diff --git a/scripts/src/hwlab-node-web-observe-runner-source.ts b/scripts/src/hwlab-node-web-observe-runner-source.ts
index 154886ac..b22137aa 100644
--- a/scripts/src/hwlab-node-web-observe-runner-source.ts
+++ b/scripts/src/hwlab-node-web-observe-runner-source.ts
@@ -1989,6 +1989,7 @@ function parseAlertThresholds(value) {
     scrollJumpFromY: requiredPositiveThreshold(raw, "scrollJumpFromY"),
     scrollJumpToY: requiredPositiveThreshold(raw, "scrollJumpToY"),
     sessionRailFallbackRatio,
+    crossPageProjectionDivergenceRedMs: positiveNumber(raw.crossPageProjectionDivergenceRedMs, requiredPositiveThreshold(raw, "visibleLoadingSlowMs")),
     source: "yaml-env",
   };
 }
@@ -2408,6 +2409,7 @@ function parseAlertThresholds(value) {
     scrollJumpFromY: requiredPositiveThreshold(raw, "scrollJumpFromY"),
     scrollJumpToY: requiredPositiveThreshold(raw, "scrollJumpToY"),
     sessionRailFallbackRatio,
+    crossPageProjectionDivergenceRedMs: positiveNumber(raw.crossPageProjectionDivergenceRedMs, requiredPositiveThreshold(raw, "visibleLoadingSlowMs")),
     source: "yaml-env",
   };
 }
@@ -2795,7 +2797,12 @@ function buildFindings(samples, control, network, errors, sampleMetrics, promptN
   );
   const crossPageProjectionDiffs = crossPageDiffs.filter((item) => item.diffKind !== "trace-visibility");
   const crossPageTraceVisibilityDiffs = crossPageDiffs.filter((item) => item.diffKind === "trace-visibility");
-  if (crossPageProjectionDiffs.length > 0) findings.push({ id: "cross-page-projection-divergence", severity: "red", summary: "control and observer pages saw different projection state for the same sampled session", count: crossPageProjectionDiffs.length, samples: crossPageProjectionDiffs.slice(0, 20) });
+  const crossPageProjectionBudgetMs = alertThresholds.crossPageProjectionDivergenceRedMs;
+  const timedCrossPageProjectionDiffs = annotateCrossPageDiffTiming(crossPageProjectionDiffs);
+  const persistentCrossPageProjectionDiffs = timedCrossPageProjectionDiffs.filter((item) => Number(item.observedSpanMs ?? 0) > crossPageProjectionBudgetMs);
+  const transientCrossPageProjectionDiffs = timedCrossPageProjectionDiffs.filter((item) => Number(item.observedSpanMs ?? 0) <= crossPageProjectionBudgetMs);
+  if (persistentCrossPageProjectionDiffs.length > 0) findings.push({ id: "cross-page-projection-divergence", severity: "red", summary: "control and observer pages saw different projection state for the same sampled session beyond the configured budget", count: persistentCrossPageProjectionDiffs.length, budgetMs: crossPageProjectionBudgetMs, samples: persistentCrossPageProjectionDiffs.slice(0, 20) });
+  if (transientCrossPageProjectionDiffs.length > 0) findings.push({ id: "cross-page-projection-transient-divergence", severity: "info", summary: "control and observer pages briefly differed near a sampled transition; retained as transient evidence but not treated as persistent projection failure", count: transientCrossPageProjectionDiffs.length, budgetMs: crossPageProjectionBudgetMs, samples: transientCrossPageProjectionDiffs.slice(0, 20) });
   if (crossPageTraceVisibilityDiffs.length > 0) findings.push({ id: "cross-page-trace-visibility-divergence", severity: "info", summary: "control and observer pages differed only in visible trace row count; this is local disclosure/hydration visibility, not session/message projection divergence", count: crossPageTraceVisibilityDiffs.length, samples: crossPageTraceVisibilityDiffs.slice(0, 20) });
   const traceMessageDuplicates = detectTraceMessageDuplication(samples);
   if (traceMessageDuplicates.length > 0) findings.push({ id: "trace-assistant-message-duplicates-final-response", severity: "amber", summary: "trace rendered assistant message rows that duplicate the sealed final response", count: traceMessageDuplicates.length, samples: traceMessageDuplicates.slice(0, 20) });
@@ -5943,6 +5950,43 @@ function mergeCrossPageDiffRows(...groups) {
   return rows;
 }
 
+function annotateCrossPageDiffTiming(rows) {
+  const groups = new Map();
+  for (const row of Array.isArray(rows) ? rows : []) {
+    const controlAt = Date.parse(String(row?.control?.ts || ""));
+    const observerAt = Date.parse(String(row?.observer?.ts || ""));
+    const timestamps = [controlAt, observerAt].filter(Number.isFinite);
+    const startMs = timestamps.length > 0 ? Math.min(...timestamps) : null;
+    const endMs = timestamps.length > 0 ? Math.max(...timestamps) : null;
+    const sessionId = row?.control?.routeSessionId || row?.control?.activeSessionId || row?.observer?.routeSessionId || row?.observer?.activeSessionId || "unknown-session";
+    const key = [row?.diffKind || "projection", sessionId].join(":");
+    const group = groups.get(key) || { rows: [], firstMs: null, lastMs: null };
+    const annotated = {
+      ...row,
+      sampleStartAt: startMs === null ? null : new Date(startMs).toISOString(),
+      sampleEndAt: endMs === null ? null : new Date(endMs).toISOString(),
+      pairSkewMs: startMs === null || endMs === null ? null : endMs - startMs,
+    };
+    group.rows.push(annotated);
+    if (startMs !== null && (group.firstMs === null || startMs < group.firstMs)) group.firstMs = startMs;
+    if (endMs !== null && (group.lastMs === null || endMs > group.lastMs)) group.lastMs = endMs;
+    groups.set(key, group);
+  }
+  const result = [];
+  for (const group of groups.values()) {
+    const observedSpanMs = group.firstMs === null || group.lastMs === null ? null : group.lastMs - group.firstMs;
+    for (const row of group.rows) {
+      result.push({
+        ...row,
+        observedFirstAt: group.firstMs === null ? null : new Date(group.firstMs).toISOString(),
+        observedLastAt: group.lastMs === null ? null : new Date(group.lastMs).toISOString(),
+        observedSpanMs,
+      });
+    }
+  }
+  return result;
+}
+
 function detectAdjacentCrossPageProjectionDiffs(samples) {
   const rows = [];
   const ordered = (Array.isArray(samples) ? samples : []).slice().sort((a, b) => Number(a?.seq ?? 0) - Number(b?.seq ?? 0));