diff --git a/specification/eventgrid/Azure.Messaging.EventGrid.SystemEvents/Microsoft.Communication/AzureCommunicationServices.tsp b/specification/eventgrid/Azure.Messaging.EventGrid.SystemEvents/Microsoft.Communication/AzureCommunicationServices.tsp
index 2aeca813322a..333ac3176184 100644
--- a/specification/eventgrid/Azure.Messaging.EventGrid.SystemEvents/Microsoft.Communication/AzureCommunicationServices.tsp
+++ b/specification/eventgrid/Azure.Messaging.EventGrid.SystemEvents/Microsoft.Communication/AzureCommunicationServices.tsp
@@ -1081,6 +1081,9 @@ model AcsChatMessageEventBaseProperties extends AcsChatEventBaseProperties {
   /** The display name of the sender */
   senderDisplayName?: string;
 
+  /** The Sequence id of the message */
+  sequenceId?: int64;
+
   /** The original compose time of the message */
   @madeRequired(ServiceApiVersions.v2024_01_01)
   composeTime: utcDateTime;
@@ -1198,6 +1201,9 @@ model AcsChatMessageEventInThreadBaseProperties
   /** The display name of the sender */
   senderDisplayName?: string;
 
+  /** The Sequence id of the message */
+  sequenceId?: int64;
+
   /** The original compose time of the message */
   @madeRequired(ServiceApiVersions.v2024_01_01)
   composeTime: utcDateTime;
diff --git a/specification/eventgrid/data-plane/Microsoft.EventGrid/stable/2018-01-01/GeneratedSystemEvents.json b/specification/eventgrid/data-plane/Microsoft.EventGrid/stable/2018-01-01/GeneratedSystemEvents.json
index 2c507293a174..b531cd1c78be 100644
--- a/specification/eventgrid/data-plane/Microsoft.EventGrid/stable/2018-01-01/GeneratedSystemEvents.json
+++ b/specification/eventgrid/data-plane/Microsoft.EventGrid/stable/2018-01-01/GeneratedSystemEvents.json
@@ -457,6 +457,11 @@
           "type": "string",
           "description": "The display name of the sender"
         },
+        "sequenceId": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The Sequence id of the message"
+        },
         "composeTime": {
           "type": "string",
           "format": "date-time",
@@ -499,6 +504,11 @@
           "type": "string",
           "description": "The display name of the sender"
         },
+        "sequenceId": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The Sequence id of the message"
+        },
         "composeTime": {
           "type": "string",
           "format": "date-time",
diff --git a/specification/eventgrid/data-plane/Microsoft.EventGrid/stable/2024-01-01/GeneratedSystemEvents.json b/specification/eventgrid/data-plane/Microsoft.EventGrid/stable/2024-01-01/GeneratedSystemEvents.json
index b96ad6a64d81..005706ff932e 100644
--- a/specification/eventgrid/data-plane/Microsoft.EventGrid/stable/2024-01-01/GeneratedSystemEvents.json
+++ b/specification/eventgrid/data-plane/Microsoft.EventGrid/stable/2024-01-01/GeneratedSystemEvents.json
@@ -466,6 +466,11 @@
           "type": "string",
           "description": "The display name of the sender"
         },
+        "sequenceId": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The Sequence id of the message"
+        },
         "composeTime": {
           "type": "string",
           "format": "date-time",
@@ -510,6 +515,11 @@
           "type": "string",
           "description": "The display name of the sender"
         },
+        "sequenceId": {
+          "type": "integer",
+          "format": "int64",
+          "description": "The Sequence id of the message"
+        },
         "composeTime": {
           "type": "string",
           "format": "date-time",