Did you, the company who built and sold this SaaS product, offer and agree to provide the service your customers paid you for?
Did your product fail to render those services? Or do damage to the customer by operating outside of the boundaries of your agreement?
There is no difference between "Company A did not fulfill the services they agreed to fulfill" and "Company A's product did not fulfill the services they agreed to fulfill", therefore there is no difference between "Company A's product, in the category of AI agents, did not fulfill the services they agreed to fulfill."
Well, that depends on what we are selling. Are you selling the service, black-box, to accomplish the outcome? Or are you selling a tool. If you sell a hammer you aren't liable as the manufacturer if the purchaser murders someone with it. You might be liable if when swinging back it falls apart and maims someone - due to the unexpected defect - but also only for a reasonable timeframe and under reasonable usage conditions.