feat: skip a11y ancestor path on android

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- The mobile a11y snapshot no longer computes the ancestor-role `path` on Android, emitting an empty `path` for every node instead. Android `path` values were widget class names (e.g. `android.widget.FrameLayout`) that dominated the `describe-screen` payload with no targeting value (mobile targeting is by a11y `ref` or `testId`). iOS and browser behavior are unchanged. ([#44](https://github.com/MetaMask/client-mcp-core/pull/44))
+
 ## [0.8.0]
 
 ### Added

src/platform/mobile-platform-driver.test.ts

@@ -509,6 +509,42 @@ describe('MobilePlatformDriver', () => {
       expect(nodes[2].path).toStrictEqual(['Window']);
     });
 
+    it('emits an empty path for every node on android', async () => {
+      const backend = createMockBackend({
+        platform: 'android',
+        snapshot: vi.fn().mockResolvedValue({
+          platform: 'android',
+          hierarchy: [
+            makeElement({
+              type: 'android.widget.FrameLayout',
+              children: [
+                makeElement({
+                  type: 'android.widget.LinearLayout',
+                  children: [
+                    makeElement({ type: 'android.widget.Button', label: 'OK' }),
+                    makeElement({
+                      type: 'android.widget.Button',
+                      label: 'Cancel',
+                    }),
+                  ],
+                }),
+              ],
+            }),
+          ],
+          raw: '[]',
+          timestamp: Date.now(),
+        }),
+      });
+      const driver = new MobilePlatformDriver(backend);
+
+      const { nodes } = await driver.getAccessibilityTree();
+
+      expect(nodes).toHaveLength(4);
+      for (const node of nodes) {
+        expect(node.path).toStrictEqual([]);
+      }
+    });
+
     it('builds refMap with value fallback', async () => {
       const backend = createMockBackend({
         snapshot: vi.fn().mockResolvedValue({

src/platform/mobile-platform-driver.ts

@@ -193,7 +193,7 @@ export class MobilePlatformDriver implements IPlatformDriver {
     _rootSelector?: string,
   ): Promise<{ nodes: A11yNodeTrimmed[]; refMap: Map<string, string> }> {
     const snapshot = await this.#backend.snapshot();
-    return normalizeSnapshot(snapshot.hierarchy);
+    return normalizeSnapshot(snapshot.hierarchy, this.#backend.platform);
   }
 
   /**
@@ -685,21 +685,33 @@ function parseStableIdentifier(stableId: string): ElementQuery {
 /**
  * Normalizes a UIElement hierarchy into A11yNodeTrimmed nodes with sequential refs.
  *
+ * On Android the ancestor-role `path` is a chain of widget class names
+ * (e.g. `android.widget.FrameLayout`) that offers no targeting value — mobile
+ * targeting is by a11y `ref` or `testId` only — and dominates the payload
+ * returned to agents. So on Android we emit an empty `path` rather than
+ * accumulating the ancestry. iOS keeps the ancestor path (its parity is
+ * unvalidated), matching the browser driver's behavior.
+ *
  * @param hierarchy - The raw UIElement tree from a device snapshot.
+ * @param platform - The device platform; `'android'` skips path computation.
  * @returns Trimmed nodes and the ref-to-stable-identifier map.
  */
-function normalizeSnapshot(hierarchy: UIElement[]): {
+function normalizeSnapshot(
+  hierarchy: UIElement[],
+  platform: PlatformType,
+): {
   nodes: A11yNodeTrimmed[];
   refMap: Map<string, string>;
 } {
   const nodes: A11yNodeTrimmed[] = [];
   const refMap = new Map<string, string>();
   const stableIdCount = new Map<string, string[]>();
+  const skipPath = platform === 'android';
   let refCounter = 0;
 
   /**
    * @param elements - UIElement nodes to walk.
-   * @param path - Accumulated ancestor roles.
+   * @param path - Accumulated ancestor roles (always empty on Android).
    */
   function walk(elements: UIElement[], path: string[]): void {
     for (const el of elements) {
@@ -737,7 +749,7 @@ function normalizeSnapshot(hierarchy: UIElement[]): {
       }
 
       if (el.children?.length) {
-        walk(el.children, [...path, role]);
+        walk(el.children, skipPath ? path : [...path, role]);
       }
     }
   }