The code works except that I am struggling with getting the box to not expand to the right which exposes the background past the scaled down border. This is the XIB in question without these changes: https://github.com/HearthSim/HSTracker/blob/master/HSTracker/UIs/Battlegrounds/Base.lproj/BattlegroundsSession.xib Let me know if you have any suggestions

Thanks, this mostly works. My hierarchy is like this: Window NSBox with custom background +- NSStackView ... I added a wrapper NSView around the NSBox and followed your suggestion:      guard let window else {       return     }     let bounds = sessionPanel.bounds     let sw = bounds.width * 0.9     let sh = bounds.height * 0.9     outerBox.frame = NSRect(x: 0, y: window.frame.height - sh, width: sw, height: sh)     outerBox.bounds = bounds

Wouldn't that always crash though? This doesn't have a very large number of reports, so it is not happening that consistently. I have never seen this crash on my local development machine either. I double checked the connection the XIB source and nothing really looked out of the ordinary. I would have expected a corruption to always crash when running under the debugger.