China's Moonshot Unveils Kimi K3, Claiming World's Largest Open-Weight AI Model

Chinese AI startup Moonshot on Friday introduced Kimi K3, a 2.8 trillion-parameter model that it said is the world's largest open-weight artificial intelligence system. The company claimed its performance approaches that of Anthropic's frontier Fable model, a leading US system.

Open-weight models allow users to download, run, and customise the underlying AI, unlike proprietary closed-source models. The launch comes a month after Anthropic's Fable and Mythos models were withdrawn by the US government due to security concerns, according to reports. This underscores the rapid progress of China's open AI ecosystem in narrowing the gap with advanced US systems.

Companies like Moonshot, Z.ai, and MiniMax are releasing increasingly powerful models at sharply lower costs. This challenges the long-held Western assumption that Chinese developers trail their American peers by months. Moonshot said Kimi K3 is the first open-weight model to approach the 3 trillion-parameter mark and is designed for advanced reasoning, long-horizon coding, and knowledge work. The model features a 1 million-token context window, allowing it to process and retain substantially more information than earlier generations in a single prompt.

Moonshot stated that Kimi K3 performed competitively with Fable 5 and substantially outperformed OpenAI's Opus 4.8, GPT 5.6 Sol, and GPT 5.5 in GPU kernel optimisation—techniques that maximise hardware utilisation and minimise latency. The model 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, multi-step tasks.

Chinese AI firms are accelerating model release cycles as the global AI race intensifies. Following Z.ai's GLM-5.2, which scored near top US closed-source models on benchmark tests, the consensus that Chinese AI was at least six months behind has been undermined. Hong Kong-listed MiniMax is developing its own 2.7 trillion-parameter model, expected by the third quarter of 2026, and plans to release its frontier-level multimodal model H3 soon, according to Reuters. The race toward trillion-parameter systems reflects demand for autonomous systems capable of complex reasoning and recursive self-improvement.

Before Kimi K3, Meituan's LongCat-2.0 and DeepSeek's V4-Pro led China's AI industry with 1.6 trillion total parameters, while several other domestic rivals have crossed the trillion-parameter threshold. Moonshot said Kimi K3 incorporates two significant architectural upgrades that improve computing efficiency and enable it to complete long-horizon coding tasks with minimal human supervision. Backed by Alibaba and Tencent, Moonshot has been expanding its capabilities and capital. Bloomberg reported last month that the startup was seeking $2 billion in fresh funding at a valuation of about $30 billion ahead of a potential Hong Kong listing.