What is GPT-5?

GPT-5 is a large language model developed by OpenAI, succeeding GPT-4.5.

• Dec 2025 - Mike Israetel said GPT-5 is built on OpenAI’s architecture, exploiting a reasoning paradigm that GPT-4.5 lacked, making it “super super token efficient.”
• Jun 2026 - Nathan Labenz noted that MAI outperformed GPT-5 on quality while being 10x lower in cost.
• Jun 2026 - Nathaniel Whittemore said a new Cursor model is the same size as Claude Opus and GPT-5, trained from scratch, with 10 to 20x more compute than composer, and is generally intelligent, not just coding.