Account Abstraction Integration: Bundler & Paymaster with Pimlico

We often encounter this situation: a client wants to implement Account Abstraction (ERC-4337), but running their own bundler and writing a paymaster contract takes months and requires rare expertise. Pimlico solves this "out of the box" — managed infrastructure that handles validation, packaging, and submission of UserOperations, as well as gas sponsoring. With over 5 years in blockchain development and 50+ successful AA integrations, we ensure a smooth setup. Pimlico is one of the most reliable platforms with a claimed uptime of 99.9%.

Problems Pimlico Solves

Gas complexity for users. Without a paymaster, every user must have ETH to pay gas, which kills UX. Pimlico supports two modes: verifying paymaster (signed permission for sponsoring) and ERC-20 paymaster (gas paid in USDC). The latter keeps users within familiar tokens.

Need for network synchronization. A custom bundler requires understanding the ERC-4337 mempool, handling bundles, and retries. Pimlico abstracts this via a simple REST API — you just send a UserOperation, and the provider handles the rest.

Centralization risks. If you don't want to depend on a single provider, Pimlico offers Alto — an open-source bundler you can deploy yourself. We help set up both managed and self-hosted scenarios.

Why Pimlico is Better Than a Custom Bundler?

Developing a custom bundler costs $50,000–100,000 without considering ongoing support. Pimlico reduces this to $200–500 per month depending on load. You get an SLA of 99.9% and ready infrastructure. For example, a typical dApp processing 100k userOps per month saves $5,000–$10,000 monthly on infrastructure costs after switching to Pimlico.

How We Set Up Pimlico

We use the standard stack: permissionless.js (TypeScript library for AA), viem for blockchain interaction, and the Pimlico API. Below is an example of creating a Safe-based smart account with paymaster sponsoring:

import { createSmartAccountClient } from "permissionless";
import { createPimlicoBundlerClient, createPimlicoPaymasterClient } from "permissionless/clients/pimlico";
import { createPublicClient, http } from "viem";
import { sepolia } from "viem/chains";

const publicClient = createPublicClient({
  chain: sepolia,
  transport: http("https://rpc.ankr.com/eth_sepolia"),
});

const bundlerClient = createPimlicoBundlerClient({
  transport: http(`https://api.pimlico.io/v2/sepolia/rpc?apikey=${PIMLICO_API_KEY}`),
  entryPoint: ENTRYPOINT_ADDRESS_V07,
});

const paymasterClient = createPimlicoPaymasterClient({
  transport: http(`https://api.pimlico.io/v2/sepolia/rpc?apikey=${PIMLICO_API_KEY}`),
  entryPoint: ENTRYPOINT_ADDRESS_V07,
});

Creating a smart account and sending a sponsored transaction:

import { signerToSafeSmartAccount } from "permissionless/accounts";

const safeAccount = await signerToSafeSmartAccount(publicClient, {
  signer: walletClient,
  entryPoint: ENTRYPOINT_ADDRESS_V07,
  safeVersion: "1.4.1",
});

const smartAccountClient = createSmartAccountClient({
  account: safeAccount,
  entryPoint: ENTRYPOINT_ADDRESS_V07,
  chain: sepolia,
  bundlerTransport: http(`https://api.pimlico.io/v2/sepolia/rpc?apikey=${API_KEY}`),
  middleware: {
    sponsorUserOperation: paymasterClient.sponsorUserOperation,
  },
});

const txHash = await smartAccountClient.sendTransaction({
  to: "0xTarget",
  value: 0n,
  data: "0xCalldata",
});

What Paymaster Types Does Pimlico Support?

Pimlico supports two main paymaster types:

ERC-20 paymaster requires fetching token quotes (getTokenQuotes) and approving the token on the paymaster contract. Pimlico provides ready-made methods for this.

Integration Process

1. Analysis — choose smart account implementation (Safe, Kernel, Biconomy) and paymaster type.
2. Design — design architecture: which operations to sponsor, limits, fallback.
3. Implementation — connect permissionless.js, configure Bundler and Paymaster, write tests.
4. Testing — deploy on Sepolia/Goerli, test all scenarios (revert, gas shortage, spam).
5. Deployment — switch to mainnet, set up monitoring (Tenderly, Etherscan).

How to Set Up Paymaster for Gas Sponsoring?

For sponsored transactions, the paymaster signs a permission for a specific UserOperation. In permissionless.js, this is done via middleware:

const sponsorResult = await paymasterClient.sponsorUserOperation({
  userOperation: userOp,
}); // Returns paymasterAndData (V0.6) or paymaster + paymasterData + gas limits (V0.7)

What's Included in the Work

• Ready integration of Bundler and Paymaster with Pimlico.
• Selection and setup of smart account (Safe or Kernel).
• Configuration of sponsoring policies (limits, contract whitelist).
• Testnet testing with coverage of edge cases.
• Integration documentation for your team.
• Warranty: 2 weeks of post-release support.

Clients typically save $5,000–$10,000 per month after switching to Pimlico. The exact figure depends on transaction volume and number of chains.

Timelines and Pricing

Integrating a basic AA flow with Pimlico typically takes 1 to 2 weeks. We offer a turnkey solution — from analysis to deployment, all inclusive. Pricing is calculated individually based on the complexity of paymaster policies, number of supported chains, and documentation requirements. Contact us for a free project estimate and consultation on choosing the optimal plan.