Contributing to MLX-VLM

Use this workflow to shape a contribution so it lands cleanly. It reflects the current mlx_vlm/ layout (note: CONTRIBUTING.md still points at an older src/ layout, the real paths are below).

Setup

git clone https://github.com/<you>/mlx-vlm && cd mlx-vlm
uv pip install -e .            # editable install (or: pip install -e .)

Where things go

• Model code: mlx_vlm/models/<model_type>/, and the file name matches the config.json model_type (e.g. llava). A new kernel or helper goes in its own file in that model directory, not bolted into language.py. To add a whole new model, use Skill("mlx-vlm-skills:add-new-model").
• Config args: add to the model's ModelConfig (in <model>/config.py) with an inline # comment, and keep them backward-compatible, a default of None/0/False must reproduce the original behavior so existing checkpoints and configs are unaffected. Gate new features so they are opt-in.
• Tests: add to mlx_vlm/tests/test_models.py as a class per feature (e.g. TestMyFeature). Do not create a standalone test_<feature>.py, repo convention keeps model tests in test_models.py. Prefer cheap synthetic/random-weight tests (tiny configs) and check exactness against the original path in the degenerate limit (feature disabled == baseline).

Run the tests

cd mlx_vlm && uv run --with pytest python -m pytest tests/test_models.py -q -k "<ClassName>"

Formatting, install and run pre-commit

Before opening a PR, install the pre-commit hooks once and run them. The repo uses pre-commit (black for Python, clang-format for C++); PRs are expected to be hook-clean.

pip install pre-commit
pre-commit install                 # install the git hooks (run once per clone)

# run on the files you changed
pre-commit run --files <file1.py> <file2.py>
# or check everything
pre-commit run --all-files