Anisotropic Gravitational-Wave Propagation in G■

G■ derives a discrete anisotropic Einstein equation with octahedral cubic symmetry that extends to gravitational-wave propagation: v_GW(n,f) = c [1 − ξ_GW (f/f_Pl)^2 Σ n_i^4], with the same preferred axes as the photon Lorentz-Invariance Violation (LIV) sector. The framework is stabilized by an orientation-rigidity principle inspired by quasicrystal theory, although the underlying structure is strictly crystalline rather than quasicrystalline. The triad of three symmetry axes constitutes a rigid invariant, preserving its orientation under allowed deformations. A key consequence is a rigid-triad multimessenger test: once the axes are calibrated using a single observable (e.g., the CMB), the corresponding axes for the photon LIV, gravitational-wave, and Einstein-equation sectors are predicted without additional free parameters. The cubic form and axis orientations are derived and rigidly constrained, whereas the overall scalar amplitude remains phenomenological. Any measurable misalignment of the preferred axes between different messengers would falsify G■. This prediction represents a fourth independent manifestation of the model’s characteristic cubic symmetry signature.