Arena: Make 100 Claude Agents Fight to Get You a Better Answer

Arena is a free skill for Claude Code made by Jake Schincariol. When Claude gives you an answer you don't like, you type /arena instead of asking again and again. Arena gives the exact same task to 100 sub-agents, runs a knockout tournament between their answers, and brings back the one that survived.

What Arena does for you: every agent gets the same task, word for word, plus its own strategy card: a way of reasoning, a workflow and a strategy. So the 100 answers come out different. Then the agents pair off. Each one attacks the other's answer, defends its own and rewrites it. A separate judge agent scores both on a written rubric, and the loser is out. 100 becomes 50, then 25, 13, 7, 4, 2 and 1.

You get back the winning answer, the attacks it beat on the way, and how many rounds it took. If you started from an answer you rejected, a last judge compares the winner with it, and Arena tells you the score even when your old answer wins.

How to install Arena: copy the repo URL below, paste it into Claude Code, and say: install this skill, then confirm /arena works.

Or install it by hand (from the README). Arena needs Claude Code and Python 3.8 or newer, and there is nothing to pip install.

Best practices for Arena:

• Use quick mode for everyday jobs. /arena --quick runs 16 agents and about 91 sub-agent calls. A full 100-agent run is about 595 calls, so save it for the answer that matters.
• Write a clear task first. The agents only see a task file, not your chat. A vague task gives you 100 flavors of vague.
• Turn on accept-edits mode (Shift+Tab). Every agent writes a file inside .arena/, and the default mode asks you to approve each one.
• Read the attacks, not just the winner. The winning answer comes with the attacks it survived, which shows you where a weak spot was.

Prompts to try with Arena:

• Everyday writing, ideas, small fixes: /arena --quick (16 agents).
• A harder problem: /arena --agents 32 (about 187 calls).
• The one answer that really matters: plain /arena with all 100 agents.