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This guide provides a summary of the breaking changes when migrating from Cross-Chain Transfer Protocol (CCTP) V1 to V2. CCTP V2 introduces enhancements including Fast Transfer, Hooks features, and improved API endpoints, but requires updating your integration due to breaking changes. Arc App Kit’s Bridge capability can help simplify your migration to CCTP V2. See the Migrating with App Kit section for more information.

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V1 deprecation

Circle is deprecating CCTP V1 to focus on the newer version, which is upgradable and provides a faster, more secure, and more robust crosschain experience across a wider network of blockchains.

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Naming changes

CCTP V2 is now referred to as CCTP (except in this document). The V1 version of CCTP is now CCTP V1 (Legacy).

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Deprecation timeline

CCTP V1 will be phased out over the course of 10 months beginning in July 2026. CCTP V2 contracts are available on all CCTP V1 chains except for Aptos, Noble, and Sui. Aptos and Sui will be supported by V2 before the phase out begins. Circle is working with Noble and Cosmos ecosystem teams on an intermediate solution to route USDC flows to and from Noble.

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Access to funds

You will not lose access to funds during the V1 phase out. All pending redemptions will remain available as CCTP V1 (legacy) begins its phase out. Circle will maintain minter allowances greater than the total of pending attestations, ensuring every redemption can be processed before V1 contracts are fully paused. The deprecation process is designed to wind down activity gradually, message limits will tighten over time until no new burns can be initiated, bringing transfer volume to zero before contracts are fully paused.

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Additional resources

In addition to this guide and Arc App Kit, you can contact the Circle team on the BuildOnCircle Discord for questions and migration support.

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Summary of breaking changes

The latest version of CCTP introduces architectural changes that make it incompatible with V1 integrations. You must update your implementation to use the new contracts, APIs, and transfer speeds. Additionally, the overall flow of the protocol has been streamlined, which means you need to update your integration to use the new functions.
  • Contracts are deployed at different addresses than V1 contracts. You should update your integration to point to the new contract addresses.
  • Contract interfaces have changed. Importantly, the depositForBurn function now takes additional parameters. You should update your integration to use the new ABIs and contract calls.
  • CCTP now allows you to specify a transfer speed. The finalityThreshold parameter specifies whether the transfer should be a Fast Transfer or a Standard Transfer.
  • You no longer need to extract the message from the onchain transaction to fetch an attestation. Instead, you can call the new /v2/messages/{sourceDomainId} endpoint with the transaction hash to get the message and attestation in a single call.
  • API endpoints have changed. The new /v2/ endpoints have different functions than the old /v1/ endpoints. You should update your integration to use the new endpoints. Review the CCTP API reference for details on the changes to the CCTP offchain API.
  • Fees have been introduced. Fast Transfer has a variable fee based on the source chain. You should update your integration to account for the new fees.