OpenAI GPT-5.6 & Codex: New Guidance from Reddit AMA

OpenAI's Codex team has shared new operating guidance for GPT-5.6 and Codex. This comes after a Reddit AMA where they confirmed Codex now reaches over five million weekly users, a doubling in just three months. Here's the thing: For most coding, OpenAI recommends GPT-5.6 Sol at Medium reasoning. More complex tasks, like migrations or security-sensitive changes, should use Sol Ultra. Terra is for faster work, and Luna handles lightweight operations. What's interesting is that Sol is considered the strongest option for interface work, especially with reference images. It's also faster than GPT-5.5 for many tasks. For Codex users, the team advises giving agents bounded goals and requiring tests. They acknowledged that models can sometimes abandon tasks too quickly. The company also addressed the merged ChatGPT desktop app, stating that ChatGPT Classic and the new app can run side by side. They are working on fixes for various issues, and a Linux desktop app is in development. The bottom line is that these updates provide clearer guidance for developers and users interacting with OpenAI's coding models and applications.