This is a known bug. When Max Tab Count = 1, the tab replacement logic gets stuck in a loop, which causes a crash and high CPU usage.
Workaround: set Max Tab Count to 2 or higher. This should prevent the crash, and you’ll be able to create new agents normally.
The team is aware of the issue, but there’s no ETA for a fix yet. Your report helps us prioritize it.
Closing this as a duplicate. The same issue was discussed here: Cursor Crashes on New Agent