Pydantic model_json_schema export with Annotated types

The Fix

pip install pydantic==2.6.2

Based on closed pydantic/pydantic issue #8780 · 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

@@ -402,6 +402,13 @@ def merge_field_infos(*field_infos: FieldInfo, **overrides: Any) -> FieldInfo:
             field_info = copy(field_infos[0])
             field_info._attributes_set.update(overrides)
+
+            default_override = overrides.pop('default', PydanticUndefined)
+            if default_override is Ellipsis:

repro.py

from typing import Annotated
from pydantic import Field, create_model


Model = create_model(
    'test_model',
    foo=(int, ...),
    bar=(Annotated[int, Field(description="Bar description")], ...),
    baz=(Annotated[int, Field(..., description="Baz description")], ...),
)


Model.model_json_schema()

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==2.6.2\nWhen NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.\n\n

Why This Fix Works in Production

Trigger: model_json_schema export with Annotated types misses 'required' parameters
Mechanism: The model_json_schema did not recognize fields annotated with FieldInfo and Ellipsis as required
Why the fix works: Fixes the issue where using model_json_schema with Annotated types did not mark them as required. (first fixed release: 2.6.2).

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 3.11 in real deployments (not just unit tests).
The model_json_schema did not recognize fields annotated with FieldInfo and Ellipsis as required
Production symptom (often without a traceback): model_json_schema export with Annotated types misses 'required' parameters

Proof / Evidence

GitHub issue: #8780
Fix PR: https://github.com/pydantic/pydantic/pull/8793
First fixed release: 2.6.2
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.61

Discussion

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

Jump to Sources Open on GitHub

“Indeed, a related issue is here: https://github.com/pydantic/pydantic/issues/8534”

@sydney-runkle · 2024-02-12 · source

Failure Signature (Search String)

model_json_schema export with Annotated types misses 'required' parameters
It seems that using `model_json_schema` on type annotations combining `typing.Annotated` and `pydantic.Field` result in the `Annotated` not being marked as `required`.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
model_json_schema export with Annotated types misses 'required' parameters
It seems that using `model_json_schema` on type annotations combining `typing.Annotated` and `pydantic.Field` result in the `Annotated` not being marked as `required`.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
model_json_schema export with Annotated types misses 'required' parameters
It seems that using `model_json_schema` on type annotations combining `typing.Annotated` and `pydantic.Field` result in the `Annotated` not being marked as `required`.

Minimal Reproduction

repro.py

from typing import Annotated
from pydantic import Field, create_model


Model = create_model(
    'test_model',
    foo=(int, ...),
    bar=(Annotated[int, Field(description="Bar description")], ...),
    baz=(Annotated[int, Field(..., description="Baz description")], ...),
)


Model.model_json_schema()

Environment

Python: 3.11
Pydantic: 2

What Broke

JSON schema output incorrectly marked required fields, leading to potential validation issues.

Why It Broke

The model_json_schema did not recognize fields annotated with FieldInfo and Ellipsis as required

Fix Options (Details)

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

pip install pydantic==2.6.2

When NOT to use: Do not use if it changes public behavior or if the failure cannot be reproduced.

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/8793

First fixed release: 2.6.2

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

When NOT to Use This Fix

Do not use if it changes public behavior or if the failure cannot be reproduced.

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
2.6.2	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_json_schema export with Annotated types misses 'required' parameters (Fix)