NOTE
Chain of Responsibility
Passing a request through an ordered pipeline of handlers that may process, enrich, reject, or forward it.
This is a historical learning note and may contain outdated or incomplete understanding.
Chain of Responsibility passes a request through an ordered set of handlers. A handler may process, transform, reject, short-circuit, or delegate to the next element.
Middleware/interceptor pipelines are common examples. Keep handler order explicit and define error/short-circuit semantics; otherwise cross-cutting behavior becomes difficult to debug.