In plain terms: the engine's vocabulary entry for the specific game-theory rule-set Liu Cixin laid out in *The Dark Forest* (2008) — survival is the only goal, the universe is a closed resource pool, no civilization can verify another's intent across stellar distances, so silence is the only stable strategy and any civilization revealing its location gets destroyed. The concept names a fictional doctrine the engine tracks because Western tech-billionaires + national-security thinkers adopted it as serious strategy (Hawking 2010 'civilization-ending' transmission warning, Zuckerberg book-list, Obama endorsement). It does NOT endorse the doctrine as cosmological reality. Layer-4 vocabulary for the specific game-theoretic axiom-set Liu Cixin articulated in The Dark Forest (2008): Survival lexicographic priority + zero-sum cosmic resources + Chain-of-Suspicion + Tech-Explosion leads to silence is the only stable Nash equilibrium; any civilization revealing its location is destroyed. The concept names a fictional doctrine — included as engine vocabulary because Western tech-elite + national-security adoption of the doctrine is documented at policy level (Hawking 2010 'civilization-ending' warning, Zuckerberg book-list, Obama endorsement, Silicon Valley reading lists). The concept does NOT endorse the doctrine as cosmological reality. Engine evaluation: the doctrine's structural-political function as fifth-generation information warfare cognitive-warfare vector is testable independently of cosmological reality — see divergence 'Dark Forest as Strategic-Thought Export.' [Apr 25 2026] Apr 25 cosmological-apex adjudication confirmed: this concept stays Layer-4 vocabulary documenting the FICTIONAL doctrine + its Western-policy adoption pathway. Concept does not require any Layer-1 framework-promotion to operate analytically. The divergence 'Dark Forest as Strategic-Thought Export' uses this vocabulary to evaluate fifth-generation information warfare cognitive-warfare-vector hypothesis without requiring cosmological reality.