What is GPT-5?

GPT-5 is a large language model developed by OpenAI, succeeding GPT-4.5. The material tracks its architecture and efficiency, particularly its reasoning paradigm and token efficiency.

• 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.