Add Python 3.14 free-threaded (cp314t) wheel support

[clemlesne]

Summary

With the release of Python 3.14, the new free-threaded (no-GIL) mode is becoming more widely used. It would be great if PyMuPDF could provide prebuilt wheels and confirm compatibility with python3.14t (the free-threaded ABI).

Current State

• PyMuPDF supports Python 3.14 (standard build) per the changelog
• However, PyPI shows no cp314t wheels for the free-threaded build
• Free-threaded Python uses the cp314t wheel tag (note the t suffix)

What's Needed

1. Update CI (cibuildwheel) to build cp314t wheels
2. Declare GIL compatibility using Py_mod_gil slot in module definition (per PEP 703)
3. Test under free-threaded Python to ensure thread safety

Resources

• Python Free-Threading Guide
• Free-Threaded Wheels Tracker
• PEP 703 – Making the GIL Optional
• cibuildwheel free-threaded docs

[JorjMcKie]

Sorry, we cannot do this due to our internal architecture.
The existence of the GIL never was a reason why we did not support threading. Consequently, the "no-GIL" option means no change either.

[clemlesne]

| The existence of the GIL never was a reason why we did not support threading.

The primary issue there, from my own point of view.

I'm running all the services under 3.14t and there is no pre-built wheel for PyMuPDF. It generates slow builds and frustration using the lib. Publishing a pre-built wheel would make life easier for all lib users.

Cython gives locks (https://cython.readthedocs.io/en/latest/src/userguide/freethreading.html#locks) if some underlying code is not thread safe it could allow to make it no-gil compatible without breaking too much.

[julian-smith-artifex-com]

The latest pymupdf git has some minor fixes to wheel generation and tests, so we should be able to build wheels for 3.14t next time we release.

Pymupdf does not declare compatibility with free-threading, so python-3.14t will automatically run with the GIL enabled and output a warning.

[julian-smith-artifex-com]

Yesterday's release of pymupdf-1.27.2 includes a wheel built specifically for python-3.14t:

pymupdf-1.27.2-cp314-cp314t-manylinux_2_28_x86_64.whl

As explained above, this does not add any thread-safety, and python-3.14t will automatically run with the GIL enabled and output a warning.