macOS 26 windows are hard to resize because they aren’t really rounded

Source: 9to5Mac

Problem description

One of the things I noticed after upgrading to macOS 26 was that I would sometimes fail when trying to resize windows – I’d tried to grab the corner, but nothing would happen.
It turns out that this isn’t clumsiness on my part, but rather a design error by Apple – and that’s because the corners of windows aren’t actually rounded in the way the UI suggests.