When a posterior difference does not change the action.

Hellinger distance measures how far the hardware-derived posterior is from exact Bayes, but it does not say whether that difference changes the next action. A small error near an action threshold can matter more than a larger error far from one.

The QANTIS paper therefore performs a planner-facing check. Both posteriors enter the same standard Tiger immediate-reward rule: open right above 90 percent belief that the tiger is left, open left below 10 percent, and listen between those thresholds.

The 8-step matched-shot FPAA trajectory reports 8 of 8 action agreements. The 20-step and 32-step supporting controls report 20 of 20 and 32 of 32. Under the paper's scoring rule, cumulative value loss is 0.000 for each trajectory because there is no action disagreement.

The posterior distances do not disappear: the reported maximums for these decision checks are 0.0326, 0.0343, and 0.0228. The evidence says those deviations stayed inside the same action regions for the tested rule and trajectories.

The matched-shot 8-step decision check is tied to the primary sequential Tiger case study. The 20-step and 32-step trajectories extend the operating envelope as supporting controls. Their role is to test whether action consistency survives repeated posterior feedback, not to broaden the system claim.

The paper also includes 12-step primary fidelity evidence, Heron R3 transfer, calibration, and rare-event controls. Larger-state pilots remain exploratory and are not folded into the action-agreement claim.

The result does not prove that any planner would make the same choice. A different loss model, risk tolerance, observation sequence, hidden-state space, or threshold could convert the same posterior deviation into a different action.

Nor does immediate-action agreement validate full policy optimization. The downstream planner is classical and outside the hardware-tested module. The paper checks the immediate decision impact of the returned posterior, not a long-horizon quantum policy or end-to-end autonomous behavior.

An auditable decision record needs the hardware posterior, exact or trusted reference, distance metric, reward parameters, action thresholds, selected action, and value-loss calculation together. Without the threshold context, an action-agreement percentage cannot be reproduced or challenged.

This pattern generalizes as an assurance method, not as a general performance claim. For any new domain, the operator must define the decision rule and acceptable error region before hardware results are interpreted.

The supported result is that reported QANTIS posteriors preserve the immediate Tiger action under one specified rule. It does not establish end-to-end autonomy, automated command authority, wall-clock speedup, quantum advantage, or hardware-optimized downstream tracking and assignment.

That distinction is a design advantage. QANTIS can return bounded evidence and a clear audit trail while classical software and human governance retain authority over the action.

A belief-update service can return a posterior that is numerically imperfect yet operationally equivalent for the next decision. Conversely, a small error near a threshold can flip an action. That is why a single distribution metric cannot carry the whole systems claim.

The QANTIS evaluation sends the hardware posterior and the exact Bayes posterior through the same Tiger immediate-reward rule. Across all reported decision checks, the selected immediate action agrees. This converts posterior fidelity into decision evidence while keeping the planner classical and inspectable.

The correct conclusion remains narrow. Agreement under one immediate-action rule shows that the observed errors did not cross those tested thresholds. It does not prove that the distributions are identical, that a multi-step policy is optimal, or that a different cost model would make the same choices.

arXiv:2607.06760, submitted 7 July 2026, reports action agreement alongside posterior Hellinger distance for matched-shot and extended-horizon checks. The authors frame the result as validation of the planner-facing posterior returned by the service, not validation of the full autonomy stack around it.

This article follows that boundary. It uses 'same immediate action' rather than broader phrases such as autonomous performance, policy advantage, or mission success.