‘Plan with a robust model and implement it with a low-cost one’ – does it really work?
It’s been something of a mantra for a while now: use a frontier model for planning, then delegate the implementation to low-cost models, and finally verify the implementation using the frontier model (and then ask the cheap one to do the corrections)
I’m not saying it isn’t the best approach, but speaking from my own experience… I have my doubts.
Let’s say GPT-Sol Medium (or Terra High) are my planner models, and something like DeepSeek V4 Flash or Gemini 3.7 Flash handles the implementations. What I’ve noticed with this workflow is that the number of correction rounds resulting from the review is often enormous, no matter how clear the plan is. In this scenario, I end up burning ‘expensive’ tokens on planning and the review rounds, whilst also burning cheap tokens (which also add to the cost) through constant implementation and correction, which ultimately amounts to a waste of time and money.
So now I’m trying a different approach: once the planning agent has defined the plan, why change it? That agent already has the context to implement it in a single shot and, if anything, I have the implementation reviewed by a couple of low-cost agents. I know it sounds counterintuitive, and I don’t have any large-scale data to back up this approach either, but my feeling is that it works better for me.