Hey, this is a known issue: the sidebar position resets when you switch layouts with Cmd+E. This was fixed before, but it looks like the regression is back.
Try this workaround: open settings.json (Cmd + Shift + P > “Preferences: Open User Settings (JSON)”) and add:
"workbench.sideBar.location": "right"
Then restart Cursor. Honestly, it doesn’t help everyone, but it’s worth a try.
I should add that, previously I was able to tell if I was on the Agent or Editor layout by the background color of the agent chat (which was already fairly obscure, but that’s a different problem). It was darker when in the Editor layout, and lighter in the Agent layout. Now, however it’s always the same lighter color as when I am in the Agent layout.