diff --git a/src/AcDream.Core/Items/ClientObjectTable.cs b/src/AcDream.Core/Items/ClientObjectTable.cs
index 5ed850a8..b789c11c 100644
--- a/src/AcDream.Core/Items/ClientObjectTable.cs
+++ b/src/AcDream.Core/Items/ClientObjectTable.cs
@@ -205,6 +205,20 @@ public sealed class ClientObjectTable
         return true;
     }
 
+    /// <summary>
+    /// Apply a SetStackSize (0x0197) update: set the object's StackSize + Value and
+    /// fire ObjectUpdated so bound widgets refresh the quantity overlay. False if the
+    /// object is unknown. Retail: ACCWeenieObject::ServerSaysSetStackSize (0x0058...).
+    /// </summary>
+    public bool UpdateStackSize(uint guid, int stackSize, int value)
+    {
+        if (!_objects.TryGetValue(guid, out var item)) return false;
+        item.StackSize = stackSize;
+        item.Value = value;
+        ObjectUpdated?.Invoke(item);
+        return true;
+    }
+
     /// <summary>
     /// Canonical CreateObject ingestion: create-if-absent, else patch the
     /// wire-carried fields in place (retail SetWeenieDesc). Preserves the
diff --git a/tests/AcDream.Core.Tests/Items/ClientObjectTableUpdateTests.cs b/tests/AcDream.Core.Tests/Items/ClientObjectTableUpdateTests.cs
index b5ec1c78..e2bab4ea 100644
--- a/tests/AcDream.Core.Tests/Items/ClientObjectTableUpdateTests.cs
+++ b/tests/AcDream.Core.Tests/Items/ClientObjectTableUpdateTests.cs
@@ -38,4 +38,24 @@ public sealed class ClientObjectTableUpdateTests
         Assert.Equal(99, t.Get(0x50000001u)!.Properties.Ints[5]);
         Assert.True(updated);
     }
+
+    [Fact]
+    public void UpdateStackSize_knownObject_setsFieldsAndFiresUpdated()
+    {
+        var t = new ClientObjectTable();
+        t.AddOrUpdate(new ClientObject { ObjectId = 0x600u, StackSize = 1, Value = 5 });
+        bool updated = false;
+        t.ObjectUpdated += _ => updated = true;
+
+        bool ok = t.UpdateStackSize(0x600u, stackSize: 25, value: 125);
+
+        Assert.True(ok);
+        Assert.Equal(25, t.Get(0x600u)!.StackSize);
+        Assert.Equal(125, t.Get(0x600u)!.Value);
+        Assert.True(updated);
+    }
+
+    [Fact]
+    public void UpdateStackSize_unknownObject_returnsFalse()
+        => Assert.False(new ClientObjectTable().UpdateStackSize(0xDEADu, 1, 1));
 }