fix: correct onMessage payload extraction and increase bridgeTimeout for CI

- SandboxReactNativeView wrapper already unwraps e.nativeEvent.data before
  calling onMessage, so msg IS the data directly (not msg.data). iOS sends
  an object, Android sends a JSON string — handle both with typeof check.
- Switch beforeAll to waitFor/queryByTestId to avoid findByTestId 3-arg API
- Use a sibling hidden View for sandbox-ready marker instead of passing
  testID directly to SandboxReactNativeView: changing testID on the native
  view while the sandbox is running causes the iOS sandbox to restart,
  leading to a native crash 39s into test execution.
- Increase bridgeTimeout from default 60s to 120s so iOS CI simulator has
  enough time to install and boot the app after a long Xcode build

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: CAMOBAP

apps/fs-experiment/App.tsx

@@ -114,8 +114,10 @@ function App(): React.JSX.Element {
             </Pressable>
           </View>
 
+          {sandboxReady && (
+            <View testID="sandbox-ready" style={styles.readyMarker} />
+          )}
           <SandboxReactNativeView
-            testID={sandboxReady ? 'sandbox-ready' : undefined}
             style={styles.sandboxView}
             origin="sandbox.fs-experiment.demo"
             componentName="SandboxApp"
@@ -125,7 +127,8 @@ function App(): React.JSX.Element {
               useSubstitution ? SANDBOXED_SUBSTITUTIONS : undefined
             }
             onMessage={msg => {
-              if (msg.cmd === 'ready') setSandboxReady(true)
+              const payload = typeof msg === 'string' ? JSON.parse(msg) : msg
+              if (payload?.cmd === 'ready') setSandboxReady(true)
               console.log('Host received from sandbox:', msg)
             }}
             onError={err =>
@@ -142,6 +145,10 @@ const styles = StyleSheet.create({
   root: {
     flex: 1,
   },
+  readyMarker: {
+    width: 0,
+    height: 0,
+  },
   section: {
     borderBottomWidth: StyleSheet.hairlineWidth,
   },

apps/fs-experiment/__tests__/sandbox-isolation.harness.tsx

@@ -8,6 +8,7 @@ import {
   expect,
   it,
   render,
+  waitFor,
 } from 'react-native-harness'
 
 import App from '../App'
@@ -86,9 +87,14 @@ describe('Substitution OFF', () => {
   beforeAll(async () => {
     blockCleanup = true
     await render(<App />, {timeout: RENDER_TIMEOUT})
-    await screen.findByTestId('sandbox-ready', {
-      timeout: SANDBOX_READY_TIMEOUT,
-    })
+    await waitFor(
+      () => {
+        if (!screen.queryByTestId('sandbox-ready')) {
+          throw new Error('Sandbox not ready')
+        }
+      },
+      {timeout: SANDBOX_READY_TIMEOUT}
+    )
   }, SANDBOX_READY_TIMEOUT + RENDER_TIMEOUT)
 
   if (isIOS) {

apps/fs-experiment/rn-harness.config.mjs

@@ -33,6 +33,7 @@ const config = {
   forwardClientLogs: true,
   resetEnvironmentBetweenTestFiles: true,
   disableViewFlattening: true,
+  bridgeTimeout: 120_000,
 }
 
 export default config