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 const SUPPORTED_VERSION: u32 = CCTP_V2_MESSAGE_VERSION

The only CCTP v2 message header version this parser understands.

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) -> Option<Address>

Returns the sender as an EVM Address when the source domain is EVM.

Returns None for non-EVM domains such as DomainId::Solana or DomainId::StarknetTestnet, whose bytes32 sender words do not use the EVM trailing-20-byte convention. For those domains, the raw Self::sender field is the canonical source of truth.

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

Returns the recipient as an EVM Address when the destination domain is EVM.

Returns None for non-EVM destination domains. For those, the raw Self::recipient field is the canonical source of truth.

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

Returns the destination caller as an EVM Address when one is set and the destination domain is EVM.

Returns None when the message is permissionless or the destination domain is non-EVM. The raw Self::destination_caller field is authoritative in the non-EVM case.

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 Eq for MessageHeader

impl PartialEq for MessageHeader

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

Equality operator ==.

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

Inequality operator !=.

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 StructuralPartialEq for MessageHeader