This study offers a critical reconstruction of the lost reply of Khosrow II to Kavadh II (Shiruyeh), originally composed in Middle Persian and preserved indirectly in later historical and literary sources. Written at a decisive moment of political transition in the late Sasanian period, the letter illuminates the relationship between royal legitimacy, political authority, and the tradition of ethical counsel in pre-Islamic Iran.

Primary accounts from Islamic historians and the Shahnameh were systematically collected, and the passages attributed to the letter were comparatively examined. Through internal and external criticism, recurring elements were identified and later interpolations or abridgements distinguished from the text’s core. The reconstruction follows established patterns of Sasanian official correspondence, including an invocatory preface, formal address, responses to accusations, and an advisory conclusion.

Despite narrative variations, several passages consistently recur across the sources and may be regarded as the essential core of the letter. These sections comprise Khosrow II’s defense of his political legitimacy, justification of his royal conduct, and advisory counsel addressed to his successor. Stylistic and structural analysis indicates conformity with Sasanian administrative conventions, while the advisory elements function to reinforce royal authority. The study thus not only clarifies the political significance of this correspondence but also proposes a methodological framework for examining other lost Sasanian epistles.