ZombieBuddy

A powerful framework for Project Zomboid modders that enables Java bytecode manipulation and runtime patching of game classes using ByteBuddy.

ZombieBuddy is a Java agent-based framework that allows modders to:

• Patch game classes at runtime using bytecode manipulation
• Expose Java classes to Lua for enhanced modding capabilities
• Apply patches declaratively using simple annotations
• Load Java code from mods seamlessly

Built on top of ByteBuddy, ZombieBuddy provides a clean, annotation-based API for intercepting and modifying game behavior without requiring access to the game's source code.

Previously, Java mods for Project Zomboid required bundling .class files and manually replacing game files. ZombieBuddy makes this better:

1. No manual file replacement: Automatically loads and applies patches at runtime
2. Precise patching: Patch specific methods with surgical precision - multiple mods can patch the same class without conflicts, and game updates are less likely to break your mod

• 🎯 Annotation-based patching: Use @Patch annotations to declare method patches
• 🔄 Runtime class transformation: Patch classes that are already loaded using retransformation
• 📦 Automatic patch discovery: Scans for patch classes automatically
• 🔗 Lua integration: Expose Java classes and global functions to Lua
• ⚡ Advice and Method Delegation: Support for both advice-based and delegation-based patching
• 🔍 Verbose logging: Configurable verbosity levels for debugging

1. Windows: Download and run ZombieBuddyInstaller.exe, then choose the launch modes to patch. The installer also has an uninstall option and shows a confirmation preview before applying changes.
2. macOS/Linux: Copy ZombieBuddy.jar to the game directory and add -javaagent:ZombieBuddy.jar -- to launch options

📖 Full Installation Guide - Security warnings, manual installation, policy modes

📖 Uninstall Guide - Remove launch options, installed files, and optional config data

1. Add require=\ZombieBuddy, javaJarFile, and javaPkgName to your mod.info
2. Create patches using @Patch annotations
3. Build your JAR and place it in media/java/

📖 Modding Guide - Complete guide to creating Java mods

import me.zed_0xff.zombie_buddy.annotations.Patch;

@Patch(className = "zombie.SomeGameClass", methodName = "someMethod")
public static class MyPatch {
    @Patch.OnEnter
    public static void enter() {
        System.out.println("Method called!");
    }
}

• ZBLuaPerfMon - Real-time Lua performance monitoring
• ZBHelloWorld - Simple example demonstrating basic patching
• ZBetterWorkshopUpload - Workshop integration and Lua exposure
• ZBMacOSHideMenuBar - macOS display patching
• ZBBetterFPS - Render engine optimization
• ZItemTiers - Item rarity with optional Java patches

• Project Zomboid (Build 42+)
• Java 17 (required by the game)
• Gradle (for building Java mods)

If you find ZombieBuddy useful, consider supporting its development:

Copyright (c) 2025-2026 Andrey "Zed" Zaikin

This project is licensed under a permissive open-source license. See LICENSE.txt for details.

Contributions are welcome! Please feel free to submit issues or pull requests.

• GitHub: https://github.com/zed-0xff/ZombieBuddy
• Steam Workshop: https://steamcommunity.com/sharedfiles/filedetails/?id=3619862853
• Related: ZBSpec - Testing framework for PZ mods

This mod uses bytecode manipulation to modify game behavior. Java mods enabled through ZombieBuddy have unrestricted access to your system and can execute arbitrary code. Use at your own risk. Only install Java mods from trusted sources and review their source code when available.