This guide covers the steps to add Base Paymaster support for gasless transactions in an existing Wagmi project. It focuses on configuring wagmi.ts, adding Base-specific information, configuring the Coinbase Developer Platform (CDP), and implementing Wagmi’s experimental hooks for onchain actions.

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Initial setup: Configure CDP Account

Create a new CDP account or sign in to your existing account.

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Obtain Paymaster & Bundler Endpoint

In your CDP dashboard, navigate to Onchain Tools > Paymaster. Then click the Configuration tab.

Select the chain, Base or Base Sepolia, you’d like to sponsor transactions on. Then copy the RPC URL in the Paymaster & Bundler endpoint section.

Security

This guide uses environment variables to store the Paymaster & Bundler endpoint obtained from cdp.portal.coinbase.com. The most secure way to do this is by using a proxy. For the purposes of this guide, the endpoint is hardcoded into our project file. For production, we highly recommend using a proxy service.

Add this key to your .env file as NEXT_PUBLIC_CDP_PAYMASTER or set up a proxy service for production applications.

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Whitelist Contracts

In the Contract allowlist section, add the smart contract addresses you want to interact with using the Base Paymaster. Give each contract a name and be sure to include the specific functions as well as the contract address. Then click Add.

WalletConnect Project ID

Base Wallet (FKA Coinbase Smart Wallet) requires a WalletConnect project ID to work. If you don’t have one, please obtain one (free) from their website.

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Add Base to Wagmi configuration

Open your project’s wagmi.ts to configure your project to support the Base network, WalletConnect, and Coinbase Wallet connectors:

wagmi.ts:

import { http, cookieStorage, createConfig, createStorage } from 'wagmi';
import { base } from 'wagmi/chains';
import { coinbaseWallet, injected, walletConnect } from 'wagmi/connectors';

export function getConfig() {
  return createConfig({
    chains: [base],
    connectors: [
      injected(),
      coinbaseWallet(),
      walletConnect({ projectId: process.env.NEXT_PUBLIC_WC_PROJECT_ID }),
    ],
    storage: createStorage({
      storage: cookieStorage,
    }),
    ssr: true,
    transports: {
      [base.id]: http(),
    },
  });
}

declare module 'wagmi' {
  interface Register {
    config: ReturnType<typeof getConfig>;
  }
}

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Implement Wagmi Hooks

For the onchain actions (minting, etc.) of your application, use Wagmi’s experimental hooks to manage wallet connection, check for paymaster capabilities, and execute onchain actions with you whitelisted contracts.

  • useCapabilities: Retrieves the capabilities supported by the connected wallet, such as paymasterService for gasless transactions.
  • useWriteContracts: Executes onchain write actions, here used to call the mintTo function on the NFT contract.

Here’s an example for a onchain action to mint an NFT:

mint/page.tsx

'use client';
import { useAccount, useConnect, useDisconnect } from 'wagmi';
import { useState, useMemo } from 'react';
import { coinbaseWallet } from 'wagmi/connectors';
import { abi, contractAddress } from '../utils';
import { useCapabilities, useWriteContracts } from 'wagmi/experimental';

export default function MintPage() {
  const { address, isConnected } = useAccount();
  const { connect } = useConnect();
  const { disconnect } = useDisconnect();
  const [isMinting, setIsMinting] = useState(false);

  // Configure `useWriteContracts` to call the mint function on the contract
  const { writeContracts } = useWriteContracts({
    mutation: { onSuccess: () => console.log('Mint successful') },
  });

  const handleMint = async () => {
    setIsMinting(true);
    try {
      writeContracts({
        contracts: [
          {
            address: contractAddress,
            abi,
            functionName: 'mintTo',
            args: [address],
          },
        ],
        capabilities,
      });
    } catch (error) {
      console.error('Minting failed:', error);
    } finally {
      setIsMinting(false);
    }
  };

  // Check for paymaster capabilities with `useCapabilities`
  const { data: availableCapabilities } = useCapabilities({
    account: address,
  });
  const capabilities = useMemo(() => {
    if (!availableCapabilities || !address) return {};
    const capabilitiesForChain = availableCapabilities[address.chainId];
    if (
      capabilitiesForChain['paymasterService'] &&
      capabilitiesForChain['paymasterService'].supported
    ) {
      return {
        paymasterService: {
          url: `https://api.developer.coinbase.com/rpc/v1/base/<YOUR_PAYMASTER_URL>`, //For production use proxy
        },
      };
    }
    return {};
  }, [availableCapabilities, address]);

  return (
    <div>
      <p>
        {isConnected ? `Connected wallet: ${address}` : 'No wallet connected'}
      </p>
      <button
        onClick={
          isConnected
            ? handleMint
            : () => connect({ connector: coinbaseWallet() })
        }
      >
        {isMinting ? 'Minting...' : isConnected ? 'Mint NFT' : 'Connect Wallet'}
      </button>
      {isConnected && <button onClick={() => disconnect()}>Disconnect</button>}
    </div>
  );
}

By following these steps, you have integrated the Base Paymaster into your Wagmi project, allowing for gasless onchain interactions.

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Troubleshooting

If you run into any errors with this tutorial, please check out our troubleshooting guide.