Lighting Shabbat Candles and Automatic Acceptance of Shabbat

Does Lighting the Shabbat Candles cause an Automatic Acceptance of Shabbat?

In OC 263:10, the Shulchan Aruch writes:

According to the [sefer] Halachot Gedolot, once the Shabbat candles are lit, one has accepted Shabbat and all further melacha is forbidden…and some disagree with the Halachot Gedolot and say that the acceptance of Shabbat is not related to the lighting of the candles but to the recitation of ma’ariv. Once the chazzan has said “barchu” everyone must cease melacha. According to our practice, reciting “Mizmor Shir L’yom Hashabbat” is the equivalent of “barchu.”

As a general rule in the study of Shulchan Aruch, when there is a list of rulings that begin with “And some disagree…” or “And some say…” it is the last ruling that the Shulchan Aruch accepts.

According to this, one does not automatically accept Shabbat with the lighting of the Shabbat candles.

On the other hand, in OC 679:1, the Shulchan Aruch writes, “On Erev Shabbat one lights the Chanuka candles first and then the Shabbat candles.”

In his work, the Beit Yosef, the author of the Shulchan Aruch, explains why this is so: “…because if one lights the Shabbat candles first, one has accepted Shabbat [and would no longer be permitted to light the Chanuka candles].”

This seems to imply that one indeed automatically accepts Shabbat with the lighting of the Shabbat candles.

How do we reconcile this contradiction?

Among the answers given is that it is simply best to conform to the opinion of the Halachot Gedolot whenever possible, though in extenuating circumstances, one need not accept Shabbat with the lighting of the Shabbat candles. See the Beit Yosef, OC 679, for more.