Worked on the microsoft/typespec repository, focusing on improving the reliability of decorator usage by addressing a critical correctness bug related to argument mutation. Applied TypeScript and full stack development skills to implement a safety fix that ensures types within decorator arguments are properly mutated, preventing errors from unmutated references. This change enhanced runtime stability and made mutation behavior more predictable for downstream tooling that depends on consistent semantics. The solution, developed collaboratively and tested for robustness, reduced the likelihood of runtime errors and improved maintainability of the mutation pipeline, reflecting a thoughtful approach to quality and correctness in TypeScript-based systems.