Yiyang Yang focused on backend stability and correctness in the cvxgrp/cvxpy-ipopt repository, addressing a critical bug in the DQCP module. He implemented None-safe guards within lazy constraint closures to prevent TypeError exceptions when t.value was unset during verbose evaluation, ensuring robust handling of edge cases. Using Python and leveraging strong debugging and testing skills, he added targeted regression tests to verify that verbose mode no longer crashed when encountering None values. This work improved the reliability of bisection-based evaluation in the DQCP module and demonstrated a careful, test-driven approach to code quality and long-term maintainability within the project.