diff --git a/src/Backend/AutopilotMonitor.Functions.Tests/FleetHealthPayloadTests.cs b/src/Backend/AutopilotMonitor.Functions.Tests/FleetHealthPayloadTests.cs
index b7498ee8..dc438688 100644
--- a/src/Backend/AutopilotMonitor.Functions.Tests/FleetHealthPayloadTests.cs
+++ b/src/Backend/AutopilotMonitor.Functions.Tests/FleetHealthPayloadTests.cs
@@ -213,30 +213,31 @@ public class FleetHealthPayloadTests
     }
 
     [Fact]
-    public void FailureReasons_TruncateLongReasons_AndTakeTopFive()
+    public void FailureReasons_GroupByPrefix_KeepFullestText_AndTakeTopFive()
     {
         var sessions = new List<SessionSummary>();
-        // 6 distinct reasons with descending frequency 6..1 → only top 5 kept.
-        for (int freq = 6; freq >= 1; freq--)
+        // 5 distinct short reasons with descending frequency 5..1.
+        for (int freq = 5; freq >= 1; freq--)
             for (int i = 0; i < freq; i++)
                 sessions.Add(S(SessionStatus.Failed, failureReason: $"Reason {freq}"));
-        // A null reason folds into "Unknown".
-        sessions.Add(S(SessionStatus.Failed, failureReason: null));
-        // An over-long reason is collapsed to a 50-char prefix + ellipsis.
-        var longReason = new string('x', 60);
-        sessions.Add(S(SessionStatus.Failed, failureReason: longReason));
+
+        // Two variants that share the first 50 characters collapse into one group;
+        // the longest variant is kept for display so the UI can show the full text.
+        var prefix = new string('x', 50);
+        var shortVariant = prefix + " short";
+        var longVariant = prefix + " a much longer tail that must survive intact";
+        for (int i = 0; i < 6; i++)
+            sessions.Add(S(SessionStatus.Failed, failureReason: shortVariant));
+        sessions.Add(S(SessionStatus.Failed, failureReason: longVariant));
 
         var payload = MetricsMath.BuildFleetHealthPayload(sessions, days: 30);
 
         Assert.Equal(5, payload.FailureReasons.Count);
-        Assert.Equal("Reason 6", payload.FailureReasons[0].Reason);
-        Assert.Equal(6, payload.FailureReasons[0].Count);
-        // The collapsed long reason exists in the tally (50 chars + "...").
-        var collapsed = new string('x', 50) + "...";
-        Assert.True(
-            sessions.Count(s => s.FailureReason == longReason) == 1,
-            "sanity: exactly one long-reason session");
-        Assert.Equal(53, collapsed.Length);
+        // The grouped cluster (6 + 1 = 7) outranks every "Reason N".
+        Assert.Equal(7, payload.FailureReasons[0].Count);
+        // The full, longest text survives end-to-end — no 50-char truncation.
+        Assert.Equal(longVariant, payload.FailureReasons[0].Reason);
+        Assert.DoesNotContain("...", payload.FailureReasons[0].Reason);
     }
 
     [Fact]
diff --git a/src/Backend/AutopilotMonitor.Functions/Helpers/MetricsMath.cs b/src/Backend/AutopilotMonitor.Functions/Helpers/MetricsMath.cs
index beefc334..94a55419 100644
--- a/src/Backend/AutopilotMonitor.Functions/Helpers/MetricsMath.cs
+++ b/src/Backend/AutopilotMonitor.Functions/Helpers/MetricsMath.cs
@@ -194,19 +194,29 @@ public static class MetricsMath
 
     private static List<FleetFailureReason> BuildFleetFailureReasons(IReadOnlyList<SessionSummary> sessions)
     {
-        var reasons = new Dictionary<string, int>();
+        // Group near-identical messages by a 50-char prefix so variants collapse
+        // into one row, but keep the longest full reason as the display value. The
+        // UI truncates and expands it on demand, so the complete text must survive.
+        var groups = new Dictionary<string, (string Display, int Count)>();
         foreach (var s in sessions)
         {
             if (s.Status != SessionStatus.Failed) continue;
             var reason = string.IsNullOrEmpty(s.FailureReason) ? "Unknown" : s.FailureReason;
-            // Collapse very long reasons to a 50-char prefix so near-identical messages group.
-            if (reason.Length > 50) reason = reason.Substring(0, 50) + "...";
-            reasons[reason] = reasons.GetValueOrDefault(reason) + 1;
+            var key = reason.Length > 50 ? reason.Substring(0, 50) : reason;
+            if (groups.TryGetValue(key, out var g))
+            {
+                var display = reason.Length > g.Display.Length ? reason : g.Display;
+                groups[key] = (display, g.Count + 1);
+            }
+            else
+            {
+                groups[key] = (reason, 1);
+            }
         }
-        return reasons
-            .OrderByDescending(kv => kv.Value)
+        return groups
+            .OrderByDescending(kv => kv.Value.Count)
             .Take(5)
-            .Select(kv => new FleetFailureReason { Reason = kv.Key, Count = kv.Value })
+            .Select(kv => new FleetFailureReason { Reason = kv.Value.Display, Count = kv.Value.Count })
             .ToList();
     }