Machine payments, documented.

Aeron is a payment rail for software that buys things without a human present. A seller answers an HTTP request with 402 Payment Required and a price; a buyer signs an authorization for exactly that amount; the Aeron facilitator checks it and settles it on Robinhood Chain. The whole exchange is two HTTP round trips and one on-chain transfer.

Nothing here needs an account, an API key, or a card. Sellers need an address that can receive USDG. Buyers need USDG — and not ETH, because Aeron’s relayer submits the transaction and pays the gas.

Constants

Every service on the rail is configured with the same five values. Copy them exactly; the facilitator refuses anything else.

Network

eip155:4663

Chain

Robinhood Chain mainnet, chain id 4663

Asset

0x5fc5360d0400a0fd4f2af552add042d716f1d168 (USDG, 6 decimals)

Scheme

exact · x402Version 1

Facilitator

https://x402.aeron.sh

Explorer

robinhoodchain.blockscout.com

Prices are quoted in atomic units of USDG, so six decimals: "2000" is $0.002 and "1000000" is $1.00.

Pick a side

How one call works

1. The agent calls your endpointwith no payment header. You answer 402 with an accepts[] array: your price, your address, the asset, the network.
2. The agent signsan EIP-3009 TransferWithAuthorization for exactly that amount and retries the same request with an X-PAYMENT header.
3. You verifyby posting the payload and your requirements to POST /verify. The facilitator checks the signature, the nonce, the time window, and the payer’s balance — all against the chain.
4. You do the work.Verification has already proved the authorization is valid, unspent, and funded, so this is the safe moment to spend money on the caller’s behalf.
5. You settlewith POST /settle. Aeron’s relayer submits the transfer and pays the gas. USDG moves payer → your address in one transaction; nobody custodies it in between.
6. You answerwith the result and an X-PAYMENT-RESPONSE header carrying the transaction hash, which is the buyer’s receipt.

What is running

Service	Host	What it is
Facilitator	x402.aeron.sh	Verifies and settles x402 payments. Reference
Inference	inference.aeron.sh	OpenAI-compatible gateway, paid per call. Docs
Marketplace	market.aeron.sh	Directory of paid endpoints. Docs
RWA data	rwa.aeron.sh	Tokenized-stock prices and holdings. Docs
Aeronscan	scan.aeron.sh	Open explorer of agent payments. Docs
Wallet	npm: aeron-wallet	The buyer side, run on your own machine. Docs

Each one answers GET /healthz. If something here disagrees with what a service returns, the service is right.

Source

The two pieces a stranger has to trust are open source and MIT licensed: aeron-facilitator, which holds the settlement path, and aeron-wallet, which holds the buyer’s key. Neither has been audited. Both move real money on mainnet — read them before you point anything valuable at them.