If I arrive late to a shabbos meal, do I need Lechem Mishneh, or can I rely on the others?

Question

If I arrive late to a shabbos meal, and the others at the meal have already made Hamotzi on Lechem Mishneh, when I join them and wash for bread, do I need Lechem Mishneh of my own as well? Or can I rely on their Lechem Mishneh, and make Hamotzi on a slice of challah alone?

It seems to me that this should be okay, because, at a regular meal, when the Ba'al Habayis makes Hamotzi on Lechem Mishneh, the others there eat just the slice handed to them - in other words it seems they rely on his Lechem Mishneh. The difference is, that I join the meal later. So, can I rely on his Lechem Mishneh too?

This question is not whether I should (obviously I should make Hamotzi on Lechem Mishneh when I have the chance), but whether I must (for instance if I'm trying to save more challahs for the next meal of shabbos.)

Answer 1

Everything that follows is dependent on the situation you find yourself in. If you arrive late but there are two whole loaves (loaf is defined as one complete bread, a pita, a roti, a challah, etc) then this is the ideal and you must use those.

If you come to a dinner and the bread has already been broken then you can rely on the following. You must make hammotzi on two pieces of bread that are intact from the moment you happen upon them if there are two pieces when you arrive. So if two challot have had some slices taken off of them by the time you arrive, but you didn't slice anything off of them, then you can use those two challot for hammotzi. You may even use two slices of bread as long as they were sliced by someone else before you arrived. You may also make hammotzi on one piece of bread if it's the only bread left when you arrive.

A deficiency in the completeness of the loaf of more than 1/48 will disqualify the loaf for use as lechem mishna. In the event that one does not have two complete loaves then even any two pieces of bread will suffice in an emergency.[7] In fact, it is said that Rav Itchele of Volozhin would provide guests who arrived late to his Shabbat meal with two slices of bread to use a lechem mishna. It is explained that since the latecomer was not present when the original loaf was sliced, the two slices he is now presented with can be deemed as "whole" for the purpose of lechem mishna.[8] So too, one who only has one whole loaf, may combine a matza, a piece of cake which is whole (i.e. a rugelach)[9] or even a frozen loaf from the freezer in order to meet the lechem mishna requirement.[10] In an emergency, a broken loaf may be used for lechem mishna if it can be reattached by means of a toothpick or the like, in order that it at least appears to be whole.[11]

Source: https://outorah.org/p/36245/#_ftn7