Moonshot Ships Kimi K3.1 Pro, Promises Open Weights by Nov 4 and Says It Removed Cyber Training Data to Cap Hacking Skill
Moonshot AI has released Kimi K3.1 Pro in its apps and API and says full open weights will follow by November 4. The company says it stripped cyber-related data from two training stages so the open model would not push the frontier of offensive hacking ability; on its in-house exploit test, the released model scored 81.0% against 90.5% for a version trained without those cuts. All benchmark figures are Moonshot's own and have not been independently checked.
Moonshot AI is making an explicit trade with Kimi K3.1 Pro: release a stronger open-weight model, but deliberately hold back its hacking ability first, and publish the before-and-after numbers. Publishing those numbers makes the trade concrete, though every figure in it comes from Moonshot's own tests. On Friday, October 23, the Chinese lab released Kimi K3.1 Pro in its apps and API and said "the full model weights will be released by Nov 4."
What Moonshot released
Moonshot describes K3.1 Pro as "a post-trained version of Kimi K3, with substantially larger post-training compute," with a 1-million-token context window. The Next Web reported that K3 has nearly 3 trillion parameters. We covered K3's open release in July.
The company also released K3.1 Pro Highspeed, which it says runs two to three times faster. It says K3.1 Pro is rolling out across the Kimi apps, Kimi Work, Kimi Code and its API, and that Kimi Enterprise administrators must turn it on for their organizations because access is off by default at launch.
On Terminal-Bench 4.0, a coding-agent test, Moonshot says K3.1 Pro scored 65.7%, "ahead of GPT-6 Astra (58.2%) and narrowly behind Claude Opus 5.5 (66.4%)." Moonshot also says its claim-level hallucination rate on an internal stress test fell from 23.4% for K3 to 8.3%, and it cautions that those rates "do not represent overall error rates in daily use."
How Moonshot says it limited cyber capability
Moonshot says it saw vulnerability-research performance rise steadily as post-training scaled, and traced it to cyber-related content in its general mid-training data and cyber tasks in its reinforcement-learning environments. "For the open-weight release of K3.1 Pro, we identified and removed cyber-related data from both training stages, while retaining the general-purpose coding tasks needed for model usefulness," the company wrote.
It then tested the model on xdev-bench-hard, its in-house set of exploit tasks based mostly on recently disclosed vulnerabilities in software such as the Linux kernel and Node.js. Moonshot reports these pass@3 results:
- Checkpoint without the cuts: 90.5%.
- Released K3.1 Pro: 81.0%.
- Kimi K3: 33.3%.
- DeepSeek V4.1-Flash: 85.7%, by Moonshot's count.
Moonshot's chart also lists GPT-5.6 Sol, labeled as a third-party evaluation, solving all of the problems. The company says K3.1 Pro's cyber capability "remains behind that of frontier proprietary models that have been publicly available for at least three months."
Why the release policy matters
Moonshot frames two rules for its open-weight releases. "First, we aim not to release open weights that would extend the absolute frontier of cyber capability," it wrote. "Second, we intend to progressively raise the cyber capability available in open weights." It argues that open models let more teams audit their own code, including legacy systems.
The Next Web noted that open models cannot be recalled once downloaded, and that safety researchers have warned their safeguards lag behind those of closed models. It also reported that in July the White House accused Moonshot of using banned Nvidia chips and copying an Anthropic model to build K3, without publishing evidence. Separately, OpenAI said in September that it had attributed a reasoning-extraction cluster to Moonshot.
Limits
- Every benchmark number here is self-reported by Moonshot. Several, including xdev-bench-hard and the hallucination test, are internal benchmarks that outsiders cannot run.
- The released model's 81.0% is still far above K3's 33.3% on the same test, so data removal reduced cyber skill relative to Moonshot's own uncut checkpoint, not relative to the previous model.
- The weights are not out yet. We could not check the model card, license or any independent evaluation, and the "by Nov 4" date is a promise.
Sources
- Kimi (Moonshot AI): Kimi K3.1 Pro Tech Blog: Advancing Open Intelligence (October 23, 2026)
- The Next Web: Moonshot releases Kimi K3.1 Pro and says it cut its hacking skills (October 23, 2026)
- Times of AI: Kimi K3 near-frontier open path (July 17, 2026)
- Times of AI: OpenAI attributes a reasoning-extraction cluster to Moonshot AI (September 30, 2026)