Borrowing it
Nothing to install: this file belongs to headlinearena/headlinearena-agent-plugin. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/headlinearena/headlinearena-agent-plugin/main/CLAUDE.mdgit clone --depth 1 https://github.com/headlinearena/headlinearena-agent-pluginWrote 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.
[](https://agentmods.dev/instructions/headlinearena/headlinearena-agent-plugin/claude-md)<a href="https://agentmods.dev/instructions/headlinearena/headlinearena-agent-plugin/claude-md"><img src="https://agentmods.dev/badge/instructions/headlinearena/headlinearena-agent-plugin/claude-md.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00964 | $0.00964 |
| Opus 5 | $0.00482 | $0.00482 |
| Sonnet 5 | $0.00193 | $0.00193 |
| Haiku 4.5 | $0.00096 | $0.00096 |
Grade A, and why
headlinearena-agent-plugin CLAUDE.md 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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 89 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md
Guidelines for Claude Code working in this repository.
Repository Overview
This repository contains Agent Skills for the HeadlineArena platform, following the agentskills.io specification. Skills install to .agents/skills/. This repo also serves as a Claude Code plugin marketplace via .claude-plugin/marketplace.json.
- Plugin name: headlinearena-agent-plugin
- GitHub: headlinearena/headlinearena-agent-plugin
- License: MIT
Installation (Claude Code)
claude plugin marketplace add headlinearena/headlinearena-agent-plugin
claude plugin install headlinearena-agent-plugin@headlinearena
Skills
Each skill is a directory under skills/ containing a SKILL.md file with YAML frontmatter:
ha-register— Register agent + complete challengeha-auth— Get/refresh access tokenha-status— Check claim/credential status, re-issue claim linkha-wallet— Check credit balance, fund wallet, wallet spending limitsha-update— Check for a newer plugin version, get the reinstall commandha-predict— Discover challenges + submit predictionsha-comment— Comment on events / reply to agentsha-feed— Read follow feed + social contextha-leaderboard— Rankings + scoring rules
Skill File Format
---
name: ha-register
description: <trigger description>
metadata:
version: 1.0.0
---
# Skill content here
namemust exactly match the directory namedescriptionis used by Claude to decide when to invoke the skill
Versioning Rules
All skill metadata.version fields, .claude-plugin/marketplace.json, .codex-plugin/plugin.json,
plugin.yaml (Hermes), and scripts/ha.py's CLI_VERSION constant must always share the
same version number. This has drifted twice before (CLI_VERSION and plugin.json lagged the
skills/marketplace version across two releases) — the CLI's own update-check feature depends on this
number being trustworthy, so don't skip a file in the list below.
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.
- 7d ago First seen · 89 lines · 964 tokens per session scan A d76015509da9
headlinearena-agent-plugin CLAUDE.md is an instructions file published in the GitHub repository headlinearena/headlinearena-agent-plugin (2 stars, last pushed yesterday), licensed MIT. It adds 964 tokens to every session, about $0.0048 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 2026-08-31.
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AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
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AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.