How do I install Harness?

Copy the stdio config for Cursor, Claude Desktop, Claude Code, or VS Code on this page. It uses the publisher's install, not a PlugMCP proxy.

Does Harness need an API key?

No required environment variable is listed on this record.

What transport does Harness use?

Harness runs locally over stdio.

When was Harness last checked?

Last checked 2026-11-09. Start Claude Code and Codex agents the person can watch, wait for them and read their answers.

Harness MCP server

Power your agent

Add this server

The publisher's own command. Not a PlugMCP endpoint.

Add to Cursor Add to VS Code Run on PlugMCP

Host a copy with our keys and logs.

Local command

npx -y @autonomous-ai/[email protected]

Claude Code has no install link for a local command. Copy the command below and run it in a terminal.

shClaude Code

1claude mcp add ai.autonomous.harness-harness -- npx -y @autonomous-ai/harness-mcp@0.2.0

Run in a terminal.

jsonClaude Desktop

1{2  "mcpServers": {3    "ai.autonomous.harness-harness": {4      "command": "npx",5      "args": [6        "-y",7        "@autonomous-ai/[email protected]"8      ]9    }10  }11}

claude_desktop_config.json

Local · npmPublisher installStep-by-step: add this in Claude

Remote URL or a command on your machine? How the two installs differ

Run on PlugMCP

Host a copy with our keys and logs.

A new server you create. It is not this listing's official endpoint. Use the publisher install when you want their URL and their credentials.

Launch

Server facts

Local

Transport: stdio
Version: 0.4.20
License

Tools

No tool list yet. Remote servers get one after the first health check.

FAQ

Questions

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 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

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. 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. Build a filter. Change one resistor. Overlay the new trace, measure the difference and keep both.

Beyond code: Robotics

MuJoCo. Pin a moment in a robot's run. Shove it with 100 N. Watch two futures split.

Beyond code: Games

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. 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. Turn a bond and watch the molecule move. Follow the real energy curve. Keep the pose worth a closer look.

Beyond code: Documents

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

Category	Agents and harnesses
Coding	Claude Code, Codex, Cursor, OpenCode, Pi, Hermes, Command Code, Devin, Muse Code, Amp, Antigravity, GitHub Copilot, Grok Build, Kilo Code, Machine Monitor, Trail of Bits Skills
Essentials	Harness Monitor, Memories
Design	Autonomous Workshop, Blender, Bonsai MCP, Creative Direction, Excalidraw, FreeCAD, Generative Art, OpenSCAD, text-to-cad
Engineering	Autonomous Circuit, CircuitJS, Home Assistant, KiCad, ,

Upstream open-source tools and original workflows. 10 shared viewers install alongside the harnesses that need them. Unlisted experiments are not shown.

Build your own

The next harness is the one for your craft. Wrap a tool you love or your team's toolchain. It can live here or in your own repo. From this repo:

{
  "spec": 1,
  "id": "examples/hello-world",
  "name": "Hello World",
  "engine": "codex",
  "workspace": { "template": "template", "marker": "index.html" },
  "agent": { "instructions": "AGENTS.md" },
  "viewer": { "use": "autonomous/web-viewer" }
}

harness dsh install "$PWD/store/viewers/web-viewer" --link
cp -R store/examples/hello-world ../my-harness
harness dsh check ../my-harness
harness dsh install ../my-harness --link

Press ⌘N → Hello World and say hello. The authoring guide covers the rest.

Harness device

Get a Harness device, or build your own from the files below. The firmware guide lists the supported boards and build commands, and the hardware guide covers the design files. The optional Harness device is a round, always-on display that sits beside your keyboard and shows your agents at a glance: what each one is doing, which one has finished, and which one is waiting on you. Read a question and answer it on the screen, or tap and speak a new task, without switching windows.

It is open hardware, all the way down. This repository has everything it takes to build one:

Layer	What's here
Firmware	ESP32-S3, ESP-IDF, a 466 × 466 round AMOLED with touch, microphones and audio. Connects to the host's daemon over USB — no Wi-Fi setup, no account on the device.
PCB	The EasyEDA Pro project, the schematic, Gerbers, the bill of materials, and pick-and-place data for assembly.
Enclosure	STEP for editing and STL for printing: the housing, an iron counterweight base, the USB clamp, and the button.

Contribute

Make a harness for a tool you love. Improve terminals, engines, the daemon or the relay. Port the firmware. Start with the contribution guide.

Architecture · Product direction (proposal) · Development · Extending · CLI · Security · MIT license; upstream tools keep their own.

Add this server

Host a copy with our keys and logs.

Server facts

Tools

Questions

How do I install Harness?

Does Harness need an API key?

What transport does Harness use?

When was Harness last checked?

Documentation

Every machine, side by side

Keyboard first

End-to-end encrypted

Fast and light

Built the way developers work

How it works

Get started

Beyond code: Build across disciplines

Beyond code: Design

Beyond code: Circuits

Beyond code: Robotics

Beyond code: Games

Beyond code: Music

Beyond code: Chemistry

Beyond code: Documents

Domain-specific harnesses (DSH)

49 harnesses in the Store

Build your own

Harness device

Contribute