OpenAI released GPT-5.5, positioned as the frontier model for coding, research, computer use, documents, spreadsheets, and long-running work. It continued the roughly six-week flagship cadence OpenAI had settled into.

Its run was short: on September 15, OpenAI announced GPT-5.5 would retire from ChatGPT, ChatGPT Work, and Codex on October 14, 2026, directing users to GPT-5.6 Sol or GPT-6 Astra instead.

The brisk retirement underscored how aggressively OpenAI was cycling its lineup — GPT-5.5 lasted barely six months in the main product surfaces.