OpenAI announced on Tuesday that its latest foundation model, GPT‑5.5 Instant, will replace GPT‑5.3 Instant as the default engine behind ChatGPT. The upgrade targets reduced hallucinations in high‑risk domains such as law, medicine and finance while preserving the low‑latency performance users expect. GPT‑5.5 also scores higher on math and multimodal reasoning benchmarks, and introduces a context‑management feature that lets the model reference past chats, files and Gmail. The changes roll out to Plus and Pro users on the web now, with broader availability slated for mobile and other plans in the coming weeks. Read more →