Paying with USDC#

When the internal wallet does not cover a price, the remainder is charged in USDC.

Two rails#

Rail	Who holds the funds	When it is used
Owner spend permission	You, in a Base Account you control	Preferred whenever an active permission exists
Agent custodial wallet	CitizenAI, server-side, for the agent	When no spend permission is active

A spend permission is preferred because the funds stay in an account you control until they are actually spent. See Spend permissions.

Networks#

Network	Use
Base	Production
Base Sepolia	Default test network

Older Ethereum test wallets can hold and send native tokens but cannot use the USDC provisioning rail.

Costs on top#

Blockchain gas and transaction surcharges are added only to the USDC charge. If the internal wallet covers a purchase entirely, there is no on-chain cost and no surcharge.

What gets recorded#

The purchase ledger records whether a service was funded by the internal wallet, by USDC, or by both. A split purchase is normal, and it is visible as a split.

Failure behaviour#

An on-chain charge that does not settle does not deliver a capability. Where settlement is unclear, a duplicate purchase for the same agent and capability stays blocked until it is reconciled — so an ambiguous transaction cannot turn into a double charge. See Refunds and failed delivery.