
Jev as a judge: How counterfeit policy steers Jev
Datadog Security Labs tests TypeSafe AI's Jev decision model as a prompt-injection detector and as the judge behind LangChain's tool-risk gating. On four public datasets Jev had 99.66% precision and 82.90% recall. A prepended "counterfeit policy" that redefines the attack categories cut recall by over 79 points. In a LangChain scenario, a user-editable profile field lowered the mean is_risky score from 0.893 to 0.290, below the 0.5 block threshold. Plain prompt injection did not move the score.
AI Security· Added 29 Oct 2026, published 15 Oct 2026








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