diff --git a/third_party/blink/renderer/modules/webaudio/audio_worklet_processor.cc b/third_party/blink/renderer/modules/webaudio/audio_worklet_processor.cc
index 9d4533f75be6e0..ad7a35484c9655 100644
--- a/third_party/blink/renderer/modules/webaudio/audio_worklet_processor.cc
+++ b/third_party/blink/renderer/modules/webaudio/audio_worklet_processor.cc
@@ -466,7 +466,11 @@ bool AudioWorkletProcessor::Process(
   TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("audio-worklet"),
                "AudioWorkletProcessor::Process");
 
-  DCHECK(global_scope_->IsContextThread());
+  // Process() enters the AudioWorklet's v8::Isolate via ScriptState::Scope
+  // below. V8 isolates are single-threaded; entering from a thread that does
+  // not own the isolate is undefined behavior (HandleScopeData / heap races).
+  // Upgrade to CHECK so a stale render-thread task runner cannot reach V8.
+  CHECK(global_scope_->IsContextThread());
   DCHECK(!hasErrorOccurred());
 
   ScriptState* script_state =
diff --git a/third_party/blink/renderer/modules/webaudio/offline_audio_destination_handler.cc b/third_party/blink/renderer/modules/webaudio/offline_audio_destination_handler.cc
index 6db772e60558e5..a81df0b73b0f45 100644
--- a/third_party/blink/renderer/modules/webaudio/offline_audio_destination_handler.cc
+++ b/third_party/blink/renderer/modules/webaudio/offline_audio_destination_handler.cc
@@ -374,4 +374,17 @@ void OfflineAudioDestinationHandler::RestartRendering() {
   PrepareTaskRunnerForRendering();
 }
 
+void OfflineAudioDestinationHandler::PrepareTaskRunnerForWorklet() {
+  DCHECK(IsMainThread());
+
+  // Called from BaseAudioContext::NotifyWorkletIsReady() while the context is
+  // suspended. If startRendering() has already created `render_thread_`, that
+  // thread's task runner is now stale: rendering must move to the AudioWorklet
+  // thread (which owns the V8 isolate that AudioWorkletProcessor::Process()
+  // will enter). Re-run the same task-runner selection logic so a subsequent
+  // resume() posts DoOfflineRendering to the worklet thread instead of the
+  // stale NonMainThread.
+  PrepareTaskRunnerForRendering();
+}
+
 }  // namespace blink
diff --git a/third_party/blink/renderer/modules/webaudio/offline_audio_destination_handler.h b/third_party/blink/renderer/modules/webaudio/offline_audio_destination_handler.h
index 461facfdf0bcf1..b3c9dd5ba9e01e 100644
--- a/third_party/blink/renderer/modules/webaudio/offline_audio_destination_handler.h
+++ b/third_party/blink/renderer/modules/webaudio/offline_audio_destination_handler.h
@@ -47,7 +47,7 @@ class OfflineAudioDestinationHandler final : public AudioDestinationHandler {
   void Pause() override;
   void Resume() override;
   uint32_t MaxChannelCount() const override;
-  void PrepareTaskRunnerForWorklet() override {}
+  void PrepareTaskRunnerForWorklet() override;
 
   void RestartRendering() override;