auto-arena

auto-arena is a skill for Claude Code, Codex from agentscope-ai/OpenJudge. It costs 103 tokens per session (2,472 once invoked), scanned A, original, Apache-2.0.

An automated system for comparing responses from two or more AI models or agents. It creates test questions, evaluation criteria, pairwise judgments, rankings, and reports.

In plain words
What is it for?
Use it to test model endpoints against a task, collect their answers, have a judge compare them, and produce win rates, rankings, charts, and comparison reports.
Why use it?
It removes the need to prepare all test cases and compare every response manually.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to test model endpoints against a task, collect their answers, have a judge compare them, and produce win rates, rankings, charts, and comparison reports.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/agentscope-ai/openjudge/auto-arena
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add agentscope-ai/OpenJudge --skill auto-arena
Clone the repo
git clone --depth 1 https://github.com/agentscope-ai/OpenJudge

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for auto-arena

README.md
[![agentmods](https://agentmods.dev/badge/skills/agentscope-ai/openjudge/auto-arena/github.svg)](https://agentmods.dev/skills/agentscope-ai/openjudge/auto-arena)
Your own site
<a href="https://agentmods.dev/skills/agentscope-ai/openjudge/auto-arena"><img src="https://agentmods.dev/badge/skills/agentscope-ai/openjudge/auto-arena/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for auto-arena

Your own site · 80×15
<a href="https://agentmods.dev/skills/agentscope-ai/openjudge/auto-arena"><img src="https://agentmods.dev/badge/skills/agentscope-ai/openjudge/auto-arena.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 103 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,472 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 5 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Data Exfiltration · line 98
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 109
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 140
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 144
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
  • medium Data Exfiltration · line 149
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00103 $0.02472
Opus 5 $0.00051 $0.01236
Sonnet 5 $0.00021 $0.00494
Haiku 4.5 $0.00010 $0.00247

Measured 11d ago against content hash d3b6fdbb3629, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

auto-arena scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/auto-arena/SKILL.md · 275 lines

How it starts

The opening of the file, as written. The whole thing — 275 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Auto Arena Skill

End-to-end automated model comparison using the OpenJudge AutoArenaPipeline:

  1. Generate queries — LLM creates diverse test queries from task description
  2. Collect responses — query all target endpoints concurrently
  3. Generate rubrics — LLM produces evaluation criteria from task + sample queries
  4. Pairwise evaluation — judge model compares every model pair (with position-bias swap)
  5. Analyze & rank — compute win rates, win matrix, and rankings
  6. Report & charts — Markdown report + win-rate bar chart + optional matrix heatmap

Prerequisites

# Install OpenJudge
pip install py-openjudge

# Extra dependency for auto_arena (chart generation)
pip install matplotlib

Gather from user before running

Info Required? Notes
Task description Yes What the models/agents should do (set in config YAML)
Target endpoints Yes At least 2 OpenAI-compatible endpoints to compare
Judge endpoint Yes Strong model for pairwise evaluation (e.g. gpt-4, qwen-max)
API keys Yes Env vars: OPENAI_API_KEY, DASHSCOPE_API_KEY, etc.
Number of queries No Default: 20
Seed queries No Example queries to guide generation style
System prompts No Per-endpoint system prompts
Output directory No Default: ./evaluation_results
Report language No "zh" (default) or "en"

Quick start

CLI

# Run evaluation
python -m cookbooks.auto_arena --config config.yaml --save

# Use pre-generated queries
python -m cookbooks.auto_arena --config config.yaml \
  --queries_file queries.json --save

# Start fresh, ignore checkpoint
python -m cookbooks.auto_arena --config config.yaml --fresh --save

# Re-run only pairwise evaluation with new judge model
# (keeps queries, responses, and rubrics)
python -m cookbooks.auto_arena --config config.yaml --rerun-judge --save

Python API

import asyncio
from cookbooks.auto_arena.auto_arena_pipeline import AutoArenaPipeline

async def main():
    pipeline = AutoArenaPipeline.from_config("config.yaml")
    result = await pipeline.evaluate()

    print(f"Best model: {result.best_pipeline}")
    for rank, (model, win_rate) in enumerate(result.rankings, 1):
        print(f"{rank}. {model}: {win_rate:.1%}")

asyncio.run(main())

Read the full file on GitHub · 275 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 11d ago First seen · 275 lines · 103 tokens per session scan A d3b6fdbb3629

Subscribe to this mod's changes

auto-arena is a skill published in the GitHub repository agentscope-ai/OpenJudge (826 stars, last pushed 3d ago), licensed Apache-2.0. It adds 103 tokens to every session and 2,472 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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