CCIP v2.0.0 USDCTokenPoolProxy API Reference

Summary

USDCTokenPoolProxy is a forwarding pool that routes USDC lockOrBurn and releaseOrMint flows to specific child pool implementations.

It:

Implements [IPoolV1V2](/ccip/evm/api-reference/v2.0.0/i-pool-v1-v2)
Does not inherit [TokenPool](/ccip/evm/api-reference/v2.0.0/token-pool)
Forwards calls using call
Selects child pools based on:
- LockOrBurnMechanism
- Version tag prefix embedded in sourcePoolData

Supported routing targets:

CCTP v1 pool
CCTP v2 pool
CCTP v2 with CCV
Siloed lock-release pool

Contract

chains/evm/contracts/pools/usdc/USDCTokenPoolProxy.sol

Import

import {USDCTokenPoolProxy} from "chainlink-ccip/chains/evm/contracts/pools/usdc/USDCTokenPoolProxy.sol";

Target + upgrade model

This contract is not a storage proxy.

All calls are forwarded via call
No delegatecall is used
State is isolated from child pools
Owner can update child pool addresses

Inheritance

contract USDCTokenPoolProxy
  is IPoolV1V2,
     Ownable2StepMsgSender,
     ITypeAndVersion

typeAndVersion

string public constant override typeAndVersion =
  "USDCTokenPoolProxy 2.0.0-dev";

State

Constants

uint16 internal constant WAIT_FOR_FINALITY = 0;

Immutables

IERC20 internal immutable i_token;
IRouter internal immutable i_router;
ICrossChainVerifierResolver internal immutable i_cctpVerifier;

Storage

mapping(uint64 => LockOrBurnMechanism)
  internal s_lockOrBurnMechanism;

address internal s_cctpV1Pool;
address internal s_cctpV2Pool;
address internal s_cctpV2PoolWithCCV;
address internal s_siloedLockReleasePool;

address internal s_feeAggregator;

Structs & Enums

LockOrBurnMechanism

enum LockOrBurnMechanism {
  NONE,
  CCTP_V1,
  CCTP_V2,
  CCTP_V2_CCV,
  LOCK_RELEASE
}

PoolAddresses

struct PoolAddresses {
  address cctpV1Pool;
  address cctpV2Pool;
  address cctpV2PoolWithCCV;
  address siloedLockReleasePool;
}

External API (forwarded surface)

lockOrBurn (V1)

function lockOrBurn(
  Pool.LockOrBurnInV1 calldata lockOrBurnIn
)
  public
  override
  returns (Pool.LockOrBurnOutV1 memory)

Requires caller equals i_router.getOnRamp(...)
Routes according to s_lockOrBurnMechanism
Reverts if no mechanism configured

lockOrBurn (V2)

function lockOrBurn(
  Pool.LockOrBurnInV1 calldata lockOrBurnIn,
  uint16 blockConfirmationRequested,
  bytes memory tokenArgs
)
  public
  override
  returns (Pool.LockOrBurnOutV1 memory, uint256)

Supports CCV and LOCK_RELEASE mechanisms
Resolves outbound verifier via i_cctpVerifier

releaseOrMint (V1)

function releaseOrMint(
  Pool.ReleaseOrMintInV1 calldata releaseOrMintIn
)
  public
  override
  returns (Pool.ReleaseOrMintOutV1 memory)

Requires caller equals authorized OffRamp
Extracts version tag from sourcePoolData
Routes accordingly

releaseOrMint (V2)

function releaseOrMint(
  Pool.ReleaseOrMintInV1 calldata releaseOrMintIn,
  uint16 blockConfirmationRequested
)
  public
  override
  returns (Pool.ReleaseOrMintOutV1 memory)

Supports CCV and LOCK_RELEASE
Routes based on version tag

getFee

Delegates to underlying pool supporting V2.

updatePoolAddresses

function updatePoolAddresses(
  PoolAddresses calldata pools
)
  external
  onlyOwner

updateLockOrBurnMechanisms

function updateLockOrBurnMechanisms(
  uint64[] calldata chainSelectors,
  LockOrBurnMechanism[] calldata mechanisms
)
  external
  onlyOwner

withdrawFeeTokens

function withdrawFeeTokens(
  address[] calldata feeTokens
) external

Permissionless. Forwards to FeeTokenHandler.

Events

event LockOrBurnMechanismUpdated(
  uint64 indexed remoteChainSelector,
  LockOrBurnMechanism mechanism
);

event PoolAddressesUpdated(PoolAddresses pools);

Errors

error AddressCannotBeZero();
error ChainNotSupportedByVerifier(uint64 remoteChainSelector);
error InvalidLockOrBurnMechanism(LockOrBurnMechanism mechanism);
error InvalidMessageVersion(bytes4 version);
error MismatchedArrayLengths();
error NoLockOrBurnMechanismSet(uint64 remoteChainSelector);
error CallerIsNotARampOnRouter(address caller);
error TokenPoolUnsupported(address pool);
error MustSetPoolForMechanism(
  uint64 remoteChainSelector,
  LockOrBurnMechanism mechanism
);

Security model

Owner controls routing configuration.
Router enforces ramp authorization.
No delegatecall — child pool storage remains isolated.
Version tag must match expected child pool semantics.
Misconfiguration can halt lane until corrected.

CCIP v2.0.0 USDCTokenPoolProxy API Reference

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