[DOCS]: Clarify GET / response on Serverless

specification/_global/info/RootNodeInfoRequest.ts

@@ -22,6 +22,7 @@ import { RequestBase } from '@_types/Base'
 /**
  * Get cluster info.
  * Get basic build, version, and cluster information.
+ * ::: In Serverless, this API is retained for backward compatibility only. Some response fields, such as the version number, should be ignored.
  * @rest_spec_name info
  * @availability stack stability=stable
  * @availability serverless stability=stable visibility=public

specification/_global/info/examples/response/RootNodeInfoResponseExample1.yaml

@@ -1,19 +1,19 @@
-# summary: ''
-description: A successful response from `GET /`s.
+summary: Stack response
+description: A successful response from `GET /`.
 # type: response
 # response_code: 200
 value:
  name: instance-0000000000
  cluster_name: my_test_cluster
- cluster_uuid: 5QaxoN0pRZuOmWSxstBBwQ
+ cluster_uuid: zk-HjQtYQGyL3NFSSu7InA
  version:
- build_date: '2024-02-01T13:07:13.727175297Z'
- minimum_wire_compatibility_version: 7.17.0
- build_hash: 6185ba65d27469afabc9bc951cded6c17c21e3f3
- number: 8.12.1
- lucene_version: 9.9.2
- minimum_index_compatibility_version: 7.0.0
+ number: 9.1.0
  build_flavor: default
- build_snapshot: false
  build_type: docker
+ build_hash: 00000000
+ build_date: 2025-07-09T22:10:13.578182715Z
+ build_snapshot: false
+ lucene_version: 10.2.2
+ minimum_wire_compatibility_version: 8.19.0
+ minimum_index_compatibility_version: 8.0.0
  tagline: 'You Know, for Search'

specification/_global/info/examples/response/RootNodeInfoResponseExample2.yaml

@@ -0,0 +1,19 @@
+summary: Serverless response
+description: A successful response from `GET /` on Serverless. This API is retained for backward compatibility only. Some fields, such as the version number, return static values and should be ignored.
+# type: response
+# response_code: 200
+value:
+ name: serverless
+ cluster_name: my_test_serverless_cluster
+ cluster_uuid: 8xx0pi24Squnf4PFDOAtwg
+ version:
+ number: 8.11.0
+ build_flavor: serverless
+ build_type: docker
+ build_hash: 00000000
+ build_date: 2023-10-31
+ build_snapshot: false
+ lucene_version: 9.7.0
+ minimum_wire_compatibility_version: 8.11.0
+ minimum_index_compatibility_version: 8.11.0
+ tagline: 'You Know, for Search'

specification/_types/Base.ts

@@ -110,6 +110,9 @@ export class ElasticsearchVersionInfo {
  minimum_wire_compatibility_version: VersionString
  /**
  * The Elasticsearch version number.
+ *
+ * ::: IMPORTANT: For Serverless deployments, this static value is always `8.11.0` and is used solely for backward compatibility with legacy clients.
+ * Serverless environments are versionless and automatically upgraded, so this value can be safely ignored.
  */
  number: string
 }