Struct MessageHeader 

pub struct MessageHeader {
    pub version: u32,
    pub source_domain: DomainId,
    pub destination_domain: DomainId,
    pub nonce: FixedBytes<32>,
    pub sender: FixedBytes<32>,
    pub recipient: FixedBytes<32>,
    pub destination_caller: FixedBytes<32>,
    pub min_finality_threshold: u32,
    pub finality_threshold_executed: u32,
}

CCTP v2 Message Header

The message header contains metadata about cross-chain messages, including source/destination domains, finality requirements, and routing.

Format

• version: uint32 (4 bytes)
• sourceDomain: uint32 (4 bytes)
• destinationDomain: uint32 (4 bytes)
• nonce: bytes32 (32 bytes) - unique identifier assigned by Circle
• sender: bytes32 (32 bytes) - message sender address
• recipient: bytes32 (32 bytes) - message recipient address
• destinationCaller: bytes32 (32 bytes) - authorized caller on destination
• minFinalityThreshold: uint32 (4 bytes) - minimum required finality
• finalityThresholdExecuted: uint32 (4 bytes) - actual finality level

Total fixed size: 4 + 4 + 4 + 32 + 32 + 32 + 32 + 4 + 4 = 148 bytes

Fields

version: u32

Message format version

source_domain: DomainId

Source blockchain domain ID

destination_domain: DomainId

Destination blockchain domain ID

nonce: FixedBytes<32>

Unique message nonce assigned by Circle

sender: FixedBytes<32>

Address that sent the message (padded to 32 bytes)

recipient: FixedBytes<32>

Address that will receive the message (padded to 32 bytes)

destination_caller: FixedBytes<32>

Address authorized to call receiveMessage on destination (0 = anyone)

min_finality_threshold: u32

Minimum finality threshold required (1000 = Fast, 2000 = Standard)

finality_threshold_executed: u32

Actual finality threshold when message was attested

Implementations

impl MessageHeader

pub const SIZE: usize = 148

Size of the message header in bytes

pub fn new( version: u32, source_domain: DomainId, destination_domain: DomainId, nonce: FixedBytes<32>, sender: FixedBytes<32>, recipient: FixedBytes<32>, destination_caller: FixedBytes<32>, min_finality_threshold: u32, finality_threshold_executed: u32, ) -> Self

Creates a new message header

pub fn encode(&self) -> Bytes

Encodes the message header to bytes

The encoding follows Circle’s v2 message format specification.

pub fn decode(bytes: &[u8]) -> Option<Self>

Decodes a message header from bytes

Returns None if the bytes are not at least MessageHeader::SIZE bytes long or if domain IDs are invalid.

pub fn parse(bytes: &[u8]) -> Result<Self, ParseMessageError>

Parses a message header and returns a descriptive error on failure.

pub fn has_placeholder_nonce(&self) -> bool

Returns true when the nonce is still the placeholder zero value from the on-chain event.

pub fn sender_address(&self) -> Address

Returns the EVM sender address encoded in the 32-byte sender field.

This helper assumes the source domain uses the EVM trailing-20-byte convention for bytes32 addresses. For non-EVM domains, the raw Self::sender field is authoritative.

pub fn recipient_address(&self) -> Address

Returns the EVM recipient address encoded in the 32-byte recipient field.

This helper assumes the destination domain uses the EVM trailing-20-byte convention for bytes32 addresses. For non-EVM domains, the raw Self::recipient field is authoritative.

pub fn destination_caller_address(&self) -> Option<Address>

Returns the destination caller as an EVM address if the message is not permissionless.

This helper assumes the destination domain uses the EVM trailing-20-byte convention for bytes32 addresses. For non-EVM domains, the raw Self::destination_caller field is authoritative.

pub fn is_permissionless(&self) -> bool

Returns true when the message can be relayed by anyone.

pub fn requested_finality(&self) -> Option<FinalityThreshold>

Returns the requested finality threshold when it matches a known CCTP mode.

pub fn attested_finality(&self) -> Option<FinalityThreshold>

Returns the finality threshold that Circle actually used for the attestation.

Trait Implementations

impl Clone for MessageHeader

fn clone(&self) -> MessageHeader

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MessageHeader

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for MessageHeader

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for MessageHeader

fn eq(&self, other: &MessageHeader) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for MessageHeader

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for MessageHeader

impl StructuralPartialEq for MessageHeader