Writing an Effective CLAUDE.md

# Project: MyApp

## Overview
E-commerce platform built with Next.js 15, TypeScript, Tailwind CSS 4, and Supabase.
Monorepo with apps/web (frontend) and apps/api (backend).

## Tech Stack
- **Framework**: Next.js 15 (App Router, Server Components)
- **Language**: TypeScript 5.5 (strict mode)
- **Database**: Supabase (PostgreSQL + Auth + Storage)
- **Styling**: Tailwind CSS 4 with CSS variables

## Directory Structure
\`\`\`
apps/web/
  app/           # Next.js App Router pages
  components/    # React components (PascalCase directories)
  lib/           # Utilities, services, types
  store/         # Zustand stores
apps/api/
  routes/        # Express route handlers
  middleware/    # Auth, validation, logging
  models/        # Database models
\`\`\`

## Conventions
- Components: PascalCase directories with index.tsx barrel exports
- Hooks: camelCase with "use" prefix in lib/hooks/
- Types: defined in lib/types/, never use `any`
- Styling: Tailwind classes only, NO inline styles, NO CSS modules
- Imports: use @/ alias, group by: react > next > external > internal
- State: Zustand for client state, React Query for server state

## NEVER Do
- NEVER use `any` type — use `unknown` and narrow
- NEVER use default exports (except pages and layouts)
- NEVER hardcode colors — use CSS variables via var(--)
- NEVER commit .env files with real credentials
- NEVER use useEffect for data fetching — use React Query
- NEVER add console.log to committed code

## Commands
- `npm run dev` — start development server
- `npm run build` — production build
- `npm run test` — run Jest tests
- `npm run lint` — ESLint check
- `npm run typecheck` — TypeScript validation