How to: Add Arc to Your Bridge Protocol

import { defineChain } from "viem";

export const arcTestnet = defineChain({
  id: 5042002,
  name: "Arc Testnet",
  nativeCurrency: {
    name: "USDC",
    symbol: "USDC",
    decimals: 18,
  },
  rpcUrls: {
    default: {
      http: ["https://rpc.testnet.arc.network"],
      webSocket: ["wss://rpc.testnet.arc.network"],
    },
  },
  blockExplorers: {
    default: {
      name: "Arcscan",
      url: "https://testnet.arcscan.app",
    },
  },
});

// Bridge confirmation config
const arcBridgeConfig = {
  chainId: 5042002,
  requiredConfirmations: 1, // Deterministic finality—1 is sufficient
  finalityType: "deterministic" as const,
  avgBlockTimeMs: 500,
};

import { createWalletClient, http } from "viem";
import { privateKeyToAccount } from "viem/accounts";

// Deploy using standard viem workflow
const account = privateKeyToAccount(
  process.env.DEPLOYER_PRIVATE_KEY as `0x${string}`,
);

const walletClient = createWalletClient({
  account,
  chain: arcTestnet,
  transport: http("https://rpc.testnet.arc.network"),
});

// CREATE2 deterministic deployment works as expected
// Permit2 is available at the canonical address
const PERMIT2_ADDRESS = "0x000000000022D473030F116dDEE9F6B43aC78BA3";
const MULTICALL3_ADDRESS = "0xcA11bde05977b3631167028862bE2a173976CA11";

import { parseUnits, formatUnits } from "viem";

// Check relayer gas balance (USDC with 18 decimals at native level)
const balance = await publicClient.getBalance({
  address: relayerAddress,
});

console.log(`Relayer balance: ${formatUnits(balance, 18)} USDC`);

// Fund relayer via ERC-20 transfer (6 decimals)
const USDC_ADDRESS = "0x3600000000000000000000000000000000000000";

const fundTx = await walletClient.writeContract({
  address: USDC_ADDRESS,
  abi: [
    {
      name: "transfer",
      type: "function",
      inputs: [
        { name: "to", type: "address" },
        { name: "amount", type: "uint256" },
      ],
      outputs: [{ type: "bool" }],
      stateMutability: "nonpayable",
    },
  ],
  functionName: "transfer",
  args: [relayerAddress, parseUnits("1000", 6)], // 1,000 USDC
});

import { createPublicClient, webSocket, http } from "viem";

// WebSocket for real-time event monitoring (relay watchers)
const wsClient = createPublicClient({
  chain: arcTestnet,
  transport: webSocket("wss://rpc.testnet.arc.network"),
});

// HTTP for transaction submission (relay executors)
const httpClient = createPublicClient({
  chain: arcTestnet,
  transport: http("https://rpc.testnet.arc.network"),
});

// Watch for bridge events with immediate finality
const unwatch = wsClient.watchContractEvent({
  address: YOUR_BRIDGE_CONTRACT,
  abi: bridgeAbi,
  eventName: "MessageSent",
  onLogs: (logs) => {
    // Each log is final on receipt—no need to wait for confirmations
    for (const log of logs) {
      processRelayMessage(log);
    }
  },
});