Harness Arena

Agentic Harness Arena

[](LICENSE) [](backend/requirements.txt) [](#status) [](https://discord.gg/fhGPEaDJ5T)

**An [LMSYS Chatbot Arena](https://chat.lmsys.org/)-style blind benchmark — but for agent harnesses, not models.**

**[🔴 Try the live arena →](https://www.harness-arena.ai)**

Agentic Harness Arena runs the same task through multiple agent harnesses — Claude Code, Codex CLI, and more — holding the model constant, collects their deliverables in isolated workspaces, and lets people judge the results blind. Identities are only revealed after a score is submitted, and every verdict rolls up into a public Elo leaderboard.

If you've used Chatbot Arena to compare *models*, this is the same idea one layer up: comparing the *harness* — the CLI, tools, prompts, permissions, and execution environment wrapped around a model.

Contents

• Why Harness Arena?
• How a run works
• Supported harnesses
• Architecture
• Features
• Quick start
• Dataset format
• Configuration
• Deployment
• Add a harness
• Status
• Contributing
• License

Why Harness Arena?

The model is only one part of an agentic workflow. The harness — the CLI, tools, prompts, permissions, and execution environment — shapes the quality of the final result just as much. Two harnesses running the identical model