diff --git a/src/GameLogic/CastleSiege/CastleSiegeContext.cs b/src/GameLogic/CastleSiege/CastleSiegeContext.cs
index 61ff735..d9d985d 100644
--- a/src/GameLogic/CastleSiege/CastleSiegeContext.cs
+++ b/src/GameLogic/CastleSiege/CastleSiegeContext.cs
@@ -25,6 +25,7 @@ public class CastleSiegeContext
     private bool _dirty;
     private string? _crownHoldGuild;
     private DateTime? _crownHoldStartUtc;
+    private bool _lastShieldDown;
 
     /// <summary>Initializes a new instance of the <see cref="CastleSiegeContext"/> class.</summary>
     /// <param name="configuration">The cycle timing configuration.</param>
@@ -217,28 +218,31 @@ public class CastleSiegeContext
     /// <param name="holdDuration">How long the master must hold to capture.</param>
     public CrownTickResult TickCrownHold(string? eligibleGuild, bool masterHolding, DateTime now, TimeSpan holdDuration)
     {
+        var shieldDown = this.Phase == CastleSiegePhase.Siege && eligibleGuild is not null;
+        var shieldChanged = shieldDown != this._lastShieldDown;
+        this._lastShieldDown = shieldDown;
+
         if (this.Phase != CastleSiegePhase.Siege)
         {
             this._crownHoldGuild = null;
             this._crownHoldStartUtc = null;
-            return new CrownTickResult(false, CrownEvent.None, null);
+            return new CrownTickResult(false, shieldChanged, CrownEvent.None, null);
         }
 
-        var shieldDown = eligibleGuild is not null;
         var wasHolding = this._crownHoldGuild is not null;
 
         if (eligibleGuild is null || !masterHolding)
         {
             this._crownHoldGuild = null;
             this._crownHoldStartUtc = null;
-            return new CrownTickResult(shieldDown, wasHolding ? CrownEvent.HoldReset : CrownEvent.None, null);
+            return new CrownTickResult(shieldDown, shieldChanged, wasHolding ? CrownEvent.HoldReset : CrownEvent.None, null);
         }
 
         if (this._crownHoldGuild != eligibleGuild || this._crownHoldStartUtc is null)
         {
             this._crownHoldGuild = eligibleGuild;
             this._crownHoldStartUtc = now;
-            return new CrownTickResult(shieldDown, CrownEvent.HoldStarted, eligibleGuild);
+            return new CrownTickResult(shieldDown, shieldChanged, CrownEvent.HoldStarted, eligibleGuild);
         }
 
         if (now - this._crownHoldStartUtc.Value >= holdDuration)
@@ -247,10 +251,10 @@ public class CastleSiegeContext
             this._crownHoldGuild = null;
             this._crownHoldStartUtc = null;
             this._dirty = true;
-            return new CrownTickResult(shieldDown, CrownEvent.Captured, eligibleGuild);
+            return new CrownTickResult(shieldDown, shieldChanged, CrownEvent.Captured, eligibleGuild);
         }
 
-        return new CrownTickResult(shieldDown, CrownEvent.None, eligibleGuild);
+        return new CrownTickResult(shieldDown, shieldChanged, CrownEvent.None, eligibleGuild);
     }
 
     /// <summary>
@@ -363,6 +367,7 @@ public class CastleSiegeContext
         this._occupier = null;
         this._crownHoldGuild = null;
         this._crownHoldStartUtc = null;
+        this._lastShieldDown = false;
     }
 
     private ValueTask TransitionAsync(CastleSiegePhase phase, DateTime now)
@@ -393,6 +398,7 @@ public enum CrownEvent
 
 /// <summary>The result of a crown-hold tick: the shield state and any event that occurred.</summary>
 /// <param name="ShieldDown">Whether the crown shield is currently down (both switches held, defenses cleared).</param>
+/// <param name="ShieldChanged">Whether the shield state changed this tick (only then should the client be told).</param>
 /// <param name="Event">The event that occurred this tick.</param>
 /// <param name="Guild">The guild the event refers to, if any.</param>
-public readonly record struct CrownTickResult(bool ShieldDown, CrownEvent Event, string? Guild);
+public readonly record struct CrownTickResult(bool ShieldDown, bool ShieldChanged, CrownEvent Event, string? Guild);
diff --git a/src/GameLogic/PlugIns/PeriodicTasks/CastleSiegeEventPlugIn.cs b/src/GameLogic/PlugIns/PeriodicTasks/CastleSiegeEventPlugIn.cs
index 5aeafb4..9e15915 100644
--- a/src/GameLogic/PlugIns/PeriodicTasks/CastleSiegeEventPlugIn.cs
+++ b/src/GameLogic/PlugIns/PeriodicTasks/CastleSiegeEventPlugIn.cs
@@ -428,7 +428,12 @@ public sealed class CastleSiegeEventPlugIn : IPeriodicTaskPlugIn, ISupportCustom
                 return;
             }
 
-            await player.InvokeViewPlugInAsync<ICastleSiegeStatusViewPlugIn>(p => p.SetCrownShieldAsync(crown.ShieldDown)).ConfigureAwait(false);
+            // Only tell the client when the shield state actually flips — the 0xB2/0x16 packet pops a modal
+            // message box, so sending it every tick would block player input.
+            if (crown.ShieldChanged)
+            {
+                await player.InvokeViewPlugInAsync<ICastleSiegeStatusViewPlugIn>(p => p.SetCrownShieldAsync(crown.ShieldDown)).ConfigureAwait(false);
+            }
 
             switch (crown.Event)
             {