+ /* This is what the evil WM does to us: Resize the window behind our back. */
I think gitlab CI is running fvwm2 instead of evilwm...
I happen to be rather fond of fvwm, but IIRC it does have the issue of not updating it's screen size in response to RandR mode changes, which I guess is what we're running into here. I think RandR support is supposed to be improved in fvwm3, fwiw.