ThreadWeave is a lightweight simulation framework that allows you to move expensive logic from Minecraft thread into other threads while keeping all world modifications thread-safe

- Mod does not modify Minecraft or patch vanilla code. This is library for other mods

All world changes are still executed on the main server thread

Isolated simulation does not have Live Level changing access due to race-conditions on threads so it only processes calculations and e.t.c. This may sound useless unless you start to make AI, reactors, computers or more complicated systems like physics Engines.

Execution changes to world like placing blocks will still depend on Minecraft Thread to not create race conditions

Minecraft mods often suffer from:

Heavy tick logic on main thread
Expensive calculations inside BlockEntities
Complex systems (reactors, AI, factories)

ThreadWeave allows you to move only the computation part into async execution while keeping world safety intact

Only pure data is allowed inside simulation methods

Important limitation

Simulation methods must be pure methods:

input DTO -> output DTO
No side effects allowed inside async execution

How it works?

ThreadWeave works by separating what your mod does into two parts: data processing and world changes

Minecraft normally runs everything on a single thread. That means all calculations, AI, machines, and block logic compete for the same limited performance budget

ThreadWeave changes this by safely moving heavy calculations to background threads

Minecraft Tick
Extract data from BlockEntity
Run simulation in background threads
Get results (updated values)
Apply changes back to world

Modder only defines:

What data is used
What calculation should happen
How results are applied

What ThreadWeave does automatically?

Extracts data from BlockEntity
Runs calculations on multiple threads
Prevents unsafe access to the game world
Applies results back safely
Manages tick timing (normal or accelerated simulation)

Tick modes

WORLD_SYNCED

Runs in sync with Minecraft (20 times per second)

Used for normal game logic

ISOLATED

Runs independently of Minecraft speed

Used for simulations that can run faster or slower than the game itself

Safety

Minecraft world is never accessed from background threads
Only simple data is used during calculations
All world changes happen safely on the main thread

Framework prevents unsafe access to:

Level
Entities
BlockEntities
Server internals

How to use?

Installation Guide

repositories {
    maven {
        url = "https://api.modrinth.com/maven"
    }
}

dependencies {
    implementation "maven.modrinth:thread-weave:{version}"
}

Do not forget to define dependency in mods.toml or you will get minecraft crashed

[[dependencies.${mod_id}]]
modId="thread_weave"
type="required"
versionRange="[{version},)"
ordering="AFTER" // VERY important to load your mod AFTER ThreadWeave
side="BOTH"

For example you have BlockEntity (you can use custom classes. No matter it's minecraft or not)

public class ReactorBlockBE extends BlockEntity implements TickableBE {
    private int heat;
    private int fuel;

    public ReactorBlockBE(BlockPos pos, BlockState state) {
        super(ThreadBlockEntities.REACTOR_BE.get(), pos, state);
    }

    @Override
    public void tick() {
        if (level == null || level.isClientSide()) return;
        heat+=20;
        fuel-=1;
    }
}

I - You need to set what variables will be used in async-processing

public record ReactorData(int heat, int fuel) implements SimulationDelta {}

II - Then you need to split your processing. Simply take all of your calculations and move it to other method. Here you need to set @SimulatedThread annotation. TickMode can be Isolated or WorldSynced. WorldSynced will run at minecraft TPS. Isolated will run at any tick speed you set without minecraft dependency

    //value = MOD_ID + ":reactor"
    //value = "my_mod:reactor"
    @SimulatedThread(value = MOD_ID + ":reactor", mode = TickMode.WORLD_SYNCED)
    public ReactorData simulate(ReactorData data) {
        int heat = data.heat() + 20;
        int fuel = data.fuel() - 1;
        return new ReactorData(heat, fuel);
    }

III - Last you need to submit your data to framework. Use static method "submit"

    @Override
    public void tick() {
        if (level == null || level.isClientSide()) return;

        Simulations.submit(this);
        System.out.println("heat=" + this.getHeat() + " fuel=" + this.getFuel());
    }

IV - Also you need set what classes that will be scanned for @SimulatedThread annotation

    public YourMainModClass(IEventBus modEventBus, ModContainer modContainer) {
        modEventBus.addListener(this::commonSetup);
        Simulations.submitScan(NavMeshSimulation.class);
        ...
    }

You can also manually control interpreter and extractor by @SimulatedInterpreter and @SimulatedExtractor annotations

For example: work ticks

    @SimulatedThread(value = MOD_ID + ":reactor", mode = TickMode.WORLD_SYNCED)
    public ReactorData simulate(ReactorData data) {
        int heat = data.heat() + 20;
        int fuel = data.fuel() - 1;
        return new ReactorData(heat, fuel);
    }

    @SimulatedInterpreter
    public void interpreter(NavData data) {
        this.heat = data.heat();
        this.fuel = data.fuel();
        workTicks++;
    }

Example above is not the best. Custom interpreter is much usable in per-region processing when you need to merge result (Baked Navmesh generation)

    @SimulatedThread(value = MOD_ID + ":navgraph", mode = TickMode.WORLD_SYNCED)
    public NavData simulate(NavProcessorData data) {
        if (processor.isEmpty()) return null;
        return processor.build(navLevel);
    }

    @SimulatedInterpreter
    public void interpreter(NavData data) {
        if (data == null) return;
        for (NavNode node : data.toRemove()) {
            navLevel.nodes.remove(node.id());
        }
        navLevel.nodes.putAll(data.nodes());
        navLevel.portals.putAll(data.portals());
        navLevel.chunkIndices.putAll(data.chunkIndices());
    }

Is this peak optimisation?

No. There is still much work to do. You can follow progress in my discord server

For example most of TickingBlockEntities is not really good with this library due to Level require (Yet)

P.S: I will post a fabric port + other versions later [1.7.10 - 26.x]

Thread Weave