OpenAI has switched ChatGPT’s default engine to GPT-5.5 Instant, a model that slashes hallucinated statements by more than half in internal tests and trims inaccurate replies by over a third. The upgrade also delivers leaner, more direct answers, quicker file searches and a new “memory sources” feature that lets users see and manage the context used to personalize responses. Plus and Pro subscribers receive the change today; other tiers will follow in the coming weeks. Read more →