OpenAI retires GPT-5.5 from ChatGPT and Codex as older APIs face sunset
On October 14, OpenAI retired GPT-5.5 from ChatGPT, ChatGPT Work and Codex sessions signed in with a ChatGPT account, while API access and API-key Codex sessions remain unaffected. Specified versions of GPT-4o, GPT-4o mini, GPT-4.1 and GPT-4.1 mini are also counting down to discontinuation on January 14, 2027, leaving developers roughly three months to migrate; OpenAI advises checking model settings on older tasks and switching to replacement versions. Reports say GPT-5.5 shipped in April 2026 and was superseded by GPT-5.6 and GPT-6 in under six months, and some Reddit users have posted prompt-writing guides to carry its tone and habits into private API setups, citing MentalHealthBench scores — user claims rather than official statements.
Model retirements are becoming routine operations, forcing users to weigh capability upgrades against the loss of familiar interaction habits and conversational continuity.