Summary

This PR creates a focused reproduction for the Android harness runtime failure seen after upgrading the playground app to react-native@0.86.0-nightly-20260409-b1d12f535.

It also updates the matching @react-native/* toolchain packages to the same nightly version and keeps the runtime overlay buildable on RN 0.85+ so the repro stays isolated to the Metro module-loading path.

Context from investigation: this now looks specific to the RN nightly/Hermes nightly path. A clean react-native@0.85.0 install was reported to work, while this nightly still fails after reinstalling and rebuilding from a clean Android build.

What changed

• upgrade react-native in apps/playground to 0.86.0-nightly-20260409-b1d12f535
• upgrade @react-native/babel-preset, @react-native/eslint-config, @react-native/jest-preset, @react-native/metro-config, and @react-native/typescript-config to the same nightly version
• switch the runtime overlay to StyleSheet.absoluteFill so the runtime package still builds against RN 0.85+

Reproduction

Cleaned and rebuilt before running the Android smoke test:

pnpm install --force
pnpm nx reset
pnpm nx run-many -t build --projects="packages/*"
cd apps/playground/android && ./gradlew clean
cd ../../..
pnpm nx run @react-native-harness/playground:build-android --tasks=assembleDebug
cd apps/playground
HARNESS_PROJECT_ROOT="$PWD" HARNESS_RUNNER=android HARNESS_APP_PATH=android/app/build/outputs/apk/debug/app-debug.apk HARNESS_DEBUG=true pnpm exec react-native-harness --harnessRunner android --runTestsByPath src/__tests__/smoke.harness.ts

I also reran locally with the harness Metro cache disabled and still saw the same failure. The local-only runner config was temporarily pointed at the already booted Pixel_7_Pro_API_33 emulator, then reverted before pushing.

Observed failure

2026-04-10T06:40:04.895Z [harness][plugin:playground-logging] metro.bundleFailed runId=21ac9405-7353-4b63-8f24-fd5deff1a89a target=setupFile file=src/setupFile.ts error=Parsing source code unsupported: __d(function (global, _$$_REQUIR

FAIL src/__tests__/smoke.harness.ts
  ● Test suite failed to run

    SyntaxError: Parsing source code unsupported: __d(function (global, _$$_REQUIR

      at evaluateModule (http:/localhost:8082/index.bundle/&platform=android&dev=true&lazy=true&minify=false&app=com.harnessplayground&modulesOnly=false&runModule=true&excludeSource=true&sourcePaths=url-server:109513:9)
      at anonymous (http:/localhost:8082/index.bundle/&platform=android&dev=true&lazy=true&minify=false&app=com.harnessplayground&modulesOnly=false&runModule=true&excludeSource=true&sourcePaths=url-server:109677:25)
      at asyncGeneratorStep (http:/localhost:8082/index.bundle/&platform=android&dev=true&lazy=true&minify=false&app=com.harnessplayground&modulesOnly=false&runModule=true&excludeSource=true&sourcePaths=url-server:24779:19)
      at _next (http:/localhost:8082/index.bundle/&platform=android&dev=true&lazy=true&minify=false&app=com.harnessplayground&modulesOnly=false&runModule=true&excludeSource=true&sourcePaths=url-server:24793:29)
      at tryCallOne (address at InternalBytecode.js:1:1274)
      at anonymous (address at InternalBytecode.js:1:4865)

The failure happens at runtime when the harness asks Metro to load the setup/test module, not during the Android build.

Validation

• pnpm install --force
• pnpm nx reset
• pnpm nx run-many -t build --projects="packages/*"
• cd apps/playground/android && ./gradlew clean
• pnpm nx run @react-native-harness/playground:build-android --tasks=assembleDebug
• Android smoke harness run fails with the parser error above on 0.86.0-nightly-20260409-b1d12f535