diff --git a/src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts b/src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts
index 2aa027c29ba2e..8706def9f288c 100644
--- a/src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts
+++ b/src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts
@@ -188,9 +188,15 @@ async function webviewPreloads(ctx: PreloadContext) {
 		}, 0);
 	};
 
-	const isEditableElement = (element: Element) => {
-		return element.tagName.toLowerCase() === 'input' || element.tagName.toLowerCase() === 'textarea'
-			|| ('editContext' in element && !!element.editContext);
+	const hasActiveEditableElement = (
+		parent: Node | DocumentFragment,
+		root: ShadowRoot | Document = document
+	): boolean => {
+		const element = root.activeElement;
+		return !!(element && parent.contains(element)
+			&& (element.matches(':read-write') || element.tagName.toLowerCase() === 'select'
+				|| (element.shadowRoot && hasActiveEditableElement(element.shadowRoot, element.shadowRoot)))
+		);
 	};
 
 	// check if an input element is focused within the output element
@@ -202,7 +208,7 @@ async function webviewPreloads(ctx: PreloadContext) {
 		}
 
 		const id = lastFocusedOutput?.id;
-		if (id && (isEditableElement(activeElement) || activeElement.tagName === 'SELECT')) {
+		if (id && (hasActiveEditableElement(activeElement, window.document))) {
 			postNotebookMessage<webviewMessages.IOutputInputFocusMessage>('outputInputFocus', { inputFocused: true, id });
 
 			activeElement.addEventListener('blur', () => {
@@ -309,7 +315,7 @@ async function webviewPreloads(ctx: PreloadContext) {
 			return;
 		}
 		const activeElement = window.document.activeElement;
-		if (activeElement && isEditableElement(activeElement)) {
+		if (activeElement && hasActiveEditableElement(activeElement, window.document)) {
 			(activeElement as HTMLInputElement).select();
 		}
 	};
@@ -335,7 +341,7 @@ async function webviewPreloads(ctx: PreloadContext) {
 			return;
 		}
 		const activeElement = window.document.activeElement;
-		if (activeElement && isEditableElement(activeElement)) {
+		if (activeElement && hasActiveEditableElement(activeElement, window.document)) {
 			// Leave for default behavior.
 			return;
 		}
@@ -363,7 +369,7 @@ async function webviewPreloads(ctx: PreloadContext) {
 			return;
 		}
 		const activeElement = window.document.activeElement;
-		if (activeElement && isEditableElement(activeElement)) {
+		if (activeElement && hasActiveEditableElement(activeElement, window.document)) {
 			// The input element will handle this.
 			return;
 		}
@@ -702,7 +708,7 @@ async function webviewPreloads(ctx: PreloadContext) {
 				focusableElement.tabIndex = -1;
 				postNotebookMessage<webviewMessages.IOutputInputFocusMessage>('outputInputFocus', { inputFocused: false, id });
 			} else {
-				const inputFocused = isEditableElement(focusableElement);
+				const inputFocused = hasActiveEditableElement(focusableElement, focusableElement.ownerDocument);
 				postNotebookMessage<webviewMessages.IOutputInputFocusMessage>('outputInputFocus', { inputFocused, id });
 			}