diff --git a/webgpu/link/base.py b/webgpu/link/base.py
index f5f9024..6ea0f26 100644
--- a/webgpu/link/base.py
+++ b/webgpu/link/base.py
@@ -480,8 +480,6 @@ def __init__(self):
         super().__init__()
         self._send_loop = asyncio.new_event_loop()
         self._callback_loop = asyncio.new_event_loop()
-        self._callback_queue = asyncio.Queue()
-
         self._callback_thread = threading.Thread(target=self._start_callback_thread, daemon=True)
         self._callback_thread.start()
 
@@ -516,7 +514,13 @@ def _send_data(self, metadata, data, key=None):
             event = threading.Event()
             self._requests[request_id] = event, key
 
-        asyncio.run_coroutine_threadsafe(self._send_async(data), self._send_loop)
+        try:
+            asyncio.run_coroutine_threadsafe(self._send_async(data), self._send_loop)
+        except RuntimeError:
+            # Event loop is closed — connection is dead, clean up and bail.
+            if event:
+                self._requests.pop(request_id, None)
+            return None
         if event:
             event.wait()
             return self._requests.pop(request_id)
@@ -530,15 +534,19 @@ async def handle_callbacks():
                 try:
                     func, args = await self._callback_queue.get()
                     func(*args)
+                except asyncio.CancelledError:
+                    break
+                except RuntimeError:
+                    break
                 except asyncio.QueueEmpty:
                     pass
                 except Exception as e:
                     print("error in callback", type(e), str(e))
-                # await asyncio.sleep(0.01)
 
         try:
             self._callback_loop = asyncio.new_event_loop()
             asyncio.set_event_loop(self._callback_loop)
+            self._callback_queue = asyncio.Queue()
             self._callback_loop.create_task(handle_callbacks())
             self._callback_loop.run_forever()
         except Exception as e:
diff --git a/webgpu/link/websocket.py b/webgpu/link/websocket.py
index 3567bbc..ae79d23 100644
--- a/webgpu/link/websocket.py
+++ b/webgpu/link/websocket.py
@@ -122,3 +122,16 @@ async def start_websocket():
 
     def stop(self):
         self._send_loop.call_soon_threadsafe(self._stop.set_result, None)
+
+        # Stop the callback event loop so the _callback_thread exits.
+        try:
+            self._callback_loop.call_soon_threadsafe(self._callback_loop.stop)
+        except RuntimeError:
+            pass  # Event loop already closed
+
+        # Unblock any threads stuck waiting for websocket RPC responses.
+        for rid, val in list(self._requests.items()):
+            if isinstance(val, tuple):
+                event, key = val
+                if isinstance(event, threading.Event):
+                    event.set()
diff --git a/webgpu/platform.py b/webgpu/platform.py
index 76f8f7e..92b2094 100644
--- a/webgpu/platform.py
+++ b/webgpu/platform.py
@@ -206,3 +206,32 @@ def init_pyodide(link_):
 
     LinkBase.register_serializer(BaseWebGPUHandle, lambda _, v: v.handle)
     LinkBase.register_serializer(BaseWebGPUObject, lambda _, v: v.__dict__ or None)
+
+
+def reset():
+    """Reset the platform globals so that init can be called again.
+
+    Used by test runners that start and stop multiple app instances
+    in the same process.
+    """
+    global js, websocket_server, link, create_proxy, destroy_proxy
+    if websocket_server is not None:
+        try:
+            websocket_server.stop()
+        except RuntimeError:
+            pass  # Event loop already closed
+    js = None
+    websocket_server = None
+    link = None
+    if not is_pyodide:
+        create_proxy = None
+        destroy_proxy = None
+
+    # Reset cached WebGPU device so it is re-requested on the new connection.
+    from . import utils as _utils
+    _utils._device = None
+
+    # Reset the cached font atlas — its GPU texture is tied to the old
+    # connection and would deadlock when accessed on a new one.
+    from . import font as _font
+    _font._default_font_atlas = None
diff --git a/webgpu/scene.py b/webgpu/scene.py
index 31a7ab1..d8d9ddf 100644
--- a/webgpu/scene.py
+++ b/webgpu/scene.py
@@ -97,7 +97,11 @@ def init(self, canvas):
             self.options.timestamp = time.time()
             self.options.update_buffers()
             for obj in self.render_objects:
-                obj._update_and_create_render_pipeline(self.options)
+                try:
+                    obj._update_and_create_render_pipeline(self.options)
+                except Exception as e:
+                    print(f'Warning: failed to init renderer {type(obj).__name__}: {e}')
+                    obj.active = False
 
             camera = self.options.camera
             self._js_render = platform.create_proxy(self._render_direct)
@@ -308,8 +312,11 @@ def cleanup(self):
                 self.options.camera._render_function = None
                 self.options.camera._get_position_function = None
                 self.input_handler.unregister_callbacks()
-                platform.destroy_proxy(self._js_render)
-                del self._js_render
-                self.canvas._on_resize_callbacks.remove(self.render)
-                self.canvas._on_update_html_canvas.remove(self.__on_update_html_canvas)
+                if hasattr(self, '_js_render'):
+                    platform.destroy_proxy(self._js_render)
+                    del self._js_render
+                if self.render in self.canvas._on_resize_callbacks:
+                    self.canvas._on_resize_callbacks.remove(self.render)
+                if self.__on_update_html_canvas in self.canvas._on_update_html_canvas:
+                    self.canvas._on_update_html_canvas.remove(self.__on_update_html_canvas)
                 self.canvas = None