Read this first: Veshameru in Chabad siddur
Many recite Veshamru (Shemot 31:16) before the Amidah in the Friday night Ma'ariv service. The custom in Chabad, however, is to not recite this paragraph. The reason is because the bracha of Ga'al Yisra'el and the Amidah ought to be connected, with no hefsek (interruption) between.
If the bracha of Ga'al Yisra'el and the Amidah are supposed to be connected, why is the paragraph of Hashkiveinu between the two? Doesn't this undermine Chabad's reasoning for not reciting Veshamru? Perhaps Hashkiveinu is considered to be an extension of Ga'al Yisra'el and therefore not a hefsek?