This repo has code examples on how to sponsor a mint for a Knight Warriors NFT on Base Sepolia using Coinbase Cloud's Paymaster & Bundler.

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

• Alchemy (aa-core)
• Pimlico (permissionless.js)

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

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

• Create your Base Node RPC URL

  • Navigate to https://coinbase.com/cloud/products/base/rpc
  • Sign up for a Coinbase Cloud account, if you don't have one already
  • Create a project, and select Base Sepolia
  • Click "Activate" on the Paymaster & Bundler modal
  • Copy your RPC endpoint, and paste it into config.json as the rpc_url variable.

• 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 config.json as the private_key variable

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 Cloud!
 🔍 View on Etherscan: https://sepolia.basescan.org/tx/0xe51e9bf6fea0dfecfcbf7168bcc7da2c833ad0dcac5651940953a89857674885
✨  Done in 5.66s.