Fedora CoreOS is built, tested, and released differently than the operating systems from which it originated, Fedora Atomic Host and CoreOS Container Linux. This talk covers a very brief overview of how CL and FAH images were previously built and how the Fedora CoreOS build system, CoreOS Assembler, improves upon them. It discusses how CoreOS Assembler aims to unify the developer and production build processes and ensure reproducibility. It also covers the CoreOS Assembler developer workflow both for developing the OS and build process itself. Finally it covers what is coming next for CoreOS Assembler. No resources required, max attendees, etc