diff --git a/.changeset/green-plums-wave.md b/.changeset/green-plums-wave.md
new file mode 100644
index 0000000000..c3c438abb8
--- /dev/null
+++ b/.changeset/green-plums-wave.md
@@ -0,0 +1,5 @@
+---
+"@lynx-js/react": patch
+---
+
+Avoid registering lifecycle refs for main-thread functions (MTF) that have not received an `execId` during `renderPage()` first-screen binding.
diff --git a/packages/react/worklet-runtime/__test__/observers.test.js b/packages/react/worklet-runtime/__test__/observers.test.js
new file mode 100644
index 0000000000..1bea337d47
--- /dev/null
+++ b/packages/react/worklet-runtime/__test__/observers.test.js
@@ -0,0 +1,53 @@
+// Copyright 2026 The Lynx Authors. All rights reserved.
+// Licensed under the Apache License Version 2.0 that can be found in the
+// LICENSE file in the root directory of this source tree.
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import { onWorkletCtxUpdate } from '../src/bindings/observers';
+import { initWorklet } from '../src/workletRuntime';
+
+beforeEach(() => {
+  globalThis.SystemInfo = {
+    lynxSdkVersion: '2.16',
+  };
+  initWorklet();
+});
+
+afterEach(() => {
+  delete globalThis.lynxWorkletImpl;
+});
+
+describe('MTFObservers', () => {
+  it('should not add a lifecycle ref when execId is missing for an MTF', () => {
+    const addRef = vi.fn();
+    globalThis.lynxWorkletImpl._jsFunctionLifecycleManager = {
+      addRef,
+    };
+
+    onWorkletCtxUpdate(
+      {
+        _wkltId: 'ctx1',
+      },
+      undefined,
+      false,
+      'element',
+    );
+
+    expect(addRef).not.toHaveBeenCalled();
+  });
+
+  it('should add a lifecycle ref when execId exists for an MTF', () => {
+    const addRef = vi.fn();
+    globalThis.lynxWorkletImpl._jsFunctionLifecycleManager = {
+      addRef,
+    };
+    const mtf = {
+      _wkltId: 'ctx1',
+      _execId: 8,
+    };
+
+    onWorkletCtxUpdate(mtf, undefined, false, 'element');
+
+    expect(addRef).toHaveBeenCalledWith(8, mtf);
+  });
+});
diff --git a/packages/react/worklet-runtime/src/bindings/observers.ts b/packages/react/worklet-runtime/src/bindings/observers.ts
index 5f59e2648b..7f39ea9f30 100644
--- a/packages/react/worklet-runtime/src/bindings/observers.ts
+++ b/packages/react/worklet-runtime/src/bindings/observers.ts
@@ -18,7 +18,9 @@ export function onWorkletCtxUpdate(
   isFirstScreen: boolean,
   element: ElementNode,
 ): void {
-  globalThis.lynxWorkletImpl?._jsFunctionLifecycleManager?.addRef(worklet._execId!, worklet);
+  if (worklet._execId !== undefined) {
+    globalThis.lynxWorkletImpl?._jsFunctionLifecycleManager?.addRef(worklet._execId, worklet);
+  }
   if (isFirstScreen && oldWorklet) {
     globalThis.lynxWorkletImpl?._hydrateCtx(worklet, oldWorklet);
   }