China's Moonshot AI releases Kimi K3, the largest open-source model ever, rivaling top U.S. systems

Beijing-based artificial intelligence startup Moonshot AI on Thursday released Kimi K3, a 2.8-trillion-parameter model the company says is the largest open-source AI model in the world. Moonshot AI announced the release, which was timed ahead of the 2026 World Artificial Intelligence Conference in Shanghai. The company said benchmarks show the model performs neck-and-neck with the most powerful proprietary systems from Anthropic and OpenAI. Full model weights are scheduled to be released on July 27, according to details shared by researchers who reviewed the company's technical documentation. The model features a 1-million-token context window, native visual understanding capabilities, and an always-on reasoning mode the company calls "thinking mode." It is built on two architectural innovations developed internally: Kimi Delta Attention and Attention Residuals. On the API side, Kimi K3 is compatible with the OpenAI SDK and priced at $3 per million input tokens and $15 per million output tokens. Benchmark results drawn from public leaderboard data and a private evaluation by analytics firm Artificial Analysis show Kimi K3 scored 1,687 on GDPval-AA v2, placing third behind Claude Fable 5 Max and GPT-5.6 Sol Max. On AA-Briefcase, it scored 1,527 for second place. It achieved a state-of-the-art score of 91.2 out of 100 on BrowseComp. Moonshot AI also showcased a 48-hour autonomous chip design demonstration and a computational astrophysics case where K3 reproduced the universal I-Love-Q relation in approximately two hours.