diff --git a/dwds/debug_extension_mv3/web/cider_connection.dart b/dwds/debug_extension_mv3/web/cider_connection.dart
index 54a78e659..f0e67bb51 100644
--- a/dwds/debug_extension_mv3/web/cider_connection.dart
+++ b/dwds/debug_extension_mv3/web/cider_connection.dart
@@ -8,13 +8,11 @@ library cider_connection;
 import 'dart:convert';
 import 'dart:js_util';
 
-import 'package:dwds/data/debug_info.dart';
 import 'package:js/js.dart';
 
 import 'chrome_api.dart';
 import 'debug_session.dart';
 import 'logger.dart';
-import 'storage.dart';
 
 /// Used to identify messages passed to/from Cider.
 ///
@@ -38,12 +36,9 @@ enum CiderMessageType {
 /// The types must match those defined by ChromeExtensionErrorType in the
 /// Cider extension.
 enum CiderErrorType {
-  chromeError,
   internalError,
   invalidRequest,
-  multipleDartTabs,
-  noDartTab,
-  noWorkspace,
+  noAppId,
 }
 
 const _ciderPortName = 'cider';
@@ -115,36 +110,32 @@ Future<void> _handleMessageFromCider(dynamic message, Port _) async {
   final messageBody = decoded['messageBody'] as String?;
 
   if (messageType == CiderMessageType.startDebugRequest.name) {
-    await _startDebugging(workspaceName: messageBody);
+    await _startDebugging(appId: messageBody);
   } else if (messageType == CiderMessageType.stopDebugRequest.name) {
-    await _stopDebugging(workspaceName: messageBody);
+    await _stopDebugging(appId: messageBody);
   }
 }
 
-Future<void> _startDebugging({String? workspaceName}) async {
-  if (workspaceName == null) {
-    _sendNoWorkspaceError();
+Future<void> _startDebugging({String? appId}) async {
+  if (appId == null) {
+    _sendNoAppIdError();
     return;
   }
-
-  final dartTab = await _findDartTabIdForWorkspace(workspaceName);
-  if (dartTab != null) {
-    // TODO(https://github.com/dart-lang/webdev/issues/2198): When debugging
-    // with Cider, disable debugging with DevTools.
-    await attachDebugger(dartTab, trigger: Trigger.cider);
-  }
+  final tabId = _tabId(appId);
+  // TODO(https://github.com/dart-lang/webdev/issues/2198): When debugging
+  // with Cider, disable debugging with DevTools.
+  await attachDebugger(tabId, trigger: Trigger.cider);
 }
 
-Future<void> _stopDebugging({String? workspaceName}) async {
-  if (workspaceName == null) {
-    _sendNoWorkspaceError();
+Future<void> _stopDebugging({String? appId}) async {
+  if (appId == null) {
+    _sendNoAppIdError();
     return;
   }
+  final tabId = _tabId(appId);
 
-  final dartTab = await _findDartTabIdForWorkspace(workspaceName);
-  if (dartTab == null) return;
   final successfullyDetached = await detachDebugger(
-    dartTab,
+    tabId,
     type: TabType.dartApp,
     reason: DetachReason.canceledByUser,
   );
@@ -159,48 +150,14 @@ Future<void> _stopDebugging({String? workspaceName}) async {
   }
 }
 
-void _sendNoWorkspaceError() {
-  sendErrorMessageToCider(
-    errorType: CiderErrorType.noWorkspace,
-    errorDetails: 'Cannot find a debuggable Dart tab without a workspace',
-  );
+int _tabId(String appId) {
+  final tabId = appId.split('-').last;
+  return int.parse(tabId);
 }
 
-Future<int?> _findDartTabIdForWorkspace(String workspaceName) async {
-  final allTabsInfo = await fetchAllStorageObjectsOfType<DebugInfo>(
-    type: StorageObject.debugInfo,
+void _sendNoAppIdError() {
+  sendErrorMessageToCider(
+    errorType: CiderErrorType.noAppId,
+    errorDetails: 'Cannot find a debuggable Dart tab without an app ID',
   );
-  final dartTabIds = allTabsInfo
-      .where(
-        (debugInfo) => debugInfo.workspaceName == workspaceName,
-      )
-      .map(
-        (info) => info.tabId,
-      )
-      .toList();
-
-  if (dartTabIds.isEmpty) {
-    sendErrorMessageToCider(
-      errorType: CiderErrorType.noDartTab,
-      errorDetails: 'No debuggable Dart tabs found.',
-    );
-    return null;
-  }
-  if (dartTabIds.length > 1) {
-    sendErrorMessageToCider(
-      errorType: CiderErrorType.multipleDartTabs,
-      errorDetails: 'Too many debuggable Dart tabs found.',
-    );
-    return null;
-  }
-  final tabId = dartTabIds.first;
-  if (tabId == null) {
-    sendErrorMessageToCider(
-      errorType: CiderErrorType.chromeError,
-      errorDetails: 'Debuggable Dart tab is null.',
-    );
-    return null;
-  }
-
-  return tabId;
 }
diff --git a/dwds/debug_extension_mv3/web/debug_session.dart b/dwds/debug_extension_mv3/web/debug_session.dart
index 268556c40..fd9e24446 100644
--- a/dwds/debug_extension_mv3/web/debug_session.dart
+++ b/dwds/debug_extension_mv3/web/debug_session.dart
@@ -111,7 +111,10 @@ Future<void> attachDebugger(
   required Trigger trigger,
 }) async {
   // Validate that the tab can be debugged:
-  final tabIsDebuggable = await _validateTabIsDebuggable(dartAppTabId);
+  final tabIsDebuggable = await _validateTabIsDebuggable(
+    dartAppTabId,
+    forwardErrorsToCider: trigger == Trigger.cider,
+  );
   if (!tabIsDebuggable) return;
 
   _tabIdToTrigger[dartAppTabId] = trigger;
@@ -168,12 +171,16 @@ Future<void> clearStaleDebugSession(int tabId) async {
   }
 }
 
-Future<bool> _validateTabIsDebuggable(int dartAppTabId) async {
+Future<bool> _validateTabIsDebuggable(
+  int dartAppTabId, {
+  bool forwardErrorsToCider = false,
+}) async {
   // Check if a debugger is already attached:
   final existingDebuggerLocation = _debuggerLocation(dartAppTabId);
   if (existingDebuggerLocation != null) {
-    await _showWarningNotification(
+    await _showWarning(
       'Already debugging in ${existingDebuggerLocation.displayName}.',
+      forwardToCider: forwardErrorsToCider,
     );
     return false;
   }
@@ -183,7 +190,10 @@ Future<bool> _validateTabIsDebuggable(int dartAppTabId) async {
     tabId: dartAppTabId,
   );
   if (debugInfo == null) {
-    await _showWarningNotification('Not a Dart app.');
+    await _showWarning(
+      'Not a Dart app.',
+      forwardToCider: forwardErrorsToCider,
+    );
     return false;
   }
   // Determine if there are multiple apps in the tab:
@@ -192,8 +202,9 @@ Future<bool> _validateTabIsDebuggable(int dartAppTabId) async {
     tabId: dartAppTabId,
   );
   if (multipleApps != null) {
-    await _showWarningNotification(
+    await _showWarning(
       'Dart debugging is not supported in a multi-app environment.',
+      forwardToCider: forwardErrorsToCider,
     );
     return false;
   }
@@ -692,6 +703,21 @@ Future<bool> _sendAuthRequest(String authUrl) async {
   return responseBody.contains('Dart Debug Authentication Success!');
 }
 
+Future<bool> _showWarning(
+  String message, {
+  bool forwardToCider = false,
+}) {
+  if (forwardToCider) {
+    sendErrorMessageToCider(
+      errorType: CiderErrorType.invalidRequest,
+      errorDetails: message,
+    );
+    return Future.value(true);
+  } else {
+    return _showWarningNotification(message);
+  }
+}
+
 Future<bool> _showWarningNotification(String message) {
   final completer = Completer<bool>();
   chrome.notifications.create(