diff --git a/output/openapi/elasticsearch-openapi.json b/output/openapi/elasticsearch-openapi.json
index ea702e6e12..487808fd13 100644
--- a/output/openapi/elasticsearch-openapi.json
+++ b/output/openapi/elasticsearch-openapi.json
@@ -65682,6 +65682,13 @@
       "_types.mapping:RuntimeField": {
         "type": "object",
         "properties": {
+          "fields": {
+            "description": "For type `composite`",
+            "type": "object",
+            "additionalProperties": {
+              "$ref": "#/components/schemas/_types.mapping:CompositeSubField"
+            }
+          },
           "fetch_fields": {
             "description": "For type `lookup`",
             "type": "array",
@@ -65716,18 +65723,15 @@
           "type"
         ]
       },
-      "_types.mapping:RuntimeFieldFetchFields": {
+      "_types.mapping:CompositeSubField": {
         "type": "object",
         "properties": {
-          "field": {
-            "$ref": "#/components/schemas/_types:Field"
-          },
-          "format": {
-            "type": "string"
+          "type": {
+            "$ref": "#/components/schemas/_types.mapping:RuntimeFieldType"
           }
         },
         "required": [
-          "field"
+          "type"
         ]
       },
       "_types.mapping:RuntimeFieldType": {
@@ -65744,6 +65748,20 @@
           "lookup"
         ]
       },
+      "_types.mapping:RuntimeFieldFetchFields": {
+        "type": "object",
+        "properties": {
+          "field": {
+            "$ref": "#/components/schemas/_types:Field"
+          },
+          "format": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "field"
+        ]
+      },
       "autoscaling.get_autoscaling_capacity:AutoscalingDeciders": {
         "type": "object",
         "properties": {
diff --git a/output/openapi/elasticsearch-serverless-openapi.json b/output/openapi/elasticsearch-serverless-openapi.json
index 682a5d3080..0d38e9dc99 100644
--- a/output/openapi/elasticsearch-serverless-openapi.json
+++ b/output/openapi/elasticsearch-serverless-openapi.json
@@ -41998,6 +41998,13 @@
       "_types.mapping:RuntimeField": {
         "type": "object",
         "properties": {
+          "fields": {
+            "description": "For type `composite`",
+            "type": "object",
+            "additionalProperties": {
+              "$ref": "#/components/schemas/_types.mapping:CompositeSubField"
+            }
+          },
           "fetch_fields": {
             "description": "For type `lookup`",
             "type": "array",
@@ -42032,18 +42039,15 @@
           "type"
         ]
       },
-      "_types.mapping:RuntimeFieldFetchFields": {
+      "_types.mapping:CompositeSubField": {
         "type": "object",
         "properties": {
-          "field": {
-            "$ref": "#/components/schemas/_types:Field"
-          },
-          "format": {
-            "type": "string"
+          "type": {
+            "$ref": "#/components/schemas/_types.mapping:RuntimeFieldType"
           }
         },
         "required": [
-          "field"
+          "type"
         ]
       },
       "_types.mapping:RuntimeFieldType": {
@@ -42060,6 +42064,20 @@
           "lookup"
         ]
       },
+      "_types.mapping:RuntimeFieldFetchFields": {
+        "type": "object",
+        "properties": {
+          "field": {
+            "$ref": "#/components/schemas/_types:Field"
+          },
+          "format": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "field"
+        ]
+      },
       "_types:Refresh": {
         "type": "string",
         "enum": [
diff --git a/output/schema/schema-serverless.json b/output/schema/schema-serverless.json
index e1bb4d9c6f..e6d8da5a4d 100644
--- a/output/schema/schema-serverless.json
+++ b/output/schema/schema-serverless.json
@@ -65845,6 +65845,29 @@
         "namespace": "_types.mapping"
       },
       "properties": [
+        {
+          "description": "For type `composite`",
+          "name": "fields",
+          "required": false,
+          "type": {
+            "key": {
+              "kind": "instance_of",
+              "type": {
+                "name": "string",
+                "namespace": "_builtins"
+              }
+            },
+            "kind": "dictionary_of",
+            "singleKey": false,
+            "value": {
+              "kind": "instance_of",
+              "type": {
+                "name": "CompositeSubField",
+                "namespace": "_types.mapping"
+              }
+            }
+          }
+        },
         {
           "description": "For type `lookup`",
           "name": "fetch_fields",
@@ -65935,40 +65958,28 @@
           }
         }
       ],
-      "specLocation": "_types/mapping/RuntimeFields.ts#L26-L48"
+      "specLocation": "_types/mapping/RuntimeFields.ts#L26-L50"
     },
     {
       "kind": "interface",
       "name": {
-        "name": "RuntimeFieldFetchFields",
+        "name": "CompositeSubField",
         "namespace": "_types.mapping"
       },
       "properties": [
         {
-          "name": "field",
+          "name": "type",
           "required": true,
           "type": {
             "kind": "instance_of",
             "type": {
-              "name": "Field",
-              "namespace": "_types"
-            }
-          }
-        },
-        {
-          "name": "format",
-          "required": false,
-          "type": {
-            "kind": "instance_of",
-            "type": {
-              "name": "string",
-              "namespace": "_builtins"
+              "name": "RuntimeFieldType",
+              "namespace": "_types.mapping"
             }
           }
         }
       ],
-      "shortcutProperty": "field",
-      "specLocation": "_types/mapping/RuntimeFields.ts#L50-L54"
+      "specLocation": "_types/mapping/RuntimeFields.ts#L52-L54"
     },
     {
       "kind": "enum",
@@ -66005,7 +66016,40 @@
         "name": "RuntimeFieldType",
         "namespace": "_types.mapping"
       },
-      "specLocation": "_types/mapping/RuntimeFields.ts#L56-L66"
+      "specLocation": "_types/mapping/RuntimeFields.ts#L62-L72"
+    },
+    {
+      "kind": "interface",
+      "name": {
+        "name": "RuntimeFieldFetchFields",
+        "namespace": "_types.mapping"
+      },
+      "properties": [
+        {
+          "name": "field",
+          "required": true,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "Field",
+              "namespace": "_types"
+            }
+          }
+        },
+        {
+          "name": "format",
+          "required": false,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "string",
+              "namespace": "_builtins"
+            }
+          }
+        }
+      ],
+      "shortcutProperty": "field",
+      "specLocation": "_types/mapping/RuntimeFields.ts#L56-L60"
     },
     {
       "kind": "interface",
diff --git a/output/schema/schema.json b/output/schema/schema.json
index c162abe023..98ff02622c 100644
--- a/output/schema/schema.json
+++ b/output/schema/schema.json
@@ -71089,6 +71089,27 @@
       ],
       "specLocation": "_types/mapping/specialized.ts#L33-L41"
     },
+    {
+      "kind": "interface",
+      "name": {
+        "name": "CompositeSubField",
+        "namespace": "_types.mapping"
+      },
+      "properties": [
+        {
+          "name": "type",
+          "required": true,
+          "type": {
+            "kind": "instance_of",
+            "type": {
+              "name": "RuntimeFieldType",
+              "namespace": "_types.mapping"
+            }
+          }
+        }
+      ],
+      "specLocation": "_types/mapping/RuntimeFields.ts#L52-L54"
+    },
     {
       "kind": "interface",
       "inherits": {
@@ -74634,6 +74655,29 @@
         "namespace": "_types.mapping"
       },
       "properties": [
+        {
+          "description": "For type `composite`",
+          "name": "fields",
+          "required": false,
+          "type": {
+            "kind": "dictionary_of",
+            "key": {
+              "kind": "instance_of",
+              "type": {
+                "name": "string",
+                "namespace": "_builtins"
+              }
+            },
+            "singleKey": false,
+            "value": {
+              "kind": "instance_of",
+              "type": {
+                "name": "CompositeSubField",
+                "namespace": "_types.mapping"
+              }
+            }
+          }
+        },
         {
           "description": "For type `lookup`",
           "name": "fetch_fields",
@@ -74724,7 +74768,7 @@
           }
         }
       ],
-      "specLocation": "_types/mapping/RuntimeFields.ts#L26-L48"
+      "specLocation": "_types/mapping/RuntimeFields.ts#L26-L50"
     },
     {
       "kind": "interface",
@@ -74757,7 +74801,7 @@
         }
       ],
       "shortcutProperty": "field",
-      "specLocation": "_types/mapping/RuntimeFields.ts#L50-L54"
+      "specLocation": "_types/mapping/RuntimeFields.ts#L56-L60"
     },
     {
       "kind": "enum",
@@ -74794,7 +74838,7 @@
         "name": "RuntimeFieldType",
         "namespace": "_types.mapping"
       },
-      "specLocation": "_types/mapping/RuntimeFields.ts#L56-L66"
+      "specLocation": "_types/mapping/RuntimeFields.ts#L62-L72"
     },
     {
       "kind": "type_alias",
diff --git a/output/typescript/types.ts b/output/typescript/types.ts
index 941e0b1afc..521578ed9a 100644
--- a/output/typescript/types.ts
+++ b/output/typescript/types.ts
@@ -5230,6 +5230,10 @@ export interface MappingCompletionProperty extends MappingDocValuesPropertyBase
   type: 'completion'
 }
 
+export interface MappingCompositeSubField {
+  type: MappingRuntimeFieldType
+}
+
 export interface MappingConstantKeywordProperty extends MappingPropertyBase {
   value?: any
   type: 'constant_keyword'
@@ -5573,6 +5577,7 @@ export interface MappingRoutingField {
 }
 
 export interface MappingRuntimeField {
+  fields?: Record<string, MappingCompositeSubField>
   fetch_fields?: (MappingRuntimeFieldFetchFields | Field)[]
   format?: string
   input_field?: Field
diff --git a/specification/_types/mapping/RuntimeFields.ts b/specification/_types/mapping/RuntimeFields.ts
index b5ad85f52d..62160a46f7 100644
--- a/specification/_types/mapping/RuntimeFields.ts
+++ b/specification/_types/mapping/RuntimeFields.ts
@@ -24,6 +24,8 @@ import { Script } from '@_types/Scripting'
 export type RuntimeFields = Dictionary<Field, RuntimeField>
 
 export class RuntimeField {
+  /** For type `composite` */
+  fields?: Dictionary<string, CompositeSubField>
   /** For type `lookup` */
   fetch_fields?: RuntimeFieldFetchFields[]
   /**
@@ -47,6 +49,10 @@ export class RuntimeField {
   type: RuntimeFieldType
 }
 
+class CompositeSubField {
+  type: RuntimeFieldType
+}
+
 /** @shortcut_property field */
 export class RuntimeFieldFetchFields {
   field: Field