Adding Features to Your Codex CLI App

Codex generates individual functions and scripts well, but doesn't scaffold full applications — no routing, no authentication, no database schema, no deployment config. It struggles with features that require coordinating multiple systems or maintaining state across requests

Data processing pipelines in Python with proper error handling and retry logic. REST API endpoints with authentication and input validation. CLI tools with argument parsing and help text. Test suites with fixtures and parameterized cases. Database migration scripts

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. Codex CLI 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 Codex CLI apps every week — we know the patterns and the pitfalls.