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

Published: January 8, 2026 | arXiv ID: 2601.04603v1

By: Hoagy Cunningham , Jerry Wei , Zihan Wang and more

BigTech Affiliations: Anthropic

Potential Business Impact:

Makes AI safer and cheaper to run.

Business Areas:
Corrections Facilities Privacy and Security

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.

Country of Origin
🇺🇸 United States

Page Count
17 pages

Category
Computer Science:
Cryptography and Security