During October 2025, Sebastian Behrisch focused on improving build reliability and code hygiene in the apache/arrow repository, specifically within the Parquet C++ modules. He addressed persistent compiler warnings by implementing missing pragma warning(pop) directives and suppressing warning 4250 across multiple source and header files. To resolve API export inconsistencies, Sebastian introduced the PARQUET_EXPORT macro, ensuring correct symbol visibility for downstream consumers. Working primarily with C++ and build systems, he targeted issues affecting CI stability and integration workflows. Although the work centered on bug fixes rather than new features, it demonstrated careful attention to detail and a strong understanding of compiler behavior.