There are 2 settings necessary for this set up to work as expected. Inside ~/.tmux.conf you need:

bind-key -n c-g send-prefix
bind-key -n c-t send-keys c-g

for prefix key access to nested windows. The default prefix is ctrl+b, so here I'm setting ctrl+g to work as prefix on the second level of tmux, and ctrl+t to work on the third level.

Thanks to configuration like this, if you use ctrl+b & c to create a new window on the first level of tmux, you will use:

• ctrl+g & c - to create window on the second level
• ctrl+g & c - to create window on the first

The other setting is inside your .zshrc or .profile:

unset TMUX

If we skip this, we will end up seeing:

$ tmux new -s test
sessions should be nested with care, unset $TMUX to force

Summary

In this short guide we have seen how to set up our tmux to support nesting with minimal configuration & nice mapping for prefix key. Let me know in the comments if you are interested in more tmux or command line tips.