Sponsors see the agreed priorities and the progress reviews. Where the engagement is sponsored, it opens with an alignment session between leader, sponsor and coach, and closes with a review against the priorities that session set.
Session content stays between coach and leader. That line is stated at contracting and never varies, because it is what lets the leader work on the real version of the problem rather than the managed one. When coaching turns into reporting, the leader starts managing the coach, and the work stops being real.
Where stakeholder input is gathered, it reports as patterns, non-attributable. The evidence shows whether the behaviour changed, and nothing of what was said in the room.