Kimi releases K3.1 Pro: an open model in the 3-trillion-parameter class, ranked fourth on the independent Artificial Analysis index, with weights promised for November 4
Prepared by Sintelligent with the help of SI. Published in SI: . Updated: .
A Chinese lab is offering an open model close to Claude Opus 5.5, and the independent index broadly bears that out; the weights are not yet published, and the lab has limited the model's hacking ability with its own measures.
The company calls K3.1 Pro the first model in its new K3.1 series and its strongest "open" model in the 3-trillion-parameter class (2.8 trillion in total and 104 billion active, according to The Decoder); the context window is 1 million tokens. The faster K3.1 Pro Highspeed version, it says, runs 2-3 times faster. By Kimi's own measurements, the model scores 65.7% on Terminal-Bench 4.0 against 58.2% for GPT-6 Astra and 66.4% for Claude Opus 5.5; 92.7% on BenchCAD with tools against 96.2% for Opus 5.5; and 64.4 on OfficeQA Pro v2, which the company calls the best result. The independent Artificial Analysis evaluation, as reported by The Decoder, puts the model fourth on its intelligence index with 55 points, against 58 for Claude Opus 5.5, 56 for Claude Sonnet 5.5 and 56 for Muse Wonder Full. According to The Decoder, prices were cut by a third: $2 per million input tokens and $10 per million output tokens. According to The Next Web and The Decoder, Moonshot removed material about cyberattacks from training so as not to increase what open models can do in hacking: on an in-house vulnerability-exploitation test the released version solved 81% of tasks against 90.5% for a version without that restriction (company measurements). The models are available in Kimi.ai, Kimi Work, Kimi Code and via API; full weights are promised by November 4. Apart from the Artificial Analysis index, the benchmark results are company data; The Next Web notes that an open model cannot be recalled once downloaded.
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