Fabric Observer Gamemode

Adds a new server-sided gamemode to Minecraft Fabric servers. Observer mode is a customisable hybrid between Spectator and Adventure mode.

Setup

1. Install the mods dependencies:
   • Fabric API
   • ClothConfig
2. Install this mod using a jar from the versions page.
3. Start your server and configure using the /observermode command or directly to the config/observermode.json file.

Config

• allow_fly - If players in Observer mode should be able to fly (true/false)
• can_spectate_mobs - If players in Observer mode should be able to specate non-player entities (true/false)
• can_spectate_players - If players in Observer mode should be able to specate other non-specator/observer players (true/false)

How does it work?

This exploits the methods the client uses to get the players gamemode (kind-of a bug). For some features, the client will use the player's gamemode sent with Game Join, Game State Change and other packets, while other features will use the gamemode sent with the player list packets. By telling the client that the player is in spectator mode but telling the player list the player is in adventure mode, we get observer mode.
There are a variety of packets that have mixins to ensure that the client is never aware of being in observer mode, by replaceing it with spectator or adventure depending on the packet.

Libraries

Observer mode takes advantage of the following libraries included in the mod file:

• Fabric-ASM