Perplexity-based filtering. Perplexity- based filtering has been suggested in many contexts as a defense against adversarial text input LLM-based filtering. A possible defense is to employ an oracle LLM to determine if the query is natural or not. An active alternative is to paraphrase queries using an oracle LLM. Detecting anomalous user workloads. Another possible defense requires the router to monitor individual user work- loads, and identify those users whose queries are routed to the strongest model with an abnormally high frequenc