PR #44978: fix: handle absent sys.modules entry in modeling_utils

• Repository: huggingface/transformers
• Author: cjkindel
• State: closed | merged: False
• Link: https://github.com/huggingface/transformers/pull/44978

Description (problem / solution / changelog)

What does this PR do?

_can_set_attn_implementation and _can_set_experts_implementation both do a direct subscript lookup into sys.modules:

class_module = sys.modules[cls.__module__]

If the module is not registered under its dotted name in sys.modules — which can happen with lazy loaders, frozen importers, or certain packaging environments on Windows — this raises a KeyError instead of returning False as intended.

The existing comment already acknowledges this class of problem ("This can happen for a custom model in a jupyter notebook or repl for example") but the file guard only ran after the subscript, so it never had a chance to fire.

First introduced: commit 0642963 (PR #42697, merged January 5, 2026).

Real-world traceback reported by Griptape Nodes users:

KeyError: 'transformers.models.clip.modeling_clip'
  modeling_utils.py, in _can_set_experts_implementation
    class_module = sys.modules[cls.__module__]

Reproducing code:

import sys
from transformers.models.clip.modeling_clip import CLIPTextModel, CLIPTextConfig

# Simulate condition where module is absent from sys.modules
del sys.modules["transformers.models.clip.modeling_clip"]

config = CLIPTextConfig()
CLIPTextModel(config)  # KeyError before this fix, succeeds after

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• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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@ArthurZucker (original author) @CyrilVallez (model loading)

Closes https://github.com/huggingface/transformers/issues/45003

Changed files

• src/transformers/modeling_utils.py (modified, +4/-4)

PR #45015: fix: guard sys.modules access in _can_set_attn/experts_implementation

• Repository: huggingface/transformers
• Author: pnehete23
• State: closed | merged: False
• Link: https://github.com/huggingface/transformers/pull/45015

Description (problem / solution / changelog)

What does this PR do?

Fixes a KeyError in _can_set_attn_implementation and _can_set_experts_implementation when a model's module is absent from sys.modules.

Fixes #45003

Root Cause

Both _can_set_attn_implementation (line 1951) and _can_set_experts_implementation (line 1970) use a direct dictionary subscript:

class_module = sys.modules[cls.__module__]

This raises KeyError when the module is not registered in sys.modules — which happens with lazy loaders, frozen importers, or tools like Griptape Nodes that manipulate the module registry.

The existing comment on the very next line already acknowledges this class of scenario ("This can happen for a custom model in a jupyter notebook or repl"), but the __file__ guard only runs after the dictionary access, so it never fires.

Fix

Replace sys.modules[cls.__module__] with sys.modules.get(cls.__module__) and add a class_module is None check alongside the existing hasattr guard. Both functions now gracefully return False instead of crashing.

Tests

Added TestCanSetImplementationWithMissingSysModule with 3 tests:

• _can_set_attn_implementation returns False when module is missing from sys.modules
• _can_set_experts_implementation returns False when module is missing from sys.modules
• Full model initialization succeeds when module is missing from sys.modules

All existing TestAttentionImplementation tests continue to pass.

Code Agent Policy

• I confirm that this is not a pure code agent PR.

Changed files

• src/transformers/modeling_utils.py (modified, +8/-6)
• tests/utils/test_modeling_utils.py (modified, +47/-0)