optimize

A guide for finding and fixing interface performance problems, such as slow loading, expensive animations, large files, or inefficient images and code.

In plain words
What is it for?
Use it to investigate Core Web Vitals, loading and rendering delays, bundle and image size, animation smoothness, memory use, and network requests.
Why use it?
It replaces guesswork with measurements of speed, responsiveness, resource use, and network activity before and after changes.

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/lanesket/llm.log/optimize
Any agent
npx skills add lanesket/llm.log --skill optimize
Clone the repo
git clone --depth 1 https://github.com/lanesket/llm.log

Made for: Claude Code, Codex.

Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,868 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 95% 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 $0.00026 $0.01868
Opus 5 $0.00013 $0.00934
Sonnet 5 $0.00005 $0.00374
Haiku 4.5 $0.00003 $0.00187

Measured 3d ago against content hash f9400a9dde1f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

optimize 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 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.

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.

Origin

This is a copy

95% identical to optimize — 2 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.

.agents/skills/optimize/SKILL.md · 268 lines

How it starts

The opening of the file, as written. The whole thing — 268 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Identify and fix performance issues to create faster, smoother user experiences.

Assess Performance Issues

Understand current performance and identify problems:

  1. Measure current state:

    • Core Web Vitals: LCP, FID/INP, CLS scores
    • Load time: Time to interactive, first contentful paint
    • Bundle size: JavaScript, CSS, image sizes
    • Runtime performance: Frame rate, memory usage, CPU usage
    • Network: Request count, payload sizes, waterfall
  2. Identify bottlenecks:

    • What's slow? (Initial load? Interactions? Animations?)
    • What's causing it? (Large images? Expensive JavaScript? Layout thrashing?)
    • How bad is it? (Perceivable? Annoying? Blocking?)
    • Who's affected? (All users? Mobile only? Slow connections?)

CRITICAL: Measure before and after. Premature optimization wastes time. Optimize what actually matters.

Optimization Strategy

Create systematic improvement plan:

Loading Performance

Optimize Images:

  • Use modern formats (WebP, AVIF)
  • Proper sizing (don't load 3000px image for 300px display)
  • Lazy loading for below-fold images
  • Responsive images (srcset, picture element)
  • Compress images (80-85% quality is usually imperceptible)
  • Use CDN for faster delivery
<img 
  src="hero.webp"
  srcset="hero-400.webp 400w, hero-800.webp 800w, hero-1200.webp 1200w"
  sizes="(max-width: 400px) 400px, (max-width: 800px) 800px, 1200px"
  loading="lazy"
  alt="Hero image"
/>

Reduce JavaScript Bundle:

  • Code splitting (route-based, component-based)
  • Tree shaking (remove unused code)
  • Remove unused dependencies
  • Lazy load non-critical code
  • Use dynamic imports for large components
// Lazy load heavy component
const HeavyChart = lazy(() => import('./HeavyChart'));

Optimize CSS:

  • Remove unused CSS
  • Critical CSS inline, rest async
  • Minimize CSS files
  • Use CSS containment for independent regions

Optimize Fonts:

  • Use font-display: swap or optional
  • Subset fonts (only characters you need)
  • Preload critical fonts
  • Use system fonts when appropriate
  • Limit font weights loaded

Read the full file on GitHub · 268 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 · 268 lines · 26 tokens per session scan A f9400a9dde1f

Subscribe to this mod's changes

optimize is a skill published in the GitHub repository lanesket/llm.log (22 stars, last pushed 5mo ago), licensed MIT. It adds 26 tokens to every session and 1,868 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 95% identical to optimize, differing in 2 lines, and is treated as a copy.

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