Configurable Zombie AI

Configurable Zombie AI is a Minecraft Forge mod for 1.16.5 that makes vanilla zombies easier to tune for harder survival servers and modpacks.

Instead of hardcoding one zombie behavior profile, the mod exposes runtime commands for server operators so they can change how zombies detect, acquire, keep, and switch targets without restarting the world. Settings are stored with the world and apply to loaded zombies immediately.

What It Does

• Changes zombie follow range.
• Optionally lets zombies ignore line of sight checks.
• Optionally prevents zombies from despawning naturally.
• Replaces vanilla "pick the nearest valid target" behavior with configurable target acquisition.
• Adds a framework for weighted abnormal target-acquisition behaviors.
• Lets operators change which target families specific nearby zombies may attack.
• Adds optional horse targeting for zombies.
• Optionally lets zombies re-evaluate and switch targets over time using weighted rules.
• Adds easy-to-use admin commands to kill zombies globally or within a radius.

The mod keeps vanilla target families enabled by default. Horse targeting is available as an explicit per-zombie option, so existing worlds do not suddenly make every zombie attack horses unless an operator enables it.

Compatibility

• Minecraft: 1.16.5
• Forge: 36.x or newer in the 1.16.5 line
• Language/runtime: Kotlin via KotlinForForge
• Implementation details: Sponge Mixin injections plus Kotlin runtime logic
• Multiplayer clients do not need the mod installed to join a server running it.

How Configuration Works

• All settings are changed in-game through commands.
• Command roots: czai and configurablezombieai
• Permission level: operator level 2
• Settings are saved in world data, so they persist across restarts.
• Per-zombie target-family changes are saved on the affected zombies.
• When settings change, loaded zombies are refreshed immediately.

Command Reference

Examples below use the short root command, but every command also works with configurablezombieai instead of czai.

Core Commands

Command	Description
czai enable	Enables all mod behavior.
czai disable	Disables all mod behavior and restores vanilla follow range for loaded zombies.
czai status	Prints the current live configuration.
czai ignore_LOS <true|false>	Makes zombies ignore line-of-sight checks when choosing valid targets.
czai despawn_prevention <true|false>	Prevents natural zombie despawning when enabled.
czai visibility_range <blocks>	Sets the zombie follow range / detection distance.

Target Type Commands

These commands apply to loaded zombies within the given radius of the command source position.

Command	Description
czai targets radius <blocks> players <true|false>	Toggles whether affected zombies may target players.
czai targets radius <blocks> villagers <true|false>	Toggles whether affected zombies may target villagers.
czai targets radius <blocks> iron_golems <true|false>	Toggles whether affected zombies may target iron golems.
czai targets radius <blocks> turtles <true|false>	Toggles whether affected zombies may target baby turtles on land.
czai targets radius <blocks> horses <true|false>	Toggles whether affected zombies may target horses.
czai targets radius <blocks> all <true|false>	Sets every configurable target family for affected zombies.
czai targets radius <blocks> reset	Restores affected zombies to default target-family settings.

Acquisition Tuning

These settings affect how a zombie picks an initial target after vanilla has already decided that a target goal may run.

Command	Description
czai acquisition distance_variability_from_closest_target <blocks>	Expands the initial candidate pool beyond the closest target by the given distance.
czai acquisition chance_to_auto-select_closest_target <percent>	Chance to guarantee the closest available target is chosen. At 100, the closest target always wins. At 0, any candidate in the acquisition pool may be chosen.
czai acquisition abnormals chance <percent>	Chance that an initial target acquisition roll tries to use an abnormal behavior before falling back to normal acquisition.
czai acquisition abnormals behavior <behavior_id> weight <value>	Sets the relative weight for a specific abnormal behavior id. A weight of 1.0 is baseline, 2.0 is twice as likely as baseline, 0.5 is half as likely, and 0.0 disables that behavior.
czai acquisition abnormals reset_behavior_weights	Resets all registered abnormal behavior weights to 1.0.
czai acquisition abnormals list	Lists registered abnormal acquisition behaviors.

Registered abnormal acquisition behaviors:

Behavior ID	Description
furthest	Selects the farthest valid target inside the zombie's configured acquisition range.
furthest_no_switching	Selects the farthest valid target and prevents this zombie from target-switching while it keeps chasing that target.

Switching Tuning

Switching is off by default. When enabled, zombies periodically re-roll their target inside the same target family as the current one.

Command	Description
czai switching enabled <true|false>	Turns weighted target switching on or off.
czai switching interval <ticks>	How often each zombie evaluates target switching.
czai switching search_radius <blocks>	Radius used to collect alternative targets for switching.
czai switching proximity_bias <value>	Positive values favor nearer candidates; negative values favor farther ones.
czai switching current_target_bias <value>	Positive values make the zombie more likely to stay on its current target.
czai switching closer_than_current_target_bias <value>	Positive values reward candidates that are closer than the current target.

Utility Commands

Command	Description
czai kill all	Kills all loaded zombies across every loaded dimension.
czai kill radius <blocks>	Kills zombies within a radius of the executing player.

Default Values

Setting	Default
Mod enabled	true
Ignore line of sight	false
Prevent despawn	false
Visibility range	35.0 blocks
Acquisition distance variability	0.0 blocks
Chance to auto-select closest target	100.0%
Abnormal acquisition chance	0.0%
Abnormal behavior weights	1.0 per registered behavior
Per-zombie target families	Players, villagers, iron golems, and turtles enabled; horses disabled
Switching enabled	false
Switching interval	40 ticks
Switching search radius	16.0 blocks
Switching proximity bias	0.0
Switching current target bias	1.0
Switching closer-than-current-target bias	1.5

Targeting Notes

• Acquisition respects the per-zombie target-family settings. By default this matches vanilla categories such as players, villagers, iron golems, and baby turtles on land.
• Horse targeting is added by this mod and starts disabled until enabled on specific zombies with czai targets radius <blocks> horses true.
• Abnormal acquisition behavior is attempted only after configured-compatible candidates have been collected. If no abnormal behavior is registered, no behavior has a positive configured weight, or the selected behavior cannot produce a valid target, normal acquisition runs instead.
• Switching does not jump between target families. If a zombie is currently chasing a villager, it will only compare that villager against other villager candidates during a switching pass.
• Line-of-sight bypass still respects attack validity checks and the configured visibility range.

Building From Source

Requirements

• JDK 17 for Gradle dev runs and builds
• A working Gradle environment through the included wrapper

Common Tasks

./gradlew build
./gradlew runClient
./gradlew runServer

Build output is written to build/libs/.

• configurablezombieai-<version>.jar: reobfuscated release jar for normal Forge launchers
• configurablezombieai-<version>-dev.jar: intermediate jar kept as the reobfJar input

Project Layout

• src/main/kotlin: mod entrypoint, saved settings, commands, and runtime AI logic
• src/main/java: mixins and mixin accessors
• src/main/resources: mod metadata, mixin config, and pack metadata

License

This project is licensed under GPL-3.0-or-later. See LICENSE.md.