Stable402

Reference implementations for x402, AP2, and agentic payment protocols — built in public on Cloudflare Workers.

What is Stable402?

x402 is the HTTP 402 payment standard for machine-to-machine commerce. An AI agent receives a 402 Payment Required response, reads the PAYMENT-REQUIRED header, signs a USDC transfer on Base, and retries — no accounts, no API keys, no human in the loop.

Stable402 fills the gap between protocol specs and production-ready code. Every POC implements the official vendor quickstart, ports it to Cloudflare Workers, then bridges across the ecosystem. Each build is a newsletter issue. Each build lights up a station on the Transit Map.

The 10 POCs

POC 01

x402 Worker Middleware

A Cloudflare Worker that gates a JSON API behind x402. Settlement on Base Sepolia via Coinbase CDP facilitator.

Live

POC 02

paidTool MCP Server

Cloudflare Agents SDK MCP server with x402-gated tools. $0.01 per tool invocation. Protocol comparison data from D1.

Planned

POC 03

AP2 ↔ x402 Bridge

Google’s A2A x402 Extension — AP2 mandate flow where the payment leg settles via x402 on Base instead of card rails.

Planned

POC 04

Stripe x402 Facilitator

Stripe as an x402 facilitator with fiat off-ramp. Bridges crypto settlement to card-based payment flows.

Planned

POC 05

Multi-Chain Settlement

Base vs Solana x402 settlement comparison — same protocol, different chains, documented latency and cost differences.

Planned

POC 06

Signed Agents + x402

Cloudflare Signed Agents dual-gate — commerce (x402 payment) and compliance (agent identity) in a single handshake.

Planned

POC 07

Circle Nanopayments

Aggregate sub-cent x402 transactions via Circle Nanopayments. Per-token streaming payments with USDC.

Planned

POC 08

x402 Sandbox

Interactive x402 sandbox built on Durable Objects. Test payment flows, inspect headers, replay transactions in the browser.

Planned

POC 09

Pay-Per-Crawl

Cloudflare AI Crawl Control + x402. Publishers monetize AI crawler access with per-request USDC micropayments.

Planned

POC 10

Transit Map

Beck-style interactive map of the agentic payments ecosystem — every protocol, facilitator, and settlement chain as a station.

Planned

Built on: Cloudflare Workers · Cloudflare Agents SDK · Base Sepolia · x402 · AP2 · Astro 6

For consulting or sponsorship: Leo@Stable402.com