Show HN: Boo – Screen-style terminal multiplexer built on libghostty

A GNU screen style terminal multiplexer built on libghostty (libghostty-vt), written in Zig.

Every session's output is parsed through Ghostty's terminal emulation core, so boo always knows the exact screen state of every session: contents, styles, cursor, scrollback, and terminal modes. That state is used to rehydrate your terminal on attach, to answer terminal queries for detached sessions, and to let scripts and AI agents read the screen exactly as a human would see it.

• Sessions that survive disconnects: detach with Ctrl-A d, reattach with boo attach.
• A full-screen session manager: boo ui lists sessions in a sidebar.
• Faithful redraws from libghostty terminal state, including SGR styles, cursor position, scrolling regions, window title, and terminal modes.
• Agent-friendly automation primitives: send, peek, wait, and --json output, all usable without a TTY.

For Linux and macOS:

curl -fsSL https://raw.githubusercontent.com/coder/boo/main/install.sh | sh

Pre-built binaries are published on the releases page. Set BOO_VERSION to pin a release and BOO_INSTALL_DIR to change the install location (default: /usr/local/bin when writable, otherwise ~/.local/bin).

boo new                    # new session running $SHELL, attached
boo new work               # named session
boo new work -d -- make    # create detached, running a command
boo ui                     # manage sessions in a full-screen UI (alias: i)
boo ls                     # list sessions
boo attach work            # reattach (alias: at, a)
boo rename work api        # rename a session
boo kill work              # end a session
boo kill --all             # end every session

With no name, boo new names the session after the current directory, falling back to the process id when that name is taken or unusable.

Run boo help for the full overview, boo help <command> for flags and examples, and boo help --all to print every help page at once.

Bindings follow GNU screen's defaults, including the C-x variants (C-a C-d detaches just like C-a d).

boo ui adds additional keybinds for switching, resizing, creating sessions, and killing them.

Everything except attach works without a terminal, which makes boo a natural sandbox for scripts and AI agents driving interactive programs. The canonical loop:

boo new build -d -- bash               # 1. headless session
boo send build --text 'make' --enter   # 2. type into it
boo wait build --idle                  # 3. let output settle
boo peek build --scrollback            # 4. read the screen
boo kill build                         # 5. clean up

• Reading state: peek prints the rendered screen reconstructed from terminal state, not a raw byte log: ordered, fully redrawn, and stable. --scrollback includes history; --json adds size, cursor, and title.
• Waiting: wait --text <text> blocks until the screen contains the text; wait --idle until output has been quiet for 2 seconds; --timeout <dur> exits 4 instead of hanging forever (durations: 500ms, 2s, 1m, 4h, 1d). No more sleep-and-poll loops.
• Sending input: send --text is literal: no escape processing, no implicit newline, no quoting layer to fight. --enter submits, --key Enter,C-c,Up names control keys, and stdin mode is binary safe.
• Machine-readable output: ls --json and peek --json.
• Exit codes: 0 success, 1 error, 2 usage error, 3 no such session, 4 wait timed out.

See boo help automation for the full page.

GNU screen works the same way boo does, architecturally: it parses all output through its own built-in terminal emulator and redraws from that state on reattach. But that emulator is decades old and lags far behind what modern programs emit. Whatever it doesn't understand gets dropped or mangled on redraw. boo swaps that layer for libghostty-vt, Ghostty's VT core, so the saved state matches what your terminal would actually display, and terminal queries are answered while detached so TUIs don't hang unattended.

Scripting is the other win: send, peek --json, and wait --text/--idle instead of -X stuff, hardcopy files, and sleep loops.

tmux is great, it just solves a different problem. boo keeps screen's model by design: sessions, a prefix key, and nothing else to learn. One session per task, with boo ui to juggle them.

Requires Zig 0.15.2.

zig build                       # binary in zig-out/bin/boo
zig build test                  # unit tests
zig build test-integration     # end-to-end tests on a real PTY
zig build test-all             # everything

The libghostty dependency is fetched and built from source automatically (pinned in build.zig.zon).

With Nix, nix develop opens a shell with the right Zig version, and nix build builds the package to ./result/bin/boo.

your terminal <-(raw tty)-> boo client <-(unix socket)-> session daemon
                                                         `- PTY + ghostty-vt Terminal

• The client puts your TTY in raw mode and shuttles bytes over a framed Unix-socket protocol (src/protocol.zig).
• The daemon (forked on session creation) owns the session's command: a PTY-attached child whose output feeds a persistent ghostty-vt TerminalStream (src/window.zig).
• While attached, output is passed through to your terminal byte for byte. On attach the daemon sanitizes your terminal and replays the screen from libghostty state using its VT TerminalFormatter.
• Terminal queries (DSR, DA, XTWINOPS, ...) while detached are answered by libghostty's stream handler; while attached your real terminal answers, avoiding double replies.

This is a young project, not a drop-in GNU screen replacement:

• One attached client per session (attaching steals); no -x sharing.
• One window per session: no splits or tabs inside a session. Run one session per task and juggle them with boo ui.
• The C-a prefix is not yet configurable, and pasted bytes containing 0x01 are interpreted as the prefix (GNU screen has the same quirk; boo ui is immune thanks to bracketed paste).
• Sessions run with TERM=xterm-256color.

Feel free to open an issue if you have questions, run into bugs, or have a feature request.

MIT. Ghostty itself is MIT licensed.