Coding agents are getting remarkably good at making software work, but making a correct change is not always the same as making the right architectural change. When new requirements arrive, agents often extend the structures that already exist, adding behavior to familiar classes, services, and modules rather than asking whether those structures still reflect the domain. Over time, that tendency can leave a codebase technically correct but conceptually outdated. This article explores why coding agents are often structurally conservative, how that can quietly degrade architecture, and why the next generation of agents will need to do more than generate successful patches. They will need to recognize when the software model itself should change.