# Capability-Routed Guard: Defending Large Reasoning Models Against Reasoning-Centric Jailbreaks

arXiv: https://arxiv.org/abs/2608.07892 · HTML: https://mlsanity.com/paper/2608.07892/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Placed in Safety alignment, refusal and guardrails, one of 12 directions in LLM safety and security.
- Builds on 11 of its 16 references that are in the map.
- First posted on arXiv 8 Aug 2026.

## Placed in

- LLM safety and security / [Safety alignment, refusal and guardrails](https://mlsanity.com/safety/safety-alignment-refusal-and-guardrails/)

## Builds on (most cited first, 11 of 11)

- [Llama Guard: LLM-based Input-Output Safeguard for Human-AI Conversations](https://mlsanity.com/paper/2312.06674/) (2023)
- [DeepInception: Hypnotize Large Language Model to Be Jailbreaker](https://mlsanity.com/paper/2311.03191/) (2023)
- [A Wolf in Sheep's Clothing: Generalized Nested Jailbreak Prompts can Fool Large Language Models Easily](https://mlsanity.com/paper/2311.08268/) (2023)
- [Defending Large Language Models Against Jailbreaking Attacks Through Goal Prioritization](https://mlsanity.com/paper/2311.09096/) (2023)
- [Self-Guard: Empower the LLM to Safeguard Itself](https://mlsanity.com/paper/2310.15851/) (2023)
- [A Mousetrap: Fooling Large Reasoning Models for Jailbreak with Chain of Iterative Chaos](https://mlsanity.com/paper/2502.15806/) (2025)
- [Jailbreaking Large Language Models Against Moderation Guardrails via Cipher Characters](https://mlsanity.com/paper/2405.20413/) (2024)
- [PARDEN, Can You Repeat That? Defending against Jailbreaks via Repetition](https://mlsanity.com/paper/2405.07932/) (2024)
- [SecurityLingua: Efficient Defense of LLM Jailbreak Attacks via Security-Aware Prompt Compression](https://mlsanity.com/paper/2506.12707/) (2025)
- [ReasoningGuard: Safeguarding Large Reasoning Models with Inference-time Safety Aha Moments](https://mlsanity.com/paper/2508.04204/) (2025)
- [IntentionReasoner: Facilitating Adaptive LLM Safeguards through Intent Reasoning and Selective Query Refinement](https://mlsanity.com/paper/2508.20151/) (2025)

## Abstract (arXiv)

Large reasoning models (LRMs) expose a new safety failure mode: adversarial prompts can manipulate reasoning context, task decomposition, or capability interpretation so that harmful objectives are processed as legitimate reasoning steps. Existing safeguards, including safety reminders, external classifiers, and self-checking wrappers, are often brittle because they either inspect the adversarial prompt directly or ask the target model to perform additional safety reasoning on the same surface that attacks exploit. We introduce Capability-Routed Guard (CRG), a model-agnostic inference-time guardrail for closed-source LRMs, where defenders cannot inspect hidden reasoning traces or modify model weights. CRG reframes prompt defense as a capability-routing problem: a side-channel controller first constructs a trusted representation of the user's authorized task, active context, safety evidence, and capability-transfer risk, separating executable intent from untrusted reasoning context. This representation supports route-specific execution, allowing CRG to block high-risk requests, constrain ambiguous ones, and forward low-risk requests through trusted active context. Finally, CRG applies TraceCheck to verify consistency with the authorized task and invokes a restricted fallback to preserve utility for low-risk benign prompts. Extensive experiments demonstrate that CRG effectively mitigates diverse reasoning-centric jailbreaks while preserving benign utility and avoiding common over-refusal issues. Further analysis shows that its components contribute complementary benefits, highlighting the importance of coordinated defense mechanisms for securing large reasoning models.