The lower the code quality and less coherent the design, the poorer the agent will perform over time as the project grows.

Pure vibe coding pretty much limits the max scope of your project to the capability of the agent, and if you're trying to make something real and maintainable, you'll always end up with something worse than the person who guides it at a lower level.

That being said, there are certainly going to be systemic/built in ways to have coding agents generate coherent architectures. Just it isn't really baked in right now.

Probably an ideal model with current tech is the main coding agent thread that implements things, and a secondary thread that constantly compacts/prunes and cleans up according to specific style rules.

Problem with doing both in same context via AGENTS.md is the LLM often won't adhere to all rules if it's overloaded with many competing instructions. But you can scope the code styling agent prompt tightly and get much higher focus and adherence.