diff --git a/openapi/openapiv2.json b/openapi/openapiv2.json
index 57fc9540..f9eba246 100644
--- a/openapi/openapiv2.json
+++ b/openapi/openapiv2.json
@@ -13835,6 +13835,10 @@
         "priority": {
           "$ref": "#/definitions/v1Priority",
           "title": "Priority metadata"
+        },
+        "createRequestId": {
+          "type": "string",
+          "description": "A unique identifier for the request to start this child workflow execution. This is used to\ndeduplicate requests to start a child workflow execution with the same workflow ID."
         }
       }
     },
diff --git a/openapi/openapiv3.yaml b/openapi/openapiv3.yaml
index 1880a9b3..3e1cf149 100644
--- a/openapi/openapiv3.yaml
+++ b/openapi/openapiv3.yaml
@@ -11086,6 +11086,11 @@ components:
           allOf:
             - $ref: '#/components/schemas/Priority'
           description: Priority metadata
+        createRequestId:
+          type: string
+          description: |-
+            A unique identifier for the request to start this child workflow execution. This is used to
+             deduplicate requests to start a child workflow execution with the same workflow ID.
     StartWorkflowExecutionRequest:
       type: object
       properties:
diff --git a/temporal/api/history/v1/message.proto b/temporal/api/history/v1/message.proto
index b9e258fd..718e2f2c 100644
--- a/temporal/api/history/v1/message.proto
+++ b/temporal/api/history/v1/message.proto
@@ -665,6 +665,9 @@ message StartChildWorkflowExecutionInitiatedEventAttributes {
     bool inherit_build_id = 19;
     // Priority metadata
     temporal.api.common.v1.Priority priority = 20;
+    // A unique identifier for the request to start this child workflow execution. This is used to
+    // deduplicate requests to start a child workflow execution with the same workflow ID.
+    string create_request_id = 21;
 }
 
 message StartChildWorkflowExecutionFailedEventAttributes {