I'm using https://pi.dev/packages/pi-claude-agent-sdk to use the claude sub, but it has the drawbacks of being forced through the claude-sdk. You would still be using the claude system prompt etc., which is one of the main reasons I started using Pi over claude-code.

For my workflow I primarily use a Codex subscription, but farm out adversarial reviews to Fable to clean up unnecessary gpt-ish code (lots of over-engineering). All my UI planning is done with fable, but implemented with OAI agents once I have a solid very specific plan.