Add ui/close-resource request for UI to initiate termination

Author: fredericbarthelet

src/app-bridge.ts

@@ -68,6 +68,8 @@ import {
   McpUiResourceTeardownRequest,
   McpUiResourceTeardownResult,
   McpUiResourceTeardownResultSchema,
+  McpUiCloseResourceNotification,
+  McpUiCloseResourceNotificationSchema,
   McpUiSandboxProxyReadyNotification,
   McpUiSandboxProxyReadyNotificationSchema,
   McpUiSizeChangedNotificationSchema,
@@ -549,6 +551,39 @@ export class AppBridge extends Protocol<
     );
   }
 
+  /**
+   * Register a handler for app-initiated close notifications from the Guest UI.
+   *
+   * The Guest UI sends `ui/notifications/close-resource` when it wants to close itself.
+   * This is the app-initiated counterpart to the host-initiated `ui/resource-teardown`.
+   * Since the app initiates this, it has already performed any necessary cleanup
+   * before sending the notification.
+   *
+   * This is a fire-and-forget notification - the host should immediately unmount
+   * the app iframe upon receiving this notification.
+   *
+   * @param callback - Handler that receives close params
+   *   - params - Empty object (reserved for future use)
+   *
+   * @example
+   * ```typescript
+   * bridge.oncloseresource = (params) => {
+   *   console.log("App requested close");
+   *   // Unmount the iframe
+   *   iframe.remove();
+   * };
+   * ```
+   *
+   * @see {@link McpUiCloseResourceNotification} for the notification type
+   */
+  set oncloseresource(
+    callback: (params: McpUiCloseResourceNotification["params"]) => void,
+  ) {
+    this.setNotificationHandler(McpUiCloseResourceNotificationSchema, (n) =>
+      callback(n.params),
+    );
+  }
+
   /**
    * Register a handler for display mode change requests from the Guest UI.
    *

src/app.ts

@@ -34,6 +34,7 @@ import {
   McpUiResourceTeardownRequest,
   McpUiResourceTeardownRequestSchema,
   McpUiResourceTeardownResult,
+  McpUiCloseResourceNotification,
   McpUiSizeChangedNotification,
   McpUiToolCancelledNotification,
   McpUiToolCancelledNotificationSchema,
@@ -848,6 +849,43 @@ export class App extends Protocol<AppRequest, AppNotification, AppResult> {
   /** @deprecated Use {@link openLink} instead */
   sendOpenLink: App["openLink"] = this.openLink;
 
+  /**
+   * Signal the host to close this app.
+   *
+   * Apps call this method to initiate their own termination. The host will
+   * close/unmount the app iframe upon receiving this notification. Since the app
+   * is initiating the close, it should perform any necessary cleanup (save state,
+   * close connections, etc.) before calling this method.
+   *
+   * This is a fire-and-forget notification - no response is expected since the
+   * host will immediately unmount the app upon receiving this notification.
+   *
+   * Unlike host-initiated teardown (`ui/resource-teardown`), the app has already
+   * done its cleanup when it calls this method, so no teardown request is
+   * sent back to the app.
+   *
+   * @param params - Empty params object (reserved for future use)
+   * @returns Promise that resolves when the notification is sent
+   *
+   * @example App-initiated close after user action
+   * ```typescript
+   * // User clicks "Done" button in the app
+   * async function handleDoneClick() {
+   *   await saveState();
+   *   app.closeResource();
+   *   // App will be unmounted by host
+   * }
+   * ```
+   *
+   * @see {@link McpUiCloseResourceNotification} for notification structure
+   */
+  closeResource(params: McpUiCloseResourceNotification["params"] = {}) {
+    return this.notification(<McpUiCloseResourceNotification>{
+      method: "ui/notifications/close-resource",
+      params,
+    });
+  }
+
   /**
    * Request a change to the display mode.
    *

src/generated/schema.json

@@ -407,6 +407,19 @@ export interface McpUiResourceTeardownResult {
   [key: string]: unknown;
 }
 
+/**
+ * @description Notification for app-initiated termination (Guest UI -> Host).
+ * Apps send this to signal the host to close/unmount them.
+ * Since the app initiates this, it has already performed any necessary cleanup.
+ * This is fire-and-forget - no response is expected since the host will
+ * immediately unmount the app upon receiving this notification.
+ * @see {@link app.App.closeResource} for the app method that sends this
+ */
+export interface McpUiCloseResourceNotification {
+  method: "ui/notifications/close-resource";
+  params: {};
+}
+
 /**
  * @description Capabilities supported by the host application.
  * @see {@link McpUiInitializeResult} for the initialization result that includes these capabilities

src/generated/schema.test.ts

@@ -33,6 +33,7 @@ export {
   type McpUiHostContextChangedNotification,
   type McpUiResourceTeardownRequest,
   type McpUiResourceTeardownResult,
+  type McpUiCloseResourceNotification,
   type McpUiHostCapabilities,
   type McpUiAppCapabilities,
   type McpUiInitializeRequest,
@@ -62,6 +63,7 @@ import type {
   McpUiInitializedNotification,
   McpUiSizeChangedNotification,
   McpUiSandboxProxyReadyNotification,
+  McpUiCloseResourceNotification,
   McpUiInitializeResult,
   McpUiOpenLinkResult,
   McpUiMessageResult,
@@ -90,6 +92,7 @@ export {
   McpUiHostContextChangedNotificationSchema,
   McpUiResourceTeardownRequestSchema,
   McpUiResourceTeardownResultSchema,
+  McpUiCloseResourceNotificationSchema,
   McpUiHostCapabilitiesSchema,
   McpUiAppCapabilitiesSchema,
   McpUiInitializeRequestSchema,
@@ -157,7 +160,7 @@ export type AppRequest =
  * - Sandbox resource ready
  *
  * App to host:
- * - Initialized, size-changed, sandbox-proxy-ready
+ * - Initialized, size-changed, sandbox-proxy-ready, close-resource
  * - Logging messages
  */
 export type AppNotification =
@@ -175,6 +178,7 @@ export type AppNotification =
   | McpUiInitializedNotification
   | McpUiSizeChangedNotification
   | McpUiSandboxProxyReadyNotification
+  | McpUiCloseResourceNotification
   | LoggingMessageNotification;
 
 /**