I do a similar thing with a "planner agent" that uses the cheapest (I think it's using openai-gpt-5.2-mini or something at like 20 cents for 1M.) that more or less emits a plan name, task list and the task list has a recommended model in each task. It's not perfect, but many of our tasks are accomplished with lighter weight models. When doing code generation or fixing we upgrade to a more expensive model, planning and decisions are done more cheaply. Keep in mind the tasks are relatively constrained, so planning done with a cheap agent makes sense here. An open-ended agent would likely use a more expensive call for planning.