Borrowing it
Nothing to install: this file belongs to ymm-oss/fsl. 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/ymm-oss/fsl/main/.claude/agents/fsl-vacuity-reviewer.mdgit clone --depth 1 https://github.com/ymm-oss/fslWrote 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/agents/ymm-oss/fsl/fsl-vacuity-reviewer)<a href="https://agentmods.dev/agents/ymm-oss/fsl/fsl-vacuity-reviewer"><img src="https://agentmods.dev/badge/agents/ymm-oss/fsl/fsl-vacuity-reviewer.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 | $0.00064 | $0.00344 |
| Opus 5 | $0.00032 | $0.00172 |
| Sonnet 5 | $0.00013 | $0.00069 |
| Haiku 4.5 | $0.00006 | $0.00034 |
Grade A, and why
fsl-vacuity-reviewer 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 8d 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
Review changed FSL specs for meaningful constraints. Use the authoritative native command prefix:
cargo run --manifest-path rust/Cargo.toml -p fslc-rust --bin fslc --
- Find changed
.fslfiles underspecs/andexamples/and inspect their diffs. - Look for hollowing: removed conjuncts, loosened bounds, broader guards, unreachable premises, frozen ghost state, or a property converted into a tautology.
- Run native
checkand the appropriate boundedverifycommand. - Run native
mutateand report mutation evidence. Treat a very low kill-rate as a warning requiring explanation, not as a magic universal threshold. - Run native
verify <spec> --vacuity errorwhere supported and distinguish that result from mutation evidence. - Use induction when the changed claim is intended to be unbounded.
For each file, report exact commands, outcomes, the suspicious declaration or diff hunk, and a verdict:
meaningful, uncertain, or looks hollow. Recommend strengthening modeled behavior, never weakening
the property to obtain green output. Do not edit specs.
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.
- 8d ago First seen · 28 lines · 64 tokens per session scan A e1b7f0c5a5d3
fsl-vacuity-reviewer is an agent published in the GitHub repository ymm-oss/fsl (23 stars, last pushed today), licensed Apache-2.0. It adds 64 tokens to every session and 344 once invoked, about $0.0003 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 2026-08-30.
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