During January 2026, Zhang focused on backend development and unit testing in the apache/paimon repository, addressing a critical issue in table schema validation using Java. Zhang implemented a bug fix that enforces the sequence group requirement for aggregate functions, resolving a gap that previously risked table unavailability in production environments. The solution involved strengthening the validation logic to ensure tables with aggregate functions cannot be created without proper sequence group definitions. To support this change, Zhang added automated test coverage, safeguarding against future regressions. This work improved reliability and data correctness, demonstrating careful attention to code quality and robust change management.