The Imams know all the knowledge that has come to the angels, the prophets and the Messenger

"Indeed, Allah, Blessed and Exalted, has two kinds of knowledge: One kind He has made apparent to His angels, His prophets, and His messengers. Whatever He has made apparent to His angels, His prophets, and His messengers, we have learned it. And another kind He has kept exclusively to Himself. So, whenever Allah decides to reveal something from it, He informs us of it, and it is presented to the Imams who came before us."
From Ali ibn Muhammad and Muhammad ibn al-Hasan, from Sahl ibn Ziyad, from Musa ibn al-Qasim, and Muhammad ibn Yahya, from al-Amraki ibn Ali, all from Ali ibn Ja‘far, from his brother Musa ibn Ja‘far (AS), a similar narration.

“Allah, the Most Holy, the Most High, has two kinds of knowledge. One kind is His only and no creature knows about it. The other kind is that which He has thrown unto His angels and His Messenger. Whatever is thrown to the angels and the Messengers have reached us.”

he heard abu Ja‘far (a.s.) say the following. “Allah, the Most Holy, the Most High, has two kinds of knowledge. One kind is that which is granted and the kind is that which I withheld. Of the one which, is granted, nothing is known to the angels and the Messengers, but only we know it. The one which is withheld iis the kind that is before Allah, the Most Holy, the Most High in the original Book. When it appears it permeates.” come of Allah said:

“Allah, the Most Holy, the Most High, has two kinds of knowledge. One kind of knowledge is that which no one knows except He. The other kind is that which He has taught to the His angels and His messengers. Whatever His angels and Messengers have learned we know it.”