You want a computer-use agent: it looks at a screen, clicks, types, and you can see what it does. Pieces. The desktop template has XFCE on Xvfb, Chrome, xdotool and scrot. Nothing runs until you start the desktop, so an idle one costs the same as any other sandbox.
1

Start a desktop and take a screenshot

desktop_agent.py
2

Loop: look, decide, act

Send the screenshot to your model, then call move_mouse, left_click, write or the other actions it returns. Desktop lists them.
3

Watch it

desk.live_url() returns a live-view link. With control scope you can take over. For web pages only, the dom channel replays the page with passwords masked: Live view.