OpenAI released GPT-5, the first model to unify its two lineages: a fast model for most queries, a deeper 'thinking' model for hard problems, and a real-time router that picks between them based on the task. Users no longer had to choose a model — the system decided.

OpenAI reported gains over GPT-4 in coding, writing, health answers, and factual accuracy, with lower hallucination rates and stronger agentic tool use. It shipped across ChatGPT, Microsoft Copilot, and the API on day one.

GPT-5 became the base of the 5.x generation, which OpenAI iterated rapidly through 5.1, 5.2, and beyond — a faster cadence than any previous flagship line.