NPS is the loyalty cousin of CSAT. Where CSAT measures the single interaction, NPS measures the relationship, how willing the customer is to recommend you to a friend, on a 0–10 scale.
For AI-handled interactions, NPS is the harder benchmark. A customer can rate the call CSAT 5 and still drop their NPS, because the experience felt efficient but cold, or because something resolved but the customer felt a person should have been involved.
A serious vendor tracks the NPS delta across the period an AI agent is deployed. If NPS holds or climbs, the AI is helping the relationship. If it drops, something subtler is going on than the resolution metric suggests.