I've discovered that if I go into "copy mode" or "scrollback mode" in a byobu screen, detach from it and leave it running, the buffer will fill up and eventually block the process I'm running in the screen. (Presumably because the process is prevented from writing to stdout, since there's no one to consume the bytes.)
This behaviour is kind of devastating. Is it possible to for instance
Automatically exit copy / scrollback mode upon detaching from the screen,
or
Let the position of the view which is in copy / scrollback mode move forward once the buffer is full, to allow for the process to continue executing
Happy to hear of any advice on this.
Your assessment is correct, the program running within the scrollback-mode window is stopping because its output buffer is full and it is suspended waiting to write. This behavior is both correct and desirable; the user entered scrollback mode to view the screen contents but as you have noticed, this is not convenient nor obvious when the session is detached.
Unfortunately it appears to be a missing feature in both gnu-screen and tmux. byobu wouldn't be able to fix it in a wrapper because it can't detect the scrollback state of a given window, nor can it break a window out of it using external commands, though it could send commands to the terminal like the user would, were it able to detect or remember the scrollback state. Neither screen nor tmux appear to include a feature to enable automatically reverting from scrollback mode when the terminal is detached. A patch would be required.