In this video, I build Dionysus — a full-stack AI GitHub SaaS that helps developers collaborate on complex codebases with AI. We start from zero with Next.js 15 (App Router) on a T3-style setup, then layer in the “real SaaS” pieces: Neon Postgres for the database, Shadcn + Tailwind for UI, and Clerk for authentication. I also show how I sync users from Clerk into my own database using a forced redirect to a `/sync-user` route and a Prisma upsert, because you’ll want your own relational data model for projects, questions, credits, and teammates. The core of the app is an end-to-end, production-ready RAG pipeline: I connect to the GitHub API, scrape a repo, embed files, and use retrieval to answer questions with full codebase context (including citing files so you can verify). On top of that, I add AI-generated commit summaries so you can quickly understand what changed while you were away, plus meeting uploads where AssemblyAI processes recordings asynchronously and lets you query meeting context later. Finally, I integrate Stripe for a credit-based system so you can sell more processing capacity, then deploy the whole thing to Vercel.