diff --git a/extensions/vscode-api-tests/src/singlefolder-tests/notebook.test.ts b/extensions/vscode-api-tests/src/singlefolder-tests/notebook.test.ts
index 01a7c87479e4335a896cacb8fd4d6a31262c8d03..b7bfc767d5d278c24a5c97c059595fbd9fe95bef 100644
--- a/extensions/vscode-api-tests/src/singlefolder-tests/notebook.test.ts
+++ b/extensions/vscode-api-tests/src/singlefolder-tests/notebook.test.ts
@@ -834,7 +834,6 @@ suite('Notebook API tests', function () {
 		assert.ok(cell.executionSummary);
 		assert.strictEqual(cell.executionSummary!.success, true);
 		assert.strictEqual(typeof cell.executionSummary!.executionOrder, 'number');
-
 	});
 
 	test('initialize executionSummary', async () => {
diff --git a/src/vs/workbench/api/common/extHostNotebookKernels.ts b/src/vs/workbench/api/common/extHostNotebookKernels.ts
index a83a15041305ebb5b05f5db266023f1193ac26a2..87e0868cc70ace507cdba8dc6ccf5a4a6ec13cb4 100644
--- a/src/vs/workbench/api/common/extHostNotebookKernels.ts
+++ b/src/vs/workbench/api/common/extHostNotebookKernels.ts
@@ -468,6 +468,10 @@ class NotebookCellExecutionTask extends Disposable {
 					runEndTime: endTime,
 					lastRunSuccess: success
 				});
+
+				// The last update needs to be ordered correctly and applied immediately,
+				// so we use updateSoon and immediately flush.
+				that._collector.flush();
 			},
 
 			clearOutput(cell?: vscode.NotebookCell): Thenable<void> {
@@ -511,13 +515,17 @@ class TimeoutBasedCollector<T> {
 		this.batch.push(item);
 		if (!this.waitPromise) {
 			this.waitPromise = timeout(this.delay).then(() => {
-				this.waitPromise = undefined;
-				const batch = this.batch;
-				this.batch = [];
-				return this.callback(batch);
+				return this.flush();
 			});
 		}
 
 		return this.waitPromise;
 	}
+
+	flush(): void | Promise<void> {
+		this.waitPromise = undefined;
+		const batch = this.batch;
+		this.batch = [];
+		return this.callback(batch);
+	}
 }