Card Checkout Is Dead for Agents. The Replacement Rails Have Settled 191 Million Transactions.
Card-based checkout for AI agents ended in March 2026. That was when ACP retired its in-chat flow. The industry finally admitted that forcing legacy payment rails into agentic workflows was unsustainable. Now, the market is splitting into two distinct, stablecoin-native replacement rails: the x402 protocol and the Machine Payments Protocol (MPP). They are not converging.…