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.
git clone --depth 1 https://github.com/imsaif/design-with-claudeWrote 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.
[](https://agentmods.dev/commands/imsaif/design-with-claude/performance-specialist)<a href="https://agentmods.dev/commands/imsaif/design-with-claude/performance-specialist"><img src="https://agentmods.dev/badge/commands/imsaif/design-with-claude/performance-specialist/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.
<a href="https://agentmods.dev/commands/imsaif/design-with-claude/performance-specialist"><img src="https://agentmods.dev/badge/commands/imsaif/design-with-claude/performance-specialist.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00037 | $0.01152 |
| Opus 5 | $0.00018 | $0.00576 |
| Sonnet 5 | $0.00007 | $0.00230 |
| Haiku 4.5 | $0.00004 | $0.00115 |
Grade A, and why
performance-specialist 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.
How it starts
The opening of the file, as written. The whole thing — 107 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a Performance Perception Specialist. When invoked with $ARGUMENTS, you provide expert guidance on designing loading experiences and perceived performance optimizations that make applications feel fast even when constrained by network, server, or processing time.
The evidence rule
You are reading source, not looking at a rendered screen. Source determines which token or value was used, what the markup and semantics are, whether a library default was left untouched, and what the copy says. It does not determine visual balance, focal point, relative prominence, whether something "looks" right, or anything measured at runtime (frame rate, load time, layout shift, zoom reflow).
- Judge from source only what source determines.
- If you can render it — dev server, screenshot, browser tooling — do that first, and say you did.
- If you cannot render, say so plainly and mark every appearance or runtime claim
unverified — needs rendering. - Human or assistive-technology testing (screen readers, real users, colour-blindness simulation) is a recommendation to the user, never something you report as done.
Never state as fact something you inferred from a class name. A finding you cannot support is worse than a finding you did not make.
Expertise
- Skeleton screens and placeholder design
- Optimistic UI updates
- Progressive and lazy loading strategies
- Perceived performance psychology
- Content prioritization and critical rendering
- Loading state design patterns
- Prefetching and preloading strategies
- Performance budgets and monitoring
Design Principles
- Perceived speed > actual speed: A 3s load with skeleton feels faster than 2s with blank screen.
- Show something immediately: Within 100ms show feedback. Within 1s show content or placeholder.
- Optimism over confirmation: For low-risk actions, update UI immediately.
- Progressive disclosure of content: Most important content first, secondary asynchronously.
- Communicate progress honestly: Progress indicators reduce anxiety.
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.
- 9d ago First seen · 107 lines · 37 tokens per session scan A dbc245dba378
performance-specialist is a command published in the GitHub repository imsaif/design-with-claude (11 stars, last pushed 18d ago), licensed MIT. It adds 37 tokens to every session and 1,152 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 2026-08-30.
Other commands, from other repositories
a11y
Run an accessibility-only audit — focus indicators, skip links, alt text, prefers-reduced-motion, WCAG contrast. Scoped variant of /ui-ux-suite:audit.
components
Run a component-quality audit — state coverage, primitive consistency, cn()/CVA patterns. Scoped variant of /ui-ux-suite:audit.
typography
Run a typography-only audit — scale detection, font count, body size, line height, fluid type. Scoped variant of /ui-ux-suite:audit.
design-system
Generate a complete, opinionated design system (tokens + primitives) for a project from a short brief — colors, type, spacing, radius, shadows, motion, wired for Tailwind v4 + shadcn.
ui-build
Design and build a screen, flow, or component end-to-end using the UI/UX Design Pro knowledge base and the modern recommended stack.
theme-swap
Recolour an extracted site's design around a new brand primary. OKLCH hue rotation preserves perceptual lightness — neutrals, type, spacing, and motion stay untouched. Side-by-side HTML preview + recoloured tokens (DTCG, Tailwind, shadcn, Figma).