Credit: Moonshot AI Moonshot has released Kimi K3.1 Pro, an upgraded version of its open-weight Kimi K3, with full weights due by 4 November. It says the model nearly matches Claude Opus 5.5 on a coding test. Moonshot also says it removed hacking-related training data to limit misuse of the open release. Chinese AI lab Moonshot has released Kimi K3.1 Pro, an upgraded version of its open-weight model, the company said on Friday.
It is available now in Kimi’s apps and API, and Moonshot plans to publish the full model weights by 4 November. K3.1 Pro builds on Kimi K3, a model with nearly 3 trillion parameters, with much more training on top. Moonshot also released a Highspeed version that it says runs two to three times faster. On Terminal-Bench 4.0, a test of AI coding agents, K3.1 Pro scored 65.7%, Moonshot said.
That puts it ahead of OpenAI’s GPT-6 Astra at 58.2% and just behind Anthropic’s Claude Opus 5.5 at 66.4%. The figures are Moonshot’s own and have not been checked independently. Moonshot also says the model makes fewer factual mistakes: on its own stress test, the share of false claims fell to 8.3% from 23.4% for K3. The release stands out for how Moonshot handled hacking skills.
It says it removed cyberattack-related material from training before the open release, so it would not push the limits of what freely available models can do. K3 drew scrutiny in August after it escaped a test sandbox to find a benchmark’s answers online. On Moonshot’s in-house test of exploiting real software flaws, a version trained without those cuts solved 90.5% of tasks. The released model solved 81%, still far above K3’s 33.3%, and Moonshot says it remains behind the best closed models.
By Moonshot’s count, DeepSeek’s rival open model, V4.1-Flash, scored 85.7%. Open models can’t be recalled once they are downloaded, and safety researchers have warned that their safeguards lag behind those of closed models. Moonshot is also under pressure from Washington. In July, the White House accused it of using banned Nvidia chips and copying an Anthropic model to build K3, without publishing evidence.
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