> ## Documentation Index > Fetch the complete documentation index at: https://developers.circle.com/llms.txt > Use this file to discover all available pages before exploring further. # CCTP for non-USDC contract reference > CCTP for non-USDC contracts, types, errors, and non-obvious behaviors integrators need. The following tables index contracts, types, errors, and sentinels, and document behaviors that aren't obvious from reading the source. For contract addresses, see [Contract Addresses](/cctp/expanded-assets/references/contract-addresses). ## Contracts | Contract | Purpose | | --------------------------- | -------------------------------------------------------------------------------------------------------------------------------- | | `CrossChainTokenService` | Singleton entry point on each domain. Registers tokens, deploys remote token contracts, and routes crosschain transfers. | | `TokenManager` | Deployed per token on each domain. Moves tokens during transfers; enforces rate limit, max transfer amount, and pause. | | `CrossChainToken` | ERC-20 with `ERC20Permit` deployed for natively crosschain tokens. Holders call `crossChainTransfer` directly. | | `CrossChainTokenExecutable` | Optional abstract helper for destination-domain hook receivers. Integrators can implement `executeWithCrossChainToken` directly. | | `IDenylistProvider` | Interface for service-level and per-token denylist providers. One view: `isDenylisted(address)`. | ## Types ### `QuoteClaim` Passed to every payable entrypoint to attach a signed fee quote and a refund address. ```solidity Solidity theme={null} struct QuoteClaim { bytes signedQuote; address payable refundAddress; } ``` * `signedQuote`: version-prefixed, ABI-encoded fee quote returned by the Iris fee-quote endpoint (`POST /v1/quote/cctpx/{tokenId}/{sourceDomain}/{destinationDomain}`). Pass the bytes value verbatim. * `refundAddress`: receives fee refunds. Set to `address(0)` to opt out of refund attribution. Non-zero values are screened against the USDC denylist on collection; the call reverts if denied. ### `DeploymentParams` Passed when registering or deploying a token. ```solidity Solidity theme={null} struct DeploymentParams { TokenManagerType tokenManagerType; bytes tokenManagerOwner; bytes tokenManagerOperator; bytes tokenOwner; bytes tokenMinter; uint256 initialSupply; TokenManagerSettings tokenManagerSettings; } struct TokenManagerSettings { uint256 rateLimit; uint256 maxTransferAmount; } ``` Address fields are `bytes` rather than `address` so the struct can carry non-EVM addresses for non-EVM domains. Some deployments omit `initialSupply` from the onchain ABI (for example current sandbox `registerCustomToken`). Encoding a field the contract does not expect produces an empty revert. Always verify the live ABI or function selector before copying struct layouts from docs. ### `TokenManagerType` ```solidity Solidity theme={null} enum TokenManagerType { NATIVE_CROSSCHAIN_TOKEN, // 0 BURN_MINT, // 1 LOCK_UNLOCK // 2 } ``` See [Token manager types](/cctp/expanded-assets/concepts/architecture#token-manager-types) for when each applies. ### `ConnectionType` ```solidity Solidity theme={null} enum ConnectionType { OWNERLESS, CUSTOM } ``` Distinguishes the two integration models. See [Ownerless and custom tokens](/cctp/expanded-assets/concepts/ownerless-vs-custom-tokens). ## Errors Integrators should monitor for these reverts: | Error | Source | Meaning | | --------------------------------------------------------------------------- | ------------------------ | ---------------------------------------------------------------------------------------------- | | `TokenNotRegistered(bytes32 tokenId)` | `CrossChainTokenService` | `resolveTokenManager` or `resolveTokenAddress` called with a `tokenId` that has no deployment. | | `HookDataExecutionFailed(bytes32 tokenId, address recipient, bytes reason)` | `CrossChainTokenService` | Recipient's hook reverted, or returned a value other than the `EXECUTE_SUCCESS` sentinel. | | `DenylistedAddress(address account)` | `CrossChainTokenService` | Service-level denylist rejected `msg.sender`, `tx.origin`, or the inbound recipient. | | `AccountDenylisted(address account)` | `CrossChainToken` | Per-token denylist rejected `from`, `to`, or the spender on an ERC-20 movement. | ## Sentinels ### `EXECUTE_SUCCESS` ```solidity Solidity theme={null} bytes32 constant EXECUTE_SUCCESS = keccak256("circle-cctpx-execute-success"); ``` The value that `executeWithCrossChainToken` must return. The service verifies this on every hook call. Implement the public entrypoint on your receiver, restrict `msg.sender` to the local `CrossChainTokenService`, and return this sentinel. See [Build a hook receiver](/cctp/expanded-assets/howtos/build-hook-receiver). When the contracts are open-sourced, an optional `CrossChainTokenExecutable` base can wrap the same pattern (external entrypoint returns the sentinel; subclasses override an internal hook). Until then, implement the write ABI directly. ## Non-obvious behaviors These behaviors aren't apparent from reading the source but commonly trip up integrators. ### `approve` goes to the `TokenManager`, not the service For `BURN_MINT` and `LOCK_UNLOCK` transfers, the source token is moved by the per-token `TokenManager`. ERC-20 approvals must target the `TokenManager` address (returned by `resolveTokenManager(tokenId)`), not the `CrossChainTokenService`. ### `destinationAddress` is packed address bytes, not ABI-encoded `crossChainTransfer` takes `destinationAddress` as `bytes`. On EVM, pass the raw 20-byte address (`abi.encodePacked(recipient)` / `encodePacked(["address"], [recipient])`). Do **not** use `abi.encode` / `encodeAbiParameters([{ type: "address" }], …)`, which produces a 32-byte left-padded word and breaks destination delivery. This is separate from application `hookData`, which may still be ABI-encoded. ### Custom `tokenId` uses `customTokenDeploySalt` For custom tokens, the `tokenId` is `crossChainTokenId(deployer, customTokenDeploySalt(deployer, salt))`. Calling `crossChainTokenId(deployer, salt)` alone yields a different id. Native crosschain tokens use `crossChainTokenId(deployer, salt)` directly. ### `resolveTokenManager` and `resolveTokenAddress` revert on miss Both revert with `TokenNotRegistered(tokenId)` when the predicted address has no deployed code. They do not return `address(0)`. To probe for existence without throwing, wrap the call in `try`/`catch` or check `extcodesize` on the deterministic CREATE3-predicted address. ### `CrossChainToken` denylist provider replaces, it does not chain `CrossChainToken` holds a single denylist provider slot. Calling `updateDenylistProvider` overwrites the previous value rather than adding to it. To combine multiple lists, deploy a composite provider that internally calls each upstream. The service-level denylist still runs in addition to the per-token layer. ### Ownerless deploys inherit Circle's denylist provider When `deployRemoteOwnerlessToken` lands on a remote domain, the new `CrossChainToken`'s `denylistProvider` is initialized to the service's provider. ### `tokenManagerOwner`, `tokenManagerOperator`, and related fields are `bytes` The fields are typed `bytes` instead of `address` so the same struct works for non-EVM domains in the future. On EVM, pack the address with `abi.encodePacked(addr)` / `encodePacked(["address"], [addr])` (20 bytes). Do not use `encodeAbiParameters([{ type: "address" }], [addr])`, which ABI-pads to 32 bytes and is not equivalent. For an **existing** ERC-20 registered with `registerCustomToken`, pass empty bytes (`0x`) for `tokenOwner` and `tokenMinter`; grant the `TokenManager` minter role on the token in a separate step. ### `sourceAddress` in hook callbacks is `bytes` Same reason as the deployment params: the hook signature carries the source address as `bytes` so receivers can decode senders from non-EVM blockchains. ### Hook execution can be reorged on fast transfers When a hook executes with `finalityThresholdExecuted < 2000`, the source blockchain transaction is still pre-finality and could be reorged. Receivers that opt into fast hook execution must design their logic to tolerate rollback by deferring irreversible side-effects until finality is confirmed. ## Function index ### `CrossChainTokenService` | Group | Functions | | ------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Crosschain transfer | `crossChainTransfer`, `transmitCrossChainTransfer` | | Resolve and inspect | `resolveTokenManager`, `resolveTokenAddress`, `getOwnerlessTokenId`, `crossChainTokenId`, `customTokenDeploySalt`, `ownerlessTokenDeploySalt`, `isTrustedDomain` | | Trust and limits | `addTrustedDomain`, `removeTrustedDomain`, `setRateLimits` | | Denylist | `denylistProvider`, `setDenylistProvider`, `initializeDenylistProvider` | | Roles and upgrade | `feeService`, `messageTransmitter`, `operator`, `transferOwnership`, `acceptOwnership`, `pause`, `unpause`, `upgradeToAndCall` | ### `TokenManager` | Group | Functions | | ----------------- | ------------------------------------------------------------------------------------------ | | Transfer limits | `setRateLimit`, `setMaxTransferAmount`, `setRateLimitWindow` | | Pause | `pause`, `unpause`, `updatePauser` | | Implementation | `upgradeToCustomImplementation`, `resetToDefaultImplementation` | | Ownership | `transferOwnership`, `acceptOwnership`, `transferOperatorship` | | Circle assignment | `assignOwnership`, `assignOperatorship` (only callable on ownerless `TokenManager`s) | | Service-only | `takeToken`, `giveToken` (called by `CrossChainTokenService`; not callable by integrators) | ### `CrossChainToken` | Group | Functions | | ----------------- | ------------------------------------------------------------------------------------------------------------------- | | Crosschain | `crossChainTransfer`, `crossChainTransferFrom` | | Mint and burn | `mint`, `burn`, `burnFrom`, `addMinter`, `removeMinter`, `transferMintership` | | Denylist | `denylistProvider`, `isDenylisted`, `updateDenylistProvider` | | Implementation | `upgradeToCustomImplementation`, `resetToDefaultImplementation` | | Ownership | `transferOwnership`, `acceptOwnership` | | Circle assignment | `assignOwnership`, `assignOperatorship` (only callable on ownerless `CrossChainToken`s) | | ERC-20 surface | Standard ERC-20 (`transfer`, `transferFrom`, `approve`, `allowance`, `balanceOf`, `totalSupply`) plus `ERC20Permit` | ### `CrossChainTokenExecutable` Optional helper (when published). Integrators may instead implement the public entrypoint directly. | Group | Functions | | ------------------- | --------------------------------------------------------------------- | | Hook entry point | `executeWithCrossChainToken` (returns `EXECUTE_SUCCESS`) | | Hook implementation | `_executeWithCrossChainToken` (override when using the abstract base) |