Pydantic 2.10: `validated_data` must be provided if

The Fix

Relaxed the check for validated data in default factory utilities to prevent breaking changes in Pydantic 2.10.

Based on closed pydantic/pydantic issue #10912 · 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

@@ -572,7 +572,9 @@ def deprecation_message(self) -> str | None:
 
     @overload
-    def get_default(self, *, call_default_factory: Literal[True], validated_data: dict[str, Any]) -> Any: ...
+    def get_default(
+        self, *, call_default_factory: Literal[True], validated_data: dict[str, Any] | None = None

repro.py

from typing import ClassVar, List, Set

from pydantic import BaseModel, Field


class PrefectBaseModel(BaseModel):
    _reset_fields: ClassVar[Set[str]] = set()

    def reset_fields(self):
        return self.model_copy(
            update={
                field: self.model_fields[field].get_default(call_default_factory=True)
                for field in self._reset_fields
            }
        )


class TaskRun(PrefectBaseModel):
    _reset_fields: ClassVar[Set[str]] = {"tags"}

    name: str
    tags: List[str] = Field(default_factory=list)


def main():
    task = TaskRun(name="test-task")
    task.tags.append("new-tag")
    task.reset_fields()


if __name__ == "__main__":
    main()

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\nRelaxed the check for validated data in default factory utilities to prevent breaking changes in Pydantic 2.10.\nWhen NOT to use: This fix should not be used if the application relies on the previous behavior of default factories.\n\nOption C — Workaround\nversion above\nWhen NOT to use: This fix should not be used if the application relies on the previous behavior of default factories.\n\n

Why This Fix Works in Production

Trigger: def get_default(self, *, call_default_factory: bool = False, validated_data: dict[str, Any] | None = None) -> Any:
Mechanism: Relaxed the check for validated data in default factory utilities to prevent breaking changes in Pydantic 2.10.

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: def get_default(self, *, call_default_factory: bool = False, validated_data: dict[str, Any] | None = None) -> Any:

Proof / Evidence

GitHub issue: #10912
Fix PR: https://github.com/pydantic/pydantic/pull/10909
Reproduced locally: No (not executed)
Last verified: 2026-02-11
Confidence: 0.60
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.23

Discussion

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

Jump to Sources Open on GitHub

“Hey folks! We've just released v2.10.1 with a fix for this issue! Let us know if you're still experiencing any difficulties. Thanks!”

@sydney-runkle · 2024-11-22 · confirmation · source

“Just wanted to chime in that this broke creating new instances of SqlModels in the last few hours; will try and read through to understand…”

@joshuamckenty · 2024-11-21 · source

“> Any update on this? Broke our whole system. Let me know if we can help. Anyone knows the last working pydantic version? We should…”

@sydney-runkle · 2024-11-21 · source

“> EDIT: ok I think I get it. https://github.com/pydantic/pydantic/pull/10678, that's what we need to pass if we're going to tell it to call_default_factory at this…”

@zzstoatzz · 2024-11-21 · source

Failure Signature (Search String)

def get_default(self, *, call_default_factory: bool = False, validated_data: dict[str, Any] | None = None) -> Any:

Error Message

Stack trace

error.txt

Error Message
-------------
def get_default(self, *, call_default_factory: bool = False, validated_data: dict[str, Any] | None = None) -> Any:
    ...
        if self.default_factory is None:
            return _utils.smart_deepcopy(self.default)
        elif call_default_factory:
            if validated_data is None:
              raise ValueError("'validated_data' must be provided if 'call_default_factory' is True.")
E               ValueError: 'validated_data' must be provided if 'call_default_factory' is True.

Stack trace

error.txt

Error Message
-------------
» python sandbox/repros/pydantic210.py
Traceback (most recent call last):
  File "/Users/nate/github.com/prefecthq/prefect/sandbox/repros/pydantic210.py", line 32, in <module>
    main()
  File "/Users/nate/github.com/prefecthq/prefect/sandbox/repros/pydantic210.py", line 28, in main
    task.reset_fields()
  File "/Users/nate/github.com/prefecthq/prefect/sandbox/repros/pydantic210.py", line 12, in reset_fields
    field: self.model_fields[field].get_default(call_default_factory=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/nate/github.com/prefecthq/prefect/.venv/lib/python3.12/site-packages/pydantic/fields.py", line 596, in get_default
    raise ValueError("'validated_data' must be provided if 'call_default_factory' is True.")
ValueError: 'validated_data' must be provided if 'call_default_factory' is True.

</details>

Stack trace

error.txt

Error Message
-------------
» uv run --with prefect==3.1.3 --with pydantic==2.10.0  sandbox/repros/pydantic210.py
Traceback (most recent call last):
  File "/Users/nate/github.com/prefecthq/prefect/sandbox/repros/pydantic210.py", line 34, in <module>
    main()
  File "/Users/nate/github.com/prefecthq/prefect/sandbox/repros/pydantic210.py", line 28, in main
    task.reset_fields()
  File "/Users/nate/github.com/prefecthq/prefect/sandbox/repros/pydantic210.py", line 12, in reset_fields
    field: self.model_fields[field].get_default(call_default_factory=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/nate/github.com/prefecthq/prefect/.venv/lib/python3.12/site-packages/pydantic/fields.py", line 596, in get_default
    raise ValueError("'validated_data' must be provided if 'call_default_factory' is True.")
ValueError: 'validated_data' must be provided if 'call_default_factory' is True.



» uv run --with prefect==3.1.3 --with pydantic@git+https://github.com/pydantic/pydantic.git@validated-data-fix sandbox/repros/pydantic210.py
 Updated https://github.com/pydantic/pydantic.git (69e509ef)
name='test-task' tags=['new-tag']

Minimal Reproduction

repro.py

from typing import ClassVar, List, Set

from pydantic import BaseModel, Field


class PrefectBaseModel(BaseModel):
    _reset_fields: ClassVar[Set[str]] = set()

    def reset_fields(self):
        return self.model_copy(
            update={
                field: self.model_fields[field].get_default(call_default_factory=True)
                for field in self._reset_fields
            }
        )


class TaskRun(PrefectBaseModel):
    _reset_fields: ClassVar[Set[str]] = {"tags"}

    name: str
    tags: List[str] = Field(default_factory=list)


def main():
    task = TaskRun(name="test-task")
    task.tags.append("new-tag")
    task.reset_fields()


if __name__ == "__main__":
    main()

Environment

Python: 3.12
Pydantic: 2

Fix Options (Details)

Option A — Apply the official fix

Relaxed the check for validated data in default factory utilities to prevent breaking changes in Pydantic 2.10.

When NOT to use: This fix should not be used if the application relies on the previous behavior of default factories.

Option C — Workaround Temporary workaround

version above

When NOT to use: This fix should not be used if the application relies on the previous behavior of default factories.

Use only if you cannot change versions today. Treat this as a stopgap and remove once upgraded.

Fix reference: https://github.com/pydantic/pydantic/pull/10909

Last verified: 2026-02-11. Validate in your environment.

When NOT to Use This Fix

This fix should not be used if the application relies on the previous behavior of default factories.

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.

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 2.10: `validated_data` must be provided if `call_default_factory` is True (affets: (Fix)

The Fix

Why This Fix Works in Production

Why This Breaks in Prod

Proof / Evidence

Discussion

Failure Signature (Search String)

Error Message

Minimal Reproduction

Environment

Fix Options (Details)

Option A — Apply the official fix

Option C — Workaround Temporary workaround

Get updates

When NOT to Use This Fix

Verify Fix

Did This Fix Work in Your Case?

Prevention

Related Issues

Sources