Tests Pass, Structure Fails: Keeping Long-Lived Systems Maintainable in the Agent Era
Agents optimise for code that works, and the tests that gate the merge cannot see what happens to the structure. Studies of agent-written code show duplication, coupling and complexity growing while pass rates stay flat. For systems that have to live for years, intent has to be machine-readable, enforced by executable checks, measured on three levels, and reviewed at the level of structure instead of lines.