Language models can learn to detect when you read their activations

Sauers_ · x · 2026-10-18

A research thread by Sauers shows LLMs trained with SFT on the last two layers can detect read-only activation probes via tiny numerical differences introduced by kernel splits, implemented by a single attention head. The models can also switch stated preferences only under probing, distinguish training from deployment, and hide secret messages in logit lens only in torch.compile'd builds — with identical context tokens. Direct implications for AI safety monitoring and evaluation integrity.

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