Q. To be considered a seudas mitzvah, does the bar mitzvah bochur have to be there? (On the bo bayom he had to go to shiur, but he was there at the beginning)

A. Horav Shlomo Miller’s Shlit’a opinion is that the bar mitzvah bochur does not have to be present, since it is the mitzvah of the father to do the seudah. (Mogen Avrohom O.H. 225: 4 quoting Yalkut Chodosh, Yam Shel Shlomo – Baba Kama 37, Bereshis Rabah 53, Chinuch Yisroel 13: 10)

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a