How to Set Up a Paymaster Kit 2026

What a paymaster kit does

A paymaster kit 2026 is the infrastructure layer that allows applications to sponsor gas fees for their users. Under the ERC-4337 account abstraction standard, a paymaster is a smart contract that pays the gas required to execute a user operation on-chain. This tool abstracts the complexity of gas management, allowing end-users to interact with decentralized applications without needing to hold native tokens like ETH or MATIC.

By shifting the cost burden from the user to the application or service provider, paymasters remove the primary friction point in onboarding. Users no longer need to navigate multiple exchanges, bridge assets, or manage complex wallet balances just to pay for transaction fees. This abstraction transforms the user experience from a multi-step financial chore into a seamless interaction focused on the application’s core utility.

Paymaster kits typically offer flexibility in how fees are collected. While the default model involves the dApp paying in the native chain token, many kits support paying gas in ERC-20 tokens or stablecoins. This allows users to pay for transactions using the assets they already hold, further simplifying the flow. The kit handles the logic of validating the user operation, collecting the necessary payment, and settling the gas fees with the bundler, ensuring the transaction is processed efficiently.

Choose your sponsorship model

Selecting the right paymaster type depends on your dApp’s budget, user base, and technical stack. ERC-4337 supports three main models, each handling gas sponsorship differently. Use the table below to compare cost, complexity, and user experience impact.

Standard Sponsorship

The Sponsorship model is the simplest to implement. Your project pays gas fees directly using the native token (e.g., ETH). This approach removes all friction for users, making it ideal for onboarding new users who don’t hold native tokens. However, it requires your project to maintain a balance of native tokens and absorb the cost.

ERC-20 Paymaster

With an ERC-20 paymaster, users pay gas fees in a specific token like USDC. This shifts the cost burden to the user but allows you to avoid holding native tokens. Implementation is slightly more complex because users must approve the paymaster to spend their tokens. This model works well if your users already hold stablecoins.

Verifying Paymaster

The Verifying paymaster offers a conditional gas-free experience. Users only pay gas if certain conditions are met (e.g., they haven’t used the dApp in 30 days). This requires signature verification logic, making it the most complex to implement. It’s best for retaining engaged users while minimizing costs for inactive ones.

Integrate the smart account SDK

To begin, you need to add the Paymaster Kit SDK to your project. This library handles the heavy lifting of constructing User Operations and communicating with the paymaster service. Run the following command in your project directory to install the dependencies.

npm install @paymasterkit/sdk

Once installed, you will initialize the smart account instance. This step connects your application to the underlying account abstraction protocol. You must provide your wallet provider and the chain configuration. The SDK creates a signer instance that can sponsor gas fees on behalf of your users.

import { PaymasterKit } from '@paymasterkit/sdk';
import { createWalletClient, http } from 'viem';

const client = createWalletClient({
  chain: yourChain,
  transport: http(),
});

const paymasterKit = new PaymasterKit({
  apiKey: 'your-api-key',
  chainId: yourChain.id,
});

The final step in this phase is configuring the UserOp builder. This component ensures that your transactions are formatted correctly for the paymaster to process. It attaches the necessary sponsorship data to every outgoing User Operation. Without this configuration, the paymaster will reject your requests because it cannot identify the sponsorship context.

const userOpBuilder = paymasterKit.createBuilder({
  entryPoint: '0x5ff137d4b0fdcd49dca30c7cf57e578a026d2789',
  paymaster: '0xyour-paymaster-address',
});

With the SDK integrated and the builder configured, your application is ready to start sponsoring gas fees. The smart account instance is now linked to the paymaster kit dependencies, allowing seamless transaction processing.

Configure gas sponsorship logic

a Paymaster Kit works best as a sequence, not a scramble through settings. Do the minimum first: confirm compatibility, connect the core hardware, update only when needed, and test the result before adding optional features. That order keeps the task understandable and makes failures easier to isolate. After each step, pause long enough for the interface to finish syncing. Many setup problems are timing problems disguised as configuration problems. If the same step fails twice, record the exact error, restart the smallest affected piece, and retry before moving deeper.

1

Confirm prerequisites

Check compatibility, account access, firmware, network, and physical access before changing the a Paymaster Kit setup.

2

Make one change at a time

Apply the setup steps in order so any connection, pairing, or permission failure is easy to isolate.

3

Verify the result

Test the final state from the app and from the physical device before adding automations or optional settings.

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Next

Test the Paymaster Kit flow

Before moving to production, verify that your Paymaster Kit correctly sponsors transactions on a testnet. This step confirms that the gas sponsorship logic triggers as expected and that the user experience remains seamless for the end user.

1. Deploy to a testnet

Deploy your Paymaster contract and Smart Account factory to a testnet like Sepolia or Holesky. Ensure the contract is verified on the block explorer so you can inspect the sponsorship logic directly. Without a deployed instance, you cannot validate the on-chain behavior.

2. Trigger a sponsored transaction

Use your dApp interface to initiate a transaction that would normally require gas from the user. Check the transaction receipt to confirm that the paymasterAndData field is populated and that the user’s balance remains unchanged. The Paymaster should absorb the gas cost entirely.

3. Verify the user wallet interaction

Open the user’s wallet in your test environment. Confirm that the transaction is signed and submitted without prompting the user for ETH or native tokens. If the wallet requests gas, your Paymaster integration is likely misconfigured or the allowance is insufficient.

4. Check the Paymaster balance

Monitor your testnet Paymaster wallet to ensure it has sufficient funds to cover the sponsored transactions. If the balance drops to zero, subsequent transactions will fail or revert to user-paid gas. Refill the balance to continue testing.

5. Review the transaction logs

Inspect the event logs emitted by your Paymaster contract. Look for PaymasterAccepted or similar events that confirm the operation was accepted. This provides an on-chain audit trail that the sponsorship logic executed correctly.

Common paymaster integration: what to check next

When integrating a paymaster kit, developers often hit specific hurdles around ERC-4337 compliance and gas estimation. Addressing these technical details early prevents runtime failures and ensures a smooth user experience.

Can I accept ERC-20 tokens for gas?

Yes, ERC-4337 paymasters enable dapps and wallets to sponsor user operations using ERC-20 tokens or stablecoins. This requires implementing a verification step where the user approves the paymaster contract to spend their tokens. The paymaster then settles with the bundler in the native chain currency. Always verify token allowances before execution to avoid reverted transactions.

How do I handle gas estimation errors?

User operations have complex gas requirements that differ from standard EOA transactions. If your paymaster kit fails to estimate gas correctly, the bundler will reject the entry. Use the eth_estimateUserOpGas RPC method provided by your entry point contract. Cache these estimates but refresh them periodically, as network congestion can change gas prices rapidly.

What are the security risks of a paymaster?

A paymaster contract holds significant control over user operations. If compromised, attackers could drain funds or spam the network. Always implement strict validation logic in your paymasterValidationData function. Limit the scope of sponsored operations to specific actions or token transfers. Regular audits of your smart contract code are essential to prevent unauthorized gas sponsorship.