An agreement in principle is not an agreement
Reuters reported that Russian and Ukrainian negotiators reached an agreement in principle on a prisoner exchange after talks in Abu Dhabi. That is the whole of the confirmed claim, and it is narrower than a completed swap. US mediators, who took part in the session, said major disagreements remained — and those disagreements were not resolved by the meeting. No date for an exchange appeared in the reporting we are working from, and no verified list of names has been published by either side.
An agreement in principle fixes intent, not logistics. Until a date and a location are attached to it and both delegations confirm the same roster, nothing has moved except the fact that the two sides sat in one room.