This repo has code examples on how to sponsor a mint for a Knight Warriors NFT on Base Sepolia using Coinbase Developer Platform's Paymaster & Bundler. If you'd like to see a live demo app sponsoring NFT mints in action, check out ours here.

We currently have examples for the following SDKs, but contributions are always welcome! See Contributing for more details.

• Alchemy (aa-core)
• Pimlico (permissionless.js)
• ZeroDev (@zerodev/sdk)

• SimpleAccount (default)
• Safe
• Kernel

Prerequisites: you'll need to have node and yarn installed.

git clone https://github.com/coinbase/paymaster-bundler-examples.git

• Copy the env example

cp .env.example .env

• Install dotenv

yarn

• This will setup dotenv to load the env file for private values

• Get your Node RPC URL

  • Navigate to https://www.coinbase.com/developer-platform/products/base-node
  • Sign up for a Coinbase Developer Platform account, if you don't have one already.
  • Under the Build Onchain section in the Portal, select Node
  • In the dropdown on the top right of Configuration, select Base Testnet (Sepolia)
  • Copy your RPC endpoint, and paste it into .env as the RPC_URL variable.
    • The RPC URL should look like https://api.developer.coinbase.com/rpc/v1/base-sepolia/<api_key>

• Add a signer

  You'll need to add a private key to initialize and sign for your ERC-4337 smart contract account

  • Since the NFT mint is free and gas will be sponsored by our Paymaster, you can use a new account without any funds
  • You can create a new private key with Foundry
    • To install Foundry, run curl -L https://foundry.paradigm.xyz | bash
    • To generate a new key pair, run cast wallet new
  • Copy your private key, and paste it into .env as the PRIVATE_KEY variable

• Optional: configure the smart account for Pimlico

  • If you're using Pimlico, you can use a different smart account type by changing the account_type variable in .env
    • Valid values: simple, safe, kernel
    • pimlico/src/account.js is a code example on how to configure a different smart account for SDKs that support this feature

Example for Alchemy

cd examples/alchemy

yarn

yarn dev

You should receive an Etherscan link with your sponsored transaction in the terminal output. Example

Minting to 0xF19CEA17462220437000F459f721e3e393bd1fc9
Waiting for transaction...
 ⛽ Successfully sponsored gas for mintTo transaction with Coinbase Developer Platform!
 🔍 View on Etherscan: https://sepolia.basescan.org/tx/0xe51e9bf6fea0dfecfcbf7168bcc7da2c833ad0dcac5651940953a89857674885
✨  Done in 5.66s.

If you'd like to see an example of an app sponsoring NFT mints in action, check out our demo app here.