The server JVM agent (runtime/authlib-injector.jar, mounted at /extras) is gitignored and was previously fetched by the deleted build-stack.sh prep. A fresh checkout had no jar, so minecraft crashlooped with "Error opening zip file or JAR manifest missing". Add a standalone fetch tool: resolves the latest release asset, downloads, and verifies it's a real zip/jar (PK magic) before trusting it. Idempotent (skips if valid, --force to re-download). Wire it into the deploy skill and README launch steps. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
/runtime
Runtime drop-ins mounted read-only into the Minecraft container at /extras.
Required files
authlib-injector.jar— fetch withtooling/fetch-authlib.sh(downloads the latest from https://github.com/yushijinhun/authlib-injector/releases and verifies it's a valid jar). Gitignored.
Mods are no longer listed here; the pack is served via packwiz
(PACKWIZ_URL, see plan/04-packwiz.md).