Piyush Goel contributed to the stdlib-js/stdlib repository by focusing on code stability and maintainability through targeted bug fixes and code cleanup. He addressed a memory deallocation issue in the example C file, updating the deallocation logic to ensure the correct object was freed, which reduced the risk of memory leaks and undefined behavior for downstream users. His work involved C programming and careful memory management, as well as linting to align with project standards. While the scope was limited to one bug fix over the month, the changes improved code quality and reliability, demonstrating attention to detail in C development practices.