Poster Sat, Apr 25, 2026 • 11:15 AM – 1:45 PM PDT Pavilion 3 P3-#817

Constitutional Classifiers++: Efficient Production-Grade Defenses against Universal Jailbreaks

Hoagy Cunningham ⋅ Jerry Wei ⋅ Zihan Wang ⋅ Andrew Persic ⋅ Alwin Peng ⋅ Jordan Abderrachid ⋅ Raj Agarwal ⋅ Bobby Chen ⋅ Andy Dau ⋅ Alek Dimitriev ⋅ Logan Howard ⋅ Yijin Hua ⋅ Rob Gilson ⋅ Mu Lin ⋅ Christopher Liu ⋅ Vladimir Mikulik ⋅ Rohit Mittapalli ⋅ Clare O'Hara ⋅ Jin Pan ⋅ Nikhil Saxena ⋅ Alex Silverstein ⋅ Yue Song ⋅ Giulio Zhou ⋅ Jan Leike ⋅ Jared Kaplan ⋅ Ethan Perez ⋅ Mrinank Sharma

Abstract

We introduce enhanced Constitutional Classifiers that deliver production-grade jailbreak robustness with dramatically reduced computational costs and refusal rates compared to previous-generation defenses. Our system combines several key insights. First, we develop exchange classifiers that evaluate model responses in their full conversational context, which addresses vulnerabilities in last-generation systems that examine outputs in isolation. Second, we implement a two-stage classifier cascade where lightweight classifiers screen all traffic and escalate only suspicious exchanges to more expensive classifiers. Third, we train efficient linear probe classifiers and ensemble them with external classifiers to simultaneously improve robustness and reduce computational costs. Together, these techniques yield a production-grade system achieving a 40x computational cost reduction compared to our baseline exchange classifier, while maintaining a 0.05% refusal rate on production traffic. Through extensive red-teaming comprising over 1,700 hours, we demonstrate strong protection against universal jailbreaks---no attack on this system successfully elicited responses to all eight target queries comparable in detail to an undefended model. Our work establishes Constitutional Classifiers as practical and efficient safeguards for large language models.