feat(mobile): iOS is single-hop only (hide multi-hop until it's reworked)

Single-hop (Fast) now connects on iOS after dropping the second Go runtime.
Multi-hop stays disabled on iOS (it needs the wgnest core, a second Go runtime
in the tunnel extension). Force routeStyle to 'single' on iOS and hide the
Fast/Multi-hop toggle so users don't hit a dead multi-hop path. Android
unchanged (both hops).

Author: TheTrunk

clients/mobile/src/screens/ConnectScreen.tsx

@@ -167,17 +167,22 @@ export function ConnectScreen({
         ) : null}
       </View>
 
-      {/* Fast / Multi-hop toggle — multi-hop is OFF by default (docs/11 §UX). */}
-      <ModeToggle
-        multihop={vpn.multihop}
-        disabled={connected || busy}
-        onFast={() => void vpn.setRouteStyle('single')}
-        onMultihop={() =>
-          void vpn.setRouteStyle(
-            vpn.routeStyle === 'single' ? 'multihop-same-country' : vpn.routeStyle,
-          )
-        }
-      />
+      {/* Fast / Multi-hop toggle — multi-hop is OFF by default (docs/11 §UX).
+          Hidden on iOS: multi-hop is single-hop-only there for now (the wgnest
+          core would be a second Go runtime in the tunnel extension — see
+          MULTIHOP_SUPPORTED in useVpn). */}
+      {Platform.OS !== 'ios' ? (
+        <ModeToggle
+          multihop={vpn.multihop}
+          disabled={connected || busy}
+          onFast={() => void vpn.setRouteStyle('single')}
+          onMultihop={() =>
+            void vpn.setRouteStyle(
+              vpn.routeStyle === 'single' ? 'multihop-same-country' : vpn.routeStyle,
+            )
+          }
+        />
+      ) : null}
 
       {vpn.multihop ? (
         <MultihopControls

clients/mobile/src/state/useVpn.ts

@@ -22,12 +22,19 @@ import {
   status as fetchStatus,
 } from '@cumulusvpn/core';
 import type { EnrollResponse, GatewayInfo, Keypair, RouteStyle, Tier } from '@cumulusvpn/core';
+import { Platform } from 'react-native';
 import {
   CumulusTunnel,
   onTunnelStatus,
   type TunnelState,
   type TunnelStatus,
 } from '../native/CumulusTunnel';
+
+// Multi-hop runs the gomobile wgnest core, which on iOS would be a SECOND Go
+// runtime alongside WireGuardKit's libwg-go in the one Packet Tunnel extension
+// process — two Go runtimes crash it. So multi-hop is disabled on iOS until it
+// is reworked onto a single runtime; iOS is single-hop only.
+const MULTIHOP_SUPPORTED = Platform.OS !== 'ios';
 import {
   discoverFleet,
   groupByCountry,
@@ -359,7 +366,7 @@ export function useVpn(): VpnModel & VpnActions {
         }
         setKeypair(restored);
         setSelectedCode(await loadSelectedCountry());
-        setRouteStyleState(await loadRouteStyle());
+        setRouteStyleState(MULTIHOP_SUPPORTED ? await loadRouteStyle() : 'single');
         setEntryCode(await loadEntryCountry());
         setExitCode(await loadExitCountry());
         setKillSwitchState(await loadKillSwitch());
@@ -721,8 +728,10 @@ export function useVpn(): VpnModel & VpnActions {
   }, []);
 
   const setRouteStyle = useCallback(async (style: RouteStyle): Promise<void> => {
-    setRouteStyleState(style);
-    await saveRouteStyle(style);
+    // iOS is single-hop only (see MULTIHOP_SUPPORTED) — never enter a multihop style.
+    const next = MULTIHOP_SUPPORTED ? style : 'single';
+    setRouteStyleState(next);
+    await saveRouteStyle(next);
   }, []);
 
   const selectEntryCountry = useCallback(async (code: string | null): Promise<void> => {