K2-Horizon-MoVA-36B-A4B

K2-Horizon-MoVA-36B-A4B is the sparse member of the K2-Horizon family: a Mixture-of-Experts model with Mixture-of-Values attention (MoVA) that stores 36B parameters and runs 4B per token. We have released the final checkpoint; intermediate checkpoints, along with the data and the training code, will be released.

K2-Horizon-MoVA-36B-A4B Highlights

• Frontier-class results at 4B active parameters. On agentic and reasoning benchmarks it outscores open weight dense (approximately 30B model size) and MoE models up to 15× its size; and also performs competitively against closed frontier models (see Benchmark Results).
• 512K context. Native 524,288-token context from the midtraining stages onward.
• Intermediate checkpoints. Intermediate checkpoints will be released so capability changes can be studied across training rather than at a single checkpoint.
• Fully open. Training data/recipe and the training code will be made public.

Benchmark Results

		Open-weight models
	K2-Horizon-MoVA-36B-A4B	Nemotron 3 Ultra	Nemotron 3 Super	G9v3-39A5B	Qwen3.6-35B-A3B	Muse Glimmer-30B	Gemma 4 31B-it
# Params	36B	550B	120B	39B	35B	30B	31B
# Activated params	4B	55B	12B	5B	3B	30B	31B
Architecture	MoE	MoE	MoE	MoE	MoE	Dense	Dense
Agents
tau3-Banking Agentic tool use	26.8	14.2	10.3	22.1	9.3	23.5	14.8
Coding
Terminal-Bench 2.1 Agentic terminal use	58.6	53.9	38.6	32.6	44.9	51.7	43.4
SciCode Scientific coding	38.9	39.9	36.0	34.0	35.8	43.6	43.4
Scientific Reasoning
Humanity's Last Exam (without tools) Expert-level reasoning	25.2	28.4	20.8	17.5	22.2	22.0	23.6
GPQA Diamond Graduate-level science QA	80.8	86.7	80.0	80.5	84.1	83.5	85.7
CritPt Frontier physics reasoning	2.1	3.1	3.1	0.3	0.3	2.6	1.4
General
AA-LCR Long-context reasoning	66.3	71.0	60.3	62.0	66.7	80.0	68.3
AA-Omniscience Accuracy Factual accuracy	18.8	22.6	24.3	14.9	18.8	27.0	20.0
AA-Omniscience Non-Hallucination Non-hallucination rate	69.2	70.3	13.0	87.0	49.5	18.1	15.0

Scores in %. Bold marks the best score in each row. Sections follow the Artificial Analysis Intelligence Index categories. Baseline scores are from Artificial Analysis; Muse Glimmer-30B at high reasoning effort, all other open models in their reasoning mode.

Quickstart

Serving

vLLM, recipe at recipes.vllm.ai/IFM:

vllm serve IFM/K2-Horizon-MoVA-36B-A4B \
  --revision main \
  --tensor-parallel-size 2 \
  --enable-expert-parallel \
  --trust-remote-code \
  --dtype bfloat16 \
  --reasoning-parser k2_horizon \
  --tool-call-parser k2_horizon \
  --enable-auto-tool-choice

Use an exact branch name from the inventory with vLLM's --revision option. For example, --revision pretrain_1100000 selects the final checkpoint of Pretraining, at step 1,100,000.

SGLang recipe validated on 2× H200 in the SGLang K2 Horizon cookbook:

python3 -m sglang.launch_server \
  --model-path IFM/K2-Horizon-MoVA-36B-A4B \
  --revision main \
  --tp 2 \
  --ep 2 \
  --dtype bfloat16 \
  --attention-backend fa3 \
  --json-model-override-args '{"xllm_source_router_gemm_partitions":2}' \
  --reasoning-parser k2_horizon \
  --tool-call-parser k2_horizon \
  --host 0.0.0.0 --port 30000

API Usage

Recommended settings: reasoning_effort="high", temperature=1.0, top_p=0.95. Reasoning depth is selected per request through chat_template_kwargs. Thinking is returned in reasoning_content and the answer in content.

from openai import OpenAI

client = OpenAI(base_url="http://localhost:30000/v1", api_key="EMPTY")
response = client.chat.completions.create(
    model="IFM/K2-Horizon-MoVA-36B-A4B",
    messages=[{"role": "user", "content": "Explain the result step by step."}],
    temperature=1.0,
    top_p=0.95,
    max_tokens=32768,
    extra_body={"chat_template_kwargs": {"reasoning_effort": "high", "tool_call_format": "xml"}},
)
message = response.choices[0].message
print("Reasoning:", getattr(message, "reasoning_content", None))
print("Answer:", message.content)

Our model supports multiple tool-call formats, which can be changed with chat_template_kwargs. The supported values are json, xml, and xml_typed. The default is xml. Keep --tool-call-parser k2_horizon enabled to parse the selected format.

Transformers

Validated with Transformers 5.15.0, PyTorch 2.13.0, Safetensors 0.8.0.

from transformers import AutoModelForCausalLM, AutoTokenizer

model_id = "IFM/K2-Horizon-MoVA-36B-A4B"
tokenizer = AutoTokenizer.from_pretrained(model_id, trust_remote_code=True)
model = AutoModelForCausalLM.from_pretrained(
    model_id, device_map="auto", dtype="bfloat16", low_cpu_mem_usage=True, trust_remote_code=True
)

inputs = tokenizer("Explain why long-context evaluation is difficult.", return_tensors="pt").to(model.device)
inputs.pop("token_type_ids", None)
outputs = model.generate(**inputs, max_new_tokens=32768, temperature=1.0, top_p=0.95, do_sample=True)
print(tokenizer.decode(outputs[0], skip_special_tokens=True))

Training Overview

The table below lists the training stages in order and the purpose of each stage.

Training steps are counted within each stage or phase. Token budgets cover only the additional training in that stage or phase. For example, the 50B tokens listed for SFT Phase 2 are additional to the 219B tokens in Phase 1, bringing the cumulative budget to 269B tokens by the end of Phase 2. Here, B and T denote billion and trillion tokens, respectively.

Each stage or phase continues from the final checkpoint of the preceding stage or phase.

Some stages, such as SFT, have multiple phases with slight changes to the data mix while retaining the same overall purpose.

Training stage	Training steps	Training tokens	Sequence length	Purpose
Pretraining	1100000	22.9T	8K	Pretraining.
Midtraining — Stage 1	55000	1.1T	32K	Context extension.
Midtraining — Stage 2	25000	498B	128K	Context extension.
Midtraining — Stage 3	5500	110B	512K	Context extension.
Midtraining — Stage 4	10000	199B	512K	Continued context extension from Stage 3, with the data mix shifted toward agentic and reasoning SFT data.
SFT — Phase 1	11000	219B	512K	SFT for better domain coverage, starting from the final checkpoint of midtraining stage 4.
SFT — Phase 2	2500	50B	512K	SFT on a high-quality subset of the data used in Phase 1, with learning rate decay.

Release Artifacts

The tables below list the release artifacts for K2-Horizon-MoVA-36B-A4B, their availability, and the expected release dates for remaining items.

Last updated: 2026-09-11

Status:

• Available — fully released for the scope listed;
• Partial — some items are available, with remaining items listed in the notes;
• In Progress — being prepared for release but not yet available.

Artifact Index

Artifact	Link	Status	Remaining items / expected availability
Model card	Hugging Face	Available	N/A
Training logs	W&B	Available	N/A
Blog post	Blog post	Available	N/A
Checkpoints	Checkpoint inventory	Available	See details below
Technical report	Not yet available	In Progress	End of September 2026
Code repository	GitHub	In Progress	End of September 2026

Checkpoint Inventory

Model repository: IFM/K2-Horizon-MoVA-36B-A4B

Branch names below refer to this repository. Patterns containing * group branches by training stage or phase. The * is a placeholder for a training-step number, not a literal branch name. Intermediate checkpoint groups exclude the final checkpoint listed separately; a pattern does not imply that a checkpoint is available at every step.

For example, sft_1_11000 is the checkpoint saved at training step 11,000 within SFT Phase 1, and is the final checkpoint of that phase. The numeric suffix is the step within the named stage or phase, not the cumulative step across all training. Thus, sft_2_2500 refers to step 2,500 within SFT Phase 2.

For a partially released group, the available checkpoints and the remaining checkpoints are listed in the notes.

Checkpoint	Branch / repository	Status	Remaining items / expected availability
Pretrain Intermediate Checkpoints	pretrain_*	Available	N/A
Pretrain Final Checkpoint	pretrain_1100000	Available	N/A
Midtrain Stage 1 Intermediate Checkpoints	mid_1_*	Available	N/A
Midtrain Stage 1 Final Checkpoint	mid_1_55000	Available	N/A
Midtrain Stage 2 Intermediate Checkpoints	mid_2_*	Available	N/A
Midtrain Stage 2 Final Checkpoint	mid_2_25000	Available	N/A
Midtrain Stage 3 Intermediate Checkpoints	mid_3_*	Available	N/A
Midtrain Stage 3 Final Checkpoint	mid_3_5500	Available	N/A
Midtrain Stage 4 Intermediate Checkpoints	mid_4_*	Available	N/A
Midtrain Stage 4 Final Checkpoint	mid_4_10000	Available	N/A
SFT Phase 1 Intermediate Checkpoints	sft_1_*	Available	N/A
SFT Phase 1 Final Checkpoint	sft_1_11000	Available	N/A
SFT Phase 2 Intermediate Checkpoints	sft_2_*	Available	N/A
SFT Phase 2 Final Checkpoint	sft_2_2500	Available	N/A

Note:

• Released K2-Horizon Hugging Face checkpoints (e.g. Huggingface) can be used for inference, evaluation, and downstream fine-tuning (including SFT). Training behavior in the bundled Hugging Face implementation may differ from native xLLM, including the auxiliary load-balancing loss. To continue the original pretraining with xLLM's training behavior, use the native xLLM checkpoint and XLLM runtime.

Best Practices

1. Reasoning effort: always high. All reported results use high reasoning effort. Pass {"chat_template_kwargs": {"reasoning_effort": "high"}} on every request.
2. Sampling parameters. temperature=1.0, top_p=0.95.
3. Serving. Use the validated SGLang recipe above: BF16, TP=2, FlashAttention-3, and the xllm_source_router_gemm_partitions override, which preserves the checkpoint's router numerics. Full recipes for every K2-Horizon size, with measured H200 latency and throughput, are in the SGLang cookbook and the vLLM recipe.
4. Parsers. Enable the k2_horizon reasoning parser for chat, and add the k2_horizon tool-call parser for agent use. Leave both off for plain completion-style generation.

Citation

@misc{k2horizon2026,
  title  = {Introducing K2 Horizon: Frontier Performance, Radically Open},
  author = {{IFM Team}},
  year   = {2026},
  url    = {https://ifm.ai/blog/k2/},
}