diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Browse/GalaxyDiscoverer.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Browse/GalaxyDiscoverer.cs
index 7874c46a..9f60b95c 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Browse/GalaxyDiscoverer.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/Browse/GalaxyDiscoverer.cs
@@ -17,9 +17,12 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Browse;
 ///       <item>Folder per gobject; variables placed inside their owner folder.</item>
 ///       <item>Variable's full reference = <c>tag_name.attribute_name</c> — the format MXAccess
 ///         expects for read/write addressing (translated from the contained-name browse path).</item>
-///       <item>Hierarchy is rendered flat (one folder per gobject under the driver root).
-///         Nesting under <c>parent_gobject_id</c> for a true tree shape is not implemented;
-///         the flat layout is the current shipping behaviour.</item>
+///       <item>Hierarchy is nested by <c>parent_gobject_id</c>: each gobject's folder is created
+///         under the folder of the gobject named by its <c>parent_gobject_id</c> (resolved
+///         order-independently and memoised, so the parent can appear before or after the child).
+///         A gobject degrades to the driver root when its <c>parent_gobject_id</c> is <c>0</c>,
+///         self-referential, or names a gobject not present in the returned set — so a model
+///         that carries no parentage still renders flat.</item>
 ///     </list>
 /// </remarks>
 public sealed class GalaxyDiscoverer
@@ -44,12 +47,30 @@ public sealed class GalaxyDiscoverer
         ArgumentNullException.ThrowIfNull(builder);
         var objects = await _source.GetHierarchyAsync(cancellationToken).ConfigureAwait(false);
 
+        // Pass 1 — collect gobjects with a usable browse identity (order preserved), and index
+        // them by gobject_id so pass 2 can resolve a parent the source returned AFTER the child
+        // (order-independent). Only the FIRST gobject per non-zero id is indexed as a parent
+        // target; the index excludes id 0 so identity-less / un-keyed objects can't collide.
+        var usable = new List<GalaxyObject>();
+        var byId = new Dictionary<int, GalaxyObject>();
         foreach (var obj in objects)
         {
             var browseName = string.IsNullOrEmpty(obj.ContainedName) ? obj.TagName : obj.ContainedName;
             if (string.IsNullOrEmpty(browseName)) continue; // skip objects with no usable identity
+            usable.Add(obj);
+            if (obj.GobjectId != 0)
+            {
+                byId.TryAdd(obj.GobjectId, obj);
+            }
+        }
 
-            var folder = builder.Folder(browseName, browseName);
+        // Pass 2 — create each gobject's folder under its parent (memoised), then its variables.
+        // Iterating the ordered list (not the index) keeps the flat case stable and emits a
+        // folder even for objects whose gobject_id is 0 or duplicated.
+        var folders = new Dictionary<int, IAddressSpaceBuilder>();
+        foreach (var obj in usable)
+        {
+            var folder = EnsureFolder(obj, builder, byId, folders);
 
             foreach (var attr in obj.Attributes)
             {
@@ -82,6 +103,42 @@ public sealed class GalaxyDiscoverer
         }
     }
 
+    // Resolve (and memoise) the folder for a gobject, recursively creating its parent's folder
+    // first so the result nests under it. Falls back to the driver root when the parent_gobject_id
+    // is 0, self-referential, absent from the returned set, or already mid-resolution (cycle guard).
+    // Memoisation is keyed by gobject_id and only applies to non-zero ids — an id-0 object always
+    // gets its own freshly-created folder (it can be neither a parent target nor shared).
+    private static IAddressSpaceBuilder EnsureFolder(
+        GalaxyObject obj,
+        IAddressSpaceBuilder root,
+        IReadOnlyDictionary<int, GalaxyObject> byId,
+        Dictionary<int, IAddressSpaceBuilder> folders,
+        HashSet<int>? building = null)
+    {
+        if (obj.GobjectId != 0 && folders.TryGetValue(obj.GobjectId, out var existing)) return existing;
+
+        var browseName = string.IsNullOrEmpty(obj.ContainedName) ? obj.TagName : obj.ContainedName;
+        building ??= [];
+
+        IAddressSpaceBuilder parentBuilder = root;
+        if (obj.ParentGobjectId != 0
+            && obj.ParentGobjectId != obj.GobjectId
+            && !building.Contains(obj.ParentGobjectId)
+            && byId.TryGetValue(obj.ParentGobjectId, out var parentObj))
+        {
+            building.Add(obj.GobjectId);
+            parentBuilder = EnsureFolder(parentObj, root, byId, folders, building);
+            building.Remove(obj.GobjectId);
+        }
+
+        var folder = parentBuilder.Folder(browseName, browseName);
+        if (obj.GobjectId != 0)
+        {
+            folders[obj.GobjectId] = folder;
+        }
+        return folder;
+    }
+
     // PR 5.W workaround for mxaccessgw GalaxyRepository.cs:173-175 — the gateway's
     // SQL appends `[]` to array-typed `full_tag_reference` values, but MxAccess COM
     // `IInstance.AddItem` doesn't accept `[]`-suffixed addresses (so any downstream
diff --git a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Browse/GalaxyDiscovererTests.cs b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Browse/GalaxyDiscovererTests.cs
index 11b771f7..d2d72a61 100644
--- a/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Browse/GalaxyDiscovererTests.cs
+++ b/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.Tests/Browse/GalaxyDiscovererTests.cs
@@ -23,7 +23,9 @@ public sealed class GalaxyDiscovererTests
             => Task.FromResult(objects);
     }
 
-    private sealed record FolderCall(string BrowseName, string DisplayName);
+    /// <summary><c>ParentBrowseName</c> is the browse-name of the folder this folder was created under
+    /// (<c>null</c> = created at the driver root).</summary>
+    private sealed record FolderCall(string BrowseName, string DisplayName, string? ParentBrowseName);
     private sealed record VariableCall(string FolderBrowseName, string AttributeName, DriverAttributeInfo Info);
 
     private sealed class FakeBuilder : IAddressSpaceBuilder
@@ -47,7 +49,8 @@ public sealed class GalaxyDiscovererTests
         /// <returns>An IAddressSpaceBuilder scoped to the new folder.</returns>
         public IAddressSpaceBuilder Folder(string browseName, string displayName)
         {
-            Folders.Add(new FolderCall(browseName, displayName));
+            // Root-level folder — no parent.
+            Folders.Add(new FolderCall(browseName, displayName, ParentBrowseName: null));
             // Return a child scoped to this folder; nested folders inherit the parent reference.
             return new ChildBuilder(this, browseName);
         }
@@ -79,7 +82,8 @@ public sealed class GalaxyDiscovererTests
             /// <returns>An IAddressSpaceBuilder scoped to the new child folder.</returns>
             public IAddressSpaceBuilder Folder(string browseName, string displayName)
             {
-                parent.Folders.Add(new FolderCall(browseName, displayName));
+                // Nested folder — record the folder it was created under.
+                parent.Folders.Add(new FolderCall(browseName, displayName, ParentBrowseName: folderBrowseName));
                 return new ChildBuilder(parent, browseName);
             }
 
@@ -155,6 +159,22 @@ public sealed class GalaxyDiscovererTests
         return o;
     }
 
+    /// <summary>Builds a gobject with explicit id + parent id so nesting-by-parent can be asserted.</summary>
+    private static GalaxyObject Node(
+        int gobjectId, int parentGobjectId, string tagName,
+        string? containedName = null, params GalaxyAttribute[] attributes)
+    {
+        var o = new GalaxyObject
+        {
+            GobjectId = gobjectId,
+            ParentGobjectId = parentGobjectId,
+            TagName = tagName,
+            ContainedName = containedName ?? tagName,
+        };
+        o.Attributes.AddRange(attributes);
+        return o;
+    }
+
     /// <summary>Verifies that discovery creates one folder per object and one variable per attribute.</summary>
     [Fact]
     public async Task DiscoverAsync_BuildsOneFolderPerObject_AndOneVariablePerAttribute()
@@ -333,6 +353,101 @@ public sealed class GalaxyDiscovererTests
         builder.Variables.Count.ShouldBe(1);
     }
 
+    /// <summary>Child gobject's folder is created UNDER its parent's folder, not at the root.</summary>
+    [Fact]
+    public async Task Nests_child_folder_under_its_parent()
+    {
+        var src = new FakeHierarchySource([
+            Node(1, 0, "Parent", "parent", Attr("PV")),
+            Node(2, 1, "Child", "child", Attr("PV")),
+        ]);
+        var builder = new FakeBuilder();
+
+        await new GalaxyDiscoverer(src).DiscoverAsync(builder, CancellationToken.None);
+
+        var parent = builder.Folders.Single(f => f.BrowseName == "parent");
+        parent.ParentBrowseName.ShouldBeNull();
+        var child = builder.Folders.Single(f => f.BrowseName == "child");
+        child.ParentBrowseName.ShouldBe("parent");
+    }
+
+    /// <summary>Nesting is order-independent: child returned before its parent still nests correctly.</summary>
+    [Fact]
+    public async Task Is_order_independent_child_before_parent()
+    {
+        var src = new FakeHierarchySource([
+            Node(2, 1, "Child", "child", Attr("PV")), // child FIRST
+            Node(1, 0, "Parent", "parent", Attr("PV")),
+        ]);
+        var builder = new FakeBuilder();
+
+        await new GalaxyDiscoverer(src).DiscoverAsync(builder, CancellationToken.None);
+
+        var child = builder.Folders.Single(f => f.BrowseName == "child");
+        child.ParentBrowseName.ShouldBe("parent");
+    }
+
+    /// <summary>Both gobjects with parent=0 land flat at the driver root.</summary>
+    [Fact]
+    public async Task Degrades_to_flat_when_parent_is_zero()
+    {
+        var src = new FakeHierarchySource([
+            Node(1, 0, "A", "a", Attr("PV")),
+            Node(2, 0, "B", "b", Attr("PV")),
+        ]);
+        var builder = new FakeBuilder();
+
+        await new GalaxyDiscoverer(src).DiscoverAsync(builder, CancellationToken.None);
+
+        builder.Folders.Single(f => f.BrowseName == "a").ParentBrowseName.ShouldBeNull();
+        builder.Folders.Single(f => f.BrowseName == "b").ParentBrowseName.ShouldBeNull();
+    }
+
+    /// <summary>A child whose parent_gobject_id is not in the returned set degrades to the root.</summary>
+    [Fact]
+    public async Task Degrades_to_flat_when_parent_not_in_set()
+    {
+        var src = new FakeHierarchySource([
+            Node(2, 99, "Child", "child", Attr("PV")), // parent 99 absent
+        ]);
+        var builder = new FakeBuilder();
+
+        await new GalaxyDiscoverer(src).DiscoverAsync(builder, CancellationToken.None);
+
+        builder.Folders.Single(f => f.BrowseName == "child").ParentBrowseName.ShouldBeNull();
+    }
+
+    /// <summary>A self-referential parent (id == parent id) attaches to the root, never to itself.</summary>
+    [Fact]
+    public async Task Self_parent_attaches_to_root()
+    {
+        var src = new FakeHierarchySource([
+            Node(5, 5, "Selfie", "selfie", Attr("PV")),
+        ]);
+        var builder = new FakeBuilder();
+
+        await new GalaxyDiscoverer(src).DiscoverAsync(builder, CancellationToken.None);
+
+        builder.Folders.Single(f => f.BrowseName == "selfie").ParentBrowseName.ShouldBeNull();
+    }
+
+    /// <summary>A child object's attributes are added into the child's own folder, not the parent's.</summary>
+    [Fact]
+    public async Task Variables_land_in_their_owner_folder()
+    {
+        var src = new FakeHierarchySource([
+            Node(1, 0, "Parent", "parent", Attr("ParentPV")),
+            Node(2, 1, "Child", "child", Attr("ChildPV")),
+        ]);
+        var builder = new FakeBuilder();
+
+        await new GalaxyDiscoverer(src).DiscoverAsync(builder, CancellationToken.None);
+
+        builder.Variables.ShouldContain(v => v.FolderBrowseName == "parent" && v.AttributeName == "ParentPV");
+        builder.Variables.ShouldContain(v => v.FolderBrowseName == "child" && v.AttributeName == "ChildPV");
+        builder.Variables.ShouldNotContain(v => v.FolderBrowseName == "parent" && v.AttributeName == "ChildPV");
+    }
+
     /// <summary>Helper that exercises the internal ctor (test seam) without exposing it publicly.</summary>
     private sealed class GalaxyDriverHelper
     {