`setup.cfg` causes `tox.toml` to be ignored and fail with `HandledError| SetupCfg ...`

[cpburnz]

Issue

A setup.cfg prevents tox.toml from being used which causes tox to fail with the following error:

ROOT: HandledError| SetupCfg failed loading /home/caleb/tox-issue/setup.cfg due to section tox:tox not found

I think the problem is setup.cfg has a higher priority than tox.toml unlike tox.ini.

Why am I using setup.cfg? I'm the author of pathspec, and in order to support setuptools installs on old versions of Red Hat / Fedora, I generate setup.cfg from pyproject.toml. I currently use tox.ini to configure tox, and was looking to switch to tox.toml because it's the recommended config.

Environment

Provide at least:

• OS: Manjaro Linux 25.0.10 (Arch Linux derivative)
• Python 3.14.0

Output of pip list of the host Python, where tox is installed

Package       Version
------------- -------
cachetools    6.2.2
chardet       5.2.0
colorama      0.4.6
distlib       0.4.0
filelock      3.20.0
packaging     25.0
pip           25.2
platformdirs  4.5.0
pluggy        1.6.0
pyproject-api 1.10.0
tox           4.32.0
virtualenv    20.35.4

Output of running tox

Output of tox -rvv

ROOT: HandledError| SetupCfg failed loading /home/caleb/tox-issue/setup.cfg due to section tox:tox not found

Minimal example

python3.14 -m venv .venv
. .venv/bin/activate
pip install tox
touch setup.cfg
echo 'env_list = ["3.14"]' > tox.toml
tox