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Agent skill

Perf Audit

by Houseofmvps in Houseofmvps/ultraship

Run Lighthouse performance audit with auto-fix for common issues.

MITAuto-check: notesFrontend & Design

Install Perf Audit

skills CLI
$ npx skills add Houseofmvps/ultraship --skill perf-audit -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install Houseofmvps/ultraship perf-audit --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/Houseofmvps/ultraship.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/perf-audit .claude/skills/perf-audit && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
perf-audit
GitHub stars
123
Token cost
~945 tokens
SKILL.md length
448 words
Files
1
Skills in repo
28
Repo updated
First seen
Licence
MIT

At a glance

Run Lighthouse performance audit with auto-fix for common issues.

  • Works in 6 steps: Find the URL → Run Lighthouse → Report Scores & Core Web Vitals → …
  • User wants to check
  • SKILL.md covers Process and Key Principle
  • Calls node

What it does

Perf Audit is an agent skill from Houseofmvps/ultraship. Run Lighthouse performance audit with auto-fix for common issues. Use when user wants to check or improve site performance.

Its SKILL.md is about 950 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Frontend & Design, covering Web performance. The repository describes itself as: "ULTRASHIP" Claude Code plugin — 39 skills, 33 tools, 11 agents for ship-ready workflows: planning, review, pentesting, safety guardrails, canary monitoring, SEO/AI-readiness… The licence is MIT.

When your agent uses it

  • User wants to check
  • Improve site performance

Example prompts

  • “/perf-audit”

Requirements

  • Pre-approved tools (allowed-tools): Bash, Read, Edit, Grep, Glob

Workflow steps

6 steps, taken from the step headings in SKILL.md.

  1. Find the URL
  2. Run Lighthouse
  3. Report Scores & Core Web Vitals
  4. Identify Root Causes
  5. Apply Fixes
  6. Graceful Degradation

What it can do on your machine

Read from SKILL.md and the folder at commit ed232cb. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • Bash
    • Read
    • Edit
    • Grep
    • Glob

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • node

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Perf Audit loads about 945 tokens when it runs. Until then it costs about 34 tokens; SKILL.md has 448 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~34
When it runs · the whole SKILL.md, loaded when a task matches
~945

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check: notes

The automated check noted patterns worth knowing about, such as sudo or a known installer.

  • NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
    allowed-tools: Bash, Read, Edit, Grep, Glob

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Houseofmvps/ultraship at commit ed232cb, republished under its MIT licence (© Houseofmvps). 448 words, ~945 tokens.

Download SKILL.mdSave it as .claude/skills/perf-audit/SKILL.md (or your agent's skills folder).
name
perf-audit
description
Run Lighthouse performance audit with auto-fix for common issues. Use when user wants to check or improve site performance.
allowed-tools
Bash, Read, Edit, Grep, Glob
argument-hint
<url>

Performance Audit

Run Lighthouse against the project and fix performance issues.

Process

Step 1: Find the URL
  • Check if dev server is running (try common ports: 3000, 5173, 4321, 8080)
  • Check package.json scripts for dev/start commands
  • Ask user for URL if not auto-detected
  • If no server running, suggest starting one first
Step 2: Run Lighthouse
bash
node ${CLAUDE_PLUGIN_ROOT}/tools/lighthouse-runner.mjs <url>

Parse JSON output for scores and opportunities.

Step 3: Report Scores & Core Web Vitals

Present all four Lighthouse scores:

  • Performance (target 90+)
  • Accessibility (target 90+)
  • Best Practices (target 90+)
  • SEO (target 100)

Report Core Web Vitals with targets:

  • LCP (Largest Contentful Paint): target <2.5s — report the LCP element from lcp_element
  • TBT (Total Blocking Time): target <200ms — proxy for INP
  • CLS (Cumulative Layout Shift): target <0.1
  • FCP (First Contentful Paint): target <1.8s
  • SI (Speed Index): target <3.4s
Step 4: Identify Root Causes

Before fixing, identify what's actually causing problems:

LCP too high? Check lcp_element in results — fix THAT specific element:

  • If it's an <img>: preload it, use WebP, add fetchpriority="high"
  • If it's text: check web font loading, add font-display: swap
  • If it's a background image: preload via <link rel="preload">

CLS too high? Check diagnostics for layout shift sources:

  • Images without width/height → add dimensions (scanner already checks this)
  • Dynamic content injected above fold → reserve space with CSS
  • Web fonts causing FOUT → add font-display: optional or swap

Unused resources? Check wasted_resources:

  • unused_js_kb > 100KB → code splitting or tree shaking needed
  • unused_css_kb > 50KB → purge unused CSS (PurgeCSS, Tailwind purge)

Third-party scripts slow? Check third_party_impact:

  • Analytics blocking >100ms → defer/async load
  • Ad scripts blocking >200ms → lazy load below fold
  • Chat widgets → load on user interaction, not page load
Show full SKILL.md (182 more words)Show less
Step 5: Apply Fixes

For each opportunity, apply fixes using Edit tool:

Performance fixes (high impact first):

  • Render-blocking resources → add defer or async to non-critical scripts
  • Unused JavaScript → recommend code splitting, dynamic imports, tree shaking
  • Unused CSS → recommend PurgeCSS or Tailwind purge config
  • LCP image not preloaded → add <link rel="preload" as="image" href="...">
  • Images not lazy-loaded → add loading="lazy" to below-fold images
  • Images without dimensions → add width and height attributes
  • No preconnect → add <link rel="preconnect" href="..."> for external origins
  • Font display → add font-display: swap to @font-face declarations
  • Third-party scripts → defer non-essential scripts, lazy load on interaction

Accessibility fixes:

  • Missing alt text (also caught by SEO scanner)
  • Missing form labels → add <label> elements
  • Low contrast → adjust colors
  • Missing landmark regions → add <main>, <nav>, <footer>
Step 6: Graceful Degradation
  • No Chrome: report "Chrome needed for Lighthouse. Install Chrome or Chromium."
  • Lighthouse timeout: return partial results with warning
  • No dev server: suggest starting one, or test against production URL

Key Principle

Fix, don't just audit. Identify the specific elements causing problems. Apply every automated fix possible. For build-tool changes (code splitting, tree shaking), provide exact config recommendations.

© Houseofmvps, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/perf-audit of Houseofmvps/ultraship.

Open the folder on GitHubat commit ed232cb

Compare with similar skills

Perf Audit next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Perf Audit compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Perf Audit this skillHouseofmvps/ultraship123—~945Automated safety check: NotesMIT
React Doctormakeplane/plane61k12 repos~657Automated safety check: PassAGPL-3.0
Fixing Motion Performanceibelick/ui-skills9.5k5 repos~1.4kAutomated safety check: PassMIT
GSAP Performance Tuninggreensock/gsap-skills16k4 repos~1kAutomated safety check: PassMIT
React Frontend Development Guidelinesdiet103/claude-code-infrastructure-showcase10k2 repos~2.9kAutomated safety check: PassMIT
Web Quality Auditaddyosmani/web-quality-skills2.9k—~2.6kAutomated safety check: PassMIT

Similar skills

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    61k GitHub starsUsed in 12 repos~657 tokens
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  • Fixing Motion Performance

    ibelick/ui-skills

    Audits and fixes web animation performance: layout thrashing, work that belongs on the compositor, scroll-linked motion and costly blur effects.

    9.5k GitHub starsUsed in 5 repos~1.4k tokens
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    10k GitHub starsUsed in 2 repos~2.9k tokens
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    2.9k GitHub stars~2.6k tokensUpdated 1 mo ago
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Categories

Questions about Perf Audit

What does Perf Audit do?

Run Lighthouse performance audit with auto-fix for common issues. Perf Audit is an agent skill from Houseofmvps/ultraship. Run Lighthouse performance audit with auto-fix for common issues.

When should I use Perf Audit?

Perf Audit fits situations like: user wants to check; improve site performance.

How do I install Perf Audit in Claude Code?

Run `npx skills add Houseofmvps/ultraship --skill perf-audit -a claude-code`. Or copy the skill folder (skills/perf-audit in Houseofmvps/ultraship) into .claude/skills/perf-audit in your project. Claude Code loads it when a task matches its description.

How do I install Perf Audit in Codex?

Run `npx skills add Houseofmvps/ultraship --skill perf-audit -a codex`. Or copy the skill folder (skills/perf-audit in Houseofmvps/ultraship) into .agents/skills/perf-audit in your project. Codex loads it when a task matches its description.

Can I use Perf Audit in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add Houseofmvps/ultraship --skill perf-audit -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/perf-audit, .gemini/skills/perf-audit, .github/skills/perf-audit and .opencode/skills/perf-audit in your project.

What does Perf Audit need to run?

Going by SKILL.md and its folder, Perf Audit needs the command-line tools its instructions call (node). Its frontmatter pre-approves these tools: Bash, Read, Edit, Grep, Glob.

Does Perf Audit access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Perf Audit safe to install?

Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.

What licence does Perf Audit use?

Perf Audit is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Perf Audit use?

About 945 tokens (SKILL.md is roughly 3.8k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Perf Audit?

Skills that share tags, products or a category with Perf Audit: React Doctor (makeplane/plane, 61k stars), Fixing Motion Performance (ibelick/ui-skills, 9.5k stars), GSAP Performance Tuning (greensock/gsap-skills, 16k stars) and React Frontend Development Guidelines (diet103/claude-code-infrastructure-showcase, 10k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Perf Audit?

Houseofmvps (a GitHub user) maintains it in Houseofmvps/ultraship, which has 123 GitHub stars. The repository holds 28 skills in this directory. The repository was last updated on July 8, 2026.

Source: Houseofmvps/ultraship on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.