diff --git a/src/tooling/docs-assembler/Cli/RepositoryCommands.cs b/src/tooling/docs-assembler/Cli/RepositoryCommands.cs
index e68b62689..b2f674660 100644
--- a/src/tooling/docs-assembler/Cli/RepositoryCommands.cs
+++ b/src/tooling/docs-assembler/Cli/RepositoryCommands.cs
@@ -169,7 +169,7 @@ public async Task<int> BuildAll(
 		var navigation = new GlobalNavigation(assembleSources, navigationFile);
 
 		var pathProvider = new GlobalNavigationPathProvider(navigationFile, assembleSources, assembleContext);
-		var htmlWriter = new GlobalNavigationHtmlWriter(logFactory, navigation);
+		var htmlWriter = new GlobalNavigationHtmlWriter(logFactory, navigation, collector);
 		var legacyPageChecker = new LegacyPageChecker();
 		var historyMapper = new PageLegacyUrlMapper(legacyPageChecker, assembleSources.HistoryMappings);
 
diff --git a/src/tooling/docs-assembler/Navigation/GlobalNavigation.cs b/src/tooling/docs-assembler/Navigation/GlobalNavigation.cs
index f028616cd..82e98557d 100644
--- a/src/tooling/docs-assembler/Navigation/GlobalNavigation.cs
+++ b/src/tooling/docs-assembler/Navigation/GlobalNavigation.cs
@@ -47,7 +47,7 @@ public GlobalNavigation(AssembleSources assembleSources, GlobalNavigationFile na
 
 		var navigationIndex = 0;
 		var allNavigationItems = new HashSet<INavigationItem>();
-		UpdateParent(allNavigationItems, NavigationItems, null);
+		UpdateParent(allNavigationItems, NavigationItems, null, null);
 		UpdateNavigationIndex(NavigationItems, ref navigationIndex);
 		TopLevelItems = NavigationItems.OfType<TableOfContentsTree>().Where(t => !t.Hidden).ToList();
 		NavigationLookup = TopLevelItems.ToDictionary(kv => kv.Source, kv => kv);
@@ -64,9 +64,12 @@ public GlobalNavigation(AssembleSources assembleSources, GlobalNavigationFile na
 	private void UpdateParent(
 		HashSet<INavigationItem> allNavigationItems,
 		IReadOnlyCollection<INavigationItem> navigationItems,
-		INodeNavigationItem<INavigationModel, INavigationItem>? parent
+		INodeNavigationItem<INavigationModel, INavigationItem>? parent,
+		IRootNavigationItem<INavigationModel, INavigationItem>? topLevelNavigation
 	)
 	{
+		if (parent is IRootNavigationItem<INavigationModel, INavigationItem> tree)
+			topLevelNavigation ??= tree;
 		foreach (var item in navigationItems)
 		{
 			switch (item)
@@ -74,13 +77,17 @@ private void UpdateParent(
 				case FileNavigationItem fileNavigationItem:
 					if (parent is not null)
 						fileNavigationItem.Parent = parent;
+					if (topLevelNavigation is not null)
+						fileNavigationItem.Model.NavigationRoot = topLevelNavigation;
 					_ = allNavigationItems.Add(fileNavigationItem);
 					break;
 				case DocumentationGroup documentationGroup:
 					if (parent is not null)
 						documentationGroup.Parent = parent;
+					if (topLevelNavigation is not null)
+						documentationGroup.Index.NavigationRoot = topLevelNavigation;
 					_ = allNavigationItems.Add(documentationGroup);
-					UpdateParent(allNavigationItems, documentationGroup.NavigationItems, documentationGroup);
+					UpdateParent(allNavigationItems, documentationGroup.NavigationItems, documentationGroup, topLevelNavigation);
 					break;
 				default:
 					_navigationFile.EmitError($"Unhandled navigation item type: {item.GetType()}");
diff --git a/src/tooling/docs-assembler/Navigation/GlobalNavigationHtmlWriter.cs b/src/tooling/docs-assembler/Navigation/GlobalNavigationHtmlWriter.cs
index 9a65dd4ad..a69c99c16 100644
--- a/src/tooling/docs-assembler/Navigation/GlobalNavigationHtmlWriter.cs
+++ b/src/tooling/docs-assembler/Navigation/GlobalNavigationHtmlWriter.cs
@@ -3,13 +3,14 @@
 // See the LICENSE file in the project root for more information
 
 using System.Collections.Concurrent;
+using Elastic.Documentation.Diagnostics;
 using Elastic.Documentation.Site.Navigation;
 using Elastic.Markdown.IO.Navigation;
 using Microsoft.Extensions.Logging;
 
 namespace Documentation.Assembler.Navigation;
 
-public class GlobalNavigationHtmlWriter(ILoggerFactory logFactory, GlobalNavigation globalNavigation) : INavigationHtmlWriter
+public class GlobalNavigationHtmlWriter(ILoggerFactory logFactory, GlobalNavigation globalNavigation, DiagnosticsCollector collector) : INavigationHtmlWriter
 {
 	private readonly ILogger<Program> _logger = logFactory.CreateLogger<Program>();
 
@@ -17,34 +18,30 @@ public class GlobalNavigationHtmlWriter(ILoggerFactory logFactory, GlobalNavigat
 
 	public async Task<NavigationRenderResult> RenderNavigation(IRootNavigationItem<INavigationModel, INavigationItem> currentRootNavigation, int maxLevel, Cancel ctx = default)
 	{
-		INodeNavigationItem<INavigationModel, INavigationItem> lastParentBeforeRoot = currentRootNavigation;
-		INodeNavigationItem<INavigationModel, INavigationItem> parent = currentRootNavigation;
-		while (parent.Parent is not null)
-		{
-			lastParentBeforeRoot = parent;
-			parent = parent.Parent;
-		}
-		if (_renderedNavigationCache.TryGetValue((lastParentBeforeRoot.Id, maxLevel), out var html))
+		if (currentRootNavigation.Parent is not null && currentRootNavigation.Parent.Depth != 0)
+			collector.EmitGlobalError($"Passed root is not actually a top level navigation item {currentRootNavigation.NavigationTitle} ({currentRootNavigation.Id}) in {currentRootNavigation.Url}");
+
+		if (_renderedNavigationCache.TryGetValue((currentRootNavigation.Id, maxLevel), out var html))
 		{
 			return new NavigationRenderResult
 			{
 				Html = html,
-				Id = lastParentBeforeRoot.Id
+				Id = currentRootNavigation.Id
 			};
 		}
 
-		_logger.LogInformation("Rendering navigation for {NavigationTitle} ({Id})", lastParentBeforeRoot.NavigationTitle, lastParentBeforeRoot.Id);
+		_logger.LogInformation("Rendering navigation for {NavigationTitle} ({Id})", currentRootNavigation.NavigationTitle, currentRootNavigation.Id);
 
-		if (lastParentBeforeRoot is not DocumentationGroup group)
+		if (currentRootNavigation is not DocumentationGroup group)
 			return NavigationRenderResult.Empty;
 
 		var model = CreateNavigationModel(group, maxLevel);
 		html = await ((INavigationHtmlWriter)this).Render(model, ctx);
-		_renderedNavigationCache[(lastParentBeforeRoot.Id, maxLevel)] = html;
+		_renderedNavigationCache[(currentRootNavigation.Id, maxLevel)] = html;
 		return new NavigationRenderResult
 		{
 			Html = html,
-			Id = lastParentBeforeRoot.Id
+			Id = currentRootNavigation.Id
 		};
 	}