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EURC and cirBTC use the same unified balance, transfer flow, and API as USDC. Each asset keeps its own balance, and a transfer must use the same asset on the source and the destination. Existing USDC integrations are unchanged. The following sections cover only what differs from USDC.

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Balances and transfers by asset

Gateway tracks a separate balance for each asset. When you deposit EURC, Gateway credits a EURC balance, and a cirBTC deposit credits a cirBTC balance. Gateway never converts between assets. A transfer burns an asset on the source blockchain and mints the same asset on the destination blockchain, so both blockchains must support the asset.

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Supported blockchains by asset

Each asset is available on a subset of the Gateway blockchains. cirBTC is not available on Solana. EURC is also issued on Cronos and Stellar, but Gateway is not offered on those blockchains. For token addresses, see EURC contract addresses and cirBTC contract addresses. For the USDC matrix, see Gateway supported blockchains. The Gateway Wallet and Gateway Minter contracts are the same as for USDC. For their addresses, see Gateway contract addresses.

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Asset selection in API requests

The /v1/balances and /v1/deposits requests select the asset with a token field. The accepted values are USDC, EURC, and cirBTC. The casing must match exactly, so the API rejects CIRBTC. When token is omitted, Gateway uses USDC. The following example queries a EURC balance on Arc Testnet (domain 26):
The /v1/transfer and /v1/estimate requests identify the asset through token contract addresses instead. Each burn intent carries a sourceToken and a destinationToken, which hold the address of the asset on the source and destination blockchains. On Solana, destinationRecipient must be the token account for the asset you transfer.

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Decimals

Each asset uses its own number of decimal places. Amounts, fees, and gas values are all expressed in the asset’s atomic units.
Treating cirBTC as a 6-decimal asset makes amounts 100 times too large or too small. Decimals are specific to each asset, so the USDC value doesn’t carry over.

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Fees

Gateway charges fees and gas in the token you transfer. A cirBTC transfer pays its fees in cirBTC, and maxFee is in that token’s atomic units. The /v1/estimate response is the authoritative fee for a transfer. For the fee model, see EURC and cirBTC fees.

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Forwarding Service

The Forwarding Service supports USDC, EURC, and cirBTC. For details, see Forwarding Service.

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Nanopayments

Nanopayments extends to EURC and cirBTC on EVM blockchains only. Non-USDC assets require EIP-3009 version 2 authorizations. For the version 2 signing details, see EIP-3009 signing. The /x402/supported endpoint returns the live list of supported assets for each network.

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Deposit and withdrawal safety

The safety rules for USDC apply to every asset. A direct ERC-20 transfer to the Gateway Wallet contract loses the funds, so deposits must go through the Gateway deposit methods. Trustless withdrawal and its delay also apply to every asset.