As Meta’s product ecosystem expanded, teams encountered inconsistencies across UI patterns, duplicated implementation effort, and gaps between design artifacts and production code. The initiative focused on defining a cohesive system architecture that connected visual language, interaction behavior, and reusable components into a shared foundation. To balance flexibility with governance, the system separated foundational primitives into a controlled Style Library while enabling more adaptable interface construction through a modular Pattern Library. This structure reduced ambiguity, improved parity between design and engineering, and allowed teams to move quickly without compromising consistency.