containerOf

The real on-disk jar behind root. A JiJ root nests UnionFileSystem ->jij: PathFileSystem -> UnionFileSystem -> real file; each layer names its backing path reflectively (loader classes, not on the common compile classpath).

The container's IDENTITY, for staleness only — never where a class is READ from. That is JarLocator's job, and it refuses to answer with the container on purpose (a different library's type set).