Pydantic `validate_call` doesn't use types from local scope

The Fix

pip install pydantic==2.8.0

Based on closed pydantic/pydantic issue #9744 · 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

@@ -307,6 +307,7 @@ def get_function_type_hints(
     globalns = add_module_globals(function)
     type_hints = {}
+    type_params: tuple[Any] = getattr(function, '__type_params__', ())  # type: ignore
     for name, value in annotations.items():
         if include_keys is not None and name not in include_keys:

repro.py

from __future__ import annotations

import pydantic


class M1(pydantic.BaseModel):
    x: int


M = M1


def foo():
    class M2(pydantic.BaseModel):
        y: str

    M = M2

    class Outer(pydantic.BaseModel):
        m: M

    print(repr(Outer(m={'y': 'abc'})))  # Outer(m=M2(y='abc'))

    @pydantic.validate_call
    def bar(m: M) -> M:
        return m

    print(repr(bar({'x': 1})))  # M1(x=1)


foo()

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==2.8.0\nWhen NOT to use: Do not use this fix if local type hints are not required.\n\n

Why This Fix Works in Production

Trigger: `validate_call` doesn't use types from local scope
Mechanism: `validate_call` only used types from the global namespace instead of local scope
Why the fix works: `validate_call` now correctly uses types from the local scope, addressing the issue where it only utilized types from the global namespace. (first fixed release: 2.8.0).

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

`validate_call` only used types from the global namespace instead of local scope
Production symptom (often without a traceback): `validate_call` doesn't use types from local scope

Proof / Evidence

GitHub issue: #9744
Fix PR: https://github.com/pydantic/pydantic/pull/9760
First fixed release: 2.8.0
Reproduced locally: No (not executed)
Last verified: 2026-02-09
Confidence: 0.85
Did this fix it?: Yes (upstream fix exists)
Own content ratio: 0.54

Discussion

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

Jump to Sources Open on GitHub

“### Initial Checks - [X] I confirm that I'm using Pydantic V2 ### Description @pydantic.validate_call only uses types from the global namespace, not locals. BaseModel doesn't have this problem. ### Example Code ### Python, Pydantic & OS Ver”

Issue thread · issue description · source

Failure Signature (Search String)

`validate_call` doesn't use types from local scope
`@pydantic.validate_call` only uses types from the global namespace, not locals. `BaseModel` doesn't have this problem.

Copy-friendly signature

signature.txt

Failure Signature
-----------------
`validate_call` doesn't use types from local scope
`@pydantic.validate_call` only uses types from the global namespace, not locals. `BaseModel` doesn't have this problem.

Error Message

Signature-only (no traceback captured)

error.txt

Error Message
-------------
`validate_call` doesn't use types from local scope
`@pydantic.validate_call` only uses types from the global namespace, not locals. `BaseModel` doesn't have this problem.

Minimal Reproduction

repro.py

from __future__ import annotations

import pydantic


class M1(pydantic.BaseModel):
    x: int


M = M1


def foo():
    class M2(pydantic.BaseModel):
        y: str

    M = M2

    class Outer(pydantic.BaseModel):
        m: M

    print(repr(Outer(m={'y': 'abc'})))  # Outer(m=M2(y='abc'))

    @pydantic.validate_call
    def bar(m: M) -> M:
        return m

    print(repr(bar({'x': 1})))  # M1(x=1)


foo()

Environment

Pydantic: 2

What Broke

Incorrect type validation leading to runtime errors in function calls.

Why It Broke

`validate_call` only used types from the global namespace instead of local scope

Fix Options (Details)

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

pip install pydantic==2.8.0

When NOT to use: Do not use this fix if local type hints are not required.

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/9760

First fixed release: 2.8.0

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

When NOT to Use This Fix

Do not use this fix if local type hints are not required.

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
2.8.0	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 `validate_call` doesn't use types from local scope (Fix)