On 2026-10-06 an external integrator called /v1/check, paid 0.02 USDC over x402 on Base mainnet, and received a verdict. They then sent the identical request again. The second call returned the same answer at a cost of 0.0000 and produced no second payment. The settlement was reconciled against the chain the next day from an independent machine.
This is the part that matters. Charging once is easy; not charging twice for a repeated request is where payment systems break.
Base mainnet public RPC, read directly from an independent machine, on 2026-10-07. 1500 blocks from the settlement block were scanned, filtering by USDC contract, Transfer event, this payer and this recipient. The scan returned 1 matching transfer — the one above — and no second one in the window that covers the replay.
You do not have to take any of this from us: open the transaction in a block explorer.
It is one paid call from one integrator. It is not a commercial customer, not recurring revenue, not an audit or third-party certification. We say what happened and stop there.