frontend-perf-reviewer

frontend-perf-reviewer is a skill for Claude Code, Codex from RaNDoM6913/claude-code-superkit. It costs 34 tokens per session (749 once invoked), scanned A, original, MIT.

A front-end performance review skill for checking how website code affects loading speed, rendering, and Core Web Vitals, which are browser measurements of user experience.

In plain words
What is it for?
Use it to review code splitting, tree shaking, heavy dependencies, lazy-loaded images, placeholders, image formats, and related performance practices.
Why use it?
It helps locate avoidable slowdowns such as oversized bundles, unnecessary imports, unoptimized images, and inefficient loading.

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/random6913/claude-code-superkit/frontend-perf-reviewer
Any agent
npx skills add RaNDoM6913/claude-code-superkit --skill frontend-perf-reviewer
Clone the repo
git clone --depth 1 https://github.com/RaNDoM6913/claude-code-superkit

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 frontend-perf-reviewer

README.md
[![agentmods](https://agentmods.dev/badge/skills/random6913/claude-code-superkit/frontend-perf-reviewer.svg)](https://agentmods.dev/skills/random6913/claude-code-superkit/frontend-perf-reviewer)
Your own site
<a href="https://agentmods.dev/skills/random6913/claude-code-superkit/frontend-perf-reviewer"><img src="https://agentmods.dev/badge/skills/random6913/claude-code-superkit/frontend-perf-reviewer.svg" alt="Measured on agentmods" height="20"></a>
Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 749 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found 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 $0.00034 $0.00749
Opus 5 $0.00017 $0.00375
Sonnet 5 $0.00007 $0.00150
Haiku 4.5 $0.00003 $0.00075

Measured 3d ago against content hash ccdf9827653b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-perf-reviewer 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.

packages/codex/skills/frontend-perf-reviewer/SKILL.md · 66 lines

How it starts

The opening of the file, as written. The whole thing — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Frontend Performance Reviewer

You review frontend code for performance, focusing on bundle size, rendering efficiency, and Core Web Vitals.

Before Review

Read project AGENTS.md or CLAUDE.md and package.json for framework, bundler, and dependency context.

Review Checklist (12 checks)

Bundle Size (3 checks)

# Check Severity What to look for
1 Code splitting CRITICAL Routes use dynamic import() or framework lazy loading. No single monolithic bundle
2 Tree shaking WARNING Named imports (import { x } from 'lib') not namespace (import * as lib). Barrel files re-exporting everything defeat tree shaking
3 Heavy imports WARNING Large libraries (moment, lodash full, three.js) imported in main bundle instead of code-split. Use date-fns, lodash-es, or dynamic import for 3D

Images & Media (3 checks)

# Check Severity What to look for
4 Lazy loading WARNING Images below the fold use loading="lazy" or framework Image component with lazy default
5 Placeholders INFO Large images have blur/thumbhash/skeleton placeholder during load. No layout shift
6 Format INFO Images served as WebP/AVIF where possible. PNGs for transparency only, never for photos

CSS & Rendering (3 checks)

# Check Severity What to look for
7 CSS containment INFO Complex components use contain: content or contain: layout paint. Limits browser repaint scope
8 will-change WARNING Only on elements that actually animate. will-change: transform on static elements wastes GPU memory
9 Layout thrashing CRITICAL No read-then-write DOM pattern in loops (el.offsetHeight then el.style.height). Batch reads, then writes

Runtime Performance (3 checks)

# Check Severity What to look for
10 LCP optimization CRITICAL Largest Contentful Paint element loads fast — no unnecessary JS blocking, preload critical images/fonts
11 CLS prevention WARNING Images/embeds have explicit width/height or aspect-ratio. No layout shift during load
12 INP optimization WARNING Event handlers are fast (< 200ms). Heavy work deferred to requestIdleCallback or Web Worker

Read the full file on GitHub · 66 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 · 66 lines · 34 tokens per session scan A ccdf9827653b

Subscribe to this mod's changes

frontend-perf-reviewer is a skill published in the GitHub repository RaNDoM6913/claude-code-superkit (2 stars, last pushed 1mo ago), licensed MIT. It adds 34 tokens to every session and 749 once invoked, about $0.0002 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 2026-08-31.

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