I know from other issues/PRs (e.g., #40) that making cffi actually thread-safe is a big task. However, a small but easier step is to produce free-threaded wheels. As mentioned in https://docs.python.org/3.13/howto/free-threading-extensions.html#module-initialization

Extension modules need to explicitly indicate that they support running with the GIL disabled; otherwise importing the extension will raise a warning and enable the GIL at runtime.

Thus, providing FT wheels doesn't necessarily mean the extension supports it, it simply allows the package to be installed in a FT installation.

I do understand that providing such wheels could make some users believe that cffi is fully multi-threaded. As long as expectations are made clear that hopefully shouldn't be an issue, but that's very easy to say.

In my case I'm trying to provide FT builds of my library (with hopefully actual thread-safe code), and cffi is an optional dependency (rarely used though from what I know). I'm not running multi-threaded code in my tests (yet), and even if I did python would should re-enable the GIL when importing cffi.