Payment flows must handle subscription renewals, not just first checkouts

A payment flow can pass launch checks yet fail weeks later if it only processes the events sent during the initial checkout. Renewals often trigger different events, and a handler that ignores them can acknowledge the payment while never extending the customer's access. This can leave a customer who has just paid downgraded without anyone noticing. The advice is to list every event a payment provider sends across a subscription's lifecycle, including renewals, failed payments and cancellations, and ensure each is either handled or logged clearly. Developers are also encouraged to test a renewal in a sandbox environment before launch rather than waiting a month to discover problems.