diff --git a/README.md b/README.md index 1448405f4..af0e5ecd5 100644 --- a/README.md +++ b/README.md @@ -11,6 +11,26 @@ This action provides the following functionality for GitHub Actions users: - Optionally caching dependencies for pip, pipenv and poetry - Registering problem matchers for error output +# Free-threaded Python Support + +This is a fork of the "official" setup-python GitHub Action. We made this +available to allow setting up CI with free-threaded Python while we wait for +official [upstream +support](https://github.com/actions/setup-python/issues/771). Hopefully, [coming +soon](https://github.com/actions/setup-python/issues/771#issuecomment-2490607417). + +## Caveats + +Since setup-python relies on the Python.org installers, the [limitations](https://github.com/python/cpython/issues/127294#issuecomment-2501787837) related to installing free-threaded Python on Windows are also present here. + +In particular, if you install both a free-threaded and standard build of Python +(e.g. both versions `3.13` and `3.13t`) in the same Actions environment, only +one of the specified versions [will end up installed on the +runner](https://github.com/Quansight-Labs/setup-python/issues/5#issue-2714826484). + +To work around this limitation, we suggest ensuring that any CI runs using the +free-threaded build on Windows only activate one Python version. + ## Basic usage See [action.yml](action.yml)