diff --git a/src/views/workflow-history/helpers/__tests__/workflow-history-grouper.test.tsx b/src/views/workflow-history/helpers/__tests__/workflow-history-grouper.test.tsx
index 4529096d0..70ab81c7e 100644
--- a/src/views/workflow-history/helpers/__tests__/workflow-history-grouper.test.tsx
+++ b/src/views/workflow-history/helpers/__tests__/workflow-history-grouper.test.tsx
@@ -471,6 +471,31 @@ describe(WorkflowHistoryGrouper.name, () => {
     expect(Object.keys(groups).length).toBe(0);
   });
 
+  it('should notify subscribers after pending events are processed', async () => {
+    const { grouper, waitForProcessing } = setup();
+    const scheduledEvent = createScheduleActivityEvent('7');
+    grouper.updateEvents([scheduledEvent]);
+    await waitForProcessing();
+    // subscribe to state changes
+    const mockOnChange = jest.fn();
+    grouper.onChange(mockOnChange);
+    // add pending event on history after scheduled event is processed and onChange is subscribed
+    await grouper.updatePendingEvents({
+      pendingStartActivities: [pendingActivityTaskStartEvent],
+      pendingStartDecision: null,
+    });
+
+    await waitForProcessing();
+    expect(mockOnChange).toHaveBeenCalled();
+
+    const callArgs = mockOnChange.mock.calls[0][0];
+    expect(callArgs.groups['7']).toBeDefined();
+    expect(callArgs.groups['7'].events).toEqual([
+      scheduledEvent,
+      pendingActivityTaskStartEvent,
+    ]);
+  });
+
   it('should handle pending decision buffer clearing when decision changes', async () => {
     const { grouper, waitForProcessing } = setup();
 
diff --git a/src/views/workflow-history/helpers/workflow-history-grouper.ts b/src/views/workflow-history/helpers/workflow-history-grouper.ts
index e0917a0d8..30c376d6f 100644
--- a/src/views/workflow-history/helpers/workflow-history-grouper.ts
+++ b/src/views/workflow-history/helpers/workflow-history-grouper.ts
@@ -413,6 +413,10 @@ export default class WorkflowHistoryGrouper {
     );
 
     this.updatePendingDecision(currentPendingDecision, newPendingDecision);
+
+    // Report progress to all subscribers
+    const state = this.getState();
+    this.subscribers.forEach((callback) => callback(state));
   }
 
   /**