Why aren’t coffee beans kitniyot?
Coffee beans are indeed kitniyot! They are seeds that are eaten and planted like any other bean (including soybeans or sunflower seeds). The Chacham Tzvi and the Yabetz said that coffee beans are definitely kitniyot, but no one says that they are forbidden on Pesah as everyone knows that when the minhag of kitniyot was adopted in the land of Ashkenaz hundreds of years ago, coffee was unknown and therefore not included under the purview of the minhag. In addition, everyone knew that anything else came along was not to be added to the list of kitniyot. Rav Bar-Hayim relates that Rav Shaul Yisraeli zt”l of Yeshivat Merkaz HaRav told him that he held this same reasoning for permitting the consumption of soybeans during Pesah.