Well, I'm not going to share either solution as this is actually a pretty useful utility that I plan on releasing, but the short answer is: 1) don't use ScreenCaptureKit, and 2) take advantage of what CGWindowListCreateImage() offers through the content server. This is a simple IPC mechanism that does not trigger all the SKC limitations (i.e., no multi-space or multi-desktop support). In fact, when using SKC, the user cannot even minimize the "watched" window.

Claude realized those issues right from the start.

One of the trickiest parts is tracking the window content while the window is moving - the content server doesn't, natively, provide that information.