diff --git a/openapi/openapiv2.json b/openapi/openapiv2.json
index 7e88dbd74..406738a8e 100644
--- a/openapi/openapiv2.json
+++ b/openapi/openapiv2.json
@@ -17957,6 +17957,10 @@
           "type": "integer",
           "format": "int32",
           "title": "Starting at 1, how many attempts there have been to complete this task"
+        },
+        "scheduleToStartTimeout": {
+          "type": "string",
+          "description": "Limits time a workflow task can stay in a task queue before a worker picks it up.\nOnly set when the server enforces a schedule-to-start timeout (e.g. sticky or speculative WT on normal queue).\n"
         }
       }
     },
diff --git a/openapi/openapiv3.yaml b/openapi/openapiv3.yaml
index 136e06d70..40196fc23 100644
--- a/openapi/openapiv3.yaml
+++ b/openapi/openapiv3.yaml
@@ -16718,6 +16718,15 @@ components:
           type: integer
           description: Starting at 1, how many attempts there have been to complete this task
           format: int32
+        scheduleToStartTimeout:
+          pattern: ^-?(?:0|[1-9][0-9]{0,11})(?:\.[0-9]{1,9})?s$
+          type: string
+          description: |-
+            Limits time a workflow task can stay in a task queue before a worker picks it up.
+             Only set when the server enforces a schedule-to-start timeout (e.g. sticky or speculative WT on normal queue).
+
+             (-- api-linter: core::0140::prepositions=disabled
+                 aip.dev/not-precedent: "to" is used to indicate interval. --)
     WorkflowTaskStartedEventAttributes:
       type: object
       properties:
diff --git a/temporal/api/history/v1/message.proto b/temporal/api/history/v1/message.proto
index 4243baab6..3c7cb9924 100644
--- a/temporal/api/history/v1/message.proto
+++ b/temporal/api/history/v1/message.proto
@@ -261,6 +261,13 @@ message WorkflowTaskScheduledEventAttributes {
     google.protobuf.Duration start_to_close_timeout = 2;
     // Starting at 1, how many attempts there have been to complete this task
     int32 attempt = 3;
+    // Limits time a workflow task can stay in a task queue before a worker picks it up.
+    // Only set when the server enforces a schedule-to-start timeout (e.g. sticky or speculative WT on normal queue).
+    //
+    // (-- api-linter: core::0140::prepositions=disabled
+    //     aip.dev/not-precedent: "to" is used to indicate interval. --)
+    google.protobuf.Duration schedule_to_start_timeout = 4;
+
 }
 
 message WorkflowTaskStartedEventAttributes {