Product Updates & Enhancements - OpenAI's Codex has undergone a significant overhaul, featuring an improved agent with a smarter reasoning model (GPT5 codecs) and a rewritten harness for better planning and interaction capabilities [3][4][5] - The Codex CLI has been revamped with simplified approval modes, a more legible UI, and default sandboxing for safety, with frequent updates based on user feedback [6] - Codex is now natively integrated into IDEs like VS Code and Cursor as an extension, attracting 100,000 users within the first week [7] - Codex Cloud has been upgraded to run tasks 90% faster, enabling parallel task execution and remote command through mobile devices [8] Usage & Impact - 92% of OpenAI's technical staff uses Codex daily, a significant increase from 50% in July [14] - Engineers using Codex submit 70% more pull requests (PRs) per week [14] - Code review, powered by GPT5 codeex, is now frequently enabled by default due to its high signal in identifying critical issues [13][14] Code Review & Testing - Codex has been specifically trained for thorough code review, capable of identifying complex bugs and suggesting fixes [12][44] - Codex supports test-driven development (TDD) by running tests, fixing code, and re-running tests until they pass, and can also verify UI visually using snapshots [21][22] - Local code reviews can be performed using slash commands in the CLI, allowing developers to review and fix code before submitting PRs [47][48] Workflow & Scalability - Codex can be used to create detailed plans and specifications for complex features, acting as a "senior engineer" capable of handling its own documentation [32][31] - Codex can sustain productive sessions for over seven hours, processing more than 150 million tokens for large projects [27] - The workflow from idea to pull request can be streamlined into a few steps with Codex, involving rigorous planning and thorough testing [41]