> Yeah the Chat router is busted big time... You have to add "Think hard." to the end of the prompt, or explicitly switch to the Thinking model in the UI.

I don't really get this gripe? It seems no different than before, except now it will sometimes opt into thinking harder by itself. If you know you want CoT reasoning you just select gpt5-thinking, no different than choosing o4-mini/o3 like before.

Your options are now effectively 4o and o3 (GPT-5 and GPT-5 Thinking). There's no equivalent to o4-mini (at least not via ChatGPT -- I think you could emulate it through some combination of gpt-5 model size (-mini?) and reasoning effort).

o4-mini was the best reasoning model in my experience, because it gave you approximately o3 performance in a very small fraction of the time o3 would take.

ChatGPT's GPT-5 Thinking is even worse than o3, it's closer to o3 Pro! Some messages take 4 minutes to get a reply. Which is great when that's what you want, but the niche of "5 seconds to get an actually intelligent response" has been deleted for no good reason.