The starting point extracted after Audiophile was finished: a monorepo wired end to end, so the next project begins at working authentication rather than at an empty folder. Two apps — a React client on React Router 7 and Vite, an Express 5 REST API — sit over four packages holding the Prisma client and schema, the shared domain types and Zod schemas, and the ESLint and TypeScript configs both apps inherit.

Two vertical slices prove the wiring instead of a feature list. Signup and login run JWTs through both cookies and headers, with protected routes on the client and protected endpoints on the API. The navbar reads a public categories endpoint and an authenticated cart badge, and defines what each renders while logged out. A template that merely compiles proves nothing; these are the paths that break first when the seams are wrong.

Turborepo orchestrates the task graph and TypeScript project references carry types across the workspace boundary, so the domain package's Zod schemas are one definition point for what the client sends and what the server validates — the contract cannot drift between the two halves without failing a build.