diff --git a/src/AcDream.Core/Items/ClientObjectTable.cs b/src/AcDream.Core/Items/ClientObjectTable.cs
index 98d4f062..1be5f3ba 100644
--- a/src/AcDream.Core/Items/ClientObjectTable.cs
+++ b/src/AcDream.Core/Items/ClientObjectTable.cs
@@ -42,6 +42,7 @@ public sealed class ClientObjectTable
 {
     private readonly ConcurrentDictionary<uint, ClientObject> _objects = new();
     private readonly ConcurrentDictionary<uint, Container> _containers = new();
+    private readonly Dictionary<uint, List<uint>> _containerIndex = new();
 
     /// <summary>Fires when an object is first added to the session.</summary>
     public event Action<ClientObject>? ObjectAdded;
@@ -89,6 +90,7 @@ public sealed class ClientObjectTable
     /// Register / refresh an object in the table. Called on
     /// CreateObject for item-typed weenies and on IdentifyObjectResponse
     /// to fill in detail properties.
+    /// Does NOT update the container index — use Ingest for container-tracked objects.
     /// </summary>
     public void AddOrUpdate(ClientObject item)
     {
@@ -123,7 +125,7 @@ public sealed class ClientObjectTable
         item.ContainerId = newContainerId;
         item.ContainerSlot = newSlot;
         item.CurrentlyEquippedLocation = newEquipLocation;
-
+        Reindex(item, oldContainer);
         ObjectMoved?.Invoke(item, oldContainer, newContainerId);
         return true;
     }
@@ -135,6 +137,8 @@ public sealed class ClientObjectTable
     public bool Remove(uint itemId)
     {
         if (!_objects.TryRemove(itemId, out var item)) return false;
+        if (item.ContainerId != 0 && _containerIndex.TryGetValue(item.ContainerId, out var l))
+            l.Remove(itemId);
         ObjectRemoved?.Invoke(item);
         return true;
     }
@@ -275,8 +279,31 @@ public sealed class ClientObjectTable
         return obj;
     }
 
-    // Filled in Task 6 (container index). No-op until then.
-    private void Reindex(ClientObject obj, uint oldContainerId) { }
+    private void Reindex(ClientObject obj, uint oldContainerId)
+    {
+        if (oldContainerId != obj.ContainerId && oldContainerId != 0
+            && _containerIndex.TryGetValue(oldContainerId, out var oldList))
+            oldList.Remove(obj.ObjectId);
+
+        if (obj.ContainerId != 0)
+        {
+            if (!_containerIndex.TryGetValue(obj.ContainerId, out var list))
+                _containerIndex[obj.ContainerId] = list = new List<uint>();
+            if (!list.Contains(obj.ObjectId)) list.Add(obj.ObjectId);
+            list.Sort((a, b) => SlotOf(a).CompareTo(SlotOf(b)));
+        }
+    }
+
+    private int SlotOf(uint guid) =>
+        _objects.TryGetValue(guid, out var o) ? o.ContainerSlot : int.MaxValue;
+
+    /// <summary>
+    /// Ordered item guids in a container (retail object_inventory_table), by ContainerSlot.
+    /// Returns a SNAPSHOT (safe to hold / read off-thread); empty for an unknown container.
+    /// </summary>
+    public IReadOnlyList<uint> GetContents(uint containerId) =>
+        _containerIndex.TryGetValue(containerId, out var l)
+            ? l.ToArray() : System.Array.Empty<uint>();
 
     /// <summary>
     /// Flush the table — typically called on logoff or teleport
@@ -286,5 +313,6 @@ public sealed class ClientObjectTable
     {
         _objects.Clear();
         _containers.Clear();
+        _containerIndex.Clear();
     }
 }
diff --git a/tests/AcDream.Core.Tests/Items/ClientObjectTableTests.cs b/tests/AcDream.Core.Tests/Items/ClientObjectTableTests.cs
index 04309bc6..2aed953f 100644
--- a/tests/AcDream.Core.Tests/Items/ClientObjectTableTests.cs
+++ b/tests/AcDream.Core.Tests/Items/ClientObjectTableTests.cs
@@ -317,4 +317,56 @@ public sealed class ClientObjectTableTests
         Assert.Equal(0x06001234u, table.Get(0x500000B6u)!.IconId);          // data NOT clobbered by membership
         Assert.Equal(EquipMask.MeleeWeapon, table.Get(0x500000B6u)!.CurrentlyEquippedLocation);
     }
+
+    [Fact]
+    public void ContainerIndex_IngestThenContents_OrderedBySlot()
+    {
+        var table = new ClientObjectTable();
+        table.Ingest(FullWeenie(0x510u, container: 0xC0u));
+        table.Ingest(FullWeenie(0x511u, container: 0xC0u));
+        table.MoveItem(0x510u, 0xC0u, newSlot: 1);
+        table.MoveItem(0x511u, 0xC0u, newSlot: 0);
+        Assert.Equal(new[] { 0x511u, 0x510u }, table.GetContents(0xC0u));
+    }
+
+    [Fact]
+    public void ContainerIndex_Move_ReparentsBetweenContainers()
+    {
+        var table = new ClientObjectTable();
+        table.Ingest(FullWeenie(0x520u, container: 0xC1u));
+        table.MoveItem(0x520u, 0xC2u, newSlot: 0);
+        Assert.Empty(table.GetContents(0xC1u));
+        Assert.Equal(new[] { 0x520u }, table.GetContents(0xC2u));
+    }
+
+    [Fact]
+    public void ContainerIndex_Remove_DropsFromContents()
+    {
+        var table = new ClientObjectTable();
+        table.Ingest(FullWeenie(0x530u, container: 0xC3u));
+        table.Remove(0x530u);
+        Assert.Empty(table.GetContents(0xC3u));
+    }
+
+    [Fact]
+    public void GetContents_UnknownContainer_Empty()
+    {
+        var table = new ClientObjectTable();
+        Assert.Empty(table.GetContents(0xDEADu));
+    }
+
+    [Fact]
+    public void ContainerIndex_SlotChange_ResortsInPlace() // guards the Reindex same-container early-out
+    {
+        var table = new ClientObjectTable();
+        table.Ingest(FullWeenie(0x540u, container: 0xC4u));
+        table.Ingest(FullWeenie(0x541u, container: 0xC4u));
+        table.MoveItem(0x540u, 0xC4u, newSlot: 0);
+        table.MoveItem(0x541u, 0xC4u, newSlot: 1);
+        Assert.Equal(new[] { 0x540u, 0x541u }, table.GetContents(0xC4u));
+        // move 0x540 to a later slot WITHIN THE SAME container — order must flip
+        table.MoveItem(0x540u, 0xC4u, newSlot: 5);
+        Assert.Equal(new[] { 0x541u, 0x540u }, table.GetContents(0xC4u));
+        Assert.Equal(2, table.GetContents(0xC4u).Count); // no duplicate from the same-container move
+    }
 }