I implement Stripe Billing subscriptions in Next.js + Node.js/TypeScript: checkout flow, Customer Portal, proration rules, and plan changes — plus production-grade webhook handling.

What you get (1–7 days):

Stripe products/prices aligned with your plan rules

Subscription flow (Checkout + Portal integration)

Webhook signature verification + idempotent processing (dedupe by event.id)

Upgrade/downgrade/cancel behavior with proration verified in test mode

Clean PR(s) + deployment checklist + acceptance steps

Acceptance criteria:

Create/upgrade/downgrade/cancel works in Stripe test mode

Webhooks are verified, idempotent, and safely retryable

Your app reflects subscription state consistently

What I need:

Repo access (GitHub invite or zip)

Stripe test mode access

Plan rules (tiers, trials, metered vs fixed, cancellation policy)