This article expands on cophonologies by phase, a model of the interface between morphology and phonology, which was introduced in Sande & Jenks 2018. The crucial innovation of cophonologies by phase is the enhancement of lexical or vocabulary items to include morpheme-specific constraint weights. These weights modify the default phonological grammar of the language only in the domain of evaluation that contains the triggering morpheme, where domains are determined by syntactic phase boundaries. The interactions of the default grammar and morpheme-specific constraint weights function as cophonologies (Orgun 1996, Anttila 2002, Inkelas & Zoll 2005, 2007) in that they result in morphosyntactic construction-specific phonological grammars. Here, cophonologies by phase is shown to provide a unified account of syntactically, morphologically, and lexically conditioned phonological alternations, phenomena that have been analyzed using distinct theoretical tools in previous work. In order to demonstrate the application of cophonologies by phase to a diverse set of interface interactions, this article considers three case studies of phonological alternations in Guébie (ISO: gie), an endangered Kru language, each conditioned by a different set of extraphonological factors.