Adding Features to Your Fine.dev App

Fine.dev handles well-specified features in existing codebases well. It's less effective for architectural decisions, cross-repository changes, infrastructure-alongside-code features, and features that require understanding system context beyond the codebase

Implementing a detailed GitHub issue with clear acceptance criteria. Adding a new API endpoint with request and response schemas specified. Building a new React component from a design spec. Updating an existing feature based on a detailed change request. Adding tests for an existing feature that lacks coverage

Almost every SaaS app needs payment processing. Stripe is the standard — it handles credit cards, subscriptions, invoices, and payouts. The key pieces: a checkout flow for collecting payment, webhooks to update your database when payments succeed or fail, and a customer portal for managing subscriptions. Fine.dev might generate a basic checkout page, but the webhook handling and subscription lifecycle management usually need to be built by hand.

Your app needs user accounts with secure login. The easiest options: NextAuth (for Next.js), Supabase Auth, or Clerk. These handle email/password login, social login (Google, GitHub), password resets, and session management. Don't build auth from scratch — the security implications are too complex for a first implementation.

Transactional emails — welcome emails, password resets, order confirmations — require an email service provider. Resend is the simplest to set up, SendGrid is the most established, and Amazon SES is the cheapest at scale. You'll need email templates, a sending service, and proper DNS configuration (SPF, DKIM) so your emails don't land in spam.

If a feature requires deep technical expertise (payment compliance, data privacy, real-time systems), it's faster and safer to get professional help than to iterate with AI tools. Our team adds features like these to Fine.dev apps every week — we know the patterns and the pitfalls.