diff --git a/scripts/src/hwlab-node-web-observe-analyzer-source.ts b/scripts/src/hwlab-node-web-observe-analyzer-source.ts
index 3599e8d7..200784d5 100644
--- a/scripts/src/hwlab-node-web-observe-analyzer-source.ts
+++ b/scripts/src/hwlab-node-web-observe-analyzer-source.ts
@@ -1418,6 +1418,16 @@ function sessionInvariantNavigationWindows(control) {
   return windows;
 }
 
+function sessionInvariantCanarySessionIds(control) {
+  const ids = new Set();
+  for (const row of control || []) {
+    const detail = objectValue(row?.detail);
+    const canarySessionId = stringOrNull(detail.canarySessionId);
+    if (canarySessionId) ids.add(canarySessionId);
+  }
+  return ids;
+}
+
 function sessionChangeSamplesOutsideControlledNavigation(samples, key, windows) {
   const canaryIds = new Set((windows || []).map((item) => item.canarySessionId).filter(Boolean));
   if (canaryIds.size === 0) return samples.filter((item) => item?.[key]);
@@ -1438,10 +1448,14 @@ function sampleInControlledNavigationWindow(sample, windows) {
 function sampleRefInControlledNavigationSessionWindow(sample, windows) {
   const ms = timestampMs(sample?.ts);
   if (!Number.isFinite(ms)) return false;
+  if (!sampleRefMatchesControlledNavigationSession(sample, windows)) return false;
+  return (windows || []).some((window) => ms >= window.startMs && ms <= window.endMs);
+}
+
+function sampleRefMatchesControlledNavigationSession(sample, windows) {
   const routeSessionId = stringOrNull(sample?.routeSessionId);
   const activeSessionId = stringOrNull(sample?.activeSessionId);
   return (windows || []).some((window) => {
-    if (ms < window.startMs || ms > window.endMs) return false;
     const expected = [window.canarySessionId, window.alternateSessionId].filter(Boolean);
     return expected.some((sessionId) => sessionId === routeSessionId || sessionId === activeSessionId);
   });
@@ -1458,7 +1472,7 @@ function isBlankHydrationProjectionSample(sample) {
 
 function controlledNavigationHydrationCrossPageDiff(row, windows, sampleBySeq) {
   if (row?.diffKind !== "projection") return false;
-  if (!sampleRefInControlledNavigationSessionWindow(row.control, windows) || !sampleRefInControlledNavigationSessionWindow(row.observer, windows)) return false;
+  if (!sampleRefMatchesControlledNavigationSession(row.control, windows) || !sampleRefMatchesControlledNavigationSession(row.observer, windows)) return false;
   const control = sampleBySeq.get(Number(row?.control?.seq));
   const observer = sampleBySeq.get(Number(row?.observer?.seq));
   return isBlankHydrationProjectionSample(control) || isBlankHydrationProjectionSample(observer);
@@ -2272,6 +2286,7 @@ function buildRuntimeAlerts(samples, control, network, consoleEvents, errors) {
   const domDiagnostics = [];
   const executionErrors = [];
   const baselineExecutionErrors = [];
+  const canarySessionIds = sessionInvariantCanarySessionIds(control);
   const firstPromptMs = promptTimes.length > 0 ? promptTimes[0] : Infinity;
   const firstSeenExecutionErrorMs = new Map();
   for (const sample of samples) {
@@ -2353,7 +2368,9 @@ function buildRuntimeAlerts(samples, control, network, consoleEvents, errors) {
         textHash,
         preview: limitText(candidate.text, 260)
       };
-      if (baseline) baselineExecutionErrors.push(event);
+      const eventSessions = [event.routeSessionId, event.activeSessionId].filter(Boolean);
+      const nonCanarySession = canarySessionIds.size > 0 && !eventSessions.some((sessionId) => canarySessionIds.has(sessionId));
+      if (baseline || nonCanarySession) baselineExecutionErrors.push({ ...event, baseline: true, baselineReason: nonCanarySession ? "non-canary-session" : "pre-first-prompt" });
       else executionErrors.push(event);
       domDiagnostics.push({
         seq: sample.seq ?? null,