Build failure on Python 3.14 Free-threaded (cp314t): Py_LIMITED_API is incompatible with Py_GIL_DISABLED

[dreampuf]

Description

I am attempting to install brotlicffi using the experimental Python 3.14 Free-threaded build (CPython 3.14t). The build fails during bdist_wheel creation.

The error occurs because brotlicffi is configured to build a Limited API wheel (Stable ABI) in setup.py, but the Limited API is currently explicitly disabled/incompatible with free-threaded (No-GIL) Python builds.

Reproduction Steps

1. Install Python 3.14 (Free-threaded).
2. Attempt to pip install brotlicffi.

# Using uv for reproduction
uv python install 3.14
uv run --python 3.14 pip install brotlicffi

Traceback

Traceback (most recent call last):
  ...
  File ".../setuptools/command/bdist_wheel.py", line 285, in _validate_py_limited_api
    raise ValueError(
ValueError: `py_limited_api='cp314'` not supported. `Py_LIMITED_API` is currently incompatible with `Py_GIL_DISABLED`. See https://github.com/python/cpython/issues/111506.

Analysis

The issue stems from setup.py hardcoding the py_limited_api option:

https://github.com/python-hyper/brotlicffi/blob/main/setup.py#L79

self.py_limited_api = "cp3{}".format(sys.version_info[1])

According to the CPython issue #111506, free-threaded builds do not support the stable ABI.

Suggested Fix

I'm not sure whether it's safe to omit the py_limited_api option when running on a free-threaded interpreter. If so, should we remove it from setup.py?

Environment

• OS: macOS (ARM64)
• Python: CPython 3.14.0+freethreaded
• brotlicffi version: 1.1.0.0