Worked on the gdsfactory/gdsfactory repository to enhance the robustness and reliability of core photonic component modeling. Focused on improving the MZI arm length calculation by addressing edge-case scenarios where negative delta_length values could cause runtime errors. Applied backend development and software debugging skills in Python to implement a sign-aware calculation, ensuring correct operation even when length_y is small. Delivered a production-quality patch that prevents ValueErrors and reduces the risk of incorrect modeling in edge conditions. The work contributed to the stability of the core library, emphasizing careful handling of numerical edge cases in photonic design workflows.