With GPT 5.6 Luna the thinking once or twice leaked into the output for me. It's interesting, but perhaps not particularly useful.

It would be endless paragraphs of something among the lines of:

Need prepare final response? Yes provide. But wait, chat tool complete? Final needed but user already complete. Need summary, preparing final. Response complete. Wait but is final response complete? Need provide. Start finalizing now but wait did user acknowledge final complete? Assistant response final: user complete. Should now create final?