mainThreadDebugService: proper listeners separation

src/vs/workbench/api/electron-browser/mainThreadDebugService.ts

@@ -35,8 +35,11 @@ export class MainThreadDebugService implements MainThreadDebugServiceShape, IDeb
 	) {
 		this._proxy = extHostContext.getProxy(ExtHostContext.ExtHostDebugService);
 		this._toDispose = [];
-		this._toDispose.push(debugService.onWillNewSession(session => {
+		this._toDispose.push(debugService.onDidNewSession(session => {
 			this._proxy.$acceptDebugSessionStarted(<DebugSessionUUID>session.getId(), session.configuration.type, session.getName(false));
+		}));
+		this._toDispose.push(debugService.onWillNewSession(session => {
+			// Need to start listening early to new session events because a custom event can come while a session is initialising
 			this._toDispose.push(session.onDidCustomEvent(event => {
 				if (event && event.sessionId) {
 					this._proxy.$acceptDebugSessionCustomEvent(event.sessionId, session.configuration.type, session.configuration.name, event);