Siman 133
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א בְּשַׁבָּת וְיוֹם טוֹב אֵין אוֹמְרִים בָּרְכוּ אַחַר קַדִּישׁ בַּתְרָא. הַגָּה: אֲפִלּוּ בְּמָקוֹם שֶׁנָּהֲגוּ לְאָמְרוֹ בִּימוֹת הַחֹל, שֶׁמָּא לֹא הָיוּ יְחִידִים בְּבֵית הַכְּנֶסֶת כְּשֶׁאָמְרוּ בָּרְכוּ, מִכָּל מָקוֹם בְּשַׁבָּת וְיוֹם טוֹב אֵין לְאָמְרוֹ, דְּהַכֹּל בָּאִין לְבֵית הַכְּנֶסֶת קֹדֶם בָּרְכוּ (בֵּית יוֹסֵף בְּשֵׁם רִיבַ"שׁ).
1 The Laws of Bar'khu on Shabbat. Containing 1 Se'if: On Shabbat and Yom Tov we don't say Bar'khu after the last Kaddish. Rema: Even in a place where they say it on ordinary days [because] perhaps there were individuals who were not in the synagogue when they said [the initial] Bar'khu; nevertheless, on Shabbos and Yom Tov we don't say it because everybody comes to synagogue before Bar'khu. [Beit Yosef in the name of the Rivash]