EAS Observe rejects 7.47 MiB Gradle source map although Expo CLI Hermes map fits 5 MiB

[pholoubek]

Build/Submit details page URL

Omitted from the public issue because the build belongs to a private project. I can provide the build URL and server request ID privately to Expo maintainers.

Summary

With uploadSourceMaps: true, an otherwise successful Android EAS Build cannot upload its source map to EAS Observe because the processed Gradle-generated map is 7,836,304 bytes and the server rejects maps at 5 MiB. A production expo export --platform android --source-maps external for the same JavaScript produces a Hermes-composed map that is 5,059,651 bytes after removing sourcesContent, which is below the 5 MiB limit.

Expected: EAS Build uploads an equivalent source map that fits the server limit, supports a compact/compressed representation, or provides a supported way to select/process the map before upload.

Actual: the Android app bundle finishes successfully, but source-map upload fails and EAS Observe errors cannot be symbolicated.

Managed or bare?

Managed / Continuous Native Generation. EAS runs npx expo prebuild --clean; the EAS job reports type: managed.

Environment

Local:
  OS: Linux / WSL2
  Node: 20.19.5
  npm: 10.8.2
  eas-cli: 23.2.0

Packages:
  expo: 57.0.21
  expo-observe: 57.0.20
  expo-router: 57.0.20
  expo-updates: 57.0.21
  react: 19.2.3
  react-native: 0.86.3
  react-native-reanimated: 4.5.1
  react-native-worklets: 0.10.1

EAS Build:
  Platform: Android
  Profile: preview
  Build type: app-bundle
  Node: 22.13.0
  Image: ubuntu-26.04-jdk-17-ndk-r27b-sdk-57
  NODE_ENV: production
  BABEL_ENV: production

Expo Doctor:
  21/21 checks passed. No issues detected.

Error output

The Gradle build first creates the packager map:

Writing sourcemap output to: <project>/android/app/build/intermediates/sourcemaps/react/release/index.android.bundle.packager.map

During UPLOAD_BUILD_ARTIFACTS, EAS selects the generated map:

Uploading source map: <project>/android/app/build/generated/sourcemaps/react/release/index.android.bundle.map
Source map upload failed
size: 7836304
Unexpected response from server (400):
{"errors":[{"code":"VALIDATION_ERROR","type":"USER","message":"Source map size must be less than 5 MiB.","isTransient":false}]}

The build itself finishes successfully; only source-map upload is reported as a warning.

Reproducible demo or steps to reproduce from a blank project

The exact EAS build URL and request ID can be shared privately with Expo maintainers.

1. Use an Expo SDK 57 managed/CNG app with a sufficiently large native JavaScript graph. The affected build bundled 4,499 modules. The largest dependency is stream-chat-expo@9.3.0, but the failure occurs in EAS source-map upload rather than Stream runtime code.

2. Install expo-observe@57.0.20.

3. Configure an EAS Android profile with production transforms and source-map upload:

   {
     "build": {
       "preview": {
         "distribution": "internal",
         "uploadSourceMaps": true,
         "env": {
           "NODE_ENV": "production",
           "BABEL_ENV": "production"
         },
         "android": {
           "buildType": "app-bundle"
         }
       }
     }
   }

4. Run eas build --platform android --profile preview --clear-cache.

5. Observe the 400 validation error during UPLOAD_BUILD_ARTIFACTS when the stripped map is larger than 5 MiB.

For comparison, generate the Expo CLI production export locally:

NODE_ENV=production BABEL_ENV=production npx expo export \
  --platform android \
  --source-maps external \
  --clear

Parsing the resulting Android Hermes map, deleting only the top-level sourcesContent property, and serializing it with JSON.stringify gives:

Raw Hermes map: 21,277,447 bytes
Without sourcesContent: 5,059,651 bytes (4.83 MiB)
5 MiB server limit: 5,242,880 bytes

The corresponding EAS Gradle-generated upload payload is 7,836,304 bytes (7.47 MiB). Could EAS use the smaller Expo CLI-equivalent Hermes map, further compact the Gradle map, accept gzip transfer/storage, or expose a supported preprocessing/upload path?