Kimi K3 Is the Biggest Open-Weight Model Ever Shipped. Here's What Actually Matters.

A Beijing startup just out-shipped every US lab's open-weight strategy

On July 16, Moonshot AI — the Alibaba-backed startup behind Kimi — put Kimi K3 behind an API. Today, July 27, the full weights land on Hugging Face. No waitlist, no "responsible scaling" essay, no six-month delay between "we built something scary" and "here, run it yourself." Just 2.8 trillion parameters, open, on the day they said it would happen.

That's not a small model with a big number attached. It's the largest open-weight model ever released, full stop. And unlike most "open" releases that quietly underperform their closed competitors, K3 is winning on the benchmarks developers actually care about.

Let's get into what's real and what's marketing.

The numbers