Pydantic Python 3.14 does not support

The Fix

Updates the documentation for `use_attribute_docstrings` to clarify its limitations in the interactive interpreter.

Based on closed pydantic/pydantic issue #12651 · PR/commit linked

Production note: Most teams hit this during upgrades or environment changes. Roll out with a canary and smoke critical endpoints (health, OpenAPI/docs) before 100%.

Jump to Verify Open PR/Commit

@@ -1038,7 +1038,7 @@ class Model(BaseModel):
     # > Description in Field
     ```
-    This requires the source code of the class to be available at runtime.
+    This requires the source code of the class to be available at runtime (and so won't work in the interactive interpreter shell).

repro.py

from pydantic import BaseModel, ConfigDict, Field


class Model(BaseModel):
    model_config = ConfigDict(use_attribute_docstrings=True)

    x: str
    """
    Example of an attribute docstring
    """

    y: int = Field(description="Description in Field")
    """
    Description in Field overrides attribute docstring
    """


print(Model.model_fields["x"].description)
# > Example of an attribute docstring
print(Model.model_fields["y"].description)
# > Description in Field

verify

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

fix.md

Option A — Apply the official fix\nUpdates the documentation for `use_attribute_docstrings` to clarify its limitations in the interactive interpreter.\nWhen NOT to use: This fix is not applicable if the source code is not available at runtime.\n\n

Why This Fix Works in Production

Trigger: Running the example code from the [docs](https://docs.pydantic.dev/latest/api/config/#pydantic.config.ConfigDict.use_attribute_docstrings) on the interpreter…
Mechanism: The interactive interpreter does not retain the source code of the class at runtime

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

Shows up under Python 3.14 in real deployments (not just unit tests).
The interactive interpreter does not retain the source code of the class at runtime
Production symptom (often without a traceback): Python 3.14 does not support use_attribute_docstring

Proof / Evidence

GitHub issue: #12651
Fix PR: https://github.com/pydantic/pydantic/pull/12652
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.80
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.54

Discussion

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

Jump to Sources Open on GitHub

“This is expected: > This requires the source code of the class to be available at runtime.”

@Viicos · 2025-12-21 · source

Failure Signature (Search String)

Running the example code from the [docs](https://docs.pydantic.dev/latest/api/config/#pydantic.config.ConfigDict.use_attribute_docstrings) on the interpreter does not yield the

Copy-friendly signature

signature.txt

Failure Signature
-----------------
Python 3.14 does not support use_attribute_docstring
Running the example code from the [docs](https://docs.pydantic.dev/latest/api/config/#pydantic.config.ConfigDict.use_attribute_docstrings) on the interpreter does not yield the same result, shown below.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
Python 3.14 does not support use_attribute_docstring
Running the example code from the [docs](https://docs.pydantic.dev/latest/api/config/#pydantic.config.ConfigDict.use_attribute_docstrings) on the interpreter does not yield the same result, shown below.

Minimal Reproduction

repro.py

from pydantic import BaseModel, ConfigDict, Field


class Model(BaseModel):
    model_config = ConfigDict(use_attribute_docstrings=True)

    x: str
    """
    Example of an attribute docstring
    """

    y: int = Field(description="Description in Field")
    """
    Description in Field overrides attribute docstring
    """


print(Model.model_fields["x"].description)
# > Example of an attribute docstring
print(Model.model_fields["y"].description)
# > Description in Field

Environment

Python: 3.14
Pydantic: 2

What Broke

Users experience incorrect descriptions when using attribute docstrings in interactive sessions.

Why It Broke

The interactive interpreter does not retain the source code of the class at runtime

Fix Options (Details)

Option A — Apply the official fix

Updates the documentation for `use_attribute_docstrings` to clarify its limitations in the interactive interpreter.

When NOT to use: This fix is not applicable if the source code is not available at runtime.

Fix reference: https://github.com/pydantic/pydantic/pull/12652

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

When NOT to Use This Fix

This fix is not applicable if the source code is not available at runtime.

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?

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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
6.12.57	Broken

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.

Pydantic Python 3.14 does not support use_attribute_docstring (Fix)