diff --git a/RunCat365/TemperatureRepository.cs b/RunCat365/TemperatureRepository.cs
index ecbe1a0..311d33b 100644
--- a/RunCat365/TemperatureRepository.cs
+++ b/RunCat365/TemperatureRepository.cs
@@ -69,22 +69,40 @@ internal sealed class TemperaturePerformanceCounters : InstancedPerformanceCount
         }
     }
 
+    internal sealed class TemperatureHighPrecisionPerformanceCounters : InstancedPerformanceCounters
+    {
+        protected override string CategoryName => "Thermal Zone Information";
+        protected override string CounterName => "High Precision Temperature";
+
+        internal static TemperatureHighPrecisionPerformanceCounters? TryCreate()
+        {
+            var instance = new TemperatureHighPrecisionPerformanceCounters();
+            return instance.TryInitialize() ? instance : null;
+        }
+    }
+
     internal class TemperatureRepository
     {
         private const float KELVIN_TO_CELSIUS_OFFSET = 273.15f;
         private const float MIN_VALID_TEMPERATURE_CELSIUS = -50.0f;
         private const float MAX_VALID_TEMPERATURE_CELSIUS = 150.0f;
         private const int REFRESH_INTERVAL_TICKS = 30;
+        private const int STALE_READ_THRESHOLD = 24;
 
         private readonly TemperaturePerformanceCounters? counters;
+        private readonly TemperatureHighPrecisionPerformanceCounters? highPrecisionCounters;
+        private readonly List<float> baselineRawValues = [];
         private TemperatureInfo? temperatureInfo;
         private int ticksSinceLastRefresh;
+        private int identicalReadCount;
+        private bool hasEverVaried;
 
         internal bool IsAvailable => counters is not null;
 
         internal TemperatureRepository()
         {
             counters = TemperaturePerformanceCounters.TryCreate();
+            highPrecisionCounters = TemperatureHighPrecisionPerformanceCounters.TryCreate();
         }
 
         internal void Update()
@@ -96,9 +114,13 @@ internal void Update()
             {
                 ticksSinceLastRefresh = 0;
                 counters.RefreshInstances();
+                highPrecisionCounters?.RefreshInstances();
             }
 
             var rawValues = counters.ReadValues();
+            var variationValues = highPrecisionCounters is null ? rawValues : highPrecisionCounters.ReadValues();
+            TrackValueVariation(variationValues);
+
             var temperaturesCelsius = new List<float>(rawValues.Count);
             foreach (var temperatureKelvin in rawValues)
             {
@@ -108,7 +130,7 @@ internal void Update()
                 temperaturesCelsius.Add(temperatureCelsius);
             }
 
-            temperatureInfo = temperaturesCelsius.Count == 0
+            temperatureInfo = temperaturesCelsius.Count == 0 || IsLikelyPlaceholder()
                 ? null
                 : new TemperatureInfo
                 {
@@ -117,6 +139,48 @@ internal void Update()
                 };
         }
 
+        // Some firmware exposes an ACPI thermal zone that is not wired to a real
+        // sensor and always reports the same fixed value (e.g. 301 K). Track whether
+        // the readings have ever changed so such zones can be treated as unavailable
+        // instead of showing a misleading constant temperature. Variation is tracked
+        // on the "High Precision Temperature" counter (0.1 K granularity) when it is
+        // available, because a live sensor jitters at that resolution even when the
+        // whole-Kelvin "Temperature" counter stays flat on an idle machine; the
+        // tracking source is fixed at construction so values are never compared
+        // across the two counters' different scales.
+        private void TrackValueVariation(List<float> rawValues)
+        {
+            if (hasEverVaried || rawValues.Count == 0) return;
+
+            var sortedValues = new List<float>(rawValues);
+            sortedValues.Sort();
+
+            if (baselineRawValues.Count != sortedValues.Count)
+            {
+                baselineRawValues.Clear();
+                baselineRawValues.AddRange(sortedValues);
+                identicalReadCount = 1;
+                return;
+            }
+
+            for (var i = 0; i < sortedValues.Count; i++)
+            {
+                if (baselineRawValues[i] != sortedValues[i])
+                {
+                    hasEverVaried = true;
+                    baselineRawValues.Clear();
+                    return;
+                }
+            }
+
+            identicalReadCount += 1;
+        }
+
+        private bool IsLikelyPlaceholder()
+        {
+            return !hasEverVaried && STALE_READ_THRESHOLD <= identicalReadCount;
+        }
+
         internal TemperatureInfo? Get()
         {
             return temperatureInfo;
@@ -125,6 +189,7 @@ internal void Update()
         internal void Close()
         {
             counters?.Close();
+            highPrecisionCounters?.Close();
         }
     }
 }