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 bop-clocktower/canary --skill canary-cassandragit clone --depth 1 https://github.com/bop-clocktower/canaryWrote 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/bop-clocktower/canary/canary-cassandra)<a href="https://agentmods.dev/skills/bop-clocktower/canary/canary-cassandra"><img src="https://agentmods.dev/badge/skills/bop-clocktower/canary/canary-cassandra/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/bop-clocktower/canary/canary-cassandra"><img src="https://agentmods.dev/badge/skills/bop-clocktower/canary/canary-cassandra.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00178 | $0.02196 |
| Opus 5 | $0.00089 | $0.01098 |
| Sonnet 5 | $0.00036 | $0.00439 |
| Haiku 4.5 | $0.00018 | $0.00220 |
Grade A, and why
canary-cassandra scanned grade A with 1 finding 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 4d 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.
Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
first-party **script path** that a `spawnSync`/`execFileSync`-family call then How it starts
The opening of the file, as written. The whole thing — 181 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Canary Cassandra
Cassandra Cain reads the fake. So does this skill.
A test with no assertions is easy to find and everybody already looks for it. The dangerous test is the one with assertions that cannot fail — it has coverage, it goes green, and it goes green identically against the bug it was written to catch. Three of those shipped in this project in a single cycle (recorded in [#486]) and every gate the repo owned read all three as healthy.
Cassandra is Tier-0: deterministic, no LLM, no network, no execution.
What it finds
| Rule | Severity | Fires on |
|---|---|---|
VAC-001 |
critical | An assertion whose expectation is identical to the value it checks — expect(true).toBe(true), assert x == x |
VAC-002 |
warning | The test never references the target it claims to cover |
VAC-003 |
warning | Every assertion in the test asserts an absence, and none of them observes the target — so nothing proves it ran |
VAC-001 is deterministic, hence critical: no implementation can fail it.
VAC-002 and VAC-003 depend on resolving a target, which is inference, so
they are warning and carry a fidelity tier.
Run it
Two doors, one detector. Both run the same engine rules, so they cannot disagree about a finding or about the denominator.
canary vacuity-check tests/ # human-readable
canary vacuity-check tests/ --json # verdict + denominator + skips
canary vacuity-check tests/a.test.ts # one file
As a skill, for an orchestrator or a CI step composing all four Tier-0 detectors:
canary skills run canary-cassandra -- tests/
canary skills run canary-cassandra -- tests/ --json --strict
Usage, flags, and the full rule list — this one is runnable verbatim, needs no fixtures, and is what CI executes to prove the doc still matches the CLI:
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 4d ago Changed · +38 lines beeddae6dfb7
- 10d ago First seen · 143 lines · 178 tokens per session scan A f9d4e3bc221a
canary-cassandra is a skill published in the GitHub repository bop-clocktower/canary (4 stars, last pushed today), licensed MIT. It adds 178 tokens to every session and 2,196 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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