Harness — Claude Code MCP server: what it does, how to install
An MCP server for the Harness environment. It allows coding agents to start Claude Code or Codex runs across connected machines, wait for completion, and read results.
claude mcp add harness -- npx -y @autonomous-ai/harness-mcpWhat Harness does
The server connects Claude Code and other clients to the Harness workspace. Through MCP, an agent can start external runs of Codex or Claude Code. It waits for progress and reads final outputs. You can orchestrate tasks across several computers.
Execution happens under the Harness daemon. Every session runs inside its own tmux pane. Terminal text moves directly between machines using WebRTC and ChaCha20-Poly1305 encryption. Relays only handle encrypted ciphertext without storing keys.
Launching @autonomous-ai/harness-mcp requires npx. The server cannot interact with agents unless the Harness daemon is configured on the target hosts.
What it helps with
- run Claude Code and Codex sessions on remote servers
- monitor task execution status across Harness sessions
- collect answers and terminal output from running agents
- manage agent workflows inside isolated tmux panes
Example prompts for the agent
- Start a Claude Code task on the remote machine through Harness and wait for the result.
- Check the status of the Codex session in Harness and read its terminal output.
How to install Harness
Platform CLI
claude mcp add harness -- npx -y @autonomous-ai/harness-mcpPlatform CLI
codex mcp add harness -- npx -y @autonomous-ai/harness-mcpConfig file
{
"mcpServers": {
"harness": {
"command": "npx",
"args": [
"-y",
"@autonomous-ai/harness-mcp"
]
}
}
}Config file
{
"servers": {
"harness": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"@autonomous-ai/harness-mcp"
]
}
}
}Platform CLI
gemini mcp add harness npx -y @autonomous-ai/harness-mcpStep by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about Harness
How do I install Harness in Claude Code?
Run claude mcp add harness -- npx -y @autonomous-ai/harness-mcp in your terminal. This requires Node.js with npx installed on your machine.
What does the Harness MCP server do?
It allows coding agents to launch Claude Code and Codex sessions on linked machines. The calling model can wait for those runs and read their responses.
How does Harness secure remote communication?
Connections use direct WebRTC channels with ChaCha20-Poly1305 encryption and X25519 session keys. The fallback relay only forwards encrypted ciphertext without having decryption keys.
