4 files changed, 18 insertions, 8 deletions
diff --git a/runtime/js/11_workers.js b/runtime/js/11_workers.js
index 80e85a3a1..5b8d03e71 100644
--- a/runtime/js/11_workers.js
+++ b/runtime/js/11_workers.js
@@ -140,14 +140,16 @@
         error: null,
       });
 
-      let handled = false;
-
       this.dispatchEvent(event);
-      if (event.defaultPrevented) {
-        handled = true;
+      // Don't bubble error event to window for loader errors (`!e.fileName`).
+      // TODO(nayeemrmn): Currently these are never bubbled because worker
+      // error event fields aren't populated correctly and `e.fileName` is
+      // always empty.
+      if (e.fileName && !event.defaultPrevented) {
+        window.dispatchEvent(event);
       }
 
-      return handled;
+      return event.defaultPrevented;
     }
 
     #pollControl = async () => {
@@ -165,7 +167,7 @@
           } /* falls through */
           case 2: { // Error
             if (!this.#handleError(data)) {
-              throw new Error("Unhandled error event in child worker.");
+              throw new Error("Unhandled error in child worker.");
             }
             break;
           }
diff --git a/runtime/js/99_main.js b/runtime/js/99_main.js
index 3a37abeab..44d457e5c 100644
--- a/runtime/js/99_main.js
+++ b/runtime/js/99_main.js
@@ -558,6 +558,7 @@ delete Object.prototype.__proto__;
 
     eventTarget.setEventTargetData(globalThis);
 
+    defineEventHandler(window, "error");
     defineEventHandler(window, "load");
     defineEventHandler(window, "unload");
 
diff --git a/runtime/web_worker.rs b/runtime/web_worker.rs
index 0e3167041..014b3e738 100644
--- a/runtime/web_worker.rs
+++ b/runtime/web_worker.rs
@@ -119,6 +119,7 @@ pub struct WebWorkerInternalHandle {
   has_terminated: Arc<AtomicBool>,
   terminate_waker: Arc<AtomicWaker>,
   isolate_handle: v8::IsolateHandle,
+  pub name: String,
   pub worker_type: WebWorkerType,
 }
 
@@ -264,6 +265,7 @@ impl WebWorkerHandle {
 
 fn create_handles(
   isolate_handle: v8::IsolateHandle,
+  name: String,
   worker_type: WebWorkerType,
 ) -> (WebWorkerInternalHandle, SendableWebWorkerHandle) {
   let (parent_port, worker_port) = create_entangled_message_port();
@@ -272,13 +274,14 @@ fn create_handles(
   let has_terminated = Arc::new(AtomicBool::new(false));
   let terminate_waker = Arc::new(AtomicWaker::new());
   let internal_handle = WebWorkerInternalHandle {
-    sender: ctrl_tx,
+    name,
     port: Rc::new(parent_port),
     termination_signal: termination_signal.clone(),
     has_terminated: has_terminated.clone(),
     terminate_waker: terminate_waker.clone(),
     isolate_handle: isolate_handle.clone(),
     cancel: CancelHandle::new_rc(),
+    sender: ctrl_tx,
     worker_type,
   };
   let external_handle = SendableWebWorkerHandle {
@@ -452,7 +455,7 @@ impl WebWorker {
     let (internal_handle, external_handle) = {
       let handle = js_runtime.v8_isolate().thread_safe_handle();
       let (internal_handle, external_handle) =
-        create_handles(handle, options.worker_type);
+        create_handles(handle, name.clone(), options.worker_type);
       let op_state = js_runtime.op_state();
       let mut op_state = op_state.borrow_mut();
       op_state.put(internal_handle.clone());
diff --git a/runtime/worker.rs b/runtime/worker.rs
index db9490dbe..983f174aa 100644
--- a/runtime/worker.rs
+++ b/runtime/worker.rs
@@ -217,6 +217,10 @@ impl MainWorker {
   async fn evaluate_module(&mut self, id: ModuleId) -> Result<(), AnyError> {
     let mut receiver = self.js_runtime.mod_evaluate(id);
     tokio::select! {
+      // Not using biased mode leads to non-determinism for relatively simple
+      // programs.
+      biased;
+
       maybe_result = &mut receiver => {
         debug!("received module evaluate {:#?}", maybe_result);
         maybe_result.expect("Module evaluation result not provided.")