fix: App hanging when changing passcode on iOS

- Add 300ms delay between authentication and passcode change modals
- Add try-catch to handle authentication cancellation gracefully
- Prevents iOS UI thread hang when two modals open back-to-back

Fixes #6313

Author: DSingh0304

app/lib/constants/localAuthentication.ts

@@ -11,3 +11,6 @@ export const MAX_ATTEMPTS = 6;
 export const TIME_TO_LOCK = 30000;
 
 export const DEFAULT_AUTO_LOCK = 1800;
+
+// Delay between modal transitions to prevent iOS UI thread hang
+export const MODAL_TRANSITION_DELAY_MS = 300;

app/views/ScreenLockConfigView.test.tsx

@@ -0,0 +1,85 @@
+import * as localAuthentication from '../lib/methods/helpers/localAuthentication';
+import { ScreenLockConfigView } from './ScreenLockConfigView';
+
+// Mock localAuthentication helpers used by the component
+jest.mock('../lib/methods/helpers/localAuthentication', () => ({
+	handleLocalAuthentication: jest.fn(),
+	changePasscode: jest.fn(),
+	checkHasPasscode: jest.fn(),
+	supportedBiometryLabel: jest.fn()
+}));
+
+// Mock the database to avoid hitting real DB in constructor.init()
+jest.mock('../lib/database', () => ({
+	servers: {
+		get: jest.fn(() => ({
+			find: jest.fn(() => ({ autoLock: true, autoLockTime: null }))
+		}))
+	}
+}));
+
+// Mock i18n to avoid initialization side-effects in tests
+jest.mock('../i18n', () => ({ 
+	__esModule: true,
+	default: { t: jest.fn((k: string) => k) } 
+}));
+
+describe('ScreenLockConfigView - integration tests', () => {
+	beforeEach(() => {
+		jest.clearAllMocks();
+		jest.useFakeTimers();
+	});
+
+	afterEach(() => {
+		jest.useRealTimers();
+	});
+
+	it('should add 300ms delay between authentication and passcode change (real component)', async () => {
+		const handleLocalAuthenticationMock = (localAuthentication.handleLocalAuthentication as jest.Mock).mockResolvedValue(undefined);
+		const changePasscodeMock = (localAuthentication.changePasscode as jest.Mock).mockResolvedValue(undefined);
+
+		// Create a mock instance of the component
+		const mockInstance: any = new (ScreenLockConfigView as any)({ theme: 'light', server: '', Force_Screen_Lock: false, Force_Screen_Lock_After: 0 });
+		
+		// Set the state we want for this test
+		mockInstance.state = { autoLock: true };
+
+		const promise = mockInstance.changePasscode({ force: false });
+
+		// microtask flush so the handleLocalAuthentication call happens
+		await Promise.resolve();
+		expect(handleLocalAuthenticationMock).toHaveBeenCalledWith(true);
+
+		// changePasscode should NOT be called before the delay
+		expect(changePasscodeMock).not.toHaveBeenCalled();
+
+		// advance timers and flush all promises
+		jest.runAllTimers();
+		await promise;
+
+		expect(changePasscodeMock).toHaveBeenCalledWith({ force: false });
+	});
+
+	it('should return early when authentication is cancelled (real component)', async () => {
+		const handleLocalAuthenticationMock = (localAuthentication.handleLocalAuthentication as jest.Mock).mockRejectedValue(new Error('cancel'));
+		const changePasscodeMock = (localAuthentication.changePasscode as jest.Mock).mockResolvedValue(undefined);
+
+		const mockInstance: any = new (ScreenLockConfigView as any)({ theme: 'light', server: '', Force_Screen_Lock: false, Force_Screen_Lock_After: 0 });
+		mockInstance.state = { autoLock: true };
+
+		await mockInstance.changePasscode({ force: false });		expect(handleLocalAuthenticationMock).toHaveBeenCalledWith(true);
+		expect(changePasscodeMock).not.toHaveBeenCalled();
+	});
+
+	it('should proceed directly to passcode change when autoLock is disabled (real component)', async () => {
+		const handleLocalAuthenticationMock = (localAuthentication.handleLocalAuthentication as jest.Mock);
+		const changePasscodeMock = (localAuthentication.changePasscode as jest.Mock).mockResolvedValue(undefined);
+
+		const mockInstance: any = new (ScreenLockConfigView as any)({ theme: 'light', server: '', Force_Screen_Lock: false, Force_Screen_Lock_After: 0 });
+		mockInstance.state = { autoLock: false };
+
+		await mockInstance.changePasscode({ force: false });		expect(handleLocalAuthenticationMock).not.toHaveBeenCalled();
+		expect(changePasscodeMock).toHaveBeenCalledWith({ force: false });
+	});
+});
+

app/views/ScreenLockConfigView.tsx

@@ -12,7 +12,7 @@ import {
 	supportedBiometryLabel,
 	handleLocalAuthentication
 } from '../lib/methods/helpers/localAuthentication';
-import { BIOMETRY_ENABLED_KEY, DEFAULT_AUTO_LOCK } from '../lib/constants/localAuthentication';
+import { BIOMETRY_ENABLED_KEY, DEFAULT_AUTO_LOCK, MODAL_TRANSITION_DELAY_MS } from '../lib/constants/localAuthentication';
 import { themes } from '../lib/constants/colors';
 import SafeAreaView from '../containers/SafeAreaView';
 import { events, logEvent } from '../lib/methods/helpers/log';
@@ -132,7 +132,15 @@ class ScreenLockConfigView extends React.Component<IScreenLockConfigViewProps, I
 	changePasscode = async ({ force }: { force: boolean }) => {
 		const { autoLock } = this.state;
 		if (autoLock) {
-			await handleLocalAuthentication(true);
+			try {
+				await handleLocalAuthentication(true);
+				// Add a small delay to ensure the first modal is fully closed before opening the next one
+				// This prevents the app from hanging on iOS when two modals open back-to-back
+				await new Promise(resolve => setTimeout(resolve, MODAL_TRANSITION_DELAY_MS));
+			} catch {
+				// User cancelled or authentication failed
+				return;
+			}
 		}
 		logEvent(events.SLC_CHANGE_PASSCODE);
 		await changePasscode({ force });
@@ -296,4 +304,6 @@ const mapStateToProps = (state: IApplicationState) => ({
 	Force_Screen_Lock_After: state.settings.Force_Screen_Lock_After as number
 });
 
+export { ScreenLockConfigView };
+
 export default connect(mapStateToProps)(withTheme(ScreenLockConfigView));

app/views/SecurityPrivacyView.tsx

@@ -6,6 +6,7 @@ import * as List from '../containers/List';
 import SafeAreaView from '../containers/SafeAreaView';
 import I18n from '../i18n';
 import { ANALYTICS_EVENTS_KEY, CRASH_REPORT_KEY } from '../lib/constants/keys';
+import { MODAL_TRANSITION_DELAY_MS } from '../lib/constants/localAuthentication';
 import { useAppSelector } from '../lib/hooks/useAppSelector';
 import useServer from '../lib/methods/useServer';
 import { type SettingsStackParamList } from '../stacks/types';
@@ -59,7 +60,14 @@ const SecurityPrivacyView = ({ navigation }: ISecurityPrivacyViewProps): JSX.Ele
 
 	const navigateToScreenLockConfigView = async () => {
 		if (server?.autoLock) {
-			await handleLocalAuthentication(true);
+			try {
+				await handleLocalAuthentication(true);
+				// Add a small delay to prevent modal conflicts on iOS
+				await new Promise(resolve => setTimeout(resolve, MODAL_TRANSITION_DELAY_MS));
+			} catch {
+				// User cancelled or authentication failed
+				return;
+			}
 		}
 		navigateToScreen('ScreenLockConfigView');
 	};