Developed and delivered the Configurable Reasoning Effort Level feature for the openai/codex repository, enabling users to adjust the model’s reasoning depth via a new --reasoning-effort command-line flag. This addition allows for dynamic tuning between response quality and latency, addressing varying workload and customer requirements. The work involved designing a maintainable CLI and configuration architecture in Rust, with careful attention to backend integration and version-controlled release practices. By focusing on user-driven customization, the feature enhanced flexibility and control over model behavior. Demonstrated proficiency in Rust, backend development, and command-line interface design throughout the end-to-end feature implementation process.