According to Greg Brockman on X, developer Christopher Ehrlich used GPT-5.3 Codex to rewrite the 1989 SimCity C codebase into TypeScript and run it in the browser with minimal guidance, demonstrating robust multi-language code transformation at production scale (source: Greg Brockman citing Christopher Ehrlich on X). As reported by the original X thread from Christopher Ehrlich, the workflow required little code reading and limited steering, indicating that GPT-5.3 Codex can infer architecture and translate legacy C patterns into modern TypeScript constructs suitable for web deployment. According to these posts, this showcases practical business use cases for large-scale code migration, legacy modernization, and cross-platform enablement, reducing manual refactoring time and cost for enterprises with C and C++ estates moving to TypeScript and WebAssembly targets.