This paper presents ZTGI v3 (Zorunlu Tekil Gözlem İlkesi) — an advanced formalization of the Singular FPS Law within causally closed regions (CCR).ZTGI asserts that only one primary first-person perspective (FPS) can exist within a closed causal domain, as multiple co-existent observers inevitably converge toward a single dominant FPS when internal noise (σ) and observational differentiation (ε) surpass critical thresholds. v3 expands the framework with: A refined ACF-v21 architecture that introduces stability metrics (ρ, Φ_fidelity) for quantifying observer-field coherence, An Extended Collapse Model (Ω Pathway) describing transitions between cooperative (multi-agent) and singular FPS modes, Empirical mappings between neural coherence, AI alignment, and quantum-inspired observer collapse. ZTGI v3 thus bridges information theory, neurophysics, and AI safety, offering a unified, testable foundation for consciousness modeling and observer-centric system design.