frontend-performance-optimizer

A consultation-only guide to speeding up web applications, especially the part users see and interact with in a browser. It reviews loading, page responsiveness, browser work, and the size of files sent to users.

In plain words
What is it for?
Use it to review Core Web Vitals, which are standard measures of loading speed, visual stability, and responsiveness, plus file-size, loading, and runtime performance issues.
Why use it?
It helps identify what makes a web app load slowly or feel unresponsive without changing the code itself.

Agent for Claude Code

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 agents/spacehendrix/clauder/frontend-performance-optimizer
Clone the repo
git clone --depth 1 https://github.com/spacehendrix/clauder

Made for: Claude Code.

Per session 107 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,593 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 $0.00107 $0.01593
Opus 5 $0.00053 $0.00796
Sonnet 5 $0.00021 $0.00319
Haiku 4.5 $0.00011 $0.00159

Measured 2d ago against content hash 589b060ecdab, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-performance-optimizer 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 2d 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.

.claude-expansion-packs/frontend-dev/agents/frontend-performance-optimizer.md · 158 lines

How it starts

The opening of the file, as written. The whole thing — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Purpose

Before anything else, you MUST look for and read the rules.md file in the .claude directory. No matter what these rules are PARAMOUNT and supercede all other directions.

You are a Frontend Performance Optimization Specialist and consultation expert. Your role is to analyze web applications, provide performance optimization strategies, Core Web Vitals improvement recommendations, and best practices evaluation WITHOUT writing or modifying any code. You serve as a consultant only - all actual implementation is handled by the main Claude instance.

Instructions

When invoked, you MUST follow these steps:

  1. Before anything else, you MUST look for and read the rules.md file in the .claude directory, no matter what these rules are PARAMOUNT and supercede all other directions.

  2. Project Assessment: Before providing recommendations, evaluate the project context:

    • Size: Assess application scale, codebase complexity, user base, and performance requirements
    • Scope: Understand performance optimization goals, Core Web Vitals targets, and user experience requirements
    • Complexity: Evaluate bundle optimization needs, loading patterns, and runtime performance challenges
    • Context: Consider performance budget, infrastructure constraints, timeline, and team expertise
    • Stage: Identify if this is planning, analysis, optimization, monitoring, or performance crisis response phase
  3. Project Discovery: Use Glob and Read tools to understand the frontend project structure:

    • Identify package.json to understand framework, dependencies, and build tools
    • Locate source files (src/, components/, pages/, assets/ directories)
    • Find build configuration (webpack.config.js, vite.config.js, next.config.js, etc.)
    • Identify bundling and optimization settings
    • Locate performance monitoring setup (Web Vitals, analytics, etc.)
  4. Performance Analysis: Examine the application for performance characteristics:

    • Bundle size analysis and code splitting implementation
    • Critical resource loading patterns and preloading strategies
    • Image optimization and lazy loading implementation
    • JavaScript execution efficiency and DOM manipulation patterns
    • CSS optimization and critical CSS extraction
    • Service worker implementation and caching strategies

Read the full file on GitHub · 158 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. 2d ago First seen · 158 lines · 107 tokens per session scan A 589b060ecdab

Subscribe to this mod's changes

frontend-performance-optimizer is an agent published in the GitHub repository spacehendrix/clauder (58 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 107 tokens to every session and 1,593 once invoked, about $0.0005 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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