tmux Setup

Pi works inside tmux, but tmux strips modifier information from certain keys by default. Without configuration, Shift+Enter and Ctrl+Enter are usually indistinguishable from plain Enter.

Add to ~/.tmux.conf:

set -g extended-keys on
set -g extended-keys-format csi-u

Then restart tmux fully:

tmux kill-server
tmux

Pi requests extended key reporting automatically when Kitty keyboard protocol is not available. With extended-keys-format csi-u, tmux forwards modified keys in CSI-u format, which is the most reliable configuration. The extended-keys-format option requires tmux 3.5 or later.

With only:

set -g extended-keys on

tmux defaults to extended-keys-format xterm. When an application requests extended key reporting, modified keys are forwarded in xterm modifyOtherKeys format such as:

• Ctrl+C → \x1b[27;5;99~
• Ctrl+D → \x1b[27;5;100~
• Ctrl+Enter → \x1b[27;5;13~

With extended-keys-format csi-u, the same keys are forwarded as:

• Ctrl+C → \x1b[99;5u
• Ctrl+D → \x1b[100;5u
• Ctrl+Enter → \x1b[13;5u

Pi supports both formats, but csi-u is the recommended tmux setup.

Without tmux extended keys, modified Enter keys collapse to legacy sequences:

This affects the default keybindings (Enter to submit, Shift+Enter for newline) and any custom keybindings using modified Enter.

• tmux 3.5 or later for extended-keys-format csi-u (run tmux -V to check)
• A terminal emulator that supports extended keys (Ghostty, Kitty, iTerm2, WezTerm, Windows Terminal)

With tmux 3.2 through 3.4, omit extended-keys-format csi-u; Pi still supports tmux's default xterm modifyOtherKeys format.