Recurring USDC billing with weekly / monthly / yearly intervals. Receipts persist client-side; the renewal-window check is a 4-line helper.
25+ wallets across EVM, Solana, Bitcoin, Tron, Kaspa. One modal, any chain.
On success, your webhook receives metadata.kind=subscription with theplanId and subscriptionId — provision access, then schedule renewal with computeNextRenewal().