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Arena
When you don't like Claude's answer, /arena runs a knockout tournament of sub-agents on the same task and hands you the one that survived.
- Claude Code
- Python 3.8+
- Setup
- 2 min
- Level
- Beginner
- Stars
- 306
- License
- MIT
What it does
A sub-agent is a separate copy of Claude that Claude Code starts to work on one job. Arena starts up to 100 of them and gives each the exact same task, plus a different strategy card that changes how it reasons and works.
They pair off, attack each other's answers, defend and revise, and a judge scores each match on a written rubric. The loser is out, round after round, until one answer is left. You get that answer, the attacks it beat and how many rounds it took. It never edits your files: everything happens inside a .arena folder.
Install it
- Open Claude Code.
- Paste the prompt below. Claude installs the skill and checks that /arena works.
- Prefer to do it yourself? Use the terminal commands in the next box. They give you plain /arena.
Paste this into Claude
https://github.com/Jakeschincariol/arena-skill Install this skill, then confirm /arena works.
Or copy the folder yourself
git clone https://github.com/Jakeschincariol/arena-skill.git cp -r arena-skill/skills/arena ~/.claude/skills/
Use it
- After an answer you didn't like, type /arena. It uses your last request as the task and the rejected answer as the one to beat.
- For everyday tasks use the quick mode with 16 competitors, for example: /arena --quick write the headline for our pricing page
- Pick a number of competitors with --agents, for example: /arena --agents 32 fix the flaky test in tests/test_api.py
- Switch on accept-edits mode (Shift+Tab) first, or you will get one permission prompt per sub-agent file.
Good to know
The skill is free, but the tokens are yours. The default 100-agent run makes 595 sub-agent calls in 70 waves and takes a while. --quick (16 agents) makes 91 calls. The skill prints the numbers before it starts.
Installed as a plugin (/plugin marketplace add Jakeschincariol/arena-skill, then /plugin install arena-skill@arena-skill) it shows up as /arena-skill:arena. The judges are Claude too, so the winner is the strongest answer the tournament found, not proof it is right.
Links
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