performance

performance is a skill for Claude Code, Codex from FlorianBruniaux/ccboard. It costs 49 tokens per session (2,398 once invoked), scanned A, a copy of performance, MIT.

A web-performance audit and optimization workflow focused on loading speed, runtime work, assets, and user-facing page measurements such as Core Web Vitals.

In plain words
What is it for?
Use it to investigate slow pages, reduce JavaScript, CSS, image, font, or third-party weight, and improve resource loading and server response time.
Why use it?
It helps identify what makes a website slow and turns those bottlenecks into specific changes that can be measured before and after.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/florianbruniaux/ccboard/performance
Any agent
npx skills add FlorianBruniaux/ccboard --skill performance
Clone the repo
git clone --depth 1 https://github.com/FlorianBruniaux/ccboard

Made for: Claude Code, Codex.

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 performance

README.md
[![agentmods](https://agentmods.dev/badge/skills/florianbruniaux/ccboard/performance.svg)](https://agentmods.dev/skills/florianbruniaux/ccboard/performance)
Your own site
<a href="https://agentmods.dev/skills/florianbruniaux/ccboard/performance"><img src="https://agentmods.dev/badge/skills/florianbruniaux/ccboard/performance.svg" alt="Measured on agentmods" height="20"></a>
Per session 49 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,398 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin 88% copy Near-identical to another mod 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 $0.00049 $0.02398
Opus 5 $0.00024 $0.01199
Sonnet 5 $0.00010 $0.00480
Haiku 4.5 $0.00005 $0.00240

Measured 3d ago against content hash 3fc1a78f1552, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

performance 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 3d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

return cached || fetch(event.request).then((response) => {
Origin

This is a copy

88% identical to performance — 192 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.claude/skills/performance/SKILL.md · 366 lines

How it starts

The opening of the file, as written. The whole thing — 366 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Performance optimization

Deep performance optimization based on Lighthouse performance audits. Focuses on loading speed, runtime efficiency, and resource optimization.

How it works

  1. Identify performance bottlenecks in code and assets
  2. Prioritize by impact on Core Web Vitals
  3. Provide specific optimizations with code examples
  4. Measure improvement with before/after metrics

Performance budget

Resource Budget Rationale
Total page weight < 1.5 MB 3G loads in ~4s
JavaScript (compressed) < 300 KB Parsing + execution time
CSS (compressed) < 100 KB Render blocking
Images (above-fold) < 500 KB LCP impact
Fonts < 100 KB FOIT/FOUT prevention
Third-party < 200 KB Uncontrolled latency

Critical rendering path

Server response

  • TTFB < 800ms. Time to First Byte should be fast. Use CDN, caching, and efficient backends.
  • Enable compression. Gzip or Brotli for text assets. Brotli preferred (15-20% smaller).
  • HTTP/2 or HTTP/3. Multiplexing reduces connection overhead.
  • Edge caching. Cache HTML at CDN edge when possible.

Resource loading

Preconnect to required origins:

<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://cdn.example.com" crossorigin>

Preload critical resources:

<!-- LCP image -->
<link rel="preload" href="/hero.webp" as="image" fetchpriority="high">

<!-- Critical font -->
<link rel="preload" href="/font.woff2" as="font" type="font/woff2" crossorigin>

Defer non-critical CSS:

<!-- Critical CSS inlined -->
<style>/* Above-fold styles */</style>

<!-- Non-critical CSS -->
<link rel="preload" href="/styles.css" as="style" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="/styles.css"></noscript>

JavaScript optimization

Defer non-essential scripts:

<!-- Parser-blocking (avoid) -->
<script src="/critical.js"></script>

<!-- Deferred (preferred) -->
<script defer src="/app.js"></script>

<!-- Async (for independent scripts) -->
<script async src="/analytics.js"></script>

<!-- Module (deferred by default) -->
<script type="module" src="/app.mjs"></script>

Read the full file on GitHub · 366 lines

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. 3d ago First seen · 366 lines · 49 tokens per session scan A 3fc1a78f1552

Subscribe to this mod's changes

performance is a skill published in the GitHub repository FlorianBruniaux/ccboard (94 stars, last pushed 2d ago), licensed MIT. It adds 49 tokens to every session and 2,398 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 88% identical to performance, differing in 192 lines, and is treated as a copy.