Set tmux escape-time to 0

By default, tmux uses a 500 millisecond escape-time, which causes problems with multi-function keyboard keys1. Set it to 0 instead:

set  -s escape-time 0

  1. For example, I have my <caps lock> key mapped to <ctrl> on hold, and <escape> on tap. With tmux’s default escape time, tapping it without waiting for half a second before the next key press results in a <ctrl> being sent instead of an <escape>.