> Having to have thread safe code all over the place just for the 1% of users who need to have multi-threading in Python and can't use subinterpreters for some reason is nuts.

Way more than 1% of the community, particularly of the community actively developing Python, wants free-threaded. The problem here is that the Python community consists of several different groups:

1. Basically pure Python code with no threading

2. Basically pure Python with appropriate thread safety

3. Basically pure Python code with already broken threaded code, just getting lucky for now

4. Mixed Python and C/C++/Rust code, with appropriate threading behavior in the C or C++ components

5. Mixed Python and C or C++ code, with C and C++ components depending on GIL behavior

Group 1 gets a slightly reduced performance. Groups 2 and 4 get a major win with free-threaded Python, being able to use threading through their interfaces to C/C++/Rust components. Group 3 is already writing buggy code and will probably see worse consequences from their existing bugs. Group 5 will have to either avoid threading in their Python code or rewrite their C/C++ components.

Right now, a big portion of the Python language developer base consists of Groups 2 and 4. Group 5 is basically perceived as holding Python-the-language and Python-the-implementations back.

Where is the major win? Sorry but I just don't see the use case for free-threading.

Native code can already be multi-threaded so if you are using Python to drive parallelized native code, there's no win there. If your Python code is the bottleneck, well then you could have subinterpreters with shared buffers and locks. If you really need to have shared objects, do you actually need to mutate them from multiple interpreters? If not, what about exploring language support for frozen objects or proxies?

The only thing that free threading gives you is concurrent mutations to Python objects, which is like, whatever. In all my years of writing Python I have never once found myself thinking "I wish I could mutate the same object from two different threads".