During January 2026, Vjeux focused on improving function type formatting in the prettier/prettier repository, addressing a nuanced bug affecting optional and nullable function return types. Using JavaScript and front end development skills, Vjeux refined the logic for parentheses detection to ensure correct formatting and better TypeScript type inference, particularly for nullable arrow functions. The work included adding targeted tests to validate the new behavior and prevent regressions, emphasizing maintainability and correctness. By concentrating on a single, well-defined bug fix and enhancing test coverage, Vjeux contributed to a more stable developer experience for TypeScript codebases relying on Prettier.