moai-domain-frontend

---
name: moai-domain-frontend
description: >
  Frontend development specialist covering React 19, Next.js 16, Vue 3.5,
  and modern UI/UX patterns with component architecture. Use when building
  web UIs, implementing components, optimizing frontend performance, or
  integrating state management.

when_to_use: >
  Use for frontend development: React 19, Next.js 16, Vue 3.5 components,
  responsive UIs, TypeScript/JavaScript, state management, hooks, props,
  JSX/TSX, DOM, CSS, Tailwind, and client-side browser performance.

license: Apache-2.0
compatibility: Designed for Claude Code
allowed-tools: Read, Grep, Glob
user-invocable: false
metadata:
  version: "2.1.0"
  category: "domain"
  status: "active"
  updated: "2026-03-28"
  tags: "frontend, react, nextjs, vue, ui, components"
  author: "MoAI-ADK Team"
---

# Frontend Development Specialist

## Quick Reference

Modern Frontend Development - Comprehensive patterns for React 19, Next.js 16, Vue 3.5.

Core Capabilities:

- React 19: Server components, concurrent features, cache(), Suspense
- Next.js 16: App Router, Server Actions, ISR, Route handlers
- Vue 3.5: Composition API, TypeScript, Pinia state management
- Component Architecture: Design systems, compound components, CVA
- Performance: Code splitting, dynamic imports, memoization, Framer Motion animations

When to Use:

- Modern web application development
- Component library creation
- Frontend performance optimization
- UI/UX with accessibility

---

## Patterns

### Framework Patterns

React 19 Patterns:

- Server Components, Concurrent features, cache() API, Form handling

Next.js 16 Patterns:

- App Router, Server Actions, ISR, Route Handlers, Parallel Routes

Vue 3.5 Patterns:

- Composition API, Composables, Reactivity, Pinia, Provide/Inject

### Architecture Patterns

Component Architecture:

- Design tokens, CVA variants, Compound components, Accessibility

State Management:

- Zustand, Redux Toolkit, React Context, Pinia

Performance Optimization:

- Code splitting, Dynamic imports, Image optimization, Memoization

AI-Assisted Frontend Patterns:

- Visual reference strategy, Playwright verification, motion design, reasoning-level tuning

Vercel React Best Practices:

- 45 rules across 8 categories from Vercel Engineering
- Eliminating waterfalls, bundle optimization, server-side performance
- Client-side data fetching, re-render optimization, rendering performance

---

## Implementation Quickstart

### React 19 Server Component

Create an async page component that uses the cache function from React to memoize data fetching. Import Suspense for loading states. Define a getData function that fetches from the API endpoint with an id parameter and returns JSON. In the page component, wrap the DataDisplay component with Suspense using a Skeleton fallback, and pass the awaited getData result as the data prop.

### Next.js Server Action

Create a server action file with the use server directive. Import revalidatePath from next/cache and z from zod for validation. Define a schema with title (minimum 1 character) and content (minimum 10 characters). The createPost function accepts FormData, validates with safeParse, returns errors on failure, creates the post in the database, and calls revalidatePath for the posts page.

### Vue Composable

Create a useUser composable that accepts a userId ref parameter. Define user as a nullable ref, loading as a boolean ref, and fullName as a computed property that concatenates firstName and lastName. Use watchEffect to set loading true, fetch the user data asynchronously, assign to user ref, and set loading false. Return the user, loading, and fullName refs.

### CVA Component

Import cva and VariantProps from class-variance-authority. Define buttonVariants with base classes for inline-flex, items-center, justify-center, rounded-md, and font-medium. Add variants object with variant options for default (primary background with hover) and outline (border with hover accent). Add size options for sm (h-9, px-3, text-sm), default (h-10, px-4), and lg (h-11, px-8). Set defaultVariants for variant and size. Export a Button component that applies the variants to a button element className.

---

## Works Well With

- moai-domain-backend - Full-stack development
- moai-ref-ui-polish - Component library integration
- moai-ref-ui-polish - UI/UX design principles
- `.claude/rules/moai/languages/typescript.md` - TypeScript patterns (auto-loaded via paths frontmatter)
- moai-workflow-testing - Frontend testing

---

## Technology Stack

Frameworks: React 19, Next.js 16, Vue 3.5, Nuxt 3

Languages: TypeScript 5.9+, JavaScript ES2024

Styling: Tailwind CSS 3.4+, CSS Modules, shadcn/ui

Animation: Framer Motion

State: Zustand, Redux Toolkit, Pinia

Testing: Vitest, Testing Library, Playwright

Verification: Playwright (visual inspection, functional testing)

---

## Resources

Official documentation:

- React: https://react.dev/
- Next.js: https://nextjs.org/docs
- Vue: https://vuejs.org/

---

Version: 2.1.0

<!-- moai:evolvable-start id="rationalizations" -->
## Common Rationalizations

| Rationalization | Reality |
|---|---|
| "Accessibility can be added after launch" | Post-launch accessibility is a rewrite, not an addition. Semantic HTML and ARIA are foundational, not decorative. |
| "This component is too simple to need its own test" | Simple components compose into complex UIs. A broken simple component cascades failures everywhere it is used. |
| "Server components are always faster" | Server components add network round trips. Client components with proper caching can outperform naive server components. Measure, do not assume. |
| "I will just use any as the TypeScript type for now" | any disables the type checker for everything downstream. One any infects the entire call chain. |
| "Global CSS is fine for this project" | Global CSS creates specificity conflicts as the project grows. Scoped styles (CSS modules, Tailwind) prevent collisions. |

<!-- moai:evolvable-end -->

<!-- moai:evolvable-start id="red-flags" -->
## Red Flags

- Component renders user-provided HTML without sanitization (XSS vector)
- TypeScript `any` type used in component props or state definitions
- No loading or error states defined for async data fetching components
- Accessibility attributes (aria-label, role) missing from interactive elements
- Bundle size increased by more than 50KB without justification
- Component has more than 300 lines without extraction into sub-components

<!-- moai:evolvable-end -->

<!-- moai:evolvable-start id="verification" -->
## Verification

- [ ] All interactive elements have accessible names (aria-label or visible text)
- [ ] Components handle loading, error, and empty states
- [ ] No TypeScript `any` in new or modified code (show grep results)
- [ ] Bundle size impact measured for new dependencies (show analyzer output)
- [ ] User-provided content rendered with proper escaping or sanitization
- [ ] Components under 300 lines or decomposed with clear sub-component boundaries

<!-- moai:evolvable-end -->