diff --git a/csharp/src/Google.Protobuf.Test/testprotos.pb b/csharp/src/Google.Protobuf.Test/testprotos.pb
index 31c0359c4d..df38f46b09 100644
Binary files a/csharp/src/Google.Protobuf.Test/testprotos.pb and b/csharp/src/Google.Protobuf.Test/testprotos.pb differ
diff --git a/csharp/src/Google.Protobuf/Reflection/Descriptor.pb.cs b/csharp/src/Google.Protobuf/Reflection/Descriptor.pb.cs
index c7ea7e1663..e0e8127489 100644
--- a/csharp/src/Google.Protobuf/Reflection/Descriptor.pb.cs
+++ b/csharp/src/Google.Protobuf/Reflection/Descriptor.pb.cs
@@ -817,6 +817,9 @@ namespace Google.Protobuf.Reflection {
     /// The supported values are "proto2", "proto3", and "editions".
     ///
     /// If `edition` is present, this value must be "editions".
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -846,6 +849,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.Edition edition_;
     /// <summary>
     /// The edition of the proto file.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -6675,6 +6681,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.FeatureSet features_;
     /// <summary>
     /// Any features defined in the specific edition.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -7653,6 +7662,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.FeatureSet features_;
     /// <summary>
     /// Any features defined in the specific edition.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -8409,6 +8421,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.FeatureSet features_;
     /// <summary>
     /// Any features defined in the specific edition.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -9711,6 +9726,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.FeatureSet features_;
     /// <summary>
     /// Any features defined in the specific edition.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -10102,6 +10120,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.FeatureSet features_;
     /// <summary>
     /// Any features defined in the specific edition.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -10496,6 +10517,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.FeatureSet features_;
     /// <summary>
     /// Any features defined in the specific edition.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -10911,6 +10935,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.FeatureSet features_;
     /// <summary>
     /// Any features defined in the specific edition.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
@@ -11316,6 +11343,9 @@ namespace Google.Protobuf.Reflection {
     private global::Google.Protobuf.Reflection.FeatureSet features_;
     /// <summary>
     /// Any features defined in the specific edition.
+    /// WARNING: This field should only be used by protobuf plugins or special
+    /// cases like the proto compiler. Other uses are discouraged and
+    /// developers should rely on the protoreflect APIs for their client language.
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
diff --git a/csharp/src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs b/csharp/src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs
new file mode 100644
index 0000000000..208ce1fcb6
--- /dev/null
+++ b/csharp/src/Google.Protobuf/Reflection/FeatureSetDescriptor.g.cs
@@ -0,0 +1,17 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+#endregion
+
+namespace Google.Protobuf.Reflection;
+
+internal sealed partial class FeatureSetDescriptor
+{
+    // Canonical serialized form of the edition defaults, generated by embed_edition_defaults.
+    private const string DefaultsBase64 =
+        "ChMYhAciACoMCAEQAhgCIAMoATACChMY5wciACoMCAIQARgBIAIoATABChMY6AciDAgBEAEYASACKAEwASoAIOYHKOgH";
+}
diff --git a/php/src/Google/Protobuf/Internal/EnumOptions.php b/php/src/Google/Protobuf/Internal/EnumOptions.php
index b7d2059606..71a952f851 100644
--- a/php/src/Google/Protobuf/Internal/EnumOptions.php
+++ b/php/src/Google/Protobuf/Internal/EnumOptions.php
@@ -46,6 +46,9 @@ class EnumOptions extends \Google\Protobuf\Internal\Message
     protected $deprecated_legacy_json_field_conflicts = null;
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 7;</code>
      */
@@ -80,6 +83,9 @@ class EnumOptions extends \Google\Protobuf\Internal\Message
      *           had time to migrate.
      *     @type \Google\Protobuf\Internal\FeatureSet $features
      *           Any features defined in the specific edition.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type array<\Google\Protobuf\Internal\UninterpretedOption>|\Google\Protobuf\Internal\RepeatedField $uninterpreted_option
      *           The parser stores options it doesn't recognize here. See above.
      * }
@@ -227,6 +233,9 @@ class EnumOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 7;</code>
      * @return \Google\Protobuf\Internal\FeatureSet|null
@@ -248,6 +257,9 @@ class EnumOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 7;</code>
      * @param \Google\Protobuf\Internal\FeatureSet $var
diff --git a/php/src/Google/Protobuf/Internal/EnumValueOptions.php b/php/src/Google/Protobuf/Internal/EnumValueOptions.php
index f99234bd2f..76af9882ac 100644
--- a/php/src/Google/Protobuf/Internal/EnumValueOptions.php
+++ b/php/src/Google/Protobuf/Internal/EnumValueOptions.php
@@ -27,6 +27,9 @@ class EnumValueOptions extends \Google\Protobuf\Internal\Message
     protected $deprecated = null;
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 2;</code>
      */
@@ -65,6 +68,9 @@ class EnumValueOptions extends \Google\Protobuf\Internal\Message
      *           this is a formalization for deprecating enum values.
      *     @type \Google\Protobuf\Internal\FeatureSet $features
      *           Any features defined in the specific edition.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type bool $debug_redact
      *           Indicate that fields annotated with this enum value should not be printed
      *           out when using debug formats, e.g. when the field contains sensitive
@@ -124,6 +130,9 @@ class EnumValueOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 2;</code>
      * @return \Google\Protobuf\Internal\FeatureSet|null
@@ -145,6 +154,9 @@ class EnumValueOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 2;</code>
      * @param \Google\Protobuf\Internal\FeatureSet $var
diff --git a/php/src/Google/Protobuf/Internal/FieldOptions.php b/php/src/Google/Protobuf/Internal/FieldOptions.php
index efde73f695..69b96b2596 100644
--- a/php/src/Google/Protobuf/Internal/FieldOptions.php
+++ b/php/src/Google/Protobuf/Internal/FieldOptions.php
@@ -123,6 +123,9 @@ class FieldOptions extends \Google\Protobuf\Internal\Message
     private $edition_defaults;
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 21;</code>
      */
@@ -210,6 +213,9 @@ class FieldOptions extends \Google\Protobuf\Internal\Message
      *     @type array<\Google\Protobuf\Internal\FieldOptions\EditionDefault>|\Google\Protobuf\Internal\RepeatedField $edition_defaults
      *     @type \Google\Protobuf\Internal\FeatureSet $features
      *           Any features defined in the specific edition.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type \Google\Protobuf\Internal\FieldOptions\FeatureSupport $feature_support
      *     @type array<\Google\Protobuf\Internal\UninterpretedOption>|\Google\Protobuf\Internal\RepeatedField $uninterpreted_option
      *           The parser stores options it doesn't recognize here. See above.
@@ -676,6 +682,9 @@ class FieldOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 21;</code>
      * @return \Google\Protobuf\Internal\FeatureSet|null
@@ -697,6 +706,9 @@ class FieldOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 21;</code>
      * @param \Google\Protobuf\Internal\FeatureSet $var
diff --git a/php/src/Google/Protobuf/Internal/FileDescriptorProto.php b/php/src/Google/Protobuf/Internal/FileDescriptorProto.php
index 659d3b3675..b01cf6e307 100644
--- a/php/src/Google/Protobuf/Internal/FileDescriptorProto.php
+++ b/php/src/Google/Protobuf/Internal/FileDescriptorProto.php
@@ -84,12 +84,18 @@ class FileDescriptorProto extends \Google\Protobuf\Internal\Message
      * The syntax of the proto file.
      * The supported values are "proto2", "proto3", and "editions".
      * If `edition` is present, this value must be "editions".
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional string syntax = 12;</code>
      */
     protected $syntax = null;
     /**
      * The edition of the proto file.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.Edition edition = 14;</code>
      */
@@ -127,8 +133,14 @@ class FileDescriptorProto extends \Google\Protobuf\Internal\Message
      *           The syntax of the proto file.
      *           The supported values are "proto2", "proto3", and "editions".
      *           If `edition` is present, this value must be "editions".
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type int $edition
      *           The edition of the proto file.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      * }
      */
     public function __construct($data = NULL) {
@@ -458,6 +470,9 @@ class FileDescriptorProto extends \Google\Protobuf\Internal\Message
      * The syntax of the proto file.
      * The supported values are "proto2", "proto3", and "editions".
      * If `edition` is present, this value must be "editions".
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional string syntax = 12;</code>
      * @return string
@@ -481,6 +496,9 @@ class FileDescriptorProto extends \Google\Protobuf\Internal\Message
      * The syntax of the proto file.
      * The supported values are "proto2", "proto3", and "editions".
      * If `edition` is present, this value must be "editions".
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional string syntax = 12;</code>
      * @param string $var
@@ -496,6 +514,9 @@ class FileDescriptorProto extends \Google\Protobuf\Internal\Message
 
     /**
      * The edition of the proto file.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.Edition edition = 14;</code>
      * @return int
@@ -517,6 +538,9 @@ class FileDescriptorProto extends \Google\Protobuf\Internal\Message
 
     /**
      * The edition of the proto file.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.Edition edition = 14;</code>
      * @param int $var
diff --git a/php/src/Google/Protobuf/Internal/FileOptions.php b/php/src/Google/Protobuf/Internal/FileOptions.php
index 9d2c2ab010..a130d5a67a 100644
--- a/php/src/Google/Protobuf/Internal/FileOptions.php
+++ b/php/src/Google/Protobuf/Internal/FileOptions.php
@@ -173,6 +173,9 @@ class FileOptions extends \Google\Protobuf\Internal\Message
     protected $ruby_package = null;
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 50;</code>
      */
@@ -274,6 +277,9 @@ class FileOptions extends \Google\Protobuf\Internal\Message
      *           determining the ruby package.
      *     @type \Google\Protobuf\Internal\FeatureSet $features
      *           Any features defined in the specific edition.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type array<\Google\Protobuf\Internal\UninterpretedOption>|\Google\Protobuf\Internal\RepeatedField $uninterpreted_option
      *           The parser stores options it doesn't recognize here.
      *           See the documentation for the "Options" section above.
@@ -1060,6 +1066,9 @@ class FileOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 50;</code>
      * @return \Google\Protobuf\Internal\FeatureSet|null
@@ -1081,6 +1090,9 @@ class FileOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 50;</code>
      * @param \Google\Protobuf\Internal\FeatureSet $var
diff --git a/php/src/Google/Protobuf/Internal/MessageOptions.php b/php/src/Google/Protobuf/Internal/MessageOptions.php
index 2fe22c2869..23ba7b4a25 100644
--- a/php/src/Google/Protobuf/Internal/MessageOptions.php
+++ b/php/src/Google/Protobuf/Internal/MessageOptions.php
@@ -92,6 +92,9 @@ class MessageOptions extends \Google\Protobuf\Internal\Message
     protected $deprecated_legacy_json_field_conflicts = null;
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 12;</code>
      */
@@ -164,6 +167,9 @@ class MessageOptions extends \Google\Protobuf\Internal\Message
      *           teams have had time to migrate.
      *     @type \Google\Protobuf\Internal\FeatureSet $features
      *           Any features defined in the specific edition.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type array<\Google\Protobuf\Internal\UninterpretedOption>|\Google\Protobuf\Internal\RepeatedField $uninterpreted_option
      *           The parser stores options it doesn't recognize here. See above.
      * }
@@ -451,6 +457,9 @@ class MessageOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 12;</code>
      * @return \Google\Protobuf\Internal\FeatureSet|null
@@ -472,6 +481,9 @@ class MessageOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 12;</code>
      * @param \Google\Protobuf\Internal\FeatureSet $var
diff --git a/php/src/Google/Protobuf/Internal/MethodOptions.php b/php/src/Google/Protobuf/Internal/MethodOptions.php
index fc9e551029..da27df21aa 100644
--- a/php/src/Google/Protobuf/Internal/MethodOptions.php
+++ b/php/src/Google/Protobuf/Internal/MethodOptions.php
@@ -31,6 +31,9 @@ class MethodOptions extends \Google\Protobuf\Internal\Message
     protected $idempotency_level = null;
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 35;</code>
      */
@@ -56,6 +59,9 @@ class MethodOptions extends \Google\Protobuf\Internal\Message
      *     @type int $idempotency_level
      *     @type \Google\Protobuf\Internal\FeatureSet $features
      *           Any features defined in the specific edition.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type array<\Google\Protobuf\Internal\UninterpretedOption>|\Google\Protobuf\Internal\RepeatedField $uninterpreted_option
      *           The parser stores options it doesn't recognize here. See above.
      * }
@@ -141,6 +147,9 @@ class MethodOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 35;</code>
      * @return \Google\Protobuf\Internal\FeatureSet|null
@@ -162,6 +171,9 @@ class MethodOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 35;</code>
      * @param \Google\Protobuf\Internal\FeatureSet $var
diff --git a/php/src/Google/Protobuf/Internal/OneofOptions.php b/php/src/Google/Protobuf/Internal/OneofOptions.php
index 4d7f344680..2d94ac4898 100644
--- a/php/src/Google/Protobuf/Internal/OneofOptions.php
+++ b/php/src/Google/Protobuf/Internal/OneofOptions.php
@@ -18,6 +18,9 @@ class OneofOptions extends \Google\Protobuf\Internal\Message
 {
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 1;</code>
      */
@@ -37,6 +40,9 @@ class OneofOptions extends \Google\Protobuf\Internal\Message
      *
      *     @type \Google\Protobuf\Internal\FeatureSet $features
      *           Any features defined in the specific edition.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type array<\Google\Protobuf\Internal\UninterpretedOption>|\Google\Protobuf\Internal\RepeatedField $uninterpreted_option
      *           The parser stores options it doesn't recognize here. See above.
      * }
@@ -48,6 +54,9 @@ class OneofOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 1;</code>
      * @return \Google\Protobuf\Internal\FeatureSet|null
@@ -69,6 +78,9 @@ class OneofOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 1;</code>
      * @param \Google\Protobuf\Internal\FeatureSet $var
diff --git a/php/src/Google/Protobuf/Internal/ServiceOptions.php b/php/src/Google/Protobuf/Internal/ServiceOptions.php
index 278a60c5ce..56b44585a2 100644
--- a/php/src/Google/Protobuf/Internal/ServiceOptions.php
+++ b/php/src/Google/Protobuf/Internal/ServiceOptions.php
@@ -18,6 +18,9 @@ class ServiceOptions extends \Google\Protobuf\Internal\Message
 {
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 34;</code>
      */
@@ -46,6 +49,9 @@ class ServiceOptions extends \Google\Protobuf\Internal\Message
      *
      *     @type \Google\Protobuf\Internal\FeatureSet $features
      *           Any features defined in the specific edition.
+     *           WARNING: This field should only be used by protobuf plugins or special
+     *           cases like the proto compiler. Other uses are discouraged and
+     *           developers should rely on the protoreflect APIs for their client language.
      *     @type bool $deprecated
      *           Is this service deprecated?
      *           Depending on the target platform, this can emit Deprecated annotations
@@ -62,6 +68,9 @@ class ServiceOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 34;</code>
      * @return \Google\Protobuf\Internal\FeatureSet|null
@@ -83,6 +92,9 @@ class ServiceOptions extends \Google\Protobuf\Internal\Message
 
     /**
      * Any features defined in the specific edition.
+     * WARNING: This field should only be used by protobuf plugins or special
+     * cases like the proto compiler. Other uses are discouraged and
+     * developers should rely on the protoreflect APIs for their client language.
      *
      * Generated from protobuf field <code>optional .google.protobuf.FeatureSet features = 34;</code>
      * @param \Google\Protobuf\Internal\FeatureSet $var