This article examines why technically coherent public financial management reforms struggle when budget systems are embedded in coalition maintenance and coercive allocation in South Sudan with comparison to Liberia and Sierra Leone. It asks how capability-trapped budget reform structures political order during the post-conflict reform era from the mid-2000s to the present, combining public financial management theory, political economy of budgeting, and “good enough governance” arguments with a research design centred on budget execution analysis, reading of PEFA and audit materials, interviews with reform participants, and comparison across fragile-state PFM trajectories. The central argument is that the issue under study is not best explained as a discrete policy failure or a short-lived crisis. Rather, it is reproduced through linked institutional and political mechanisms that reshape incentives, authority, and access to resources over time (Allen & Tommasi, 2001; Andrews, 2013) (Wildavsky, 1986; Schick, 1998). Across the paper, the analysis tracks how these mechanisms operate in practice, what variation they generate, and why reform agendas that ignore the underlying political settlement rarely succeed. The article therefore contributes both a conceptual synthesis and a grounded comparative interpretation of the focal case. Its wider implication is that durable reform requires institutional redesign, political bargaining, and accountability strategies capable of reaching the real sites where power is exercised (Caiden, 1988; Grindle, 2004) (PEFA, 2012; PEFA, 2021).