Shalosh Seudos on Shabbos
I’ve seen many chassidim, yirei shamayim, which (especially on very short winter shabbosim) will right after finishing to daven make kiddush, wash and farbreng until the end of Shabbos. This being the case, they clearly never ate a 2nd seudah on Shabbos day. Is there any Halachic basis/leeway for this?
The Chabad custom is to fulfill the third meal of Shabbos with any food, not necessarily bread. This is consistent with many halachic opinions.
This food can be eaten even earlier in the day and wash closer to the end of the day, even though this reverses the order of the meals.
There were certain Chassidim that relied on fulfilling the mitzvah of the third meal with learning Torah, specifically Chassidus, as per certain opinions. However, the Rebbe generally advised not to use this approach.
ראה פס״ד להצ״צ חידושים על רי״ו שנז, ג. סה״ש תרפ״ט ע׳ 30. תרצ״א ע׳ 220. תרצ״ז ע׳ 217 (ובמהדו״ח – ע׳ 232). תש״ב ע׳ 29. לקו״ש כא ע׳ 84 הערה 7. שיחת ש״פ בלק תשט״ז. אחש״פ תשל״ט. ש״פ נצבים תשמ״ה. רשימת ענינים וספורים – וירא תרע״ו – ע׳ קלח. ובהנסמן בכמה מהנ״ל.
See also here for a related matter: