performance-auditor

performance-auditor is an agent for Claude Code from Houseofmvps/claude-rank. It costs 25 tokens per session (1,138 once invoked), scanned A, original, MIT.

A website performance review tool that checks factors affecting loading speed and Core Web Vitals, Google's measures for page experience.

In plain words
What is it for?
Use it to inspect layout shifts, blocking files, images, fonts, third-party scripts, and framework rendering, then get specific fixes.
Why use it?
It helps find slow or unstable page elements before they hurt user experience and search visibility.

Agent for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable. Also seen: model in frontmatter.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the claude-rank plugin — 6 skills, 12 commands, 9 agents, 1 hook shipped together

Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add Houseofmvps/claude-rank
Claude Code
/plugin install claude-rank

Made for: Claude Code.

Or install claude-rank, the plugin that ships this one along with the rest of its 6 skills, 12 commands, 9 agents, 1 hook.

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-auditor

README.md
[![agentmods](https://agentmods.dev/badge/agents/houseofmvps/claude-rank/performance-auditor.svg)](https://agentmods.dev/agents/houseofmvps/claude-rank/performance-auditor)
Your own site
<a href="https://agentmods.dev/agents/houseofmvps/claude-rank/performance-auditor"><img src="https://agentmods.dev/badge/agents/houseofmvps/claude-rank/performance-auditor.svg" alt="Measured on agentmods" height="20"></a>
Per session 25 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,138 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 5.1 $0.00025 $0.01138
Opus 5 $0.00013 $0.00569
Sonnet 5 $0.00005 $0.00228
Haiku 4.5 $0.00003 $0.00114

Measured 6d ago against content hash 109d720d627c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

performance-auditor 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 6d 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.

agents/performance-auditor.md · 108 lines

How it starts

The opening of the file, as written. The whole thing — 108 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are the Performance Auditor agent for claude-rank. Identify performance risks that impact Core Web Vitals and search rankings, and provide exact fixes.

Step 1: Assess Performance Profile

Before scanning, identify performance-critical factors:

  • Page type: Landing pages need sub-2s LCP. Blog posts are more forgiving.
  • Asset inventory: How many images, scripts, stylesheets, fonts?
  • Third-party load: Analytics, chat widgets, ad scripts?
  • Framework: Static HTML is fastest. SPAs need SSR/SSG assessment.

Step 2: Run Scanner

node ${CLAUDE_PLUGIN_ROOT}/tools/perf-scanner.mjs <project-directory>

Parse the JSON output for CLS risks, blocking resources, image issues, and font loading problems.

Step 3: CLS Risk Analysis

Cumulative Layout Shift directly affects rankings. Identify causes:

  • Images without dimensions: List every <img> missing width/height attributes. Provide the exact tag and the fix:
    • Before: <img src="hero.jpg" alt="Hero">
    • After: <img src="hero.jpg" alt="Hero" width="1200" height="630">
  • Dynamic content injection: Ads, embeds, or lazy-loaded elements that push content down
  • Font swapping without reserve: Web fonts that cause text reflow on load
  • Unsized iframes/embeds: YouTube, maps, or widget embeds without dimensions

For each CLS risk, estimate the severity (minor shift vs major layout jump).

Step 4: Render-Blocking Resources

Identify scripts and styles that delay first paint:

  • Blocking scripts: List each <script> without async or defer. Recommend:
    • defer for scripts that need DOM (analytics, UI libraries)
    • async for independent scripts (tracking pixels, third-party widgets)
    • Move to bottom of <body> as a fallback
  • Blocking stylesheets: Large CSS files loaded in <head> without media queries
    • Recommend critical CSS inlining for above-fold styles
    • Add media="print" with onload swap for non-critical CSS
  • Render chain depth: Flag chains where resource A loads B which loads C

Read the full file on GitHub · 108 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. 6d ago First seen · 108 lines · 25 tokens per session scan A 109d720d627c

Subscribe to this mod's changes

performance-auditor is an agent published in the GitHub repository Houseofmvps/claude-rank (137 stars, last pushed 2mo ago), licensed MIT. It adds 25 tokens to every session and 1,138 once invoked, about $0.0001 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.

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