Ironically, Devin Desktop is one of those tools. It supports any harness that supports ACP (which is most of them)—you can use Claude Code, Codex, OpenCode, etc from the Devin Desktop UI.

I'm currently experimenting with OpenSpec[0] as the "framework" and using different subscriptions for different parts of the spec-driven process: Opus via Claude Code for exploration, Devin SWE for building, and GLM 5.2 via the Z.ai Coding Plan for verification. I don't love having to mix and match harnesses, but in practice it's barely more effort than switching models.

[0]: https://openspec.dev/

Is that surprising? It is standard "embrace, extend, extinguish" from a company not in a strong enough position to do the third one.