Harness

Harness like a boss.

The ultimate harness for coding agents and beyond.

Claude Code at work. Codex at home. Hermes in the cloud. One command center.

Start with code. Then follow your curiosity and build across disciplines: CAD, circuits, robots, games and music.

Download · How it works · Beyond code · Harnesses · Device

Every agent, side by side

Claude Code, Codex, Cursor, OpenCode, Devin, Amp, Copilot and seven more.

Every machine, side by side

Your laptop, home server and GPU box in one window. Link each one with a password. No SSH keys. No Tailscale. No port forwarding.

Keyboard first

⌘P finds any harness on any machine. ⇧⌘I jumps to the harness waiting on you. ⌘D splits. Every key remaps.

End-to-end encrypted

Code, keys and keystrokes are sealed on your machine. The relay forwards bytes it can't read.

Fast and light

A native app, not Electron. Close it and your agents keep working.

Idle measurements on an M2 Max:

• ⌘N, ⌘O, ⌘T UI: 11–13 ms median, 15–18 ms p95.
• Local terminal echo: 1.1 ms median, 7.2 ms p95, excluding UI rendering.
• Desktop resources: ~0.1% of one CPU core and 304 MiB, including terminal rendering and scrollback; agent CLIs and the daemon are excluded.

Desktop results use a Release fixture with 16 terminals and 1,000 scrollback lines each. See the workflow and resource benchmarks and remote P2P, TURN and relay results for workloads, slow tails, connection failures and raw data.

Built the way developers work

• Real terminals. Every agent runs in its own tmux pane. Scrollback, colors and keys just work.
• Your CLIs, as they are. Harness never wraps an agent. It reads transcripts and uses the vendor's own hooks.
• A worktree per harness. Start an agent on its own branch. Your working copy stays clean.
• Remap every key. One JSONC file, reloaded on save. Chords up to four strokes.
• Local models. Run open-weight models on your own machines with Grid, Ollama, MLX-LM and vLLM.
• Bytes, not pixels. Remote terminals stream text peer to peer. No remote desktop.
• Open source, all of it. App, CLI, daemon, relay and device, in this repo.

How it works

In the workspace, a harness is one running session of an agent such as Codex or Claude Code, with its own conversation and working context. A tab groups harnesses. Use New Harness to start one and New Tab to group work. Harnesses in the same tab can message each other with harness send: Agent Messages, an experiment of your account, off by default and turned on in Settings ▸ Experimental.

The Store offers harnesses with instructions, tools, and optional viewers for specific crafts. Install a harness, then start it in your workspace. See the Naming System for the complete naming rules.

One daemon per machine runs your agents in tmux. It dials out, so no machine opens a port.

flowchart LR

subgraph laptop["Your laptop"] app["Harness app"] -- loopback --> d1["daemon"] d1 --> a1["tmux · Claude Code · Codex"] end subgraph box["Your GPU box"] d2["daemon"] --> a2["tmux · OpenCode · Hermes"] end device["Harness device"] -- USB --> d1 d1 <-. "direct WebRTC" .-> d2 d1 <-- "ciphertext" --> relay["Harness relay · no keys"] relay <-- "ciphertext" --> d2

Every path is sealed end to end: ChaCha20-Poly1305, X25519 session keys, pinned Ed25519 identities. Harness picks the best path on its own.

Direct. A WebRTC channel between your machines. No server in the path.

Through Cloudflare. When a firewall blocks the direct path, the same encrypted channel runs over Cloudflare's TURN network. Harness keeps trying for a direct path.

Through our relay. A fallback while WebRTC negotiates. The relay holds no keys and forwards ciphertext.

The architecture guide has the details.

Get started

[Download the app](https://harness.autonomous.ai/desktop?utm_source=github&utm_medium=readme) for macOS or Linux.

Add a machine. Run this on it, then Machines → Link Machine in the app:

curl -fsSL https://harness.autonomous.ai/cli/install.sh | bash

harness login harness remote-password set harness start

In a terminal: the same line installs hn — tmux's keys and your ~/.tmux.conf, with every harness on every machine (hn). The first time, hn signs in and connects the computer:

curl -fsSL https://harness.autonomous.ai/cli/install.sh | bash

hn

For agents: Claude Code and Codex can start, wait for and read other harnesses with the harness skill (harness.autonomous.ai/agents, which has the Codex lines too):

claude plugin marketplace add autonomous-ai/openharness --sparse .claude-plugin plugins

claude plugin install harness@openharness

Build from source

Needs Node.js 20+, tmux, Xcode and Flutter 3.47+ / Dart 3.13+:

git clone https://github.com/autonomous-ai/openharness.git

cd openharness (cd cli && npm ci) make install-cli cd desktop flutter config --enable-swift-package-manager flutter pub get flutter run -d macos

make install-cli installs this checkout's CLI and restarts the local daemon. See the development guide.

Beyond code: Build across disciplines

“World-class entrepreneurs are polymaths.” — Peter Thiel

Coding agents can build far more than software. Give one a harness and it works with the real tools of a craft. You steer in a live viewer. Every clip below is a real session.

Beyond code: Design

[Blender](store/agents/blender/). Ask for a lamp and the sliders that matter. Turn them and Blender rebuilds the geometry. Keep the versions you love.

Beyond code: Circuits

[CircuitJS](store/agents/circuitjs/). Build a filter. Change one resistor. Overlay the new trace, measure the difference and keep both.

Beyond code: Robotics

[MuJoCo](store/agents/mujoco/). Pin a moment in a robot's run. Shove it with 100 N. Watch two futures split.

Beyond code: Games

[Godogen](store/agents/godogen/). Your agent makes a playable game. Miss a jump, rewind, try again. Pin the moment so the agent sees what you mean.

Beyond code: Music

[Strudel](store/agents/strudel/). The track is code you can perform. Bring voices in and out, mark the good parts, keep the WAV. Hear it.

Beyond code: Chemistry

[RDKit](store/agents/rdkit/). Turn a bond and watch the molecule move. Follow the real energy curve. Keep the pose worth a closer look.

Beyond code: Documents

[Typst](store/agents/typst/). Your agent writes a real PDF. Circle a detail, quote a line, leave a note. The next draft answers it.

Domain-specific harnesses (DSH)

Code is the common medium. Geometry scripts make parts. Netlists make boards. Animation code makes film.

A domain-specific harness turns a coding agent into a specialist. It brings the craft's instructions and skills, a pinned toolchain, a project template, checks and a live viewer. You chat on one side. The board, the part or the game takes shape on the other.

The agent does the reasoning. The harness supplies the tools and the view. It's a folder with a harness.json, so adding a craft never touches the app.

49 harnesses in the Store

| Engineering | Autonomous Circuit, CircuitJS