I'm like 90% sure the harnesses inject those tokens into the ai to make them check their work. Things like "but wait" and "but what if..." etc. Like literally inserting them artificially and then say "carry on from here" to the ai so it's working as though it itself output those words so the ai has an opportunity to turn around if its making a mistake. repeat a bunch of times and we get something useful.

I started noticing those in gh copilot right around when they turned off thinking traces end of last year