The whole point of “agency” is that there is a principal (you) behind the agent that owns all responsibility. The agent ACTS for you, it does not absorb any liability for those acts — that flows straight back to the principal.

Just because the AI companies have decided to use the word "agent" doesn't means it's legally an agent. It's just a word they chose. Maybe it'll also be found legally to be an agent but it's likely that'll vary depending on the jurisdiction and will take at least a few years and lots of lawyer bills to iron out.