Abstract As computation becomes perceptive, predictive, and generative, interaction no longer begins with a click, a tap, or a prompt. Systems increasingly act before users do—inferring intent, reallocating attention, and shaping outcomes through silence, defaults, and thresholds rather than explicit commands. In this condition, the central problem of design is no longer interface usability, but design governance: who is allowed to act, when interaction should surface, and how human agency survives when cognition itself is partially delegated. This white paper introduces Ambient Cognitive Design (ACD) as a framework for systems that participate implicitly in human cognition. Extending affordance thinking beyond static artifacts, it formalizes a new vocabulary for the "Generative UX" era: Generative Affordances: Dynamic manifestation and dissolution of intent-based interfaces. Implicit Cognitive Delegation: The stewardship of delegated mental tasks. Cognitive Sovereignty: Governance of contestability and non-delegable human agency. Rather than speculating about distant futures, this work responds to infrastructure already in use: voice assistants, wearables, spatial computing, and LLMs. It argues that ambient systems fail not because they lack capability, but because they lack explicit governance—allowing delegation to drift into substitution and calmness into opacity. Keywords Human-Computer Interaction (HCI), Generative User Experience,Generative User Interface, Ambient Intelligence, Cognitive Design, Design Governance, Generative Affordance, AI Policy, Human Agency.