@rnx-kit/react-native-host: build fails with React Native 0.87 nightly

[kraenhansen]

Description

@rnx-kit/react-native-host@0.5.17 fails to compile against React Native 0.87 nightly (0.87.0-nightly-20260529-88857d22f).

Error

RNXBridgelessHeaders.h:74:33: error: only virtual member functions can be marked 'override'
    bool enableFabricRenderer() override
RNXBridgelessHeaders.h:78:28: error: only virtual member functions can be marked 'override'
    bool useTurboModules() override

Root Cause

The enableFabricRenderer() and useTurboModules() methods were removed from ReactNativeFeatureFlagsDefaults in React Native 0.87 (Fabric and TurboModules are now always enabled). The RNXBridgelessFeatureFlags subclass in RNXBridgelessHeaders.h still tries to override them, which fails because the base class methods no longer exist.

Workaround

Commenting out the two method overrides resolves the build error:

-    bool enableFabricRenderer() override
-    {
-        return true;
-    }
-    bool useTurboModules() override
-    {
-        return true;
-    }
+    // enableFabricRenderer and useTurboModules removed in RN 0.87 (always-on)

Environment

• @rnx-kit/react-native-host: 0.5.17
• react-native: 0.87.0-nightly-20260529-88857d22f
• react-native-test-app: 5.1.9
• Xcode: 26 beta
• Platform: iOS Simulator

[tido64]

Thanks for reporting! Our nightly builds don't run over the weekend so we're only seeing this now: https://github.com/microsoft/react-native-test-app/actions/runs/26737077356/job/78792410909

[tido64]

Can you try the fix in #4183 and let me know how it goes?