x402 isn’t good (yet) — Jan Curn, Apify

A verified payment is not necessarily a collected payment. In this Apify talk, Jan Curn describes the gap in x402, a protocol that uses the long-dormant HTTP 402 status code so a server can ask an agent to pay. Between the moment a server verifies a payment signature and the moment it settles on the blockchain, nothing stops the buyer spending that money elsewhere, and a client can create a thousand signatures against one wallet. A seller who starts real work on the strength of verification is therefore exposed.

As described, the safe approach is to start the work only after settlement, which suits a fixed-price call but is awkward for slower jobs. For work whose final cost is unknown, Apify charges the full amount first and refunds the remainder. That costs a second blockchain transaction and makes the buyer rely on the seller to return the unused balance.