GPT-5 isn’t really a brand-new model in the way people think. From what I’ve seen, the goal was more about reducing costs and unifying the interface than releasing a totally different architecture. Under the hood it is still routing to models we already know, just picking what it thinks will give the “best” result for the request.
That can be fine for a lot of general use cases, but if you’re working in specific domains like coding agents or high-precision summarization, that routing can actually make results worse compared to sticking with a model you know performs well for your workload.
Thats not what OpenAI are claiming. They are claiming that there are two new flagship models and a router that routes between them.
"GPT‑5 is a unified system with a smart, efficient model that answers most questions, a deeper reasoning model (GPT‑5 thinking) for harder problems, and a real‑time router that quickly decides which to use"
That can be fine for a lot of general use cases, but if you’re working in specific domains like coding agents or high-precision summarization, that routing can actually make results worse compared to sticking with a model you know performs well for your workload.