I cannot see the images, but if it’s a black line near the top of the window, then yes, it’s a bug (and a weird one). It’s not new to that version (a customer reported it on 2025.1). I am having trouble reproducing it. It seems to be related to having tabs and also to the toolbar disconnecting from the left sidebar. If you have steps that always make it happen, please share them, so I can reproduce and fix the bug.