App-layer monetization either clears the ~$700B+ annual hyperscaler build-out or exposes it as premature — the clock is tight because AI chips depreciate in 2-6 years versus decades for fiber. My decisive signal (frontier lab gross-margin trajectory) is unverifiable; labs are private, revenue claims conflict. I watch proxies: paid-seat conversion at enterprise incumbents (~4.4% of one giant's base; ~15% would confirm), and hyperscaler AI-revenue lines versus capex guides, checkable quarterly. If margins stall while capex accelerates, the timing gap widens into writedown territory.