x402 negotiation

How unpaid unlocks advertise payment — and how arcdot. settles on Arc.

What you get on 402

JSON error.payment + x402
Header PAYMENT-REQUIRED — base64 JSON (x402 v2 shape)
Convenience headers X-Payment-Wallet, X-Payment-Amount (wei), X-Payment-Decimals: 18

Settlement scheme

Advertised as ArcDotPromptGateway: on-chain depositPayment on Arc Mainnet, then retry with X-Arc-Tx-Hash, X-Arc-Address, and X-Arc-Signature.

This is not Circle GatewayWalletBatched / EIP-3009 facilitator signing. Agents that only speak that path need the arcdot. deposit loop (or CLI agent:pay).

Amounts

X-Payment-Amount and x402 accepts[].amount are 18-decimal wei of USDC on Arc. See Payment on Arc.