

Jump to Sources Open on GitHub

“Unblocks https://github.com/pydantic/pydantic/pull/10313”

Issue thread · issue description · source

Failure Signature (Search String)

Users experienced unexpected behavior due to conflicting configuration specifications.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Users experienced unexpected behavior due to conflicting configuration specifications.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Users experienced unexpected behavior due to conflicting configuration specifications.

What Broke

Users experienced unexpected behavior due to conflicting configuration specifications.

Why It Broke

The configuration was specified in both the `@dataclass` decorator and the `__pydantic_config__` attribute

Fix Options (Details)

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

pip install pydantic==1.10.19

When NOT to use: This fix should not be used if multiple configuration sources are intended.

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/10313

First fixed release: 1.10.19

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

When NOT to Use This Fix

This fix should not be used if multiple configuration sources are intended.

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
1.10.19	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.

Pydantic Only support one config specification location in pydantic `dataclasses` (Fix)