Beyond the Autonomy Paradox: A Delphi-Based Framework for Harmonizing Language Testing in Turkish Higher Education

English serves as the primary global language for communication. Despite its significance, Türkiye consistently ranks low in international English proficiency indices. Turkish higher education institutions utilize English Preparatory Programs (EPPs) to equip students for English-medium instruction, but the quality and consistency of assessment within these schools remain a systemic concern. This study investigates validity and comparability issues within the language testing practices of 50 state and foundation universities in Türkiye. Adopting an explanatory sequential mixed-methods design, the research gathered qualitative data through semi-structured interviews and focus groups with 208 practitioners. These findings then informed a three-round modified Delphi study with experts to reach consensus on systemic challenges. The results reveal a significant "autonomy paradox," where institutional freedom leads to a lack of standardized assessment frameworks, resulting in wide variations in exam difficulty, scoring, and security. Legal ambiguities and varying assessment literacy exacerbate the comparability gap. The study concludes with a proposed framework for national alignment, arguing that sustainable improvement requires a shift from fragmented practices toward a consensus-based, systemic approach to quality assurance.