diff --git a/ios/chrome/browser/settings/ui_bundled/password/password_details/add_password_coordinator.mm b/ios/chrome/browser/settings/ui_bundled/password/password_details/add_password_coordinator.mm
--- a/ios/chrome/browser/settings/ui_bundled/password/password_details/add_password_coordinator.mm
+++ b/ios/chrome/browser/settings/ui_bundled/password/password_details/add_password_coordinator.mm
@@ -129,6 +129,14 @@

 #pragma mark - UIAdaptivePresentationControllerDelegate

+- (BOOL)presentationControllerShouldDismiss:
+    (UIPresentationController*)presentationController {
+  // Block interactive swipe-to-dismiss while the blocking
+  // LocalReauthenticationViewController is on top of the nav stack, so a
+  // pending LAContext callback cannot be raced by a sheet dismissal.
+  return ![_reauthCoordinator isPresentingBlockingUI];
+}
+
 - (void)presentationControllerDidDismiss:
     (UIPresentationController*)presentationController {
   [self.delegate passwordDetailsTableViewControllerDidFinish:self];
diff --git a/ios/chrome/browser/settings/ui_bundled/password/widget_promo_instructions/widget_promo_instructions_coordinator.mm b/ios/chrome/browser/settings/ui_bundled/password/widget_promo_instructions/widget_promo_instructions_coordinator.mm
--- a/ios/chrome/browser/settings/ui_bundled/password/widget_promo_instructions/widget_promo_instructions_coordinator.mm
+++ b/ios/chrome/browser/settings/ui_bundled/password/widget_promo_instructions/widget_promo_instructions_coordinator.mm
@@ -74,6 +74,14 @@

 #pragma mark - UIAdaptivePresentationControllerDelegate

+- (BOOL)presentationControllerShouldDismiss:
+    (UIPresentationController*)presentationController {
+  // Block interactive swipe-to-dismiss while the blocking
+  // LocalReauthenticationViewController is on top of the nav stack, so a
+  // pending LAContext callback cannot be raced by a sheet dismissal.
+  return ![_reauthCoordinator isPresentingBlockingUI];
+}
+
 - (void)presentationControllerDidDismiss:
     (UIPresentationController*)presentationController {
   [self.delegate removeWidgetPromoInstructionsCoordinator:self];
diff --git a/ios/chrome/browser/settings/ui_bundled/password/reauthentication/local_reauthentication_view_controller.mm b/ios/chrome/browser/settings/ui_bundled/password/reauthentication/local_reauthentication_view_controller.mm
--- a/ios/chrome/browser/settings/ui_bundled/password/reauthentication/local_reauthentication_view_controller.mm
+++ b/ios/chrome/browser/settings/ui_bundled/password/reauthentication/local_reauthentication_view_controller.mm
@@ -30,6 +30,9 @@
     _reauthModule = reauthenticationModule;
     _reauthUponPresentation = reauthUponPresentation;
     self.navigationItem.hidesBackButton = YES;
+    // Defense-in-depth: prevent the hosting modal sheet from being
+    // swipe-dismissed while this blocking VC is presented.
+    self.modalInPresentation = YES;

     // This view does not support large titles as it uses a custom title view.
     self.navigationItem.largeTitleDisplayMode =