diff --git a/packages/firebase_ai/firebase_ai/lib/src/content.dart b/packages/firebase_ai/firebase_ai/lib/src/content.dart
index ac47ed996069..b2661d05c880 100644
--- a/packages/firebase_ai/firebase_ai/lib/src/content.dart
+++ b/packages/firebase_ai/firebase_ai/lib/src/content.dart
@@ -13,7 +13,9 @@
 // limitations under the License.
 
 import 'dart:convert';
+import 'dart:developer';
 import 'dart:typed_data';
+
 import 'error.dart';
 
 /// The base structured datatype containing multi-part content of a message.
@@ -81,7 +83,14 @@ Content parseContent(Object jsonObject) {
 
 /// Parse the [Part] from json object.
 Part parsePart(Object? jsonObject) {
-  if (jsonObject is Map && jsonObject.containsKey('functionCall')) {
+  if (jsonObject is! Map<String, Object?>) {
+    log('Unhandled part format: $jsonObject');
+    return UnknownPart(<String, Object?>{
+      'unhandled': jsonObject,
+    });
+  }
+
+  if (jsonObject.containsKey('functionCall')) {
     final functionCall = jsonObject['functionCall'];
     if (functionCall is Map &&
         functionCall.containsKey('name') &&
@@ -104,13 +113,12 @@ Part parsePart(Object? jsonObject) {
       }
     } =>
       FileData(mimeType, fileUri),
-    {
-      'functionResponse': {'name': String _, 'response': Map<String, Object?> _}
-    } =>
-      throw UnimplementedError('FunctionResponse part not yet supported'),
     {'inlineData': {'mimeType': String mimeType, 'data': String bytes}} =>
       InlineDataPart(mimeType, base64Decode(bytes)),
-    _ => throw unhandledFormat('Part', jsonObject),
+    _ => () {
+        log('unhandled part format: $jsonObject');
+        return UnknownPart(jsonObject);
+      }(),
   };
 }
 
@@ -120,6 +128,18 @@ sealed class Part {
   Object toJson();
 }
 
+/// A [Part] that contains unparsable data.
+final class UnknownPart implements Part {
+  // ignore: public_member_api_docs
+  UnknownPart(this.data);
+
+  /// The unparsed data.
+  final Map<String, Object?> data;
+
+  @override
+  Object toJson() => data;
+}
+
 /// A [Part] with the text content.
 final class TextPart implements Part {
   // ignore: public_member_api_docs
diff --git a/packages/firebase_ai/firebase_ai/test/content_test.dart b/packages/firebase_ai/firebase_ai/test/content_test.dart
index fc2957d89d73..59a68bd6a198 100644
--- a/packages/firebase_ai/firebase_ai/test/content_test.dart
+++ b/packages/firebase_ai/firebase_ai/test/content_test.dart
@@ -16,7 +16,6 @@ import 'dart:convert';
 import 'dart:typed_data';
 
 import 'package:firebase_ai/src/content.dart';
-import 'package:firebase_ai/src/error.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 // Mock google_ai classes (if needed)
@@ -192,24 +191,36 @@ void main() {
       expect(inlineData.bytes, [1, 2, 3]);
     });
 
-    test('throws UnimplementedError for functionResponse', () {
+    test('returns UnknownPart for functionResponse', () {
       final json = {
         'functionResponse': {'name': 'test', 'response': {}}
       };
-      expect(() => parsePart(json), throwsA(isA<FirebaseAISdkException>()));
+      final result = parsePart(json);
+      expect(result, isA<UnknownPart>());
+      final unknownPart = result as UnknownPart;
+      expect(unknownPart.data, json);
     });
 
-    test('throws unhandledFormat for invalid JSON', () {
+    test('returns UnknownPart for invalid JSON', () {
       final json = {'invalid': 'data'};
-      expect(() => parsePart(json), throwsA(isA<Exception>()));
+      final result = parsePart(json);
+      expect(result, isA<UnknownPart>());
+      final unknownPart = result as UnknownPart;
+      expect(unknownPart.data, json);
     });
 
-    test('throws unhandledFormat for null input', () {
-      expect(() => parsePart(null), throwsA(isA<Exception>()));
+    test('returns UnknownPart for null input', () {
+      final result = parsePart(null);
+      expect(result, isA<UnknownPart>());
+      final unknownPart = result as UnknownPart;
+      expect(unknownPart.data, {'unhandled': null});
     });
 
-    test('throws unhandledFormat for empty map', () {
-      expect(() => parsePart({}), throwsA(isA<Exception>()));
+    test('returns UnknownPart for empty map', () {
+      final result = parsePart({});
+      expect(result, isA<UnknownPart>());
+      final unknownPart = result as UnknownPart;
+      expect(unknownPart.data, {'unhandled': {}});
     });
   });
 }
diff --git a/packages/firebase_ai/firebase_ai/test/utils/matchers.dart b/packages/firebase_ai/firebase_ai/test/utils/matchers.dart
index 39c23188b677..aa085da49475 100644
--- a/packages/firebase_ai/firebase_ai/test/utils/matchers.dart
+++ b/packages/firebase_ai/firebase_ai/test/utils/matchers.dart
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 import 'package:firebase_ai/firebase_ai.dart';
+import 'package:firebase_ai/src/content.dart';
 import 'package:http/http.dart' as http;
 import 'package:matcher/matcher.dart';
 
@@ -33,6 +34,8 @@ Matcher matchesPart(Part part) => switch (part) {
         isA<FunctionResponse>()
             .having((p) => p.name, 'name', name)
             .having((p) => p.response, 'args', response),
+      UnknownPart(data: final data) =>
+        isA<UnknownPart>().having((p) => p.data, 'data', data),
     };
 
 Matcher matchesContent(Content content) => isA<Content>()
diff --git a/packages/firebase_vertexai/firebase_vertexai/test/content_test.dart b/packages/firebase_vertexai/firebase_vertexai/test/content_test.dart
index 21db7a03f852..59a68bd6a198 100644
--- a/packages/firebase_vertexai/firebase_vertexai/test/content_test.dart
+++ b/packages/firebase_vertexai/firebase_vertexai/test/content_test.dart
@@ -16,8 +16,6 @@ import 'dart:convert';
 import 'dart:typed_data';
 
 import 'package:firebase_ai/src/content.dart';
-import 'package:firebase_vertexai/firebase_vertexai.dart'
-    show VertexAISdkException;
 import 'package:flutter_test/flutter_test.dart';
 
 // Mock google_ai classes (if needed)
@@ -193,24 +191,36 @@ void main() {
       expect(inlineData.bytes, [1, 2, 3]);
     });
 
-    test('throws UnimplementedError for functionResponse', () {
+    test('returns UnknownPart for functionResponse', () {
       final json = {
         'functionResponse': {'name': 'test', 'response': {}}
       };
-      expect(() => parsePart(json), throwsA(isA<VertexAISdkException>()));
+      final result = parsePart(json);
+      expect(result, isA<UnknownPart>());
+      final unknownPart = result as UnknownPart;
+      expect(unknownPart.data, json);
     });
 
-    test('throws unhandledFormat for invalid JSON', () {
+    test('returns UnknownPart for invalid JSON', () {
       final json = {'invalid': 'data'};
-      expect(() => parsePart(json), throwsA(isA<Exception>()));
+      final result = parsePart(json);
+      expect(result, isA<UnknownPart>());
+      final unknownPart = result as UnknownPart;
+      expect(unknownPart.data, json);
     });
 
-    test('throws unhandledFormat for null input', () {
-      expect(() => parsePart(null), throwsA(isA<Exception>()));
+    test('returns UnknownPart for null input', () {
+      final result = parsePart(null);
+      expect(result, isA<UnknownPart>());
+      final unknownPart = result as UnknownPart;
+      expect(unknownPart.data, {'unhandled': null});
     });
 
-    test('throws unhandledFormat for empty map', () {
-      expect(() => parsePart({}), throwsA(isA<Exception>()));
+    test('returns UnknownPart for empty map', () {
+      final result = parsePart({});
+      expect(result, isA<UnknownPart>());
+      final unknownPart = result as UnknownPart;
+      expect(unknownPart.data, {'unhandled': {}});
     });
   });
 }
diff --git a/packages/firebase_vertexai/firebase_vertexai/test/utils/matchers.dart b/packages/firebase_vertexai/firebase_vertexai/test/utils/matchers.dart
index 28e72e65a4cb..8daf0b12abf8 100644
--- a/packages/firebase_vertexai/firebase_vertexai/test/utils/matchers.dart
+++ b/packages/firebase_vertexai/firebase_vertexai/test/utils/matchers.dart
@@ -11,6 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+import 'package:firebase_ai/src/content.dart';
 import 'package:firebase_vertexai/firebase_vertexai.dart';
 import 'package:http/http.dart' as http;
 import 'package:matcher/matcher.dart';
@@ -33,6 +34,8 @@ Matcher matchesPart(Part part) => switch (part) {
         isA<FunctionResponse>()
             .having((p) => p.name, 'name', name)
             .having((p) => p.response, 'args', response),
+      UnknownPart(data: final data) =>
+        isA<UnknownPart>().having((p) => p.data, 'data', data),
     };
 
 Matcher matchesContent(Content content) => isA<Content>()