CCIP v2.0.0 CCTPMessageTransmitterProxy API Reference

Summary

CCTPMessageTransmitterProxy is a forwarding proxy that restricts access to Circle’s IMessageTransmitter.receiveMessage while keeping a stable onchain address.

It:

Resolves and stores the local MessageTransmitter at construction time.
Restricts receiveMessage calls using [AuthorizedCallers](/ccip/evm/api-reference/v2.0.0/authorized-callers).
Forwards calls using call.
Does not use delegatecall.

This proxy is used to stabilize the caller address required by CCTP integrations while allowing outer systems to upgrade independently.

Contract

chains/evm/contracts/pools/USDC/CCTPMessageTransmitterProxy.sol

CCTPMessageTransmitterProxy.sol

Check out the complete code on GitHub.

Import

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

Target + upgrade model

The underlying transmitter address is resolved once in the constructor via:
```
tokenMessenger.localMessageTransmitter()
```
The resolved transmitter is stored as an immutable.
No delegatecall is used.
Calls are forwarded via standard call.
Only authorized callers may invoke receiveMessage.

This is not an upgradeable storage proxy.

Inheritance

AuthorizedCallers
ITypeAndVersion

typeAndVersion

string public constant override typeAndVersion =
  "CCTPMessageTransmitterProxy 2.0.0";

State

Constants

None declared.

Immutables

IMessageTransmitter public immutable i_cctpTransmitter;

Resolved at construction time.

Storage

No additional storage declared.

Allowlist state is inherited from AuthorizedCallers.

Constructor

constructor(
  ITokenMessenger tokenMessenger
)
  AuthorizedCallers(new address)

Behavior:

Resolves transmitter:

tokenMessenger.localMessageTransmitter()

Reverts with:
```
error TransmitterCannotBeZero();
```
if the resolved transmitter is address(0).
Stores the transmitter in i_cctpTransmitter.

External API (forwarded surface)

receiveMessage

function receiveMessage(
  bytes calldata message,
  bytes calldata attestation
)
  external
  onlyAuthorizedCallers
  returns (bool success)

Behavior:

Enforces onlyAuthorizedCallers.

Forwards call to:

i_cctpTransmitter.receiveMessage(message, attestation);

Returns the boolean result from the underlying transmitter.

Events

No events declared in this contract.

Events from AuthorizedCallers may be emitted during allowlist updates.

Errors

error TransmitterCannotBeZero();

Inherited errors from AuthorizedCallers may also surface.

Security model

Only allowlisted addresses may call receiveMessage.
Underlying transmitter is immutable and cannot be changed post-deployment.
No delegatecall; no storage collision risk.
If allowlist is misconfigured, legitimate CCTP flows will fail.
Transmitter resolution is validated at deployment.

CCIP v2.0.0 CCTPMessageTransmitterProxy API Reference

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