Worked on stabilizing the Spawn API within the tier4/scenario_simulator_v2 repository, focusing on improving reliability and maintainability in simulation workflows. Addressed a bug where applyAddEntityAction could be called without a required MiscObjectBehavior parameter by introducing a default behavior path through a new struct and static method in api.hpp. This ensured entities without explicit behaviors would spawn correctly, reducing edge-case failures. Additionally, performed code formatting and linting cleanup in add_entity_action.cpp, standardizing argument placement and removing trailing whitespace. Utilized C++ for API development and simulation, emphasizing code quality and adherence to API contracts throughout the debugging and enhancement process.