diff --git a/LanguageFeatures/Static-extensions/syntax_A01_t01.dart b/LanguageFeatures/Static-extensions/syntax_A01_t01.dart
new file mode 100644
index 0000000000..36f5743f9f
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A01_t01.dart
@@ -0,0 +1,39 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+/// ...
+/// For the purpose of identifying the on-declaration of a given extension, the
+/// types `void`, `dynamic`, and `Never` are not considered to be classes, and
+/// neither are record types or function types.
+///
+/// @description Checks that that it is a compile-time error to declare a
+/// factory constructor in an extension declaration that has no on-declaration.
+/// Test extension on type `void`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+class C {}
+
+typedef Void = void;
+
+extension Ext on void {
+  factory Void.foo() => 42;
+//^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  factory Void.bar() = C.new;
+//^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  print(C);
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A01_t02.dart b/LanguageFeatures/Static-extensions/syntax_A01_t02.dart
new file mode 100644
index 0000000000..7666b5c19c
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A01_t02.dart
@@ -0,0 +1,37 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+/// ...
+/// For the purpose of identifying the on-declaration of a given extension, the
+/// types `void`, `dynamic`, and `Never` are not considered to be classes, and
+/// neither are record types or function types.
+///
+/// @description Checks that that it is a compile-time error to declare a
+/// factory constructor in an extension declaration that has no on-declaration.
+/// Test extension on type `dynamic`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+class C {}
+
+extension Ext on dynamic {
+  factory dynamic.foo() => C();
+//^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  factory dynamic.bar() = C.new;
+//^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  print(C);
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A01_t03.dart b/LanguageFeatures/Static-extensions/syntax_A01_t03.dart
new file mode 100644
index 0000000000..1b54acd7f0
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A01_t03.dart
@@ -0,0 +1,37 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+/// ...
+/// For the purpose of identifying the on-declaration of a given extension, the
+/// types `void`, `dynamic`, and `Never` are not considered to be classes, and
+/// neither are record types or function types.
+///
+/// @description Checks that that it is a compile-time error to declare a
+/// factory constructor in an extension declaration that has no on-declaration.
+/// Test extension on type `Never`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+class C {}
+
+extension Ext on Never {
+  factory Never.foo() => C();
+//^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  factory Never.bar() = C.new;
+//^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  print(C);
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A01_t04.dart b/LanguageFeatures/Static-extensions/syntax_A01_t04.dart
new file mode 100644
index 0000000000..969b1fd439
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A01_t04.dart
@@ -0,0 +1,29 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+/// ...
+/// For the purpose of identifying the on-declaration of a given extension, the
+/// types `void`, `dynamic`, and `Never` are not considered to be classes, and
+/// neither are record types or function types.
+///
+/// @description Checks that that it is a compile-time error to declare a
+/// factory constructor in an extension declaration that has no on-declaration.
+/// Test extension on type `Record`.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+extension Ext on Record {
+  factory Record.foo() => ();
+//^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A01_t05.dart b/LanguageFeatures/Static-extensions/syntax_A01_t05.dart
new file mode 100644
index 0000000000..732cc4dd4b
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A01_t05.dart
@@ -0,0 +1,32 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+/// ...
+/// For the purpose of identifying the on-declaration of a given extension, the
+/// types `void`, `dynamic`, and `Never` are not considered to be classes, and
+/// neither are record types or function types.
+///
+/// @description Checks that that it is a compile-time error to declare a
+/// factory constructor in an extension declaration that has no on-declaration.
+/// Test extension on a function type.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+typedef F = void Function();
+
+extension Ext on F {
+  factory F.foo() => () {};
+//^^^^^^^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  print(F);
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A02_t01.dart b/LanguageFeatures/Static-extensions/syntax_A02_t01.dart
new file mode 100644
index 0000000000..fcc927af2f
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A02_t01.dart
@@ -0,0 +1,43 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+///
+/// @description Checks that that it is not an error to declare a factory
+/// constructor in an extension declaration that has an on-declaration.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+import '../../Utils/expect.dart';
+
+class C {
+  int v;
+  C(this.v);
+}
+
+class D extends C {
+  D(super.v);
+}
+
+extension type ET(int v) {}
+
+extension ExtC on C {
+  factory C.foo() => D(0);
+
+  factory C.bar(int v) = C.new;
+}
+
+extension ExtET on ET {
+  factory ET.baz(int v) = ET.new;
+}
+
+main() {
+  Expect.equals(0, C.foo().v);
+  Expect.equals(1, C.bar(1).v);
+  Expect.equals(2, ET.baz(2).v);
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A02_t02.dart b/LanguageFeatures/Static-extensions/syntax_A02_t02.dart
new file mode 100644
index 0000000000..4e8a506de0
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A02_t02.dart
@@ -0,0 +1,43 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+///
+/// @description Checks that that it is not an error to declare a constant
+/// factory constructor in an extension declaration that has an on-declaration.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+import '../../Utils/expect.dart';
+
+class C {
+  final int v;
+  const C(this.v);
+}
+
+class D extends C {
+  const D(super.v);
+}
+
+extension type const ET(int v) {}
+
+extension ExtC on C {
+  const factory C.foo() => const D(0);
+
+  const factory C.bar(int v) = C.new;
+}
+
+extension ExtET on ET {
+  const factory ET.baz(int v) = ET.new;
+}
+
+main() {
+  Expect.equals(0, const C.foo().v);
+  Expect.equals(1, const C.bar(1).v);
+  Expect.equals(2, const ET.baz(2).v);
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A02_t03.dart b/LanguageFeatures/Static-extensions/syntax_A02_t03.dart
new file mode 100644
index 0000000000..45ad5d882a
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A02_t03.dart
@@ -0,0 +1,37 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+///
+/// @description Checks that that it is not an error to declare a redirecting
+/// generative constructor in an extension declaration that has an
+/// on-declaration.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+import '../../Utils/expect.dart';
+
+class C {
+  int v;
+  C(this.v);
+}
+
+extension type ET(int v) {}
+
+extension ExtC on C {
+  C.foo() : this(0);
+}
+
+extension ExtET on ET {
+  ET.bar() : this(1);
+}
+
+main() {
+  Expect.equals(0, C.foo().v);
+  Expect.equals(1, ET.bar().v);
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A02_t04.dart b/LanguageFeatures/Static-extensions/syntax_A02_t04.dart
new file mode 100644
index 0000000000..5bf2cbcb67
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A02_t04.dart
@@ -0,0 +1,49 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+///
+/// @description Checks that that it is not an error to declare a constant
+/// redirecting generative constructor in an extension declaration that has an
+/// on-declaration.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+import '../../Utils/expect.dart';
+
+class C {
+  final int v;
+  const C(this.v);
+}
+
+extension type const ET(int v) {}
+
+enum E {
+  e0(0), e1.baz();
+
+  final int v;
+  const E(this.v);
+}
+
+extension ExtC on C {
+  const C.foo() : this(0);
+}
+
+extension ExtET on ET {
+  const ET.bar() : this(1);
+}
+
+extension ExtE on E {
+  const E.baz() : this(2);
+}
+
+main() {
+  Expect.equals(0, C.foo().v);
+  Expect.equals(1, ET.bar().v);
+  Expect.equals(2, E.e1.v);
+}
diff --git a/LanguageFeatures/Static-extensions/syntax_A02_t05.dart b/LanguageFeatures/Static-extensions/syntax_A02_t05.dart
new file mode 100644
index 0000000000..7ea3f77dbb
--- /dev/null
+++ b/LanguageFeatures/Static-extensions/syntax_A02_t05.dart
@@ -0,0 +1,33 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// @assertion It is no longer an error to declare a factory constructor,
+/// redirecting or not, or a redirecting generative constructor in an extension
+/// declaration that has an on-declaration (defined later in this section), and
+/// both kinds can be constant or not.
+///
+/// @description Checks that that it is not a compile-time error to declare a
+/// non-constant constant redirecting generative constructor in an extension
+/// declaration on an enum.
+/// @author sgrekhov22@gmail.com
+
+// SharedOptions=--enable-experiment=static-extensions
+
+enum E {
+  e0(0);
+
+  final int v;
+  const E(this.v);
+}
+
+extension ExtE on E {
+  E.baz() : this(1);
+//^
+// [analyzer] unspecified
+// [cfe] unspecified
+}
+
+main() {
+  print(E);
+}