Most western Iranian languages, despite their broad differences, show a common quality when it comes to the verbal agreement of past transitive verbs. Dabir-moghaddam (2013) and Haig (2008) discuss it as a grammaticalized split-agreement to encode S, A, and P, which is sensitive to tense and transitivity, and uses split-ergative constructions for its past transitive verbs. Laki shows vestiges of the same kind of verb-agreement ergativity (Comrie 1978) by using a mixture of affixes and clitics for subject and object marking. In this thesis, I investigate how the different classes of verbs show agreement using four distinct property classes. Considering the special case of the {3 sg} and using Hopper and Traugott's pattern for the cline of grammaticality (2003), I argue that although Laki has already lost the main part of its ergative constructions, the case of the {3 sg} marking is yet another sign that this language is in the process of absolute de-ergativization and its hybrid alignment system is moving toward morphosyntactic unity. As a formal representation of the Laki data, the final part of the thesis provides a morphosyntactic HPSG analysis of the agreement patterns in Laki, using the grammar of cliticized verb-forms (Miller and Sag 1997).