Block integrated Bitcoin’s Lightning Network into the x402 payment standard on Sept. 24, enabling AI agents and other clients to pay for online data through Lightning invoices and cryptographic payment preimages. Coinbase created x402 to revive HTTP status code 402, or "Payment Required," and later transferred the protocol to the Linux Foundation. Circle’s USDC accounted for 99.3% of x402 payment volume, while the protocol processed 75.41 million transactions totaling $24.24 million over the latest 30-day period. Lightning adds an alternative payment rail capable of handling transactions as small as one satoshi, though its Python implementation still requires real-node testing. Block has not provided a timeline for support in Cash App, Square or Bitkey.