Worked on the wevm/viem repository to deliver a critical bug fix focused on Tempo transaction signing and fee token handling. Addressed issues with preserving the feeToken in the broadcast envelope after the fee payer signs, ensuring compliance with TIP-76 and improving on-chain verification. Used TypeScript and backend development skills to enable single round-trip sponsorship by handling prefilled fee payer signatures and correcting serialization paths. The solution stabilized transaction formatting and serialization, reduced envelope errors, and improved reliability for Tempo transactions. This work enhanced protocol compliance and maintainability, resulting in fewer invalid transactions and a better developer experience for blockchain applications.