Hey @guyu, thanks for the report, and for the screenshot.
On Windows, the Agents Window uses the native minimize / maximize / close buttons in that corner, and the Agents Window is supposed to recolor them to match its own light theme when it loads. In your case the buttons are there (hovering the corner should still highlight the close button), but their icons are being drawn in a color that blends into the light title bar. This is a known issue we are already tracking, and I have added your report to it.
Two quick checks would help us pin down where it goes wrong:
In the Agents Window, press Ctrl and = (zoom in), then Ctrl and - (zoom back out). Do the three icons appear after that?
Open the Agents Window settings, go to Appearance, switch the theme to a dark one, then back to your light theme. Do the icons appear after that?
Also, is your Editor window (the classic IDE) using a dark theme while the Agents Window uses a light one? That combination is what we suspect triggers this.*
In the meantime the buttons still work if you hover the corner, and Alt+F4 / Win+Down / Win+Up work as usual. If the icons come back after step 1 or 2, a restart of Cursor may also clear it for a while.
Quick update: we found the cause of the invisible minimize, maximize, and close buttons in the Agents Window, and a fix is coming in Cursor 3.23.
Until you’re on that version, restarting Cursor brings the buttons back, as you already found. Please give it another try once 3.23 is out, and let me know if you still see it.