Worked on improving the reliability of CLI argument parsing in the tailwindlabs/tailwindcss repository, focusing on ensuring that when duplicate command-line options are provided, only the last value is used, consistent with single-value expectations and previous behavior. Addressed this by updating the TypeScript-based parser to handle arrays for duplicate arguments and revising the test suite to validate the new logic. Emphasized backward compatibility with Tailwind v3 semantics, reducing potential misconfigurations and support issues. The work involved CLI development and testing, resulting in a more robust command-line interface that better aligns with user expectations and established usage patterns.