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Integrating CCTP for non-USDC when you already know CCTP for USDC is mostly a matter of switching entry contracts and adjusting for a different fee model. The following sections document the key differences for developers integrating pre-registered or third-party-registered tokens.

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What stays the same

This layer shares CCTP’s core infrastructure:
  • Message transmitter: Both use MessageTransmitterV2. Attestations are delivered to the same contract on the destination.
  • Attestation service: Both use Iris (Circle’s attestation API). Polling /v2/messages/{sourceDomain} works the same way.
  • Finality thresholds: minFinalityThreshold = 2000 for standard, 1000 for fast. Same semantics as CCTP fast transfers.
  • Hooks: Available on both protocols. The CrossChainTokenExecutable interface is analogous to CCTP’s IMessageHandlerV2.

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Key integration differences

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Entry contract and approval target

For CCTP, you approve TokenMessengerV2 and call depositForBurn. For non-USDC transfers, resolve the per-token TokenManager address from CrossChainTokenService using resolveTokenManager(tokenId), approve that address, then call crossChainTransfer on the service. Approving the service contract directly does not work; the approval must go to the TokenManager.

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Fee model

CCTP deducts its fee from the transferred USDC amount; the recipient receives slightly less than the sender transferred. Non-USDC fees are paid in native gas on the source blockchain at transfer time, so the recipient receives the full transferred amount.

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Forwarding

CCTP forwarding (auto-delivery of the destination mint) is compulsory whenever the forwarding service is used. For non-USDC transfers, forwarding is opt-in: include a FORWARD entry in the requests array when you fetch the Iris fee quote. Transfers that omit FORWARD require you or the recipient to submit receiveMessage on the destination MessageTransmitterV2 manually.

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Allowance pools for fast transfers

Both protocols support fast transfers, but they track allowance separately. USDC fast transfers consume the USDC allowance; non-USDC fast transfers consume a per-token allowance maintained by Circle. Check the per-token allowance using GET /v2/cctpx/allowances before initiating a fast transfer; if the allowance is insufficient or FX pricing is not configured for the token, the quote returns FX_SYMBOL_NOT_CONFIGURED and the fast transfer cannot proceed.

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Token prerequisite

USDC works on CCTP without setup. Non-USDC transfers require the token to be registered before it can be transferred. If you are using a pre-registered token (such as EURC), the token is already available and no registration step is needed on your end. To check which tokens are pre-registered, see Supported blockchains.