Worked on the BitGoJS repository to address a critical issue in transaction signing by implementing a robust payload serialization guard. Focused on backend and API development using TypeScript, the work introduced a type-check in the signing path to prevent double-stringification of string payloads, which had previously caused invalid signature errors and disrupted transaction workflows. By aligning the new guard with existing mechanisms in ext-signing-mode, the solution unified payload handling and improved overall signing reliability. This fix reduced support incidents related to signature failures and reinforced defensive programming practices, contributing to more stable transaction processing and enhanced maintainability in the codebase.