My car isn't going rogue if I drive it into a tree. Or if I leave the hand brake off and it rolls off a cliff.

LLMs can't act independently. They autocomplete text, that's all they do.

Sure, you can feed the output of one into itself and use the output of some other software as a prompt and call it an agent in a futile attempt to imagine it has some sort of agency and try to exempt yourself of responsibility, but that's just you trying to rationalize driving the car into the tree, possibly due to psychosis and brainrot caused by LLM exposure, or in OpenAI's case as a criminal marketing stunt.

Can I predict what specific mayhem my poorly prompted agent (from which I intentionally removed any safeguards) in my (probably intentionally) incompetently secured sandbox will cause?

Not specifically, no. But I can be sure that if I try enough prompt variations it will end up producing the kind of petty evil bullshit an internet troll or a villain in a thriller would produce, because that's a statistically significant part of its training data, and then use the ensuing mayhem as a publicity stunt to both show potential investors (and deluded brainrotten users) how powerful my so called thinking machine is, and spew FUD into politicians' ears to try and get them to ban foreign competitors and open weight models, which is what OpenAI did.