Stockfish is superintelligence in a very narrow domain. A superintelligent AGI is that concept applied to general intelligence. Whatever you try, it is always several steps ahead. If you ask it to write a program, and you think you found a bug, it’s not a bug, you just misunderstood the code. Anything that you can consider, it can also consider but in more depth.
More speculatively superintelligent AGI implies situations such as: you try to turn it off, but you find that it has already modified its own code, found a zero day and established an outpost on another network that you don’t have access to.