Ruby::Box: Rethinking Code Reloading with Isolated Namespaces | Ruby Elders

Ruby lives in a single global object space. Classes, modules, and constants can see each other, reopen each other, and override each other freely. This is one of Ruby’s greatest design strengths: it enables expressive DSLs, powerful metaprogramming, and a level of flexibility that few languages can match. At the same time, it comes with a cost. When everything is global, isolation is difficult, and undoing already executed code — especially code that has already been loaded — quickly becomes problematic. Ruby developers value fast feedback loops, yet restarting a web server breaks flow, and safely reloading code inside a long-running process is fragile by nature. Once a file is loaded or a constant is defined, the runtime offers no simple way to rewind that state.