Borrowing it
Nothing to install: this file belongs to nwiizo/cargo-coupling. 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/nwiizo/cargo-coupling/main/.agents/skills/mutants/SKILL.mdgit clone --depth 1 https://github.com/nwiizo/cargo-couplingWrote 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/nwiizo/cargo-coupling/mutants)<a href="https://agentmods.dev/skills/nwiizo/cargo-coupling/mutants"><img src="https://agentmods.dev/badge/skills/nwiizo/cargo-coupling/mutants/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/nwiizo/cargo-coupling/mutants"><img src="https://agentmods.dev/badge/skills/nwiizo/cargo-coupling/mutants.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 | $0.00030 | $0.00348 |
| Opus 5.5 | $0.00012 | $0.00139 |
| Sonnet 5.5 | $0.00006 | $0.00070 |
| Haiku 4.5 | $0.00003 | $0.00035 |
Grade A, and why
mutants 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 20d 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.
What it actually says
Mutation Testing
Run the requested scope, or start with the changed files. A full-project run is appropriate when requested; mutation testing is not a default release requirement.
rtk proxy cargo mutants --no-shuffle -f src/config.rs
rtk proxy cargo mutants --no-shuffle -F 'function_name'
Use cargo mutants --help for installed options and job limits. Inspect the actual
run output and mutants.out/missed.txt to distinguish outcomes:
| Result | Interpretation |
|---|---|
| caught | Tests detected the mutation |
| missed | Tests did not detect it; inspect reachability and observable behavior |
| unviable | The mutated program did not compile |
| timeout | Execution exceeded its limit; investigate before assigning a cause |
Prioritize changed business behavior and actionable gaps. Existing misses may be relevant to the requested scope; do not dismiss CLI or output behavior solely by filename. Some surviving mutations preserve behavior or cannot be meaningfully exercised, so zero missed mutants is not a universal completion criterion.
For diagnosis, report actionable misses and unresolved cases with evidence. When test improvements are requested, add assertions for observable behavior, run the affected tests, and rerun the relevant mutations. Complete with caught/missed/ unviable/timeout results for the tested scope and explain remaining limitations.
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.
- 20d ago Changed · -1 lines · +9 tokens per session 26bbef966770
- 1mo ago Changed · -25 lines · +21 tokens per session e97174532143
- 1mo ago First seen · 63 lines · 0 tokens per session scan A a79bd33529d8
mutants is a skill published in the GitHub repository nwiizo/cargo-coupling (116 stars, last pushed 2d ago), licensed MIT. It adds 30 tokens to every session and 348 once invoked, about $0.0001 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 2026-09-01.
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