OpenAI Retires o3 and GPT-4.5 From ChatGPT, Prioritizes GPT-5.5 Series

According to OpenAI's latest release notes announced today, the company is retiring OpenAI o3 and GPT-4.5 from ChatGPT's web and mobile interfaces to optimize resource allocation and focus engineering efforts on the newer GPT-5.5 flagship series.

GPT-4.5 will enter a 30-day transition period and officially discontinue on June 27, 2026, while o3 will have a 90-day transition window, ending August 26, 2026. ChatGPT paid users can still manually select these models during their respective transition periods. OpenAI's API service remains unaffected, allowing developers to continue accessing both models through API.