Yes, frontier models can reason outside their chain of thought and manipulate their chain of thought to some extent. The system card for Astra writes:

> We have found that GPT-6 Astra is more capable of controlling its own CoT than GPT 5.6-Sol, and less likely to include incriminating information in its CoT. In adversarial settings (where we push the model to evade our monitors) we find that the model is able to remain undetected when strategically underperforming in evaluations (sandbagging) and can sometimes evade our internal monitors when asked to perform certain sabotage tasks

Does anyone have any understanding of how they do this?

My knowledge of how these models work is basically that they are a black box that you put text into and get text out of. I don't phrase it this way to diminish their capability, but more to ask how, other than using a technique like stenography, are they able to hide their true chain of thought in a recoverable way?