Next.js 15 + Supabase SaaS Starter (AI‑Optimized for Cursor)

Stop spending hours wiring auth and billing. Start shipping real SaaS features today.

You open a fresh project and immediately lose half a day setting up Supabase auth, Stripe billing, and a folder structure your AI assistant won’t destroy. You jump between docs, copy snippets, fix type errors, and pray your RLS rules actually protect tenant data. By the time it works, you’re too drained to build the feature you came for.

This starter removes all of that. It’s a production‑ready Next.js 15 + Supabase SaaS foundation with fully wired auth, billing, RLS, and AI‑optimized patterns designed specifically for Cursor. No guessing. No fragile examples. Just code you can trust on day one.

What’s Included:
- Preconfigured Supabase auth with OAuth, email, and magic links, plus 8 security‑safe middleware patterns.
- Fully implemented RLS policies and tenant context enforcement across server actions, API routes, and webhooks.
- Stripe subscription billing with secure, idempotent API handlers and 3 verified webhook flows.
- AI‑tuned project structure so Cursor produces clean, consistent code in every file.
- Protected dashboard example showing sessions, redirects, and user context wired end‑to‑end.
- Prebuilt database schema with users, teams, and subscriptions, plus migration files.
- Server/client boundary patterns that eliminate hydration mismatches and app‑router pitfalls.
- Environment, typing, error, and logging presets used in real production apps.

Built from patterns used in live SaaS products handling thousands of authenticated requests per day. Every file exists because it prevented a real bug, exploit, or late‑night debugging session.

Who This Is For:
- Developers who want to ship a production‑safe SaaS in a weekend.
- Builders using Cursor who want AI‑ready scaffolding that won’t break with every edit.
- Freelancers who need a reliable base for client apps with secure auth and billing.

Who This Is NOT For:
- Developers who want to hand‑roll every auth or billing detail themselves.
- Hobby projects that don’t need user accounts, permissions, or payments.

If this doesn’t save you at least 4 hours on setup, reach out for a full refund.

What's Included (12 files)

• lib-multi-tenant-org-loader.ts-–-Auto-load-tenant-context-with-RLS-safe-enforcement
• app-auth-sign-in-page.tsx-–-Production-ready-email-password-+-magic-link-sign-in-with-validation
• supabase-rls-multi-tenant-policies.sql-–-Fully-written-multi‑tenant-security-policies-(industrial-strength)
• SETUP-GUIDE.md-–-10-minute-setup-to-connect-Supabase,-Stripe,-env-vars,-and-run-locally
• TROUBLESHOOTING.md-–-Fixes-for-common-Supabase,-Stripe,-and-Next.js-15-edge-cases
• cursorrules-prompts-feature-spec.prompt-–-Prompt-template-for-safely-generating-new-features-via-Cursor
• lib-supabase-createClientServer.ts-–-Verified-safe-server-side-Supabase-client-with-typed-responses
• cursorrules-.cursorrules-–-AI-instructions-that-force-Cursor-to-extend,-not-overwrite,-core-logic
• pages-api-stripe-webhook-handler.ts-–-Idempotent-webhook-processor-with-replay-attack-protection
• app-auth-callback-route.ts-–-Secure-Supabase-OAuth-callback-handler-with-CSRF-+-state-checks
• pages-api-stripe-create-checkout-session.ts-–-Stripe-Checkout-session-creation-with-anti-abuse-guards
• app-(dashboard)-billing-page.tsx-–-User-billing-portal-with-role-safe-access-and-error-states-handled