Claude 3.5 Sonnet
A mid-sized model beat the largest model of the previous generation while running twice as fast and costing five times less.
Why it matters
The price-quality curve broke inside a single family: the middle model passed the large one in a quarter of a year.
The main gain was in programming: the share of solved problems drawn from real repositories rose sharply, and the model became usable on a code base rather than a single function for the first time. It shipped with an interface where an answer opens in a separate panel and is edited further instead of disappearing into the conversation. That pair, strong coding plus a place where the result lives, set a shape everyone repeated within a year.