Six weeks ago I shipped the first version of MelodyCraft AI , a single-page AI music generator. Today there are 21 tool pages live — rap generators, name generators, a lyrics-to-song workflow, an 8-page band-name cluster, and a few experiments that worked despite my better judgment. I'm a solo dev. No co-founder, no design team. The whole thing runs on Next.js 15 (App Router), Drizzle ORM, Better Auth, Tailwind 4, and a thin abstraction over two AI providers. One Git repo, deployed on Vercel. This is a brain dump of what I'd tell myself before week 1. Not a brag list — half of it is mistakes. Some of these are technical, some are product, some are weirdly specific to the way solo devs accidentally make their own lives harder. Here's the rundown. ## 1. The stack matters less than the page checklist Everyone obsesses over stack selection. I did too — Next.js 15 vs SvelteKit, Drizzle vs Prisma, Better Auth vs NextAuth vs roll-your-own. In the end the stack delta was maybe 2-3 days over 6 weeks.…