expo-prebuild

name	expo-prebuild
description	Managed-to-bare transition with Expo prebuild, the ios/android directories, .easignore, native-upgrade discipline, and custom-mod application order. Triggers on expo prebuild, prebuild, managed to bare, bare workflow, native upgrade, ios android directory, easignore, prebuild cache, eject, sync native, native code generation.
license	MIT
compatibility	Works with Claude Code
allowed-tools	Read Write Edit Bash Grep
metadata	{"author":"badi","homepage":"https://github.com/fatihkan/badi-skills/tree/main/skills/expo-prebuild","badi-version":">=1.27.0","category":"expo","scope":"advisory"}

expo-prebuild

A guide to the managed → bare transition and continuous native sync with npx expo prebuild. Managing the ios/ and android/ directories, .easignore, the native-upgrade flow, and custom-mod application order. Plugin writing lives in expo-config-plugin.

What It Does

• Generates the native projects with the prebuild command
• Continuous native generation (CNG) vs persisted native decision
• EAS build cleanup with .easignore
• Native upgrade flow (Expo SDK + dependencies)
• Prebuild cache and --clean flag usage
• Custom mod compose order

Prebuild Commands

# Basic
npx expo prebuild

# Single platform
npx expo prebuild --platform ios
npx expo prebuild --platform android

# Clean start (delete and regenerate the native directories)
npx expo prebuild --clean

# Specific template
npx expo prebuild --template <github-url-or-tarball>

# Skip dependency install
npx expo prebuild --no-install

Two Strategies

A) Continuous Native Generation (CNG) — Recommended

• Don't commit the ios/ and android/ directories
• prebuild runs before every build (EAS does it automatically)
• Native config is fully generated from app.config.ts + plugins
• Advantage: easy SDK upgrades, no conflicts
• Limit: very custom native changes = you must write a config plugin

B) Persisted Native (the old "bare")

• ios/ and android/ are committed
• Don't run prebuild — go straight to Xcode/Android Studio
• Advantage: full native control
• Limit: manual SDK upgrades, expect conflicts

.gitignore (for CNG)

/ios
/android

.easignore (speeds up the EAS build)

/ios
/android
.expo/
node_modules/
*.test.ts
__tests__/
docs/
apps/web/
packages/web-only/

Every file in .gitignore is fine for .easignore too. Without .easignore, EAS uses .gitignore.

Native Upgrade Flow

# 1. Upgrade the Expo SDK
npx expo install expo@latest
npx expo install --check          # detect incompatible packages
npx expo install --fix            # auto-pull compatible versions

# 2. Prebuild again (always, if using CNG)
npx expo prebuild --clean

# 3. Pod install (iOS)
cd ios && pod install && cd ..

# 4. Test
npx expo run:ios
npx expo run:android

Persisted Native Mode: Manual Patch Flow

If you're not using CNG:

# 1. See which native changes the new Expo SDK brought
npx expo prebuild --clean --platform ios
# Review the ios/ changes with git diff

# 2. Apply the patches by hand to your own ios/ android/ directories
# 3. Commit ios/ android/

Higher chance of errors. Moving to CNG is usually less painful.

Custom Mod Application Order

During prebuild the mods run in order:

1. The order in the app.config.ts plugins array is critical
2. withInfoPlist mods are applied first
3. Then the withDangerousMod mods
4. mod.finalize last

If there's a clash: one plugin adds a key to Info.plist, the next must not delete it.

// app.config.ts
export default {
  expo: {
    plugins: [
      "./plugins/withBaseConfig",      // 1. Base
      "./plugins/withFeatureFlags",    // 2. Add the flags
      "./plugins/withFinalize",        // 3. Final cleanup
    ],
  },
};

Prebuild Cache

# Clear the cache (if there's a problem)
rm -rf node_modules .expo ios android
npm install
npx expo prebuild --clean
cd ios && pod install && cd ..

iOS Pods cache:

cd ios
pod cache clean --all
pod deintegrate
pod install

Gradle cache:

cd android
./gradlew --stop
./gradlew clean
rm -rf ~/.gradle/caches/build-cache-*

Verification

# Native file check
ls -la ios/MyApp.xcworkspace
ls -la android/app/build.gradle

# Info.plist plugin effect
plutil -p ios/MyApp/Info.plist | grep MyCustomKey

# AndroidManifest plugin effect
grep "API_KEY" android/app/src/main/AndroidManifest.xml

# Run
npx expo run:ios
npx expo run:android

Best Practices

• Choose CNG mode (don't commit ios/android) — SDK upgrades get easier
• .easignore reduces the EAS upload size
• --clean use often — it fixes stale-residue problems
• Write the plugin order explicitly (add comments)
• Pod install after every prebuild (if an iOS native dep changes)
• Run expo-doctor before and after prebuild

Common Failure Patterns

• ios/ committed but a plugin exists too → manual patch + plugin clash
• pod install skipped → iOS build "module not found"
• Gradle cache residue → "duplicate class"
• A plugin change without --clean → old state remains
• Native dependency missing from package.json but present in ios/Podfile → lost in CI
• expo-modules-autolinking version mismatch → autolink fails

Hard Refusal

• Committing another developer's native code without permission
• Prebuilding with a forged bundle ID and trying to submit
• Native modification that violates App Store rules (private API usage)

Output Format

1. CNG vs persisted decision (rationale)
2. .easignore example
3. Prebuild command (copy-paste)
4. Native upgrade order
5. Verification commands
6. Next step: expo-config-plugin (custom mod) or expo-eas-build