diff --git a/src/lib/server/db/repositories/monitoring.ts b/src/lib/server/db/repositories/monitoring.ts
index d171c1f0..3e12b3b8 100644
--- a/src/lib/server/db/repositories/monitoring.ts
+++ b/src/lib/server/db/repositories/monitoring.ts
@@ -333,8 +333,8 @@ export class MonitoringRepository extends BaseRepository {
    * Recent samples the Confirmation Threshold resolver needs, newest first: scheduled-check
    * observations (REALTIME/TIMEOUT/ERROR) plus incident/maintenance overlays. MANUAL pushes
    * and DEFAULT fill are excluded — they stay transparent to the counter. Returns `type` so
-   * the resolver can stop at overlay rows (freeze); observations whose status is NO_DATA are
-   * skipped as neutral by the resolver.
+   * the resolver can stop at overlay rows (freeze). Observations whose status is NO_DATA are
+   * excluded entirely (neutral — they neither advance nor reset the count and must not consume lookback slots).
    */
   async getRecentSamplesForConfirmation(
     monitor_tag: string,
@@ -346,6 +346,7 @@ export class MonitoringRepository extends BaseRepository {
       .where("monitor_tag", monitor_tag)
       .where("timestamp", "<", beforeTs)
       .whereIn("type", [...OBSERVED_CHECK_TYPES, ...OVERLAY_TYPES])
+      .whereNot("status", GC.NO_DATA)
       .orderBy("timestamp", "desc")
       .limit(limit);
   }
diff --git a/src/lib/server/services/confirmationThreshold.ts b/src/lib/server/services/confirmationThreshold.ts
index a553b4bd..152bf9bb 100644
--- a/src/lib/server/services/confirmationThreshold.ts
+++ b/src/lib/server/services/confirmationThreshold.ts
@@ -32,8 +32,9 @@ export interface ConfirmationDeps {
 
 // Overlay sample types that freeze the count (must match OVERLAY_TYPES in the monitoring repository).
 const OVERLAY_TYPES: string[] = [GC.INCIDENT, GC.MAINTENANCE];
-// Extra lookback rows beyond the threshold, to tolerate neutral (NO_DATA) rows that are skipped
-// rather than counted. Pathologically neutral-dense histories may delay confirmation by a check.
+// Extra lookback rows beyond the threshold: headroom for the anchor row and any interleaved
+// overlay rows. NO_DATA observations are excluded by the query (neutral), so they never
+// consume slots — the buffer does not need to scale with NO_DATA density.
 const LOOKBACK_BUFFER = 10;
 
 /**
@@ -90,7 +91,7 @@ export async function resolveConfirmedStatus(
   for (const row of recent) {
     if (row.type !== null && OVERLAY_TYPES.indexOf(row.type) !== -1) break; // freeze boundary
     const rawSide = sideOf(row.raw_status);
-    if (rawSide === null) continue; // NO_DATA: neutral — neither advance nor reset
+    if (rawSide === null) continue; // NO_DATA: neutral (excluded by the query; this is a defensive guard)
     if (rawSide === observedSide && sideOf(row.status) === confirmedSide) {
       pendingRun++;
       pendingTimestamps.push(row.timestamp);
@@ -119,5 +120,6 @@ function confirmedSideStatus(
     if (row.type !== null && OVERLAY_TYPES.indexOf(row.type) !== -1) continue;
     if (sideOf(row.status) === confirmedSide && row.status) return row.status;
   }
+  // Defensive fallback (unreachable when an anchor was found above); side is correct, severity may coarsen.
   return confirmedSide === "UP" ? GC.UP : GC.DOWN;
 }