Worked on the IBM/velox repository to enhance observability and diagnostics by integrating plan fragment logging into the TaskListener component. Developed a new callback mechanism in C++ that logs plan fragments alongside task statistics, updating the task completion flow to propagate plan fragments to listeners. This involved refactoring Task::onTaskCompletion and introducing an overload for TaskListener::onTaskCompletion to accept plan fragments, thereby improving end-to-end visibility into task execution. Focused on callback implementation, software design, and refactoring, this work established a stronger foundation for plan-fragment diagnostics and optimization, enabling faster debugging and more targeted performance improvements within the Velox codebase.