frontend-ui

frontend-ui is a skill for Claude Code, Codex from soden46/engineer-flow. It costs 23 tokens per session (950 once invoked), scanned A, original, MIT.

A set of practical guidelines for building and reviewing web interfaces, including forms, layouts, interactions, accessibility, and responsive behavior.

In plain words
What is it for?
Use it when creating or checking components, forms, page layouts, loading and error states, keyboard behavior, focus handling, and screen-reader support.
Why use it?
It helps prevent confusing, inaccessible, fragile interfaces and makes UI behavior easier to reason about.

Skill for Claude CodeCodex

Part of the engineer-flow plugin — 18 skills shipped together

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/soden46/engineer-flow/frontend-ui
Any agent
npx skills add soden46/engineer-flow --skill frontend-ui
Clone the repo
git clone --depth 1 https://github.com/soden46/engineer-flow

Made for: Claude Code, Codex.

Or install engineer-flow, the plugin that ships this one along with the rest of its 18 skills.

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 frontend-ui

README.md
[![agentmods](https://agentmods.dev/badge/skills/soden46/engineer-flow/frontend-ui.svg)](https://agentmods.dev/skills/soden46/engineer-flow/frontend-ui)
Your own site
<a href="https://agentmods.dev/skills/soden46/engineer-flow/frontend-ui"><img src="https://agentmods.dev/badge/skills/soden46/engineer-flow/frontend-ui.svg" alt="Measured on agentmods" height="20"></a>
Per session 23 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 950 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 $0.00023 $0.00950
Opus 5 $0.00012 $0.00475
Sonnet 5 $0.00005 $0.00190
Haiku 4.5 $0.00002 $0.00095

Measured 5d ago against content hash e134fefececb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

frontend-ui 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 5d 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/engineer-flow/core/frontend-ui/SKILL.md · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

frontend-ui

Use this skill for UI components, forms, layouts, interaction behavior, responsive design, and accessibility.

Principles

Keep UI state explicit.

Separate presentation from unrelated business or persistence logic where practical.

Forms should provide:

  • clear labels
  • validation feedback
  • useful error states
  • loading/submission state
  • accessible interaction

Consider:

  • keyboard usage
  • focus management
  • semantic structure
  • screen readers
  • responsive layouts
  • empty states
  • loading states
  • error states

Avoid unnecessary rendering or state duplication.

Preserve user input where practical when recoverable errors occur.

Use the project's existing design system and component conventions.

Browser-Driven UI Inspection

When the task involves visual UI work and a browser-capable tool is available, inspect the real rendered interface instead of relying only on source files.

Useful browser-capable tools may include:

  • host browser tools
  • browser MCP tools
  • Playwright or Playwright MCP
  • agent-browser
  • compatible external browser or UI inspection skills

Do not hardcode a single browser tool as mandatory. Use the best available tool for the host and project.

If no browser-capable tool or runnable app is available, state that limitation and avoid claiming visual or runtime parity.

Inspect relevant:

  • rendered layout and visual hierarchy
  • DOM structure
  • accessibility tree or semantic structure
  • typography
  • spacing
  • color usage
  • component density
  • navigation structure
  • loading, empty, error, hover, focus, and active states
  • console errors
  • network or asset failures when visible in the browser

Reference-Driven UI Reconstruction

Use this workflow when the user provides a reference website, screenshot, design, or existing UI to emulate.

  1. Open or inspect the reference with the best available browser-capable tool.
  2. Capture the interface structure, layout, spacing rhythm, typography scale, color tokens, component patterns, navigation, responsive behavior, and interaction states.
  3. Separate the reusable visual language from site-specific content, logos, proprietary media, brand assets, and exact copy.
  4. Inspect the target project and its current design system, components, routes, backend contracts, and frontend stack.
  5. Map the reference design into the target project's existing conventions instead of blindly cloning markup or adding an unrelated design system.
  6. Implement the smallest coherent UI change that satisfies the task.
  7. Re-open the local app and compare against the intended visual direction.
  8. Iterate until the implemented UI is visually coherent across the required states and viewports.

Read the full file on GitHub · 135 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. 5d ago First seen · 135 lines · 23 tokens per session scan A e134fefececb

Subscribe to this mod's changes

frontend-ui is a skill published in the GitHub repository soden46/engineer-flow (3 stars, last pushed 2d ago), licensed MIT. It adds 23 tokens to every session and 950 once invoked, about $0.0001 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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