diff --git a/package.json b/package.json
index deb0162..bece073 100644
--- a/package.json
+++ b/package.json
@@ -25,8 +25,14 @@
   "scripts": {
     "test": "npm run test:node",
     "test:node": "node --import=tsx ./node_modules/poku/lib/bin/index.js tests --showLogs",
+    "test:node:none": "node --import=tsx ./node_modules/poku/lib/bin/index.js tests --showLogs --isolation=none",
+    "test:node:process": "node --import=tsx ./node_modules/poku/lib/bin/index.js tests --showLogs --isolation=process",
     "test:bun": "bun ./node_modules/poku/lib/bin/index.js tests --showLogs",
+    "test:bun:none": "bun ./node_modules/poku/lib/bin/index.js tests --showLogs --isolation=none",
+    "test:bun:process": "bun ./node_modules/poku/lib/bin/index.js tests --showLogs --isolation=process",
     "test:deno": "deno run -A npm:poku tests --showLogs",
+    "test:deno:none": "deno run -A npm:poku tests --showLogs --isolation=none",
+    "test:deno:process": "deno run -A npm:poku tests --showLogs --isolation=process",
     "clean": "rimraf dist",
     "build": "npm run clean && tsc -p tsconfig.dist.json",
     "typecheck": "tsc -p tsconfig.build.json --noEmit",
@@ -56,15 +62,11 @@
     "provenance": true
   },
   "peerDependencies": {
-    "@happy-dom/global-registrator": ">=20",
     "happy-dom": ">=20",
     "jsdom": ">=22",
     "poku": ">=4.1.0"
   },
   "peerDependenciesMeta": {
-    "@happy-dom/global-registrator": {
-      "optional": true
-    },
     "happy-dom": {
       "optional": true
     },
diff --git a/src/dom-env.ts b/src/dom-env.ts
index 0dc31a7..34859c5 100644
--- a/src/dom-env.ts
+++ b/src/dom-env.ts
@@ -1,4 +1,4 @@
-import { GlobalRegistrator } from '@happy-dom/global-registrator';
+import { GlobalWindow } from 'happy-dom';
 import type { RuntimeOptions } from './types.ts';
 
 type SetupDomEnvironmentOptions = {
@@ -19,31 +19,55 @@ const applyReactActEnvironment = (enabled: boolean) => {
   }
 };
 
+const defineGlobal = (key: keyof typeof globalThis, value: unknown) => {
+  Object.defineProperty(globalThis, key, {
+    configurable: true,
+    writable: true,
+    value,
+  });
+};
+
 export const setupHappyDomEnvironment = async (
   options: SetupDomEnvironmentOptions
 ) => {
   if (!globalThis.window || !globalThis.document) {
-    GlobalRegistrator.register({
-      url: options.runtimeOptions.domUrl,
-    });
+    // Save native event primitives before installing Happy DOM globals.
+    // Deno's runtime calls globalThis.dispatchEvent('beforeunload') on exit
+    // using its own native Event constructor — if Happy DOM's dispatchEvent
+    // is installed instead, the type check inside it throws a TypeError.
+    const existingDispatchEvent = globalThis.dispatchEvent;
+    const existingEvent = globalThis.Event;
+    const existingCustomEvent = globalThis.CustomEvent;
+
+    const happyWindow = new GlobalWindow({ url: options.runtimeOptions.domUrl });
 
-    const nativeDispatchEvent = globalThis.window.dispatchEvent;
-    if (typeof nativeDispatchEvent === 'function') {
-      globalThis.dispatchEvent = nativeDispatchEvent.bind(globalThis.window);
+    defineGlobal('window', happyWindow);
+    defineGlobal('document', happyWindow.document);
+    defineGlobal('navigator', happyWindow.navigator);
+    defineGlobal('HTMLElement', happyWindow.HTMLElement);
+    defineGlobal('Element', happyWindow.Element);
+    defineGlobal('Node', happyWindow.Node);
+    defineGlobal('Text', happyWindow.Text);
+    defineGlobal('SVGElement', happyWindow.SVGElement);
+    defineGlobal('MutationObserver', happyWindow.MutationObserver);
+    defineGlobal('requestAnimationFrame', happyWindow.requestAnimationFrame);
+    defineGlobal('cancelAnimationFrame', happyWindow.cancelAnimationFrame);
+
+    // Prefer the runtime's native Event constructors so that Deno's internal
+    // event dispatch (e.g. beforeunload) continues to work correctly.
+    defineGlobal('Event', typeof existingEvent === 'function' ? existingEvent : happyWindow.Event);
+    defineGlobal('CustomEvent', typeof existingCustomEvent === 'function' ? existingCustomEvent : happyWindow.CustomEvent);
+
+    if (typeof existingDispatchEvent === 'function') {
+      globalThis.dispatchEvent = existingDispatchEvent;
+    } else {
+      globalThis.dispatchEvent = happyWindow.dispatchEvent.bind(happyWindow) as unknown as typeof globalThis.dispatchEvent;
     }
   }
 
   applyReactActEnvironment(Boolean(options.enableReactActEnvironment));
 };
 
-const defineGlobal = (key: keyof typeof globalThis, value: unknown) => {
-  Object.defineProperty(globalThis, key, {
-    configurable: true,
-    writable: true,
-    value,
-  });
-};
-
 export const setupJsdomEnvironment = async (
   options: SetupDomEnvironmentOptions
 ) => {
@@ -64,7 +88,7 @@ export const setupJsdomEnvironment = async (
       pretendToBeVisual: true,
     });
 
-    defineGlobal('window', dom.window as unknown as Window & typeof globalThis);
+    defineGlobal('window', dom.window);
     defineGlobal('document', dom.window.document);
     defineGlobal('navigator', dom.window.navigator);
     defineGlobal('HTMLElement', dom.window.HTMLElement);
diff --git a/src/plugin-setup.ts b/src/plugin-setup.ts
index 6fe12bf..0bc565b 100644
--- a/src/plugin-setup.ts
+++ b/src/plugin-setup.ts
@@ -8,6 +8,13 @@ type TsxEsmApiModule = {
 
 const TSX_LOADER_MODULE = 'tsx/esm/api';
 
+// Once tsx is registered in a Node.js process it cannot be safely deregistered
+// and re-registered (tsx's hook worker re-instantiation fails with an invalid
+// URL scheme). Under isolation:'none' everything runs in the same process for
+// its lifetime, so keeping the loader registered permanently is correct.
+const TSX_LOADER_REGISTERED_KEY = Symbol.for('@pokujs/dom.tsx-loader-registered');
+type GlobalWithTsxFlag = typeof globalThis & { [TSX_LOADER_REGISTERED_KEY]?: boolean };
+
 const appendMissingRuntimeArgs = (runtimeOptionArgs: string[]) => {
   for (const arg of runtimeOptionArgs) {
     if (process.argv.includes(arg)) continue;
@@ -19,7 +26,11 @@ const loadDomSetupModule = async (domSetupPath: string) => {
   await import(pathToFileURL(domSetupPath).href);
 };
 
-const registerNodeTsxLoader = async (packageTag: string) => {
+const registerNodeTsxLoader = async (packageTag: string): Promise<() => void> => {
+  const g = globalThis as GlobalWithTsxFlag;
+
+  if (g[TSX_LOADER_REGISTERED_KEY]) return () => {};
+
   const requireFromCwd = createRequire(`${process.cwd()}/`);
 
   try {
@@ -29,7 +40,9 @@ const registerNodeTsxLoader = async (packageTag: string) => {
       throw new Error('Missing register() export from tsx loader API');
     }
 
-    return mod.register();
+    mod.register();
+    g[TSX_LOADER_REGISTERED_KEY] = true;
+    return () => {};
   } catch (error) {
     throw new Error(
       `[${packageTag}] isolation "none" in Node.js requires a working "tsx" installation to load .tsx/.jsx test files.`,