chore: return loaderId in a11y snapshots (#14591)

packages/puppeteer-core/src/cdp/Accessibility.ts

@@ -8,6 +8,7 @@ import type {Protocol} from 'devtools-protocol';
 
 import type {ElementHandle} from '../api/ElementHandle.js';
 import type {Realm} from '../api/Realm.js';
+import type {CdpFrame} from '../cdp/Frame.js';
 import {debugError} from '../common/util.js';
 
 /**
@@ -88,12 +89,19 @@ export interface SerializedAXNode {
   children?: SerializedAXNode[];
 
   /**
-   * CDP-specifc ID to reference the DOM node.
+   * CDP-specific ID to reference the DOM node.
    *
    * @internal
    */
   backendNodeId?: number;
 
+  /**
+   * CDP-specific documentId.
+   *
+   * @internal
+   */
+  loaderId: string;
+
   /**
    * Get an ElementHandle for this AXNode if available.
    *
@@ -553,6 +561,9 @@ class AXNode {
         })) as ElementHandle<Element>;
       },
       backendNodeId: this.payload.backendDOMNodeId,
+      // LoaderId is an experimental mechanism to establish unique IDs across
+      // navigations.
+      loaderId: (this.#realm.environment as CdpFrame)._loaderId,
     };
 
     type UserStringProperty =

test/TestExpectations.json

@@ -230,6 +230,13 @@
     "expectations": ["SKIP"],
     "comment": "TODO: add a comment explaining why this expectation is required (include links to issues)"
   },
+  {
+    "testIdPattern": "[a11yLoaderId.spec] Accessibility loaderId should match loaderId for iframes",
+    "platforms": ["darwin", "linux", "win32"],
+    "parameters": ["webDriverBiDi"],
+    "expectations": ["SKIP"],
+    "comment": "not supported, CDP-specific test"
+  },
   {
     "testIdPattern": "[accessibility.spec] *",
     "platforms": ["darwin", "linux", "win32"],

test/src/cdp/a11yLoaderId.spec.ts

@@ -0,0 +1,66 @@
+/**
+ * @license
+ * Copyright 2026 Google Inc.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import expect from 'expect';
+import type {CdpFrame} from 'puppeteer-core/internal/cdp/Frame.js';
+
+import {getTestState, setupTestBrowserHooks} from '../mocha-utils.js';
+import {attachFrame} from '../utils.js';
+
+describe('Accessibility loaderId', function () {
+  setupTestBrowserHooks();
+
+  it('should match loaderId for iframes', async () => {
+    const {page, server} = await getTestState();
+    await page.goto(server.EMPTY_PAGE);
+    await attachFrame(page, 'frame1', server.EMPTY_PAGE);
+    const frame1 = page.frames()[1];
+    await frame1!.evaluate(() => {
+      const button = document.createElement('button');
+      button.innerText = 'value1';
+      document.body.appendChild(button);
+    });
+    const snapshot = await page.accessibility.snapshot({
+      interestingOnly: true,
+      includeIframes: true,
+    });
+
+    const mainLoaderId = (page.mainFrame() as CdpFrame)._loaderId;
+    const frame1LoaderId = (frame1 as CdpFrame)._loaderId;
+
+    expect(typeof mainLoaderId).toBe('string');
+    expect(mainLoaderId).toBeTruthy();
+    expect(typeof frame1LoaderId).toBe('string');
+    expect(frame1LoaderId).toBeTruthy();
+
+    expect(snapshot).toMatchObject({
+      role: 'RootWebArea',
+      name: '',
+      loaderId: mainLoaderId,
+      children: [
+        {
+          role: 'Iframe',
+          name: '',
+          loaderId: mainLoaderId,
+          children: [
+            {
+              role: 'RootWebArea',
+              name: '',
+              loaderId: frame1LoaderId,
+              children: [
+                {
+                  role: 'button',
+                  name: 'value1',
+                  loaderId: frame1LoaderId,
+                },
+              ],
+            },
+          ],
+        },
+      ],
+    });
+  });
+});