Post-Session Execution Assurance (PSEA): A Security Model for Verifying Authority at the Moment of Action

Modern security architectures assume that trust established at login can safely extend to all subsequent actions within a session. This assumption is fundamentally flawed. Sessions preserve the memory of authentication but not the certainty of authority. Post-Session Execution Assurance (PSEA) is an architectural security model that addresses this gap by requiring cryptographic proof of real human presence, device trust, and execution authority at the exact moment a sensitive action is approved -- independent of prior authentication or session state. This paper defines the PSEA model, its core principles, its distinction from existing security paradigms, and its implications for regulated and mission-critical systems.