The constrained layout guide warns that
Currently Constrained Layout is experimental . The behaviour and API are subject to change, or the whole functionality may be removed without a deprecation period.
Is there a roadmap for considering it part of the stable API? I would like to use it in a library, but would not do so with the current warning.
Yes, its pretty stable and we are dropping the warning for 3.3.
OTOH, it doesn’t work miracles, so if you run into problems, let us know and we can try and fix.
Its possible some things under the hood will change, and that could lead to different output (as opposed to actual API differences), but we will try and minimize that.
BTW you may be interested in https://github.com/matplotlib/matplotlib/pull/17246 which attempts to squeeze axes together when they leave a lot of empty space (i.e. for fixed-aspect plots). However, it may be too preliminary to use robustly in seaborn and other downstream packages.