Add optional status notifications for tasks

Author: LucaButBoring

docs/specification/draft/basic/utilities/tasks.mdx

@@ -220,6 +220,35 @@ This notification resolves the race condition where a requestor might attempt to
 
 Receivers that do not support tasks (and thus ignore task metadata in requests) will not send this notification, allowing requestors to fall back to waiting for the original request response.
 
+### Task Status Notification
+
+When a task's status changes, receivers **MAY** send a `notifications/tasks/status` notification to inform the requestor of the change.
+
+**Notification:**
+
+```json
+{
+  "jsonrpc": "2.0",
+  "method": "notifications/tasks/status",
+  "params": {
+    "status": "completed",
+    "_meta": {
+      "modelcontextprotocol.io/related-task": {
+        "taskId": "786512e2-9e0d-44bd-8f29-789f320fe840"
+      }
+    }
+  }
+}
+```
+
+The notification includes:
+- `status`: The new task status
+- `error` (optional): Error message if the status is `failed`
+
+The task ID is conveyed through the `modelcontextprotocol.io/related-task` metadata key.
+
+Requestors **MUST NOT** rely on receiving these notifications, as they are optional. Receivers are not required to send status notifications and may choose to only send them for certain status transitions. Requestors **SHOULD** continue to poll via `tasks/get` to ensure they receive status updates.
+
 ### Listing Tasks
 
 To retrieve a list of tasks, requestors send a `tasks/list` request. This operation supports pagination.

docs/specification/draft/schema.mdx

@@ -57,7 +57,6 @@ export interface NotificationParams {
   _meta?: { [key: string]: unknown };
 }
 
-
 /** @internal */
 export interface Notification {
   method: string;
@@ -546,7 +545,7 @@ export interface Implementation extends BaseMetadata, Icons {
  */
 export interface PingRequest extends JSONRPCRequest {
   method: "ping";
-  params?: RequestParams
+  params?: RequestParams;
 }
 
 /* Progress notifications */
@@ -1423,6 +1422,41 @@ export interface TaskCreatedNotification extends JSONRPCNotification {
   };
 }
 
+/**
+ * Parameters for a `notifications/tasks/status` notification.
+ *
+ * @category notifications/tasks/status
+ */
+export interface TaskStatusNotificationParams extends NotificationParams {
+  /**
+   * The new task status.
+   */
+  status: TaskStatus;
+
+  /**
+   * Error message if status is "failed".
+   */
+  error?: string;
+
+  /**
+   * The _meta field MUST include modelcontextprotocol.io/related-task with the taskId.
+   */
+  _meta?: {
+    "modelcontextprotocol.io/related-task"?: RelatedTaskMetadata;
+    [key: string]: unknown;
+  };
+}
+
+/**
+ * An optional notification from the receiver to the requestor, informing them that a task's status has changed. Receivers are not required to send these notifications.
+ *
+ * @category notifications/tasks/status
+ */
+export interface TaskStatusNotification extends JSONRPCNotification {
+  method: "notifications/tasks/status";
+  params: TaskStatusNotificationParams;
+}
+
 /* Logging */
 
 /**
@@ -2042,7 +2076,8 @@ export type ClientNotification =
   | ProgressNotification
   | InitializedNotification
   | RootsListChangedNotification
-  | TaskCreatedNotification;
+  | TaskCreatedNotification
+  | TaskStatusNotification;
 
 /** @internal */
 export type ClientResult =
@@ -2076,7 +2111,8 @@ export type ServerNotification =
   | ResourceListChangedNotification
   | ToolListChangedNotification
   | PromptListChangedNotification
-  | TaskCreatedNotification;
+  | TaskCreatedNotification
+  | TaskStatusNotification;
 
 /** @internal */
 export type ServerResult =