Building an AI SaaS in a Weekend: Auth, Billing, and Usage Tracking

The first version of every AI SaaS product looks the same: a chat box, a submit button, and a direct API call. No auth. No billing. No usage tracking. Just vibes. The second version is where most projects die -- because wiring up auth, payments, and a dashboard from scratch takes 2-3 weeks of work that has nothing to do with your actual product. Here's how to go from idea to deployed AI SaaS in a weekend, with the full stack pre-configured. The Stack Before I get into implementation, here's what I use and why: Layer Choice Why Framework Next.js 14 App Router Server components + API routes in one project Auth NextAuth v5 Google + GitHub OAuth, sessions, DB integration Payments Stripe Best docs, best DX, webhook handling is straightforward AI Claude API / OpenAI Both pre-wired, switch with one env var Database Prisma + PostgreSQL Type-safe ORM, excellent migration tooling UI Tailwind + shadcn/ui Fast, consistent, accessible by default Deployment Vercel Zero-config for Next.js, handles en