Geopolitical conflicts, climate change and debt shocks in the post pandemic period have disrupted global fiscal systems and exposed the limitations of mechanistic budgeting and static forecasting. This research investigates how the public sector achieves budgeting results within the uncertainty of adaptive and flexible systems, incorporating predictive analytics, integrates adaptive governance, digital fiscal systems, and institutional complementarity in public sector budgeting unpredictability. This research uses secondary data from 58 countries covering the period 2020- 2024 obtained from the IMF, OECD, World Bank, and World Uncertainty Index incorporating system of equations and multilevel regression analysis. This research showed that fiscal coordination (β=0.41), institutional accountability (β=0.39), and digital budgeting (β=0.34) combined explained as much as 83 percent of the budget performance resilience, with disruption intensity as the moderating variable. Those countries with strong credible fiscal governance systems, independent fiscal oversight, and digital interconnectivity maintained smaller fiscal deficits and rapid recovery. This research makes a significant contribution to theory of fiscal federalism by embedding adaptive coordination within a construct of digital transparency with a revised stress testing framework. From a practice perspective, this research reinforces the reform of public financial management with the adaptive element of real-time fiscal flex and trust. The findings encourage policymakers to implement digital accountability, mid-year budget reviews, and contingency anchors, while transitioning from compliance-based governance to adaptive, data-driven fiscal governance to achieve sustainable stability.