Use before a root-cause, done/verified claim, irreversible action, or 2nd-time fix reaches the owner (APEX or plain conversation); also fires at every eLicit/Verify gate. Not for code correctness (use sniper).
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
<objective>
Challenge is the adversarial verification protocol behind the `challenger` agent: refute-by-default, fresh-context intake (claim + evidence only, never the author's reasoning), sources-backed (Context7 -> Exa -> fuse-browser -> code), bounded to 2 refutation rounds ending in a mandatory verdict (CONFIRMED / REFUTED / UNCERTAIN). It is consultative, not a veto -- it reports the strongest objection and leaves the decision to the lead/owner.
It fires systematically by claim TYPE, not by a stakes judgment: before a root-cause conclusion, a done/verified claim, an irreversible action (commit/deploy/rm/push), or a 2nd-time fix reaches the owner, whether inside an APEX task or in plain conversation -- plus automatically at every APEX eLicit round and Verify gate. It does not cover code correctness, lint, or type validation -- that stays sniper's lane at eXamine.
</objective>
# Challenge Skill
Reusable protocol behind the `challenger` agent. Also usable directly inside any expert agent's own eLicit step when a dedicated agent call is overkill -- the discipline is the same either way.
## The 7 Principles
…
The line at the top of this page pins the label git:20260729.3b91eed, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
GET https://markdownregistry.com/api/v1/artifacts/art_g3n2boseh6kxlchz
GET https://markdownregistry.com/api/v1/resolve?ref=fusengine/claude-plugins/challenge
GET https://markdownregistry.com/api/v1/blob/3a319df83e2c98e311011c6cfdff243950916d3e4ea910bbc9e9125633e128d9
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
fusengine/claude-plugins · plugins/ai-pilot/skills/agent-creator/SKILL.md · Use when creating expert agents. Generates agent.md with frontmatter, hooks, required sections, and skill references.
fusengine/claude-plugins · plugins/ai-pilot/skills/brainstorming/SKILL.md · Use when creating a feature/component or adding functionality. Fires BEFORE APEX Analyze to refine requirements via…
fusengine/claude-plugins · plugins/ai-pilot/skills/elicitation/SKILL.md · Use when an expert agent self-reviews and self-corrects code after the Execute phase, before sniper validation…
fusengine/claude-plugins · plugins/ai-pilot/skills/fuse-browser-usage/SKILL.md · Use when about to call any mcp__fuse-browser__* tool. Routes fetch/crawl/SERP vs live browser session vs screenshot…
fusengine/claude-plugins · plugins/ai-pilot/skills/lead-orchestration/SKILL.md · Use when you are the LEAD (main session) and an owner request arrives that needs agents -- intake, routing, briefs…
fusengine/claude-plugins · plugins/ai-pilot/skills/pr-summary/SKILL.md · Summarize current pull request with diff, comments, and changed files. Use when reviewing PRs or before merging.
fusengine/claude-plugins · plugins/ai-pilot/skills/react-effects-audit/SKILL.md · Use when auditing React or Next.js components for unnecessary or unsafe useEffect usage -- detects 9 anti-patterns from…
fusengine/claude-plugins · plugins/ai-pilot/skills/research/SKILL.md · Use when researching documentation, best practices, or complex technical investigations -- Context7 + Exa + Sequential…
alirezarezvani/claude-skills · c-level-advisor/executive-mentor/skills/challenge/SKILL.md · Use before committing serious resources to a plan, or when feedback has been suspiciously positive. Runs a pre-mortem…
pedrohcgs/claude-code-my-workflow · .claude/skills/challenge/SKILL.md · Stress-test a finding against the choices you did not make. Enumerates the discrete forks a competent analyst could…
oliver-kriska/claude-elixir-phoenix · plugins/elixir-phoenix/skills/challenge/SKILL.md · Challenge mode reviews - rigorous questioning before approving changes. Use when you want thorough scrutiny of Ecto…
athola/claude-night-market · plugins/gauntlet/skills/challenge/SKILL.md · Presents adaptive codebase challenge questions with multiple-choice and trace exercises. Use when testing contributor…
agentii-ai/agentii-investment-intelligence · plugins/vertical-plugins/scenarios/skills/agentii/challenge/SKILL.md · Adversarial verification of research theses — cross-run/cross-thesis contradiction via the entity index, pre-mortem…
fusengine/agents · plugins/ai-pilot/skills/challenge/SKILL.md · Use before a root-cause, done/verified claim, irreversible action, or 2nd-time fix reaches the owner (APEX or plain…
