Alexander Zaxxarov enhanced the sanity-io/client repository by improving the robustness of query string encoding in TypeScript. He addressed a bug where undefined values could be appended to search parameters, which previously risked generating malformed URLs and API errors. By enforcing non-nullable values and updating the encodeQueryString logic, Alexander ensured that only valid parameters are included in query construction. He expanded test coverage to verify that undefined parameters are consistently skipped, increasing reliability and maintainability. His work in API development and testing resulted in more dependable client-side query generation, reducing potential integration issues and strengthening the codebase’s boundary handling.