canary-katana

canary-katana is a skill for Claude Code from bop-clocktower/canary. It costs 94 tokens per session (2,636 once invoked), scanned A, original, MIT.

A test-change tracker that records deleted and skipped tests in an append-only history, including who changed them, when, why, and which commit was involved. It raises an alarm only when a deletion removes the last test covering an area marked high-risk.

In plain words
What is it for?
Use it when reviewing code changes that remove or skip Python, JavaScript, or TypeScript tests, especially in areas already identified as high risk.
Why use it?
Tests can disappear or be muted while the suite still passes, leaving an unnoticed coverage gap. This keeps a record of those changes and highlights the most dangerous loss of protection.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the canary plugin — 23 skills, 13 commands, 8 agents, 4 hooks shipped together

Good fit Use it when reviewing code changes that remove or skip Python, JavaScript, or TypeScript tests, especially in areas already identified as high risk.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/bop-clocktower/canary/canary-katana
Install

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.

Any agent
npx skills add bop-clocktower/canary --skill canary-katana
Clone the repo
git clone --depth 1 https://github.com/bop-clocktower/canary

Made for: Claude Code.

Or install canary, the plugin that ships this one along with the rest of its 23 skills, 13 commands, 8 agents, 4 hooks.

Wrote 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.

agentmods badge for canary-katana

README.md
[![agentmods](https://agentmods.dev/badge/skills/bop-clocktower/canary/canary-katana/github.svg)](https://agentmods.dev/skills/bop-clocktower/canary/canary-katana)
Your own site
<a href="https://agentmods.dev/skills/bop-clocktower/canary/canary-katana"><img src="https://agentmods.dev/badge/skills/bop-clocktower/canary/canary-katana/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.

agentmods 80×15 button for canary-katana

Your own site · 80×15
<a href="https://agentmods.dev/skills/bop-clocktower/canary/canary-katana"><img src="https://agentmods.dev/badge/skills/bop-clocktower/canary/canary-katana.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 94 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,636 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00094 $0.02636
Opus 5 $0.00047 $0.01318
Sonnet 5 $0.00019 $0.00527
Haiku 4.5 $0.00009 $0.00264

Measured 5d ago against content hash 0e5dd3ffbc6f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

canary-katana 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 5d ago.

The scan reads SKILL.md. This mod also ships 4 executable files (scripts/alarm.mjs, scripts/cli.mjs, scripts/diffscan.mjs, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

agents/skills/claude-code/canary-katana/SKILL.md · 244 lines

How it starts

The opening of the file, as written. The whole thing — 244 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Canary Katana

Named for Tatsu Yamashiro's Soultaker — the blade that captures the soul of whatever it cuts. A deleted test is coverage that leaves without a trace: the suite still goes green, the gap is invisible, and nobody notices until the bug it caught ships. Katana catches every test as it is removed or muted, records who took it and why, and raises its voice only when the cut was the last thing guarding a critical path.

Tier-0 deterministic analysis: no LLM, no network, no secrets, no dependency on any other skill at runtime.

What it captures

Event Detected from a diff
removed a def test_* / async def test_* (Python) or describe/it/test('…') (JS/TS) that left on a - line and did not come back on the + side
skipped a +-side skip/mute marker: @pytest.mark.skip / skipif / xfail, or it.skip / test.skip / describe.skip, it.only / test.only, xit / xdescribe / fit

A test flipped in place from it('x') to it.skip('x') is one event, not two: the skip supersedes the removal so the ledger never double-counts a mute-in-place as both a deletion and a skip.

The general form of that rule is the emphasis above: a (file, title) that reappears on the + side was modified, not removed. Without it, any rewrite of a declaration line recorded a deletion of a test that is still in the tree — a prettier reflow of a long signature, or a .skip lifted in place, was enough (#783). The ledger is append-only, so such a row is permanent and cannot be corrected without the hand-edit the ledger exists to prevent; and a consumer that attributes on the newest matching row would hand every test under a phantom removal of a describe the wrong ticket. A rename is still a removal — the old title's coverage really is gone.

Read the full file on GitHub · 244 lines

Files

What ships with it

4 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.

Changes

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.

  1. 5d ago Changed · +71 lines 0e5dd3ffbc6f
  2. 10d ago First seen · 173 lines · 94 tokens per session scan A 8f256197cc9f

Subscribe to this mod's changes

canary-katana is a skill published in the GitHub repository bop-clocktower/canary (4 stars, last pushed today), licensed MIT. It adds 94 tokens to every session and 2,636 once invoked, about $0.0005 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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