GPT-5's auto routing was bad, you'd get off the cuff bad answers for hard questions and overthinking on the banal. Also, with a chatbot the idea is that it's a back and forth but 5 minutes of thinking kills that, whereas fire and forget is core to the idea of autonomous agents.

Agents are going to replace almost all the UI in computers. For a trivial example, things like a control panel or settings menu will cease to exist, you'll handle coarse things via conversation ("set volume to 20%"), and UIs will be presented only for things where chat is cumbersome ("the password for the printer is !-*Donkey_Loves_Shrek^^@"). The UI that remains will become heavily decoupled, like supercharged versions of the office ribbons, with the intent that the agent will compose menu fragments and capability widgets dynamically so you only ever need to see controls for the settings that are relevant and that you care about.