Moonshot AI published the full open weights for Kimi K3.1 Pro on Hugging Face on November 4, 2026, matching the date it gave when the model launched in its apps and API in late October. The public repository moonshotai/Kimi-K3.1-Pro is ungated. The same day, Arena's Agent Arena open-source leaderboard listed Kimi K3.1 Pro (Max) first among open models.
Key Facts
| Item | Detail |
|---|---|
| Model | Kimi K3.1 Pro (first model in the K3.1 series) |
| Weights | Open on Hugging Face: moonshotai/Kimi-K3.1-Pro |
| Architecture | Mixture-of-Experts |
| Parameters | 2.8T total; 104B activated per token |
| Context | 1,048,576 tokens |
| Modalities | Text and image (MoonViT-V2 vision encoder, 401M params) |
| Quantization | MXFP4 weights / MXFP8 activations (quantization-aware training) |
| License | Kimi K3.1 Pro License (modified MIT-style with revenue / MAU conditions) |
| API | kimi-k3.1-pro on platform.kimi.ai |
| Suggested runtimes | vLLM, SGLang, TokenSpeed |
| Agent Arena (open filter, Nov 4, 2026 snapshot) | Rank 1 open-source; overall rank 14; marked Preliminary; 18,045 sessions; net improvement 5.29% ± 1.28% |
Background
Moonshot's model card describes K3.1 Pro as an open-weight, natively multimodal agentic model post-trained from Kimi K3 with large-scale joint reinforcement learning. Relative to K3, full-attention Gated MLA layers are replaced with Gated DeepSeek Sparse Attention (Gated DSA) layers for cheaper long-context modeling (69 KDA + 24 Gated DSA layers).
ArtificialWatch confirmed the Hugging Face listing went public on November 4 and counted 96 safetensors shards totaling about 1.56 TB, matching the Kimi K3 release size at the same MXFP4 precision. Moonshot's earlier tech blog had said full weights would ship by November 4 and also introduced Kimi K3.1 Pro Highspeed for faster serving; a separate Highspeed weight repository was not on Hugging Face at the time of that report.
License conditions
The LICENSE file grants free use, modification, fine-tuning, and redistribution, with two commercial gates:
- If the licensee runs a "Model as a Service" business (for example an inference API that lets third parties control inputs or training) and affiliate revenue exceeds $20 million over any consecutive 12 months, a separate agreement with Moonshot is required before commercial use of the Software or derivatives.
- If a commercial product or service using the Software (or derivatives) has more than 100 million monthly active users, or more than $20 million in monthly revenue, "Kimi K3.1-Pro" must be shown prominently in the UI.
Internal use, and use through Moonshot's official products or certified inference partners, are exempt from those two conditions.
Reactions and Impact
On Arena's Agent Arena open-source board dated November 4, 2026, Kimi K3.1 Pro (Max) led open models on net improvement and ranked first on several signal boards Arena publishes for praise versus complaint, steerability, and bash reliability. The listing is labeled Preliminary. Arena ranks from live agent sessions rather than pairwise chat votes; session counts and scores can move as more traffic arrives.
AI Rank previously covered a K3.1 teaser video and a separate K3.1 Pro rate-limit apology. Those stories are not the open-weight release.
What We Don't Know Yet
- Whether Kimi K3.1 Pro Highspeed is a separate downloadable checkpoint
- How Arena's Preliminary ranking will settle with more sessions
- Hardware and cost needed for practical local deployment at full fidelity (third-party size notes exist; Moonshot does not publish a consumer GPU recipe on the model card)