Bundler API - Using SDK

The v5 stack uses viem's createBundlerClient for direct interaction with Alchemy's ERC-4337 bundler. @alchemy/aa-infra's estimateFeesPerGas helper wraps rundler_getUserOperationGasPrice so the bundler picks user-op-aware fees. Below: estimate-and-send a UserOperation, and retrieve a UserOperation by hash.

config.ts

import { sepolia } from "viem/chains";
 
export const chain = sepolia;
export const ALCHEMY_API_KEY = "<YOUR_API_KEY>";
export const PRIVATE_KEY = "<YOUR_PRIVATE_KEY>";

estimateAndSendUserOperation.ts

import { createBundlerClient } from "viem/account-abstraction";
import { createClient, type Hex } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { alchemyTransport } from "@alchemy/common";
import { toModularAccountV2 } from "@alchemy/smart-accounts";
import { estimateFeesPerGas } from "@alchemy/aa-infra";
import { chain, ALCHEMY_API_KEY, PRIVATE_KEY } from "./config";
 
const transport = alchemyTransport({ apiKey: ALCHEMY_API_KEY });
 
export async function estimateAndSendUserOperation() {
  const rpcClient = createClient({ chain, transport });
 
  const account = await toModularAccountV2({
    client: rpcClient,
    owner: privateKeyToAccount(PRIVATE_KEY as Hex),
  });
 
  const bundlerClient = createBundlerClient({
    account,
    client: rpcClient,
    chain,
    transport,
    userOperation: { estimateFeesPerGas },
  });
 
  try {
    const hash = await bundlerClient.sendUserOperation({
      calls: [
        { to: "0x0000000000000000000000000000000000000000", value: 0n, data: "0x" },
      ],
    });
 
    const receipt = await bundlerClient.waitForUserOperationReceipt({ hash });
    console.log("UserOperation receipt:", receipt);
  } catch (error) {
    console.error("Error processing UserOperation:", error);
  }
}

getUserOperationByHash.ts

import { createBundlerClient } from "viem/account-abstraction";
import { createClient, type Hash } from "viem";
import { alchemyTransport } from "@alchemy/common";
import { chain, ALCHEMY_API_KEY } from "./config";
 
const transport = alchemyTransport({ apiKey: ALCHEMY_API_KEY });
 
export async function getUserOperationByHash(uoHash: Hash) {
  const rpcClient = createClient({ chain, transport });
  const bundlerClient = createBundlerClient({
    client: rpcClient,
    chain,
    transport,
  });
 
  try {
    const userOp = await bundlerClient.getUserOperation({ hash: uoHash });
    console.log("User Operation:", userOp);
  } catch (error) {
    console.error("Error retrieving UserOperation:", error);
  }
}

Make sure your environment has the correct ALCHEMY_API_KEY and PRIVATE_KEY. These examples target EntryPoint v0.7 by default via Modular Account V2.

Bundler API - Using SDK

Manage UserOperations with viem + @alchemy/aa-infra