diff --git a/go/chat/v1/gamingplatform.go b/go/chat/v1/gamingplatform.go
index afb83a4..c3709bc 100644
--- a/go/chat/v1/gamingplatform.go
+++ b/go/chat/v1/gamingplatform.go
@@ -5,3 +5,5 @@ package chatv1
 const InitiateChatType = "Chat.InitiateChat.v1"
 const InitiateChatResponseType = "Chat.InitiateChatResponse.v1"
 const MessageWrittenType = "Chat.MessageWritten.v1"
+const WriteMessageType = "Chat.WriteMessage.v1"
+const WriteMessageResponseType = "Chat.WriteMessageResponse.v1"
diff --git a/go/chat/v1/messaging.pb.go b/go/chat/v1/messaging.pb.go
index 9d102a2..fea6e0d 100644
--- a/go/chat/v1/messaging.pb.go
+++ b/go/chat/v1/messaging.pb.go
@@ -133,6 +133,112 @@ func (x *InitiateChatResponse) GetCorrelationId() string {
 	return ""
 }
 
+type WriteMessage struct {
+	state protoimpl.MessageState `protogen:"open.v1"`
+	// This applies per author within a chat.
+	// Don't set if no idempotency is needed.
+	IdempotencyKey string `protobuf:"bytes,1,opt,name=idempotency_key,json=idempotencyKey,proto3" json:"idempotency_key,omitempty"`
+	ChatId         string `protobuf:"bytes,2,opt,name=chat_id,json=chatId,proto3" json:"chat_id,omitempty"`
+	AuthorId       string `protobuf:"bytes,3,opt,name=author_id,json=authorId,proto3" json:"author_id,omitempty"`
+	Message        string `protobuf:"bytes,4,opt,name=message,proto3" json:"message,omitempty"`
+	unknownFields  protoimpl.UnknownFields
+	sizeCache      protoimpl.SizeCache
+}
+
+func (x *WriteMessage) Reset() {
+	*x = WriteMessage{}
+	mi := &file_gamingplatform_api_chat_v1_messaging_proto_msgTypes[2]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *WriteMessage) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*WriteMessage) ProtoMessage() {}
+
+func (x *WriteMessage) ProtoReflect() protoreflect.Message {
+	mi := &file_gamingplatform_api_chat_v1_messaging_proto_msgTypes[2]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use WriteMessage.ProtoReflect.Descriptor instead.
+func (*WriteMessage) Descriptor() ([]byte, []int) {
+	return file_gamingplatform_api_chat_v1_messaging_proto_rawDescGZIP(), []int{2}
+}
+
+func (x *WriteMessage) GetIdempotencyKey() string {
+	if x != nil {
+		return x.IdempotencyKey
+	}
+	return ""
+}
+
+func (x *WriteMessage) GetChatId() string {
+	if x != nil {
+		return x.ChatId
+	}
+	return ""
+}
+
+func (x *WriteMessage) GetAuthorId() string {
+	if x != nil {
+		return x.AuthorId
+	}
+	return ""
+}
+
+func (x *WriteMessage) GetMessage() string {
+	if x != nil {
+		return x.Message
+	}
+	return ""
+}
+
+type WriteMessageResponse struct {
+	state         protoimpl.MessageState `protogen:"open.v1"`
+	unknownFields protoimpl.UnknownFields
+	sizeCache     protoimpl.SizeCache
+}
+
+func (x *WriteMessageResponse) Reset() {
+	*x = WriteMessageResponse{}
+	mi := &file_gamingplatform_api_chat_v1_messaging_proto_msgTypes[3]
+	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+	ms.StoreMessageInfo(mi)
+}
+
+func (x *WriteMessageResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*WriteMessageResponse) ProtoMessage() {}
+
+func (x *WriteMessageResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_gamingplatform_api_chat_v1_messaging_proto_msgTypes[3]
+	if x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use WriteMessageResponse.ProtoReflect.Descriptor instead.
+func (*WriteMessageResponse) Descriptor() ([]byte, []int) {
+	return file_gamingplatform_api_chat_v1_messaging_proto_rawDescGZIP(), []int{3}
+}
+
 type MessageWritten struct {
 	state     protoimpl.MessageState `protogen:"open.v1"`
 	ChatId    string                 `protobuf:"bytes,1,opt,name=chat_id,json=chatId,proto3" json:"chat_id,omitempty"`
@@ -147,7 +253,7 @@ type MessageWritten struct {
 
 func (x *MessageWritten) Reset() {
 	*x = MessageWritten{}
-	mi := &file_gamingplatform_api_chat_v1_messaging_proto_msgTypes[2]
+	mi := &file_gamingplatform_api_chat_v1_messaging_proto_msgTypes[4]
 	ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 	ms.StoreMessageInfo(mi)
 }
@@ -159,7 +265,7 @@ func (x *MessageWritten) String() string {
 func (*MessageWritten) ProtoMessage() {}
 
 func (x *MessageWritten) ProtoReflect() protoreflect.Message {
-	mi := &file_gamingplatform_api_chat_v1_messaging_proto_msgTypes[2]
+	mi := &file_gamingplatform_api_chat_v1_messaging_proto_msgTypes[4]
 	if x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -172,7 +278,7 @@ func (x *MessageWritten) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use MessageWritten.ProtoReflect.Descriptor instead.
 func (*MessageWritten) Descriptor() ([]byte, []int) {
-	return file_gamingplatform_api_chat_v1_messaging_proto_rawDescGZIP(), []int{2}
+	return file_gamingplatform_api_chat_v1_messaging_proto_rawDescGZIP(), []int{4}
 }
 
 func (x *MessageWritten) GetChatId() string {
@@ -221,7 +327,13 @@ const file_gamingplatform_api_chat_v1_messaging_proto_rawDesc = "" +
 	"\aauthors\x18\x03 \x03(\tR\aauthors\"V\n" +
 	"\x14InitiateChatResponse\x12\x17\n" +
 	"\achat_id\x18\x01 \x01(\tR\x06chatId\x12%\n" +
-	"\x0ecorrelation_id\x18\x02 \x01(\tR\rcorrelationId\"\x9e\x01\n" +
+	"\x0ecorrelation_id\x18\x02 \x01(\tR\rcorrelationId\"\x87\x01\n" +
+	"\fWriteMessage\x12'\n" +
+	"\x0fidempotency_key\x18\x01 \x01(\tR\x0eidempotencyKey\x12\x17\n" +
+	"\achat_id\x18\x02 \x01(\tR\x06chatId\x12\x1b\n" +
+	"\tauthor_id\x18\x03 \x01(\tR\bauthorId\x12\x18\n" +
+	"\amessage\x18\x04 \x01(\tR\amessage\"\x16\n" +
+	"\x14WriteMessageResponse\"\x9e\x01\n" +
 	"\x0eMessageWritten\x12\x17\n" +
 	"\achat_id\x18\x01 \x01(\tR\x06chatId\x12\x1d\n" +
 	"\n" +
@@ -243,11 +355,13 @@ func file_gamingplatform_api_chat_v1_messaging_proto_rawDescGZIP() []byte {
 	return file_gamingplatform_api_chat_v1_messaging_proto_rawDescData
 }
 
-var file_gamingplatform_api_chat_v1_messaging_proto_msgTypes = make([]protoimpl.MessageInfo, 3)
+var file_gamingplatform_api_chat_v1_messaging_proto_msgTypes = make([]protoimpl.MessageInfo, 5)
 var file_gamingplatform_api_chat_v1_messaging_proto_goTypes = []any{
 	(*InitiateChat)(nil),         // 0: gamingplatform.api.chat.v1.InitiateChat
 	(*InitiateChatResponse)(nil), // 1: gamingplatform.api.chat.v1.InitiateChatResponse
-	(*MessageWritten)(nil),       // 2: gamingplatform.api.chat.v1.MessageWritten
+	(*WriteMessage)(nil),         // 2: gamingplatform.api.chat.v1.WriteMessage
+	(*WriteMessageResponse)(nil), // 3: gamingplatform.api.chat.v1.WriteMessageResponse
+	(*MessageWritten)(nil),       // 4: gamingplatform.api.chat.v1.MessageWritten
 }
 var file_gamingplatform_api_chat_v1_messaging_proto_depIdxs = []int32{
 	0, // [0:0] is the sub-list for method output_type
@@ -268,7 +382,7 @@ func file_gamingplatform_api_chat_v1_messaging_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: unsafe.Slice(unsafe.StringData(file_gamingplatform_api_chat_v1_messaging_proto_rawDesc), len(file_gamingplatform_api_chat_v1_messaging_proto_rawDesc)),
 			NumEnums:      0,
-			NumMessages:   3,
+			NumMessages:   5,
 			NumExtensions: 0,
 			NumServices:   0,
 		},
diff --git a/php/GamingPlatform/Api/Chat/V1/ChatV1.php b/php/GamingPlatform/Api/Chat/V1/ChatV1.php
index fc6d18e..d982818 100644
--- a/php/GamingPlatform/Api/Chat/V1/ChatV1.php
+++ b/php/GamingPlatform/Api/Chat/V1/ChatV1.php
@@ -38,4 +38,24 @@ public static function createMessageWritten(
         if ($data !== null) $message->mergeFromString($data);
         return $message;
     }
+    public const string WriteMessageType = 'Chat.WriteMessage.v1';
+    public static function createWriteMessage(
+        ?string $data = null
+    ): WriteMessage {
+        static $template;
+        $template ??= new WriteMessage();
+        $message = clone $template;
+        if ($data !== null) $message->mergeFromString($data);
+        return $message;
+    }
+    public const string WriteMessageResponseType = 'Chat.WriteMessageResponse.v1';
+    public static function createWriteMessageResponse(
+        ?string $data = null
+    ): WriteMessageResponse {
+        static $template;
+        $template ??= new WriteMessageResponse();
+        $message = clone $template;
+        if ($data !== null) $message->mergeFromString($data);
+        return $message;
+    }
 }
diff --git a/php/GamingPlatform/Api/Chat/V1/ChatV1Factory.php b/php/GamingPlatform/Api/Chat/V1/ChatV1Factory.php
index 5419e3b..347d6e1 100644
--- a/php/GamingPlatform/Api/Chat/V1/ChatV1Factory.php
+++ b/php/GamingPlatform/Api/Chat/V1/ChatV1Factory.php
@@ -42,4 +42,26 @@ public static function createMessageWritten(
         return $message;
     }
 
+    /** @deprecated */
+    public static function createWriteMessage(
+        string $data
+    ): \GamingPlatform\Api\Chat\V1\WriteMessage {
+        static $template;
+        $template ??= new \GamingPlatform\Api\Chat\V1\WriteMessage();
+        $message = clone $template;
+        $message->mergeFromString($data);
+        return $message;
+    }
+
+    /** @deprecated */
+    public static function createWriteMessageResponse(
+        string $data
+    ): \GamingPlatform\Api\Chat\V1\WriteMessageResponse {
+        static $template;
+        $template ??= new \GamingPlatform\Api\Chat\V1\WriteMessageResponse();
+        $message = clone $template;
+        $message->mergeFromString($data);
+        return $message;
+    }
+
 }
diff --git a/php/GamingPlatform/Api/Chat/V1/WriteMessage.php b/php/GamingPlatform/Api/Chat/V1/WriteMessage.php
new file mode 100644
index 0000000..a10670e
--- /dev/null
+++ b/php/GamingPlatform/Api/Chat/V1/WriteMessage.php
@@ -0,0 +1,150 @@
+<?php
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# source: gamingplatform/api/chat/v1/messaging.proto
+
+namespace GamingPlatform\Api\Chat\V1;
+
+use Google\Protobuf\Internal\GPBType;
+use Google\Protobuf\Internal\RepeatedField;
+use Google\Protobuf\Internal\GPBUtil;
+
+/**
+ * Generated from protobuf message <code>gamingplatform.api.chat.v1.WriteMessage</code>
+ */
+class WriteMessage extends \Google\Protobuf\Internal\Message
+{
+    /**
+     * This applies per author within a chat.
+     * Don't set if no idempotency is needed.
+     *
+     * Generated from protobuf field <code>string idempotency_key = 1;</code>
+     */
+    protected $idempotency_key = '';
+    /**
+     * Generated from protobuf field <code>string chat_id = 2;</code>
+     */
+    protected $chat_id = '';
+    /**
+     * Generated from protobuf field <code>string author_id = 3;</code>
+     */
+    protected $author_id = '';
+    /**
+     * Generated from protobuf field <code>string message = 4;</code>
+     */
+    protected $message = '';
+
+    /**
+     * Constructor.
+     *
+     * @param array $data {
+     *     Optional. Data for populating the Message object.
+     *
+     *     @type string $idempotency_key
+     *           This applies per author within a chat.
+     *           Don't set if no idempotency is needed.
+     *     @type string $chat_id
+     *     @type string $author_id
+     *     @type string $message
+     * }
+     */
+    public function __construct($data = NULL) {
+        \GamingPlatform\Api\GPBMetadata\Chat\V1\Messaging::initOnce();
+        parent::__construct($data);
+    }
+
+    /**
+     * This applies per author within a chat.
+     * Don't set if no idempotency is needed.
+     *
+     * Generated from protobuf field <code>string idempotency_key = 1;</code>
+     * @return string
+     */
+    public function getIdempotencyKey()
+    {
+        return $this->idempotency_key;
+    }
+
+    /**
+     * This applies per author within a chat.
+     * Don't set if no idempotency is needed.
+     *
+     * Generated from protobuf field <code>string idempotency_key = 1;</code>
+     * @param string $var
+     * @return $this
+     */
+    public function setIdempotencyKey($var)
+    {
+        GPBUtil::checkString($var, True);
+        $this->idempotency_key = $var;
+
+        return $this;
+    }
+
+    /**
+     * Generated from protobuf field <code>string chat_id = 2;</code>
+     * @return string
+     */
+    public function getChatId()
+    {
+        return $this->chat_id;
+    }
+
+    /**
+     * Generated from protobuf field <code>string chat_id = 2;</code>
+     * @param string $var
+     * @return $this
+     */
+    public function setChatId($var)
+    {
+        GPBUtil::checkString($var, True);
+        $this->chat_id = $var;
+
+        return $this;
+    }
+
+    /**
+     * Generated from protobuf field <code>string author_id = 3;</code>
+     * @return string
+     */
+    public function getAuthorId()
+    {
+        return $this->author_id;
+    }
+
+    /**
+     * Generated from protobuf field <code>string author_id = 3;</code>
+     * @param string $var
+     * @return $this
+     */
+    public function setAuthorId($var)
+    {
+        GPBUtil::checkString($var, True);
+        $this->author_id = $var;
+
+        return $this;
+    }
+
+    /**
+     * Generated from protobuf field <code>string message = 4;</code>
+     * @return string
+     */
+    public function getMessage()
+    {
+        return $this->message;
+    }
+
+    /**
+     * Generated from protobuf field <code>string message = 4;</code>
+     * @param string $var
+     * @return $this
+     */
+    public function setMessage($var)
+    {
+        GPBUtil::checkString($var, True);
+        $this->message = $var;
+
+        return $this;
+    }
+
+}
+
diff --git a/php/GamingPlatform/Api/Chat/V1/WriteMessageResponse.php b/php/GamingPlatform/Api/Chat/V1/WriteMessageResponse.php
new file mode 100644
index 0000000..e63bdd1
--- /dev/null
+++ b/php/GamingPlatform/Api/Chat/V1/WriteMessageResponse.php
@@ -0,0 +1,31 @@
+<?php
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# source: gamingplatform/api/chat/v1/messaging.proto
+
+namespace GamingPlatform\Api\Chat\V1;
+
+use Google\Protobuf\Internal\GPBType;
+use Google\Protobuf\Internal\RepeatedField;
+use Google\Protobuf\Internal\GPBUtil;
+
+/**
+ * Generated from protobuf message <code>gamingplatform.api.chat.v1.WriteMessageResponse</code>
+ */
+class WriteMessageResponse extends \Google\Protobuf\Internal\Message
+{
+
+    /**
+     * Constructor.
+     *
+     * @param array $data {
+     *     Optional. Data for populating the Message object.
+     *
+     * }
+     */
+    public function __construct($data = NULL) {
+        \GamingPlatform\Api\GPBMetadata\Chat\V1\Messaging::initOnce();
+        parent::__construct($data);
+    }
+
+}
+
diff --git a/php/GamingPlatform/Api/GPBMetadata/Chat/V1/Messaging.php b/php/GamingPlatform/Api/GPBMetadata/Chat/V1/Messaging.php
index 65ea638..5356470 100644
--- a/php/GamingPlatform/Api/GPBMetadata/Chat/V1/Messaging.php
+++ b/php/GamingPlatform/Api/GPBMetadata/Chat/V1/Messaging.php
@@ -16,7 +16,7 @@ public static function initOnce() {
         }
         $pool->internalAddGeneratedFile(
             '
-Ì
+Â
 *gamingplatform/api/chat/v1/messaging.protogamingplatform.api.chat.v1"P
 InitiateChat
 idempotency_key
 
(	
@@ -24,7 +24,13 @@ public static function initOnce() {
 authors (	"?
 InitiateChatResponse
 chat_id
 
(	
-correlation_id 
(	"m
+correlation_id 
(	"\\
+WriteMessage
+idempotency_key
 
(	
+chat_id 
(	
+	author_id 
(	
+message 
(	"
+WriteMessageResponse"m
 MessageWritten
 chat_id
 
(	
 
diff --git a/schema/gamingplatform/api/chat/v1/messaging.proto b/schema/gamingplatform/api/chat/v1/messaging.proto
index cfd36c4..0413603 100644
--- a/schema/gamingplatform/api/chat/v1/messaging.proto
+++ b/schema/gamingplatform/api/chat/v1/messaging.proto
@@ -17,6 +17,18 @@ message InitiateChatResponse {
   string correlation_id = 2;
 }
 
+message WriteMessage {
+  // This applies per author within a chat.
+  // Don't set if no idempotency is needed.
+  string idempotency_key = 1;
+  string chat_id = 2;
+  string author_id = 3;
+  string message = 4;
+}
+
+message WriteMessageResponse {
+}
+
 message MessageWritten {
   string chat_id = 1;
   string message_id = 2;