performance

performance is a skill for Claude Code from shennawardana23/skillme. It costs 88 tokens per session (2,983 once invoked), scanned A, a copy of performance, Apache-2.0.

A guide to improving website loading speed, code execution, and asset use, based on Lighthouse audits. Lighthouse is a tool that measures web-page performance and user experience.

In plain words
What is it for?
Auditing page speed, reducing JavaScript, CSS, image, font, and third-party resource costs, and improving Core Web Vitals.
Why use it?
It helps identify what is actually slowing a site down and prioritise changes that improve loading and interaction.

Skill for Claude Code

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

Part of the skillme plugin — 137 skills, 2 commands shipped together

Good fit Auditing page speed, reducing JavaScript, CSS, image, font, and third-party resource costs, and improving Core Web Vitals.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/shennawardana23/skillme/performance
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 shennawardana23/skillme --skill performance
Clone the repo
git clone --depth 1 https://github.com/shennawardana23/skillme

Made for: Claude Code.

Or install skillme, the plugin that ships this one along with the rest of its 137 skills, 2 commands.

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/shennawardana23/skillme/performance/github.svg)](https://agentmods.dev/skills/shennawardana23/skillme/performance)
Your own site
<a href="https://agentmods.dev/skills/shennawardana23/skillme/performance"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/performance/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 performance

Your own site · 80×15
<a href="https://agentmods.dev/skills/shennawardana23/skillme/performance"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 88 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,983 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin 84% 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 5.1 $0.00088 $0.02983
Opus 5 $0.00044 $0.01491
Sonnet 5 $0.00018 $0.00597
Haiku 4.5 $0.00009 $0.00298

Measured 5d ago against content hash 05f3eb6a1c2f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, 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 5d 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

84% identical to performance — 235 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.

skills/performance/SKILL.md · 401 lines

How it starts

The opening of the file, as written. The whole thing — 401 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.
  • Send Early Hints (HTTP 103) for slow origins. When the origin needs hundreds of milliseconds to assemble the final response, return a 103 Early Hints with Link: </hero.webp>; rel=preload; as=image (and similar for critical CSS/fonts) so the browser starts fetching before the 200 OK lands. Cloudflare reports 20–30% LCP improvements on image-heavy pages. Requires HTTP/2+ and is supported by Chromium-based browsers; other browsers ignore the 103 and fall through to the 200 — safe to enable. CDNs (Cloudflare, Fastly, Akamai) can synthesize 103s automatically from prior responses; on your own origin, emit them from the same handler that issues the 200.

Resource loading

Preconnect to required origins:

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

Read the full file on GitHub · 401 lines

Files

What ships with it

1 file 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 First seen · 401 lines · 88 tokens per session scan A 05f3eb6a1c2f

Subscribe to this mod's changes

performance is a skill published in the GitHub repository shennawardana23/skillme (2 stars, last pushed 11d ago), licensed Apache-2.0. It adds 88 tokens to every session and 2,983 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 84% identical to performance, differing in 235 lines, and is treated as a copy.

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