[porridgeraisin]

Not to detract from your overall point, but the app is not resetting the clipboard. In X11 if you close any app, you lose anything you copy from it. This is because in X11 windows do message passing to emulate a clipboard. Your browser say and fsearch send messages to each other to send data in few KB chunks(yes there's an incremental transfer protocol where you have to support all kinds of irrelevant clients even if the last such client died before the turn of the century) So when one of the windows closes, it's gg. It's a pretty convoluted over-engineered idea when instead a single file ~/. clipboard would have sufficed.

For a more articulated rant from 20 years ago, see the rant file in https://github.com/porridgewithraisins/x11cp. Also shameless plug.

To fix this, use a clipboard manager. Also shameless plug https://github.com/porridgewithraisins/coffee-pesto :)