Be warned that the Jev "jaggedness" documentation specifically notes adversarial content as something Jev is very susceptible to: https://docs.typesafe.ai/model-jaggedness/jev-1.13#adversari... - so using Jev itself as part of a prompt injection guard is risky.

Anthropic, OpenAI, and Muse all use regular LLM calls to protect against prompt injection now and seem to have evals that give them confidence in doing that, so at least they think their own models are up to the task.