Harness

The native macOS terminal that keeps your sessions running and tells you the moment a coding agent needs you.

Terminal panes render on Harness's own GPU engine. A stable session host owns shells and PTYs, while a replaceable daemon manages workspaces and application services. Sessions survive quitting the app when persistence is enabled, and compatible daemon replacement keeps their programs and terminal streams running. You can drive or attach to them from the command line, including a headless or remote daemon over SSH. And Harness watches the agents you run inside it (Claude Code, Codex, Cursor, and more), with optional hooks and program reports to surface requests for attention behind other tabs.

One self-contained app. The terminal engine, daemon, and CLI are first-party Swift. Sparkle is linked only by the GUI. The official Swift MCP SDK and its pinned support libraries are isolated to the CLI’s MCP integration; Swift TOML supports format-aware configuration edits. Lua 5.1 is vendored and linked by the CLI alone. The daemon does not link Lua or MCP. See architecture and provenance for dependency boundaries.

Source and downloads

This README describes the current main source. Versioned changes and downloads
are listed in the changelog and GitHub Releases.

Download

Harness 2.2 adds durable session ownership, agent history and the Overview Board,
encrypted macOS history, development workflows, and a unified Graphite interface.
The full changes are documented in the changelog.
See the release-readiness review and
performance results for measured results and remaining acceptance work.

Download Harness for macOS →

Open the DMG, drag Harness.app to Applications, and launch it normally. The release is signed, notarized, and built for Apple silicon Macs running macOS 15 or later.

Verify the SHA-256 checksum against the value published on the GitHub release page.

Prefer to build it yourself? Jump to Build from source.

Why Harness

• It's a real terminal first. GPU rendering, accurate sRGB color by default, opt-in converted Display-P3 vivid color, ligatures, native color emoji, inline images (Sixel / Kitty / iTerm2), and 514 bundled themes, including 25 original Harness palettes and black and light defaults. Block and box-drawing glyphs are drawn procedurally, so borders tile without seams at any font.
• Your work outlives the window. A stable session host owns shells and their PTYs while a replaceable daemon manages application services. Quit and reopen to attach to preserved programs. Compatible daemon replacement retains their process identities and terminal streams; host failure and reboot require restoration, not live-process survival. See survival and update behavior. Attach the same session from a second window or another machine.
• It's scriptable, locally or remotely. harness-cli drives the whole thing — open tabs, send keys, capture a pane, resize, swap, zoom — so your tooling can build the layout it needs. Point any command at a headless or remote daemon with --host <name>; the daemon and CLI run on Linux too, so a remote box can host your sessions.
• It watches your agents. Harness detects Claude Code, Codex, Cursor, and others by their process tree, shows which session is running what, and pings you when an agent stops or asks for approval. Cmd+Shift+U jumps you to the one that's waiting and skips the ones still thinking.

How it feels

Harness ranges from a plain, get-out-of-your-way terminal to a full session manager. Pick the level in Settings → Terminal → Experience:

• Plain Terminal — fast and quiet. No command prefix, no status bar. The preset turns off global persistence; unpinned sessions close on a clean quit unless you enable Keep sessions running.
• Persistent Terminal — the same clean look, but sessions survive quitting and you can attach to them from the CLI.
• Full Terminal — everything: command prefix, status line, copy mode, paste buffers, panes, and the full harness-cli command set.
• Agent Workspace — persistent project workspaces with agent detection and notifications turned up front.

These are presets: the Keep sessions running setting and per-session pins determine actual quit behavior. See Experience modes.

New installs start in Persistent with Harness Graphite, 85% opacity, 60 pt blur, 25% window border opacity, and the bottom status strip off. Tab gaps and pane borders use 8 pt spacing. Sessions survive quitting. An existing settings file that never stored a mode stays Full, so an upgrade does not hide the prefix or the status line. Moving over from another setup? See docs/MIGRATION.md — Harness offers a reviewed import of an existing terminal config (colors, font, padding); it preserves the new-install defaults until you apply an import.

Workspace workflows

Session → Activity, Saved Setups, Recently Closed, and Search All Sessions bring ongoing work together across attached hosts. The command palette and Settings → Tools also expose these actions. See Workspace workflows for behavior, limits, and CLI examples.

Development workflows

The Overview Board combines agent attention, usage freshness and process resources across attached hosts. Durable run history, tool anchors and deterministic digests share the same activity ledger. See activity and search. Optional AI summaries use explicitly configured providers and content consent; basic digests remain available without AI.

Managed worktrees, fan-out, schedules and hook policies have local configuration and recovery flows. Preview panes and remote connectivity, recording review, importers, notifications and power, MCP, and trusted local plugins document their opt-ins and limits.

History is encrypted on macOS when signed components can access their Keychain key. If access is unavailable, capture stays in bounded memory and the app reports unavailable history. Linux uses explicitly documented owner-only plaintext storage. Linux packaging and installation lifecycle describe verified archives, atomic installation and guarded service changes. The implementation checklist records remaining acceptance work; a source build alone does not establish completed native verification.

Features

• GPU-accelerated rendering by Harness's own terminal engine — accurate sRGB output by default, opt-in converted Display-P3 vivid color, a themed translucent canvas, and program output left untouched unless you opt into theme recoloring; damage-driven redraws keep selection drags, find highlights, IME composition, and streaming output cheap, full-rate on ProMotion displays, and covered or minimized windows stop rendering entirely
• Mainstream-GPU-terminal polish: live re-wrap while resizing (with a grid-size overlay), word / line / block selection, middle-click paste, alternate-screen wheel scrolling, focus reporting, hollow unfocused cursor, minimum contrast, follow-macOS appearance with separate light and dark theme picks (Settings ▸ Appearance), bold-is-bright control, and paste protection
• Quick terminal: a Quake-style dropdown on a global hotkey (Settings ▸ Keys), sliding over whatever app is frontmost and persisting like any other session
• Terminal bell (\a): audible and/or visual feedback on the focused surface, a bell badge on background tabs, and tmux visual-bell/bell-action bridging
• Find bar (⌘F) with regular-expression and case-sensitivity toggles; matches highlight across scrollback
• Title-bar tabs level with the traffic lights, each with an app tile (>_ for a shell, the brand tile for an agent) and a live status mark (working, needs you, done, error). ⌘\ switches to sidebar mode, which lists every session by name with its tabs beneath
• A sessions popover (⌃⌘S, or the stacked-squares button): filter or create a session by typing, ✓ on the current one, New Session, Add Remote Host
• Every pane is an inset card with a header (identity, split-right / split-down; double-click to zoom), horizontal / vertical splits, and grouped sessions with shared window lists
• Workspace Overview (⌘⇧O): every tab as a live tile, the ones waiting on you first; type to filter, arrows and ↩ to jump
• Session layout persists across quits (daemon-owned, attach from the CLI or over SSH); if the daemon restarts under a pane, a quiet "Reconnecting…" chip rides the ~1-minute automatic backoff before the click-to-re-grab overlay takes over
• Persistent scrollback: a pane's history is written to disk per surface and restored when the daemon restarts — set the scrollback limit to 0 to remove the line cap. Raw output and decoded history each have a separate 512 MiB ceiling; active grids, snapshots, and rendering caches are additional memory. Wide rows may reach the decoded ceiling sooner
• Remote & headless daemon: run HarnessDaemon on a headless or remote box (Linux included) and drive it with harness-cli --host <name> over your own SSH. Add Remote Host… needs only the SSH destination: it detects the daemon socket and tests the connection, and a dropped tunnel reconnects itself
• harness-cli for automation and agent hooks: run --wait -- make test exits with the command's status, targets take names, positions, or ID fragments (--surface 2, --tab logs), and exit statuses are documented (3 = no such target, 4 = daemon unreachable)
• Color/theme diagnostics from the CLI: harness-cli color-check and harness-cli theme-preview --theme <name> print deterministic SGR pages for eyeballing fidelity in Harness itself
• Command set: send-keys, capture-pane, kill-pane, resize-pane, zoom-pane, swap-pane, rename-tab, attach, find-window, kill-server, start-server, respawn-window, refresh-client, and more
• Command prefix keymap (default Ctrl-A) with a live cheatsheet (prefix ?)
• Detection and sourced identities for 37 coding CLIs, including Claude Code, Codex, Cursor, Gemini, Copilot, Amp, Aider, OpenCode, Pi, and more. Uniform monochrome marks on transparent backgrounds replace agent color customization; see the complete identity catalog and source notices. Detection is separate from per-tool hook support; see the verified CLI commands and capability boundaries
• Agent alerts as desktop notifications and a notification bell, with a switch per event in Settings ▸ Notifications (needs you, finished, failed, bell, long command finished); Cmd+Shift+U jumps to whoever is waiting
• One-line hook install: harness-cli install-hooks <agent>
• Command palette (Cmd+K) and a native macOS Settings window (Cmd+,)
• 514 bundled color themes, including 25 original Harness palettes: Graphite as the new-install default, pure-black Harness Obsidian, blue-teal Harness Deep Sea, Harness Navy, and eight light options, plus .harnesstheme export / import for sharing — double-click (or Open With) a theme file to install it, optionally applying its colors immediately. Settings ▸ Colors ▸ Theme saves the colors on screen as a named theme or exports them; saved and imported themes list in the theme menu
• Shell integration (OSC 133), auto-injected at spawn for bash / zsh / fish: prompt marks for jump-to-prompt and a command success / failure gutter, no install step (opt out with set-option shell-integration off; manual snippets remain in docs/shell-integration/)
• Inline images that stay put across reflow and scroll into history
• Cursor-anchored Insert Path popup (⌥⌘I) with Folder/Project fuzzy search, keyboard navigation, and shell-quoted insertion; drag file-backed folders or images into a pane to insert paths
• Set Harness as the default terminal for SSH/Telnet/man-page links and .command / .tool files from Settings > Terminal
• Automatic, signed background updates (Sparkle + EdDSA)
• Program status (OSC 7501): a pane can report working, blocked, done, or error, and that mark shows on the tab, the session row, and ⌘⇧U. See docs/PROGRAM-STATUS.md
• harness-cli api for a JSON method list, schemas, and calls, plus events --follow for a live event stream
• Lua 5.1 config at ~/.config/harness/init.lua (HARNESS_CONFIG overrides the path). It runs in the CLI. The daemon does not run it
• Two pane densities (comfortable cards with headers, or compact 1-point borders), lighter translucent panes against darker chrome, and automatic contrast correction on a light canvas
• Fresh windows target 100 columns × 30 rows using the configured font and padding. Size/position memory defaults on and preserves saved sizes. An optional machine indicator defaults off in Settings → Appearance
• Several machines at once: each remote host opens in its own window next to your local ones, all live, and the sidebar groups every machine's sessions. Each attach is your SSH tunnel to that daemon

harness-cli

Harness starts or adopts the session host and compatible daemon automatically; the CLI uses their public control socket.

harness-cli list-surfaces
harness-cli new-session --workspace Default --cwd ~/Code/myproject
harness-cli new-tab --workspace Default --cwd ~/Code/myproject
harness-cli send-keys --surface "$HARNESS_SURFACE" --keys "ls -la Enter"
harness-cli notify --surface "$HARNESS_SURFACE" --title Agent --body "Needs approval"
harness-cli color-check
harness-cli theme-preview --theme "Harness Graphite"

Install it onto your PATH:

# From the app bundle:
/Applications/Harness.app/Contents/MacOS/harness-cli install

# Or from a source build:
.build/release/harness-cli install

# Then add the printed path to your shell profile:
export PATH="$HOME/Library/Application Support/Harness/bin:$PATH"

On a fresh install, Harness.app opens a one-shot first-run tour (Welcome → Overview →
Notifications → Command line → Ready; reopen it from Help ▸ Welcome to Harness). Its
Notifications step offers permission and agent-hook installation as separate optional
actions. Skipping setup never prompts later just because an agent event arrives. Its optional Command line step performs the same local installation:
it atomically installs the CLI, daemon, and session-host helper bundles, stages service
updates while sessions are live, adds a PATH block with a backup
to the shells you use (your login shell plus any shell that already has a profile), and
writes fish completions when fish is one of them. It respects ZDOTDIR and
XDG_CONFIG_HOME, preserves existing bash login profiles and dotfile symlinks, and reports
unreadable profiles without replacing them. Isolated preview builds leave system
permissions, shell profiles, agent settings, and the regular installation unchanged.
After an update, Harness shows release
highlights (suppressible via the update-banner option).

Remote & headless daemons

HarnessDaemon can run on a headless box (no GUI) or a remote machine — including
Linux — and you can drive it from any harness-cli command with a global
--host <name> flag. The transport is an SSH tunnel that forwards the remote
daemon's control socket, so it reuses your existing SSH trust with no new
credentials.

# On the remote box: run the daemon. `harness-cli socket-path` there prints its socket.
# On your machine: register the remote, then target it with --host on any command.
harness-cli remote add --name devbox --ssh me@devbox --socket "$(ssh me@devbox harness-cli socket-path)"
harness-cli remote list
harness-cli ping --host devbox
harness-cli new-session --host devbox --cwd ~/Code
harness-cli send-keys --host devbox --surface <id> --keys "ls -la Enter"
harness-cli capture-pane --host devbox --surface <id>
harness-cli remote remove --name devbox

Pass extra SSH options (port, identity file, jump host) with --ssh-arg, e.g.
--ssh-arg -p --ssh-arg 2222 --ssh-arg -i --ssh-arg ~/.ssh/devbox.

Connect an iPhone or iPad

With SSH enabled and Harness 2.1 or later installed, enter /remote in Harness’s command prompt or choose Connect Phone or iPad in the command palette. In a shell, run harness-cli pair. A compatible private native iOS companion scans the compact QR code, verifies the computer and uses SSH authentication. Device keys require approval locally on the host with harness-cli mobile-key install --stdin; remote key installation is unsupported. The code contains public metadata only.

The Mac pairing window offers discovered LAN addresses, connected Tailscale addresses, Set Up Tailscale, and Refresh. Use the same tailnet on both devices for access away from home; ordinary SSH/Remote Login permissions still apply. Custom addresses and ports use harness-cli pair --host reachable-hostname --port 22. See mobile connection and troubleshooting details.

The companion groups work by host, workspace and session, uses the shared terminal engine and Metal renderer, includes touch scrolling and terminal shortcuts, and supports up to four visible panes on iPad. Its current distribution is source/development builds; an App Store release is not included in this terminal release.

Agent hooks

HARNESS_SURFACE is set in every Harness pane, so an agent can ping the exact tab it's running in:

harness-cli install-hooks claude-code
harness-cli notify --surface "$HARNESS_SURFACE" --body "Approval required"

Per-agent setup lives in docs/agent-hooks/README.md. Agents without a hook mechanism still notify you through Harness's built-in activity detection once they're running.

Keyboard shortcuts

The command prefix (default Ctrl-A, on in the Full preset) adds the full tmux-style pane / session keymap on top — press prefix then ? for its cheatsheet.

Build from source

git clone https://github.com/robzilla1738/harness-terminal.git harness
cd harness
make release
open Harness.app

Validate a source checkout before shipping changes:

swift build
swift test                              # fast, deterministic suite
HARNESS_LIVE_DAEMON_TESTS=1 swift test  # adds the real socket / PTY / security tests
make bench

CI (on pushes to main and on pull requests) builds debug and release and runs the whole suite with the live daemon tests switched on, on macos-26 with Xcode 26.6, the same toolchain releases are built with. It also builds Harness.xcodeproj, and builds and tests the headless daemon and CLI on Linux (Swift 6.0; advisory for now). The live tests spin up a real daemon over a Unix socket and a real PTY, so run them locally before changing the daemon, IPC, or PTY code.

make bench runs opt-in release benchmarks and prints machine-readable JSON timing lines. Treat those as a structural baseline, not a pass/fail gate — GPU and timing numbers vary by machine.

Renderer tests use structural offscreen readbacks by default. Set HARNESS_WRITE_RENDER_SNAPSHOTS=1 when running swift test --filter MetalRendererTests to write PNGs under /tmp/HarnessRenderSnapshots for human debugging only.

Develop in Xcode

Harness.xcodeproj is generated from project.yml with XcodeGen. The app target builds and bundles HarnessDaemon and harness-cli into Harness.app/Contents/MacOS/, so an Xcode run uses the same helper layout as the release app.

xcodegen generate
open Harness.xcodeproj
xcodebuild -project Harness.xcodeproj -scheme Harness -configuration Debug \
  -destination 'platform=macOS,arch=arm64' build test

Requirements

• Apple silicon Mac running macOS 15.0 or later for the downloadable DMG
• Xcode 26.6 or later (to build from source; CI and releases use 26.6)
• For a headless/remote daemon: any machine with Swift 6.0 (macOS or Linux) — build the daemon + CLI with swift build -c release (the GUI app, renderer, and Sparkle are macOS-only and are dropped from the Linux build)

Documentation

• Experience modes — Plain / Persistent / Full / Agent
• Sessions & panes guide — prefix, panes, sessions, copy mode, attach from anywhere
• Capabilities and limits — what Harness supports and where the boundaries are
• Architecture and provenance — implementation, dependencies and compatibility
• tmux parity ledger — capability status, adaptations for the daemon-owned model, explicitly rejected tmux features with rationale
• tmux-style capabilities PDF — printable setup, shortcuts, commands, attach, copy mode, and troubleshooting
• Release runbook — signed/notarized DMG, GitHub Actions release workflow, and Sparkle appcast publishing
• Migration — bringing your config and habits across
• Keybindings · Commands · Program status · Shell integration · Agent hooks
• Changelog — release history
• Third-party notices

License

MIT