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#12610·pydantic

No ForwardRef in model_fields annotations with list['Model'] field type with legacy-style annotations (w/o from __future__ import annotations)

Author: AntonOvsyannikovCreated Dec 4, 2025Updated Sep 16, 2026
Labelsbug V2topic-annotations

Initial Checks

  • I confirm that I'm using Pydantic V2

Description

There is no ForwardRef in model_fields annotations with list['Model'] field type with legacy-style annotations (w/o from __future__ import annotations) when forward model name is declared as string literal.

So model_rebuild() does not work correctly, and after rebuild there is no actual type in field annotation.

If we take a look into captured annotations, we'll see that event before rebuild annotation is not a ForwardRef.

python
class Foo(BaseModel):
    bar1: 'Bar'
    bar2: list['Bar']


class Bar(BaseModel):
    pass


print(Foo.model_fields['bar1'].annotation)  # ForwardRef('Bar') OK
print(Foo.model_fields['bar2'].annotation)  # list['Bar'] ???

Foo.model_rebuild()

print(Foo.model_fields['bar1'].annotation)  # <class '__main__.Bar'> OK
print(Foo.model_fields['bar2'].annotation)  # list['Bar'] ???

with from __future__ import annotations PEP563 annotations everything works as expected

python
class Foo(BaseModel):
    bar1: Bar
    bar2: list[Bar]


class Bar(BaseModel):
    pass


print(Foo.model_fields['bar1'].annotation)  # ForwardRef('Bar') OK
print(Foo.model_fields['bar2'].annotation)  # ForwardRef('list[Bar]') OK

Foo.model_rebuild()

print(Foo.model_fields['bar1'].annotation)  # <class '__main__.Bar'> OK
print(Foo.model_fields['bar2'].annotation)  # list[__main__.Bar] OK

Example Code

python
# from __future__ import annotations
import sys

import pydantic
from pydantic import BaseModel

print(sys.version)  # 3.10.4 (tags/v3.10.4:9d38120, Mar 23 2022, 23:13:41) [MSC v.1929 64 bit (AMD64)]
print(pydantic.version.VERSION)  # 2.12.5


class Foo(BaseModel):
    bar1: 'Bar'
    bar2: list['Bar']


class Bar(BaseModel):
    pass


print(Foo.model_fields['bar1'].annotation)  # ForwardRef('Bar') OK
print(Foo.model_fields['bar2'].annotation)  # list['Bar'] ???
print()
Foo.model_rebuild()
print(Foo.model_fields['bar1'].annotation)  # <class '__main__.Bar'> OK
print(Foo.model_fields['bar2'].annotation)  # list['Bar'] ???

Python, Pydantic & OS Version

> python -c "import pydantic.version; print(pydantic.version.version_info())"
             pydantic version: 2.12.5
        pydantic-core version: 2.41.5
          pydantic-core build: profile=release pgo=false
               python version: 3.10.4 (tags/v3.10.4:9d38120, Mar 23 2022, 23:13:41) [MSC v.1929 64 bit (AMD64)]
                     platform: Windows-10-10.0.26200-SP0
             related packages: fastapi-0.123.5 mypy-1.16.1 typing_extensions-4.15.0
                       commit: unknown

Source: pydantic/pydantic

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