Harnss

Harnss is currently pending a large rewrite to improve usability, performance and overall codebase into a more production ready app. I will share more info about it soon.

Harnss is in early development and issues are to be expected. Please feel free to report bugs and issues in the Issues section.

  Harness your AI coding agents.

Harnss is a cross-platform desktop app that gives you one interface to run, manage, and switch between AI coding agents — Claude Code, Codex, and any ACP-compatible agent — without losing context, sessions, or tool state.

Why Harnss?

- One app, every agent. Run Claude Code, Codex, and custom ACP agents side by side. No more juggling terminals or losing context when switching tools.
- See what your AI is actually doing. Tool calls render as interactive cards with word-level diffs, syntax highlighting, and inline bash output — not raw JSON.
- Your workspace, your way. Built-in terminal, browser, git, MCP servers, and file panels — all scoped per project, all staying open while you work.

Screenshots

  Terminal, browser, git, and MCP integrations — all in one window.

  One UI - all agents. Browse entire ACP registry.

Click to reveal other screenshots

https://github.com/user-attachments/assets/41f5bcbc-c141-4a16-b430-79f8e01d107e

  Organize your projects in spaces.

  Every tool call beautifully visualised - even those from popular MCPs.

  Run multiple agent sessions side by side — switch instantly without losing progress.

Features

Multi-engine sessions

Run Claude Code (via the Anthropic SDK), Codex, and ACP-compatible agents in parallel. Each session has its own state, history, and context. Switch between them instantly.

Rich tool visualization

Every tool call renders as an interactive card. File edits show word-level diffs with…