Contemporary desktop operating systems prioritize functionality, compatibility, and performance, while security and safety are largely implemented as reactive layers. This paper proposes an alternative architectural foundation: an integrity-first desktop operating system in which identity, safety, and recovery are treated as primary design primitives rather than auxiliary features. We introduce a phase-governed operational model that dynamically constrains system capabilities under instability, a triadic integrity kernel that structurally separates proposal, execution, and verification, and a closure mechanism that enables deterministic recovery after loss of system integrity. Artificial intelligence, where present, is structurally confined to advisory roles and explicitly denied execution authority. The proposed architecture is intended to resist persistent compromise, adaptive and AI-driven threats, and cascading system failure by refusing unsafe computation rather than attempting remediation after execution. This paper presents a conceptual framework suitable for desktop environments without disclosing implementation mechanisms.