Dense-regime dynamics and closed-loop adversarial exploitation

Characterize the behavior of the query-aware sentinel admission index beyond the measured competitor-density boundary in the dense regime, including whether a closed-loop adversary can exploit the resulting fragmentation and the gate’s loss of control.

Background

The paper establishes its witness-deficit law primarily in the sparse emergence regime, where the hub’s retrieval and sentinel coverage events coincide. In the dense regime, legitimate in-region documents compete with the hub, causing fragmentation and decoupling exposure from maintenance churn; the paper measures this transition but does not characterize its behavior beyond the observed boundary.

A concrete unresolved direction is a closed-loop adversary that exploits the under-covered region, shifts the targeted region after sentinel promotions, or deliberately weaponizes the redundancy-aware monitor’s churn budget. Such an adversary could reveal limitations not captured by the paper’s defender-favorable continued-promotion analysis.

References

That same axis is \emph{open in the dense regime}: past the competitor-density boundary of \S\ref{sec:dense}, fragmentation co-governs and the gate is no longer the controlling factor---a boundary we measure but do not push further (a closed-loop adversary that exploits it is future work).

— Coverage Is Not Redundancy: Maintenance Cost and Exposure of Query-Aware Admission Indexes in Vector Databases Under Workload Drift  (2608.16043 - Pathak, 17 Aug 2026) in Section 7, paragraph “The open axes”; see also Section 8, “Limitations and Threats to Validity”

On the regime/budget axis, the question is open by construction: whether the established floor is operationally significant is undecided until $\tau$ and the budgets are deployment-calibrated.

— Coverage Is Not Redundancy: Maintenance Cost and Exposure of Query-Aware Admission Indexes in Vector Databases Under Workload Drift  (2608.16043 - Pathak, 17 Aug 2026) in Section 7, paragraph “The open axes”; see also Section 7, paragraph “Budget-dependent, by construction”