Your premise about coding agents’ ability to manage complexity and decoherence for themselves sounds conjectural to me. Have you seen it reliably do this?

For my part, I spent a bunch of time this summer trying using a coding agent to help me pay down a technical debt situation that could be described well by this decoherence concept. The initial hope was that Claude would make light work of the project, but that did not happen. It needed constant close hand holding. It could not independently identify competing models. It crumbled in the presence of terminology drift. And it always suggested fixing complexity problems by adding even more epicycles, never by simply eliminating the unnecessary complexity.

That said, it did a great job of implementing plans, and was even helpful for validating them prior to implementation. But it still needed a human to find, diagnose, and prescribe treatment for the problems. Which implies that, where maintainability is concerned, meat is still load bearing.