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Solana Migration Guide

Across is expanding support to Solana, enabling seamless USDC bridging between Ethereum Mainnet, other supported chains and Solana.

The migration is scheduled to go live soon. All integrators and relayers are encouraged to complete the necessary updates before the migration happens to prevent disruptions.

Introduction

The changes detailed in this guide aim to support Developers, Integrators, and Relayers in order to advance their current codebases and implement the suggested changes to support bridging USDC to-and-from Solana. Here is a quick overview:

  • Developers and Integrators: We will highlight the changes and additions you can make to your current integrations.

  • Relayers and Indexers: We will be highlighting changes to events worth listen to and details on handling Solana address format.

Supporting Solana is a major milestone in our roadmap. With this, we’re ensuring all Across integrations can seamlessly add Solana to their product suites.

Summary of Product Changes

SpokePool contract deployed on Solana supports USDC bridging between Ethereum Mainnet, all supported L2s, and Solana. Integrators must use the new Deposit() function in order to use the Solana routes. You can learn more about the contract here.

DepositV3 is not being deprecated and can continue to be used for all EVM routes.

We urge integrators to reach out to us in case they want to use the multicall handler contract on Solana. We are still building a seamless experience here and are eager to assist.

Across Protocol will use 34268394551451 as the chain ID for Solana.

For Indexers

When working with the deposit/status endpoint, there are important parameter changes to note:

  1. The parameter depositTxHash will still work for EVM chains but is deprecated and will be removed soon.

  2. A new parameter depositTxnId is being introduced that works universally for both EVM and Solana transactions:

    1. For EVM: This will be the transaction hash

    2. For Solana: This will be the transaction signature

Transaction status tracking

The status values returned by the deposit/status API remain unchanged:

  • pending

  • filled

  • expired

  • requestSlowFill

  • refunded

However, be aware that Solana transactions use signatures rather than transaction hashes for identification. All other fields in the API response body will remain the same.

For Developers and Integrators

For Solana routes, check out this utility script demonstrating how to call deposit()with the integratorID for seamless transaction execution.

Building and Executing Transactions

We do not support Solana devnet or testnet at the moment. We urge developers and integrators to test their Solana integration using the Solana mainnet with small amount of tokens. We will let you know as soon as we are live and you can begin testing.

Solana is not currently supported in the Across App-SDK. We’re actively working on expanding support and improving the developer experience for Solana. Stay tuned — we’ll share updates as soon as it becomes available.

If you need any help adding the integratorID, please reach out to us here.

For Relayers

Relayers supporting Solana will need:

  1. A valid Solana address to perform fill operations.

  2. The following package dependencies:

    1. @across-protocol/sdk

    2. @across-protocol/contracts

    3. @solana/kit (previously @solana/web3.js@^2.0.0)

While each relayer can decide how to manage their Solana addresses, the recommended approach is deriving the Solana address from the same private key used for EVM operations. This approach minimizes the need to store additional secrets.

When filling to or from Solana, relayers must always specify a valid address on the chain where they request repayment. Failing to do so may result in loss of funds.

Fill Mechanism Changes

For relayers, the most significant update for relayers is the transition from fillV3Relay to fillRelay for handling crosschain transactions:

  1. For deposits from Solana to EVM chains:

    1. Relayers monitor for deposit events on Solana

    2. Use fillRelay to complete the fill transaction on the EVM destination. You can learn more about it here.

  2. For deposits from EVM chains to Solana:

    1. Monitor for deposit events on EVM chains

    2. Use Solana-specific fill functions to complete the transaction

We use emit_cpi!() method in Anchor to emit events through a Cross Program Invocation (CPI) by including the event data in the instruction data. Here, you need to fetch all transactions involving the SVM Spokepool program and inspect the internal event data. Please checkout the helper in the SDK to implement this.

Technical Reference

Deposit Function

The deposit function is used when users want to transfer funds from Solana to an EVM chain:

// This function is called when a user wants to bridge from Solana to another chain
function deposit(
    Pubkey depositor,           // The depositor address in Pubkey format
    Pubkey recipient,           // The recipient address on the destination chain
    Pubkey input_token,          // Token being deposited (on Solana)
    Pubkey output_token,         // Token to receive on destination chain
    u64 input_amount,         // Amount of input token being deposited
    u64 output_amount,        // Amount of output token to receive
    u64 destination_chain_id,  // Destination chain ID
    Pubkey exclusive_relayer,    // Address of exclusive relayer (use Pubkey::default() if none)
    u32 quote_timestamp,       // Timestamp when quote was generated
    u32 fill_deadline,         // Deadline after which deposit can't be filled
    u32 exclusivity_parameter,  // Deadline for exclusive relayer's priority
    Vec<u8> calldata message       // Additional message data
) external payable;

FillRelay Function

Relayers use this function to complete crosschain transactions:

/// This function is called when a relayer wants to fill a crosschain bridge request by sending
/// the specified output tokens to the recipient on the destination chain.
function fillRelay(
    [u8; 32] relay_hash,             // Hash uniquely identifying the deposit to be filled. Computed as hash of relay_data & destination_chain_id.
    V3RelayData relay_data,         // Struct containing all deposit data (matches parameters from FundsDeposited event).
    Pubkey depositor,              // The account credited with the deposit on the origin chain.
    Pubkey recipient,              // The recipient account receiving the funds on this chain.
    Pubkey input_token,            // Token used for deposit on the origin chain.
    Pubkey output_token,           // Token to be received by the recipient on the destination chain.
    u64 input_amount,           // Amount deposited by the user on the origin chain.
    u64 output_amount,          // Amount sent to the recipient on the destination chain.
    u64 origin_chain_id,        // Origin chain identifier.
    Pubkey exclusive_relayer,      // The exclusive relayer allowed to fill the deposit before the exclusivity deadline.
    u32 fill_deadline,           // Deadline after which deposit cannot be filled.
    u32 exclusivity_deadline,    // Deadline for exclusive relayer to maintain priority.
    bytes calldata message,         // Message to be passed.
    u64 repayment_chain_id,     // Chain where the relayer expects repayment after the challenge period.
    Pubkey repayment_address       // Address where relayer wants to receive refund on the repayment chain.
) external;

Support

Want to learn more or need personalized help? Check out developer support and reach out to us!

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