Worked on the ueberdosis/tiptap repository to address a critical Markdown parsing issue, ensuring that headings following ordered list items are correctly terminated and rendered as headings in compliance with CommonMark standards. Applied a test-driven approach using TypeScript and Regex to implement the fix, adding comprehensive regression tests to lock in the intended behavior and prevent future regressions. Enhanced the extension-list module by introducing targeted tests and a changeset for the heading lazy continuation scenario, improving Markdown reliability for client documentation and downstream rendering. The work demonstrated a focus on maintainability, standards compliance, and robust automated testing practices.