The Gemara establishes the core principle 'ein kiddush ela bemakom seudah' — Kiddush is only valid where the meal is eaten. One who recites Kiddush in one place and eats in another has not fulfilled their obligation.
וְאַזְדָּא שְׁמוּאֵל לְטַעְמֵיהּ, דְּאָמַר שְׁמוּאֵל: אֵין קִידּוּשׁ אֶלָּא בִּמְקוֹם סְעוּדָה. סְבוּר מִינַּהּ: הָנֵי מִילֵּי מִבַּיִת לְבַיִת, אֲבָל מִמָּקוֹם לְמָקוֹם בְּחַד בֵּיתָא — לָא. אֲמַר לְהוּ רַב עָנָן בַּר תַּחְלִיפָא: זִימְנִין סַגִּיאִין הֲוָה קָאֵימְנָא קַמֵּיהּ דִּשְׁמוּאֵל, וְנָחֵית מֵאִיגָּרָא לְאַרְעָא וַהֲדַר מְקַדֵּשׁ. וְאַף רַב הוּנָא סָבַר אֵין קִידּוּשׁ אֶלָּא בִּמְקוֹם סְעוּדָה. דְּרַב הוּנָא קַדֵּישׁ, וְאִיתְעֲקַרָא לֵיהּ שְׁרָגָא, וְעַיַּילִי לֵיהּ לְמָנֵיהּ לְבֵי גְנָנֵיהּ דְּרַבָּה בְּרֵיהּ דַּהֲוָה שְׁרָגָא וְקַדֵּישׁ וּטְעֵים מִידֵּי, אַלְמָא קָסָבַר: אֵין קִידּוּשׁ אֶלָּא בִּמְקוֹם סְעוּדָה.
And Shmuel follows his line of reasoning, as Shmuel said: There is no valid kiddush except in the place of one’s Shabbat meal. If one does not eat a meal in the location in which he recites kiddush, he has not fulfilled the mitzva of kiddush. The students understood from this statement that this halakha applies only when one goes from house to house and eats the Shabbat meal in a different house from the one in which he recited kiddush. But if one went from the place where he recited kiddush to another place in one house, no, there is no problem, and he has fulfilled the mitzva of kiddush. However, Rav Anan bar Taḥalifa said to the students: Many times I stood before Shmuel, and he descended from the roof to the ground floor and recited kiddush again. This indicates that Shmuel maintains that even if one recites kiddush and eats the Shabbat meal in a different part of the same house, he must recite kiddush a second time. With regard to this halakha, the Gemara notes: And Rav Huna also maintains that there is no kiddush except in the place of one’s Shabbat meal. The proof of this is that Rav Huna once recited kiddush and his lamp was extinguished. And as it was difficult to eat in the dark, he brought his belongings to the wedding home of his son Rabba, where there was a lamp, and he recited kiddush there and tasted some food. Apparently, Rav Huna maintains that there is no kiddush except in the place of one’s Shabbat meal.