Introduction

OhMyLoader (OML) is a mod loader for Minecraft Java Edition: a self-developed bytecode injection engine, a unified high-level mod API, and data-driven declarative content registration — on both the client and the dedicated server. The current stable line is 26.3, and the whole stack runs on Java 27.

Design

Unified semantic API

Mods program against high-level game semantics (events, lifecycle, content registration) and never touch version internals. Cross-version differences are absorbed below the semantic layer, by the per-version adapter, and never leak upward.

Self-developed bytecode engine

The core ships its own lightweight bytecode surgery tooling, replacing the heavy SpongePowered Mixin and Access Transformer layers:

• Injection DSL: anchors like atHead / atReturn / beforeCall combined with payloads like call / modifyArg / redirectCall — semantics aligned with Mixin, but purely declarative and self-checked at startup;
• Mixin class merging: @Shadow / @Overwrite / @Unique / @Accessor / @Invoker are all supported;
• Annotation front-end: developers used to Mixin can keep writing @Mixin / @Inject; the loader compiles the annotations into injection rules and runs them through the same pipeline.

Every rule is verified at startup — handler existence, staticness, signature consistency and match counts. A wrong rule fails the launch, instead of silently doing one thing less in game.

Thin adapters

Each game version gets one thin adapter module (oml-adapter-*) that only maps hook anchors and native types. The current stable line is 26.3; the latest snapshot is tracked separately by oml-adapter-snapshot, which shares its whole implementation with the 26.3 adapter — landing the 26.4 official release is one shape check away, not a rewrite.

Two content tracks

• Code track: declare blocks / items / recipes through ContentRegistry; they are materialized into native content at the registry freeze point;
• Data track: declare data-driven blocks and items in a content.toml inside a .oml archive — no code at all.

Repositories

Repository	Contents
OhMyLoader	The loader: core, API, version adapters, installer, native library
OhMyLoaderGradle	The official Gradle plugin: runtime assembly and runClient / runServer
OhMyLoaderTestMod	The end-to-end verification mod, consuming OML exactly like an external mod project

The three repositories consume each other by Maven coordinate only. See the loader repository's README for the module layout.

API stability

The mod-facing surface comes in three tiers, contracted in the loader's oml-api/README.md:

• Contracted: the @Mod entry, OMLModInitializer / ModContext, Events, the content declaration DSL and the injection DSL — semantically backward-compatible; breaking changes are deprecated for one minor release first.
• Provided, settling: commands, config, network, key bindings / HUD / creative tabs — shipped, allowed to adjust until 1.0, changes recorded in the release notes.
• Escape hatches: everything a platform property hands you — the raw game objects, free to change with any game version, by design.