diff --git a/FirebaseInAppMessaging/Sources/Runtime/FIRIAMActionURLFollower.m b/FirebaseInAppMessaging/Sources/Runtime/FIRIAMActionURLFollower.m
index 840937c1be5..e80a4f29f48 100644
--- a/FirebaseInAppMessaging/Sources/Runtime/FIRIAMActionURLFollower.m
+++ b/FirebaseInAppMessaging/Sources/Runtime/FIRIAMActionURLFollower.m
@@ -175,8 +175,9 @@ - (BOOL)followURLWithContinueUserActivity:(NSURL *)url {
     FIRLogDebug(kFIRLoggerInAppMessaging, @"I-IAM240004",
                 @"App delegate responds to application:continueUserActivity:restorationHandler:."
                  "Simulating action url opening from a web browser.");
-    NSUserActivity *userActivity =
-        [[NSUserActivity alloc] initWithActivityType:NSUserActivityTypeBrowsingWeb];
+    // Use string literal to ensure compatibility with Xcode 26 and iOS 18
+    NSString *browsingWebType = @"NSUserActivityTypeBrowsingWeb";
+    NSUserActivity *userActivity = [[NSUserActivity alloc] initWithActivityType:browsingWebType];
     userActivity.webpageURL = url;
     BOOL handled = [self.appDelegate application:self.mainApplication
                             continueUserActivity:userActivity
diff --git a/FirebaseInAppMessaging/Tests/Unit/FIRIAMActionUrlFollowerTests.m b/FirebaseInAppMessaging/Tests/Unit/FIRIAMActionUrlFollowerTests.m
index 9a0b56e26e5..6fe8e363402 100644
--- a/FirebaseInAppMessaging/Tests/Unit/FIRIAMActionUrlFollowerTests.m
+++ b/FirebaseInAppMessaging/Tests/Unit/FIRIAMActionUrlFollowerTests.m
@@ -84,8 +84,9 @@ - (void)testUniversalLinkHandlingReturnYES {
                          continueUserActivity:[OCMArg checkWithBlock:^BOOL(id userActivity) {
                            // verifying the type and url field for the userActivity object
                            NSUserActivity *activity = (NSUserActivity *)userActivity;
-                           return [activity.activityType
-                                      isEqualToString:NSUserActivityTypeBrowsingWeb] &&
+                           // Use string literal to ensure compatibility with Xcode 26 and iOS 18
+                           NSString *browsingWebType = @"NSUserActivityTypeBrowsingWeb";
+                           return [activity.activityType isEqualToString:browsingWebType] &&
                                   [activity.webpageURL isEqual:url];
                          }]
                            restorationHandler:[OCMArg any]])
diff --git a/FirebaseMessaging/CHANGELOG.md b/FirebaseMessaging/CHANGELOG.md
index 00b746df27a..f2756c5ce0a 100644
--- a/FirebaseMessaging/CHANGELOG.md
+++ b/FirebaseMessaging/CHANGELOG.md
@@ -1,3 +1,8 @@
+# 12.1.0
+- [fixed] Fix Xcode 26 crash from missing `NSUserActivityTypeBrowsingWeb`
+  symbol. Note that this fix isn't in the 12.1.0 zip and Carthage
+  distributions, but will be included from 12.2.0 onwards. (#15159)
+
 # 11.14.0
 - [fixed] Fix a potential SQL injection issue. (#14846).
 
diff --git a/FirebaseMessaging/Sources/FIRMessaging.m b/FirebaseMessaging/Sources/FIRMessaging.m
index e2bb09b098c..3eb83e94e5f 100644
--- a/FirebaseMessaging/Sources/FIRMessaging.m
+++ b/FirebaseMessaging/Sources/FIRMessaging.m
@@ -400,8 +400,9 @@ - (void)handleIncomingLinkIfNeededFromMessage:(NSDictionary *)message {
   // if they haven't implemented it.
   if ([NSUserActivity class] != nil &&
       [appDelegate respondsToSelector:continueUserActivitySelector]) {
-    NSUserActivity *userActivity =
-        [[NSUserActivity alloc] initWithActivityType:NSUserActivityTypeBrowsingWeb];
+    // Use string literal to ensure compatibility with Xcode 26 and iOS 18
+    NSString *browsingWebType = @"NSUserActivityTypeBrowsingWeb";
+    NSUserActivity *userActivity = [[NSUserActivity alloc] initWithActivityType:browsingWebType];
     userActivity.webpageURL = url;
     [appDelegate application:application
         continueUserActivity:userActivity