Solidity API

IRelayBridge

Interface for the RelayBridge contract Defines the bridge function for cross-chain asset transfers

bridge

function bridge(uint256 amount, address recipient, address poolAsset, uint256 poolGas, bytes extraData) external payable returns (uint256 nonce)

Bridges an asset (ERC20 token or native currency) from the origin chain to a pool chain

Parameters

Name	Type	Description
amount	uint256	Amount of asset units to bridge (ERC20 tokens or native currency)
recipient	address	Address on the pool chain to receive the bridged asset
poolAsset	address	Address of the asset on the pool chain to bridge to
poolGas	uint256	Gas limit for the pool chain transaction
extraData	bytes	Extra data passed to the bridge proxy

Return Values

Name	Type	Description
nonce	uint256	Unique identifier for this bridge transaction

RelayBridge

RelayBridge contract enabling cross-chain bridging via Hyperlane Bridges assets from an origin chain to a configured pool chain

BridgeTransaction

Internal struct capturing parameters for a bridge transaction

struct BridgeTransaction {
  uint256 amount;
  address recipient;
  address poolAsset;
  uint256 poolGas;
  bytes extraData;
  uint256 nonce;
  bytes txParams;
  uint32 poolChainId;
  bytes32 poolId;
}

BridgingFailed

error BridgingFailed(uint256 nonce)

Error for failed bridging operations

Parameters

Name	Type	Description
nonce	uint256	The nonce of the failed transaction

InsufficientValue

error InsufficientValue(uint256 received, uint256 expected)

Error for insufficient native value sent to cover fees or asset

Parameters

Name	Type	Description
received	uint256	The amount of native currency received
expected	uint256	The amount of native currency expected

FailedFeeRefund

error FailedFeeRefund(uint256 value)

Error when refunding leftover native value fails

Parameters

Name	Type	Description
value	uint256	The amount of native currency that failed to refund

transferNonce

uint256 transferNonce

Counter for assigning unique nonces to bridge transactions Incremented with each bridge transaction to ensure uniqueness

ASSET

address ASSET

Asset address on the origin chain being bridged (address(0) for native currency) Immutable to ensure the bridge always handles the same asset

BRIDGE_PROXY

contract BridgeProxy BRIDGE_PROXY

BridgeProxy contract handling origin-chain transfer logic Uses delegatecall to execute custom bridge logic

HYPERLANE_MAILBOX

address HYPERLANE_MAILBOX

Hyperlane Mailbox contract for cross-chain messaging Used to dispatch messages to the pool chain

BridgeInitiated

event BridgeInitiated(uint256 nonce, address sender, address recipient, address ASSET, address poolAsset, uint256 amount, contract BridgeProxy BRIDGE_PROXY)

Emitted when a bridge transaction is initiated on the origin chain

Parameters

Name	Type	Description
nonce	uint256	Nonce of the transaction
sender	address	Address on the origin chain that initiated the bridge
recipient	address	Address on the pool chain to receive assets
ASSET	address	Asset address on the origin chain (address(0) for native currency)
poolAsset	address	Asset address on the pool chain (address(0) for native currency)
amount	uint256	Amount of asset units bridged
BRIDGE_PROXY	contract BridgeProxy	BridgeProxy used

BridgeExecuted

event BridgeExecuted(uint256 nonce)

Emitted after a bridge transaction is executed on the pool chain This event would be emitted by the pool chain contract

Parameters

Name	Type	Description
nonce	uint256	Nonce of the executed transaction

BridgeCancelled

event BridgeCancelled(uint256 nonce)

Emitted if a bridge transaction is cancelled prior to execution This event would be emitted if a bridge is cancelled

Parameters

Name	Type	Description
nonce	uint256	Nonce of the cancelled transaction

constructor

constructor(address asset, contract BridgeProxy bridgeProxy, address hyperlaneMailbox) public

Initializes the RelayBridge with asset and infrastructure contracts All parameters are immutable after deployment

Parameters

Name	Type	Description
asset	address	Asset address on the origin chain to bridge (0 for native currency)
bridgeProxy	contract BridgeProxy	BridgeProxy contract for origin-chain transfers
hyperlaneMailbox	address	Hyperlane Mailbox address for messaging

getFee

function getFee(uint256 amount, address recipient, uint256 poolGas) external view returns (uint256 fee)

Calculates the fee required in native currency to dispatch a cross-chain message Uses Hyperlane’s quoteDispatch to estimate the cross-chain messaging fee

Parameters

Name	Type	Description
amount	uint256	Amount of asset units to bridge
recipient	address	Address on the pool chain that will receive the bridged asset
poolGas	uint256	Gas limit for the pool chain transaction

Return Values

Name	Type	Description
fee	uint256	Required fee in native currency for dispatch

bridge

function bridge(uint256 amount, address recipient, address poolAsset, uint256 poolGas, bytes extraData) external payable returns (uint256 nonce)

Bridges an asset (ERC20 token or native currency) from the origin chain to a pool chain _Executes a cross-chain bridge transaction with the following steps:

Validates sufficient payment for fees (and asset amount if native)
Transfers the asset from sender to this contract (if ERC20)
Executes bridge logic via delegatecall to BRIDGE_PROXY
Dispatches cross-chain message via Hyperlane
Refunds any excess native currency to sender_

Parameters

Name	Type	Description
amount	uint256	Amount of asset units to bridge (ERC20 tokens or native currency)
recipient	address	Address on the pool chain to receive the bridged asset
poolAsset	address	Address of the asset on the pool chain to bridge to
poolGas	uint256	Gas limit for the pool chain transaction
extraData	bytes	Extra data passed to the bridge proxy

Return Values

Name	Type	Description
nonce	uint256	Unique identifier for this bridge transaction

Relay Protocol

​Solidity API

​IRelayBridge

​bridge

​Parameters

​Return Values

​RelayBridge

​BridgeTransaction

​BridgingFailed

​Parameters

​InsufficientValue

​Parameters

​FailedFeeRefund

​Parameters

​transferNonce

​ASSET

​BRIDGE_PROXY

​HYPERLANE_MAILBOX

​BridgeInitiated

​Parameters

​BridgeExecuted

​Parameters

​BridgeCancelled

​Parameters

​constructor

​Parameters

​getFee

​Parameters

​Return Values

​bridge

​Parameters

​Return Values

Solidity API

IRelayBridge

bridge

Parameters

Return Values

RelayBridge

BridgeTransaction

BridgingFailed

Parameters

InsufficientValue

Parameters

FailedFeeRefund

Parameters

transferNonce

ASSET

BRIDGE_PROXY

HYPERLANE_MAILBOX

BridgeInitiated

Parameters

BridgeExecuted

Parameters

BridgeCancelled

Parameters

constructor

Parameters

getFee

Parameters

Return Values

bridge

Parameters

Return Values