This article examines the relationship between semantic and syntactic evolution in the development of three Spanish verbal constructions: verbal periphrases, pseudo-coordinative constructions (e.g., va y dice), and auxiliary chains. While theories of grammaticalization and diachronic construction grammar generally predict a parallel decrease in semantic compositionality and syntactic analyzability, the behavior of these constructions suggests a more complex scenario. We argue that semantic compositionality and syntactic analyzability do not always evolve in tandem. Instead, the constructionalization of grammatical patterns may preserve aspects of internal syntax even when constituents undergo functional recategorization. Drawing on previous analyses and a corpus-based examination of Spanish complex predicates, we show that verbal periphrases, pseudo-coordinative constructions, and auxiliary chains maintain analyzable internal structure despite diachronic reduction of compositional meaning. We propose that (complete) loss of analyzability tends to occur only at advanced stages of grammatical change. The study contributes to current debates on the nature of grammaticalization/constructionalization, internal syntax, and the cognitive status of auxiliary constructions, offering a broader perspective on mechanisms of language change.