diff --git a/modules/openapi-generator/src/main/resources/dart2/api.mustache b/modules/openapi-generator/src/main/resources/dart2/api.mustache
index 2ce04e81f0eb..e40ebac39408 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api.mustache
@@ -86,7 +86,6 @@ class {{{classname}}} {
       {{/headerParams}}
     {{/hasHeaderParams}}
 
-    const authNames = <String>[{{#authMethods}}'{{{name}}}'{{^-last}}, {{/-last}}{{/authMethods}}];
     const contentTypes = <String>[{{#prioritizedContentTypes}}'{{{mediaType}}}'{{^-last}}, {{/-last}}{{/prioritizedContentTypes}}];
 
     {{#isMultipart}}
@@ -129,7 +128,6 @@ class {{{classname}}} {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/modules/openapi-generator/src/main/resources/dart2/api_client.mustache b/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
index 92846fc4b910..8eae959e3e5d 100644
--- a/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
+++ b/modules/openapi-generator/src/main/resources/dart2/api_client.mustache
@@ -1,27 +1,7 @@
 {{>header}}
 {{>part_of}}
 class ApiClient {
-  ApiClient({this.basePath = '{{{basePath}}}'}) {
-  {{#hasAuthMethods}}
-    // Setup authentications (key: authentication name, value: authentication).
-  {{#authMethods}}
-  {{#isBasic}}
-  {{#isBasicBasic}}
-    _authentications[r'{{{name}}}'] = HttpBasicAuth();
-  {{/isBasicBasic}}
-  {{#isBasicBearer}}
-    _authentications[r'{{{name}}}'] = HttpBearerAuth();
-  {{/isBasicBearer}}
-  {{/isBasic}}
-  {{#isApiKey}}
-    _authentications[r'{{{name}}}'] = ApiKeyAuth({{#isKeyInCookie}}'cookie'{{/isKeyInCookie}}{{^isKeyInCookie}}{{#isKeyInHeader}}'header'{{/isKeyInHeader}}{{^isKeyInHeader}}'query'{{/isKeyInHeader}}{{/isKeyInCookie}}, '{{{keyParamName}}}');
-  {{/isApiKey}}
-  {{#isOAuth}}
-    _authentications[r'{{{name}}}'] = OAuth();
-  {{/isOAuth}}
-  {{/authMethods}}
-  {{/hasAuthMethods}}
-  }
+  ApiClient({this.basePath = '{{{basePath}}}', this.authentication});
 
   final String basePath;
 
@@ -38,7 +18,7 @@ class ApiClient {
   }
 
   final _defaultHeaderMap = <String, String>{};
-  final _authentications = <String, Authentication>{};
+  final Authentication? authentication;
 
   void addDefaultHeader(String key, String value) {
      _defaultHeaderMap[key] = value;
@@ -46,15 +26,6 @@ class ApiClient {
 
   Map<String,String> get defaultHeaderMap => _defaultHeaderMap;
 
-  /// Returns an unmodifiable [Map] of the authentications, since none should be added
-  /// or deleted.
-  Map<String, Authentication> get authentications => Map.unmodifiable(_authentications);
-
-  T? getAuthentication<T extends Authentication>(String name) {
-    final authentication = _authentications[name];
-    return authentication is T ? authentication : null;
-  }
-
   // We don't use a Map<String, String> for queryParams.
   // If collectionFormat is 'multi', a key might appear multiple times.
   Future<Response> invokeAPI(
@@ -65,9 +36,8 @@ class ApiClient {
     Map<String, String> headerParams,
     Map<String, String> formParams,
     String? contentType,
-    List<String> authNames,
   ) async {
-    _updateParamsForAuth(authNames, queryParams, headerParams);
+    _updateParamsForAuth(queryParams, headerParams);
 
     headerParams.addAll(_defaultHeaderMap);
     if (contentType != null) {
@@ -188,18 +158,12 @@ class ApiClient {
   String serialize(Object? value) => value == null ? '' : json.encode(value);
 
   /// Update query and header parameters based on authentication settings.
-  /// @param authNames The authentications to apply
   void _updateParamsForAuth(
-    List<String> authNames,
     List<QueryParam> queryParams,
     Map<String, String> headerParams,
   ) {
-    for(final authName in authNames) {
-      final auth = _authentications[authName];
-      if (auth == null) {
-        throw ArgumentError('Authentication undefined: $authName');
-      }
-      auth.applyToParams(queryParams, headerParams);
+    if (authentication != null) {
+      authentication!.applyToParams(queryParams, headerParams);
     }
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
index 22858e953afa..d0354de38dbb 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/pet_api.dart
@@ -37,7 +37,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['application/json', 'application/xml'];
 
 
@@ -49,7 +48,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -104,7 +102,6 @@ class PetApi {
       headerParams[r'api_key'] = parameterToString(apiKey);
     }
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>[];
 
 
@@ -116,7 +113,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -160,7 +156,6 @@ class PetApi {
 
       queryParams.addAll(_queryParams('csv', 'status', status));
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>[];
 
 
@@ -172,7 +167,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -225,7 +219,6 @@ class PetApi {
 
       queryParams.addAll(_queryParams('csv', 'tags', tags));
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>[];
 
 
@@ -237,7 +230,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -289,7 +281,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>[];
 
 
@@ -301,7 +292,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -349,7 +339,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['application/json', 'application/xml'];
 
 
@@ -361,7 +350,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -416,7 +404,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['application/x-www-form-urlencoded'];
 
     if (name != null) {
@@ -434,7 +421,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -487,7 +473,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['multipart/form-data'];
 
     bool hasFields = false;
@@ -513,7 +498,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
index 51b4b81fb0f5..db1ac1f010bf 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/store_api.dart
@@ -38,7 +38,6 @@ class StoreApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -50,7 +49,6 @@ class StoreApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -85,7 +83,6 @@ class StoreApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>[];
 
 
@@ -97,7 +94,6 @@ class StoreApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -141,7 +137,6 @@ class StoreApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -153,7 +148,6 @@ class StoreApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -201,7 +195,6 @@ class StoreApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -213,7 +206,6 @@ class StoreApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
index 46eef79d505a..a44252a6130b 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api/user_api.dart
@@ -37,7 +37,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>['application/json'];
 
 
@@ -49,7 +48,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -89,7 +87,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>['application/json'];
 
 
@@ -101,7 +98,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -141,7 +137,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>['application/json'];
 
 
@@ -153,7 +148,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -194,7 +188,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>[];
 
 
@@ -206,7 +199,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -247,7 +239,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -259,7 +250,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -313,7 +303,6 @@ class UserApi {
       queryParams.addAll(_queryParams('', 'username', username));
       queryParams.addAll(_queryParams('', 'password', password));
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -325,7 +314,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -371,7 +359,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>[];
 
 
@@ -383,7 +370,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -422,7 +408,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>['application/json'];
 
 
@@ -434,7 +419,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_client.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
index 3efae0775a54..79977d854b68 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_client.dart
@@ -11,11 +11,7 @@
 part of openapi.api;
 
 class ApiClient {
-  ApiClient({this.basePath = 'http://petstore.swagger.io/v2'}) {
-    // Setup authentications (key: authentication name, value: authentication).
-    _authentications[r'api_key'] = ApiKeyAuth('header', 'api_key');
-    _authentications[r'petstore_auth'] = OAuth();
-  }
+  ApiClient({this.basePath = 'http://petstore.swagger.io/v2', this.authentication});
 
   final String basePath;
 
@@ -32,7 +28,7 @@ class ApiClient {
   }
 
   final _defaultHeaderMap = <String, String>{};
-  final _authentications = <String, Authentication>{};
+  final Authentication? authentication;
 
   void addDefaultHeader(String key, String value) {
      _defaultHeaderMap[key] = value;
@@ -40,15 +36,6 @@ class ApiClient {
 
   Map<String,String> get defaultHeaderMap => _defaultHeaderMap;
 
-  /// Returns an unmodifiable [Map] of the authentications, since none should be added
-  /// or deleted.
-  Map<String, Authentication> get authentications => Map.unmodifiable(_authentications);
-
-  T? getAuthentication<T extends Authentication>(String name) {
-    final authentication = _authentications[name];
-    return authentication is T ? authentication : null;
-  }
-
   // We don't use a Map<String, String> for queryParams.
   // If collectionFormat is 'multi', a key might appear multiple times.
   Future<Response> invokeAPI(
@@ -59,9 +46,8 @@ class ApiClient {
     Map<String, String> headerParams,
     Map<String, String> formParams,
     String? contentType,
-    List<String> authNames,
   ) async {
-    _updateParamsForAuth(authNames, queryParams, headerParams);
+    _updateParamsForAuth(queryParams, headerParams);
 
     headerParams.addAll(_defaultHeaderMap);
     if (contentType != null) {
@@ -180,18 +166,12 @@ class ApiClient {
   String serialize(Object? value) => value == null ? '' : json.encode(value);
 
   /// Update query and header parameters based on authentication settings.
-  /// @param authNames The authentications to apply
   void _updateParamsForAuth(
-    List<String> authNames,
     List<QueryParam> queryParams,
     Map<String, String> headerParams,
   ) {
-    for(final authName in authNames) {
-      final auth = _authentications[authName];
-      if (auth == null) {
-        throw ArgumentError('Authentication undefined: $authName');
-      }
-      auth.applyToParams(queryParams, headerParams);
+    if (authentication != null) {
+      authentication!.applyToParams(queryParams, headerParams);
     }
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
index f03350c4dfff..689eafbd8ed7 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/another_fake_api.dart
@@ -37,7 +37,6 @@ class AnotherFakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -49,7 +48,6 @@ class AnotherFakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
index 02c22bfa2d9f..23798028b943 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/default_api.dart
@@ -28,7 +28,6 @@ class DefaultApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -40,7 +39,6 @@ class DefaultApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
index d4bd12ec939b..6cfbfb4e6c93 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_api.dart
@@ -30,7 +30,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -42,7 +41,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -95,7 +93,6 @@ class FakeApi {
       headerParams[r'header_1'] = parameterToString(header1);
     }
 
-    const authNames = <String>['http_signature_test'];
     const contentTypes = <String>['application/json', 'application/xml'];
 
 
@@ -107,7 +104,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -149,7 +145,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -161,7 +156,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -205,7 +199,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -217,7 +210,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -261,7 +253,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -273,7 +264,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -317,7 +307,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -329,7 +318,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -373,7 +361,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -385,7 +372,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -429,7 +415,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['image/png'];
 
 
@@ -441,7 +426,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -476,7 +460,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -488,7 +471,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -523,7 +505,6 @@ class FakeApi {
 
       queryParams.addAll(_queryParams('', 'query', query));
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -535,7 +516,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -572,7 +552,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -584,7 +563,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -671,7 +649,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['http_basic_test'];
     const contentTypes = <String>['application/x-www-form-urlencoded'];
 
     if (integer != null) {
@@ -722,7 +699,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -847,7 +823,6 @@ class FakeApi {
       headerParams[r'enum_header_string'] = parameterToString(enumHeaderString);
     }
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/x-www-form-urlencoded'];
 
     if (enumFormStringArray != null) {
@@ -865,7 +840,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -957,7 +931,6 @@ class FakeApi {
       headerParams[r'boolean_group'] = parameterToString(booleanGroup);
     }
 
-    const authNames = <String>['bearer_test'];
     const contentTypes = <String>[];
 
 
@@ -969,7 +942,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -1024,7 +996,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -1036,7 +1007,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -1079,7 +1049,6 @@ class FakeApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/x-www-form-urlencoded'];
 
     if (param != null) {
@@ -1097,7 +1066,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -1159,7 +1127,6 @@ class FakeApi {
     }
       queryParams.addAll(_queryParams('', 'allowEmpty', allowEmpty));
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -1171,7 +1138,6 @@ class FakeApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
index 158c127195bf..2782357efb9b 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/fake_classname_tags123_api.dart
@@ -37,7 +37,6 @@ class FakeClassnameTags123Api {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key_query'];
     const contentTypes = <String>['application/json'];
 
 
@@ -49,7 +48,6 @@ class FakeClassnameTags123Api {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
index 74d8ab2b059d..371afa625cfc 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/pet_api.dart
@@ -37,7 +37,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['application/json', 'application/xml'];
 
 
@@ -49,7 +48,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -96,7 +94,6 @@ class PetApi {
       headerParams[r'api_key'] = parameterToString(apiKey);
     }
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>[];
 
 
@@ -108,7 +105,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -152,7 +148,6 @@ class PetApi {
 
       queryParams.addAll(_queryParams('csv', 'status', status));
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>[];
 
 
@@ -164,7 +159,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -217,7 +211,6 @@ class PetApi {
 
       queryParams.addAll(_queryParams('csv', 'tags', tags));
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>[];
 
 
@@ -229,7 +222,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -281,7 +273,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>[];
 
 
@@ -293,7 +284,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -341,7 +331,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['application/json', 'application/xml'];
 
 
@@ -353,7 +342,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -400,7 +388,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['application/x-www-form-urlencoded'];
 
     if (name != null) {
@@ -418,7 +405,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -471,7 +457,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['multipart/form-data'];
 
     bool hasFields = false;
@@ -497,7 +482,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -558,7 +542,6 @@ class PetApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['petstore_auth'];
     const contentTypes = <String>['multipart/form-data'];
 
     bool hasFields = false;
@@ -584,7 +567,6 @@ class PetApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
index ee1756bea39b..68c1c9fdccb9 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/store_api.dart
@@ -38,7 +38,6 @@ class StoreApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -50,7 +49,6 @@ class StoreApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -85,7 +83,6 @@ class StoreApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>['api_key'];
     const contentTypes = <String>[];
 
 
@@ -97,7 +94,6 @@ class StoreApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -141,7 +137,6 @@ class StoreApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -153,7 +148,6 @@ class StoreApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -201,7 +195,6 @@ class StoreApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -213,7 +206,6 @@ class StoreApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
index dec46b87bd84..a44252a6130b 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api/user_api.dart
@@ -37,7 +37,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -49,7 +48,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -89,7 +87,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -101,7 +98,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -141,7 +137,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -153,7 +148,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -194,7 +188,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -206,7 +199,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -247,7 +239,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -259,7 +250,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -313,7 +303,6 @@ class UserApi {
       queryParams.addAll(_queryParams('', 'username', username));
       queryParams.addAll(_queryParams('', 'password', password));
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -325,7 +314,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -371,7 +359,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>[];
 
 
@@ -383,7 +370,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
@@ -422,7 +408,6 @@ class UserApi {
     final headerParams = <String, String>{};
     final formParams = <String, String>{};
 
-    const authNames = <String>[];
     const contentTypes = <String>['application/json'];
 
 
@@ -434,7 +419,6 @@ class UserApi {
       headerParams,
       formParams,
       contentTypes.isEmpty ? null : contentTypes.first,
-      authNames,
     );
   }
 
diff --git a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_client.dart b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_client.dart
index 508d1b2beac9..ba7a9e692b7a 100644
--- a/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_client.dart
+++ b/samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_client.dart
@@ -11,14 +11,7 @@
 part of openapi.api;
 
 class ApiClient {
-  ApiClient({this.basePath = 'http://petstore.swagger.io:80/v2'}) {
-    // Setup authentications (key: authentication name, value: authentication).
-    _authentications[r'api_key'] = ApiKeyAuth('header', 'api_key');
-    _authentications[r'api_key_query'] = ApiKeyAuth('query', 'api_key_query');
-    _authentications[r'bearer_test'] = HttpBearerAuth();
-    _authentications[r'http_basic_test'] = HttpBasicAuth();
-    _authentications[r'petstore_auth'] = OAuth();
-  }
+  ApiClient({this.basePath = 'http://petstore.swagger.io:80/v2', this.authentication});
 
   final String basePath;
 
@@ -35,7 +28,7 @@ class ApiClient {
   }
 
   final _defaultHeaderMap = <String, String>{};
-  final _authentications = <String, Authentication>{};
+  final Authentication? authentication;
 
   void addDefaultHeader(String key, String value) {
      _defaultHeaderMap[key] = value;
@@ -43,15 +36,6 @@ class ApiClient {
 
   Map<String,String> get defaultHeaderMap => _defaultHeaderMap;
 
-  /// Returns an unmodifiable [Map] of the authentications, since none should be added
-  /// or deleted.
-  Map<String, Authentication> get authentications => Map.unmodifiable(_authentications);
-
-  T? getAuthentication<T extends Authentication>(String name) {
-    final authentication = _authentications[name];
-    return authentication is T ? authentication : null;
-  }
-
   // We don't use a Map<String, String> for queryParams.
   // If collectionFormat is 'multi', a key might appear multiple times.
   Future<Response> invokeAPI(
@@ -62,9 +46,8 @@ class ApiClient {
     Map<String, String> headerParams,
     Map<String, String> formParams,
     String? contentType,
-    List<String> authNames,
   ) async {
-    _updateParamsForAuth(authNames, queryParams, headerParams);
+    _updateParamsForAuth(queryParams, headerParams);
 
     headerParams.addAll(_defaultHeaderMap);
     if (contentType != null) {
@@ -183,18 +166,12 @@ class ApiClient {
   String serialize(Object? value) => value == null ? '' : json.encode(value);
 
   /// Update query and header parameters based on authentication settings.
-  /// @param authNames The authentications to apply
   void _updateParamsForAuth(
-    List<String> authNames,
     List<QueryParam> queryParams,
     Map<String, String> headerParams,
   ) {
-    for(final authName in authNames) {
-      final auth = _authentications[authName];
-      if (auth == null) {
-        throw ArgumentError('Authentication undefined: $authName');
-      }
-      auth.applyToParams(queryParams, headerParams);
+    if (authentication != null) {
+      authentication!.applyToParams(queryParams, headerParams);
     }
   }