agada stories legends - Is the leviathan kosher?

The leviathan seems to be a unique sea creature, which I've always pictured as some sort of sea serpent. This is consistent with Yeshayahu 27:1's description of it as a snake (nachash). An answer to this question suggests that it's a fish (and doesn't address Yeshayahu). We know from the midrash that at the end of days the righteous will feed on it, whatever it is.

One could argue that because the righteous will feed on it, it must be a kosher fish. Or if the leviathan is a serpent, one could argue that when God holds this end-of-days banquet He can declare anything He wants to be permitted, culinarily speaking -- the laws of kashrut as we know them don't apply. (I've no idea if such an argument would be, err, kosher.)

Do any sources say if the leviathan is kosher by the laws of the torah?

Answer

The medrash tanchuma on parshas Shmini #7 takes the opinion that at that great feast of Beheimos and Leviason, the mitzvos which until now were only to purify/smelt the people with will no longer apply. The proof is that the Beheimos will not have a proper slaughtering, but will rather be killed by the Liviason. The medrash goes on to prove that Liviason is an abnormal strong creature, capable of killing Beheimos.

But throughout the entire discussion of proving that slaughtering will become obsolete, the medrash does not entertain the idea that Beheimos or Liviason are not kosher.

The Vayikra Rabba in chapter 22 states explicitly that it is kosher.

The Bavli in Chulin 67b says it is a kosher fish. The Maharsha asks would Hashem ever feed his Tzadikim nonkosher fish? He answers that the gemara is clarifying that Liviason is in fact a fish and not some other creature like a bird. The Iyun Yaakov answers this question by pointing to Yalkut on Shmini 535 and on Tehilim siman 146, that in fact in the future Hashem will allow what was not allowed beforehand and a New Torah will be given from Tzion. The Aruch ערך גא says the gemara needed to tell us it was kosher because it is mentioned along with a snake, so as to preclude the assumption that it is not kosher like a snake, we have the drasha in the gemara.