Invariant Observer Geometry

Invariant Observer Geometry formalizes observers as geometric entities whose admissible structure governs stability, semantic projection, and drift behavior in near-critical systems. The paper defines observer states as subgroup selections acting on distinguishability space and shows that only invariant observer geometries preserve basin structure, semantic invariance, and spectral admissibility. Observer drift is characterized as a geometric instability induced by curvature, mixed-gate interactions, or thin margins. The theory proves that invariant observer geometry is a necessary condition for stable system evolution and that all admissible semantic structures are induced by observer invariants within the Einsteinian Stack.