I think OBS just captures the pixels on your display, not the logical windows themselves. So OBS doesn't know anything about your windows aside from maybe the f

I think OBS just captures the pixels on your display, not the logical windows themselves. So OBS doesn't know anything about your windows aside from maybe the first one to get the dimensions/position of the rectangle to capture. The recursion you're seeing is just old pixels from a previous capture that were copied into a new capture. It's the same thing that happens if you connect a video camera so its output is displayed on a TV/computer, then point the video camera at that output. To the video/camera computer system, it's no different than if there were no recursion "loop." A special case is a microphone + speaker. If you feed the speaker output from the microphone back to the microphone, there's a feedback loop that amplifies the signal making that really loud humming sound.