Adapters

Overview

Adapters are smart contracts that integrate with specific bridges and are used by other contracts—such as Message Controllers, Asset Controllers, and others—that need to communicate across chains. Lucid develops and deploys these adapter contracts across all chains supported by both Lucid and the corresponding bridge.

Adapter contracts are permissionless, meaning anyone can call them to relay a message to a supported chain, as long as an adapter contract exists for that target chain.

Functionality

An adapter's primary role is to relay and receive messages to and from the bridge. These messages are typically sent by a contract on the same chain, such as a Message Controller.

The adapter:

• Repackages the message to include the original msg.sender (typically the Message Controller) and the destination address (usually the Message Controller on the destination chain)

• Does not inspect or modify the message content; it supports arbitrary bytes[] data

• Uses the bridge to relay the message to the corresponding adapter on the destination chain

On the destination chain, the adapter:

• Unpacks the message to recover the original msg.sender from the source chain and the intended destination address

• Forwards the original message to the destination contract

Fees

The system charges a protocol fee for relaying messages between chains. This fee is calculated as a percentage of the value being sent (i.e., the bridge fee).

By default, the protocol fee is set to 30% for all bridge adapters.

Interfaces

Public Functions

Each adapter implements the following public functions:

relayMessage

function relayMessage( uint256 destChainId, address destination, bytes memory options, bytes calldata message ) external payable returns (bytes32)

Sends a message to the Bridge, paying any fees to the bridge and deducting the protocol fee. Any excess fees are returned to the refundAddress.

Input Params:

Type	Name	Description
uint256	destChainId	The destination chain ID.
address	destination	The destination address.
bytes	options	Additional params to be used by each adapter. Usually the refund address and the gas limit.
bytes	message	The message to be relayed.

The function returns a bytes32 transferId for the bridges that support it.

---

View Functions

Each adapter implements the following view functions:

isChainSupported

function isChainIdSupported(uint256 chainId) public view returns (bool);

Checks if a given chain ID is supported by the adapter.

---

trustedAdapters()

function trustedAdapters(uint256 chainId) external view returns (address);

Returns the contract address of the Adapter for a given chain id. Will return address(0) if an adapter doesn't exist on that chain.

---

isTrustedAdapter()

function isTrustedAdapter(uint256 chainId, address adapter) external view returns (bool);

Returns true if the given adapter is a trusted adapter for the specified chain ID