Checks vouchers of a payment channel by computation only - nothing is ever claimed, redeemed or refunded. Signatures are verified cryptographically against the address each voucher claims to be signed by, in EIP-712 form when the typed data is supplied, otherwise as a plain message signature. Double spending is the expensive case and is checked in full: every voucher id occurring more than once is reported with all its occurrences and whether the duplicates agree on the amount. Sums are added up
https://x402.halowerk.com/channel/audit