Built like instrumentation, not like an app

The complete path a keystroke takes. Eight parts, one loop, no intermediaries.

1. key event
2. input_poll() · input.c
3. pty_write() · pty_dispatch.c
4. shell
5. pty_read() · pty_unix.c
6. screen_feed() · screen.c
7. renderer_draw() · render.c
8. glyphs

That is the entire loop. No compositor in the middle, no JavaScript bridge, no IPC hop to a helper process. Each tab owns a recursive split tree — leaves carry a Pane (PTY, screen buffer, selection, title and cwd), internal nodes carry a split mode and a ratio — and the main loop drains every leaf's PTY each frame. The 0.018 ms is what is left when there is nothing else to remove. The full API is on the scripting sheet.

Bill of materials. Every figure below is measured on shipping builds, not estimated.

Four modules that do work the terminal underneath you usually leaves to a wrapper script.

RB-01 · Agents

A terminal that reports on the agents running inside it

Every tab carries a status badge derived from what the pane is actually doing: a spinner while a command runs, a green dot when it finished clean, a red dot when it failed, an amber ! when the agent is waiting on you. Claude Code rings the bell; rbterm turns that into a badge you can read across fifteen tabs without focusing one.

• rbterm @ — kitty-style remote control: ls, send-text, send-key, get-text, screenshot, split, focus-tab, set-colors, record-start / record-stop.
• Boolean match engine — state:done or state:failed, plus id, title, cwd, pid and user vars.
• display-image — an agent pops the chart or screenshot it just made as a click-to-dismiss overlay in its own pane. $RBTERM_PANE_ID survives a restart.
• Zero config with Claude Code — preferredNotifChannel: terminal_bell, with hooks preset for explicit statuses. Wiring it up →

# show what an agent just produced, in its own pane
rbterm @ display-image --path shot.png

# one wait-loop babysits N agents
rbterm @ match-count -m '(state:done or state:failed)'

# unblock a specific pane by id
rbterm @ send-text -m id:3 'git rebase --continue\n'

# every pane's status, as data
rbterm @ ls | jq -r '.data.windows[].tabs[].panes[].status'

RB-02 · SSH

libssh, not a wrapper

SSH is a first-class backend inside the terminal, so the UI never blocks on a handshake and every pane keeps its own session.

• Async connect — startup tabs, splits and saved layouts dial on worker threads, in parallel
• Key, agent, password and keyboard-interactive auth · trust-on-first-use host keys · ProxyJump
• Local -L, remote -R and dynamic -D SOCKS5 forwards, up to 16 per host
• Per-host fonts, themes, cursor colour, HUD and split layouts, stored as comments in ~/.ssh/config
• SFTP upload and download on every SSH tab, recursive, over the same session
• Key manager — generate Ed25519 or RSA, install to authorized_keys, all from the GUI

RB-03 · Panes & recording

Splits that record themselves

A recursive split tree per tab, and a recorder that writes finished files without asking you to install anything.

• Split, subdivide, cycle and maximize any pane · broadcast input to every pane at once
• Search across a million lines of scrollback with Cmd+F
• Record straight to gif, webp, mp4, webm, apng or asciinema cast
• Native gif, webp and apng encoders on every platform — no ffmpeg on the path required
• Recording a split captures every leaf — one file per pane
• Quake hotkey (Cmd+CapsLock) · multi-window · per-tab fonts · raw session logging

RB-04 · Graphics

Pixels, where pixels belong

Both inline image protocols, with real pixel geometry reported to the child process so apps stop falling back to ASCII.

• Sixel and kitty graphics protocols, decoded in-process
• Colour emoji via Core Text · HarfBuzz ligature shaping
• OSC 8 hyperlinks · OSC 133 prompt marks with an exit-status gutter
• Hand-rasterized box-drawing glyphs — no gaps in tmux, htop or btop borders

Every other module — the VT parser, intelligent reflow, the settings panel, desktop notifications, the logs browser — is drawn out part by part on the features sheet. Full feature catalogue

Echo round-trip in milliseconds, median of 1000 samples, same machine, August 2026. Logarithmic scale — the field spans three decades. Lower is better.

Method. tools/echo_bench.c writes an ANSI DSR query (CSI 6n), waits for the terminal's CSI r;c R reply and records the round-trip — parser plus PTY I/O, nothing else. 1000 samples per terminal, same machine, same session. Reproduce it in any terminal with ./tools/bench-here.sh from the repo. Tail figures: rbterm p99 0.045 ms. On bulk output the same build ingests a real full-screen animation stream at 185 MB/s, ahead of every terminal tested. The full comparison is on the comparison sheet.

Nineteen hand-tuned film- and hardware-inspired looks — CRT scanlines, phosphor decay, VHS tracking, halftone, bloom and glitch — applied live per pane and captured straight from the effect shader. Six of them below.

Pick one per tab in Settings → Effects, or pin one to an SSH host so you always know which machine you are on. All 19 effects

The ten chords worth learning first. Everything else is in the manual.

• Cmd+TNew tab — local shell
• Cmd+Shift+TNew tab over SSH, with saved hosts from ~/.ssh/config
• Cmd+D / Cmd+Shift+DSplit the pane vertically / horizontally — recursive
• Cmd+KCycle focus through the split panes
• Cmd+ZMaximize the active pane, and back again
• Cmd+FSearch the scrollback
• Cmd+Shift+IBroadcast every keystroke to all panes in the tab
• Cmd+Shift+SScreenshot the active pane to PNG
• Cmd+,Settings — font, theme, cursor, logging, HUD, launch tabs
• Cmd+CapsLockSummon or dismiss the window system-wide (macOS)

Cmd on macOS; Ctrl on Linux and Windows. Read the manual

Three artifacts, one revision. Checksums and the Gatekeeper verification walkthrough are on the download sheet.