diff --git a/specification/_doc_ids/table.csv b/specification/_doc_ids/table.csv
index ddd47afb65..f67616115a 100644
--- a/specification/_doc_ids/table.csv
+++ b/specification/_doc_ids/table.csv
@@ -358,6 +358,7 @@ inference-api-put-anthropic,https://www.elastic.co/docs/api/doc/elasticsearch/op
 inference-api-put-azureaistudio,https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-azureaistudio,https://www.elastic.co/guide/en/elasticsearch/reference/8.18/infer-service-azure-ai-studio.html,
 inference-api-put-azureopenai,https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-azureopenai,https://www.elastic.co/guide/en/elasticsearch/reference/8.18/infer-service-azure-openai.html,
 inference-api-put-cohere,https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-cohere,https://www.elastic.co/guide/en/elasticsearch/reference/8.18/infer-service-cohere.html,
+inference-api-put-custom,https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-custom,https://www.elastic.co/guide/en/elasticsearch/reference/8.19/infer-service-custom.html,
 inference-api-put-deepseek,https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-deepseek,https://www.elastic.co/guide/en/elasticsearch/reference/8.18/infer-service-deepseek.html,
 inference-api-put-eis,https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-eis,,
 inference-api-put-elasticsearch,https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-elasticsearch,https://www.elastic.co/guide/en/elasticsearch/reference/8.18/infer-service-elasticsearch.html,
diff --git a/specification/_json_spec/inference.put_custom.json b/specification/_json_spec/inference.put_custom.json
new file mode 100644
index 0000000000..c12108683d
--- /dev/null
+++ b/specification/_json_spec/inference.put_custom.json
@@ -0,0 +1,35 @@
+{
+  "inference.put_custom": {
+    "documentation": {
+      "url": "https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-inference-put-custom",
+      "description": "Configure a custom inference endpoint"
+    },
+    "stability": "stable",
+    "visibility": "public",
+    "headers": {
+      "accept": ["application/json"],
+      "content_type": ["application/json"]
+    },
+    "url": {
+      "paths": [
+        {
+          "path": "/_inference/{task_type}/{custom_inference_id}",
+          "methods": ["PUT"],
+          "parts": {
+            "task_type": {
+              "type": "string",
+              "description": "The task type"
+            },
+            "custom_inference_id": {
+              "type": "string",
+              "description": "The inference Id"
+            }
+          }
+        }
+      ]
+    },
+    "body": {
+      "description": "The inference endpoint's task and service settings"
+    }
+  }
+}
diff --git a/specification/inference/_types/CommonTypes.ts b/specification/inference/_types/CommonTypes.ts
index e097e0cd6a..c4799c1705 100644
--- a/specification/inference/_types/CommonTypes.ts
+++ b/specification/inference/_types/CommonTypes.ts
@@ -758,6 +758,136 @@ export class CohereTaskSettings {
   truncate?: CohereTruncateType
 }
 
+export class CustomServiceSettings {
+  /**
+   * Specifies the HTTPS header parameters – such as `Authentication` or `Contet-Type` – that are required to access the custom service.
+   * For example:
+   * ```
+   * "headers":{
+   *   "Authorization": "Bearer ${api_key}",
+   *   "Content-Type": "application/json;charset=utf-8"
+   * }
+   * ```
+   */
+  headers?: UserDefinedValue
+  /**
+   * The request configuration object.
+   */
+  request: CustomRequestParams
+  /**
+   * The response configuration object.
+   */
+  response: CustomResponseParams
+  /**
+   * Specifies secret parameters, like `api_key` or `api_token`, that are required to access the custom service.
+   * For example:
+   * ```
+   * "secret_parameters":{
+   *   "api_key":"<api_key>"
+   * }
+   * ```
+   */
+  secret_parameters: UserDefinedValue
+  /**
+   * The URL endpoint to use for the requests.
+   */
+  url?: string
+}
+
+export class CustomRequestParams {
+  /**
+   * The body structure of the request. It requires passing in the string-escaped result of the JSON format HTTP request body.
+   * For example:
+   * ```
+   * "request":{
+   *   "content":"{\"input\":${input}}"
+   * }
+   * ```
+   * > info
+   * > The content string needs to be a single line except using the Kibana console.
+   */
+  content: string
+}
+
+export class CustomResponseParams {
+  /**
+   * Specifies the path to the error message in the response from the custom service.
+   * For example:
+   * ```
+   * "response": {
+   *   "error_parser": {
+   *     "path": "$.error.message"
+   *   }
+   * }
+   * ```
+   */
+  error_parser: UserDefinedValue
+  /**
+   * Specifies the JSON parser that is used to parse the response from the custom service.
+   * Different task types require different json_parser parameters.
+   * For example:
+   * ```
+   * # text_embedding
+   * "response":{
+   *   "json_parser":{
+   *     "text_embeddings":"$.result.embeddings[*].embedding"
+   *   }
+   * }
+   *
+   * # sparse_embedding
+   * "response":{
+   *   "json_parser":{
+   *     "token_path":"$.result[*].embeddings[*].token",
+   *     "weight_path":"$.result[*].embeddings[*].weight"
+   *   }
+   * }
+   *
+   * # rerank
+   * "response":{
+   *   "json_parser":{
+   *     "reranked_index":"$.result.scores[*].index",    // optional
+   *     "relevance_score":"$.result.scores[*].score",
+   *     "document_text":"xxx"    // optional
+   *   }
+   * }
+   *
+   * # completion
+   * "response":{
+   *   "json_parser":{
+   *     "completion_result":"$.result.text"
+   *   }
+   * }
+   */
+  json_parser: UserDefinedValue
+}
+
+export enum CustomTaskType {
+  text_embedding,
+  sparse_embedding,
+  rerank,
+  completion
+}
+
+export enum CustomServiceType {
+  custom
+}
+
+export class CustomTaskSettings {
+  /**
+   * Specifies parameters that are required to run the custom service. The parameters depend on the model your custom service uses.
+   * For example:
+   * ```
+   * "task_settings":{
+   *   "parameters":{
+   *     "input_type":"query",
+   *     "return_token":true
+   *   }
+   * }
+   * ```
+   */
+  parameters?: UserDefinedValue
+}
+
 export class EisServiceSettings {
   /**
    * The name of the model to use for the inference task.
diff --git a/specification/inference/_types/Services.ts b/specification/inference/_types/Services.ts
index 720dd9ea43..802db7decc 100644
--- a/specification/inference/_types/Services.ts
+++ b/specification/inference/_types/Services.ts
@@ -27,6 +27,7 @@ import {
   TaskTypeAzureAIStudio,
   TaskTypeAzureOpenAI,
   TaskTypeCohere,
+  TaskTypeCustom,
   TaskTypeDeepSeek,
   TaskTypeElasticsearch,
   TaskTypeELSER,
@@ -75,18 +76,6 @@ export class InferenceEndpointInfo extends InferenceEndpoint {
    */
   task_type: TaskType
 }
-
-export class InferenceEndpointInfoJinaAi extends InferenceEndpoint {
-  /**
-   * The inference Id
-   */
-  inference_id: string
-  /**
-   * The task type
-   */
-  task_type: TaskTypeJinaAi
-}
-
 export class InferenceEndpointInfoAlibabaCloudAI extends InferenceEndpoint {
   /**
    * The inference Id
@@ -153,6 +142,16 @@ export class InferenceEndpointInfoCohere extends InferenceEndpoint {
   task_type: TaskTypeCohere
 }
 
+export class InferenceEndpointInfoCustom extends InferenceEndpoint {
+  /**
+   * The inference Id
+   */
+  inference_id: string
+  /**
+   * The task type
+   */
+  task_type: TaskTypeCustom
+}
 export class InferenceEndpointInfoDeepSeek extends InferenceEndpoint {
   /**
    * The inference Id
@@ -219,6 +218,17 @@ export class InferenceEndpointInfoHuggingFace extends InferenceEndpoint {
   task_type: TaskTypeHuggingFace
 }
 
+export class InferenceEndpointInfoJinaAi extends InferenceEndpoint {
+  /**
+   * The inference Id
+   */
+  inference_id: string
+  /**
+   * The task type
+   */
+  task_type: TaskTypeJinaAi
+}
+
 export class InferenceEndpointInfoMistral extends InferenceEndpoint {
   /**
    * The inference Id
diff --git a/specification/inference/_types/TaskType.ts b/specification/inference/_types/TaskType.ts
index 670dc3d3e5..6daed0d281 100644
--- a/specification/inference/_types/TaskType.ts
+++ b/specification/inference/_types/TaskType.ts
@@ -65,6 +65,13 @@ export enum TaskTypeCohere {
   completion
 }
 
+export enum TaskTypeCustom {
+  text_embedding,
+  sparse_embedding,
+  rerank,
+  completion
+}
+
 export enum TaskTypeDeepSeek {
   completion,
   chat_completion
diff --git a/specification/inference/put_custom/PutCustomRequest.ts b/specification/inference/put_custom/PutCustomRequest.ts
new file mode 100644
index 0000000000..fab798391a
--- /dev/null
+++ b/specification/inference/put_custom/PutCustomRequest.ts
@@ -0,0 +1,78 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { RequestBase } from '@_types/Base'
+import { Id } from '@_types/common'
+import {
+  CustomServiceSettings,
+  CustomServiceType,
+  CustomTaskSettings,
+  CustomTaskType
+} from '@inference/_types/CommonTypes'
+import { InferenceChunkingSettings } from '@inference/_types/Services'
+
+/**
+ * Create a custom inference endpoint.
+ *
+ * You can create an inference endpoint to perform an inference task with a custom model that supports the HTTP format.
+ * @rest_spec_name inference.put_custom
+ * @availability stack since=8.13.0 stability=stable visibility=public
+ * @availability serverless stability=stable visibility=public
+ * @cluster_privileges manage_inference
+ * @doc_id inference-api-put-custom
+ */
+export interface Request extends RequestBase {
+  urls: [
+    {
+      path: '/_inference/{task_type}/{custom_inference_id}'
+      methods: ['PUT']
+    }
+  ]
+  path_parts: {
+    /**
+     * The type of the inference task that the model will perform.
+     */
+    task_type: CustomTaskType
+    /**
+     * The unique identifier of the inference endpoint.
+     */
+    custom_inference_id: Id
+  }
+  body: {
+    /**
+     * The chunking configuration object.
+     * @ext_doc_id inference-chunking
+     */
+    chunking_settings?: InferenceChunkingSettings
+    /**
+     * The type of service supported for the specified task type. In this case, `custom`.
+     */
+    service: CustomServiceType
+    /**
+     * Settings used to install the inference model.
+     * These settings are specific to the `custom` service.
+     */
+    service_settings: CustomServiceSettings
+    /**
+     * Settings to configure the inference task.
+     * These settings are specific to the task type you specified.
+     */
+    task_settings?: CustomTaskSettings
+  }
+}
diff --git a/specification/inference/put_custom/PutCustomResponse.ts b/specification/inference/put_custom/PutCustomResponse.ts
new file mode 100644
index 0000000000..c09467c944
--- /dev/null
+++ b/specification/inference/put_custom/PutCustomResponse.ts
@@ -0,0 +1,25 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { InferenceEndpointInfoCustom } from '@inference/_types/Services'
+
+export class Response {
+  /** @codegen_name endpoint_info */
+  body: InferenceEndpointInfoCustom
+}
diff --git a/specification/inference/put_custom/examples/PutCustomRequestExample1.yaml b/specification/inference/put_custom/examples/PutCustomRequestExample1.yaml
new file mode 100644
index 0000000000..dabe71ed86
--- /dev/null
+++ b/specification/inference/put_custom/examples/PutCustomRequestExample1.yaml
@@ -0,0 +1,24 @@
+summary: Custom text embedding task (OpenAI)
+description: Run `PUT _inference/text_embedding/custom-embeddings` to create an inference endpoint that performs a text embedding task.
+method_request: 'PUT _inference/text_embedding/custom-embeddings'
+# type: "request"
+value: |-
+  {
+      "service": "custom",
+      "service_settings": {
+          "secret_parameters": {
+              "api_key": "<api key>"
+          },
+          "url": "https://api.openai.com/v1/embeddings",
+          "headers": {
+              "Authorization": "Bearer ${api_key}",
+              "Content-Type": "application/json;charset=utf-8"
+          },
+          "request": "{\"input\": ${input}, \"model\": \"text-embedding-3-small\"}",
+          "response": {
+              "json_parser": {
+                  "text_embeddings": "$.data[*].embedding[*]"
+              }
+          }
+      }
+  }
diff --git a/specification/inference/put_custom/examples/PutCustomRequestExample2.yaml b/specification/inference/put_custom/examples/PutCustomRequestExample2.yaml
new file mode 100644
index 0000000000..1fb61b58c1
--- /dev/null
+++ b/specification/inference/put_custom/examples/PutCustomRequestExample2.yaml
@@ -0,0 +1,25 @@
+summary: Custom rerank task (Cohere APIv2)
+description: Run `PUT _inference/rerank/custom-rerank` to create an inference endpoint that performs a rerank task.
+method_request: 'PUT _inference/rerank/custom-rerank'
+# type: "request"
+value: |-
+  {
+    "service": "custom",
+    "service_settings": {
+        "secret_parameters": {
+            "api_key": "<api key>"
+        },
+        "url": "https://api.cohere.com/v2/rerank",
+        "headers": {
+            "Authorization": "bearer ${api_key}",
+            "Content-Type": "application/json"
+        },
+        "request": "{\"documents\": ${input}, \"query\": ${query}, \"model\": \"rerank-v3.5\"}",
+        "response": {
+            "json_parser": {
+                "reranked_index":"$.results[*].index",
+                "relevance_score":"$.results[*].relevance_score"
+            }
+        }
+    }
+  }
diff --git a/specification/inference/put_custom/examples/PutCustomRequestExample3.yaml b/specification/inference/put_custom/examples/PutCustomRequestExample3.yaml
new file mode 100644
index 0000000000..70e5609051
--- /dev/null
+++ b/specification/inference/put_custom/examples/PutCustomRequestExample3.yaml
@@ -0,0 +1,31 @@
+summary: Custom text embedding task (Cohere APIv2)
+description: Run `PUT _inference/text_embedding/custom-text-embedding` to create an inference endpoint that performs a text embedding task.
+method_request: 'PUT _inference/text_embedding/custom-text-embedding'
+# type: "request"
+value: |-
+  {
+    "service": "custom",
+    "service_settings": {
+        "secret_parameters": {
+            "api_key": "<api key>"
+        },
+        "url": "https://api.cohere.com/v2/embed",
+        "headers": {
+            "Authorization": "bearer ${api_key}",
+            "Content-Type": "application/json"
+        },
+        "request": "{\"texts\": ${input}, \"model\": \"embed-v4.0\", \"input_type\": ${input_type}}",
+        "response": {
+            "json_parser": {
+                "text_embeddings":"$.embeddings.float[*]"
+            }
+        },
+        "input_type": {
+            "translation": {
+                "ingest": "search_document",
+                "search": "search_query"
+            },
+            "default": "search_document"
+        }
+    }
+  }
diff --git a/specification/inference/put_custom/examples/PutCustomRequestExample4.yaml b/specification/inference/put_custom/examples/PutCustomRequestExample4.yaml
new file mode 100644
index 0000000000..4ecaaf020b
--- /dev/null
+++ b/specification/inference/put_custom/examples/PutCustomRequestExample4.yaml
@@ -0,0 +1,25 @@
+summary: Custom rerank task (Jina AI)
+description: Run `PUT _inference/rerank/custom-rerank-jina` to create an inference endpoint that performs a rerank task.
+method_request: 'PUT _inference/rerank/custom-rerank-jina'
+# type: "request"
+value: |-
+  {
+    "service": "custom",
+    "service_settings": {
+      "secret_parameters": {
+        "api_key": "<api key>"
+      },    
+      "url": "https://api.jina.ai/v1/rerank",
+      "headers": {
+        "Content-Type": "application/json",
+        "Authorization": "Bearer ${api_key}"
+      },
+      "request": "{\"model\": \"jina-reranker-v2-base-multilingual\",\"query\": ${query},\"documents\":${input}}",
+      "response": {
+        "json_parser": {
+          "relevance_score": "$.results[*].relevance_score",
+          "reranked_index": "$.results[*].index"
+        }
+      }
+    }
+  }
diff --git a/specification/inference/put_custom/examples/PutCustomRequestExample5.yaml b/specification/inference/put_custom/examples/PutCustomRequestExample5.yaml
new file mode 100644
index 0000000000..c9f86dad8d
--- /dev/null
+++ b/specification/inference/put_custom/examples/PutCustomRequestExample5.yaml
@@ -0,0 +1,24 @@
+summary: Custom text embedding task (Hugging Face)
+description: Run `PUT _inference/text_embedding/custom-text-embedding-hf` to create an inference endpoint that performs a text embedding task by using the Qwen/Qwen3-Embedding-8B model.
+method_request: 'PUT _inference/text_embedding/custom-text-embedding-hf'
+# type: "request"
+value: |-
+  {
+    "service": "custom",
+    "service_settings": {
+        "secret_parameters": {
+            "api_key": "<api key>"
+        },
+        "url": "<dedicated inference endpoint on HF>/v1/embeddings",
+        "headers": {
+            "Authorization": "Bearer ${api_key}",
+            "Content-Type": "application/json"
+        },
+        "request": "{\"input\": ${input}}",
+        "response": {
+            "json_parser": {
+                "text_embeddings":"$.data[*].embedding[*]"
+            }
+        }
+    }
+  }
diff --git a/specification/inference/put_deepseek/request/PutDeepSeekRequestExample1.yaml b/specification/inference/put_deepseek/examples/PutDeepSeekRequestExample1.yaml
similarity index 100%
rename from specification/inference/put_deepseek/request/PutDeepSeekRequestExample1.yaml
rename to specification/inference/put_deepseek/examples/PutDeepSeekRequestExample1.yaml
diff --git a/specification/inference/put_deepseek/request/PutDeepSeekRequestExample2.yaml b/specification/inference/put_deepseek/examples/PutDeepSeekRequestExample2.yaml
similarity index 100%
rename from specification/inference/put_deepseek/request/PutDeepSeekRequestExample2.yaml
rename to specification/inference/put_deepseek/examples/PutDeepSeekRequestExample2.yaml