OpenAI Sets Firm Retirement Dates for GPT-4.5 and o3 in ChatGPT

OpenAI has set firm retirement dates for GPT-4.5 and o3 in ChatGPT, with GPT-4.5 retiring on June 27, 2026, and o3 on August 26, 2026. These changes primarily affect Custom GPT builders and ChatGPT Enterprise teams, while GPT-5.5 Instant became the default in May 2026.