kosei

Compiles, packages, and signs Android APKs directly on Android devices via Termux. No host machine, Android Studio, or desktop SDK installation required.

Build Pipeline

aapt2 compile     ->  compile res/ into .flat files
aapt2 link        ->  link .flat + AndroidManifest.xml -> .apk + R.java
ecj.jar (3.27.0)  ->  compile .java + R.java -> .class files (Java 16)
d8.dex            ->  desugar and convert .class -> classes.dex
zipfile           ->  inject classes.dex into the .apk
apksigner.dex     ->  sign the .apk with debug.pk8 and debug.x509.pem

Requirements

• Python >= 3.7
• Termux with aapt2 in $PATH
• Runtime toolchain in ~/.kosei/toolchain/ (installed via kosei setup)

Installation

Create a virtual environment and install in editable mode using uv:

uv venv
uv pip install -e .
kosei setup

Usage

Create a project with default package (com.example.hello):

kosei new Hello

Create a project with custom package and directory:

kosei new Hello -p com.mycompany.hello -d ./projects

Build project in current directory:

kosei build

Build project in specified directory:

kosei build ./projects/Hello

Clean build artifacts:

kosei clean ./projects/Hello

Download or repair runtime toolchain:

kosei setup

Force re-download complete toolchain:

kosei setup -f

Alternative Python module execution:

python -m kosei setup
python -m kosei new Hello
python -m kosei build

Build Outputs:

• build/[AppName].apk — Unsigned intermediate package inside the project build directory
• [AppName].apk — v1/v2/v3 signed APK ready for installation

Toolchain Binaries

All runtime binaries execute natively on Android's dalvikvm engine and are managed via kosei setup from kosei-toolchain.

File	Description	Purpose
android.jar	Android framework resource stubs	Passed to aapt2 link -I to resolve @android: attribute references and generate R.java
android.classes.jar	Android framework class definitions	Passed to ecj.jar via -cp so the Java compiler resolves android.* imports
ecj.jar	Eclipse Java Compiler 3.27.0 (patched for Dalvik)	Invoked via dalvikvm -cp ecj.jar org.eclipse.jdt.internal.compiler.batch.Main to compile Java source into .class files (up to Java 16)
d8.dex	Google D8 Dexer packaged as .dex	Invoked via dalvikvm -cp d8.dex com.android.tools.r8.D8 to desugar and convert .class bytecode into classes.dex
apksigner.dex	Android APK Signer tool packaged as .dex	Invoked via dalvikvm -cp apksigner.dex com.android.apksigner.ApkSignerTool to apply v1, v2, and v3 signatures
debug.pk8	PKCS8 private key for debug signing	Provided to apksigner via --key to sign debug builds
debug.x509.pem	X.509 certificate for debug signing	Provided to apksigner via --cert alongside debug.pk8

Technical Roadmap

• Native ART Engine Execution: Execute compilation toolchain (ecj, d8, apksigner) natively on Dalvik VM without host JDK dependencies.
• Java 16 & Google D8 Support: Modernized compilation pipeline with ECJ 3.27.0 and Google D8 dexer replacing legacy dx.
• Jar & Native Binary Bundling: Automated linking for 3rd-party .jar files in libs/ and .so binaries in lib/.
• Automatic Multidex Support: DEX splitting and secondary dex injection for large codebases exceeding 64k method limits.
• Custom Release Keystore Profiles: CLI options (--keystore, --alias, --ks-pass, --key-pass) for production signing.
• Incremental Compilation Engine: Hashing system to cache resource compilation and Java bytecode, rebuilding only modified sources.
• Zipalign Optimization Engine: Native 4-byte boundary alignment for uncompressed zip entries prior to signature verification.
• Kotlin Compiler Support: Integration of kotlinc targeting Dalvik/ART bytecode for .kt source files.
• AAR & Remote Dependency Resolution: Parsing .aar archives and automated transitive Maven package resolution.
• Automated ADB Deployment: Device deployment via --install and --launch options using local ADB service.

Maintainer

Created and maintained by Farhan Ali (i.farhanali.dev@gmail.com).