Exporting Gemma-3 models to ONNX is broken

[dvdplm]

System Info

optimum v1.27.0, python 3.13, macos

Who can help?

@michaelbenayoun

Information

• The official example scripts
• My own modified scripts

Tasks

• An officially supported task in the examples folder (such as GLUE/SQuAD, ...)
• My own task or dataset (give details below)

Reproduction (minimal, reproducible, runnable)

Running

uv run optimum-cli export onnx --model google/gemma-3-4b-it-qat-q4_0-unquantized --task text-generation gemma-3-4b/

Results in the following error:

Traceback (most recent call last):
  File "/REDACTED_PATH_TO_PROJECT_DIR/.venv/bin/optimum-cli", line 10, in <module>
    sys.exit(main())
             ~~~~^^
  File "/REDACTED_PATH_TO_PROJECT_DIR/.venv/lib/python3.13/site-packages/optimum/commands/optimum_cli.py", line 208, in main
    service.run()
    ~~~~~~~~~~~^^
  File "/REDACTED_PATH_TO_PROJECT_DIR/.venv/lib/python3.13/site-packages/optimum/commands/export/onnx.py", line 276, in run
    main_export(
    ~~~~~~~~~~~^
        model_name_or_path=self.args.model,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<23 lines>...
        **input_shapes,
        ^^^^^^^^^^^^^^^
    )
    ^
  File "/REDACTED_PATH_TO_PROJECT_DIR/.venv/lib/python3.13/site-packages/optimum/exporters/onnx/__main__.py", line 418, in main_export
    onnx_export_from_model(
    ~~~~~~~~~~~~~~~~~~~~~~^
        model=model,
        ^^^^^^^^^^^^
    ...<19 lines>...
        **kwargs_shapes,
        ^^^^^^^^^^^^^^^^
    )
    ^
  File "/REDACTED_PATH_TO_PROJECT_DIR/.venv/lib/python3.13/site-packages/optimum/exporters/onnx/convert.py", line 1044, in onnx_export_from_model
    raise ValueError(
        f"Trying to export a {model_type} model, that is a custom or unsupported architecture, but no custom onnx configuration was passed as `custom_onnx_configs`. Please refer to https://huggingface.co/docs/optimum/main/en/exporters/onnx/usage_guides/export_a_model#custom-export-of-transformers-models for an example on how to export custom models. Please open an issue at https://github.com/huggingface/optimum/issues if you would like the model type {model_type} to be supported natively in the ONNX export."
    )
ValueError: Trying to export a gemma3 model, that is a custom or unsupported architecture, but no custom onnx configuration was passed as `custom_onnx_configs`. Please refer to https://huggingface.co/docs/optimum/main/en/exporters/onnx/usage_guides/export_a_model#custom-export-of-transformers-models for an example on how to export custom models. Please open an issue at https://github.com/huggingface/optimum/issues if you would like the model type gemma3 to be supported natively in the ONNX export.

Given #67 has been reported&fixed, I infer that my problem above is a proper bug.

Expected behavior

optimum-cli can export gemma-3 models to onnx

[IlyasMoutawwakil]

Sorry about the confusion, the issue you mentioned was closed by mistake (automatically, upon another PR merging)
The gemma3 model support was never added, and I don't have bandwidth for it right now but more than happy to review a PR 🤗

[geraldstanje1]

saw the same. @dvdplm did you find any alternative?

[simondanielsson]

Happy to have a go at this.

I would be immensely grateful if you could have a look at my question here: #49

[IlyasMoutawwakil]

text generation is supported as of #70