Starknet

Execute deposit transactions on Starknet using the multicall format from call_data.

Overview

Starknet deposits are simple to execute because the Layerswap API returns a pre-built array of Starknet calls in call_data. You parse the JSON and pass it directly to the account’s execute method, which handles multicall execution natively.

Prerequisites:

• starknet.js for account interaction and transaction execution

Supported networks: Starknet Mainnet, Starknet Sepolia

call_data Format

For Starknet, call_data is a JSON-encoded array of call objects. Layerswap always returns two calls:

1. A transfer call on the token contract (ETH on Starknet is also an ERC-20).
2. A watch call on the Layerswap Watchdog contract, which the backend uses to match the deposit.

[
  {
    "contractAddress": "0x049d36570d4e46f48e99674bd3fcc84644ddd6b96f7c741b1562b82f9e004dc7",
    "entrypoint": "transfer",
    "calldata": ["0xRecipient", "0xAmountLow", "0xAmountHigh"]
  },
  {
    "contractAddress": "0xWatchdogContract...",
    "entrypoint": "watch",
    "calldata": ["0xSequenceNumber"]
  }
]

Both calls must execute atomically — pass the whole array to account.execute() as shown below; Starknet handles them as a single multicall transaction.

Transaction Construction

1. Parse call_data

   Deserialize the JSON string into an array of Starknet call objects.

2. Execute via Account

   Pass the calls array to account.execute(). Starknet natively supports multicall, so all calls in the array are executed atomically in a single transaction.

3. Return the transaction hash

   The execute method returns an object with transaction_hash.

Full Example

Pick the flavor that matches your setup. The Server-side tab signs with a raw private key via starknet.js. The Browser tab connects to an injected wallet like ArgentX or Braavos via get-starknet. The starknet-react tab wraps it as a hook for React apps.

Server-side

import { Account, RpcProvider, Call } from "starknet";

async function executeStarknetDeposit(
  depositAction: any,
  senderAddress: string,
  privateKey: string
) {
  const { call_data, network } = depositAction;

  const provider = new RpcProvider({ nodeUrl: network.node_url });
  const account = new Account(provider, senderAddress, privateKey);

  // Parse the call_data JSON into Starknet calls
  const calls: Call[] = JSON.parse(call_data);

  // Execute the multicall transaction
  const { transaction_hash } = await account.execute(calls);

  if (!transaction_hash) {
    throw new Error("No transaction hash returned");
  }

  // Optionally wait for confirmation
  await provider.waitForTransaction(transaction_hash);

  return transaction_hash;
}

import { connect } from "get-starknet";
import { Call } from "starknet";

async function executeStarknetDeposit(depositAction: any) {
  const { call_data } = depositAction;

  // Connect to wallet
  const starknet = await connect();
  if (!starknet?.isConnected || !starknet.account) {
    throw new Error("Starknet wallet not connected");
  }

  // Parse the call_data JSON
  const calls: Call[] = JSON.parse(call_data);

  // Execute through the connected wallet
  const { transaction_hash } = await starknet.account.execute(calls);

  if (!transaction_hash) {
    throw new Error("No transaction hash returned");
  }

  return transaction_hash;
}

import { useAccount } from "@starknet-react/core";
import { Call } from "starknet";

function useStarknetDeposit() {
  const { account } = useAccount();

  async function executeDeposit(depositAction: any): Promise<string> {
    if (!account) {
      throw new Error("Starknet account not connected");
    }

    const calls: Call[] = JSON.parse(depositAction.call_data);
    const { transaction_hash } = await account.execute(calls);

    if (!transaction_hash) {
      throw new Error("No transaction hash returned");
    }

    return transaction_hash;
  }

  return { executeDeposit };
}

Next Step

After the transaction is submitted, notify Layerswap so it can match your deposit faster:

curl -X POST https://api.layerswap.io/api/v2/swaps/{swap_id}/deposit_speedup \
  -H "X-LS-APIKEY: your_api_key" \
  -H "Content-Type: application/json" \
  -d '{ "transaction_id": "YOUR_TX_HASH" }'

See the full deposit flow for details.