[Avodah] What is the source for the minhag of Chasidim to have hakafos on Shmini Atzeres night?

[Chaim G Steinmetz]

Though the kneejerk reaction by some apparantly is that the "minhog
Chassidim" is based on a "mistaken reading" (therefore implying that the
minhog "vosikin" mentioned in Siddur of the Baal hatanya is also a
mistake!), the idea of hakofos on SA night (and day!) outside EY is
CLEARLY found in the sefer Chemdas Hayomim (without getting into the
discussion of the authorship of this sefer). Therefore, the concept
predates the "mistake" of Chassidim...
Chaim Gershon Steinmetz
cgsteinmetz at juno.com