Next.js App Router Fundamentals

Overview

Provide comprehensive guidance for Next.js App Router (Next.js 13+), covering migration from Pages Router, file-based routing conventions, layouts, metadata handling, and modern Next.js patterns.

TypeScript: NEVER Use any Type

CRITICAL RULE: This codebase has @typescript-eslint/no-explicit-any enabled. Using any will cause build failures.

❌ WRONG:

function handleSubmit(e: any) { ... }
const data: any[] = [];