C
How to accept USDC from an AI agent in 20 lines
A 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.
SH-03
5 min1.2k w
x402.blog
notes on paying for HTTP
tag schedule
Revision history03 entries · latest first
- B
verify, deliver, settle: getting the order right in a paid API
Every 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.
SH-028 min1.8k w - A
Why HTTP 402 sat unused for 26 years
402 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.
SH-018 min1.7k w
General notes
- 402
- payment required — the thing this log is about
- 2xx
- delivered, then settled
- 4xx 5xx
- failed; the authorization stays unspent
- link
- a reference to somewhere else
Sheet notes
- lettering
- Archivo Narrow · IBM Plex Sans · IBM Plex Mono
- ruling
- 24 px fine, 120 px heavy; zones A–F by 1–8
- build
- static, prerendered, no trackers
- feed
- /rss.xml
- elsewhere
- what has actually settled on chain