Ethereum has come a long way from its inception, and one of the most talked-about advancements in recent years is Account Abstraction (AA)<\/strong>.<\/p>\n But what does AA<\/strong> actually do? How do Bundlers<\/strong> and Paymasters<\/strong> work? And most importantly, why does this change how transactions work?<\/p>\n In this post, we\u2019ll break it all down with a real implementation<\/strong>: a minimal Bundler built using Biconomy\u2019s AA infrastructure<\/strong>.<\/p>\n Ethereum started with Externally Owned Accounts (EOAs)<\/strong>\u200a\u2014\u200awallets controlled by a private\u00a0key.<\/p>\n But EOAs have some major limitations<\/strong>:<\/p>\n \u274c Lose your key? Say goodbye to your\u00a0funds.<\/p>\n \u274c You always need ETH<\/strong> to pay for\u00a0gas.<\/p>\n \u274c No custom transaction rules, just simple to, value, and data\u00a0fields.<\/p>\n Account Abstraction (AA) fixes<\/strong> these problems by allowing users to use smart contract wallets<\/strong> instead of\u00a0EOAs.<\/p>\n Instead of EOAs, AA introduces smart contract wallets<\/strong>, which\u00a0can:<\/p>\n \u2705 Allow multi-signatures.<\/p>\n \u2705 Let you pay gas in any token<\/strong> (or have someone else pay it for\u00a0you).<\/p>\n \u2705 Enable social recovery<\/strong> and custom authentication logic.<\/p>\n But to make this work, we need a new way<\/strong> to send transactions, and that\u2019s where Bundlers<\/strong> and Paymasters<\/strong> come\u00a0in.<\/p>\n A normal Ethereum transaction<\/strong> goes directly to the mempool, waiting to be picked up by miners or validators.<\/p>\n With AA<\/strong>, the flow is different:<\/p>\n The user creates a UserOperation<\/strong>.Sends it to a Bundler<\/strong>, NOT the\u00a0mempool.The Bundler validates<\/strong> and submits it to the\u00a0network.<\/p>\n But what exactly does a Bundler<\/strong>\u00a0do?<\/p>\n A Bundler<\/strong> is like a miner, but specifically for AA transactions<\/strong>.<\/p>\n It does the following:<\/p>\n Accepts UserOperations<\/strong>.Validates them by checking: \ud83d\udd39 Signatures \ud83d\udd39 Gas limits and balances \ud83d\udd39 The validateUserOp() function in the smart contract\u00a0wallet.Packs UserOperations<\/strong> into a regular Ethereum transaction<\/strong> and sends it to the blockchain.<\/p>\n Without a Bundler, AA wallets wouldn\u2019t work<\/strong>, as normal transactions require an EOA\u00a0sender<\/strong>.<\/p>\n But who pays for gas? That\u2019s where Paymasters<\/strong> come\u00a0in.<\/p>\n A Paymaster<\/strong> is a smart contract that sponsors gas\u00a0fees<\/strong>.<\/p>\n It allows:<\/p>\n \ud83d\udd39 Users to pay gas in any ERC-20\u00a0token<\/strong>.<\/p>\n \ud83d\udd39 DApps to sponsor transactions<\/strong> for better\u00a0UX.<\/p>\n \ud83d\udd39 Gasless transactions where users don\u2019t pay at\u00a0all.<\/p>\n Without a Paymaster, AA wallets still need ETH<\/strong> for gas, which brings us back to the original\u00a0problem.<\/p>\n To understand this process better, I built Minimal Bundler<\/strong>\u200a\u2014\u200aa simple Bundler implementation that works with Biconomy\u2019s AA infrastructure.<\/p>\n It does the following:<\/p>\n Accepts ERC-4337 UserOperations<\/strong>.Uses two different EOAs to send transactions (to avoid failures).Works on Sepolia\u00a0testnet<\/strong>.<\/p>\n Here\u2019s how Minimal Bundler<\/strong> processes a UserOperation<\/strong>:<\/p>\n import { This function:<\/p>\n 1\ufe0f\u20e3 Picks a wallet (to prevent stuck transactions).<\/p>\n 2\ufe0f\u20e3 Encodes a UserOperation<\/strong> for the EntryPoint contract.<\/p>\n 3\ufe0f\u20e3 Sends it as a transaction<\/strong>.<\/p>\n Check the Minimal Bundler repo<\/strong> to see the full implementation: GitHub<\/strong><\/a><\/p>\n You can test by sending a UserOperation<\/strong> request:<\/p>\n { Account Abstraction<\/strong> is a game-changer for Ethereum UX. Bundlers<\/strong> and Paymasters<\/strong> make it possible to: \u2714\ufe0f Remove the need for EOAs. \u2714\ufe0f Allow gas payments in any token. \u2714\ufe0f Enable more flexible authentication.<\/p>\n Want to see it in action? Try Minimal Bundler now!<\/strong>\u00a0\ud83d\ude80<\/p>\n References:<\/strong><\/p>\n GitHub Repo<\/a>Biconomy<\/a>Biconomy SDK\u00a0Examples<\/a><\/p>\n My Links:<\/strong><\/p>\n Links<\/a> | BuyMeACoffe<\/a><\/p>\n Understanding Account Abstraction (AA) and How Bundlers Work\u200a\u2014\u200aA Deep Dive with Minimal Bundler<\/a> was originally published in Coinmonks<\/a> on Medium, where people are continuing the conversation by highlighting and responding to this story.<\/p>","protected":false},"excerpt":{"rendered":" Understanding Account Abstraction (AA) and How Bundlers Work\u200a\u2014\u200aA Deep Dive with Minimal\u00a0Bundler Ethereum has come a long way from its inception, and one of the most talked-about advancements in recent years is Account Abstraction (AA). But what does AA actually do? How do Bundlers and Paymasters work? And most importantly, why does this change how […]<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-44294","post","type-post","status-publish","format-standard","hentry","category-interesting"],"_links":{"self":[{"href":"https:\/\/mycryptomania.com\/index.php?rest_route=\/wp\/v2\/posts\/44294"}],"collection":[{"href":"https:\/\/mycryptomania.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mycryptomania.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/mycryptomania.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=44294"}],"version-history":[{"count":0,"href":"https:\/\/mycryptomania.com\/index.php?rest_route=\/wp\/v2\/posts\/44294\/revisions"}],"wp:attachment":[{"href":"https:\/\/mycryptomania.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=44294"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mycryptomania.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=44294"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mycryptomania.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=44294"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\ud83d\udca1 The Problem with\u00a0EOAs<\/h3>\n
\ud83d\udd25 What is Account Abstraction (AA)?<\/h3>\n
\ud83d\ude80 How Transactions Work in Account Abstraction<\/h3>\n
\ud83d\udd04 What is a\u00a0Bundler?<\/h3>\n
\ud83d\udcb0 What is a Paymaster?<\/h3>\n
\ud83d\udee0\ufe0f Building a Minimal Bundler (with\u00a0Code)<\/h3>\n
Key Code: Handling a UserOperation<\/h3>\n
createWalletClient,
createPublicClient,
encodeFunctionData,
http,
} from “viem”;
import { sepolia } from “viem\/chains”;
import { privateKeyToAccount } from “viem\/accounts”;
import ENTRY_POINT_ABI from “..\/..\/abis\/EntryPointAbi.json”;
import { env } from “..\/..\/config\/env”;const ENTRY_POINT_ADDRESS = “0x5ff137d4b0fdcd49dca30c7cf57e578a026d2789”;const walletClient1 = createWalletClient({
chain: sepolia,
transport: http(env.RPC_URL),
account: privateKeyToAccount(`0x${env.PRIVATE_KEY_1}`),
});const walletClient2 = createWalletClient({
chain: sepolia,
transport: http(env.RPC_URL),
account: privateKeyToAccount(`0x${env.PRIVATE_KEY_2}`),
});const publicClient = createPublicClient({
chain: sepolia,
transport: http(env.RPC_URL),
});let pick = 0;function pickWalletClient() {
pick = 1 – pick; \/\/ flip 0 -> 1, 1 -> 0
return pick === 0 ? walletClient1 : walletClient2;
}export async function handleSingleUserOp(userOp: any) {
try {
const walletClient = pickWalletClient();
const [beneficiary] = await walletClient.getAddresses(); const data = encodeFunctionData({
abi: ENTRY_POINT_ABI,
functionName: “handleOps”,
args: [[userOp], beneficiary],
}); console.log(“\ud83d\udd39 Encoded handleOps calldata”); const txHash = await walletClient.sendTransaction({
to: ENTRY_POINT_ADDRESS,
data,
}); console.log(`Transaction sent: ${txHash}`); return { transactionHash: txHash };
} catch (err) {
console.error(“Error in handleSingleUserOp:”, err);
throw err;
}
}<\/p>\n\ud83d\udee0\ufe0f Testing the\u00a0Bundler<\/h3>\n
API Endpoint: eth_sendUserOperation<\/h3>\n
“jsonrpc”: “2.0”,
“method”: “eth_sendUserOperation”,
“params”: [{
“sender”: “0x…”,
“nonce”: “0x…”,
“initCode”: “0x…”,
“callData”: “0x…”,
“signature”: “0x…”,
“paymasterAndData”: “0x”,
“maxFeePerGas”: “0x…”,
“maxPriorityFeePerGas”: “0x…”,
“verificationGasLimit”: “0x…”,
“callGasLimit”: “0x…”,
“preVerificationGas”: “0x…”
}, “0x5ff137d4b0fdcd49dca30c7cf57e578a026d2789”],
“id”: 1
}<\/p>\n\ud83c\udfaf Conclusion<\/h3>\n