A predictive physical description must preserve its conditional content under admissible re-description. Invariance of predictive relations under admissible regeneration is therefore a necessary condition for prediction itself. This work examines the structural consequences of this requirement under minimal constitutional assumptions: non-empty admissible carriers and finite diagnostic closure. Beyond these conditions, no primitives are permitted. All further structure may appear only as induced observables, defined as equivalence classes of predictive content invariant under regeneration. Finite diagnostic closure restricts admissible relational summaries to finite characteristic invariants. Resolution-dependent long-range sectors generate regeneration-sensitive diagnostics and are excluded. Any admissible long-range characteristic class is therefore transverse. Regeneration-stable canonical families are shown to collapse into the carrier-bound sector, implying that any admissible long-range class is necessarily massless. Variability of characteristic structure induces diagnostic inflation and is forbidden, leaving a single invariant characteristic relation. These constraints jointly yield a uniqueness theorem: in any non-empty finitely closed admissible regime, exactly one long-range characteristic equivalence class exists. Its admissible grammar is fixed, up to representation, as the automorphism group preserving the invariant characteristic relation, yielding Lorentz kinematics at the level of effective description without postulating spacetime, fields, or propagation primitives. The invariant thus obtained coincides operationally with the empirical invariant historically designated as light. The term is adopted purely as a late identification: light is classified here as an induced effective observable, not a primitive constituent.