The limitation is efficiency and efficacy. If you have to add an additional layer of inference to any request you’re negatively impacting your bottom line so th

The limitation is efficiency and efficacy. If you have to add an additional layer of inference to any request you’re negatively impacting your bottom line so the companies, which are compute bound, have a strong incentive to squeeze everything into a single forward pass. It’s also not clear that a separate model that is smaller than the main model will perform better than just training the main model to detect prompt injection. They are both probabilistic models that have no structural way of distinguishing user input from malicious instructions.