Yes
Once the plan is good, Opus does the rest fine and is much cheaper
henry-hong on Hacker News
In the thread “Claude Fable 5.2 and Mythos 5.2”, replying to this comment
Helped: Using the bigger model only for initial planning of complex changes.
… The one place I'd reach for the bigger model is the first plan for a change that touches many parts at once. Once the plan is good, Opus does the rest fine and is much cheaper.