Actually, how does chain of thought work? Is the LLM actually creating the tokens and then re-reading them, or is the there still a full hidden state under the hood and then the UI just prints that projection?
Closed models probably do the same thing internally. What is shown externally is different though: you get a summary of the chain of thought, not the thoughts itself. This is done to prevent distillation.
The latest look we had at a frontier chain of thought is probably in the Huggingface incident report - I haven't actually read it yet but I saw the BlackHat talk, and it included some snippets. The thoughts look like they are approaching neuralese. The words are still understandable but the grammar is weird, simplified. In comparison, Qwen 3.8 27b thinks in valid English.