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.
npx skills add fusengine/agents --skill challengegit clone --depth 1 https://github.com/fusengine/agentsWrote 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/skills/fusengine/agents/challenge)<a href="https://agentmods.dev/skills/fusengine/agents/challenge"><img src="https://agentmods.dev/badge/skills/fusengine/agents/challenge/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.
<a href="https://agentmods.dev/skills/fusengine/agents/challenge"><img src="https://agentmods.dev/badge/skills/fusengine/agents/challenge.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00052 | $0.01546 |
| Opus 5.5 | $0.00021 | $0.00618 |
| Sonnet 5.5 | $0.00010 | $0.00309 |
| Haiku 4.5 | $0.00005 | $0.00155 |
Grade A, and why
challenge 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 1mo 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 — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.
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.
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
- Refute by default -- a claim is FALSE until proven otherwise. Never "are you sure?" -- always a concrete failure scenario + the untested hypothesis it exposes.
- Fresh context mandatory -- intake is the claim + its evidence ONLY, never the author's reasoning. Inheriting the author's angle reproduces the author's blind spot.
- Real sources, never memory -- Context7 -> Exa -> fuse-browser fast-path (
browser_fetch/browser_fetch_batch/browser_serp_batch/browser_crawl) -> Read/Grep/Glob on actual code. Docs and code beat recollection. - Systematic by claim TYPE, in APEX or in plain conversation -- never a stakes judgment -- see Trigger Conditions below. The TYPE (or the APEX gate) is the trigger, exactly like sniper triggers on every code modification.
- Bounded -- max 2 refutation rounds, then a mandatory verdict. No open-ended ping-pong.
- Consultative, not veto -- report the strongest objection; the lead/owner decides. Read-only, edits nothing.
- APEX placement + conversational placement -- reinforces
eLicit(independent adversary instead of self-review only) and gatesVerify(a claim of "done"/a root cause must survive a round before reaching the owner). Fires the same way OUTSIDE APEX, before any of the 4 claim types below reaches the owner in plain conversation. Does NOT toucheXamine-- that's sniper's code-correctness lane.
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.
- 1mo ago First seen · 81 lines · 52 tokens per session scan A 3a319df83e2c
challenge is a skill published in the GitHub repository fusengine/agents (33 stars, last pushed 8d ago), licensed MIT. It adds 52 tokens to every session and 1,546 once invoked, about $0.0002 per session on Opus 5.5. 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.
Other skills, from other repositories
radin-review
Review a commit, PR, directory or range for the simplest native solution, maintainability and documented repo rubrics, triage findings with the user. Use for /radin-review, "review and log to backlog".
reviewing-code
Reviews code. Use when reviewing code implementations, assessing code quality, running a security review, checking spec or design system compliance, or conducting an end-of-build whole-project review against PRD success criteria.
assessing-quality
Conducts quality reviews of non-code artefacts. Use when reviewing or critiquing Skills, agents, workflows, documentation, or written materials, assessing quality against standards, or providing structured feedback.
code
Review code through the lens of a senior engineer.
gemini
Cross-model second opinion from Google Gemini — a different AI reviewing the same changes, with deep Google ecosystem knowledge. Three modes: review (pass/fail gate for Google Ads campaigns, SEO metadata, or code), challenge (adversarial stress-test that tries to break your changes), and consult (open Q&A with Gemini…
boundaries
Analyze Phoenix context boundaries and module coupling via mix xref. Use when checking cross-context calls, validating dependencies, before splitting modules, or reviewing architecture.