That’s my default as well, worked great, except on a machine with shared sessions, a test driver machine where several of us will login as the same user: some of those people come from windows machines where ctrl-space gets mapped to ctrl-@, which is NUL.

So we had to find another prefix for those machines; fortunately, tmux can have two.

This (space->@->NUL) is mentioned in the tmux docs, tbh.