perf

perf is a command for Claude Code from textura-agency/next16-claude-starter. It costs 19 tokens per session (625 once invoked), scanned A, original, Unlicense.

A command for measuring a web page in a real Chrome browser, finding the cause of slow frames or loading, and checking the result after each fix.

In plain words
What is it for?
Use it to investigate slow scrolling, delayed content, dropped animation frames, and page metrics such as LCP, CLS, and INP. It also checks that performance changes still pass the project's verification and build checks.
Why use it?
It replaces guesswork with a repeatable before-and-after measurement. It helps distinguish JavaScript problems from image, graphics, or browser-rendering problems.

Command for Claude Code

Written for Claude Code: argument-hint in frontmatter.

Good fit Use it to investigate slow scrolling, delayed content, dropped animation frames, and page metrics such as LCP, CLS, and INP. It also checks that performance changes still pass the project's verification and build checks.

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Install with agentmods
npx agentmods add commands/textura-agency/next16-claude-starter/perf
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.

Clone the repo
git clone --depth 1 https://github.com/textura-agency/next16-claude-starter

Made for: Claude Code.

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

README.md
[![agentmods](https://agentmods.dev/badge/commands/textura-agency/next16-claude-starter/perf/github.svg)](https://agentmods.dev/commands/textura-agency/next16-claude-starter/perf)
Your own site
<a href="https://agentmods.dev/commands/textura-agency/next16-claude-starter/perf"><img src="https://agentmods.dev/badge/commands/textura-agency/next16-claude-starter/perf/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

Your own site · 80×15
<a href="https://agentmods.dev/commands/textura-agency/next16-claude-starter/perf"><img src="https://agentmods.dev/badge/commands/textura-agency/next16-claude-starter/perf.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 19 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 625 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 $0.00019 $0.00625
Opus 5.5 $0.00008 $0.00250
Sonnet 5.5 $0.00004 $0.00125
Haiku 4.5 $0.00002 $0.00063

Measured 10d ago against content hash 76ae45bacbf6, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

perf 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 10d 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/commands/perf.md · 39 lines

What it actually says

Optimise scroll performance for: $ARGUMENTS (the home route if empty).

Use the optimize-performance skill. If the project renders a three.js / WebGL scene, run optimize-3d-scene first. The loop is the point — build, measure, attribute, fix one thing, re-measure:

  1. yarn build && yarn start — never measure next dev. yarn qa:setup once.
  2. Baseline first: node tools/qa/scroll-test.mjs --url http://localhost:3000/ — PC (wheel) and mobile (touch, 4× CPU, 4G), cold then warm, 3 runs; every frame over 50 ms with its section, cause and reproducibility. Add --first-scroll when the page has a loader. On a WebGL page also node tools/qa/fps-probe.mjs --url … (the scene's real draw rate).
  3. Attribute before fixing. Cold bad / warm clean = first-visit work inside animating frames. A gpu / raster frame with the main thread idle is GPU work (blur per letter, layer promotion, fill) — not JavaScript. Name the code with node tools/qa/profile.mjs --url … --scroll-to "<selector>".
  4. Fix one thing, re-measure with the identical config (interleave A/B runs on a busy machine). Check the fix-catalog first: obsidian/knowledge/fix-catalog.md.
  5. .claude/scripts/verify.sh, yarn lint, yarn build, node tools/qa/check-motion.mjs --url …, and qa-verify if any UI changed — a perf fix that silences a reveal is not a win. Anything a phone shows changed → mobile-device-qa.
  6. Retro — a measured fix worth reusing → obsidian/knowledge/fix-catalog.md (symptom, fix, before → after, rule/observed); a reading that misled you → obsidian/knowledge/pitfalls.md; a skill that was wrong → edit it.

The bar: ideal on PC and mobile — no frame over 50 ms, ≤ 1 % dropped, p99 ≤ 33 ms, cold and warm. Never add a fixed phone frame cap to get there.

Report the before and after verdicts with the config (and machine load) they were taken under, what you changed, what you reverted, and what you did not fix and why. Never report a win you did not re-measure; never trade visual weight without screenshots and the client's sign-off.

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. 10d ago Changed · +13 lines · +4 tokens per session 76ae45bacbf6
  2. 29d ago First seen · 26 lines · 15 tokens per session scan A 55d0b8160435

Subscribe to this mod's changes

perf is a command published in the GitHub repository textura-agency/next16-claude-starter (137 stars, last pushed 3d ago), licensed Unlicense. It adds 19 tokens to every session and 625 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-09-18.

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