diff --git a/moli-benchmark/wpt-cross-current/passed-cases.txt b/moli-benchmark/wpt-cross-current/passed-cases.txt
index dd2807ebbe..1895f591ba 100644
--- a/moli-benchmark/wpt-cross-current/passed-cases.txt
+++ b/moli-benchmark/wpt-cross-current/passed-cases.txt
@@ -4556,6 +4556,7 @@ dom/observable/tentative/observable-first.any.js?moli-wpt-any=window
 dom/observable/tentative/observable-forEach.any.js?moli-wpt-any=dedicatedworker
 dom/observable/tentative/observable-forEach.any.js?moli-wpt-any=window
 dom/observable/tentative/observable-forEach.window.js?moli-wpt-script=window
+dom/observable/tentative/observable-inspect.any.js?moli-wpt-any=dedicatedworker
 dom/observable/tentative/observable-inspect.any.js?moli-wpt-any=window
 dom/observable/tentative/observable-last.any.js?moli-wpt-any=dedicatedworker
 dom/observable/tentative/observable-last.any.js?moli-wpt-any=window
@@ -10020,6 +10021,7 @@ webidl/ecmascript-binding/constructors.html
 webidl/ecmascript-binding/default-iterator-object.html
 webidl/ecmascript-binding/default-toJSON-cross-realm.html
 webidl/ecmascript-binding/es-exceptions/exceptions.html
+webidl/ecmascript-binding/global-immutable-prototype.any.js?moli-wpt-any=dedicatedworker
 webidl/ecmascript-binding/global-object-implicit-this-value-cross-realm.html
 webidl/ecmascript-binding/has-instance.html
 webidl/ecmascript-binding/interface-object-set-receiver.html
diff --git a/moli-renderer-v8/src/worker/thread/tests/lifecycle.rs b/moli-renderer-v8/src/worker/thread/tests/lifecycle.rs
index b283d4e263..a781816a5d 100644
--- a/moli-renderer-v8/src/worker/thread/tests/lifecycle.rs
+++ b/moli-renderer-v8/src/worker/thread/tests/lifecycle.rs
@@ -276,7 +276,7 @@ async fn worker_global_prototype_chains_inherit_event_target_and_are_immutable()
                 format!(
                     r#"
                     const result = ({fixture})({interface:?});
-                    if (result.checks !== 46 || result.failures.length) {{
+                    if (result.checks !== 61 || result.failures.length) {{
                         throw new Error(JSON.stringify(result));
                     }}
                     "#
diff --git a/moli-renderer-v8/tests/fixtures/worker-global-prototypes.js b/moli-renderer-v8/tests/fixtures/worker-global-prototypes.js
index 003b9ce845..768205377e 100644
--- a/moli-renderer-v8/tests/fixtures/worker-global-prototypes.js
+++ b/moli-renderer-v8/tests/fixtures/worker-global-prototypes.js
@@ -38,6 +38,11 @@
   check(Object.prototype.toString.call(WorkerGlobalScope.prototype) === '[object WorkerGlobalScope]', 'worker tag');
   check(throwsTypeError(() => new scopeConstructor()), 'specific illegal constructor');
   check(throwsTypeError(() => new WorkerGlobalScope()), 'worker illegal constructor');
+  check(typeof self.when === 'function', 'inherited when exposed');
+  check(self.when === eventTarget.prototype.when, 'inherited when identity');
+  for (const value of chain.slice(0, 3)) {
+    check(!Object.hasOwn(value, 'when'), 'when is inherited');
+  }
   test('prototype extension', () => {
     const key = Symbol('EventTarget extension');
     eventTarget.prototype[key] = 17;
@@ -56,6 +61,33 @@
     self.dispatchEvent(new Event('worker-prototype-probe'));
     check(values.length === 1, 'global listener removal still works');
   });
+  test('inherited observable events', () => {
+    const controller = new AbortController();
+    const values = [];
+    const observable = self.when('worker-prototype-probe');
+    check(observable instanceof Observable, 'when returns Observable');
+    observable.subscribe(event => values.push(event), {signal: controller.signal});
+    const first = new Event('worker-prototype-probe');
+    self.dispatchEvent(first);
+    check(values.length === 1 && values[0] === first, 'when receives global dispatch');
+    check(first.target === self, 'dispatched event target is global');
+    controller.abort();
+    self.dispatchEvent(new Event('worker-prototype-probe'));
+    check(values.length === 1, 'abort removes global listener');
+  });
+  test('global error reporting', () => {
+    const errors = [];
+    const marker = new Error('inspector abort');
+    const controller = new AbortController();
+    self.when('error').take(1).subscribe(event => {
+      errors.push(event.error);
+      event.preventDefault();
+    });
+    new Observable(subscriber => subscriber.next(1))
+      .inspect({abort() { throw marker; }})
+      .subscribe(() => controller.abort(), {signal: controller.signal});
+    check(errors.length === 1 && errors[0] === marker, 'when receives reported callback error');
+  });
   test('receiver branding', () => {
     let conversions = 0;
     let traps = 0;
@@ -67,6 +99,7 @@
       getPrototypeOf() { traps++; throw new Error('author proxy trap'); }
     }), revoked.proxy]) {
       check(throwsTypeError(() => eventTarget.prototype.addEventListener.call(receiver, type, () => {})), 'addEventListener rejects forged/proxy receiver');
+      check(throwsTypeError(() => eventTarget.prototype.when.call(receiver, type)), 'when rejects forged/proxy receiver');
     }
     check(conversions === 0, 'brand checked before conversion');
     check(traps === 0, 'brand checked without proxy traps');
@@ -76,6 +109,7 @@
     try {
       check(Object.getPrototypeOf(WorkerGlobalScope.prototype) === eventTarget.prototype, 'prototype keeps intrinsic EventTarget');
       check(Object.getPrototypeOf(WorkerGlobalScope) === eventTarget, 'constructor keeps intrinsic EventTarget');
+      check(self.when === eventTarget.prototype.when, 'when keeps intrinsic method');
     } finally { self.EventTarget = eventTarget; }
   });
   return {checks, failures};