<p>Climate policy is widely recognized as a key determinant of future emissions trajectories, yet the integration of diverging policy pathways into climate scenario frameworks remains limited. Shared Policy Assumptions (SPA), which describe future climate policy mixes, have received far less attention than Shared Socioeconomic Pathways (SSP) and Representative Concentration Pathways (RCP). Yet climate policy instruments differ in ambition, design, and governance logic, all of which shape mitigation outcomes. A more granular assessment of policy instruments in climate modelling is crucial to increase their validity. We address this gap by developing a novel SPA framework rooted in public policy and political science. We construct four ideal-typical SPA that vary in climate ambition and depth of state intervention: Green State, Ecological Republic, Market-Liberal State, and Conserving State. We illustrate the empirical operationalization of SPA through sector-specific policy mixes across energy, transport, buildings, agriculture and industry based on a case study of Swiss climate policy. We argue that using a more granular SPA framework in climate modelling would enhance its realism and policy relevance by enabling more nuanced assessments of climate policy pathways. Our framework contributes to more comprehensive and context-sensitive climate scenario development and provides a foundation for future work on quantifying policy impacts and expanding SPA to other national contexts.</p>