fix: sync default tags to native layer

src/Sentry/Platforms/Android/SentrySdk.cs

@@ -95,8 +95,9 @@ private static void InitSentryAndroidSdk(SentryOptions options)
                 o.CacheDirPath = Path.Combine(cacheDirectoryPath, "android");
             }
 
-            // NOTE: Tags in options.DefaultTags should not be passed down, because we already call SetTag on each
-            //       one when sending events, which is relayed through the scope observer.
+            // NOTE: options.DefaultTags are forwarded to the scope observer in SentrySdk.InitHub so the
+            //       Android SDK attaches them to native crashes. The Enricher continues to apply them to
+            //       managed events at send time.
 
             if (options.HttpProxy is System.Net.WebProxy proxy)
             {

src/Sentry/Platforms/Cocoa/SentrySdk.cs

@@ -50,8 +50,9 @@ private static void InitSentryCocoaSdk(SentryOptions options)
         // NOTE: options.CacheDirectoryPath - No option for this in Sentry Cocoa, but caching is still enabled
         // https://github.com/getsentry/sentry-cocoa/issues/1051
 
-        // NOTE: Tags in options.DefaultTags should not be passed down, because we already call SetTag on each
-        //       one when sending events, which is relayed through the scope observer.
+        // NOTE: options.DefaultTags are forwarded to the scope observer in SentrySdk.InitHub so the
+        //       Cocoa SDK attaches them to native crashes. The Enricher continues to apply them to
+        //       managed events at send time.
 
         if (options.BeforeBreadcrumbInternal is { } beforeBreadcrumb)
         {

src/Sentry/SentrySdk.cs

@@ -91,6 +91,18 @@ internal static IHub InitHub(SentryOptions options)
         }
         options.PostInitCallbacks.Clear();
 
+        // Default tags are applied per-event by the Enricher to events going through the .NET pipeline,
+        // but native crashes are captured and uploaded by the native SDK without going through that pipeline.
+        // Forward them to the scope observer so the native layer attaches them to crash reports.
+        // Bypassing the .NET scope keeps scope.Tags identical between native and non-native apps.
+        if (options is { EnableScopeSync: true, ScopeObserver: { } observer } && options.DefaultTags.Count > 0)
+        {
+            foreach (var tag in options.DefaultTags)
+            {
+                observer.SetTag(tag.Key, tag.Value);
+            }
+        }
+
         // Platform specific check for profiler misconfiguration.
 #if __IOS__
         // No user-facing warning necessary - the integration is part of InitSentryCocoaSdk().

test/Sentry.Tests/SentrySdkTests.cs

@@ -967,6 +967,52 @@ public void InitHub_GlobalModeOff_NoWarningOrErrorLogged()
     }
 #endif
 
+    [Fact]
+    public void InitHub_DefaultTagsWithScopeSync_RelayedToScopeObserver()
+    {
+        // Arrange
+        var observer = Substitute.For<IScopeObserver>();
+        var options = new SentryOptions
+        {
+            Dsn = ValidDsn,
+            ScopeObserver = observer,
+            EnableScopeSync = true,
+            BackgroundWorker = Substitute.For<IBackgroundWorker>(),
+            InitNativeSdks = false,
+        };
+        options.DefaultTags["env"] = "production";
+        options.DefaultTags["region"] = "us-east-1";
+
+        // Act
+        SentrySdk.InitHub(options);
+
+        // Assert
+        observer.Received(1).SetTag("env", "production");
+        observer.Received(1).SetTag("region", "us-east-1");
+    }
+
+    [Fact]
+    public void InitHub_DefaultTagsWithoutScopeSync_NotRelayedToScopeObserver()
+    {
+        // Arrange
+        var observer = Substitute.For<IScopeObserver>();
+        var options = new SentryOptions
+        {
+            Dsn = ValidDsn,
+            ScopeObserver = observer,
+            EnableScopeSync = false,
+            BackgroundWorker = Substitute.For<IBackgroundWorker>(),
+            InitNativeSdks = false,
+        };
+        options.DefaultTags["env"] = "production";
+
+        // Act
+        SentrySdk.InitHub(options);
+
+        // Assert
+        observer.DidNotReceive().SetTag(Arg.Any<string>(), Arg.Any<string>());
+    }
+
     [Fact]
     public void InitHub_DebugEnabled_DebugLogsLogged()
     {