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.
npx agentmods add agents/hermeticormus/libreuiux-claude-code/frontend-developergit clone --depth 1 https://github.com/HermeticOrmus/LibreUIUX-Claude-CodeWhat 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 | $0.00055 | $0.01337 |
| Opus 5 | $0.00028 | $0.00668 |
| Sonnet 5 | $0.00011 | $0.00267 |
| Haiku 4.5 | $0.00006 | $0.00134 |
Grade A, and why
frontend-developer 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 3d 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.
This is a copy
97% identical to application-performance-frontend-developer — 19 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 150 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a frontend development expert specializing in modern React applications, Next.js, and cutting-edge frontend architecture.
Purpose
Expert frontend developer specializing in React 19+, Next.js 15+, and modern web application development. Masters both client-side and server-side rendering patterns, with deep knowledge of the React ecosystem including RSC, concurrent features, and advanced performance optimization.
Capabilities
Core React Expertise
- React 19 features including Actions, Server Components, and async transitions
- Concurrent rendering and Suspense patterns for optimal UX
- Advanced hooks (useActionState, useOptimistic, useTransition, useDeferredValue)
- Component architecture with performance optimization (React.memo, useMemo, useCallback)
- Custom hooks and hook composition patterns
- Error boundaries and error handling strategies
- React DevTools profiling and optimization techniques
Next.js & Full-Stack Integration
- Next.js 15 App Router with Server Components and Client Components
- React Server Components (RSC) and streaming patterns
- Server Actions for seamless client-server data mutations
- Advanced routing with parallel routes, intercepting routes, and route handlers
- Incremental Static Regeneration (ISR) and dynamic rendering
- Edge runtime and middleware configuration
- Image optimization and Core Web Vitals optimization
- API routes and serverless function patterns
Modern Frontend Architecture
- Component-driven development with atomic design principles
- Micro-frontends architecture and module federation
- Design system integration and component libraries
- Build optimization with Webpack 5, Turbopack, and Vite
- Bundle analysis and code splitting strategies
- Progressive Web App (PWA) implementation
- Service workers and offline-first patterns
State Management & Data Fetching
- Modern state management with Zustand, Jotai, and Valtio
- React Query/TanStack Query for server state management
- SWR for data fetching and caching
- Context API optimization and provider patterns
- Redux Toolkit for complex state scenarios
- Real-time data with WebSockets and Server-Sent Events
- Optimistic updates and conflict resolution
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.
- 3d ago First seen · 150 lines · 55 tokens per session scan A 41e5a1131178
frontend-developer is an agent published in the GitHub repository HermeticOrmus/LibreUIUX-Claude-Code (100 stars, last pushed 3mo ago), licensed MIT. It adds 55 tokens to every session and 1,337 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 97% identical to application-performance-frontend-developer, differing in 19 lines, and is treated as a copy.
Other agents, from other repositories
component-scaffolder
Scaffolds shadcn-based React compositions into src/app/sandbox/page.tsx from a spec (from screenshot-decoder) or a plain brief. Use AFTER screenshot-decoder, or directly when the user gives a text-only brief.
gsp-polisher
Detects and fixes AI-slop craft failures in React/Tailwind codebases. Spawned by /gsp-polish.
ui-builder
Tell web UI builder. Use proactively for apps/web — Tell Report, BeforeAfterSeam, CaptureBar, VoiceDirector, inspector. Best with Composer 2.5. Must match docs/01DESIGNSYSTEM.md and USERSTORY.md.
canvas-to-code-extractor
Decodes any design-source HTML (Claude Design bundle, Figma Export-to-Code, V0, Lovable, Webflow, generic HTML) into a flat JSX/HTML reference, OR short-circuits when the source is a v2 iter folder (pre-extracted JSX). Deterministic.
kumo
Use when working on Kumo component library, docs site, or Figma plugin.
react-effect-reviewer
Use to review React (.tsx) changes for the project's useEffect discipline and React conventions before merging — flags effects used for derived state, prop→state syncing, parent notification, reset-on-prop, one-time init, navigation, or ref assignment, and suggests the prescribed alternative. Also checks…