Studio currently handles a single isolated infinite loop reasonably well, however when there is an infinite loop in a RunService callback Studio becomes (almost) unresponsive. It is difficult to cancel the testing session, as I need to spam F6 or spam click on the stop button and wait until it works.
To reproduce this, just paste this code into a server script and run Play Solo, or run it in the command bar during Play Solo:
game:GetService("RunService").Heartbeat:Connect(function() while true do end end)
There were also a few times where having this scenario happen would permanently break the studio session (e.g. parts of the studio UI would render as white rectangles and buttons would not respond to clicks/hovers.) This was using the New Studio UI Beta. However the repro above doesn’t seem to trigger this.