Next.js App Router + Clerk Auth: A Practical Setup Guide

Install @clerk/nextjs package and set environment variables with correct NEXT_PUBLIC_ prefixes to avoid leaking secret keys. Wrap root layout with ClerkProvider to handle session state, token refresh, and authentication context across all components. Configure middleware to protect routes; explicitly allow public routes like sign-in, sign-up, and webhook endpoints that use HMAC signatures. Use auth() helper in API routes to retrieve userId and enforce authentication checks server-side. Every auth tutorial shows the happy path. Install, configure, done. Reality is messier - environment variable mismatches, middleware edge cases, production vs. development instance differences. Here's the full picture from integrating Clerk into RAXXO Studio, including the problems the docs don't warn you about. Why Clerk for Next.js Short answer: it handles the things you don't want to build. Email verification, OAuth flows, session management, user management UI, webhook events. For a solo developer, b