tmux-underkeys

tmux-underkeys is a plugin for tmux, the terminal multiplexer that lets you run multiple terminal sessions inside a single window. The plugin solves a small but recurring friction point: switching between named sessions without having to open a session list or remember which number or position each session occupies.

The approach is visual and mnemonic. The plugin picks one unique character from each session name and underlines it in the tmux status bar. To switch to any session, you press a trigger key (Control-g by default) followed by that underlined character. Because the characters are always visible in the status bar and derived directly from the session names, you do not need to memorize anything separately from what you can already see on screen.

Key assignment is stable as long as session names do not change. Sessions are processed by creation time, so adding a new session gives it its own character without shifting the keys already assigned to existing sessions. For each session, the plugin picks the first alphanumeric character in the name that has not already been claimed. So if you have sessions named "app" and "api", the first gets "a" and the second gets "p".

Installation uses TPM, the standard tmux plugin manager: add one line to your tmux configuration file and press the TPM install key combination. The trigger key, display position, character style, sort order, and separator between session labels are all configurable through tmux options. The status bar segment can also be turned off if you want to position it yourself in a custom status line layout.