Borrowing it
Nothing to install: this file belongs to purupurupu/css-noop-checker. 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/purupurupu/css-noop-checker/main/CLAUDE.mdgit clone --depth 1 https://github.com/purupurupu/css-noop-checkerWrote 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/instructions/purupurupu/css-noop-checker/claude-md)<a href="https://agentmods.dev/instructions/purupurupu/css-noop-checker/claude-md"><img src="https://agentmods.dev/badge/instructions/purupurupu/css-noop-checker/claude-md/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/instructions/purupurupu/css-noop-checker/claude-md"><img src="https://agentmods.dev/badge/instructions/purupurupu/css-noop-checker/claude-md.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 | $0.02862 | $0.02862 |
| Opus 5 | $0.01431 | $0.01431 |
| Sonnet 5 | $0.00572 | $0.00572 |
| Haiku 4.5 | $0.00286 | $0.00286 |
Grade A, and why
css-noop-checker CLAUDE.md 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 9d 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 — 219 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
Project Overview
css-noop-checker is a Chrome DevTools extension (Manifest V3) that detects "no-op" CSS properties on the selected element. Built with React 19, TypeScript 5.9, and Vite 7.
Commands
pnpm dev— Watch-mode build (vite build --watch)pnpm build— Type-check withtsc -bthen bundle with Vitepnpm lint— Lint with Oxlintpnpm fmt— Format with Oxfmtpnpm fmt:check— Check formatting without writingpnpm test— Run tests with Vitestpnpm test:watch— Run tests in watch modepnpm test:e2e— Run Playwright browser integration testspnpm test:e2e:ui— Run Playwright tests with interactive UI
Package manager is pnpm (not npm/yarn). Runtime: Node.js 24, pnpm 10 (managed via .mise.toml).
Tech Stack
- Build: Vite 7 + SWC via
@vitejs/plugin-react-swc - Framework: React 19 (
react-jsxtransform) - Language: TypeScript 5.9 (strict,
verbatimModuleSyntax,erasableSyntaxOnly) - Linting: Oxlint (
.oxlintrc.json) — plugins: typescript, react - Formatting: Oxfmt (
.oxfmtrc.jsonc) — singleQuote, trailingComma all, printWidth 100 - Testing: Vitest 4 (
vitest.config.ts, separate fromvite.config.ts), Playwright (playwright.config.ts) for browser integration tests
Architecture
Chrome DevTools extension with two entry points (multi-page Vite build):
devtools.html→src/devtools.ts— Creates "CSS Noop" sidebar pane in Elements tabsidebar.html→src/sidebar/main.tsx— React app rendered inside the sidebar pane
Rules Engine (src/rules/)
Pure-function rules with zero Chrome API dependency — fully testable. Each rule file is named after its rule ID (e.g. container-no-gap.ts → rule ID container-no-gap).
Key infrastructure files:
types.ts—ElementData,Warning,Rule,RuleContext,RuleIdcontext.ts—createRuleContext()normalizes computed styles; helper predicatesstacking-context.ts—isStackingContext()detects CSS stacking context triggersengine.ts—analyzeElement()creates context then runs all registered rulesregistry.ts— rule registration via side-effect imports inengine.ts
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.
- 9d ago First seen · 219 lines · 2,862 tokens per session scan A d1d55ebae911
css-noop-checker CLAUDE.md is an instructions file published in the GitHub repository purupurupu/css-noop-checker (24 stars, last pushed 5mo ago), licensed MIT. It adds 2,862 tokens to every session, about $0.0143 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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