perf-checklist

perf-checklist is a skill for Claude Code from atuljha23/holocron. It costs 32 tokens per session (787 once invoked), scanned A, original, MIT.

A quick reference for checking website performance. It covers loading speed, layout movement, interaction delays, JavaScript and CSS size, database queries, and caching.

In plain words
What is it for?
Use it during implementation or code review to inspect Core Web Vitals, reduce blocking resources and oversized bundles, and improve rendering, queries, and caching.
Why use it?
It gives developers concrete checks and target values when a site feels slow or responds poorly.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the holocron plugin — 11 skills, 24 commands, 14 agents, 6 hooks shipped together

Good fit Use it during implementation or code review to inspect Core Web Vitals, reduce blocking resources and oversized bundles, and improve rendering, queries, and caching.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/atuljha23/holocron/perf-checklist
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.

Any agent
npx skills add atuljha23/holocron --skill perf-checklist
Clone the repo
git clone --depth 1 https://github.com/atuljha23/holocron

Made for: Claude Code.

Or install holocron, the plugin that ships this one along with the rest of its 11 skills, 24 commands, 14 agents, 6 hooks.

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 perf-checklist

README.md
[![agentmods](https://agentmods.dev/badge/skills/atuljha23/holocron/perf-checklist/github.svg)](https://agentmods.dev/skills/atuljha23/holocron/perf-checklist)
Your own site
<a href="https://agentmods.dev/skills/atuljha23/holocron/perf-checklist"><img src="https://agentmods.dev/badge/skills/atuljha23/holocron/perf-checklist/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for perf-checklist

Your own site · 80×15
<a href="https://agentmods.dev/skills/atuljha23/holocron/perf-checklist"><img src="https://agentmods.dev/badge/skills/atuljha23/holocron/perf-checklist.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 32 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 787 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 $0.00032 $0.00787
Opus 5 $0.00016 $0.00394
Sonnet 5 $0.00006 $0.00157
Haiku 4.5 $0.00003 $0.00079

Measured 9d ago against content hash 591578786220, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

perf-checklist 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 9d 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.

skills/perf-checklist/SKILL.md · 71 lines

How it starts

The opening of the file, as written. The whole thing — 71 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Performance checklist

Measure first. Opinion second.

Frontend — Core Web Vitals

LCP (Largest Contentful Paint) — ≤ 2.5s

  • Hero image preloaded, sized, fetchpriority="high".
  • Critical CSS inlined or loaded before render-blocking resources.
  • Fonts: font-display: swap, preloaded if above the fold.
  • No render-blocking JS on the critical path. defer or async.

CLS (Cumulative Layout Shift) — ≤ 0.1

  • width/height on images and iframes.
  • Reserved space for async content (skeletons, aspect-ratio boxes).
  • No ads / embeds inserted above existing content without reservation.
  • No web-font swap without matching metrics.

INP (Interaction to Next Paint) — ≤ 200ms

  • No long tasks (>50ms) on interaction paths.
  • Break up work: scheduler.yield(), idle callbacks, debounced expensive calcs.
  • Virtualize long lists.
  • Event handlers don't do layout thrash — batch reads then writes.

Frontend — bundle

  • Tree-shake-friendly imports. import { x } from 'lib' — not import lib from 'lib' unless required.
  • No moment — use date-fns or Temporal polyfill.
  • No full lodash — use lodash-es named imports or dropping to native.
  • Code-split routes. Lazy-load heavy components that aren't above the fold.
  • Images: modern formats (WebP/AVIF), responsive srcset, served from a CDN.

Backend — query layer

  • No query inside a loop over a result set (N+1). Batch with IN/JOIN/dataloader.
  • Every WHERE / ORDER BY / JOIN column used on large tables is indexed.
  • SELECT * replaced with specific columns on hot paths.
  • Pagination uses cursors, not offset, on tables that grow.
  • Queries have statement timeouts.

Backend — request

  • Timeouts on every outbound call.
  • Retries capped with backoff. Never infinite.
  • Circuit breakers for dependencies you can't trust.
  • Response compression enabled (gzip/brotli).
  • Static assets behind a CDN with long Cache-Control.

Read the full file on GitHub · 71 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. 9d ago First seen · 71 lines · 32 tokens per session scan A 591578786220

Subscribe to this mod's changes

perf-checklist is a skill published in the GitHub repository atuljha23/holocron (2 stars, last pushed 4mo ago), licensed MIT. It adds 32 tokens to every session and 787 once invoked, about $0.0002 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 2026-08-31.

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