@@ -125,7 +125,11 @@ export class DebugCommands implements IAmDisposable {
 				return this.devTools.spawnForSession(session as DartDebugSessionInformation & { vmServiceUri: string }, { notify, page });
 			} else if (session.session.configuration.noDebug) {
 				vs.window.showInformationMessage("You must start your app with debugging in order to use DevTools.");
+			} else if (session.hasStarted) {
+				vs.window.showInformationMessage("DevTools is not available for an app running in this mode.");
 			} else {
+				// TODO: Remove the last part of this after the next Flutter release (after 3.0) when the appStarted event
+				//       is passed.
 				vs.window.showInformationMessage("This debug session is not ready yet or does not support DevTools.");
 			}
 		}));
@@ -668,6 +672,8 @@ export class DebugCommands implements IAmDisposable {
 			}
 			clearTimeout(timer);
 			this.suppressFlutterWidgetErrors = false;
+		} else if (e.event === "flutter.appStarted") {
+			session.hasStarted = true;
 		}
 	}
 
 
@@ -6,6 +6,7 @@ export class DartDebugSessionInformation {
 	public observatoryUri?: string;
 	public vmServiceUri?: string;
 	public readonly sessionStart: Date = new Date();
+	public hasStarted = false;
 	public hasEnded = false;
 	public progress: { [key: string]: ProgressMessage } = {};
 	public readonly loadedServiceExtensions: VmServiceExtension[] = [];
Original file line number	Diff line number	Diff line change
`@@ -125,7 +125,11 @@ export class DebugCommands implements IAmDisposable {`
`125`	`125`	`return this.devTools.spawnForSession(session as DartDebugSessionInformation & { vmServiceUri: string }, { notify, page });`
`126`	`126`	`} else if (session.session.configuration.noDebug) {`
`127`	`127`	`vs.window.showInformationMessage("You must start your app with debugging in order to use DevTools.");`
	`128`	`+ } else if (session.hasStarted) {`
	`129`	`+ vs.window.showInformationMessage("DevTools is not available for an app running in this mode.");`
`128`	`130`	`} else {`
	`131`	`+ // TODO: Remove the last part of this after the next Flutter release (after 3.0) when the appStarted event`
	`132`	`+ // is passed.`
`129`	`133`	`vs.window.showInformationMessage("This debug session is not ready yet or does not support DevTools.");`
`130`	`134`	`}`
`131`	`135`	`}));`
`@@ -668,6 +672,8 @@ export class DebugCommands implements IAmDisposable {`
`668`	`672`	`}`
`669`	`673`	`clearTimeout(timer);`
`670`	`674`	`this.suppressFlutterWidgetErrors = false;`
	`675`	`+ } else if (e.event === "flutter.appStarted") {`
	`676`	`+ session.hasStarted = true;`
`671`	`677`	`}`
`672`	`678`	`}`
`673`	`679`