chore: update spec.types.2026-07-28.ts from upstream

Author: github-actions[bot]

packages/core-internal/src/types/spec.types.2026-07-28.ts

@@ -3,7 +3,7 @@
  *
  * Source: https://github.com/modelcontextprotocol/modelcontextprotocol
  * Pulled from: https://raw.githubusercontent.com/modelcontextprotocol/modelcontextprotocol/main/schema/draft/schema.ts
- * Last updated from commit: f68d864a813754e188c6df52dcc5772a12f96c63
+ * Last updated from commit: 9a4ff8af92ba00cbddbf94672dfade9279987e66
  *
  * DO NOT EDIT THIS FILE MANUALLY. Changes will be overwritten by automated updates.
  * To update this file, run: pnpm run fetch:spec-types 2026-07-28
@@ -1333,10 +1333,16 @@ export interface SubscriptionsAcknowledgedNotificationParams extends Notificatio
 }
 
 /**
- * Sent by the server as the first message on a
- * {@link SubscriptionsListenRequest | subscriptions/listen} stream to acknowledge
- * that the subscription has been established and to report which notification
- * types it agreed to honor.
+ * Sent by the server to acknowledge that a
+ * {@link SubscriptionsListenRequest | subscriptions/listen} subscription has been
+ * established and to report which notification types it agreed to honor.
+ *
+ * This notification MUST be the first message the server sends carrying the
+ * subscription's ID in `io.modelcontextprotocol/subscriptionId`. The server MUST
+ * NOT send any notification on the subscription before acknowledging it. On
+ * stdio, where every subscription shares one channel, this ordering is defined
+ * per subscription ID and not per channel: messages belonging to other
+ * subscriptions MAY be interleaved before it.
  *
  * @example Listen acknowledged
  * {@includeCode ./examples/SubscriptionsAcknowledgedNotification/listen-acknowledged.json}