iOS: bound safe_area()'s boot-path dispatch_sync to avoid a launch deadlock

ios/MobViewModel.swift

@@ -7,6 +7,13 @@ import Combine
 @objc public class MobViewModel: NSObject, ObservableObject {
     @objc public static let shared = MobViewModel()
 
+    // How long to wait for BEAM boot to produce a first screen before treating
+    // it as stuck. An indefinite spinner and a persistent error look identical
+    // to "frozen" from the outside — this turns a silent hang into an explicit,
+    // diagnosable state instead of leaving the app on the black startup screen
+    // forever (seen: App Store review reporting an indefinite/blank launch).
+    private static let bootWatchdogSeconds: TimeInterval = 15
+
     @Published public var root: MobNode?
     /// Increments on every setRoot call; views use onChange(of: rootVersion) to
     /// trigger withAnimation rather than watching root directly (root identity
@@ -25,6 +32,20 @@ import Combine
     /// Non-nil when a fatal startup error has occurred; the error screen stalls here.
     @Published public var startupError: String?
 
+    override init() {
+        super.init()
+        DispatchQueue.main.asyncAfter(deadline: .now() + Self.bootWatchdogSeconds) { [weak self] in
+            guard let self, self.root == nil, self.startupError == nil else { return }
+            let info = Bundle.main.infoDictionary
+            let shortVersion = (info?["CFBundleShortVersionString"] as? String) ?? "?"
+            let build = (info?["CFBundleVersion"] as? String) ?? "?"
+            self.startupError =
+                "Startup is taking longer than expected — this usually means a " +
+                "native call blocked the main thread during boot. Please force-quit " +
+                "and relaunch the app.\n\nVersion \(shortVersion) (\(build))"
+        }
+    }
+
     @objc public func setRoot(_ node: MobNode?, transition: String) {
         DispatchQueue.main.async {
             self.transition = transition

ios/mob_nif.m

@@ -1827,10 +1827,19 @@ static ERL_NIF_TERM nif_device_keep_awake(ErlNifEnv *env, int argc, const ERL_NI
 // ── NIF: safe_area/0 ─────────────────────────────────────────────────────────
 // Returns {Top, Right, Bottom, Left} in logical points (not pixels).
 // Must read UIWindow.safeAreaInsets on the main thread.
-
+//
+// Called from Mob.Screen.init/1 — i.e. on the boot path, before the first
+// screen ever mounts. A plain dispatch_sync here is a deadlock risk: if the
+// main thread hasn't reached an idle run-loop tick yet (observed during
+// scene-attachment on iPad, including the compatibility-mode window an
+// iPhone-only app runs in there), this blocks the BEAM boot thread forever —
+// the app never finishes launching. Bound the wait and fall back to zero
+// insets on timeout: a screen with wrong insets once is a far smaller bug
+// than an app that never boots.
 static ERL_NIF_TERM nif_safe_area(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
     __block UIEdgeInsets insets = UIEdgeInsetsZero;
-    dispatch_sync(dispatch_get_main_queue(), ^{
+    dispatch_semaphore_t done = dispatch_semaphore_create(0);
+    dispatch_async(dispatch_get_main_queue(), ^{
       UIWindow *window = nil;
       for (UIScene *scene in [UIApplication sharedApplication].connectedScenes) {
           if ([scene isKindOfClass:[UIWindowScene class]]) {
@@ -1841,7 +1850,10 @@ static ERL_NIF_TERM nif_safe_area(ErlNifEnv *env, int argc, const ERL_NIF_TERM a
       }
       if (window)
           insets = window.safeAreaInsets;
+      dispatch_semaphore_signal(done);
     });
+    dispatch_time_t deadline = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC));
+    dispatch_semaphore_wait(done, deadline);
     return enif_make_tuple4(
         env, enif_make_double(env, insets.top), enif_make_double(env, insets.right),
         enif_make_double(env, insets.bottom), enif_make_double(env, insets.left));
@@ -6327,7 +6339,7 @@ static ERL_NIF_TERM nif_vendor_usb_close(ErlNifEnv *env, int argc, const ERL_NIF
     {"register_tap", 1, nif_register_tap, 0},
     {"clear_taps", 0, nif_clear_taps, 0},
     {"exit_app", 0, nif_exit_app, 0},
-    {"safe_area", 0, nif_safe_area, 0},
+    {"safe_area", 0, nif_safe_area, ERL_NIF_DIRTY_JOB_IO_BOUND},
     {"haptic", 1, nif_haptic, 0},
     {"torch", 1, nif_torch, 0},
     {"clipboard_put", 1, nif_clipboard_put, 0},