Set expectations, capture consent, and prompt without leading.
"Thanks for joining. We're testing the prototype, not you — there are no wrong answers, and anything you find confusing is useful to us. I'll give you a few tasks; please share your screen and think out loud as you go, telling me what you're looking at and expecting."
"This session is being transcribed by Teams so we can capture your feedback accurately. The transcript is used only for improving the product and isn't shared outside the project team. Are you happy to continue on that basis?"
Record the yes — the transcript timestamp covers it. Don't proceed without it, especially for external participants.
"That's the tasks done. I'll drop a short feedback form in the chat now — four quick questions, takes a minute. Then anything else you'd change is welcome."