…and it's not only BeOS fan fiction! Haiku's got some pretty interesting OS design stuff going on with its package management system. When a package gets dropped into certain blessed folders, their dependencies are automatically resolved and their contents are overlain read-only into the filesystem. The bootloader keeps track of system revisions and lets you easily boot into a previous configuration too. Like a modular version of the APFS system/data volume split https://www.haiku-os.org/docs/develop/packages/Infrastructure.html