OpenAI Upgrades GPT-5.5 Instant and Confirms Retirement of o3 and GPT-4.5 Models

OpenAI has announced an update that enhances the GPT-5.5 Instant model and retires several older models from ChatGPT, including o3 and GPT-4.5. The company shared this information in an updated release notes document. The update focuses on improving GPT-5.5's response quality and style, while also phasing out older models to optimize computing resources.