MIRAGE: A Polarity-Flipping Encoding Subspace in LLM Agents

In three linesResearchers identify a shared low-dimensional encoding subspace in LLM residual streams that detects when agents covertly encode sensitive data (Base64, ROT13, etc.). MIRAGE, a real-time monitor leveraging two mechanistic signals, achieves AUC=0.918 on 126 exfiltration scenarios, substantially outperforming output-only detection (AUC=0.518).

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