If you maintain a KickJS v3 app, the v5 changelog probably reads like a wall of unfamiliar primitives — defineAdapter , defineHttpContextDecorator , Scope.REQUEST , definePlugin , ContextMeta augmentations. The temptation is to delay: "we'll do it next quarter." This is a conceptual walkthrough of what actually changes between v3 and v5, what to migrate in what order, and where the sharp edges hide. The goal is to leave you with a mental model, not a recipe. The short version: a v5 bump is worth doing if you're still adding features. Per-request boilerplate shrinks, role decorators become typesafe, the dep tree gets smaller, and your codebase stops drifting away from where the framework's own docs and examples now live. The migration is mechanical but not trivial, and it goes much better as a planned slice-by-slice swarm than as a Saturday afternoon. The shape of what changes Three structural shifts define the v3 → v5 jump, with v4 sitting in the middle as a deprecation runway. Adapters become functional.…