Moonshot AI Releases Kimi K3: A 2.8 Trillion Parameter Open MoE Model With Kimi Delta Attention and 1M Context
Moonshot AI simply launched Kimi K3. It is a 2.8-trillion-parameter mannequin with native imaginative and prescient and a 1-million-token context window. Moonshot calls it the world’s first open 3T-class mannequin.
What is Kimi K3?
Kimi K3 is a sparse Mixture-of-Experts (MoE) mannequin constructed on two architectural updates. Those are Kimi Delta Attention (KDA) and Attention Residuals (AttnRes). Both change how info flows throughout sequence size and mannequin depth. K3 targets long-horizon coding, data work, and reasoning.
Moonshot workforce states K3 is the primary open mannequin to achieve 2.8 trillion parameters. For 9 of the previous twelve months, Kimi fashions set the higher certain of open-model sizes.
Moonshot can be direct about the place K3 sits. Overall efficiency nonetheless trails probably the most highly effective proprietary fashions, Claude Fable 5 and GPT 5.6 Sol. Across Moonshot’s personal analysis suite, K3 persistently outperformed different examined fashions.

The Architecture Underneath
Kimi Delta Attention (KDA) is a hybrid linear consideration mechanism. Moonshot states it allows as much as 6.3x quicker decoding in million-token contexts.
AttnRes works alongside the opposite axis, which is depth. It selectively retrieves representations throughout depth relatively than accumulating them uniformly. Moonshot states AttnRes delivers roughly 25% increased coaching effectivity at beneath 2% extra value.
Sparsity is the third lever. K3 makes use of Stable LatentMoE, successfully activating 16 of 896 consultants. At that sparsity, routing and optimization develop into first-order challenges. Quantile Balancing derives knowledgeable allocation immediately from router-score quantiles. That eliminates heuristic updates and a delicate balancing hyperparameter. Per-Head Muon extends Muon by optimizing consideration heads independently. Sigmoid Tanh Unit (SiTU) and Gated MLA enhance activation management and consideration selectivity respectively.
Refined coaching and information recipes accompany these structural modifications. Together they yield roughly 2.5x higher general scaling effectivity than Kimi K2.
Those decisions carry into serving. K3 applies quantization-aware coaching from the SFT stage onward. It makes use of MXFP4 weights with MXFP8 activations for broad {hardware} compatibility. Moonshot workforce recommends supernode configurations with 64 or extra accelerators. Because KDA poses new challenges for prefix caching, Moonshot contributed an implementation to vLLM.
Performance
With the mechanics established, the revealed scores are simpler to learn. All K3 outcomes use reasoning effort set to max. Harnesses differ per benchmark: KimiCode, Claude Code, or Codex.
| Benchmark | Kimi K3 | Fable 5 (w/ fallback) | GPT 5.6 Sol | Opus 4.8 | GLM-5.2 |
|---|---|---|---|---|---|
| DeepSWE | 67.5 | 70.0 | 73.0 | 59.0 | 46.2 |
| Program Bench | 77.8 | 76.8 | 77.6 | 71.9 | 63.7 |
| Terminal Bench 2.1 | 88.3 | 84.6 | 88.8 | 84.6 | 82.7 |
| FrontierSWE | 81.2 | 86.6 | 71.3 | 66.7 | 67.3 |
| SWE Marathon | 42.0 | 35.0 | 39.0 | 40.0 | 13.0 |
| BrowseComp | 91.2 | 88.0 | 90.4 | 84.3 | — |
| Automation Bench | 30.8 | 29.1 | 29.7 | 27.2 | 12.9 |
| GPQA-Diamond | 93.5 | 92.6 | 94.1 | 91.0 | 91.2 |
| HLE-Full | 43.5 | 53.3 | 44.5 | 49.8 | — |
| MMMU-Pro | 81.6 | 81.2 | 83.0 | 78.9 | — |
| OmniDocBench | 91.1 | 89.8 | 85.8 | 87.9 | — |
Two caveats form this desk. 'With fallback' means requests Fable 5 refuses beneath its utilization coverage path to Opus 4.8. Also, BrowseComp used context compaction triggered at 300K tokens. Without that context administration, K3 scores 90.4.
So K3 leads Program Bench, SWE Marathon, BrowseComp, Automation Bench, and OmniDocBench. It trails Fable 5 on FrontierSWE and HLE-Full, and GPT 5.6 Sol on DeepSWE.
Use Cases and Examples
| Use case | Reported instance | Relies on |
|---|---|---|
| Repo-scale engineering | Long periods, minimal human oversight | Kimi Code, /mannequin |
| Vision within the loop | Iterating between code and reside screenshots | Vision, ms://<file-id> |
| Research copy | I–Love–Q relations: 20+ papers, 3,000+ traces of Python | 1M context, auto caching |
| Deep analysis stories | 42-year ASIC research: 2.8k+ fetches, 11k+ pages | Kimi Work, Widgets |
| Document parsing | OmniDocBench rating of 91.1 | Vision, structured output |
Moonshot workforce states one native multimodal structure handles textual content, photographs, and video collectively.
Access and a Minimal Call
K3 is reside on Kimi.com, Kimi Work, Kimi Code, and the API. Access runs by way of the OpenAI SDK towards a Moonshot base URL.
from openai import OpenAI
import os
shopper = OpenAI(api_key=os.environ["MOONSHOT_API_KEY"],
base_url="https://api.moonshot.ai/v1")
completion = shopper.chat.completions.create(
mannequin="kimi-k3",
reasoning_effort="max",
messages=[{"role": "user", "content": "Introduce Kimi K3 in one sentence."}],
)
print(completion.decisions[0].message.content material)
Four guidelines matter. reasoning_effort helps solely max, and the K2.x pondering parameter should not be used. temperature, top_p, and n are fastened, so omit them. max_completion_tokens defaults to 131072 and reaches 1048576. In multi-turn and instrument calls, return the entire assistant message.
Pricing is flat, with no tiering by context size. Cache-hit enter is $0.30/MTok, cache-miss is $3.00/MTok, and output is $15.00/MTok. The cache-hit price is due to this fact the quantity to observe. Moonshot workforce stories above 90% cache hits in coding workloads.
Key Takeaways
- Kimi K3 is a 2.8T-parameter open MoE mannequin activating 16 of 896 consultants.
- KDA, AttnRes, sparsity, and refined recipes give ~2.5x higher scaling than K2.
- K3 leads BrowseComp, SWE Marathon, OmniDocBench; trails Fable 5 on FrontierSWE and HLE-Full.
- OpenAI-SDK appropriate at $0.30/$3.00/$15.00 per MTok, with 1M context.
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