diff --git a/src/AcDream.App/Plugins/AppAutomationSurface.cs b/src/AcDream.App/Plugins/AppAutomationSurface.cs
index f000d31b..90e929ed 100644
--- a/src/AcDream.App/Plugins/AppAutomationSurface.cs
+++ b/src/AcDream.App/Plugins/AppAutomationSurface.cs
@@ -384,14 +384,27 @@ internal sealed class AppAutomationSurface
     }
 
     // ── IMagicCommands ────────────────────────────────────────────────────
+    /// <summary>
+    /// True while an action the server has not acknowledged is in flight.
+    /// </summary>
+    /// <remarks>
+    /// Reads the shared busy count, which the cast path increments
+    /// (<c>FreeHandsAndCastSpell</c> @0x00566EF0) and the server's UseDone
+    /// decrements. NOT <c>RuntimeSpellCastState.LastRequestedSpellId</c>: that
+    /// records the last spell requested and is cleared only by Reset at session
+    /// teardown, so using it as a busy flag latches true after the first cast
+    /// and never clears -- which is exactly what stalled MossTank's first buff
+    /// pass at one cast.
+    /// </remarks>
     public bool IsCasting
     {
         get
         {
-            RuntimeSpellCastState? cast;
+            GameRuntime? runtime;
             lock (_gate)
-                cast = _cast;
-            return cast?.LastRequestedSpellId is not null;
+                runtime = _runtime;
+            return runtime is not null
+                && runtime.InventoryOwner.Transactions.BusyCount > 0;
         }
     }
 
@@ -408,6 +421,8 @@ internal sealed class AppAutomationSurface
             return PluginCastGate.Unavailable;
         if (!spellbook.Knows(spellId))
             return PluginCastGate.NotKnown;
+        if (IsCasting)
+            return PluginCastGate.Busy;
 
         return cast.EvaluateCastGate(spellId) switch
         {