Pydantic Model is not fully defined together with from

The Fix

pip install pydantic==2.10.3

Based on closed pydantic/pydantic issue #11004 · 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

@@ -63,13 +63,14 @@ def __get_pydantic_core_schema__(self, source_type: Any, handler: GetCoreSchemaH
         """
         schema = handler(source_type)
-        globalns, localns = handler._get_types_namespace()
         try:
+            # Do not pass in globals as the function could be defined in a different module.

repro.py

# File b
from __future__ import annotations  # Deleting this will fix the issue. It was OK to use it before Pydantic 2.10.0

from typing import Annotated, Any
from pydantic import PlainSerializer


def serializer(value:Any) -> Any:
    return value

Something = Annotated[Any, PlainSerializer(serializer)]

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==2.10.3\nWhen NOT to use: This fix should not be used if the code relies on future annotations for other functionalities.\n\n

Why This Fix Works in Production

Trigger: Model(something=1)
Mechanism: Fixes the issue where the Model is not fully defined when using from __future__ import annotations in Pydantic 2.10.x.
Why the fix works: Fixes the issue where the Model is not fully defined when using from __future__ import annotations in Pydantic 2.10.x. (first fixed release: 2.10.3).

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 3.12 in real deployments (not just unit tests).
Surfaces as: Traceback (most recent call last):

Proof / Evidence

GitHub issue: #11004
Fix PR: https://github.com/pydantic/pydantic/pull/11008
First fixed release: 2.10.3
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.42

Discussion

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

Jump to Sources Open on GitHub

“Thanks for the bug report, this was an oversight in https://github.com/pydantic/pydantic/pull/10929. I will provide a fix for the next patch release.”

@Viicos · 2024-11-29 · source

“I tried the new Pydantic release that includes fix for this issue and I can confirm it solves the issue. Thank you very much for…”

@Pijukatel · 2024-12-05 · source

Failure Signature (Search String)

Model(something=1)

Error Message

Stack trace

error.txt

Error Message
-------------
Traceback (most recent call last):
  File "...b.py", line 9, in <module>
    Model(something=1)
  File ".../lib/python3.12/site-packages/pydantic/main.py", line 214, in __init__
    validated_self = self.__pydantic_validator__.validate_python(data, self_instance=self)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../lib/python3.12/site-packages/pydantic/_internal/_mock_val_ser.py", line 100, in __getattr__
    raise PydanticUserError(self._error_message, code=self._code)
pydantic.errors.PydanticUserError: `Model` is not fully defined; you should define `Any`, then call `Model.model_rebuild()`.


For further information visit https://errors.pydantic.dev/2.10/u/class-not-fully-defined

Minimal Reproduction

repro.py

# File b
from __future__ import annotations  # Deleting this will fix the issue. It was OK to use it before Pydantic 2.10.0

from typing import Annotated, Any
from pydantic import PlainSerializer


def serializer(value:Any) -> Any:
    return value

Something = Annotated[Any, PlainSerializer(serializer)]

Environment

Python: 3.12
Pydantic: 2

What Broke

Users encounter PydanticUserError indicating the Model is not fully defined.

Fix Options (Details)

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

pip install pydantic==2.10.3

When NOT to use: This fix should not be used if the code relies on future annotations for other functionalities.

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/11008

First fixed release: 2.10.3

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

When NOT to Use This Fix

This fix should not be used if the code relies on future annotations for other functionalities.

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
2.10.3	Fixed

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 Model is not fully defined together with from __future__ import annotations (Started in (Fix)