diff --git a/android/src/main/kotlin/com/example/confidence_flutter_sdk/ConfidenceFlutterSdkPlugin.kt b/android/src/main/kotlin/com/example/confidence_flutter_sdk/ConfidenceFlutterSdkPlugin.kt
index 0ddfc95..e4e19bb 100644
--- a/android/src/main/kotlin/com/example/confidence_flutter_sdk/ConfidenceFlutterSdkPlugin.kt
+++ b/android/src/main/kotlin/com/example/confidence_flutter_sdk/ConfidenceFlutterSdkPlugin.kt
@@ -187,6 +187,11 @@ private fun Map<String, Any>.convert(): ConfidenceValue {
     "double" -> return ConfidenceValue.Double(this["value"] as Double)
     "bool" -> return ConfidenceValue.Boolean(this["value"] as Boolean)
     "int" -> return ConfidenceValue.Integer(this["value"] as Int)
+    // Dart could not map this type (a DateTime, a null, a custom object) and
+    // has already sent `value.toString()`. Keep that string rather than
+    // throwing: `track` is fire-and-forget from Dart, so an exception here
+    // would surface only as a logged handler error while the event is lost.
+    "unknown" -> return ConfidenceValue.String(this["value"]?.toString() ?: "")
     "list" -> {
       val list = (this["value"] as List<Map<String, Any>>).map { it.convert() }
       return ConfidenceValue.List(list)
diff --git a/ios/confidence_flutter_sdk/Sources/confidence_flutter_sdk/ConfidenceFlutterSdkPlugin.swift b/ios/confidence_flutter_sdk/Sources/confidence_flutter_sdk/ConfidenceFlutterSdkPlugin.swift
index 85346c4..e5a8c0b 100644
--- a/ios/confidence_flutter_sdk/Sources/confidence_flutter_sdk/ConfidenceFlutterSdkPlugin.swift
+++ b/ios/confidence_flutter_sdk/Sources/confidence_flutter_sdk/ConfidenceFlutterSdkPlugin.swift
@@ -259,7 +259,17 @@ func convertValue(_ type: String, _ value: Any) -> ConfidenceValue {
         })
     case "string":
         return ConfidenceValue.init(string: value as! String)
+    case "unknown":
+        // Dart could not map this type (a DateTime, a null, a custom object)
+        // and has already sent `value.toString()`. Keep that string: coercing
+        // it to a number would publish a wrong value with nothing to show the
+        // caller their data was discarded.
+        return ConfidenceValue.init(string: value as? String ?? String(describing: value))
     default:
-        return ConfidenceValue.init(integer: 0)
+        // An unrecognised type marker means the Dart and native sides have
+        // drifted. Preserve the value as a string and make the mismatch
+        // visible rather than silently publishing a number.
+        NSLog("%@", "Confidence SDK: unsupported value type '\(type)', publishing it as a string")
+        return ConfidenceValue.init(string: value as? String ?? String(describing: value))
     }
 }
diff --git a/lib/confidence_flutter_sdk_method_channel.dart b/lib/confidence_flutter_sdk_method_channel.dart
index 6555388..8c1216b 100644
--- a/lib/confidence_flutter_sdk_method_channel.dart
+++ b/lib/confidence_flutter_sdk_method_channel.dart
@@ -160,6 +160,14 @@ class MethodChannelConfidenceFlutterSdk extends ConfidenceFlutterSdkPlatform {
     return value!;
   }
 
+  /// Wraps [value] in the `{'type': ..., 'value': ...}` envelope the native
+  /// plugins decode.
+  ///
+  /// Anything Confidence has no type for — a `DateTime`, a `null`, a custom
+  /// object — is sent as `type: 'unknown'` carrying `value.toString()`. Both
+  /// native sides publish that as a string. They must not coerce it to a
+  /// number or drop it: the caller's data would be silently wrong with
+  /// nothing to indicate it.
   Map<String, dynamic> toTypedValue(dynamic value) {
     if (value is int) {
       return {'type': 'int', 'value': value};
diff --git a/test/confidence_flutter_sdk_method_channel_test.dart b/test/confidence_flutter_sdk_method_channel_test.dart
index ac16352..3f128a2 100644
--- a/test/confidence_flutter_sdk_method_channel_test.dart
+++ b/test/confidence_flutter_sdk_method_channel_test.dart
@@ -111,4 +111,47 @@ void main() {
     expect(methodCalls, hasLength(1));
     expect(methodCalls.single.method, 'track');
   });
+
+  // Values Confidence has no type for must reach native as a stringified
+  // 'unknown', never as a number and never dropped. The native halves of this
+  // contract (iOS convertValue, Android convert) cannot be exercised from
+  // Dart, so what is pinned here is the wire format they rely on.
+  group('unsupported tracking values keep their value', () {
+    Map<String, dynamic> trackedData() {
+      final args = methodCalls.single.arguments as Map<Object?, Object?>;
+      return (args['data'] as Map<Object?, Object?>)
+          .map((k, v) => MapEntry(k as String, v));
+    }
+
+    test('a DateTime is stringified, not coerced to a number', () {
+      final now = DateTime.utc(2026, 9, 7, 12, 34, 56);
+      platform.track('my_event', {'ts': now});
+
+      final ts = trackedData()['ts'] as Map<Object?, Object?>;
+      expect(ts['type'], 'unknown');
+      expect(ts['value'], now.toString());
+      expect(ts['value'], isNot(0));
+    });
+
+    test('a null keeps a value and the key is not dropped', () {
+      platform.track('my_event', {'maybe': null});
+
+      final data = trackedData();
+      expect(data.containsKey('maybe'), isTrue,
+          reason: 'the key must survive so the caller can see what was sent');
+      final maybe = data['maybe'] as Map<Object?, Object?>;
+      expect(maybe['type'], 'unknown');
+      expect(maybe['value'], isNot(0));
+    });
+
+    test('supported types are unaffected', () {
+      platform.track('my_event', {'n': 7, 's': 'x', 'b': true, 'd': 1.5});
+
+      final data = trackedData();
+      expect((data['n'] as Map<Object?, Object?>)['type'], 'int');
+      expect((data['s'] as Map<Object?, Object?>)['type'], 'string');
+      expect((data['b'] as Map<Object?, Object?>)['type'], 'bool');
+      expect((data['d'] as Map<Object?, Object?>)['type'], 'double');
+    });
+  });
 }