Worked on the temporalio/sdk-java repository to enhance the robustness of Kotlin-based Temporal workflows and activities. Focused on resolving a bug related to incorrect varargs spreading in child workflow and activity execution, the work involved updating Kotlin extensions to ensure correct argument handling. This fix improved the reliability and correctness of workflow execution, particularly for developers using Kotlin with Temporal. Comprehensive tests were added to cover various varargs scenarios, increasing regression safety and overall test coverage. The engineering effort centered on activity execution, workflow development, and testing, utilizing both Java and Kotlin to deliver a more stable and predictable SDK experience.