OpenAI retires GPT-4.5, auto-migrating ChatGPT users to GPT-5.5
OpenAI retired GPT-4.5 from ChatGPT on June 27, completing a 30-day sunset it announced in late-May release notes. Existing conversations on the older model are automatically migrated to the corresponding GPT-5.5 model, and the deprecated version is removed from the model picker. It is a routine but pointed reminder that model lifecycles are short: capabilities that felt cutting-edge a year ago are now being sunset to make room for newer tiers.
Why it matters: Model deprecation is becoming an operational fact of life for anyone building on these APIs. Short sunset windows and forced migrations mean teams cannot treat a specific model version as a stable foundation — pinning versions, testing against successors, and planning migrations are now part of shipping on LLMs.