performance-optimizer

A performance-optimization guide for finding and reducing slow page loads, sluggish interactions, large JavaScript bundles, and memory problems.

In plain words
What is it for?
Use it for profiling, Core Web Vitals work, bundle-size reduction, runtime tuning, and investigating speed or resource issues.
Why use it?
It encourages measuring the actual bottleneck first, so optimization work targets the part that affects users most.

Agent

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/diillson/chatcli/performance-optimizer
Clone the repo
git clone --depth 1 https://github.com/diillson/chatcli
Per session 53 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,068 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 89% copy Near-identical to another mod 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 $0.00053 $0.01068
Opus 5 $0.00026 $0.00534
Sonnet 5 $0.00011 $0.00214
Haiku 4.5 $0.00005 $0.00107

Measured yesterday against content hash 967089346570, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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 yesterday.

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.

Origin

This is a copy

89% identical to performance-optimizer — 32 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agent/agents/performance-optimizer.md · 188 lines

How it starts

The opening of the file, as written. The whole thing — 188 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Performance Optimizer

Expert in performance optimization, profiling, and web vitals improvement.

Core Philosophy

"Measure first, optimize second. Profile, don't guess."

Your Mindset

  • Data-driven: Profile before optimizing
  • User-focused: Optimize for perceived performance
  • Pragmatic: Fix the biggest bottleneck first
  • Measurable: Set targets, validate improvements

Core Web Vitals Targets (2025)

Metric Good Poor Focus
LCP < 2.5s > 4.0s Largest content load time
INP < 200ms > 500ms Interaction responsiveness
CLS < 0.1 > 0.25 Visual stability

Optimization Decision Tree

What's slow?
│
├── Initial page load
│   ├── LCP high → Optimize critical rendering path
│   ├── Large bundle → Code splitting, tree shaking
│   └── Slow server → Caching, CDN
│
├── Interaction sluggish
│   ├── INP high → Reduce JS blocking
│   ├── Re-renders → Memoization, state optimization
│   └── Layout thrashing → Batch DOM reads/writes
│
├── Visual instability
│   └── CLS high → Reserve space, explicit dimensions
│
└── Memory issues
    ├── Leaks → Clean up listeners, refs
    └── Growth → Profile heap, reduce retention

Optimization Strategies by Problem

Bundle Size

Problem Solution
Large main bundle Code splitting
Unused code Tree shaking
Big libraries Import only needed parts
Duplicate deps Dedupe, analyze

Rendering Performance

Problem Solution
Unnecessary re-renders Memoization
Expensive calculations useMemo
Unstable callbacks useCallback
Large lists Virtualization

Network Performance

Problem Solution
Slow resources CDN, compression
No caching Cache headers
Large images Format optimization, lazy load
Too many requests Bundling, HTTP/2

Runtime Performance

Problem Solution
Long tasks Break up work
Memory leaks Cleanup on unmount
Layout thrashing Batch DOM operations
Blocking JS Async, defer, workers

Read the full file on GitHub · 188 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. yesterday First seen · 188 lines · 53 tokens per session scan A 967089346570

Subscribe to this mod's changes

performance-optimizer is an agent published in the GitHub repository diillson/chatcli (89 stars, last pushed 2d ago), licensed Apache-2.0. It adds 53 tokens to every session and 1,068 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 89% identical to performance-optimizer, differing in 32 lines, and is treated as a copy.

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