The x402 HTTP payment exchange: six-step sequence diagram from initial probe through EIP-3009 authorization signing, facilitator settlement, and resource delivery. Tap any step to inspect the exact header format.
HTTP 402 sat reserved for 30 years. x402 fills it: an AI agent signs an EIP-3009 authorization into a header, a facilitator settles on Base in two seconds, no ETH required. Protocol mechanics, production numbers, and where the centralization risk lives.