Explore the journey of rewriting tox, a widely-used Python test automation tool, in this 25-minute conference talk from Ubuntu Summit 2023. Delve into the motivations, design decisions, challenges, and lessons learned during the three-year process of reimagining a tool with over 10 million monthly downloads. Discover why the maintainers chose to undertake this significant rewrite, despite conventional wisdom against such projects. Learn about the strategies employed to minimize disruption during the release, the steps taken to ensure future-proofing and modularity, and gain insight into the maintainers' personal motivations. Gain valuable perspectives on when and why to consider rewriting software, and understand the potential benefits of such an endeavor for heavily relied-upon tools in both open-source and corporate environments.