When Does One Make a Leisheiv B'Sukkah?

The Rambam in Hilchos Succah 6:12 writes (in the name of his Rabbis as well as l'halacha) that on the first night of Succos one should make Kiddush standing up so that he can sit down after he makes the bracha of leishev b'succah (thus fulfilling the inyan of making the bracha before the mitzvah). [Derech Agav - Many are medayek from here that the rest of the year the Rambam would hold to sit during kiddush.] The Rosh in Succah 4:3 asks, the mitzvah of "sitting" in the Succah doesn't really mean sitting literally?! It just means to live in the succah. So if you truly want to make the bracha before the mitzvah - why not make it before you enter the succah?

The Taz in O.C. 643:2 anwers that just walking into a succah isn't recognizably a mitzvah of dwelling in the succah, because you may just walk right back out. Chazal were only mesaken a bracha for recognizably dwelling in the succah.

R' Hershel Schachter in Eretz HaTzvi Siman 3 writes as follows:

Chachamim weren't meseken a birchas hamitzvah for a kiyum hamitzvah, but only for doing a maaseh mitzvah. Granted that one who enters a succah and is standing there has been mekayem a mitzvah by entering of yeshivas succah, however on a kiyum like this there is no takkana for a bracha.

And even though entering and walking into the succah is certainly a maaseh gamur, nevertheless the Rabbis of the Rambam hold that it is not a maaseh mitzvah mesuyam until you sit mamash in the succah.

Basically R' Schachter is being mechalek between a maaseh mitzvah and a kiyum mitzvah. One only makes a bracha on a maaseh mitzvah and not a kiyum. R' Schachter points out in the footnote that not everyone agrees to this principle. For example, if someone puts a mezuzah up in someone else's house - who makes the bracha? The guy who puts it up is doing the maaseh mitzvah. The owner of the house has the kiyum. It's actually a machlokes who makes the bracha. Here R' Schachter is following the opinions that it's the one who does the maaseh mitzvah that makes the bracha.

Regardless, R' Schachter himself points out the downside of this approach. Isn't walking into the succah a maaseh? So we haven't really answered the question. Why make the bracha specifically before sitting down? So R' Schachter circles back and says that although entering is a maaseh it's not a maaseh mesuyem (a structured and defined maaseh).

We posted earlier on a similar issue. Why not make a bracha on sleeping in the succah? In that post we quoted from Reshimos Shiurim on Succah that R' Soloveitchik asks, is sleeping a kum v'aseh or a shev v'al taaseh? He seems to conclude it is shev v'al taaseh. Meaning, in halacha "going"to sleep isn't considered active, but passive. Thus, we suggested that it is not a maaseh and there is no bracha. If so, perhaps the same is true by merely entering the succah. Just "being" in the succah isn't an action. It isn't a maaseh mitzvah - even if it is a mitzvah. Perhaps that is also what R' Schachter means when he says it isn't a maaseh mesuyem.