Engineering notes on HTTP 402, agent payments, and building APIs that charge per request. Wire formats, ordering guarantees, and code that runs.https://x402.blogen-usTue, 18 Aug 2026 00:00:00 GMThttps://x402.blog/posts/accept-usdc-from-an-ai-agent-in-20-lineshttps://x402.blog/posts/accept-usdc-from-an-ai-agent-in-20-linesA working x402 paywall in one route handler: 402 with a price, verify the signature, do the work, settle. Plus the four things that will break it.Tue, 18 Aug 2026 00:00:00 GMTNikshep S.x402usdctutorialagentshttps://x402.blog/posts/verify-deliver-settle-order-in-a-paid-apihttps://x402.blog/posts/verify-deliver-settle-order-in-a-paid-apiEvery paid endpoint does the same three things. There are six ways to order them and only one that never takes money for a response it failed to send.Tue, 04 Aug 2026 00:00:00 GMTNikshep S.api-designpaymentsreliabilityx402https://x402.blog/posts/why-http-402-sat-unused-for-26-yearshttps://x402.blog/posts/why-http-402-sat-unused-for-26-years402 was never broken. It was half a protocol: a status code with no challenge header and no credential header. The missing half took 26 years.Tue, 21 Jul 2026 00:00:00 GMTNikshep S.http-402historyprotocol