This study investigates the valency and actant structure of the speech verb ayt (“to say”) in the Middle Turkic monument Gulistan bit Turki, with the aim of clarifying its historical combinatory potential and its continuity with modern Kazakh. The research is based on A. Karamanlioglu’s transcription of the text. A corpus of more than 40 verb collocations with ayt was extracted and analyzed. The study applied a structural–semantic method to identify actant frames, a historical–comparative approach to trace diachronic developments, and a statistical-corpus analysis to determine frequency and distribution of grammatical forms. Data were systematically coded for agent, patient, addressee, and modifier roles, and then compared with modern Kazakh usage. The results demonstrate that in Gulistan bit Turki the verb ayt exhibited six actant slots, forming one- to six-valent constructions. Although its syntactic valency remained stable, its semantic scope was broader in medieval Turkic, covering meanings such as reporting, ordering, proclaiming, debating, and objecting. Over time, these functions split across several verbs in modern Kazakh (aytu, soyleu, deu, zhariyalau, etc.). Thus, the verb shows diachronic narrowing of semantic valency but persistence of syntactic frames. These findings enrich the historical syntax of Turkic languages, highlight structural continuity between Middle Turkic and modern Kazakh, and provide methodological guidance for annotating historical corpora. The study also has pedagogical implications for teaching diachronic Turkic linguistics and contributes to a broader understanding of argument structure in historical texts.