Offline Mode Fix

A lightweight, plug-and-play Fabric mod that fixes the random chat lag spikes, annoying UI warnings, and texture loading crashes when playing on offline-mode Minecraft servers.

Features

• Zero Chat Lag: Prevents the random network timeout lag spikes that trigger after periods of inactive chat on offline servers.
• Clean UI: Removes the ugly red/gray "Not Secure" sidebars from player messages, restoring the classic chat look.
• Player Head: Restores player head in Player Tab for offline server.
• No Annoying Toasts: Hides the "Unverified Server" popup that appears every time you join the world.
• No Texture Crashes: Stops the log spam and client crashes caused by strict signature validation on custom offline skins.
• Smart Premium Compatibility: Automatically detects if you are using a premium account and lets vanilla checks run normally. You can safely leave this mod installed when playing on premium servers like Hypixel.

Installation

1. Install the Fabric Loader: https://fabricmc.net/
2. Download the correct .jar for your Minecraft version from the releases page.
3. Drop the .jar into your .minecraft/mods folder.

Building from Source

This project uses Stonecutter to seamlessly support multiple Minecraft versions from a single unified codebase. You will need Java 21+ and Git installed on your system.

1. Clone the repository:

   git clone https://github.com/louiszn/offline-mode-fix
   cd offline-mode-fix
   

2. Build the project using the Gradle wrapper. To compile all supported Minecraft versions at once, run:

   • Windows:

     gradlew buildAndCollect
     

   • Linux / macOS:

     ./gradlew buildAndCollect
     

3. Once the build process finishes, you will find the compiled .jar files for every version cleanly organized in the /versions/xxx/build/libs/ directory.

IDE Setup for Development (IntelliJ IDEA)

Because Stonecutter relies on dynamic comments to switch code between mapping versions:

1. Install the Stonecutter Dev plugin by KikuGie from the IntelliJ Plugins Marketplace for proper syntax highlighting and error resolution.
2. Open the Gradle tab, navigate to Tasks -> stonecutter, and double-click Set active project to xxx to swap your active workspace to a specific Minecraft update (e.g., 1.21.11).

How it works (Technical)

Offline-mode servers suffer from several distinct client-side issues introduced in different Minecraft updates:

1. 1.16.4 (The Social Manager): Minecraft checks every incoming message against the PlayerSocialManager blocklist. In offline mode, looking up unauthenticated Version 3 UUIDs causes unnecessary synchronous network requests and processing delays.
2. 1.19+ (Chat Signing): Minecraft attempts to fetch and refresh cryptographic public keys from Mojang's API to verify chat signatures. On offline servers, these background refreshes fail, causing random lag spikes (often triggering after ~30 seconds of inactive chat) and forcing the game to flag all messages as "unsecure" (UI warnings).
3. 1.20.2 (Authlib Strict Validation): The game enforces strict Base64 signature validation for player textures (skins/capes). Dummy signatures provided by offline skin plugins (like BUILDER_APPALLED_PUMPKIN) instantly trigger IllegalArgumentException log spam and texture loading failures.

This mod uses surgical Mixins to:

1. Detect offline (Version 3) UUIDs to instantly bypass the isBlocked and isTextFilteringEnabled network checks.
2. Intercept the chat GUI renderer to hide the "Not Secure" tag.
3. Block the specific "Unverified Server" toast from being added to the screen via the ToastManager / ToastComponent.
4. Bypass YggdrasilServicesKeyInfo strict Base64 property validation if a dummy signature is detected.

Contributing

Contributions are always welcome. If you have an idea for an improvement or find a bug, please open an issue first to discuss what you would like to change. Pull requests are greatly appreciated.