Atsushi Nakatsugawa's article discusses the improvements made to the GPT-5 Codex model, particularly in its application for AI-driven code reviews. The enhancements focus on addressing the perceived noise in GPT-5 by improving the signal-to-noise ratio (SNR) without sacrificing bug detection capabilities. Through the introduction of the GPT-5 Codex, which includes product changes like severity tagging and stricter refactoring suggestions, the model achieves a 35% increase in comment precision while reducing comment volume by 32%. The Codex is particularly adept at identifying complex concurrency issues and API pitfalls, offering more actionable feedback with a focus on providing diff suggestions. Despite an increase in overall comment quantity compared to pre-GPT-5 levels, the acceptance rate of useful comments has returned to previous norms. The article highlights Codex's low-latency performance and flexibility, which contribute to faster feedback loops and a more streamlined code review process. While Codex maintains robust bug detection, further improvements are planned to address coverage gaps and optimize refactoring suggestions.