It's pretty straightforward - I do the same when I'm worried about Fable usage quota. "Your usage is limited, run the token-heavy work through Opus5.5 subagents" simple as that. It works, lets Fable orchestrate, plan, and verify work.

Seems like a workaround that Anthropic might easily turn off if they decide they care.

https://github.com/ucsandman/claude-harness