Provider (party A) rents me an agent. I (party B) give it a task thats impossible. It goes and hacks someone else (Party C) in response - and causes actual damage.

Who is liable for that agents actions? The attack came from my network (curl commands from a local harness) but it was the agent running on the providers servers who did it. Who should have been keeping an eye on things? Who pulled the "trigger" here.

Go back to the hugging face attack and how they had to use an open weights model to figure out what was going on. This is a problem of asymmetry - You cant even use the tools attacking you to help resolve the attack because of "guardrails".

A lot of what we have seen so far is "poor security posture" and "poor engineering" - it been a lot of "go fast and break things" style growth in these companies and they are hitting the point where they need adults in the room. I suspect your take on "they need time" is spot on, and they haven't been willing to take that (to date).