Ghostty

Ghostty is the terminal on Cole’s desktop, the way Termius is the terminal on the phone. It is a fast, native terminal emulator for macOS and Linux, free and open source (Free (open source, MIT license) (as of Oct 28, 2026, github.com)), and it is where tmux, every agent and every SSH session are drawn. Its config is a short plain-text file, and Cole’s is tuned so the terminal stays out of tmux’s way.

What Ghostty is

Ghostty’s own description is “fast, feature-rich, and native”: its GitHub page calls it “a fast, feature-rich, and cross-platform terminal emulator that uses platform-native UI and GPU acceleration”. It is a passion project started by Mitchell Hashimoto. On macOS its interface is written in Swift with AppKit and SwiftUI; on Linux, in Zig with GTK4. Both sit on a shared core library that does the terminal emulation, font handling and rendering. In practice that means native tabs and splits, smooth scrolling through very long output, and a terminal that feels like a Mac app on a Mac.

Install it with brew install --cask ghostty (it is in Cole’s Brewfile) or from ghostty.org. The config lives at ~/.config/ghostty/config; Cole’s is kept in the Dotfiles and linked there by the installer.

Cole’s config, line by line

Alt for tmux

macos-option-as-alt = left

The most important line. On a Mac, the Option key normally types special characters (Option-h is ˙), so terminal programs never see an Alt key, and the Alt bindings in Cole’s tmux keymap (Alt-h, Alt-l, Alt-a, Alt-s) would never fire. This makes the left Option key act as Alt, and leaves the right one for typing accented letters, so normal macOS text entry still works.

Scrolling and selecting

mouse-scroll-multiplier = 0.3
selection-word-chars = "-_./:@~?&=%+#"

The first line slows scrolling with a notched mouse wheel, from Ghostty’s default of 3 down to 0.3.

The second is a lesson in reading an option’s definition. Its comment in Cole’s config says the goal is for a double-click to grab a whole feat/my-branch-name, file path or URL. But Ghostty’s reference defines this option as the characters where a selection stops: “similar to the WORDCHARS environment variable in zsh, except this specifies the boundary characters rather than the word characters”. So this value turns -, / and . into stop points, the opposite of the intent, and drops the space from the boundaries. Ghostty’s default boundaries (space, tab, quotes, brackets, |, :, ;, , and $) already keep paths and branch names whole. To have a double-click grab a whole URL as well, take the colon out of the default set:

selection-word-chars = " \t'\"│`|;,()[]{}<>$"

New tabs and splits stay where you are

window-inherit-working-directory = true
tab-inherit-working-directory = true
split-inherit-working-directory = true
split-preserve-zoom = navigation

New windows, tabs and splits open in the directory you were in, the “continue where I was” model, instead of the home folder. And a zoomed split stays zoomed when you move focus to another split, rather than silently un-zooming.

Notifications for long commands

notify-on-command-finish = unfocused
notify-on-command-finish-action = bell,notify
notify-on-command-finish-after = 30s

When a command that ran for more than 30 seconds finishes in a window you are not looking at, Ghostty rings the bell and posts a macOS notification. Ghostty’s own default is five seconds; 30 keeps quick commands from producing noise. Long test runs, builds and installs announce themselves.

SSH that renders properly

shell-integration-features = ssh-env,ssh-terminfo

Ghostty identifies itself as xterm-ghostty, and a server that has never heard of that terminal shows errors like “missing or unsuitable terminal: xterm-ghostty”, with broken backspace, arrow keys and colors. These two shell integration features fix it automatically: Ghostty installs its terminal description on the remote machine the first time you connect (with infocmp and tic), and falls back to a widely known terminal type when it cannot. Cole’s bootstrap script also installs that description locally on every Mac, since macOS does not ship one.

Keys

keybind = cmd+shift+m=toggle_mouse_reporting
keybind = cmd+opt+w=close_tab:right
keybind = ctrl+slash=text:\x1f

• Cmd+Shift+m toggles mouse reporting. Full-screen programs like lazygit or btop capture the mouse, which blocks selecting text with it; one tap gives the mouse back to the terminal, another returns it.
• Cmd+Opt+w closes every tab to the right of the current one, the way browsers do.
• Ctrl+/ sends the single byte 0x1f. Ghostty’s modern keyboard protocol encodes Ctrl-/ as an escape sequence that fzf does not understand, so the bytes leaked into fzf’s search box. 0x1f is the byte Ctrl-_ sent on old serial terminals, and fzf has always read it as ctrl-/.

How it fits with tmux and the shell

Ghostty and tmux both want to own parts of the terminal, so a few settings on the tmux side meet it halfway:

• True color. Cole’s tmux.conf tells tmux that xterm-ghostty accepts 24-bit RGB color.
• Keys. tmux runs with extended keys in the CSI u format, so Ghostty’s encodings for Alt and Ctrl combinations reach programs inside tmux instead of leaking in as escape characters.
• The right TERM. A tmux hook copies the attaching client’s terminal type into the server’s environment on every attach, so a tmux server first started over a plain SSH session still gives new windows Ghostty’s full terminal type later.
• Shell integration, guaranteed. Ghostty normally injects its zsh integration on its own. When zsh starts in a way that skips that, the integration’s ssh wrapper never loads, so Cole’s zshrc sources it explicitly. Cole’s own ssh wrapper, which cleans up terminal modes after a dropped connection, then chains to Ghostty’s (see SSH).
• Tab titles. tmux sets the tab title to the machine’s short label plus the current window name, so a Ghostty tab attached to a server says which server.

Ghostty and Termius

Ghostty runs on macOS and Linux, on the desk. On the phone, Termius plays the same role, and the tmux config is written so both feel alike, down to the scroll direction. Over Tailscale, either one reaches any machine by name.

Gotchas

• Option is not Alt by default. Without macos-option-as-alt, Alt-key bindings in tmux and other programs do nothing on a Mac.
• Remote servers need the terminfo entry. Turn on ssh-terminfo, or copy it once by hand with infocmp -x xterm-ghostty | ssh YOUR-SERVER -- tic -x -, as Ghostty’s docs show.
• Programs that grab the mouse. If you cannot select text, the program has taken the mouse; Cmd+Shift+m takes it back.
• Check what a value means. Option names can mislead, as selection-word-chars shows. The reference says, for each option, exactly what its value controls and what the default is.

The full option list is in the Ghostty config reference, and the tmux page covers the multiplexer that runs inside it.