Circle-verified x402, on Arc.
The same HTTP-402 call, side by side: Circle's vanilla facilitator on the left, a Cadenza-attested facilitator on the right. Both settle real USDC on Arc testnet. One of them closes the arXiv-documented Free-Riding attack.
Live receipts
x402 v2 separates spec, SDK, and facilitator. Circle presently ships with a vanilla facilitator that applies no attestation. Cadenza's facilitator layers rate-limit fairness and payload-integrity attestations underneath the same HTTP surface — Circle keeps its product; Cadenza adds the missing enforcement.
Every Arcscan link on this page resolves against testnet.arcscan.app. Verify yourself.
Vanilla x402 facilitator
reference
Run a receipt above.
Cadenza-attested facilitator
attested
Run a receipt above.