Chain Abstraction

💡 Chain Abstraction is in early access.

Chain Abstraction in WalletKit enables users with stablecoins on any network to spend them on-the-fly on a different network. Our Chain Abstraction solution provides a toolkit for wallet developers to integrate this complex functionality using WalletKit.

For example, when an app requests a 100 USDC payment on Base network but the user only has USDC on Arbitrum, WalletKit offers methods to detect this mismatch, generate necessary transactions, track the cross-chain transfer, and complete the original transaction after bridging finishes.

How It Works

Apps need to pass gas as null, while sending a transaction to allow proper gas estimation by the wallet. Refer to this guide for more details.

When sending a transaction, you need to:

1. Check if the required chain has enough funds to complete the transaction
2. If not, use the prepare method to generate necessary bridging transactions
3. Sign routing and initial transaction hashes, prepared by the prepare method
4. Use execute method to broadcast routing and initial transactions and wait for it to be completed

The following sequence diagram illustrates the complete flow of a chain abstraction operation, from the initial dapp request to the final transaction confirmation

Chain Abstraction Flow

Methods

The following methods from WalletKit are used in implementing chain abstraction.

💡 Chain abstraction is currently in the early access phase, use with careful

Prepare

This method is used to check if chain abstraction is needed. If it is, it will return a response with the necessary transactions. If it is not, it will return a response with the original transaction.

@available(*, message: "This method is experimental. Use with caution.")
public func prepare(chainId: String, from: FfiAddress, call: Call, accounts: [String], localCurrency: Currency) async throws -> PrepareDetailedResponse 
}

Execute

This method is used to execute the chain abstraction operation. The method will handle broadcasting all transactions in the correct order and monitor the cross-chain transfer process. It returns an ExecuteDetails object with the transaction status and results.

@available(*, message: "This method is experimental. Use with caution.")
public func execute(uiFields: UiFields, routeTxnSigs: [FfiPrimitiveSignature], initialTxnSig: FfiPrimitiveSignature) async throws -> ExecuteDetails {
}

Usage

When sending a transaction, first check if chain abstraction is needed using the prepare method. Call the execute method to broadcast the routing and initial transactions and wait for it to be completed.

If the operation is successful, you need to broadcast the initial transaction and await the transaction hash and receipt. If the operation is not successful, send a JsonRpcError to the dapp and display the error to the user.

let routeResponseSuccess = try await WalletKit.instance.ChainAbstraction.prepare(
    chainId: selectedNetwork.chainId.absoluteString,
    from: myAccount.address,
    call: call,
    accounts: caip10Accounts,
    localCurrency: .usd
)

switch routeResponseSuccess {
case .success(let routeResponse):
    switch routeResponse {
    case .available(let UiFileds):
        // If the route is available, present a CA transaction flow
        for txnDetails in uiFields.route {
            let hash = txnDetails.transactionHashToSign
            let sig = try! signer.signHash(hash)
            routeTxnSigs.append(sig)
        }
        
        // sign initial transaction hash
        let initialTxHash = uiFields.initial.transactionHashToSign
        let initialTxnSig = try! signer.signHash(initialTxHash)      
        
        let executeDetails = try await WalletKit.instance.ChainAbstraction.execute(uiFields: uiFields, routeTxnSigs: routeTxnSigs, initialTxnSig: initialTxnSig)
        
    case .notRequired:
        // user does not need to move funds from other chains, sign and broadcast original transaction
        
    }
case .error(let routeResponseError):
    // Show an error
}

For example, check out implementation of chain abstraction in sample wallet with Swift.

Error Handling

When implementing Chain Abstraction, you may encounter different types of errors. Here’s how to handle them effectively:

Application-Level Errors

These errors (PrepareError) indicate specific issues that need to be addressed and typically require user action:

• Insufficient Gas Fees: User needs to add more gas tokens to their wallet
• Malformed Transaction Requests: Transaction parameters are invalid or incomplete
• Minimum Bridging Amount Not Met: Currently set at $0.60
• Invalid Token or Network Selection: Selected token or network is not supported

When handling these errors, you should display clear, user-friendly error messages that provide specific guidance on how to resolve the issue. Allow users to modify their transaction parameters and consider implementing validation checks before initiating transactions.

Retryable Errors

These errors (Result::Err) indicate temporary issues that may be resolved by retrying the operation. Examples of these types of issues include network connection timeouts, TLS negotiation issues, service outages, or other transient errors.

For retryable errors, show a generic “oops” message to users and provide a retry button. Log detailed error information to your error tracking service, but avoid displaying technical details to end users.

For errors in the execute() method, a retry may not resolve the issue. In such cases, allow users to cancel the transaction, return them to the application, and let the application initiate a new transaction.

Critical Errors

Critical errors indicate bugs or implementation issues that should be treated as high-priority incidents: incorrect usage of WalletKit API, wrong data encoding or wrong fields passed to WalletKit, or WalletKit internal bugs.

Testing

Best way to test Chain Abstraction is to use sample wallet. You can also use the AppKit laboratory and try sending any supported tokens with any chain abstraction-supported wallet.