performance-profiling

A guide to measuring how quickly and efficiently a website or application runs, then finding what slows it down.

In plain words
What is it for?
Use it to check page loading, user interaction, layout movement, bundle size, runtime speed, memory use, and network activity.
Why use it?
It replaces guesses about performance with measurements that show where the actual bottleneck is.

Skill for Claude CodeCodex

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 skills/frogobox/frogo-sdk/performance-profiling
Any agent
npx skills add frogobox/frogo-sdk --skill performance-profiling
Clone the repo
git clone --depth 1 https://github.com/frogobox/frogo-sdk

Made for: Claude Code, Codex.

Per session 17 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 845 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 81% 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 $0.00017 $0.00845
Opus 5 $0.00009 $0.00423
Sonnet 5 $0.00003 $0.00169
Haiku 4.5 $0.00002 $0.00085

Measured 3d ago against content hash 0da78d260358, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

performance-profiling 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.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/lighthouse_audit.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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

81% identical to performance-profiling — 16 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.

.agents/skills/performance-profiling/SKILL.md · 154 lines

How it starts

The opening of the file, as written. The whole thing — 154 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Performance Profiling

Measure, analyze, optimize - in that order.

🔧 Runtime Scripts

Execute these for automated profiling:

Script Purpose Usage
scripts/lighthouse_audit.py Lighthouse performance audit python scripts/lighthouse_audit.py https://example.com

1. Core Web Vitals

Targets

Metric Good Poor Measures
LCP < 2.5s > 4.0s Loading
INP < 200ms > 500ms Interactivity
CLS < 0.1 > 0.25 Stability

When to Measure

Stage Tool
Development Local Lighthouse
CI/CD Lighthouse CI
Production RUM (Real User Monitoring)

2. Profiling Workflow

The 4-Step Process

1. BASELINE → Measure current state
2. IDENTIFY → Find the bottleneck
3. FIX → Make targeted change
4. VALIDATE → Confirm improvement

Profiling Tool Selection

Problem Tool
Page load Lighthouse
Bundle size Bundle analyzer
Runtime DevTools Performance
Memory DevTools Memory
Network DevTools Network

3. Bundle Analysis

What to Look For

Issue Indicator
Large dependencies Top of bundle
Duplicate code Multiple chunks
Unused code Low coverage
Missing splits Single large chunk

Optimization Actions

Finding Action
Big library Import specific modules
Duplicate deps Dedupe, update versions
Route in main Code split
Unused exports Tree shake

4. Runtime Profiling

Performance Tab Analysis

Pattern Meaning
Long tasks (>50ms) UI blocking
Many small tasks Possible batching opportunity
Layout/paint Rendering bottleneck
Script JavaScript execution

Memory Tab Analysis

Pattern Meaning
Growing heap Possible leak
Large retained Check references
Detached DOM Not cleaned up

Read the full file on GitHub · 154 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 First seen · 154 lines · 17 tokens per session scan A 0da78d260358

Subscribe to this mod's changes

performance-profiling is a skill published in the GitHub repository frogobox/frogo-sdk (21 stars, last pushed 3d ago), licensed Apache-2.0. It adds 17 tokens to every session and 845 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 81% identical to performance-profiling, differing in 16 lines, and is treated as a copy.

Related

Other skills, from other repositories

evergreen

Evergreen CI infrastructure, configuration validation. Use when modifying .evergreen/ config, preparing to submit changes or understanding the Evergreen test matrix.

mongodb/mongo-java-driver · 31 tokens

gradle-expert

Build optimization, dependency resolution, and multi-module KMP troubleshooting for AmethystMultiplatform. Use when working with: (1) Gradle build files (build.gradle.kts, settings.gradle), (2) Version catalog (libs.versions.toml), (3) Build errors and dependency conflicts, (4) Module dependencies and source sets, (5)…

vitorpamplona/amethyst · 132 tokens

nostr-expert

Nostr protocol implementation patterns in Quartz (AmethystMultiplatform's KMP Nostr library). Use when working with: (1) Nostr events (creating, parsing, signing), (2) Event kinds and tags, (3) NIP implementations (80+ NIP packages in quartz/), (4) Event builders and TagArrayBuilder DSL, (5) Nostr cryptography…

vitorpamplona/amethyst · 182 tokens

compose-slot-api-pattern

Use when designing or reviewing a reusable Jetpack Compose component whose visual regions vary by caller, or when primitive content parameters and boolean shape flags are accumulating. Technique-layer skill — complements the codebase-specific compose-expert.

vitorpamplona/amethyst · 48 tokens

nip85-trusted-assertions

The NIP-85 trusted-assertions model in Quartz (nip85TrustedAssertions/) — kind 10040 trust-provider lists, kind 30382 contact cards / user assertions, 30383 event assertions, 30384 addressable assertions, 30385 external-id assertions. Use when building or parsing these events, working with the typed tags (RankTag…

vitorpamplona/amethyst · 148 tokens

kotlin-flow-state-event-modeling

Use when writing or reviewing Kotlin StateFlow/SharedFlow/Channel choices, sentinel default values, stateIn placement, WhileSubscribed staleness, or MutableStateFlow update patterns. Technique-layer skill — complements the codebase-specific kotlin-expert.

vitorpamplona/amethyst · 57 tokens