perf-audit

perf-audit is a skill for Claude Code from helderberto/agent-skills. It costs 81 tokens per session (522 once invoked), scanned A, original, MIT.

A frontend performance checker that examines the files produced by a production build. It reports file sizes, possible heavy packages, and where the bundle’s size comes from.

In plain words
What is it for?
Use it to audit frontend performance, check bundle size, identify performance bottlenecks, and review the size impact of packages or modules.
Why use it?
It helps find code that makes a website download or start more slowly, without needing to inspect the application manually or run a browser.

Skill for Claude Code

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

Part of the hb plugin — 38 skills, 6 agents shipped together

Good fit Use it to audit frontend performance, check bundle size, identify performance bottlenecks…

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/helderberto/agent-skills/perf-audit
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 helderberto/agent-skills --skill perf-audit
Clone the repo
git clone --depth 1 https://github.com/helderberto/agent-skills

Made for: Claude Code.

Or install hb, the plugin that ships this one along with the rest of its 38 skills, 6 agents.

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 perf-audit

README.md
[![agentmods](https://agentmods.dev/badge/skills/helderberto/agent-skills/perf-audit.svg)](https://agentmods.dev/skills/helderberto/agent-skills/perf-audit)
Your own site
<a href="https://agentmods.dev/skills/helderberto/agent-skills/perf-audit"><img src="https://agentmods.dev/badge/skills/helderberto/agent-skills/perf-audit.svg" alt="Measured on agentmods" height="20"></a>
Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 522 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00081 $0.00522
Opus 5 $0.00041 $0.00261
Sonnet 5 $0.00016 $0.00104
Haiku 4.5 $0.00008 $0.00052

Measured 3d ago against content hash 84ea7fab0ec6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

perf-audit 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.

skills/perf-audit/SKILL.md · 41 lines

What it actually says

Performance Audit

Workflow

  1. Detect build tool from package.json (vite, webpack, next, rollup)

  2. Run the production build via the project's task runner (auto-detect from package.json).

  3. Analyze the build output — non-interactive only. Never launch a browser or a long-running server in an audit; those hang an automated run. Prefer, in order:

    • Measure the emitted files directly: for each file in the output dir (e.g. dist/assets/*.js), report raw + gzipped size — gzip -c <file> | wc -c. This always works and needs no extra tooling.
    • Per-module breakdown, as a static artifact (not a server):
      • Vite/Rollup: npx source-map-explorer 'dist/assets/*.js', or add rollup-plugin-visualizer configured to emit JSON/HTML to a file
      • webpack/Next.js: npx webpack-bundle-analyzer -m static -r report.html <stats-file> (writes a file; do not use the default server mode)
    • npx vite-bundle-visualizer opens a browser and blocks — only suggest it to the user for manual exploration; do not run it here.
  4. Check package.json for known heavy packages

  5. Report findings with size impact

Compare against standard industry thresholds; report gzipped sizes.

Output format

  • Bundle summary: total size / gzipped size vs budget
  • Large chunks: name + size + % of total
  • Heavy deps: package + size + lighter alternative
  • Quick wins: sorted by estimated savings

Rules

  • Report gzipped sizes (what the browser downloads)
  • Never auto-change dependencies -- report and suggest only

Error Handling

  • Build fails -- report the error and stop; fix build issues before auditing
  • No build output found -- run production build first
  • Build tool unrecognized -- fall back to scanning package.json for heavy packages only
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 Changed · +19 tokens per session 84ea7fab0ec6
  2. 7d ago First seen · 41 lines · 62 tokens per session scan A 86033bc57ae5

Subscribe to this mod's changes

perf-audit is a skill published in the GitHub repository helderberto/agent-skills (14 stars, last pushed 5d ago), licensed MIT. It adds 81 tokens to every session and 522 once invoked, about $0.0004 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 2026-08-30.

Related

Other skills, from other repositories

accessibility-a11y

WCAG 2.2 compliance, ARIA patterns, keyboard navigation, screen readers, automated testing.

travisjneuman/.claude · 26 tokens

flutter-development

Cross-platform development with Flutter and Dart for iOS, Android, Web, Desktop, and embedded. Use when building Flutter apps, implementing Material/Cupertino design, or optimizing Dart code.

travisjneuman/.claude · 41 tokens

electron-desktop

Desktop application development with Electron for Windows, macOS, and Linux. Use when building cross-platform desktop apps, implementing native OS features, or packaging web apps for desktop.

travisjneuman/.claude · 38 tokens

generic-react-ux-designer

Professional UI/UX design expertise for React applications. Covers design thinking, user psychology (Hick's/Fitts's/Jakob's Law), visual hierarchy, interaction patterns, accessibility, performance-driven design, and design critique. Use when designing features, improving UX, solving user problems, or conducting design…

travisjneuman/.claude · 69 tokens

generic-react-feature-developer

Guide feature development for React applications with architecture focus. Covers Zustand/Redux patterns, IndexedDB usage, component systems, lazy loading strategies, and seamless integration. Use when adding new features, refactoring existing code, or planning major changes.

travisjneuman/.claude · 53 tokens

frontend-enhancer

This skill should be used when enhancing the visual design and aesthetics of web applications. It provides modern UI components, design patterns, color palettes, animations, and layout templates. REQUIRES ui-research skill first. Use this skill for tasks like improving styling, creating responsive designs…

travisjneuman/.claude · 79 tokens