Chinese start-up Moonshot AI has launched the world’s largest open-source artificial intelligence model, claiming to outperform leading US systems from Anthropic and OpenAI in some capabilities, as domestic developers race to challenge American dominance.Beijing-based Moonshot said its Kimi K3, unveiled late on Thursday, had achieved “open frontier intelligence” with 2.8 trillion parameters, which was significantly larger than previous open models from Chinese competitors, including DeepSeek’s 1.6 trillion-parameter V4 Pro or Zhipu AI’s 744 billion GLM 5 series, making it the largest open-source model so far.Parameters, a machine-learning term, measure the complexity of AI systems during training, with a higher figure generally indicating a stronger model.K3 was designed for long-horizon coding, knowledge work and reasoning tasks, the company said in a blog post.While acknowledging that K3’s “overall performance still trails the most powerful proprietary models,” the company said the model had demonstrated frontier-level performance across a range of evaluations, “consistently outperforming other tested models”, including OpenAI’s GPT-5.5, Anthropic’s Claude Opus 4.8, and rival Zhipu AI’s latest GLM-5.2.Moonshot’s latest model comes one month after its crosstown rival Zhipu AI launched GLM-5.2 to global acclaim. Photo: Shutterstock ImagesK3 outperformed Anthropic’s Claude Fable 5 and OpenAI’s GPT-5.6 Sol – two of the most advanced AI systems from US labs – on a few evaluations, including Program Bench and SWE Marathon, according to self-reported benchmark results by the company.