Consistent Tab/Window Size With Multiple Tabs With a Border...

See this thread for a fulld description of the issue along with screen recordings:

https://community.adobe.com/t5/photoshop-ecosystem-discussions/window-behavior/m-p/15321221#M865058

Between version 22.2 and 25.12 something changed in the behavior of tabbed winodows with a boarder around the image. Prior to 22.2 if I had multiple images open in a window and pulled the winodw area wider than the image to create a border, the border size would remain consistent from tab to tab. Now the window size jumps around all over the place when going from tab to tab.

At the very least you should have a setting to make "window size consistent" when you have a window with multiple tabs.