OpenAI ships GPT-5.6 with three models, five thinking levels, and an Ultra sub-agent mode

How to use GPT-5.6

GPT-5.6 ships as Luna, Terra, and Sol, each with five thinking levels (light to max) plus an Ultra mode that spins up sub-agents aggressively. The macOS ChatGPT and Codex apps merge into ChatGPT Work; a new ChatGPT Sites plugin builds hosted pages with optional ChatGPT login. Sol excels at UI and writing, especially with references; Terra feels like a steerable 5.5 upgrade; Luna has a mini-model vibe—fuzzy on ambiguous prompts but solid on clear tasks. Higher thinking levels burn usage fast, and OpenAI temporarily removed the 5-hour cap while fixing merge bugs, so weekly limits can vanish in one session. Also: Claude Code gets an in-app browser and multiplayer Artifacts, Meta launches multimodal Muse Spark 1.1 via API, and Apple sues OpenAI over alleged trade-secret theft for AI hardware.

Why it matters: GPT-5.6 going GA is one of the week's biggest product stories, and the three-model lineup with Ultra mode is worth practitioner attention. Docked because this is a tutorial recap rather than the primary release post, and the body is truncated with key details missing.