This case study examines a class of AI risk that is already operational, externally generated, and materially ungoverned: decision-shaped AI output produced under correct facts. The core finding is not that AI systems hallucinate, misstate evidence, or violate explicit rules. The finding is that they assemble accurate claims into authoritative, decision-ready narratives in regulated healthcare contexts, without accountability, auditability, or enforceable role boundaries. For risk and finance leadership, the exposure is not hypothetical. It is immediate and structural: Once AI-mediated decision influence exists, the absence of reasoning-level evidence becomes a governance failure in its own right. This paper demonstrates why that failure is now unavoidable, and why governance cannot be deferred.