Borrowing it
Nothing to install: this file belongs to jantimon/web-performance-debugger. 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/jantimon/web-performance-debugger/main/CLAUDE.mdgit clone --depth 1 https://github.com/jantimon/web-performance-debuggerWrote 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/jantimon/web-performance-debugger/claude-md)<a href="https://agentmods.dev/instructions/jantimon/web-performance-debugger/claude-md"><img src="https://agentmods.dev/badge/instructions/jantimon/web-performance-debugger/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/jantimon/web-performance-debugger/claude-md"><img src="https://agentmods.dev/badge/instructions/jantimon/web-performance-debugger/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 | $0.11255 | $0.11255 |
| Opus 5.5 | $0.04502 | $0.04502 |
| Sonnet 5.5 | $0.02251 | $0.02251 |
| Haiku 4.5 | $0.01125 | $0.01125 |
Grade C, and why
web-performance-debugger CLAUDE.md scanned grade C 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 2mo 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.
Recursive force deletehighDestructive command
rm -rf with a variable or a broad path is one typo away from removing the wrong tree.
- Per the user's global rule: use `trash`, never `rm -rf`. How it starts
The opening of the file, as written. The whole thing — 532 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.
What this is
wpd (package @jantimon/web-performance-debugger, bins wpd / web-performance-debugger) is a
TypeScript CLI that drives Chrome or Firefox via Puppeteer to attribute layout/paint/style/
invalidation work back to source lines, plus CPU sampling (on by default) that attributes
self-time to source/package. One user-facing axis picks where it runs: --target chrome|firefox|node.
Trust tiers, keep them straight: counts (trace-derived, windowed to the renderer main thread) are
exact; slice ms on a --breakdown bar and wall/INP are wall-tier directional (trace
base::TimeTicks / Chrome-clamped performance.now()); CPU self-time comes from the profiler's
own microsecond clock (not performance.now()), so its ms are a real signal, trustworthy in
aggregate (sampling noise ~few %). So it is not a wall-clock benchmark runner, but it is the right
tool for comparing JS cost (e.g. SSR renderToString lanes).
selfMs is not "pure JS" on the browser lanes. It is JS plus the synchronous engine work JS
triggered: a forced layout lands as self-time on the line that forced it (measured: ~85% of the
forced-layout probe's "JS" self-time is reflow). Only --target node (no DOM) measures pure JS.
This is a feature — it prices "delete this line" — but do not describe it as pure JS.
Read README.md for the user-facing surface; this file is the internal map; docs/dev/ holds the
measured facts behind the non-obvious choices (index) and is the first stop
before changing the capture modes, the Gecko converter, or any cross-engine claim.
Commands
npm run build # tsc -> dist/ (ESM, NodeNext)
npm test # unit only (pretest builds first); pure functions, no browser
npm run test:e2e # e2e: drives the real CLI against headless Chrome (record -> query)
npm run lint # oxlint src test scripts examples (lint:fix to autofix)
npm run format # oxfmt --write (format:check to verify; config in .oxfmtrc.json, ~prettier)
npm run knip # dead exports/files/deps (config knip.json); a fresh dead export fails it
node dist/cli.js <...> # run the CLI (installed bins: web-performance-debugger, wpd)
npm run changeset # add a changeset; CI Release workflow versions+publishes on merge to main
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.
- 2mo ago First seen · 532 lines · 11,255 tokens per session scan C 252c705f010a
web-performance-debugger CLAUDE.md is an instructions file published in the GitHub repository jantimon/web-performance-debugger (31 stars, last pushed 1mo ago), licensed MIT. It adds 11,255 tokens to every session, about $0.0450 per session on Opus 5.5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-01.
web-performance-debugger CLAUDE.md compared with instructions from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| web-performance-debugger CLAUDE.mdjantimon/web-performance-debugger | Instructions file | 31 | 1mo ago | MIT | C | 11,255 | Claude Code |
| vscode buildNext.instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 9,719 | GitHub Copilot |
| next.js AGENTS.mdvercel/next.js | Instructions file | 143k | today | MIT | A | 7,461 | Codex, OpenCode |
| langchain AGENTS.mdlangchain-ai/langchain | Instructions file | 149k | yesterday | MIT | A | 4,680 | Codex, OpenCode |
| vscode oss-third-party-notices.instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 5,516 | GitHub Copilot |
| vscode copilot-instructions.mdmicrosoft/vscode | Instructions file | 195k | yesterday | MIT | A | 3,093 | GitHub Copilot |
| deepseek-harness AGENTS.mddeepseek-ai/deepseek-harness | Instructions file | 274k | 2d ago | MIT | A | 4,313 | Codex, OpenCode |