Worked on the carbon-language/carbon-lang repository to enhance runtime reliability by implementing a safe default return value for the Run function when no explicit return type is provided. Using C++ and leveraging LLVM for compiler infrastructure, introduced logic to default the return value to int32 0, thereby preventing the propagation of garbage values from uninitialized memory. Adjusted the lowering path and LLVM IR generation to support this new behavior, ensuring predictable program exit semantics. Updated both code and documentation to reflect these changes, focusing on stability and clarity in runtime behavior. The work demonstrates depth in compiler design and runtime safety.