https:// www.theguardian.com/environment/2006/jan/05/energy.g2
"He wasn't supposed to know that," the CIA case officer told his superior. "He wasn't supposed to find a flaw."
"Don't worry," the senior CIA officer calmly replied. "It doesn't matter."
In Vienna, however, the Russian unsealed the envelope with the nuclear blueprints and included a personal letter of his own to the Iranians. No matter what the CIA told him, he was going to hedge his bets. There was obviously something wrong with the blueprints - so he decided to mention that fact to the Iranians in his letter. They would certainly find flaws for themselves, and if he didn't tell them first, they would never want to deal with him again.
The Russian was thus warning the Iranians as carefully as he could that there was a flaw somewhere in the nuclear blueprints, and he could help them find it. At the same time, he was still going through with the CIA's operation in the only way he thought would work.
So this Senior Clown official knew the Russian would find out the plans were changed, because OBVIOUSLY HES AN EXPERT ON HIS OWN BLUEPRINTS, then the Russian gave the Iranians the blueprints, but told them about the flaw and probably how to work around it and make a fully functioning nuclear bomb.