Codex and Gemini have ACP servers already:
https://github.com/zed-industries/codex-acp https://geminicli.com/docs/cli/acp-mode/
In fact Codex, in OpenAI fashion, have their own protocol as well:
https://developers.openai.com/codex/app-server
Opencode too. These tools are already so programmable and embeddable, it's just Claude Code is a sticking point. But maybe it would be useful to provide a unified CLI and Daemon for all of them.