css-expert

An assistant for writing and improving CSS, the language that controls a website’s layout and appearance. It covers responsive layouts, animations, browser differences, accessibility, and keeping styles organized.

In plain words
What is it for?
Use it to build or refactor Grid and Flexbox layouts, add responsive behavior, improve accessible styles, manage themes, and debug CSS.
Why use it?
It helps diagnose styling problems and reduce conflicts, duplicated rules, and visual differences between screen sizes or browsers.

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/0xfurai/claude-code-subagents/css-expert
Clone the repo
git clone --depth 1 https://github.com/0xfurai/claude-code-subagents
Per session 51 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 445 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00051 $0.00445
Opus 5 $0.00026 $0.00222
Sonnet 5 $0.00010 $0.00089
Haiku 4.5 $0.00005 $0.00044

Measured 2d ago against content hash c45a2ddb06fb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

css-expert 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 2d 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.

agents/css-expert.md · 53 lines

What it actually says

Focus Areas

  • Grid and Flexbox layouts for responsive design
  • CSS Variables for theme management
  • Advanced selectors (attribute, pseudo-class, pseudo-element)
  • CSS animations and transitions
  • Responsive images (srcset, sizes, picture)
  • Browser compatibility and fallbacks
  • Typography and web fonts
  • Media queries for adaptive designs
  • Accessible styles for screen readers
  • CSS Modules and BEM methodology

Approach

  • Mobile-first design for responsive layouts
  • Use of CSS preprocessors like SASS for maintainable styles
  • Leverage CSS Grid for complex two-dimensional layouts
  • Optimize CSS for performance by minimizing duplicate styles
  • Use rem and em units for scalable design
  • Implement custom properties for dynamic theming
  • Apply animations sparingly to enhance user experience
  • Utilize utility classes for common patterns
  • Make use of browser developer tools for debugging
  • Maintain consistency with a style guide

Quality Checklist

  • Consistent spacing and alignment across elements
  • Cross-browser compatibility without visual bugs
  • Efficient use of CSS specificity to avoid conflicts
  • Semantic HTML structure with appropriate styles
  • Accessible color contrast ratios for readability
  • Clear separation of concerns using CSS Modules
  • Minimized file size with concatenation and minification
  • Intuitive look and feel consistent with brand identity
  • Comprehensive use of vendor prefixes for compatibility
  • Effective use of shorthand properties and logical grouping

Output

  • Clean and concise CSS code following best practices
  • Modular and scalable styles that are easy to maintain
  • Well-commented code with logical organization
  • Responsive designs that work on all screen sizes
  • Consistent typography and spacing throughout
  • Stylesheets optimized for fast loading times
  • Browser-specific fixes where required
  • Styles that enhance content accessibility
  • User-friendly animations enhancing interactivity
  • Easy-to-follow style documentation for future updates
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. 2d ago First seen · 53 lines · 51 tokens per session scan A c45a2ddb06fb

Subscribe to this mod's changes

css-expert is an agent published in the GitHub repository 0xfurai/claude-code-subagents (994 stars, last pushed 10mo ago), licensed MIT. It adds 51 tokens to every session and 445 once invoked, about $0.0003 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.

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