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goshi-hider edited this page Jul 24, 2026 · 1 revision

OmniMixin

OmniMixin is a Fabric library mod for Minecraft 1.21. It doesn't add any blocks, items, or gameplay by itself — instead, it wraps a big pile of vanilla mixin hooks (movement, combat, blocks, items, entities, rendering, and a small data-sync layer) behind clean, documented, Fabric-style events, so you don't have to write and maintain those mixins yourself.

If you've ever wanted to know "how much fall damage is this player about to take, and can I change it?" or "can I stop this specific mob from being knocked back?" without hand-writing a mixin into LivingEntity, that's what this mod is for.

Why this exists

Fabric API already gives you events for the big, common things — block break, item use, entity join world, and so on. But a lot of everyday gameplay logic lives inside vanilla methods that Fabric API doesn't expose an event for: how knockback strength is calculated, whether a specific block's redstone power gets modified, whether an entity is allowed to jump right now. Getting at those normally means writing your own mixin, picking the right injection point, and hoping you got the target method signature right.

OmniMixin does that work once, centrally, and exposes the result as a regular Event<T> (the same net.fabricmc.fabric.api.event.Event type you already use for Fabric API's own events). You add OmniMixin as a dependency, register a listener, and you're working with plain Java objects — no @Inject, no @At, no bytecode descriptors.

What's inside

Subsystem Package Covers
Movement dev.goshi.omnimixin.api.event.movement walking/ground speed, jumping, sprinting, flight speed, entity pushing
Combat dev.goshi.omnimixin.api.event.combat damage, knockback, armor, status effects, healing, death, absorption
World and Blocks dev.goshi.omnimixin.api.event.world block interaction, placement, breaking, mining speed, redstone power
Items and Inventory dev.goshi.omnimixin.api.event.item item use, equipment changes, inventory slot clicks, block loot
Entity Lifecycle and AI dev.goshi.omnimixin.api.event.entity ticking, despawning, spawn rules, mob AI goals and targeting
Rendering dev.goshi.omnimixin.api.event.render (client-only) HUD drawing, screens, camera FOV, per-entity rendering
Networking and Data Sync dev.goshi.omnimixin.api.sync declare a field on an entity that auto-syncs to nearby clients and saves to NBT

Every event follows the same shape, described in Architecture — a Cancellable you can call to veto something, and/or a Mutable* wrapper you can write a new value into. Once you've used one OmniMixin event, you already know how to use all of them.

A quick taste

public class MyMod implements ModInitializer {
    @Override
    public void onInitialize() {
        // Double all fall damage.
        PlayDamage.MODIFY_AMOUNT.register(ctx -> {
            if (ctx.source().isOf(DamageTypes.FALL)) {
                ctx.finalDamage().multiply(2.0f);
            }
        });

    // Stop players from sprinting while they're holding a shield up.
    PlaySprint.CAN_SPRINT.register(ctx -&gt;
            !ctx.entity().isUsingItem()
    );
}



}

That's the whole shape of the API. No mixin, no injection annotation, no Yarn method descriptor to get wrong.

Where to start

  • New to the mod? Read Getting Started first.
  • Want to understand the Cancellable/Mutable* pattern before diving into a specific subsystem? Read Architecture.
  • Otherwise, jump straight to the subsystem page you need from the table above.
  • Curious what's not implemented yet, and why? See Known Limitations.

A note on how honest this documentation tries to be

This project deliberately implements pieces incrementally rather than stubbing everything out at once, and each page here says plainly which parts of a subsystem are covered and which are still open. If a method or event doesn't exist yet, it's listed in Known Limitations along with the actual reason it was held back — usually "the real vanilla signature couldn't be verified with enough confidence to ship it," not "we forgot." If you find something here that's wrong, please open an issue — this mod has never been run through a live game instance yet (see the note at the bottom of Getting Started), so bug reports from real testing are genuinely valuable.

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