Allow me to open my question by citing an example from recent history:
If you recall in Sept 2021 it was revealed by Axios that during the chaos of the 2020 election/post-election General Mark Milley had personally called General Li Zuocheng to ensure him that there was no 'surprise strike' coming from the US towards China, as there were rumors of such a strike circling its way through Chinese Intelligence.
This became a large controversy for General Milley, who had to testify to the before the Senate; but that is not of relevant concern to this question. The point is that outside of standard media, the State Department, even the Department of Defense, there exist these channels of communication between military leaders and commanders. Likewise I would assume such secret independent channels to exist between intelligence officers, and even state officials who operate largely independent of the domestic political concerns. There are countless examples like the Milley/Li relationship throughout history; this was just the most recent example.
Is there any evidence to suggest the existence of such relationships between Russia and the US or rather NATO at large? Is there some level of assurance both can give to each other that they are not willing to enter complete Nuclear War? Do Putin's Generals and NATO Generals talk to each other as foes who understand the need to set boundaries...especially in a situation like this, or are they giving each other the silent treatment?
I understand my question asking about things that would by nature be confidential. But I would appreciate any reference to potential relationships, or specific individuals operating at a high level who have personal histories, or even if such an architecture of communication can possibly exist between with states like Russia the US.