Sponsoring Transactions With Pimlico

Pimlico is an Account Abstraction infrastructure provider that enables developers to easily integrate smart accounts and gasless transactions into their Sei applications. This guide will walk you through creating a smart account and sending your first gasless transaction on Sei Testnet using Pimlico’s infrastructure.

Getting Started

Dependencies

To integrate Pimlico into your Sei application, you’ll need to install the following dependencies:


pnpm install permissionless viem dotenv

permissionless.js is a AA SDK that works with any account, paymaster, or bundler implementation - no vendor lock-in.

Setting up Pimlico Dashboard

Before starting the integration:

Visit the Pimlico dashboard
Create an account and generate an API key
Store your API key in a .env file:


PIMLICO_API_KEY='pim_xxxxxxxxxxxxxxxxxxxxxx'

Configuring Pimlico Client

First, let’s set up the necessary clients and configurations.


import { createSmartAccountClient } from 'permissionless';
import { createPimlicoClient } from 'permissionless/clients/pimlico';
import { createPublicClient, http, Hex } from 'viem';
import { privateKeyToAccount, generatePrivateKey } from 'viem/accounts';
import { seiTestnet } from 'viem/chains';
import { toSimpleSmartAccount } from 'permissionless/accounts';
import { writeFileSync } from 'fs';
import 'dotenv/config';
 
// Load environment variables
dotenv.config();
const apiKey = process.env.PIMLICO_API_KEY;
if (!apiKey) throw new Error('Missing PIMLICO_API_KEY');
 
// Generate or load private key
const privateKey =
  process.env.PRIVATE_KEY ??
  (() => {
    const pk = generatePrivateKey();
    writeFileSync('.env', `PRIVATE_KEY=${pk}`);
    return pk;
  })();
 
// Create public client
export const publicClient = createPublicClient({
  chain: seiTestnet,
  transport: http('https://evm-rpc-testnet.sei-apis.com')
});
 
// Create Pimlico client
const pimlicoUrl = `https://api.pimlico.io/v2/${seiTestnet.id}/rpc?apikey=${apiKey}`;
 
export const pimlicoClient = createPimlicoClient({
  chain: seiTestnet,
  transport: http(pimlicoUrl)
});

Creating a Smart Account

Now let’s create a simple smart account instance. This account will be controlled by a single EOA signer:


import { toSimpleSmartAccount } from 'permissionless/accounts';
 
const account = await toSimpleSmartAccount({
  client: publicClient,
  owner: privateKeyToAccount(privateKey as Hex)
});
 
console.log(`Smart account address: ${account.address}`);

For a full list of all supported smart account types in permissionless.js see here

Setting up the Smart Account Client

To interact with the smart account, we need to create a SmartAccountClient:


import { createSmartAccountClient } from 'permissionless';
 
const smartAccountClient = createSmartAccountClient({
  account,
  chain: seiTestnet,
  bundlerTransport: http(pimlicoUrl),
  paymaster: pimlicoClient,
  userOperation: {
    estimateFeesPerGas: async () => {
      return (await pimlicoClient.getUserOperationGasPrice()).fast;
    }
  }
});

Sending a Gasless Transaction

With everything set up, we can now send a gasless transaction from our smart account:


const txHash = await smartAccountClient.sendTransaction({
  to: '0xd8da6bf26964af9d7eed9e03e53415d37aa96045',
  value: 0n,
  data: '0x1234'
});
 
console.log(`Transaction included: ${txHash}`);
return txHash;

Complete Example

Here’s a complete example that puts everything together:


import { createSmartAccountClient } from 'permissionless';
import { createPimlicoClient } from 'permissionless/clients/pimlico';
import { privateKeyToAccount, generatePrivateKey } from 'viem/accounts';
import { createPublicClient, http, Hex } from 'viem';
import { seiTestnet } from 'viem/chains';
import { toSimpleSmartAccount } from 'permissionless/accounts';
import { writeFileSync } from 'fs';
import 'dotenv/config';
 
async function main() {
  // Initialize clients and account
  const apiKey = process.env.PIMLICO_API_KEY;
  if (!apiKey) throw new Error('Missing PIMLICO_API_KEY');
 
  // Generate or load private key
  const privateKey =
    process.env.PRIVATE_KEY ??
    (() => {
      const pk = generatePrivateKey();
      writeFileSync('.env', `PRIVATE_KEY=${pk}`);
      return pk;
    })();
 
  // Create public client
  const publicClient = createPublicClient({
    chain: seiTestnet,
    transport: http('https://evm-rpc-testnet.sei-apis.com')
  });
 
  // Create Pimlico client
  const pimlicoUrl = `https://api.pimlico.io/v2/${seiTestnet.id}/rpc?apikey=${apiKey}`;
 
  const pimlicoClient = createPimlicoClient({
    chain: seiTestnet,
    transport: http(pimlicoUrl)
  });
 
  // Create smart account
  const account = await toSimpleSmartAccount({
    client: publicClient,
    owner: privateKeyToAccount(privateKey as Hex)
  });
 
  console.log(`Smart account address: ${account.address}`);
 
  // Create smart account client
  const smartAccountClient = createSmartAccountClient({
    account,
    chain: seiTestnet,
    bundlerTransport: http(pimlicoUrl),
    paymaster: pimlicoClient,
    userOperation: {
      estimateFeesPerGas: async () => {
        return (await pimlicoClient.getUserOperationGasPrice()).fast;
      }
    }
  });
 
  // Send transaction
  const txHash = await smartAccountClient.sendTransaction({
    to: '0xd8da6bf26964af9d7eed9e03e53415d37aa96045',
    value: 0n,
    data: '0x1234'
  });
 
  console.log(`Transaction included: ${txHash}`);
}
 
main().catch(console.error);

What’s Happening Under the Hood?

When you send a transaction using the smart account client:

The client builds a user operation (a transaction format for smart accounts)
Requests sponsorship from Pimlico’s paymaster
Signs the operation with the smart account owners’s private key
Submits it to Pimlico’s bundler
The bundler monitors the chain until the operation is included in a block

The first transaction will also deploy your smart account contract if it hasn’t been deployed yet.

Conclusion

You’ve now learned how to:

Set up Pimlico’s infrastructure
Create a smart account
Send gasless transactions

This implementation enables a seamless user experience where end users don’t need to worry about gas fees or managing native tokens to interact with your dApp.

For more information about Pimlico and its features, check out:

Join the Pimlico Telegram community to get help and share what you’re building!