May 2026 monthly summary: Focused on reliability, safety, and measurable business impact across two critical repositories. Micrometer delivered a strict nullability contract for Meter.match using JSpecify, removing the previous workaround and updating tests to enforce stronger type safety, reducing null-related runtime risks. Spring Kafka introduced an advanced acknowledgment mode enabling count/time-based offset commits and improved batch rollback handling by treating an empty record list as null, increasing robustness in both typical and edge-case scenarios. These changes support more predictable metrics collection and safer, more flexible message processing in production. The work also included cross-repo consistency and tests adjusted for the new semantics to improve long-term maintainability and release stability.Overall impact: higher reliability, lower risk of regression in offset management and metric processing, and clearer contracts for API consumers. Technologies/skills demonstrated: Java type system (nullability with JSpecify), test-driven development, AGs for null-safety, Kafka offset management, and cross-repo cherry-picking for multi-release support.