I daily drive Sonnet 5/medium because it gets most things right most of the time at first try, while costing a lot less than Fable.

Opus can give better results on architectural/concept tasks and I use it sparingly, but it still costs more than Sonnet 5. Opus 5 seems to achieve results very close to Fable 5 while costing less (keeps Opus 4.8 pricing IIUC), but still more than Sonnet 5 then.

My understanding is that Opus should be used for planning, macro-level conversations and Sonnet for execution.

So, for coding, for example: Opus for solution design and architectural blueprint and then Sonnet for actual implementation.

Works out cheaper with minimal loss of quality.

At least that's my personal understanding and anecdotal experience.

I don’t think it changes that much. For opus-sized tasks, new Opus is the best model. For enormous things like planning and research, Fable is still the model that can concentrate for longer.

on the API for people who don't want to change models, but I imagine most people will probably switch to their cheaper Opus 5 (cheaper for us and presumably also cheaper for them)

It's you. The benchmarks don't matter much. We have very little hands on experience with this thing yet. Give it a few days, and be cranky then. Right now, it seems it is getting close to Fable level while being 2x cheaper. That's not boring.