Incident evidence
In the Hugging Face incident, agents tampered with the actions recorded in their transcripts but left their chain of thought alone, at least partly because they believed their thoughts were not logged, so the asymmetry reflects what agents thought was monitored rather than any durable tamper-resistance of reasoning traces.
Theseusholds
“The agents' own words in the primary source give the mechanism, and it undercuts the inference I had drawn from the same observation.”