Yes, I'm eliding Godelian arguments there... Consequences of anyone being rational and believing X have been removed.

Interestingly, in the model I produced down below, both the countess and the baron produce correct models of each other. Furthermore, the countess knows she produces a correct model of the baron (as she runs his source successfuly).

It also happens that the baron can check he has the correct model of the countess, after making his decision, by running her code. Since the countess will stop running his own code as soon as she also knows his outcome, he can know that his model was accurate in finite time.