Reply To: Who wrote the Shulchan Aruch

There’s an edition of the Mishna Brura with a commentary by Rabbi Avrohom Noach Klein that notes every halachic difference between the psak din of the Chabad Shulchan Aruch and the Mishna Brura. Before the M’B was published, Polish chasidim used Shulchan Aruch Harav as their primary source of psak halocho. Thoday almost everybody but Chabad uses the Mishna Brura. Many of the differences are purely chasidic in nature. Basically the Baal HaTanya wanted to make a chasidic kitzur.