I don't think you need it in all cases. For instance, if the "world" / "tab" knows that it's no good, it could self-exit. That'd leave only the "good" one sta

I don't think you need it in all cases. For instance, if the "world" / "tab" knows that it's no good, it could self-exit. That'd leave only the "good" one standing without any coordination / communication. Or, in some other cases, return codes may be good enough. Even if it's easily possible with current stuff though, it's still an interesting idea.