diff --git a/src/Browser/Avalonia.Browser/BrowserDispatcherImpl.cs b/src/Browser/Avalonia.Browser/BrowserDispatcherImpl.cs
index d7eaa81abf..2d3d031c9b 100644
--- a/src/Browser/Avalonia.Browser/BrowserDispatcherImpl.cs
+++ b/src/Browser/Avalonia.Browser/BrowserDispatcherImpl.cs
@@ -14,16 +14,17 @@ internal class BrowserDispatcherImpl : IDispatcherImpl
     private bool _signaled;
     private int? _timerId;
 
-    private readonly Action _timerCallback;
-    private readonly Action _signalCallback;
-
     public BrowserDispatcherImpl()
     {
         _thread = Thread.CurrentThread;
         _clock = Stopwatch.StartNew();
 
-        _timerCallback = () => Timer?.Invoke();
-        _signalCallback = () =>
+        TimerHelper.Interval += () =>
+        {
+            Timer?.Invoke();
+        };
+        
+        TimerHelper.Timeout = () =>
         {
             _signaled = false;
             Signaled?.Invoke();
@@ -44,7 +45,7 @@ internal class BrowserDispatcherImpl : IDispatcherImpl
 
         // NOTE: by HTML5 spec minimal timeout is 4ms, but Chrome seems to work well with 1ms as well.
         var interval = 1;
-        TimerHelper.SetTimeout(_signalCallback, interval);
+        TimerHelper.SetTimeout(interval);
     }
 
     public void UpdateTimer(long? dueTimeInMs)
@@ -58,7 +59,7 @@ internal class BrowserDispatcherImpl : IDispatcherImpl
         if (dueTimeInMs.HasValue)
         {
             var interval = Math.Max(1, dueTimeInMs.Value - _clock.ElapsedMilliseconds);
-            _timerId = TimerHelper.SetInterval(_timerCallback, (int)interval);
+            _timerId = TimerHelper.SetInterval((int)interval);
         }
     }
 }
diff --git a/src/Browser/Avalonia.Browser/Interop/TimerHelper.cs b/src/Browser/Avalonia.Browser/Interop/TimerHelper.cs
index 32c2f66565..aff472e232 100644
--- a/src/Browser/Avalonia.Browser/Interop/TimerHelper.cs
+++ b/src/Browser/Avalonia.Browser/Interop/TimerHelper.cs
@@ -6,17 +6,37 @@ namespace Avalonia.Browser.Interop;
 internal static partial class TimerHelper
 {
     [JSImport("TimerHelper.runAnimationFrames", AvaloniaModule.MainModuleName)]
-    public static partial void RunAnimationFrames(
-        [JSMarshalAs<JSType.Function<JSType.Number, JSType.Boolean>>] Func<double, bool> renderFrameCallback);
+    public static partial void RunAnimationFrames();
 
-    [JSImport("globalThis.setTimeout")]
-    public static partial int SetTimeout([JSMarshalAs<JSType.Function>] Action callback, int intervalMs);
+    public static Action<double>? AnimationFrame;
+    [JSExport]
+    public static void JsExportOnAnimationFrame(double d)
+    {
+        AnimationFrame?.Invoke(d);
+    }
+    
+    public static Action? Timeout;
+    [JSExport]
+    public static void JsExportOnTimeout()
+    {
+        Timeout?.Invoke();
+    }
+
+    [JSImport("TimerHelper.setTimeout", AvaloniaModule.MainModuleName)]
+    public static partial int SetTimeout(int intervalMs);
 
     [JSImport("globalThis.clearTimeout")]
     public static partial int ClearTimeout(int id);
 
-    [JSImport("globalThis.setInterval")]
-    public static partial int SetInterval([JSMarshalAs<JSType.Function>] Action callback, int intervalMs);
+    public static Action? Interval;
+    [JSExport]
+    public static void JsExportOnInterval()
+    {
+        Interval?.Invoke();
+    }
+    
+    [JSImport("TimerHelper.setInterval", AvaloniaModule.MainModuleName)]
+    public static partial int SetInterval( int intervalMs);
 
     [JSImport("globalThis.clearInterval")]
     public static partial int ClearInterval(int id);
diff --git a/src/Browser/Avalonia.Browser/Rendering/BrowserRenderTimer.cs b/src/Browser/Avalonia.Browser/Rendering/BrowserRenderTimer.cs
index 55f42d0df7..fea94d0248 100644
--- a/src/Browser/Avalonia.Browser/Rendering/BrowserRenderTimer.cs
+++ b/src/Browser/Avalonia.Browser/Rendering/BrowserRenderTimer.cs
@@ -38,18 +38,16 @@ internal class BrowserRenderTimer : IRenderTimer
         if (!_started)
         {
             _started = true;
-            TimerHelper.RunAnimationFrames(RenderFrameCallback);
+            TimerHelper.AnimationFrame += RenderFrameCallback;
+            TimerHelper.RunAnimationFrames();
         }
     }
 
-    private bool RenderFrameCallback(double timestamp)
+    private void RenderFrameCallback(double timestamp)
     {
         if (_tick is { } tick)
         {
             tick.Invoke(TimeSpan.FromMilliseconds(timestamp));
-            return true;
         }
-
-        return false;
     }
 }
diff --git a/src/Browser/Avalonia.Browser/Rendering/RenderTargetBrowserSurface.cs b/src/Browser/Avalonia.Browser/Rendering/RenderTargetBrowserSurface.cs
index bbd113b75a..bfbf7cdce0 100644
--- a/src/Browser/Avalonia.Browser/Rendering/RenderTargetBrowserSurface.cs
+++ b/src/Browser/Avalonia.Browser/Rendering/RenderTargetBrowserSurface.cs
@@ -62,7 +62,7 @@ internal class RenderTargetBrowserSurface : BrowserSurface
         public BrowserRenderTarget? Target =>
             _target ??= BrowserRenderTarget.GetRenderTarget(_targetId, () => CanvasSize);
 
-        public bool IsReady => Target != null;
+        public bool IsReady => Target != null && CanvasSize.Size != default;
         public bool UsesContexts => Target!.PlatformGraphicsContext != null;
         public bool UsesSharedContext => UsesContexts;
         public (PixelSize Size, double Scaling) CanvasSize { get; set; }
@@ -95,8 +95,7 @@ internal class RenderTargetBrowserSurface : BrowserSurface
 
     public static RenderTargetBrowserSurface Create(JSObject container, IReadOnlyList<BrowserRenderingMode> modes)
     {
-        // TODO: Get thread id from JSWebWorker
-        var js = CanvasHelper.CreateRenderTargetSurface(container, modes.Select(m => (int)m).ToArray(), 0);
+        var js = CanvasHelper.CreateRenderTargetSurface(container, modes.Select(m => (int)m).ToArray(), RenderWorker.WorkerThreadId);
         return new RenderTargetBrowserSurface(js);
     }
 }
\ No newline at end of file
diff --git a/src/Browser/Avalonia.Browser/WindowingPlatform.cs b/src/Browser/Avalonia.Browser/WindowingPlatform.cs
index 5ecaa1bb84..af78d616f4 100644
--- a/src/Browser/Avalonia.Browser/WindowingPlatform.cs
+++ b/src/Browser/Avalonia.Browser/WindowingPlatform.cs
@@ -4,6 +4,7 @@ using System.Threading;
 using Avalonia.Browser.Interop;
 using Avalonia.Browser.Skia;
 using Avalonia.Controls.ApplicationLifetimes;
+using Avalonia.Controls.Platform;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.Platform;
@@ -64,12 +65,12 @@ internal class BrowserWindowingPlatform : IWindowingPlatform
             .Bind<ICursorFactory>().ToSingleton<CssCursorFactory>()
             .Bind<IKeyboardDevice>().ToConstant(s_keyboard)
             .Bind<IPlatformSettings>().ToSingleton<BrowserPlatformSettings>()
-            .Bind<IDispatcherImpl>().ToSingleton<BrowserDispatcherImpl>()
             .Bind<IWindowingPlatform>().ToConstant(instance)
             .Bind<IPlatformGraphics>().ToConstant(new BrowserSkiaGraphics())
             .Bind<IPlatformIconLoader>().ToSingleton<IconLoaderStub>()
             .Bind<PlatformHotkeyConfiguration>().ToSingleton<PlatformHotkeyConfiguration>()
             .Bind<IActivatableLifetime>().ToSingleton<BrowserActivatableLifetime>();
+        AvaloniaLocator.CurrentMutable.Bind<IDispatcherImpl>().ToSingleton<BrowserDispatcherImpl>();
 
         if (AvaloniaLocator.Current.GetService<BrowserPlatformOptions>() is { } options
             && options.RegisterAvaloniaServiceWorker)
diff --git a/src/Browser/Avalonia.Browser/build/Avalonia.Browser.targets b/src/Browser/Avalonia.Browser/build/Avalonia.Browser.targets
index 53ad40168a..fe66c02dd8 100644
--- a/src/Browser/Avalonia.Browser/build/Avalonia.Browser.targets
+++ b/src/Browser/Avalonia.Browser/build/Avalonia.Browser.targets
@@ -6,6 +6,7 @@
   <ItemGroup>
     <!-- So we can access Emscripten APIs -->
     <EmccExportedRuntimeMethod Include="GL" />
+    <EmccExportedRuntimeMethod Include="PThread" />
   </ItemGroup>
   
   <!-- Fallback for applications without StaticWebAssetsEnabled (legacy WASM SDK) -->
diff --git a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/jsExports.ts b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/jsExports.ts
new file mode 100644
index 0000000000..18fde7449a
--- /dev/null
+++ b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/jsExports.ts
@@ -0,0 +1,12 @@
+export class JsExports {
+    public static resolvedExports?: any;
+    public static exportsPromise: Promise<any>;
+}
+async function resolveExports (): Promise<any> {
+    const runtimeApi = await globalThis.getDotnetRuntime(0);
+    if (runtimeApi == null) { return; }
+    JsExports.resolvedExports = await runtimeApi.getAssemblyExports("Avalonia.Browser.dll");
+    return JsExports.resolvedExports;
+}
+
+JsExports.exportsPromise = resolveExports();
diff --git a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/surfaces/htmlSurfaceBase.ts b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/surfaces/htmlSurfaceBase.ts
index fcb71828e4..50290add9a 100644
--- a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/surfaces/htmlSurfaceBase.ts
+++ b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/surfaces/htmlSurfaceBase.ts
@@ -26,6 +26,7 @@ export abstract class HtmlCanvasSurfaceBase extends CanvasSurface {
     public onSizeChanged(sizeChangedCallback: (width: number, height: number, dpr: number) => void) {
         if (this.sizeChangedCallback) { throw new Error("For simplicity, we don't support multiple size changed callbacks per surface, not needed yet."); }
         this.sizeChangedCallback = sizeChangedCallback;
+        if (this.sizeParams) { this.sizeChangedCallback(this.sizeParams[0], this.sizeParams[1], this.sizeParams[2]); }
     }
 
     public ensureSize() {
diff --git a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/surfaces/webRenderTargetRegistry.ts b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/surfaces/webRenderTargetRegistry.ts
index 600e832fde..f8d7ab326f 100644
--- a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/surfaces/webRenderTargetRegistry.ts
+++ b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/surfaces/webRenderTargetRegistry.ts
@@ -21,9 +21,13 @@ export class WebRenderTargetRegistry {
         } else {
             const self = globalThis as any;
             const module = self.Module ?? self.getDotnetRuntime(0)?.Module;
-            const pthread = module?.PThread;
-            if (pthread == null) { throw new Error("Unable to access emscripten PThread api"); }
-            const worker = pthread.pthreads[pthreadId]?.worker as Worker;
+            const pthreads = module?.PThread;
+            if (pthreads == null) { throw new Error("Unable to access emscripten PThread api"); }
+            const pthread = pthreads.pthreads[pthreadId];
+            if (pthread == null) { throw new Error(`Unable get pthread with id ${pthreadId}`); }
+            let worker: Worker | undefined;
+            if (pthread.postMessage != null) { worker = pthread as Worker; } else { worker = pthread.worker; }
+
             if (worker == null) { throw new Error(`Unable get Worker for pthread ${pthreadId}`); }
             const offscreen = canvas.transferControlToOffscreen();
             worker.postMessage({
@@ -31,7 +35,7 @@ export class WebRenderTargetRegistry {
                 canvas: offscreen,
                 modes: preferredModes,
                 id
-            });
+            }, [offscreen]);
             WebRenderTargetRegistry.registry[id] = {
                 canvas,
                 worker
@@ -41,18 +45,18 @@ export class WebRenderTargetRegistry {
     }
 
     static initializeWorker() {
-        self.addEventListener("onmessage", ev => {
-            const msg = ev as MessageEvent;
+        const oldHandler = self.onmessage;
+        self.onmessage = ev => {
+            const msg = ev;
             if (msg.data.avaloniaCmd === "registerCanvas") {
                 WebRenderTargetRegistry.targets[msg.data.id] = WebRenderTargetRegistry.createRenderTarget(msg.data.canvas, msg.data.modes);
-            }
-            if (msg.data.avaloniaCmd === "unregisterCanvas") {
+            } else if (msg.data.avaloniaCmd === "unregisterCanvas") {
                 /* eslint-disable */
                 // Our keys are _always_ numbers and are safe to delete
                 delete WebRenderTargetRegistry.targets[msg.data.id];
                 /* eslint-enable */
-            }
-        });
+            } else if (oldHandler != null) { oldHandler.call(self, ev); }
+        };
     }
 
     static getRenderTarget(id: number): WebRenderTarget | undefined {
diff --git a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/timer.ts b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/timer.ts
index 51a5590d25..3ccd669293 100644
--- a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/timer.ts
+++ b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/timer.ts
@@ -1,12 +1,33 @@
+import { JsExports } from "./jsExports";
+
 export class TimerHelper {
-    public static runAnimationFrames(renderFrameCallback: (timestamp: number) => boolean): void {
+    public static runAnimationFrames(): void {
         function render(time: number) {
-            const next = renderFrameCallback(time);
-            if (next) {
-                self.requestAnimationFrame(render);
+            if (JsExports.resolvedExports != null) {
+                JsExports.resolvedExports.Avalonia.Browser.Interop.TimerHelper.JsExportOnAnimationFrame(time);
             }
+            self.requestAnimationFrame(render);
         }
-
         self.requestAnimationFrame(render);
     }
+
+    static onTimeout() {
+        if (JsExports.resolvedExports != null) {
+            JsExports.resolvedExports.Avalonia.Browser.Interop.TimerHelper.JsExportOnTimeout();
+        } else { console.error("TimerHelper.onTimeout call while uninitialized"); }
+    }
+
+    static onInterval() {
+        if (JsExports.resolvedExports != null) {
+            JsExports.resolvedExports.Avalonia.Browser.Interop.TimerHelper.JsExportOnInterval();
+        } else { console.error("TimerHelper.onInterval call while uninitialized"); }
+    }
+
+    public static setTimeout(interval: number): number {
+        return setTimeout(TimerHelper.onTimeout, interval);
+    }
+
+    public static setInterval(interval: number): number {
+        return setInterval(TimerHelper.onInterval, interval);
+    }
 }