Series: Spec-Driven Development with Claude Code — Part 1 · Part 2 · Part 3 In Part 1 , we set up our project structure but left it without logic. Today we implement authentication and data — the two layers that turn a wireframe into a real app. The pattern stays the same: spec first, code second . Step 1: Set Up Supabase Before touching any code, we configure the backend. Go to supabase.com and create a new project Once created, go to Project Settings → API and copy: URL anon public key Paste them into your .env : SUPABASE_URL = https://yourproject.supabase.co SUPABASE_ANON_KEY = eyJhbGciOiJI... Enter fullscreen mode Exit fullscreen mode In the Supabase dashboard, go to Authentication → Providers and make sure Email is enabled (disable email confirmation for development). Step 2: The Authentication Spec We create a dedicated spec for the auth module.…