Webhooks and payment callbacks

Business notifications and trusted payment-channel facts differ.

No unified accepted developer-webhook signing/delivery/retry contract is claimed. Existing payment integrations verify channel signatures, merchant/app identity, order and amount; a developer-reported success is not payment evidence.

A browser return correlates an order only. The result page queries the caller-owned order. Duplicate, out-of-order, delayed and paid-pending-fulfillment outcomes remain recoverable. Enterprise seats, member entitlements and open Credits use distinct funding/fulfillment contracts.

Poll compliance operation/provider state for long tasks. Unknown results and timeouts do not authorize resending paid operations.