Comparison-Indexed Record Compatibility in Finite Causal Orders

This conceptual and methodological quantum-foundations paper defines a finite constrained-record model on a causal poset. At a selected comparison event, specified record labels are compatible exactly when they admit an extension over that event's causal past. The paper proves an entailed-literal closure, restriction to earlier comparison events, structural invariance under constrained-system isomorphism, linear-extension independence, and an exact binary cycle-parity and assignment-count criterion. It also gives a terminating audit method for distinguishing compatibility, entailment, uniqueness, persistence, actualization, and the claimed invariance class.The result is deliberately bounded. Comparison-indexed compatibility may be defeated at a later comparison event. The finite construction does not supply outcome selection, probabilities, collapse dynamics, operational record semantics, Lorentz covariance, or a localized AQFT measurement instrument. A detailed non-transfer ledger identifies the additional structures required before finite order-theoretic consistency could support a claim in local quantum field measurement theory.This is a finite conceptual and methodological note, not a new physical theory or empirical prediction.