In the era of the Fourth Industrial Revolution and digital transformation, project management faces emergent challenges, escalating complexity, shifting success criteria, and intensified resource conflicts, that necessitate a reappraisal of prevailing decision‑making paradigms. Despite advances in decision‑support techniques, the absence of an integrative model that systematically situates decision types across hierarchical authority levels and project lifecycle stages has engendered ambiguity in authority allocation and governance inefficiencies. To address this gap, the present study develops an integrated decision‑making framework that systematically identifies key decisions and classifies them along two dimensions, project lifecycle and governance level, thereby providing an analytical basis for examining project authority structures. In Phase I, a systematic literature review following the PRISMA protocol, complemented by thematic analysis and semi‑structured interviews, yielded a taxonomy of 32 critical decisions distributed across five lifecycle phases and three governance levels (strategic, technical, operational). In Phase II, the framework was empirically examined in a defense‑industry with high complexity and uncertainty. A structured questionnaire was administered to project managers and senior officials to analyze observed patterns of authority allocation. Findings indicate that governance in defense organizations is characterized by a duality of “strategic discipline-technical authority”: strategic decisions and a subset of executive decisions remain concentrated at the organizational level, whereas technical decisions concerning risk management, schedule, and cost are predominantly vested in project managers. The resulting time–authority matrix enables organizations to anticipate decision‑making bottlenecks and to mitigate line‑versus‑staff conflicts, thereby enhancing the clarity and effectiveness of project governance.