UPDATE: With recent releases of tmux many configuration options have changed. If you’re running tmux 2.4 or later please read this issue comment for a potential resolution.

With the release of OS X 10.11 “El Capitan” came a new Terminal.app which has different mouse behavior with tmux. This affects both copy/paste and scrolling with tmux 2.0’s mode-mouse. If you’re running tmux 2.0 and have lines like:

set -g mode-mouse on
set -g mouse-resize-pane on
set -g mouse-select-pane on
set -g mouse-select-window on

In your ~/.tmux.conf, in El Capitan you’ll probably notice you can automatically scroll without having to first enter copy-mode. In tmux 2.1, you can replace these lines with just:

set -g mouse on

However, there’s one gotcha with this which is that tmux 2.1 apparently also changes the default behavior of mouse scrolling with the new mouse support turned on, so the automatic mouse scrolling you had with tmux 2.0 in El Capitan no longer happens by default if you upgrade. If you want it back, you’ll need to add lines like this to your ~/.tmux.conf:

bind-key -t vi-copy WheelUpPane scroll-up
bind-key -t vi-copy WheelDownPane scroll-down

Additionally, if you’ve also set up system pasteboard copying in tmux with lines like what’s suggested here: 1

# Use vim keybindings in copy mode
setw -g mode-keys vi

# Setup 'v' to begin selection as in Vim
bind-key -t vi-copy v begin-selection
bind-key -t vi-copy y copy-pipe "pbcopy"

# Update default binding of `Enter` to also use copy-pipe
unbind -t vi-copy Enter
bind-key -t vi-copy Enter copy-pipe "pbcopy"

You may notice that under El Capitan you can no longer effectively select text in tmux to copy with ⌘-C because with mouse mode on it immediately jumps into copy-mode on mousedown and out of it on mouseup…never giving you a chance to pbcopy. The case here is a little tricky and the answer is not immediately apparent; what you need to do is trigger copy-pipe before releasing the mouse (with the config above, by pressing y or Enter with the mouse still pressed). In tmux 2.0 there was also a bug which would cause this to annoyingly re-enter copy-mode, but this is fixed in tmux 2.1.

One more thing: if you’re running El Capitan and tmux 2.0, you may have noticed that notifyd will occasionally start taking up 99% CPU; this should also be fixed in tmux 2.1.


  1. The reattach-to-user-namespace prefix is no longer necessary for pasteboard access within tmux