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 agentmods add skills/slbug/claude-ruby-grape-rails/challengenpx skills add slbug/claude-ruby-grape-rails --skill challengegit clone --depth 1 https://github.com/slbug/claude-ruby-grape-railsWrote 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/slbug/claude-ruby-grape-rails/challenge)<a href="https://agentmods.dev/skills/slbug/claude-ruby-grape-rails/challenge"><img src="https://agentmods.dev/badge/skills/slbug/claude-ruby-grape-rails/challenge.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 | $0.00033 | $0.01412 |
| Opus 5 | $0.00016 | $0.00706 |
| Sonnet 5 | $0.00007 | $0.00282 |
| Haiku 4.5 | $0.00003 | $0.00141 |
Grade A, and why
rb: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 3d 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 — 176 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Challenge Mode Reviews
Rigorous, critical review patterns. Push beyond first solutions to ensure quality.
Iron Laws - Never Violate These
- No approval without verification - Don't approve until all concerns addressed
- Assume bugs exist - Look for edge cases, race conditions, missing handlers
- Question everything - Even "obvious" code can hide issues
- Demand proof - Ask for tests, show state transitions, verify behavior
Adversarial Lenses (Apply to ALL Modes)
Before diving into mode-specific checks, apply these four lenses:
- "What Would Break This?" — Describe realistic scenarios where this code fails catastrophically. Not edge cases — production failure modes under load, during deploys, with unexpected data.
- "Assumption Stress Test" — List every assumption this code relies on. Which are most fragile? (e.g., "assumes user always has an email", "assumes this query returns < 1000 rows")
- "Contradictions Finder" — Find contradictions between tests and implementation, docs and behavior, or between different parts of the code changes.
- "Overcomplicated?" — For every block of code, ask: would a senior engineer say this is overcomplicated? If you write 200 lines and it could be 50, that's a finding.
Challenge Modes
Active Record Challenge (/rb:challenge active record)
Grill the developer on database changes:
Migration Safety
- Will this migration lock the table in production?
- What happens to existing records without the new field?
- Is the migration reversible?
- Are there any unsafe operations (column removal, type change)?
Query Performance
- Have you introduced any N+1 queries?
- Are there missing indexes for new WHERE clauses?
- Will this query scale with data growth?
Schema Integrity
- Are all constraints enforced at database level?
- What happens during rolling deployment (old code, new schema)?
- Are foreign key cascades correct?
Backward Compatibility
- Will old code work during deployment?
- Are there any breaking changes to the model API?
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.
- 3d ago First seen · 176 lines · 33 tokens per session scan A 5fa18451c510
rb:challenge is a skill published in the GitHub repository slbug/claude-ruby-grape-rails (7 stars, last pushed 4d ago), licensed MIT. It adds 33 tokens to every session and 1,412 once invoked, about $0.0002 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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