How to turn a testnet x402 project into one on Base mainnet in 3 minutes

Product & onchain AI @ Coinbase, Founder @ Vanderbilt Blockchain, EPF Fellow and SSF Enthusiast

lincoln can you explain what the x402 facilitator does?

still have not read a coherent explanation

It verifies the payment isn’t coming from a sanctioned address then settles it onchain and pays the tx fee

The idea is to mitigate an API seller’s need to know or integrate anything related to crypto

but what's the flow?

also, doesn't USDC already not allow sanctioned addresses to move funds? I thought the base sequencer just forbid transactions touching sanctioned addresses?

totally

im building a similar flow right now, but assuming you've already IP banned NK / Iran from your backend, the flow is:

- user hits backend
- backend returns payment required
- user's client sends payment, and then submits transaction hash
- backend client grabs the hash, spawns a job to wait for the receipt, and makes sure it's in a finalized block before triggering a local callback. (in my case im looking for the appropriate ERC20 Transfer event).

a lot of this is spiritually modeled by x402 today, but instead of a facilitator you just check settlement in local infra code instead

User hits backend with request

Backend says 402 payment required, send me X USDC

User constructs signature, signs it, then sends it back 

Facilitator, the middleware piece, picks it up and runs the verify/settle

Once the transaction settles, facilitator lets the backend know and backend responds to user 

x402 meant for more than base and USDC so ofac check is future proof 

If you’re an AI dev you don’t want to touch anything related to checking onchain data that you don’t have to