Bridge with a Gasless Account

This guide covers prerequisites, how to create a gasless account, read the fees, bridge with paymaster options, and what the Kora node must allow.

Prerequisites

• A Kora-compatible paymaster endpoint and fee payer address. See the gasless wallet configuration.
• A node configured for this bridge, as described in Kora node requirements. A paymaster that only sponsors ordinary transfers rejects it.

npm install @tetherto/wdk-protocol-bridge-usdt0-solana @tetherto/wdk-wallet-solana-gasless

Create a gasless account

Create a WalletAccountSolanaGasless and wrap it with the same bridge class. The bridge recognizes the gasless flow from the account's paymasterAddress:

import { WalletAccountSolanaGasless } from '@tetherto/wdk-wallet-solana-gasless'
import Usdt0ProtocolSolana from '@tetherto/wdk-protocol-bridge-usdt0-solana'

const account = new WalletAccountSolanaGasless(process.env.SEED_PHRASE, "0'/0'", {
  provider: 'https://api.mainnet-beta.solana.com',
  paymasterUrl: 'https://your-kora-paymaster.example',
  paymasterAddress: process.env.PAYMASTER_ADDRESS,
  paymasterToken: { address: 'Es9vMFrzaCERmJfrF4H2FYD4KCoNkY11McCe8BenwNYB' }
})

const bridgeProtocol = new Usdt0ProtocolSolana(account)

The account needs USD₮ for the amount and paymaster tokens for the fee. It does not need SOL. For quotes without signing, use WalletAccountReadOnlySolanaGasless with the same configuration. The paymaster is the simulated fee payer, so the source address does not have to hold SOL.

Read the fees

The paymaster pays the Solana transaction, fronts the LayerZero fee, and charges both back in the paymaster token through the wallet's payment instruction. The two fields returned by quoteBridge() and bridge() therefore use different units:

Bridge with paymaster options

You can pass overrides as the second argument of bridge():

const options = {
  targetChain: 'arbitrum',
  recipient: process.env.ARBITRUM_RECIPIENT,
  token: 'Es9vMFrzaCERmJfrF4H2FYD4KCoNkY11McCe8BenwNYB',
  amount: 1000000n
}

const quote = await bridgeProtocol.quoteBridge(options)

const result = await bridgeProtocol.bridge(options, {
  bridgeMaxFee: 2_000_000n, // Lamports, checked before contacting the paymaster
  transactionMaxFee: 1_000_000n, // Paymaster token base units
  paymasterToken: { address: 'Es9vMFrzaCERmJfrF4H2FYD4KCoNkY11McCe8BenwNYB' }
})

console.log('Solana transaction hash:', result.hash)
console.log('Paid to the paymaster:', result.fee)
console.log('LayerZero fee fronted:', result.bridgeFee, 'lamports')

quoteBridge() accepts only the paymasterToken override.

Kora node requirements

The bridge needs more from the node than an ordinary sponsored transfer. Your Kora node must have:

• Margin pricing, so the LayerZero fee it pays is charged back.
• fee_payer_policy.system.allow_transfer = true, because the LayerZero message library pays its workers from the fee payer.
• max_allowed_lamports above the LayerZero fee, which follows destination gas prices. See the sampled fees. TRON was above 0.1 SOL when sampled.
• The programs below on its allowlist.

Next Steps

Harden integrations with Handle errors, or review the gasless wallet module.

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