Jack developed a deterministic action configuration system for the Metta-AI/mettagrid repository, focusing on improving test stability and maintainability. He replaced unordered maps with an ordered vector of (name, config) pairs in the GameConfig, ensuring the noop action is always at index zero when enabled. This approach aligned the benchmark configuration with the new vector-based structure, reducing nondeterministic test failures. Jack added targeted tests to verify action ordering and data-structure consistency, addressing test flakiness and supporting future deterministic changes. His work leveraged C++ and Python, emphasizing configuration management, debugging, and testing to enhance code quality and reliability.