We formulate an observationally testable phenomenological framework for a cosmological model motivated by octonionic pre-geometry. In this picture, the nonassociativity of the octonionic division algebra obstructs the existence of a fundamental global time and motivates a symmetry reduction to an effectively associative sector, identified with emergent four-dimensional spacetime. Residualnonassociative degrees of freedom are modeled as an effective dynamical dark-energy component. Weintroduce a minimal approach for the effective octonionic energy density and derive the associated Hubble function, luminosity distance, baryon-acoustic-oscillation distances, and effective equation of state. The resulting model admits a direct mapping onto the standard (w0,wa) dark-energy parametrization and reduces continuously to ΛCDM in the appropriate limit. We present a concrete benchmark parameterization and formulate a step-by-step likelihood strategy based on Type Ia supernovae, baryon acoustic oscillations, and direct H(z) measurements. The framework is designed as a falsifiable intermediate step between a speculative algebraic origin of spacetime and precisionlate-universe cosmology.