Anthropic、Opus 5 は効率重視で能力飛躍なし

But this is really a cost story. From one model update to the next subsequent one, we’ve mostly been seeing modest performance improvements—though they look far more dramatic when you look at a whole year of updates. The discourse among software developers and engineering managers right now is mostly around dealing with cost, and there’s real movement in open-weight models, local models, and other alternatives to cutting-edge frontier models.

Opus 5 sits at $5 per million input tokens, or $25 per million output tokens—on par with its predecessor, but cheaper than Fable. That said, the recently announced Chinese open-weight model Kimi K3 comes in at just $15 per million output tokens at similar performance, so competition is fierce.

Lately, companies like Cursor and Meta have been building “model routers,” systems that automatically select models of varying size and capability from an array of options based on the nature of the prompt. The idea is that you save a lot of tokens (and therefore compute and/or money) by not using something like Fable for every task.

Companies like Anthropic are going to have to keep bringing token costs down, or at least (as is the case here) offering more performance for no additional cost, to continue to see the growth they’ve seen. Otherwise, they will start seeing reduced usage as people turn to smaller or open models once those models get good enough to handle the less challenging development tasks.