Worked on the apache/spark repository to restore support for Scala UDFs with Seq[Row] input in Spark 4, ensuring backward compatibility with Spark 3.5 and reducing upgrade friction for Scala users. Addressed a backward-compatibility risk by preserving the None encoder for Seq[Row] arguments, aligning Spark 4 behavior with previous versions. Expanded unit tests to cover additional Scala UDF input types and regression scenarios, improving test coverage and reliability. Demonstrated a thorough approach to code review, continuous integration validation, and open-source contribution workflows. Utilized Scala, Spark SQL encoder mechanics, and Git-based workflows to deliver a targeted bug fix in data processing.