Software quality must be viewed as an emergent property of architectural decisions rather than a post-development discovery. It is not achieved through testing alone; it is secured through intentional design. This paper, based on the keynote for Software Quality Days 2026, explores the foundational and evolving role of software architecture design as the primary driver of quality assurance. By adopting a “shift-left” imperative, we move from a reactive “detect and fix” mentality to a proactive “prevent and design” philosophy. We first examine the role of architectures for quality engineering. Then, we discuss the techniques architectural design supports to achieve quality. The paper ends with an overview of the strategic role of architectural design for quality assurance from monolithic applications to agentic systems.