Spike addressing codex round-32 recommendation for plateau detection
diagnostic. Result: v3-inherited HC threshold (cos>0.95 AND dh<=5)
sits at high-gradient regions of the alert-rate surface (local/median
gradient ratio 25.5× for cos, 3.8× for dh) — locally sensitive,
not plateau-stable. Per codex round-33 review, this is corroborating
evidence for the no-natural-threshold finding (Scripts 39b-e remain
the primary proof); MC/HSC boundary dh=15 IS plateau-like (ratio
0.08) which means plateau finding applies to HC cutoff only.
Pooled doc-level deployed alert rate at v3 HC threshold = 62.28%
(vs Script 45's 17.97% inter-CPA proxy; 44pp gap framed as
"deployed-rate excess over inter-CPA proxy", NOT presumed TPR).
Companion artefacts in reports/v4_big4/alert_rate_sensitivity/.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
