December 2025: Delivered a comprehensive bidirectional FFI expression round-trip fidelity test for delta-kernel-rs, establishing end-to-end verification of expression semantics across Kernel and Engine boundaries. Implemented new visitor-based translation paths (engine_to_kernel_expression, engine_to_kernel_predicate) and supporting test utilities, fixtures, and deep equality checks to ensure round-trip integrity. Provided clear build/test instructions and documented limitations to guide future enhancements, reducing regression risk and increasing confidence in cross-language code paths. Business value: safer cross-language expressions, improved maintainability, and stronger CI validation.

November 2025 — delta-kernel-rs: Focused on strengthening robustness, maintainability, and API safety while delivering metadata enhancements and housekeeping improvements. Implemented fallible evaluators returning DeltaResult to enable early error reporting and input-schema validation; added optional tags to LastCheckpointHint for richer checkpoint metadata while preserving backward compatibility; removed a stray comment to improve code clarity. Validated changes with comprehensive tests: all 630 kernel tests and 18 FFI tests pass; cargo check --all-features succeeded. The work reduces downstream failures, improves debuggability, and provides a safer foundation for future development.

October 2025 monthly summary focusing on reliability and test robustness for delta-kernel-rs. Key change: added a conditional test skip for the HDFS integration test when Maven is unavailable, preventing false failures in environments without Maven and keeping test visibility intact for explicit runs.