OpenAI has made changes to the models used in ChatGPT, with reports indicating the retirement of certain models, including GPT-4 and possibly GPT-4o. However, there is uncertainty about which models are being replaced and with what, as some outlets mention new models such as GPT-4o, GPT-5.5 Instant, and GPT-Live, while others refer to Workspace Agents. The changes have reportedly prompted strong reactions from users, with some expressing sadness and anger over the retirement of certain models.