From 293a466d22780a65c8cfcd177e84c5b55cfffa29 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Fri, 21 Nov 2025 12:29:25 +0100
Subject: [PATCH 01/13] First version of fix. Dysnamic JS roots were entering
 `GetMarkerKey` without initializing the manager,

---
 .../Server/src/Circuits/RemoteRenderer.cs     | 10 +++++++---
 .../src/Rendering/WebAssemblyRenderer.cs      | 11 ++++++++---
 .../E2ETest/Tests/StatePersistenceTest.cs     | 13 +++++++++++++
 .../persistent-state-js-root-component.html   | 16 ++++++++++++++++
 .../RazorComponentEndpointsStartup.cs         |  2 ++
 .../CounterWithPersistentState.razor          | 19 +++++++++++++++++++
 6 files changed, 65 insertions(+), 6 deletions(-)
 create mode 100644 src/Components/test/testassets/BasicTestApp/wwwroot/persistent-state-js-root-component.html
 create mode 100644 src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor

diff --git a/src/Components/Server/src/Circuits/RemoteRenderer.cs b/src/Components/Server/src/Circuits/RemoteRenderer.cs
index 8e161697abdb..654829189bb2 100644
--- a/src/Components/Server/src/Circuits/RemoteRenderer.cs
+++ b/src/Components/Server/src/Circuits/RemoteRenderer.cs
@@ -321,9 +321,13 @@ protected override ComponentState CreateComponentState(int componentId, ICompone
 
     internal ComponentMarkerKey GetMarkerKey(RemoteComponentState remoteComponentState)
     {
-        return remoteComponentState.ParentComponentState != null ?
-            default :
-            _webRootComponentManager!.GetRootComponentKey(remoteComponentState.ComponentId);
+        if (remoteComponentState.ParentComponentState != null)
+        {
+            return default;
+        }
+
+        var webRootComponentManager = _webRootComponentManager ?? GetOrCreateWebRootComponentManager();
+        return webRootComponentManager.GetRootComponentKey(remoteComponentState.ComponentId);
     }
 
     private void ProcessPendingBatch(string? errorMessageOrNull, UnacknowledgedRenderBatch entry)
diff --git a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
index 242e28ed7ba2..f280d7b0d9aa 100644
--- a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
+++ b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
@@ -224,9 +224,14 @@ protected override ComponentState CreateComponentState(int componentId, ICompone
 
     internal ComponentMarkerKey GetMarkerKey(WebAssemblyComponentState webAssemblyComponentState)
     {
-        return webAssemblyComponentState.ParentComponentState != null ?
-            default :
-            _webRootComponentManager!.GetRootComponentKey(webAssemblyComponentState.ComponentId);
+        if (webAssemblyComponentState.ParentComponentState != null)
+        {
+            return default;
+        }
+
+        var webRootComponentManager = _webRootComponentManager ?? GetOrCreateWebRootComponentManager();
+
+        return webRootComponentManager.GetRootComponentKey(webAssemblyComponentState.ComponentId);
     }
 
     private static partial class Log
diff --git a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
index 007c7ce5de16..62bc170cf162 100644
--- a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
+++ b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Linq;
 using Components.TestServer.RazorComponents;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure.ServerFixtures;
@@ -355,6 +356,18 @@ private void RenderComponentsWithPersistentStateAndValidate(
             interactiveRuntime: interactiveRuntime);
     }
 
+    [Fact]
+    public void JsAddedPersistentStateRootComponentDoesNotTriggerCircuitError()
+    {
+        Navigate("subdir/persistent-state-js-root-component.html");
+
+        Browser.Equal("Counter", () => Browser.Exists(By.TagName("h1")).Text);
+        Browser.Equal("Current count: 0", () => Browser.Exists(By.CssSelector("p[role='status']")).Text);
+
+        Browser.Click(By.CssSelector("button.btn-primary"));
+        Browser.Equal("Current count: 1", () => Browser.Exists(By.CssSelector("p[role='status']")).Text);
+    }
+
     private void AssertPageState(
         string mode,
         string renderMode,
diff --git a/src/Components/test/testassets/BasicTestApp/wwwroot/persistent-state-js-root-component.html b/src/Components/test/testassets/BasicTestApp/wwwroot/persistent-state-js-root-component.html
new file mode 100644
index 000000000000..180c4ae21dc1
--- /dev/null
+++ b/src/Components/test/testassets/BasicTestApp/wwwroot/persistent-state-js-root-component.html
@@ -0,0 +1,16 @@
+<html>
+<head>
+  <base href="/subdir/" />
+</head>
+<body>
+  <div id="app">
+  </div>
+
+  <script src="_framework/blazor.server.js" autostart="false"></script>
+  <script>
+    Blazor.start().then(() => {
+      Blazor.rootComponents.add(document.getElementById("app"), "persistent-state-counter", {});
+    });
+  </script>
+</body>
+</html>
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
index 861e0fbdf288..1eca1342bb5f 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
@@ -7,6 +7,7 @@
 using System.Web;
 using Components.TestServer.RazorComponents;
 using Components.TestServer.RazorComponents.Pages.Forms;
+using Components.TestServer.RazorComponents.Pages.PersistentState;
 using Components.TestServer.Services;
 using Microsoft.AspNetCore.Components;
 using Microsoft.AspNetCore.Components.Server.Circuits;
@@ -50,6 +51,7 @@ public void ConfigureServices(IServiceCollection services)
                     options.DisconnectedCircuitMaxRetained = 0;
                     options.DetailedErrors = true;
                 }
+                options.RootComponents.RegisterForJavaScript<CounterWithPersistentState>("persistent-state-counter");
             })
             .AddAuthenticationStateSerialization(options =>
             {
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor
new file mode 100644
index 000000000000..574bcdabc595
--- /dev/null
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor
@@ -0,0 +1,19 @@
+@page "/persistent-state/counter"
+@rendermode RenderMode.InteractiveServer
+
+<PageTitle>Counter</PageTitle>
+
+<h1>Counter</h1>
+
+<p role="status">Current count: @currentCount</p>
+
+<button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
+
+@code {
+    [PersistentState] public int currentCount {get; set;}
+
+    private void IncrementCount()
+    {
+        currentCount++;
+    }
+}

From 5d503c2399e21cf071d3fe6522710ccb4a3a1e49 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Fri, 21 Nov 2025 12:55:36 +0100
Subject: [PATCH 02/13] Rename to clarify.

---
 src/Components/test/E2ETest/Tests/StatePersistenceTest.cs     | 4 ++--
 ...tent-state-js-root-component.html => dynamic-js-root.html} | 2 +-
 .../Components.TestServer/RazorComponentEndpointsStartup.cs   | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)
 rename src/Components/test/testassets/BasicTestApp/wwwroot/{persistent-state-js-root-component.html => dynamic-js-root.html} (90%)

diff --git a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
index 62bc170cf162..591c8be10b03 100644
--- a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
+++ b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
@@ -357,9 +357,9 @@ private void RenderComponentsWithPersistentStateAndValidate(
     }
 
     [Fact]
-    public void JsAddedPersistentStateRootComponentDoesNotTriggerCircuitError()
+    public void PersistentStateIsSupportedInDynamicJSRoots()
     {
-        Navigate("subdir/persistent-state-js-root-component.html");
+        Navigate("subdir/dynamic-js-root.html");
 
         Browser.Equal("Counter", () => Browser.Exists(By.TagName("h1")).Text);
         Browser.Equal("Current count: 0", () => Browser.Exists(By.CssSelector("p[role='status']")).Text);
diff --git a/src/Components/test/testassets/BasicTestApp/wwwroot/persistent-state-js-root-component.html b/src/Components/test/testassets/BasicTestApp/wwwroot/dynamic-js-root.html
similarity index 90%
rename from src/Components/test/testassets/BasicTestApp/wwwroot/persistent-state-js-root-component.html
rename to src/Components/test/testassets/BasicTestApp/wwwroot/dynamic-js-root.html
index 180c4ae21dc1..284a4d151a11 100644
--- a/src/Components/test/testassets/BasicTestApp/wwwroot/persistent-state-js-root-component.html
+++ b/src/Components/test/testassets/BasicTestApp/wwwroot/dynamic-js-root.html
@@ -9,7 +9,7 @@
   <script src="_framework/blazor.server.js" autostart="false"></script>
   <script>
     Blazor.start().then(() => {
-      Blazor.rootComponents.add(document.getElementById("app"), "persistent-state-counter", {});
+      Blazor.rootComponents.add(document.getElementById("app"), "dynamic-js-root-counter", {});
     });
   </script>
 </body>
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
index 1eca1342bb5f..eaf3694878ee 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
@@ -51,7 +51,7 @@ public void ConfigureServices(IServiceCollection services)
                     options.DisconnectedCircuitMaxRetained = 0;
                     options.DetailedErrors = true;
                 }
-                options.RootComponents.RegisterForJavaScript<CounterWithPersistentState>("persistent-state-counter");
+                options.RootComponents.RegisterForJavaScript<CounterWithPersistentState>("dynamic-js-root-counter");
             })
             .AddAuthenticationStateSerialization(options =>
             {

From 38b2f4f66c157e42d57225233d2e4a88f2cbe05d Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <32700855+ilonatommy@users.noreply.github.com>
Date: Fri, 21 Nov 2025 12:56:28 +0100
Subject: [PATCH 03/13] Update
 src/Components/test/E2ETest/Tests/StatePersistenceTest.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 src/Components/test/E2ETest/Tests/StatePersistenceTest.cs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
index 591c8be10b03..6c35ae0c9a8d 100644
--- a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
+++ b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
@@ -1,7 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Linq;
 using Components.TestServer.RazorComponents;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure;
 using Microsoft.AspNetCore.Components.E2ETest.Infrastructure.ServerFixtures;

From d75a79499186b5c79de71df3ac1fe59a6f11b122 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <32700855+ilonatommy@users.noreply.github.com>
Date: Fri, 21 Nov 2025 12:56:36 +0100
Subject: [PATCH 04/13] Update
 src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 .../Pages/PersistentState/CounterWithPersistentState.razor      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor
index 574bcdabc595..3227701f2040 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor
@@ -10,7 +10,7 @@
 <button class="btn btn-primary" @onclick="IncrementCount">Click me</button>
 
 @code {
-    [PersistentState] public int currentCount {get; set;}
+    [PersistentState] public int currentCount { get; set; }
 
     private void IncrementCount()
     {

From 6af73db4f428ea4d99bc29d0ffc91185d09566c0 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Fri, 21 Nov 2025 13:30:47 +0100
Subject: [PATCH 05/13] Change approach: do not change `GetMarkerKey` but make
 sure the manager is initialized on time.

---
 .../Server/src/Circuits/CircuitJSComponentInterop.cs | 12 ++++++++++++
 src/Components/Server/src/Circuits/RemoteRenderer.cs |  4 ++--
 .../WebAssembly/src/Rendering/WebAssemblyRenderer.cs |  5 ++---
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/Components/Server/src/Circuits/CircuitJSComponentInterop.cs b/src/Components/Server/src/Circuits/CircuitJSComponentInterop.cs
index 1896429673e7..ac1e1421c213 100644
--- a/src/Components/Server/src/Circuits/CircuitJSComponentInterop.cs
+++ b/src/Components/Server/src/Circuits/CircuitJSComponentInterop.cs
@@ -9,6 +9,7 @@ internal sealed class CircuitJSComponentInterop : JSComponentInterop
 {
     private readonly CircuitOptions _circuitOptions;
     private int _jsRootComponentCount;
+    private RemoteRenderer? _renderer;
 
     internal CircuitJSComponentInterop(CircuitOptions circuitOptions)
         : base(circuitOptions.RootComponents.JSComponents)
@@ -16,6 +17,11 @@ internal CircuitJSComponentInterop(CircuitOptions circuitOptions)
         _circuitOptions = circuitOptions;
     }
 
+    internal void SetRenderer(RemoteRenderer renderer)
+    {
+        _renderer = renderer;
+    }
+
     protected override int AddRootComponent(string identifier, string domElementSelector)
     {
         if (_jsRootComponentCount >= _circuitOptions.RootComponents.MaxJSRootComponents)
@@ -23,6 +29,12 @@ protected override int AddRootComponent(string identifier, string domElementSele
             throw new InvalidOperationException($"Cannot add further JS root components because the configured limit of {_circuitOptions.RootComponents.MaxJSRootComponents} has been reached.");
         }
 
+        if (_renderer is null)
+        {
+            throw new InvalidOperationException("Renderer has not been set. Ensure SetRenderer is called before adding root components.");
+        }
+        _renderer.GetOrCreateWebRootComponentManager();
+
         var id = base.AddRootComponent(identifier, domElementSelector);
         _jsRootComponentCount++;
         return id;
diff --git a/src/Components/Server/src/Circuits/RemoteRenderer.cs b/src/Components/Server/src/Circuits/RemoteRenderer.cs
index 654829189bb2..13f212533eb3 100644
--- a/src/Components/Server/src/Circuits/RemoteRenderer.cs
+++ b/src/Components/Server/src/Circuits/RemoteRenderer.cs
@@ -50,6 +50,7 @@ public RemoteRenderer(
         ResourceAssetCollection resourceCollection = null)
         : base(serviceProvider, loggerFactory, jsRuntime.ReadJsonSerializerOptions(), jsComponentInterop)
     {
+        jsComponentInterop.SetRenderer(this);
         _client = client;
         _options = options;
         _serverComponentDeserializer = serverComponentDeserializer;
@@ -326,8 +327,7 @@ internal ComponentMarkerKey GetMarkerKey(RemoteComponentState remoteComponentSta
             return default;
         }
 
-        var webRootComponentManager = _webRootComponentManager ?? GetOrCreateWebRootComponentManager();
-        return webRootComponentManager.GetRootComponentKey(remoteComponentState.ComponentId);
+        return _webRootComponentManager!.GetRootComponentKey(remoteComponentState.ComponentId);
     }
 
     private void ProcessPendingBatch(string? errorMessageOrNull, UnacknowledgedRenderBatch entry)
diff --git a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
index f280d7b0d9aa..68128739eb33 100644
--- a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
+++ b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
@@ -46,6 +46,7 @@ public WebAssemblyRenderer(IServiceProvider serviceProvider, ResourceAssetCollec
 
         ElementReferenceContext = DefaultWebAssemblyJSRuntime.Instance.ElementReferenceContext;
         DefaultWebAssemblyJSRuntime.Instance.OnUpdateRootComponents += OnUpdateRootComponents;
+        GetOrCreateWebRootComponentManager();
     }
 
     [UnconditionalSuppressMessage("Trimming", "IL2072", Justification = "These are root components which belong to the user and are in assemblies that don't get trimmed.")]
@@ -229,9 +230,7 @@ internal ComponentMarkerKey GetMarkerKey(WebAssemblyComponentState webAssemblyCo
             return default;
         }
 
-        var webRootComponentManager = _webRootComponentManager ?? GetOrCreateWebRootComponentManager();
-
-        return webRootComponentManager.GetRootComponentKey(webAssemblyComponentState.ComponentId);
+        return _webRootComponentManager!.GetRootComponentKey(webAssemblyComponentState.ComponentId);
     }
 
     private static partial class Log

From 3a8cfbd71c403777490fa80c5144ef3687268091 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Fri, 21 Nov 2025 13:32:24 +0100
Subject: [PATCH 06/13] Cleanup.

---
 src/Components/Server/src/Circuits/RemoteRenderer.cs     | 9 +++------
 .../WebAssembly/src/Rendering/WebAssemblyRenderer.cs     | 9 +++------
 2 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/src/Components/Server/src/Circuits/RemoteRenderer.cs b/src/Components/Server/src/Circuits/RemoteRenderer.cs
index 13f212533eb3..05f3687ccb21 100644
--- a/src/Components/Server/src/Circuits/RemoteRenderer.cs
+++ b/src/Components/Server/src/Circuits/RemoteRenderer.cs
@@ -322,12 +322,9 @@ protected override ComponentState CreateComponentState(int componentId, ICompone
 
     internal ComponentMarkerKey GetMarkerKey(RemoteComponentState remoteComponentState)
     {
-        if (remoteComponentState.ParentComponentState != null)
-        {
-            return default;
-        }
-
-        return _webRootComponentManager!.GetRootComponentKey(remoteComponentState.ComponentId);
+        return remoteComponentState.ParentComponentState != null ?
+            default :
+            _webRootComponentManager!.GetRootComponentKey(remoteComponentState.ComponentId);
     }
 
     private void ProcessPendingBatch(string? errorMessageOrNull, UnacknowledgedRenderBatch entry)
diff --git a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
index 68128739eb33..f528035661ba 100644
--- a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
+++ b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
@@ -225,12 +225,9 @@ protected override ComponentState CreateComponentState(int componentId, ICompone
 
     internal ComponentMarkerKey GetMarkerKey(WebAssemblyComponentState webAssemblyComponentState)
     {
-        if (webAssemblyComponentState.ParentComponentState != null)
-        {
-            return default;
-        }
-
-        return _webRootComponentManager!.GetRootComponentKey(webAssemblyComponentState.ComponentId);
+        return webAssemblyComponentState.ParentComponentState != null ?
+            default :
+            _webRootComponentManager!.GetRootComponentKey(webAssemblyComponentState.ComponentId);
     }
 
     private static partial class Log

From 482ee24ebf303e7ce5fa5bcba08b210989431c3a Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Fri, 21 Nov 2025 18:15:38 +0100
Subject: [PATCH 07/13] Add test for WebAssembly.

---
 .../E2ETest/Tests/StatePersistenceTest.cs     |  8 ++++---
 .../RazorComponentEndpointsStartup.cs         |  2 +-
 .../Pages/CounterWithPersistentState.razor    | 23 +++++++++++++++++++
 .../wwwroot/dynamic-js-root.html              |  0
 .../ComponentWithPersistentState.razor}       |  3 ---
 5 files changed, 29 insertions(+), 7 deletions(-)
 create mode 100644 src/Components/test/testassets/Components.WasmMinimal/Pages/CounterWithPersistentState.razor
 rename src/Components/test/testassets/{BasicTestApp => Components.WasmMinimal}/wwwroot/dynamic-js-root.html (100%)
 rename src/Components/test/testassets/{Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor => TestContentPackage/PersistentComponents/ComponentWithPersistentState.razor} (80%)

diff --git a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
index 6c35ae0c9a8d..d342d4d519ca 100644
--- a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
+++ b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
@@ -355,10 +355,12 @@ private void RenderComponentsWithPersistentStateAndValidate(
             interactiveRuntime: interactiveRuntime);
     }
 
-    [Fact]
-    public void PersistentStateIsSupportedInDynamicJSRoots()
+    [Theory]
+    [InlineData("ServerNonPrerendered")]
+    [InlineData("WebAssemblyNonPrerendered")]
+    public void PersistentStateIsSupportedInDynamicJSRoots(string renderMode)
     {
-        Navigate("subdir/dynamic-js-root.html");
+        Navigate($"subdir/WasmMinimal/dynamic-js-root.html?renderMode={renderMode}");
 
         Browser.Equal("Counter", () => Browser.Exists(By.TagName("h1")).Text);
         Browser.Equal("Current count: 0", () => Browser.Exists(By.CssSelector("p[role='status']")).Text);
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
index eaf3694878ee..13e457f49995 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
@@ -51,7 +51,7 @@ public void ConfigureServices(IServiceCollection services)
                     options.DisconnectedCircuitMaxRetained = 0;
                     options.DetailedErrors = true;
                 }
-                options.RootComponents.RegisterForJavaScript<CounterWithPersistentState>("dynamic-js-root-counter");
+                options.RootComponents.RegisterForJavaScript<TestContentPackage.PersistentComponents.ComponentWithPersistentState>("dynamic-js-root-counter");
             })
             .AddAuthenticationStateSerialization(options =>
             {
diff --git a/src/Components/test/testassets/Components.WasmMinimal/Pages/CounterWithPersistentState.razor b/src/Components/test/testassets/Components.WasmMinimal/Pages/CounterWithPersistentState.razor
new file mode 100644
index 000000000000..f44a4a80f1ac
--- /dev/null
+++ b/src/Components/test/testassets/Components.WasmMinimal/Pages/CounterWithPersistentState.razor
@@ -0,0 +1,23 @@
+@page "/persistent-state/counter"
+
+<TestContentPackage.PersistentComponents.ComponentWithPersistentState @rendermode="@RenderModeHelper.GetRenderMode(_renderMode)"/>
+
+
+@code{
+    [Parameter, SupplyParameterFromQuery(Name = "renderMode")]
+    public string? RenderModeStr { get; set; }
+
+    private RenderModeId _renderMode;
+
+    protected override void OnInitialized()
+    {
+        if (!string.IsNullOrEmpty(RenderModeStr))
+        {
+            _renderMode = RenderModeHelper.ParseRenderMode(RenderModeStr);
+        }
+        else
+        {
+            throw new ArgumentException("RenderModeStr cannot be null or empty", nameof(RenderModeStr));
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/Components/test/testassets/BasicTestApp/wwwroot/dynamic-js-root.html b/src/Components/test/testassets/Components.WasmMinimal/wwwroot/dynamic-js-root.html
similarity index 100%
rename from src/Components/test/testassets/BasicTestApp/wwwroot/dynamic-js-root.html
rename to src/Components/test/testassets/Components.WasmMinimal/wwwroot/dynamic-js-root.html
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor b/src/Components/test/testassets/TestContentPackage/PersistentComponents/ComponentWithPersistentState.razor
similarity index 80%
rename from src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor
rename to src/Components/test/testassets/TestContentPackage/PersistentComponents/ComponentWithPersistentState.razor
index 3227701f2040..d26ae13fc390 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponents/Pages/PersistentState/CounterWithPersistentState.razor
+++ b/src/Components/test/testassets/TestContentPackage/PersistentComponents/ComponentWithPersistentState.razor
@@ -1,6 +1,3 @@
-@page "/persistent-state/counter"
-@rendermode RenderMode.InteractiveServer
-
 <PageTitle>Counter</PageTitle>
 
 <h1>Counter</h1>

From 3ea48d7385ce773941bfa010b499e1cae704e532 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Fri, 21 Nov 2025 18:26:42 +0100
Subject: [PATCH 08/13] Redunadnt because wasm rnderer already has
 OnUpdateRootComponents handle

---
 .../WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
index f528035661ba..242e28ed7ba2 100644
--- a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
+++ b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
@@ -46,7 +46,6 @@ public WebAssemblyRenderer(IServiceProvider serviceProvider, ResourceAssetCollec
 
         ElementReferenceContext = DefaultWebAssemblyJSRuntime.Instance.ElementReferenceContext;
         DefaultWebAssemblyJSRuntime.Instance.OnUpdateRootComponents += OnUpdateRootComponents;
-        GetOrCreateWebRootComponentManager();
     }
 
     [UnconditionalSuppressMessage("Trimming", "IL2072", Justification = "These are root components which belong to the user and are in assemblies that don't get trimmed.")]

From dd9777f66bf88a64158ad9b8554da771b98e05cc Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Mon, 24 Nov 2025 15:00:24 +0100
Subject: [PATCH 09/13] Revert changes to the framework.

---
 .../Server/src/Circuits/CircuitJSComponentInterop.cs | 12 ------------
 src/Components/Server/src/Circuits/RemoteRenderer.cs |  1 -
 2 files changed, 13 deletions(-)

diff --git a/src/Components/Server/src/Circuits/CircuitJSComponentInterop.cs b/src/Components/Server/src/Circuits/CircuitJSComponentInterop.cs
index ac1e1421c213..1896429673e7 100644
--- a/src/Components/Server/src/Circuits/CircuitJSComponentInterop.cs
+++ b/src/Components/Server/src/Circuits/CircuitJSComponentInterop.cs
@@ -9,7 +9,6 @@ internal sealed class CircuitJSComponentInterop : JSComponentInterop
 {
     private readonly CircuitOptions _circuitOptions;
     private int _jsRootComponentCount;
-    private RemoteRenderer? _renderer;
 
     internal CircuitJSComponentInterop(CircuitOptions circuitOptions)
         : base(circuitOptions.RootComponents.JSComponents)
@@ -17,11 +16,6 @@ internal CircuitJSComponentInterop(CircuitOptions circuitOptions)
         _circuitOptions = circuitOptions;
     }
 
-    internal void SetRenderer(RemoteRenderer renderer)
-    {
-        _renderer = renderer;
-    }
-
     protected override int AddRootComponent(string identifier, string domElementSelector)
     {
         if (_jsRootComponentCount >= _circuitOptions.RootComponents.MaxJSRootComponents)
@@ -29,12 +23,6 @@ protected override int AddRootComponent(string identifier, string domElementSele
             throw new InvalidOperationException($"Cannot add further JS root components because the configured limit of {_circuitOptions.RootComponents.MaxJSRootComponents} has been reached.");
         }
 
-        if (_renderer is null)
-        {
-            throw new InvalidOperationException("Renderer has not been set. Ensure SetRenderer is called before adding root components.");
-        }
-        _renderer.GetOrCreateWebRootComponentManager();
-
         var id = base.AddRootComponent(identifier, domElementSelector);
         _jsRootComponentCount++;
         return id;
diff --git a/src/Components/Server/src/Circuits/RemoteRenderer.cs b/src/Components/Server/src/Circuits/RemoteRenderer.cs
index 05f3687ccb21..8e161697abdb 100644
--- a/src/Components/Server/src/Circuits/RemoteRenderer.cs
+++ b/src/Components/Server/src/Circuits/RemoteRenderer.cs
@@ -50,7 +50,6 @@ public RemoteRenderer(
         ResourceAssetCollection resourceCollection = null)
         : base(serviceProvider, loggerFactory, jsRuntime.ReadJsonSerializerOptions(), jsComponentInterop)
     {
-        jsComponentInterop.SetRenderer(this);
         _client = client;
         _options = options;
         _serverComponentDeserializer = serverComponentDeserializer;

From cd8cc1e7c8260989ab22d686a4f965f1cdbb1d93 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Tue, 25 Nov 2025 11:01:25 +0100
Subject: [PATCH 10/13] JS root tests do not interfre with other tests now.

---
 .../Tests/StatePersistanceJSRootTest.cs       | 42 +++++++++++++++++++
 .../E2ETest/Tests/StatePersistenceTest.cs     | 14 -------
 .../Components.TestServer/Program.cs          |  3 +-
 .../RazorComponentEndpointsStartup.cs         |  5 ++-
 4 files changed, 48 insertions(+), 16 deletions(-)
 create mode 100644 src/Components/test/E2ETest/Tests/StatePersistanceJSRootTest.cs

diff --git a/src/Components/test/E2ETest/Tests/StatePersistanceJSRootTest.cs b/src/Components/test/E2ETest/Tests/StatePersistanceJSRootTest.cs
new file mode 100644
index 000000000000..9c554fccab79
--- /dev/null
+++ b/src/Components/test/E2ETest/Tests/StatePersistanceJSRootTest.cs
@@ -0,0 +1,42 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Components.TestServer.RazorComponents;
+using Microsoft.AspNetCore.Components.E2ETest.Infrastructure;
+using Microsoft.AspNetCore.Components.E2ETest.Infrastructure.ServerFixtures;
+using Microsoft.AspNetCore.Components.E2ETests.ServerRenderingTests;
+using Microsoft.AspNetCore.Components.Web;
+using Microsoft.AspNetCore.E2ETesting;
+using OpenQA.Selenium;
+using TestServer;
+using Xunit.Abstractions;
+
+namespace Microsoft.AspNetCore.Components.E2ETests.Tests;
+
+// These tests are for Blazor Web implementation
+// For Blazor Server and Webassembly, check SaveStateTest.cs
+public class StatePersistanceJSRootTest : ServerTestBase<BasicTestAppServerSiteFixture<RazorComponentEndpointsStartup<App>>>
+{
+    public StatePersistanceJSRootTest(
+        BrowserFixture browserFixture,
+        BasicTestAppServerSiteFixture<RazorComponentEndpointsStartup<App>> serverFixture,
+        ITestOutputHelper output)
+        : base(browserFixture, serverFixture, output)
+    {
+        serverFixture.AdditionalArguments.AddRange("--RegisterDynamicJSRootComponent", "true");
+    }
+
+    [Theory]
+    [InlineData("ServerNonPrerendered")]
+    [InlineData("WebAssemblyNonPrerendered")]
+    public void PersistentStateIsSupportedInDynamicJSRoots(string renderMode)
+    {
+        Navigate($"subdir/WasmMinimal/dynamic-js-root.html?renderMode={renderMode}");
+
+        Browser.Equal("Counter", () => Browser.Exists(By.TagName("h1")).Text);
+        Browser.Equal("Current count: 0", () => Browser.Exists(By.CssSelector("p[role='status']")).Text);
+
+        Browser.Click(By.CssSelector("button.btn-primary"));
+        Browser.Equal("Current count: 1", () => Browser.Exists(By.CssSelector("p[role='status']")).Text);
+    }
+}
diff --git a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
index d342d4d519ca..007c7ce5de16 100644
--- a/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
+++ b/src/Components/test/E2ETest/Tests/StatePersistenceTest.cs
@@ -355,20 +355,6 @@ private void RenderComponentsWithPersistentStateAndValidate(
             interactiveRuntime: interactiveRuntime);
     }
 
-    [Theory]
-    [InlineData("ServerNonPrerendered")]
-    [InlineData("WebAssemblyNonPrerendered")]
-    public void PersistentStateIsSupportedInDynamicJSRoots(string renderMode)
-    {
-        Navigate($"subdir/WasmMinimal/dynamic-js-root.html?renderMode={renderMode}");
-
-        Browser.Equal("Counter", () => Browser.Exists(By.TagName("h1")).Text);
-        Browser.Equal("Current count: 0", () => Browser.Exists(By.CssSelector("p[role='status']")).Text);
-
-        Browser.Click(By.CssSelector("button.btn-primary"));
-        Browser.Equal("Current count: 1", () => Browser.Exists(By.CssSelector("p[role='status']")).Text);
-    }
-
     private void AssertPageState(
         string mode,
         string renderMode,
diff --git a/src/Components/test/testassets/Components.TestServer/Program.cs b/src/Components/test/testassets/Components.TestServer/Program.cs
index 568f809454a7..58e39b5d11c8 100644
--- a/src/Components/test/testassets/Components.TestServer/Program.cs
+++ b/src/Components/test/testassets/Components.TestServer/Program.cs
@@ -23,7 +23,8 @@ public static async Task Main(string[] args)
             ["Server authentication"] = (BuildWebHost<ServerAuthenticationStartup>(CreateAdditionalArgs(args)), "/subdir"),
             ["CORS (WASM)"] = (BuildWebHost<CorsStartup>(CreateAdditionalArgs(args)), "/subdir"),
             ["Prerendering (Server-side)"] = (BuildWebHost<PrerenderedStartup>(CreateAdditionalArgs(args)), "/prerendered"),
-            ["Razor Component Endpoints"] = (BuildWebHost<RazorComponentEndpointsStartup<Components.TestServer.RazorComponents.App>>(CreateAdditionalArgs(args)), "/subdir"),
+            ["Razor Component Endpoints"] = (BuildWebHost<RazorComponentEndpointsStartup<App>>(CreateAdditionalArgs(args)), "/subdir"),
+            ["Razor Component Endpoints with JS Root Component"] = (BuildWebHost<RazorComponentEndpointsStartup<App>>(CreateAdditionalArgs([.. args, "--RegisterDynamicJSRootComponent", "true"])), "/subdir"),
             ["Deferred component content (Server-side)"] = (BuildWebHost<DeferredComponentContentStartup>(CreateAdditionalArgs(args)), "/deferred-component-content"),
             ["Locked navigation (Server-side)"] = (BuildWebHost<LockedNavigationStartup>(CreateAdditionalArgs(args)), "/locked-navigation"),
             ["Client-side with fallback"] = (BuildWebHost<StartupWithMapFallbackToClientSideBlazor>(CreateAdditionalArgs(args)), "/fallback"),
diff --git a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
index 13e457f49995..986d4c391fd0 100644
--- a/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
+++ b/src/Components/test/testassets/Components.TestServer/RazorComponentEndpointsStartup.cs
@@ -51,7 +51,10 @@ public void ConfigureServices(IServiceCollection services)
                     options.DisconnectedCircuitMaxRetained = 0;
                     options.DetailedErrors = true;
                 }
-                options.RootComponents.RegisterForJavaScript<TestContentPackage.PersistentComponents.ComponentWithPersistentState>("dynamic-js-root-counter");
+                if (Configuration.GetValue<bool>("RegisterDynamicJSRootComponent"))
+                {
+                    options.RootComponents.RegisterForJavaScript<TestContentPackage.PersistentComponents.ComponentWithPersistentState>("dynamic-js-root-counter");
+                }
             })
             .AddAuthenticationStateSerialization(options =>
             {

From fb3717edf9e74c00406a3ffbb46d91f77b235504 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Tue, 25 Nov 2025 11:16:05 +0100
Subject: [PATCH 11/13] Simplest fix.

---
 src/Components/Server/src/Circuits/RemoteRenderer.cs  | 10 +++++++---
 .../WebAssembly/src/Rendering/WebAssemblyRenderer.cs  | 11 ++++++++---
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/Components/Server/src/Circuits/RemoteRenderer.cs b/src/Components/Server/src/Circuits/RemoteRenderer.cs
index 8e161697abdb..654829189bb2 100644
--- a/src/Components/Server/src/Circuits/RemoteRenderer.cs
+++ b/src/Components/Server/src/Circuits/RemoteRenderer.cs
@@ -321,9 +321,13 @@ protected override ComponentState CreateComponentState(int componentId, ICompone
 
     internal ComponentMarkerKey GetMarkerKey(RemoteComponentState remoteComponentState)
     {
-        return remoteComponentState.ParentComponentState != null ?
-            default :
-            _webRootComponentManager!.GetRootComponentKey(remoteComponentState.ComponentId);
+        if (remoteComponentState.ParentComponentState != null)
+        {
+            return default;
+        }
+
+        var webRootComponentManager = _webRootComponentManager ?? GetOrCreateWebRootComponentManager();
+        return webRootComponentManager.GetRootComponentKey(remoteComponentState.ComponentId);
     }
 
     private void ProcessPendingBatch(string? errorMessageOrNull, UnacknowledgedRenderBatch entry)
diff --git a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
index 242e28ed7ba2..f280d7b0d9aa 100644
--- a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
+++ b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
@@ -224,9 +224,14 @@ protected override ComponentState CreateComponentState(int componentId, ICompone
 
     internal ComponentMarkerKey GetMarkerKey(WebAssemblyComponentState webAssemblyComponentState)
     {
-        return webAssemblyComponentState.ParentComponentState != null ?
-            default :
-            _webRootComponentManager!.GetRootComponentKey(webAssemblyComponentState.ComponentId);
+        if (webAssemblyComponentState.ParentComponentState != null)
+        {
+            return default;
+        }
+
+        var webRootComponentManager = _webRootComponentManager ?? GetOrCreateWebRootComponentManager();
+
+        return webRootComponentManager.GetRootComponentKey(webAssemblyComponentState.ComponentId);
     }
 
     private static partial class Log

From 013475de858294563ed33562e9a90cdd9cb4fb2d Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Tue, 25 Nov 2025 11:41:59 +0100
Subject: [PATCH 12/13] Rever: Wasm renderer already initializes the manager
 with `OnUpdateRootComponents`.

---
 .../WebAssembly/src/Rendering/WebAssemblyRenderer.cs  | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
index f280d7b0d9aa..242e28ed7ba2 100644
--- a/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
+++ b/src/Components/WebAssembly/WebAssembly/src/Rendering/WebAssemblyRenderer.cs
@@ -224,14 +224,9 @@ protected override ComponentState CreateComponentState(int componentId, ICompone
 
     internal ComponentMarkerKey GetMarkerKey(WebAssemblyComponentState webAssemblyComponentState)
     {
-        if (webAssemblyComponentState.ParentComponentState != null)
-        {
-            return default;
-        }
-
-        var webRootComponentManager = _webRootComponentManager ?? GetOrCreateWebRootComponentManager();
-
-        return webRootComponentManager.GetRootComponentKey(webAssemblyComponentState.ComponentId);
+        return webAssemblyComponentState.ParentComponentState != null ?
+            default :
+            _webRootComponentManager!.GetRootComponentKey(webAssemblyComponentState.ComponentId);
     }
 
     private static partial class Log

From da15cfb6481f767db45fa0e961d656d19e381510 Mon Sep 17 00:00:00 2001
From: Ilona Tomkowicz <itomkowicz@microsoft.com>
Date: Tue, 25 Nov 2025 15:30:05 +0100
Subject: [PATCH 13/13] Feedback - move the initialization to CircuitFatory.

---
 src/Components/Server/src/Circuits/CircuitFactory.cs |  1 +
 src/Components/Server/src/Circuits/RemoteRenderer.cs | 10 +++-------
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/Components/Server/src/Circuits/CircuitFactory.cs b/src/Components/Server/src/Circuits/CircuitFactory.cs
index 0c086f054c03..a9aefb9fbfc9 100644
--- a/src/Components/Server/src/Circuits/CircuitFactory.cs
+++ b/src/Components/Server/src/Circuits/CircuitFactory.cs
@@ -93,6 +93,7 @@ public async ValueTask<CircuitHost> CreateCircuitHostAsync(
             resourceCollection);
 
         circuitActivitySource.Init(new Infrastructure.Server.ComponentsActivityLinkStore(renderer));
+        renderer.GetOrCreateWebRootComponentManager();
 
         // In Blazor Server we have already restored the app state, so we can get the handlers from DI.
         // In Blazor Web the state is provided in the first call to UpdateRootComponents, so we need to
diff --git a/src/Components/Server/src/Circuits/RemoteRenderer.cs b/src/Components/Server/src/Circuits/RemoteRenderer.cs
index 654829189bb2..8e161697abdb 100644
--- a/src/Components/Server/src/Circuits/RemoteRenderer.cs
+++ b/src/Components/Server/src/Circuits/RemoteRenderer.cs
@@ -321,13 +321,9 @@ protected override ComponentState CreateComponentState(int componentId, ICompone
 
     internal ComponentMarkerKey GetMarkerKey(RemoteComponentState remoteComponentState)
     {
-        if (remoteComponentState.ParentComponentState != null)
-        {
-            return default;
-        }
-
-        var webRootComponentManager = _webRootComponentManager ?? GetOrCreateWebRootComponentManager();
-        return webRootComponentManager.GetRootComponentKey(remoteComponentState.ComponentId);
+        return remoteComponentState.ParentComponentState != null ?
+            default :
+            _webRootComponentManager!.GetRootComponentKey(remoteComponentState.ComponentId);
     }
 
     private void ProcessPendingBatch(string? errorMessageOrNull, UnacknowledgedRenderBatch entry)