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Arena (Parallel Candidate Tournament)

Spawns N parallel candidates on the same task, cross-judges them against a rubric, picks a base, and grafts the strongest parts of the losers into it.

Dev & CodingAdvanced★ 3,867⑂ 267AI score 8/10Last updated: Nov 9, 2026

What it does

  • Sends one identical prompt to N subagents in parallel so you get multiple competing versions of the same artifact.
  • Runs a six-phase todolist: Frame → Fan out → Cross-judge → Pick → Graft → Verify.
  • Derives a task-specific rubric (3–6 gradeable criteria) up front, then spawns a read-only judge from a different model family than the parent to score candidates.
  • Picks one base (the one a maintainer can extend most easily), grafts only one or two worthwhile ideas per losing candidate by hand, then verifies the result.
  • Includes detailed fallbacks for rejected model slugs, dropped seats, and candidates that produce no output.

Who it's for

  • Developers working on artifacts where locking in the wrong shape early is costly: architecture, schemas, public APIs.
  • Claude Code / Cursor users who run background subagents routinely.
  • Users of the wider pstack skill set (poteto-mode, prove-it-works, etc.).

Example uses

  1. "Throw this refactor plan in the arena" → three implementations land in separate git worktrees, then get compared and merged.
  2. Designing a new CLI's command surface: run several distinct design directions and adopt the one with the cleanest boundary as the base.
  3. Writing a migration script: generation-bound work, so run the same model N times and graft only the error-handling logic from a loser.

· · · Install guide · · ·

Try it now, no install

Paste this into Claude to use the skill without installing anything.

Read the instructions in this file and follow them to help me:
https://raw.githubusercontent.com/backnotprop/pstack/HEAD/skills/arena/SKILL.md

What I want: (describe your task here)

If Claude can't open the link, open it yourself and paste the contents instead.

↓ If it works for you, download the ZIP below and install it. Then it runs on its own — no pasting each time.

Install in the Claude app (no terminal)
  1. Download the ZIP with the button below.
  2. In Claude, open Settings → Capabilities and turn on 'Code execution and file creation'. (one time)
  3. Go to Customize → Skills → + → 'Upload a skill' and upload the ZIP.
↓ Download ZIP
Install in Claude Code

Let Claude do it — paste this into Claude Code

Install the skill I found on AI Skill Mart.
Copy the skills/arena folder from the GitHub repo backnotprop/pstack into my ~/.claude/skills/backnotprop-arena/.
When it's done, tell me in one line what this skill can do.

Install with a command instead

git clone https://github.com/backnotprop/pstack.git && mkdir -p ~/.claude/skills && cp -r pstack/skills/arena ~/.claude/skills/

⚠ This is a third-party skill. Check the source repository before installing.

  1. Open a terminal.
  2. Clone the repo: git clone https://github.com/backnotprop/pstack.git
  3. Create the skills directory: mkdir -p ~/.claude/skills
  4. Copy the skill: cp -r pstack/skills/arena ~/.claude/skills/
  5. (Recommended) Copy the skills it references too: poteto-mode, prove-it-works, separate-before-serializing-shared-state, redesign-from-first-principles.
  6. (Optional) Create ~/.claude/rules/pstack-models.md with arena runners and arena cross-judge pool lines listing the model slugs available in your harness; without it the skill uses its defaults.
  7. Restart Claude Code and invoke it with /arena or "arena this".
View source on GitHub ↗License: MIT