Runtime

kit.versions.runtime reads the canonical Mojang index at piston-meta.mojang.com/v1/products/java-runtime/.../all.json.

import { RuntimePreference, detectSystem } from "@loontail/minecraft-kit";

const system = detectSystem();
const list = await kit.versions.runtime.list({ system });

const runtime = await kit.versions.runtime.resolve({
  system,
  component: "java-runtime-gamma",
  preference: RuntimePreference.RECOMMENDED,
});

Component selection

The Minecraft per-version manifest declares the required component (e.g. java-runtime-gamma, java-runtime-delta, jre-legacy). kit.targets.resolve picks that component automatically. Override component only to force a different JDK than the manifest declares.

Install layout

Runtime files land under <directory>/runtime/<component>/.... The Java executable lives at:

OS	Path
Windows	runtime/<component>/bin/javaw.exe
macOS	runtime/<component>/jre.bundle/Contents/Home/bin/java
Linux	runtime/<component>/bin/java

Symlinks declared in the per-component manifest are materialized natively on macOS/Linux and fall back to byte copies on Windows where unprivileged users cannot create symlinks. LZMA1 sidecars are decompressed on demand using a pure-JS decoder — no native build step required.