Hello Everyone, As you might know, tox4 broke almost all the projects tox.ini and so do master as well as stable branches gate. On the master, we need to fix it as we should use tox4 in testing. To fix the stable branches gate, either we need to backport all the fixes which include some more issues fixes[1] or we can pin the tox<4. We discussed it in today's TC meeting and it is better to keep testing the stable branch with the tox version that they were released with and not with the tox4. Even in future, there might be the cases where latest tox might introduce more incompatible changes. By considering all these factors, it is better to pin tox<4 for stable branches (<=stable/zed) testing. I have prepared the patch to pin it in the common job/template, feel free to comment with your feedback/opinion: - https://review.opendev.org/c/openstack/openstack-zuul-jobs/+/867849/3 also, tested with nova/cinder stable branches: - https://review.opendev.org/q/I0ca55abf9975c5a3f9713ac5dd5be39083e04554 - https://review.opendev.org/q/I300e7804a27d08ecd239d1a7faaf2aaf3e07b9ee You can also test it in your project stable branches in case any different syntax in tox.ini causing the tox upgrade to the latest. [1] https://github.com/tox-dev/tox/issues/2712 -gmann