Monkey see, monkey do! 🍌

97% of frontier performance

41% cheaper in $$

1.9× faster completion

~3× less likely to cheat

Cost vs pass rate, 7 arms · SWE-Bench Pro · a bare model = oneshot · $/task includes the frontier model's opening turns · † executes with Flash 3.5 · ‡ executes with 5.6 Luna

/plan makes perfect sense. It really shouldn't!

You've heard this pitch; you may have even shipped it. The expensive model is clearly the better architect, but it feels like a waste to use it for the entire pipeline. Why not let it do the "hard part"?

Read the code, think deeply, write a precise plan. Then a model a tenth the price executes the plan. Senior architect, junior engineer.

Sounds great, right?

Find the red dot above, labeled Opus 4.8 + /plan† . Opus plans read-only, Gemini Flash implements: lands at $3.18 per task, 12.7 minutes, 84.6% pass .

Opus doing the entire task by itself, no handoff, no junior: $2.78, 10.1 minutes, 84.6% .

The "cost-saving" measure costs 14% more than not saving.…