For me, one thing is certain: Stalin could rightly not trust the so-called "intelligence warnings".
Because too many were reported inconsistent warnings. Only for May intelligence was called 12-16 dates of the German attack.
What kind of leader does not lose confidence in such "signals" ... at the level of fortune telling on the coffee grounds?
On December 18, 1940, Hitler signed directive No. 21 (Operation Barbarossa) on preparations for war against the Soviet Union, beginning with the indication:
"... The German armed forces must be ready to break Soviet Russia in a short-term campaign even before the war against England is ended."

The document went "on execution" for the headquarters of the branches of service, for diplomats, business executives, etc. The circle of persons involved in execution was very large. It was further expanded when the Barbarossa plan was reported to the German allies.
This happened in April 1941. But not from Italy, nor from Japan, information about the directive also did not leak. More precisely. such have not become known to Soviet intelligence.
Even the name of the German directive in the USSR was learned only in the middle of the war, from the captives of German generals.
Too good The Third Reich kept its secrets and conducted disinformation measures covering the main operation.
There were no Soviet intelligence agencies in the higher echelons and among the highest officers of Germany. And the Allies had no such "exits" either.