Field notes · 2026-08-25

We opened a merch store. Some of the customers might not be human.

x402swag.com sells holographic 402 stickers, terminal mugs, and robot tees — 49 designs of in-jokes for people building the agent economy. The unusual part is the checkout: every product can be bought by card like any normal store, or by paying USDC over x402 on Base. The same HTTP 402 flow our paid APIs run all day, pointed at a t-shirt.

Why bolt machine payments onto a t-shirt store

Partly because it’s the funniest possible integration test. We spend all day writing about agents paying for API calls — structured data, deterministic responses, sub-cent prices. A physical hoodie is the exact opposite of all that, which makes it the honest stress test: order created, pay route answers HTTP 402 with the payment requirements, USDC settles on Base, the store answers 200, and dropship fulfillment kicks off automatically. No human in the loop until someone opens a mailbox. If the rails can sell a mug, they can sell anything.

And partly because the designs deserved to exist. “sudo pay.” “402 → OK.” A robot ordering coffee: GET /coffee → 402 → 200. A robot buying its tired human a coffee. The kind of jokes that need zero explanation if you’ve read this blog and infinite explanation if you haven’t — which is what merch is for.

A few of the shelves

Related reading: what running 500+ paid endpoints taught us about the rails this store runs on.