For over 25 years, the Software Development Life Cycle (SDLC) has provided a structured framework for planning, building, testing, and maintaining software systems. Originally designed for monolithic development and perimeter-based security, the SDLC has evolved to address today’s complex software supply chain. Modern practices integrate open-source governance, third-party risk management and description, SBOM generation (tranisitive), secure build pipelines, and continuous monitoring. SDLC now extends beyond code creation, encompassing dependency integrity, provenance, and lifecycle transparency across a distributed ecosystem.