The Sustainable Development Goals (SDGs) represent an indivisible agenda in which interactions among goals—synergies and trade-offs—must be managed. While substantial progress has been made in quantitative modeling and network analysis of SDG interactions, systematic evidence drawn from empirical policy cases remains limited, leaving a persistent knowledge gap between theoretical analysis and on-the-ground practice. This study screened 128 empirical case study papers cited in Chapter 3.4 of the IPCC Sixth Assessment Report (AR6) Synthesis Report (SYR), which addresses long-term interactions among adaptation, mitigation, and sustainable development. Papers were classified into five domains—energy and power; land use, forests, and agriculture; urban, transport, waste, and local governance; industry, supply chains, and circular economy; and governance—and systematically analyzed for synergies, trade-offs, enabling factors, and remaining challenges. Findings indicate that synergies consistently arise not from single measures but from cross-sectoral policy integration, long-term institutional frameworks, multi-criteria assessment, inclusive stakeholder engagement, and aligned incentive structures. Trade-offs, by contrast, were consistently associated with institutional fragmentation, asymmetric power and resource distribution, short-termism, and incoherent policy mixes rather than appearing as inevitable outcomes. Five key driving forces for synergy promotion and trade-off mitigation were identified: policy objective integration, inclusive governance and redistribution of agency, long-term vision and time horizon reorientation, incentive structure redesign, and institutional capacity for learning and adaptation. This study advances the literature by moving beyond descriptive mapping of SDG interactions to a mechanism-oriented analysis that explains how policy design and governance arrangements shape or mitigate these interactions in practice. These findings suggest that the most impactful leverage points reside in deep systemic properties—governance structures, decision-making rules, and dominant development paradigms—rather than in isolated technical or policy interventions, and that strategic combinations of shallow and deep interventions are required to enhance both effectiveness and political feasibility in SDG implementation.