> > The only situation where they can diverge is if the Emacs executable
> > was recompiled while the current one is running, and then we could add
> > some form of version check to protect against it.
>
> That happens to me sometimes as well,

Me too. And I suspect many others on this list as well.

> but in that case I've pointed the
> gun at my own foot and pulled the trigger :-) I'd consider it rare
> enough that you don't need to expend a lot of effort to prevent it.

Not only that, but even when it does happens it's unlikely to cause problems. Because the background process does very little interaction with the running Emacs, even different versions should be mostly safe.