Overview
Stellar CCTP contracts run on Soroban, Stellar’s smart contracts platform. CCTP
message fields use 32-byte address encodings. CCTP treats mintRecipient as a
contract address. If the recipient is a Stellar user or
muxed
account instead, hook data can carry a forwardRecipient strkey so the
forwarder can send funds to that address.
To align with Stellar address encoding while keeping parity with EVM and other
non-EVM blockchains, CCTP uses three contracts:
TokenMessengerMinter: consolidates the responsibilities of
TokenMessengerV2 (burn + send) and TokenMinterV2 (receive + mint). On
mint, mintRecipient is treated as a contract address and hooks supply the
forwardRecipient when needed.MessageTransmitter: provides the messaging layer that emits or receives
attested messages and delivers them to TokenMessengerMinter (including
receive_message for forwarder flows).CctpForwarder: receives minted USDC and forwards it to forwardRecipient in
hook data.
Testnet contract addresses
CCTP interface
TokenMessengerMinter: initiates crosschain burns and mints tokens upon
attested message receipt.MessageTransmitter: emits messages, verifies attestations, and routes
verified messages to the recipient contract.CctpForwarder: completes mint and forward in one transaction when hook data
supplies a forwardRecipient strkey.
TokenMessengerMinter interface
The TokenMessengerMinter contract consolidates the roles of both
TokenMessengerV2 and TokenMinterV2 found on EVM chains. It handles USDC
burns, message emission, and token minting once crosschain messages are attested
by Circle’s Iris service. On Stellar it assumes mintRecipient is a contract.
Account recipients use CctpForwarder and hook-qualified forwardRecipient
bytes.
| Function | Description | Notes |
|---|
deposit_for_burn | Burns USDC and emits a crosschain message for minting on another domain. | Standard CCTP transfer initiation. |
deposit_for_burn_with_hook | Same as deposit_for_burn, but attaches custom metadata (hook_data). | Used for programmable transfers and Stellar forwarding. |
handle_receive_finalized_message | Mints USDC upon receiving a fully finalized message. | Called by MessageTransmitter. |
handle_receive_unfinalized_message | Processes partially finalized (“Fast Burn”) messages. | Enables faster crosschain transfers. |
message_body_version | Returns supported message format version. | Used for compatibility checks. |
local_message_transmitter | Returns the linked MessageTransmitter address. | Must match configured domain transmitter. |
MessageTransmitter interface
The MessageTransmitter contract provides the core messaging layer for CCTP on
Stellar. It is responsible for emitting, receiving, and validating crosschain
messages, enforcing attestation rules, and ensuring message uniqueness.
| Function | Description | Notes |
|---|
send_message | Sends a crosschain message with specified domain, recipient, and message body. | Core function for outgoing CCTP messages. |
receive_message | Validates a message and its attestation; delivers message body to the recipient. | Called by an offchain relayer (or by CctpForwarder in the forwarder flow) with an attestation from Circle. |
get_max_message_body_size | Returns the maximum allowed message size. | Used by offchain components for validation. |
is_nonce_used | Checks if a message nonce has been processed already. | Prevents message replay. |
get_local_domain | Returns this contract’s domain ID. | Expected to be 27 for Stellar. |
get_version | Returns protocol version supported by this transmitter. | Used by Iris attestation service. |
CctpForwarder interface
The CctpForwarder contract calls receive_message on MessageTransmitter,
takes the mint, and transfers USDC to forwardRecipient parsed from
hook_data. See Hook format for
details.
| Function | Description | Notes |
|---|
mint_and_forward(message: Bytes, attestation: Bytes) | Verifies message and attestation. Runs receive_message so USDC mints to CctpForwarder. Sends USDC to forwardRecipient from hooks. | Atomic, any failure reverts. |
The CctpForwarder flow is non-custodial. mint_and_forward mints to this
contract and pays forwardRecipient in one atomic Soroban invocation. Circle
does not take custody of the minted balance in between.
