Christoph Reinsch updated the angular/angular-cli repository’s documentation to reflect the transition from Karma to Vitest as the default test runner in Angular 21. He focused on aligning workspace README templates and contributor guidance with this change, ensuring that new and existing contributors receive accurate, up-to-date information about the testing stack. Using Angular and Markdown, Christoph revised documentation to clarify Vitest usage, which helps streamline onboarding and reduces confusion for developers working with the latest Angular version. The work was limited in scope to documentation updates, with no bug fixes or feature development beyond this targeted improvement in technical communication.