diff --git a/packages/core/src/core/media/proxy.ts b/packages/core/src/core/media/proxy.ts
index f932ef77..042f2279 100644
--- a/packages/core/src/core/media/proxy.ts
+++ b/packages/core/src/core/media/proxy.ts
@@ -21,10 +21,7 @@ export interface MediaProxy {
  *
  * The `get`, `set`, and `call` methods can be overridden to provide catch-all custom behavior.
  */
-export const ProxyMixin = <T extends EventTarget>(
-  PrimaryClass: AnyConstructor<T>,
-  ...AdditionalClasses: AnyConstructor<EventTarget>[]
-) => {
+export const ProxyMixin = <T extends EventTarget>(BaseClass: AnyConstructor<T>) => {
   class MediaProxyImpl extends EventTarget {
     #target: EventTarget | null = null;
     #types = new Set<string>();
@@ -81,8 +78,12 @@ export const ProxyMixin = <T extends EventTarget>(
     };
   }
 
-  for (const Class of [PrimaryClass, ...AdditionalClasses]) {
-    defineClassPropHooks(MediaProxyImpl, Class.prototype);
+  for (
+    let proto = BaseClass.prototype;
+    proto && !Object.prototype.isPrototypeOf.call(proto, MediaProxyImpl.prototype);
+    proto = Object.getPrototypeOf(proto)
+  ) {
+    defineClassPropHooks(MediaProxyImpl, proto);
   }
 
   return MediaProxyImpl as unknown as Constructor<T & MediaProxy>;
diff --git a/packages/core/src/core/media/tests/proxy.test.ts b/packages/core/src/core/media/tests/proxy.test.ts
index 2236a57c..16cdd9b2 100644
--- a/packages/core/src/core/media/tests/proxy.test.ts
+++ b/packages/core/src/core/media/tests/proxy.test.ts
@@ -155,6 +155,46 @@ describe('ProxyMixin', () => {
     });
   });
 
+  describe('prototype chain walking', () => {
+    it('proxies methods inherited from ancestor prototypes', () => {
+      class Grandparent extends EventTarget {
+        inherited() {
+          return 'grandparent';
+        }
+      }
+
+      class Parent extends Grandparent {
+        direct() {
+          return 'parent';
+        }
+      }
+
+      const ParentProxy = ProxyMixin(Parent);
+      const proxy = new ParentProxy();
+      const target = new Parent();
+      proxy.attach(target);
+
+      expect(proxy.direct()).toBe('parent');
+      expect(proxy.inherited()).toBe('grandparent');
+    });
+
+    it('stops before prototypes the proxy already extends', () => {
+      class Child extends EventTarget {
+        custom() {
+          return 'custom';
+        }
+      }
+
+      const ChildProxy = ProxyMixin(Child);
+
+      // addEventListener is defined by the proxy itself — the walk
+      // should not overwrite it with a forwarding hook.
+      expect(Object.getOwnPropertyDescriptor(ChildProxy.prototype, 'addEventListener')?.value).toBe(
+        ChildProxy.prototype.addEventListener
+      );
+    });
+  });
+
   describe('EventListenerObject support', () => {
     it('invokes handleEvent on an object listener', () => {
       const { proxy, target } = setup();
diff --git a/packages/core/src/dom/media/custom-media-element/index.ts b/packages/core/src/dom/media/custom-media-element/index.ts
index 60b75949..7a73b080 100644
--- a/packages/core/src/dom/media/custom-media-element/index.ts
+++ b/packages/core/src/dom/media/custom-media-element/index.ts
@@ -372,7 +372,6 @@ export function CustomMediaMixin<T extends Constructor<HTMLElement>>(
           this.#childObserver?.observe(el, { attributes: true });
         }
         this.target?.append(clone);
-        this.#enableDefaultTrack(clone as HTMLTrackElement);
       });
 
       removeNativeChildren.forEach((clone, el) => {
@@ -388,25 +387,11 @@ export function CustomMediaMixin<T extends Constructor<HTMLElement>>(
           const clone = this.#childMap.get(target as MediaChild);
           if (clone && attributeName) {
             clone.setAttribute(attributeName, (target as MediaChild).getAttribute(attributeName) ?? '');
-            this.#enableDefaultTrack(clone as HTMLTrackElement);
           }
         }
       }
     }
 
-    #enableDefaultTrack(trackEl: HTMLTrackElement): void {
-      // Enable default text tracks for chapters or metadata
-      if (
-        trackEl &&
-        trackEl.localName === 'track' &&
-        trackEl.default &&
-        (trackEl.kind === 'chapters' || trackEl.kind === 'metadata') &&
-        trackEl.track.mode === 'disabled'
-      ) {
-        trackEl.track.mode = 'hidden';
-      }
-    }
-
     #upgradeProperty(this: typeof nativeElTest, prop: keyof typeof nativeElTest) {
       // Sets properties that are set before the custom element is upgraded.
       // https://web.dev/custom-elements-best-practices/#make-properties-lazy
diff --git a/packages/core/src/dom/media/proxy.ts b/packages/core/src/dom/media/proxy.ts
index d8f34639..08e7e79d 100644
--- a/packages/core/src/dom/media/proxy.ts
+++ b/packages/core/src/dom/media/proxy.ts
@@ -1,7 +1,3 @@
 import { ProxyMixin } from '../../core/media/proxy';
 
-export const VideoProxy = ProxyMixin(
-  globalThis.HTMLVideoElement ?? class {},
-  globalThis.HTMLMediaElement ?? class {},
-  globalThis.EventTarget ?? class {}
-);
+export const VideoProxy = ProxyMixin(globalThis.HTMLVideoElement ?? class {});
diff --git a/packages/core/src/dom/store/features/text-track.ts b/packages/core/src/dom/store/features/text-track.ts
index 1a0a5312..4b7d7353 100644
--- a/packages/core/src/dom/store/features/text-track.ts
+++ b/packages/core/src/dom/store/features/text-track.ts
@@ -60,6 +60,11 @@ export const textTrackFeature = definePlayerFeature({
         }
       }
 
+      // Browsers don't auto-load cues for metadata/chapters tracks even with
+      // the `default` attribute — mode stays 'disabled' until explicitly set.
+      if (chaptersTrack && chaptersTrack.mode === 'disabled') chaptersTrack.mode = 'hidden';
+      if (thumbnailTrack && thumbnailTrack.mode === 'disabled') thumbnailTrack.mode = 'hidden';
+
       // VTTCue extends TextTrackCue with `text` — cast via `unknown` since
       // the CueList is typed as TextTrackCue which doesn't expose `text`.
       const chaptersCues: MediaTextCue[] = chaptersTrack?.cues
diff --git a/packages/react/src/ui/thumbnail/thumbnail.tsx b/packages/react/src/ui/thumbnail/thumbnail.tsx
index 983967a5..71bb9e64 100644
--- a/packages/react/src/ui/thumbnail/thumbnail.tsx
+++ b/packages/react/src/ui/thumbnail/thumbnail.tsx
@@ -55,8 +55,9 @@ export const Thumbnail = forwardRef<HTMLDivElement, ThumbnailProps>(function Thu
   // Resolve thumbnails: external prop takes priority over auto <track> path.
   const thumbnails = useMemo(() => {
     if (externalThumbnails && externalThumbnails.length > 0) return externalThumbnails;
-    if (!textTrack?.thumbnailCues.length) return [];
-    return mapCuesToThumbnails(textTrack.thumbnailCues, textTrack.thumbnailTrackSrc ?? undefined);
+    return textTrack && textTrack.thumbnailCues.length > 0
+      ? mapCuesToThumbnails(textTrack.thumbnailCues, textTrack.thumbnailTrackSrc ?? undefined)
+      : [];
   }, [externalThumbnails, textTrack]);
 
   const thumbnail = useMemo(() => core.findActiveThumbnail(thumbnails, time), [core, thumbnails, time]);