<p>Silicon Valley Bank’s March 2023 failure exposes a structural tension in size‑tiered bank supervision: the same portfolio framework designed to escalate prudential expectations can also create hidden grace periods that delay binding constraint. Using SVB’s transition from the Federal Reserve’s Regional Banking Organization program to the Large and Foreign Banking Organization program, this article traces how phased‑in enhanced prudential standards, waiver‑delayed ratings, and the internal classification of supervisory findings combined to produce a long supervisory runway during which liquidity, interest‑rate, and governance weaknesses were repeatedly identified but not decisively constrained. The article treats tiering as a dual‑use institutional technology: it reallocates supervisory resources and raises formal requirements, yet it also embeds transitional mechanisms that make deferral the path of least resistance. A public‑choice account links that deferral to internal coordination costs, signaling concerns, and the limited legal status of supervisory guidance. The analysis is institutional rather than firm‑specific and highlights why long runways are most dangerous when rapidly growing banks exhibit observable deterioration that can compound before formal intervention becomes unavoidable.</p>