Resolving Xcode Sandbox File-Write-Data Errors

Problem Statement

When building React Native iOS projects (particularly Share extensions) in Xcode, you may encounter a sandbox permission error:

Sandbox: bash(72986) deny(1) file-write-data /Users/XXX/ios/Pods/resources-to-copy-XXXShareExtension.txt

This error indicates the Xcode build sandbox is preventing scripts from writing to required files. The issue manifests as a build failure despite repeated rebuild attempts, especially in projects with extensions.

Primary Solution: Disable User Script Sandboxing

The most reliable fix involves disabling the ENABLE_USER_SCRIPT_SANDBOXING setting in Xcode:

1. Open your .xcworkspace file in Xcode
2. Select your project in the left sidebar
3. Navigate to Build Settings › All › Combined
4. Search for ENABLE_USER_SCRIPT_SANDBOXING
5. Change the value to NO for:
   • Your main application target
   • Your Share Extension target (XXXShareExtension)

Important

Both targets must have this setting disabled. Failure to modify both is a common oversight.

After making these changes:

1. Clean your build: Product › Clean Build Folder (⌥⇧⌘K)
2. Delete DerivedData folder (located at ~/Library/Developer/Xcode/DerivedData)
3. Rebuild your project

Why This Works

The sandboxing feature restricts file system access during build phases. Disabling it allows essential copy scripts to:

1. Read resources from source directories
2. Write required files to the build folder
3. Access shared Pod resources between targets

Alternative Solution: Fix Gem Dependencies in CI Environments

If the error occurs in a CI/CD pipeline using Ruby-based tools, pin your xcodeproj gem version:

# Add to your Gemfile
gem 'xcodeproj', '< 1.26.0' # Versions >=1.26.0 may cause sandbox issues

Install dependencies with:

bundle install
bundle exec pod install

Framework Limitation

This Gemfile fix only applies to builds using:

• Fastlane
• CocoaPods dependency management
• Ruby-based build toolchains

Additional Troubleshooting Steps

If the issue persists:

1. Verify Podfile linkage for your extension target:

   target 'XXXShareExtension' do
     # Ensure copy resources script exists
     use_frameworks!
   end

2. Check runtime permissions in ios/XXXShareExtension/Info.plist:

   <key>NSDocumentsFolderUsageDescription</key>
   <string>Required to write resources</string>

3. Reset Xcode toolchain:

   sudo rm -rf ~/Library/Developer/Xcode/DerivedData
   sudo rm -rf ~/Library/Caches/CocoaPods
   pod deintegrate
   pod install --repo-update

Conclusion

The deny(1) file-write-data error occurs when Xcode's sandbox restricts build script operations. Disabling ENABLE_USER_SCRIPT_SANDBOXING for all targets resolves most cases, while gem version management addresses CI-specific pipeline failures. These solutions apply to:

Project Type	Compatibility
React Native	✅
Native iOS	✅
Ionic/Cordova	✅
Xcode 15+	✅
Share Extensions	✅