It does feel novel.

However, I believe the GUI for AI agents that will win is a plain text editor with a file tree, a terminal pane for coding (or preview pane for other kinds of tasks) and a chat sidebar.

Even if the code editor is not used to type, it's there for psychological safety. It lets you inspect and navigate what is being created. Has tremendous value.

Plain text has survived countless software revolutions, so it's likely to become the dominant format for artifacts produced by AI. Non-plain text things are likely to adapt instead of the other way around.

"Strange terminal commands" have survived, while even poweruser toolbar style have started to fade (I love them, but they're fading away). It clearly has some value (hint: speed over familiarity).

I think the poweruser toolbar style was indeed the only thing in the past couple of decades that really tried to match the terminal for speed of interaction. In my opinion, it succeeded, but it has its limits too (tends to clump with stuff over time; has a limit on the amount of abstractions it can hold). I would love to see a candidate GUI that tackles that speed angle.