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.

We develop crypto wallets turnkey — from custodial solutions for fintech to smart contract accounts on EIP-4337. 5+ years in blockchain development, 40+ projects implemented. Let's examine which architecture to choose for your task and why MPC or Account Abstraction solve the private key problem that MetaMask and classic HD wallets could not close.

Why are classic wallets dangerous for business?

A seed phrase in a browser extension is the only way to restore access. For retail users, this is a barrier to entry (lost phrase = lost money). For corporate treasuries, it is incompatible with compliance (KYC/AML, role model, multisignature). Any single key leak compromises all funds. These risks are built into the architecture, not poor UX.

We eliminate them at the protocol level: MPC wallets (key never fully assembled), smart contract wallets (authorization logic in code), hardware HSM for institutional storage. Details below.

What is the real difference between custodial and non-custodial?

Custodial — the provider stores the private key. User authenticates via email/password/OAuth. Recovery is trivial, KYC/AML built-in. For centralized financial applications, often the only regulatory acceptable option. Risk: single point of failure (e.g., Bitfinex hack — $72M, FTX — $600M+ client funds).

Non-custodial — keys are with the user. Provider has no access to funds. Storage responsibility falls on the user. For 99% of people, this model is unworkable without additional protection — hence MPC.

MPC wallets: the key that doesn't exist

Multi-Party Computation (MPC) is a cryptographic protocol that allows multiple parties to jointly sign a transaction without revealing their partial secrets. The private key never exists in its assembled form.

Standard scheme: 2-of-3 MPC between user (share on device), provider server, and backup cloud storage. Transaction is signed by any two of three parties. Lost phone — recovery via server + cloud. Server compromised — attacker holds only one share, signing impossible.

TSS (Threshold Signature Scheme) is a concrete implementation of MPC for ECDSA/EdDSA. Algorithms: GG18, GG20, CGGMP21 (the latter is faster and has better security proofs). Libraries: tss-lib (Go, from Binance), multi-party-sig (Go, from Coinbase), ZenGo-X/multi-party-ecdsa (Rust).

MPC requires no on-chain changes — to the blockchain, the signature looks like a normal single-key signature. This saves gas and keeps the key management scheme confidential (not published in chain) — unlike multisig.

Account Abstraction (EIP-4337): smart contract as wallet

EIP-4337 completely changes the model: instead of EOA (Externally Owned Account), a smart contract Account is used. Authorization logic is in contract code, not in protocol cryptography. This opens up arbitrary signing logic, social recovery, session keys, sponsored transactions, and batch operations.

How the EIP-4337 stack works:

User → UserOperation → Bundler → EntryPoint contract → Account contract
                                          ↑
                                    Paymaster (optional, pays gas)

UserOperation — a new type of object (not an L1 transaction). Bundler collects UserOps from an alternative mempool, packs them into one transaction, and sends to EntryPoint. EntryPoint calls validateUserOp on the Account contract — Account decides if the signature is valid.

Practical capabilities:

Social recovery. The contract stores a list of guardians (other addresses or a service). Lost key — guardians vote for replacement. Argent has used this scheme since 2020.

Session keys. A temporary key with limited rights: interaction only with a specific contract, until a certain date, up to a certain amount. For GameFi and dApps — user does not sign every micro-transaction.

Paymaster. A third-party contract pays gas for the user. Onboarding pattern: user does not hold ETH, gas is sponsored by dApp or taken from ERC-20 tokens.

Implementations: Safe{Core} Protocol, Biconomy SDK (Stackup), ZeroDev (Kernel), Alchemy (Rundler bundler). EntryPoint v0.6/v0.7 is deployed and active on Ethereum mainnet, Polygon, Arbitrum, Optimism. We guarantee compatibility with the latest contract versions.

What is a Hardware Security Module for corporate wallets?

For treasuries and institutional storage: HSM (Hardware Security Module). The key is generated and never leaves the secure chip. Signing happens inside the HSM. Hardware attestation is supported. Solutions used: AWS CloudHSM, Azure Dedicated HSM, Thales Luna, YubiHSM 2 (for small volumes). Integration via PKCS#11 or cloud-specific API.

A combination of HSM + MPC is optimal for institutional use: key shares are stored in HSMs on different servers/jurisdictions, signing via TSS. This ensures compliance with regulatory requirements (e.g., for crypto custodians).

Integration with dApps: WalletConnect and standards

Any wallet must be able to interact with dApps. Standard: WalletConnect v2 (Sign API): QR code or deep link, peer-to-peer encrypted channel via relay server. For browser extensions: EIP-1193 (Ethereum Provider API).

On the frontend, we use wagmi + viem — one interface for MetaMask, WalletConnect, Coinbase Wallet, injected providers. For Account Abstraction: EIP-5792 (wallet capabilities) and EIP-7677 (paymaster service).

Development process

1. Threat model — who is the user (B2C, B2B, institutional), what operations, what is the acceptable risk model. Architecture depends on this.
2. Selection and design of key storage scheme — MPC, HSM, multisig, or a combination.
3. Development of Account contract (if EIP-4337) or integration of MPC library.
4. Backend — MPC coordination, session management, paymaster service (if needed).
5. Mobile/browser application — UI with WalletConnect integration, biometrics, QR.
6. Integration with dApps — EIP-1193, WalletConnect v2.
7. Audit of contracts and cryptographic implementations — mandatory step. MPC libraries have known vulnerabilities (GG18 susceptible to attack with malicious participant without abort protocol). We use libraries with up-to-date security reviews (CGGMP21). Experience passing audits with Certik, Hacken, Trail of Bits — we have certificates.

What is included in the work (deliverables)

• Source code of smart contracts (Solidity/Rust) with documentation
• Backend MPC coordination service (Go or Rust) with API
• Mobile application (iOS/Android) or browser extension
• Integration with WalletConnect, Ledger/Trezor (if required)
• Preparation for security audit (vulnerability report)
• Administrator and user documentation
• Access to repository, CI/CD, monitoring (Tenderly, Etherscan API)
• Training of your team (2-3 sessions)
• Post-launch support — 1 month

Timeline and cost

Cost is calculated individually for your project. We will estimate within one day — contact us by email or Telegram. We provide a guarantee on code and timeline.

Typical mistakes in crypto wallet development (and how to avoid them)

• Using outdated MPC libraries — GG18 without abort protocol. Choose CGGMP21 or tss-lib with up-to-date audit reports.
• Tight coupling to a single blockchain — not abstracting for L2/sidechains. Use viem/wagmi for cross-chain.
• Ignoring MEV attacks — when using multisig without timelocks. Add tx simulation (Tenderly) and sandwiching protection.
• Lack of fallback recovery mechanism — for Account Abstraction, not setting up social recovery. Include from the first release.

We eliminate these pitfalls at the design stage — for each project, we create a threat model and security checklist.

Need a reliable wallet with no compromises? Get a consultation from our architect — we will analyze your task and propose an architecture with a precise estimate. Leave a request — we will respond within a day.