BEIJING – Chinese AI start-up Moonshot on July 17 unveiled Kimi K3, a 2.8 trillion-parameter model that it said is the world’s largest open-weight AI system and delivers performance approaching US giant Anthropic’s frontier Fable model.

The launch, which comes a month after Anthropic’s Fable and Mythos models were abruptly withdrawn by the US government due to security concerns, underscores how quickly China’s open AI ecosystem is narrowing the gap with the most advanced US systems.

Companies including Moonshot, Z.ai and MiniMax are releasing increasingly powerful models at sharply lower cost, challenging long-held assumptions in the West that Chinese developers trail their American peers by months.

Moonshot said Kimi K3 is the first open-weight model to approach the three trillion-parameter mark and is designed for advanced reasoning, long-horizon coding and knowledge work. The model features a one million-token context window, allowing it to process and retain substantially more information than earlier generations in a single prompt.

Kimi K3 “performed competitively with Fable 5 (with fallback) and substantially outperformed (OpenAI’s) Opus 4.8, GPT 5.6 Sol, and GPT 5.5” in terms of Graphics Processing Unit (GPU) kernel optimisation, the company said. The term refers to techniques that maximise AI hardware utilisation and minimise latency.

The model has also posted strong results in third-party evaluations.

Arena.ai ranked Kimi K3 first in a benchmark assessing web interface-building capabilities, while Vals AI placed it second overall behind Fable 5 and ahead of GPT-5.6 Sol. Artificial Analysis said the model delivered performance comparable to OpenAI’s GPT-5.5 and Anthropic’s Claude Opus 4.8, particularly on tests measuring complex, multistep tasks.

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