Arbitrum One: does the seller deliver when paid there?

Updated 2026-09-30.

Each row is one payTo that lists both Arbitrum One and Base with the same address. vet402 buys the same listing once on each chain, the same UTC day, from the same wallet, and reads each USDC transfer back on its chain. The fix column says what the seller can change when Arbitrum does not come back. A payment that did not settle is never counted against the seller, and a result that is not in the seller's favour is shown after vet402 has told that seller.

The daily record on Arbitrum One

After each UTC day with purchases, vet402 writes that day's Merkle root into DeliveryRoots on Arbitrum One, at 0x84DB4733f8F9e6803Af811fD9E438aEBc0b90145. A day is written once and never changes, and only vet402's own key for this contract can write it.

The root holds facts, not verdicts. Each purchase is one leaf: what vet402 paid and to whom, the settlement transaction the chain shows for it (or that none was found), and what came back (the HTTP status, the size and the sha256 of the answer, not the answer). Whether a purchase counts as delivered, and whose side a failure is on, is not in the root: it is decided each time this page is built, with that day's rules, so a rule change never leaves an old verdict on chain. To check a purchase, take its record from data/evm/roots/arbitrum.json, compute keccak256 of the record as canonical JSON (keys sorted, no whitespace, strings escaped as JSON.stringify does), and call verify(dayNumber, digest, proof) on the contract: it returns true only for a record of that day. Another contract can make the same call.

Every purchase is in the root from the start. A purchase whose verdict today is not in the seller's favour has its record shown only after vet402 has told that seller; until then the file shows its index alone.

How vet402 pays for this

vet402 pays from one wallet, 0x9B59…4E51, the same on every EVM chain it buys on, with the seller's own x402 402: exact scheme, EIP-3009 transferWithAuthorization only (no Permit2, no approve), to the payTo the 402 named when vet402 planned the purchase, never more than that price. On this chain: at most 0.10 USDC a purchase, 2.00 USDC in total and 90 purchases, in a ledger of its own. The facilitator the seller chose submits the payment and pays its gas.