Information-Preserving Execution and Stability in Block-Structured Markov Games

Simultaneous actions are often sampled in a linear administrative order. Block-SeBIL distinguishes this administrative order from strategic information in finite discounted games with declared block histories and selectors. We prove that hiding sampled actions until commitment preserves the game when the implementation also preserves the prescribed joint policy law, whereas revelation can change it. The resulting protocol-to-evidence contract combines structured sensitivity, invariant-region, and oracle-residual bounds to give conditional contraction and error guarantees. A legal two-state general-sum family attains its comparison bound in span coordinates: with γ=0.95 and gain scale 3, the strict local contraction threshold is L*=4.2935302 for every τ>0, and the supremum of certified normalized radii tends to zero there. Controlled game and oracle diagnostics illustrate these conditional guarantees; numerical LP checks are not formal real-arithmetic certificates. In PettingZoo MPE Simple Spread v2, a five-seed fixed-policy comparison gives identical hidden/parallel action traces, while a policy that uses revealed actions changes 77.1% of actions. A long-run aggregate summary records hidden/parallel agreement over 3,333,325 cycles per arm, but lacks the per-episode traces required for independent completion verification. These are protocol diagnostics, not learner benchmarks or a general semantic compiler.