code-developer

name: code-developer description: Code Developer Skill.

The Four Phases

You MUST complete each phase before proceeding to the next.

Phase 1: Data & Contract Definition

BEFORE writing any UI or Component code:

1. Define the Data Model

   • What does the entity look like in the database?
   • What are the required fields?
   • What are the relationships (1:1, 1:N, N:M)?
   • Draft the TypeScript Interface/Type definitions first.

2. Establish the Contract (API)

   • How does the frontend fetch this data?
   • What arguments does the query/mutation require?
   • What are the exact failure states (401, 403, 404, 500)?
   • Don't guess: Check the Swagger/OpenAPI spec or backend code.

3. Trace the State Lifecycle

   • Where does this data live? (URL URL params? Server State? Client Store? Local Component?)
   • Rule: Lift state up only as high as necessary.
   • Rule: Prefer Server State (React Query, SWR) over Global Client State (Redux/Context) for server data.

4. Security & Access Control

   • Who is allowed to see this?
   • Who is allowed to edit this?
   • Does the backend enforce this? (Frontend checks are just UI sugar).

Phase 2: The "Walking Skeleton"

Build the pipeline before the pixel:

1. Build the Integration Layer First

   • Create the API client methods.
   • Create the hook/service to fetch the data.
   • Verify data flows from Backend → Network Tab → Console Log.
   • Do not build UI elements yet.

2. Verify Error Handling

   • Force the network request to fail.
   • Does your service catch it?
   • Do you have a typed error object?

3. Hardcode the Happy Path

   • Create a bare-bones, unstyled test component.
   • Render JSON.stringify(data) to the screen.
   • Verify the "Walking Skeleton" connects end-to-end.

Phase 2.5: Modern Frontend Tooling (2026)

The 2026 frontend landscape:

1. State Management Evolution

   • Server State ≠ Client State (This is the key insight)
   • Server State: Use Tanstack Query (React Query), SWR, tRPC
     • Auto-caching, refetching, optimistic updates
     • Don't put API data in Redux/Context/Zustand
   • Client State: Use Zustand, Jotai, or Context (for truly local state)
     • UI toggles, form state, theme preference
   • React 19 Patterns:
     • Server Components for data fetching (Next.js App Router)
     • use() hook for promises
     • Actions for mutations

2. Build Tools (Vite Era)

   • Vite 6: 10x faster HMR than Webpack, native ESM
   • Turbopack: Next.js native bundler (Rust-based)
   • Biome: Unified linter/formatter (replaces ESLint + Prettier)
   • Bun: Ultra-fast package manager (3-10x faster than npm)
   • Anti-Pattern: Still using Create React App (deprecated 2023)

3. TypeScript Best Practices (2026)

   • Zod for Runtime Validation: Type safety at boundaries

     const UserSchema = z.object({ id: z.number(), email: z.string().email() });
     type User = z.infer<typeof UserSchema>; // DRY
     

   • Type Utilities: Leverage built-ins (Partial, Pick, Omit, Awaited)
   • Strict Mode: Enable strict: true in tsconfig
   • Rule: No any types (use unknown if truly dynamic)

Phase 3: Component Architecture

Design the structure:

1. Identify Boundaries

   • Container/Page: Handles data fetching, URL parameters, and layout.
   • Presentational/Leaf: Receives data via props. Pure functions. No side effects.
   • Rule: If a component is > 150 lines, it probably does too much.

2. Separation of Concerns

   • Logic goes in Custom Hooks or Utility functions.
   • Markup (JSX/HTML) stays clean and readable.
   • Styles (CSS/Tailwind) should be consistent.

3. Accessibility (a11y) Planning

   • Semantic HTML elements (<button> not <div>).
   • Keyboard navigation (Tab index).
   • Aria labels for non-text interactions.

Phase 4: Implementation & Polish

Iterative construction:

1. Implement Core Functionality

   • Build the inputs and display logic.
   • Connect the "Walking Skeleton" data to real inputs.
   • Use superpowers:test-driven-development for complex logic.

2. Handle Loading & Empty States

   • What does the user see while fetching? (Skeleton/Spinner)
   • What if the list is empty? (Empty state illustration)
   • What if it errors? (Retry button/Toast)

3. Defensive Coding

   • Handle null/undefined values safely (Optional Chaining ?.).
   • Validate form inputs (Zod/Yup).
   • Prevent double-submissions on buttons.

4. Final Polish

   • Transitions/Animations.
   • Responsive behavior (Mobile/Tablet).
   • Dark mode compliance.

Phase 4.5: Performance Profiling

Make it fast:

1. React Performance Tools

   • React DevTools Profiler: Record renders, find expensive components
   • Why Did You Render: Debug unnecessary re-renders

     npm i @welldone-software/why-did-you-render
     

   • Million.js: Auto-optimize React (virtual DOM replacement)

2. Core Web Vitals (Google Ranking Factors)

   • LCP (Largest Contentful Paint): <2.5s
     • Fix: Preload hero images, remove render-blocking scripts
   • FID/INP (Interaction): <100ms
     • Fix: Code splitting, lazy load heavy components
   • CLS (Cumulative Layout Shift): <0.1
     • Fix: Set width/height on images, reserve space for dynamic content
   • Tool: Lighthouse CI (automated performance regression tests)

3. Bundle Analysis

   • webpack-bundle-analyzer / vite-plugin-visualizer

Red Flags - STOP and Follow Process

If you catch yourself thinking:

• "I'll just put the fetch call inside the useEffect for now."
• "I'll fix the TypeScript any types later."
• "I'll handle errors globally, I don't need a try/catch here."
• "Just copy-paste that other component and tweak it."
• "I'll add the loading state after I get it working."
• "Why is this re-rendering 50 times? Whatever, it works."
• "I'm not sure where this prop comes from, just drill it down."
• Writing CSS/Styles before data is successfully logging to console.

ALL of these mean: STOP. Return to Phase 1.

Your Human Partner's Signals You're Doing It Wrong

Watch for these redirections:

• "Where is the data coming from?" - You skipped Phase 1.
• "Is this accessible?" - You ignored semantic HTML in Phase 3.
• "This feels slow/janky." - You botched the State Lifecycle or re-renders.
• "What happens if the API is down?" - You missed Phase 2 (Error Handling).
• "Why are we passing props down 5 levels?" - Bad Component Architecture.

When you see these: STOP. Return to Phase 3.

Common Rationalizations

Quick Reference

When Process Reveals "Backend Blockers"

If systematic investigation reveals the Backend API is missing or broken:

1. Mock it immediately.
2. Define the expected JSON structure (Phase 1).
3. Create a mock function that returns that JSON after a delay.
4. Continue development (Phase 2-4) using the mock.
5. Swap the mock for the real API endpoint when ready.

Do not stop development waiting for backend.

Supporting Techniques

• superpowers:test-driven-development - For complex validation or state logic.
• superpowers:clean-code - For keeping components small and readable.
• Feature Flagging - For merging code safely before it's 100% ready.

Real-World Impact

From development cycles:

• Data-First approach: Features land with 90% fewer integration bugs.
• UI-First approach: constant "rewrites" when data shape changes.
• Mocking: Allows frontend/backend to work in parallel without blocking. The above content shows the entire, complete file contents of the requested file.

🛠️ Recommended Frontend Stack (2026)

Core Framework

• React 19: Server Components, Actions, use() hook
• Next.js 15: App Router (React Server Components)
• TypeScript 5.6: Essential for scale

State Management

• Server State: Tanstack Query, tRPC (type-safe)
• Client State: Zustand (simple), Jotai (atomic)
• Forms: React Hook Form + Zod validation

Styling

• Tailwind CSS 4: Utility-first, fast
• shadcn/ui: Copy-paste components (not npm package)
• CSS Modules: For component-scoped styles

Build Tools

• Vite 6: Dev server (fast HMR)
• Turbopack: Production bundler (Next.js)
• Biome: Linter + Formatter (Rust-based)
• Bun: Package manager (faster than npm/pnpm)

Testing

• Vitest: Unit tests (Vite-native)
• Playwright: E2E tests (cross-browser)
• Testing Library: Component tests

Avoid

• Create React App: Deprecated, use Vite
• Redux: Overkill for most apps, use Tanstack Query + Zustand
• Moment.js: Huge bundle, use date-fns or Temporal API

📚 Learning Resources

Books

• Designing Data-Intensive Applications (Kleppmann) - Understand backend data flows
• Refactoring UI (Wathan) - Visual design for developers

Documentation

• React 19 Docs (react.dev) - Official React documentation
• MDN Web Docs - Web platform reference
• TypeScript Handbook - Type system deep dive

Communities

• Reactiflux Discord: 200k+ React developers
• Frontend Masters: High-quality video courses
• This Week In React: Newsletter (Sébastien Lorber)