diff --git a/modules/openapi-generator/src/main/resources/dart/libraries/dio/pubspec.mustache b/modules/openapi-generator/src/main/resources/dart/libraries/dio/pubspec.mustache
index 6e27e3309329..402a81fc610b 100644
--- a/modules/openapi-generator/src/main/resources/dart/libraries/dio/pubspec.mustache
+++ b/modules/openapi-generator/src/main/resources/dart/libraries/dio/pubspec.mustache
@@ -25,6 +25,7 @@ dependencies:
   equatable: '^2.0.7'
 {{/useEquatable}}
 {{#useJsonSerializable}}
+  copy_with_extension: '^7.1.0'
   json_annotation: '^4.9.0'
 {{/useJsonSerializable}}
 {{#useDateLibTimeMachine}}
@@ -38,6 +39,7 @@ dev_dependencies:
 {{/useBuiltValue}}
 {{#useJsonSerializable}}
   build_runner: any
+  copy_with_extension_gen: ^7.1.0
   json_serializable: '^6.9.3'
 {{/useJsonSerializable}}
   test: '^1.16.0'
diff --git a/modules/openapi-generator/src/main/resources/dart/libraries/dio/serialization/json_serializable/class.mustache b/modules/openapi-generator/src/main/resources/dart/libraries/dio/serialization/json_serializable/class.mustache
index 9fad9b10087d..55bf2bb73466 100644
--- a/modules/openapi-generator/src/main/resources/dart/libraries/dio/serialization/json_serializable/class.mustache
+++ b/modules/openapi-generator/src/main/resources/dart/libraries/dio/serialization/json_serializable/class.mustache
@@ -1,3 +1,4 @@
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 {{#useEquatable}}
 import 'package:equatable/src/equatable_utils.dart';
@@ -17,6 +18,7 @@ part '{{classFilename}}.g.dart';
 {{#isDeprecated}}
 @Deprecated('{{{classname}}} has been deprecated')
 {{/isDeprecated}}
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/binary_response/pubspec.yaml b/samples/openapi3/client/petstore/dart-dio/binary_response/pubspec.yaml
index cbfddf172a6c..d0e4ff6fe872 100644
--- a/samples/openapi3/client/petstore/dart-dio/binary_response/pubspec.yaml
+++ b/samples/openapi3/client/petstore/dart-dio/binary_response/pubspec.yaml
@@ -9,9 +9,11 @@ environment:
 
 dependencies:
   dio: '^5.7.0'
+  copy_with_extension: '^7.1.0'
   json_annotation: '^4.9.0'
 
 dev_dependencies:
   build_runner: any
+  copy_with_extension_gen: ^7.1.0
   json_serializable: '^6.9.3'
   test: '^1.16.0'
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/additional_properties_class.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/additional_properties_class.dart
index 8a187d3dc3c0..c0ce2a1090e9 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/additional_properties_class.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/additional_properties_class.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'additional_properties_class.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/all_of_with_single_ref.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/all_of_with_single_ref.dart
index c196447ea5e4..775b58a1fca6 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/all_of_with_single_ref.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/all_of_with_single_ref.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/single_ref_type.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'all_of_with_single_ref.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/animal.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/animal.dart
index 732326357226..c9abb12b9308 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/animal.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/animal.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'animal.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/api_response.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/api_response.dart
index 207cea16eabe..d1b0fa6294ee 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/api_response.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/api_response.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'api_response.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_of_array_of_number_only.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_of_array_of_number_only.dart
index da8de0169296..e0e2d78b95b7 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_of_array_of_number_only.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_of_array_of_number_only.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'array_of_array_of_number_only.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_of_number_only.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_of_number_only.dart
index 4ead761e76f7..9d9e0a197a2f 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_of_number_only.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_of_number_only.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'array_of_number_only.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_test.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_test.dart
index 0968d4b12986..30fdd53ab675 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_test.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/array_test.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/read_only_first.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'array_test.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/capitalization.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/capitalization.dart
index d2bc40f33836..c2327b44f125 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/capitalization.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/capitalization.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'capitalization.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/cat.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/cat.dart
index e2df6f2cc557..05eebe01a67e 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/cat.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/cat.dart
@@ -4,6 +4,7 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/animal.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'cat.g.dart';
@@ -11,6 +12,7 @@ part 'cat.g.dart';
 // ignore_for_file: unused_import
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/category.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/category.dart
index 6d078b06ae20..35718dc06d5b 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/category.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/category.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'category.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/child_with_nullable.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/child_with_nullable.dart
index dcda6f93ba6a..b10f87341a21 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/child_with_nullable.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/child_with_nullable.dart
@@ -4,6 +4,7 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/parent_with_nullable.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'child_with_nullable.g.dart';
@@ -11,6 +12,7 @@ part 'child_with_nullable.g.dart';
 // ignore_for_file: unused_import
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/class_model.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/class_model.dart
index 40b6b45ac3c4..8802de37921e 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/class_model.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/class_model.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'class_model.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/deprecated_object.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/deprecated_object.dart
index 68d1df4016c1..844cda541b83 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/deprecated_object.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/deprecated_object.dart
@@ -3,12 +3,14 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'deprecated_object.g.dart';
 
 
 @Deprecated('DeprecatedObject has been deprecated')
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/dog.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/dog.dart
index deb271b6dc3b..9dd6a37ffcee 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/dog.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/dog.dart
@@ -4,6 +4,7 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/animal.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'dog.g.dart';
@@ -11,6 +12,7 @@ part 'dog.g.dart';
 // ignore_for_file: unused_import
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/enum_arrays.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/enum_arrays.dart
index 632fd933d6e8..b1d9f2942b1d 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/enum_arrays.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/enum_arrays.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'enum_arrays.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/enum_test.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/enum_test.dart
index 563f7038b97f..1563c30bece7 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/enum_test.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/enum_test.dart
@@ -7,11 +7,13 @@ import 'package:openapi/src/model/outer_enum.dart';
 import 'package:openapi/src/model/outer_enum_default_value.dart';
 import 'package:openapi/src/model/outer_enum_integer.dart';
 import 'package:openapi/src/model/outer_enum_integer_default_value.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'enum_test.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/fake_big_decimal_map200_response.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/fake_big_decimal_map200_response.dart
index 1f0f2950a71c..e15b863e9218 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/fake_big_decimal_map200_response.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/fake_big_decimal_map200_response.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'fake_big_decimal_map200_response.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/file_schema_test_class.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/file_schema_test_class.dart
index cde81139a620..43307b721b15 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/file_schema_test_class.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/file_schema_test_class.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/model_file.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'file_schema_test_class.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/foo.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/foo.dart
index 13d38bc30f0d..0f214c4e6ff8 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/foo.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/foo.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'foo.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/foo_get_default_response.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/foo_get_default_response.dart
index e153e16cce1a..6a072cd6634b 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/foo_get_default_response.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/foo_get_default_response.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/foo.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'foo_get_default_response.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/format_test.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/format_test.dart
index a20ba417fa54..1f8c47a279f7 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/format_test.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/format_test.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:dio/dio.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'format_test.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/has_only_read_only.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/has_only_read_only.dart
index ef63a2980c30..d224cbcf15dd 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/has_only_read_only.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/has_only_read_only.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'has_only_read_only.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/health_check_result.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/health_check_result.dart
index 6fd362cdf351..38dcfcacddca 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/health_check_result.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/health_check_result.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'health_check_result.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/map_test.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/map_test.dart
index 59f9377d253a..4a84fa85524f 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/map_test.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/map_test.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'map_test.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/mixed_properties_and_additional_properties_class.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/mixed_properties_and_additional_properties_class.dart
index 458d2bd0534b..63bc9d15ceda 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/mixed_properties_and_additional_properties_class.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/mixed_properties_and_additional_properties_class.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/animal.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'mixed_properties_and_additional_properties_class.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model200_response.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model200_response.dart
index 47609c700da2..bee419bd3ee9 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model200_response.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model200_response.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'model200_response.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_client.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_client.dart
index 8ff470611f22..d6fef8505390 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_client.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_client.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'model_client.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_file.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_file.dart
index cccca0412f46..c34131e2940f 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_file.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_file.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'model_file.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_list.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_list.dart
index 11421881ae57..c99439660de6 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_list.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_list.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'model_list.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_return.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_return.dart
index ea5427115232..c29886c95b7e 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_return.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/model_return.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'model_return.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/name.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/name.dart
index 3d16d98780b3..787a603a97fe 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/name.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/name.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'name.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/nullable_class.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/nullable_class.dart
index 6f6a484551e4..0ffb6db0f33f 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/nullable_class.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/nullable_class.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'nullable_class.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/number_only.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/number_only.dart
index 44e9d41a189d..2e8ff4201b8a 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/number_only.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/number_only.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'number_only.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/object_with_deprecated_fields.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/object_with_deprecated_fields.dart
index 5a36ffb5147e..e2a95d308514 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/object_with_deprecated_fields.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/object_with_deprecated_fields.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/deprecated_object.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'object_with_deprecated_fields.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/order.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/order.dart
index dfbc4f5c5e41..e50a3e70e819 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/order.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/order.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'order.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/outer_composite.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/outer_composite.dart
index a4df9cc62544..66a78af39ebc 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/outer_composite.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/outer_composite.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'outer_composite.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/outer_object_with_enum_property.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/outer_object_with_enum_property.dart
index f78d6b5c8b3d..2708a3d953fd 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/outer_object_with_enum_property.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/outer_object_with_enum_property.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/outer_enum_integer.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'outer_object_with_enum_property.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/parent_with_nullable.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/parent_with_nullable.dart
index bda5847df5ad..e4dce19ff335 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/parent_with_nullable.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/parent_with_nullable.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'parent_with_nullable.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/pet.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/pet.dart
index fdb70f9ce89a..b2674ae99fc6 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/pet.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/pet.dart
@@ -5,11 +5,13 @@
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/category.dart';
 import 'package:openapi/src/model/tag.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'pet.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/read_only_first.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/read_only_first.dart
index 0ec8a7710c60..d276ea105f41 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/read_only_first.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/read_only_first.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'read_only_first.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/special_model_name.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/special_model_name.dart
index 175b6fb274ce..37053ba18f7e 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/special_model_name.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/special_model_name.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'special_model_name.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/tag.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/tag.dart
index abe588b27d6f..ca1d4ed43ebc 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/tag.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/tag.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'tag.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/test_inline_freeform_additional_properties_request.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/test_inline_freeform_additional_properties_request.dart
index 5eda7d48b384..2eb68120e147 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/test_inline_freeform_additional_properties_request.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/test_inline_freeform_additional_properties_request.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'test_inline_freeform_additional_properties_request.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/test_item.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/test_item.dart
index 84e4ee9a79a0..5949d7b92460 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/test_item.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/test_item.dart
@@ -4,11 +4,13 @@
 
 // ignore_for_file: unused_element
 import 'package:openapi/src/model/test_enum.dart';
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'test_item.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/user.dart b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/user.dart
index 56c95cb75f15..15e9b2a2eb61 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/user.dart
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/model/user.dart
@@ -3,11 +3,13 @@
 //
 
 // ignore_for_file: unused_element
+import 'package:copy_with_extension/copy_with_extension.dart';
 import 'package:json_annotation/json_annotation.dart';
 
 part 'user.g.dart';
 
 
+@CopyWith()
 @JsonSerializable(
   checked: true,
   createToJson: true,
diff --git a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/pubspec.yaml b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/pubspec.yaml
index cbfddf172a6c..d0e4ff6fe872 100644
--- a/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/pubspec.yaml
+++ b/samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/pubspec.yaml
@@ -9,9 +9,11 @@ environment:
 
 dependencies:
   dio: '^5.7.0'
+  copy_with_extension: '^7.1.0'
   json_annotation: '^4.9.0'
 
 dev_dependencies:
   build_runner: any
+  copy_with_extension_gen: ^7.1.0
   json_serializable: '^6.9.3'
   test: '^1.16.0'