The logic behind Nusach Sefard is mystical, and it was stated openly by the movement that adopted it. Lurianic kabbalah taught that the prayers of Israel ascend through heavenly gates, one for each of the twelve tribes, each with its own rite, and that the Sephardic wording used by Isaac Luria himself corresponded to a thirteenth gate through which any prayer may pass.
For the Hasidim of eighteenth-century Podolia and Volhynia, heirs of the Baal Shem Tov's revival with its intense devotional life, adopting the Ari's nusach meant praying through the gate that was open to all Israel, and prayer books began to appear that grafted Lurianic and Sephardic usages onto the Ashkenazi service their communities had always known. The graft shows: Nusach Sefard keeps the Ashkenazi corpus and much of its order while adjusting wordings toward the Sephardic text, moving certain passages, and admitting Lurianic additions such as the recitation of Hodu before Baruch She'amar and the Kabbalistic preambles to the commandments.
The opponents of Hasidism, the Mitnagdim, attacked the change as a desecration of ancestral custom, and the rabbinic literature of the era is full of the dispute; the Hasidic answer, that devotion outranks habit, was itself a manifesto. Chabad under Shneur Zalman of Liadi produced the most carefully edited version, published as the Siddur ha-Rav and known as Nusach Ari, still the exclusive rite of that movement.