[rogerbinns]

This has already been done. There is a 't' suffix in the ABI tag.

You have to explicitly compile the extension against a free threaded interpreter in order to get that ABI tag in your extension and even be able to load the extension. The extension then has to opt-in to free threading in its initialization.

If it does not opt-in then a message appears saying the GIL has been enabled, and the interpreter continues to run with the GIL.

This may seem a little strange but is helpful. It means the person running Python doesn't have to keep regular and free threaded Python around, and duplicate sets of extensions etc. They can just have the free threaded one, anything loaded that requires the GIL gives you the normal Python behaviour.

What is a little more problematic is that some of the standard library is marked as supporting free threading, even though they still have the audit and update work outstanding.

Also the last time I checked, the compiler thread sanitizers can't work with free threaded Python.