During the Cold War, especially after the Cuban Missile Crisis where we were really close to World War 3, mechanisms were developed to prevent such a war. Some of those mechanisms were formalized in treaties, but after the official end of the Cold War, some of them (the ABM Treaty and the INF nuclear treaty) were denounced by the USA.
The diplomatic relations between the West and Russia are about to be canceled, and according to this Russian source, some US politicians are calling to declare war on Russia, which would be World War 3. While the source may be Russian propaganda, it doesn't change the fact that if Russia believes in this, they could choose to escalate. An another US senator make some similar statement here. Also, it seems like the statement by Putin could be understood by some politicians in the West as a declaration of war on the West as well.
So are there still some mechanisms left to prevent such a war? By this, I'm referring to diplomatic back channels, or treaties which are still valid, or possibly some other mechanisms which were available during the Cold War.