iosbox

Build iOS apps in Docker. Works wherever Docker runs.

iosbox provides a containerized environment for building iOS apps — no Mac, no Xcode installation, no external CI required. Point it at your Xcode.xip (downloaded directly from Apple) and your Flutter project, and get a .ipa out.

How it works

1. iosbox setup — extract the iOS SDK and Swift toolchain from a downloaded Xcode.xip into a Docker volume, download a prebuilt ld64.lld linker, and register the Swift SDK for cross-compilation.

2. iosbox dev — run the full build pipeline in the container:

   • Compile Dart sources and collect assets (flutter assemble)
   • Resolve Flutter.xcframework from the cache
   • Generate a SwiftPM Package.swift wrapping your Swift sources and iOS plugins
   • Compile with swift build --swift-sdk arm64-apple-ios
   • Assemble a .app bundle and package it into Runner.ipa

The output .ipa is unsigned. Sign and install it with MobAI, which handles code signing and OTA delivery out of the box.

Prerequisites

• Docker
• Xcode.xip — downloaded from developer.apple.com/download/all (Apple ID login required). Only needed once for the SDK setup step.

Swift, Flutter, and all build tooling are included in the image.

Docker images

Pre-built images are available on Docker Hub:

Tag	Flutter
mobaiapp/iosbox:flutter-3.38.5	3.38.5
mobaiapp/iosbox:flutter-3.41.0	3.41.0
mobaiapp/iosbox:flutter-3.41.6	3.41.6

Quick start

1. Download Xcode

Sign in at developer.apple.com/download with a free Apple ID and download Xcode 26.3 — either Apple_silicon or Universal variant works.

The download links require a browser session — direct curl won't work without auth cookies.

2. One-time SDK setup

Run this once to extract and register the iOS SDK into a named Docker volume:

docker run --rm \
  -v /path/to/Xcode_26.3_Apple_silicon.xip:/workspace/Xcode.xip:/workspace/Xcode.xip \
  -v iosbox-sdk:/root/.iosbox \
  mobaiapp/iosbox:flutter-3.41.0 \
  iosbox setup /workspace/Xcode.xip

The iosbox-sdk volume persists the extracted SDK — you won't need to repeat this step.

3. Build your Flutter app

docker run --rm \
  -v iosbox-sdk:/root/.iosbox \
  -v /path/to/your-flutter-app:/project \
  -v iosbox-swift-cache-myapp:/root/.cache/org.swift.swiftpm \
  -v iosbox-build-cache-myapp:/tmp/iosbox-native-build \
  mobaiapp/iosbox:flutter-3.41.0 \
  iosbox build /project

The cache volumes (iosbox-swift-cache-*, iosbox-build-cache-*) persist SwiftPM packages and native build artifacts between runs, significantly speeding up subsequent builds.

The .ipa is written to /path/to/your-flutter-app/build/iosbox/Runner.ipa.

Sign, install, and run it with ios-builder and MobAI.

Project support

Project type	Status
Flutter (iOS)	Supported
SwiftUI / native iOS	Planned
React Native	Planned

Architecture

cmd/iosbox/          CLI entrypoint (setup, dev)
internal/
  flutter/          Flutter build pipeline
    build.go        Orchestrates the 8-step build
    native.go       SwiftPM package generation + swift build invocation
    bundle.go       .app bundle assembly
    engine.go       Flutter.xcframework resolution
    native_assets.go  Dart native assets support
    macho.go        Mach-O binary utilities
  sdk/
    sdk.go          SDK path helpers + Swift SDK JSON types
    extract.go      Xcode.app → .sdk bundle extraction
    xip.go          Xcode.xip → Xcode.app extraction (XAR + pbzx + CPIO)
    toolset.go      ld64.lld download + swift sdk install
    shims.go        Shim directory paths
  project/
    detect.go       Project type detection
shims/
  flutter/          xcrun / lipo / codesign stubs for flutter assemble
  clang             Intercepts clang calls targeting arm64-apple-ios

Swift Package Manager

iosbox uses Swift Package Manager for native iOS plugin compilation. SwiftPM support in Flutter is still not enabled by default — the Docker image enables it via flutter config --enable-swift-package-manager. If your project uses CocoaPods-only plugins, they may need SwiftPM support added.

Limitations & Disclaimer

• Debug builds only. Release (AOT) builds are in progress.
• Xcode 26.3 or earlier required. Xcode 26.4+ ships SDK headers as stubs that require Apple's installer to reconstitute. This is not yet supported.
• Only physical devices are supported (arm64-apple-ios), no simulator.
• The .ipa is unsigned. Use MobAI for signing, installation, and debugging.
• You must supply your own Xcode.xip from Apple and comply with its license. This project is for research and educational use only, is not affiliated with Apple or Google, and is provided as-is without warranty.

License

MIT