After "fully vibecoding" (i.e. I don't read the code) a few projects, the important aspect of this isn't so much the different agents, but the development process.

Ironically, it resembles waterfall much more so than agile, in that you spec everything (tech stack, packages, open questions, etc.) up front and then pass that spec to an implementation stage. From here you either iterate, or create a PR.

Even with agile, it's similar, in that you have some high-level customer need, pass that to the dev team, and then pass their output to QA.

What's the evidence? Admittedly anecdotal, as I'm not sure of any benchmarks that test this thoroughly, but in my experience this flow helps avoid the pitfall of slop that occurs when you let the agent run wild until it's "done."

"Done" is often subjective, and you can absolutely reach a done state just with vanilla codex/claude code.

Note: I don't use a hierarchy of agents, but my process follows a similar design/plan -> implement -> debug iteration flow.