that's a good question. UML - at least the mainstream version pushed by e.g. Rational - failed for many reasons. A couple pertinent to this discussion: 1. La

that's a good question. UML - at least the mainstream version pushed by e.g. Rational - failed for many reasons. A couple pertinent to this discussion: 1. Lack of closed loop between the "spec" and working code (your spec rot point). The Rational Unified Process(RUP) was a grossly inefficient, heavily manual undertaking. Mapping between artefacts - e.g. "Platform Independent Models" and "Platform Specific Models" was a manual, largely heuristic based approach. As a consequence the models were not generally kept up to date as the project evolved. 2. User experience mismatch. Developers were asked to create diagrams instead of writing code. Tool usability was poor ("write code with a mouse") and the artefacts didn't fit well with necessary tools like diffing and source code control (try diffing an xml file textually). Coding agents have some potential for alleviating (1) in that they can read the result code and, at least to some extent, ensure spec and code are in sync. (2) is more open. Some users - those proportionally more interested in solving the problem than designing/writing code - are more comfortable with natural-language-based specs and exploration. Those more experienced/comfortable with code will likely see those specs more akin to UML diagrams: a distraction from the real thing.