John contributed to the wormhole-foundation/native-token-transfers repository by implementing Mantle gas fee estimation support. He extended the existing gas limit calculation logic, which previously handled Arbitrum Sepolia, to include a Mantle-specific value, enabling accurate fee estimation for transactions on the Mantle network. This work, developed using TypeScript and leveraging his expertise in Blockchain Development and EVM, addressed the challenge of cross-network consistency in fee calculations. By focusing on robust engineering rather than bug fixes, John laid the foundation for multi-network fee estimation, reducing the risk of overpaying or failed transactions and supporting smoother Mantle deployments in production environments.