Qwen3.5-4B-MBT-R

Qwen/Qwen3.5-4B-Base fine-tuned on traces edited by MBT-R: the editor rewrites the whole trace in one call. It accompanies the paper "Distilling Metacognitive Behaviors through Agentic Editing".

Model Training data
Qwen3.5-4B-Unedited-SFT Unedited teacher traces
Qwen3.5-4B-MBT-R MBT-R (rewrite)
Qwen3.5-4B-MBT-I MBT-I (insert)
Qwen3.5-4B-MBT-A MBT-A (agentic)

Training data: built from the traces in 12kimih/mbt-traces. Code and prompts: GitHub.

Usage

The chat template that ships with the model opens a <think> block, so the generated text is the reasoning, then </think> and the answer. End the question with the instruction used in training:

from vllm import LLM, SamplingParams

llm = LLM("12kimih/Qwen3.5-4B-MBT-R")
question = "Find the remainder when 2^100 is divided by 7."
prompt = question + "\n\nPlease reason step by step, and put your final answer within \\boxed{}."
params = SamplingParams(temperature=1.0, top_p=0.95, max_tokens=122880)
out = llm.chat([{"role": "user", "content": prompt}], params)
print(out[0].outputs[0].text)

The weights are bf16. Long answers are common, so leave room for tens of thousands of tokens.

Training

Setting Value
Base model Qwen/Qwen3.5-4B-Base
Method Full-parameter supervised fine-tuning, loss on assistant tokens only
Epochs 15
Optimizer Muon (Megatron implementation), learning rate 1e-5, weight decay 0
Schedule Constant with 40 warmup steps
Global batch 64 sequences (8 GPUs x 8 accumulation steps), padding-free packing
Maximum length 131,072 tokens
Precision bf16 autocast with fp32 master weights; released in bf16

License

Apache-2.0, following the base model. The training data is CC BY-SA 4.0; see the dataset card for upstream attribution.

Citation

@misc{kim2026distilling,
  title         = {Distilling Metacognitive Behaviors through Agentic Editing},
  author        = {Kim, Ik-hwan and Han, Hyeongrok and Jung, Mingi and Yu, Sangwon and Hong, Jinseok and Kim, Sang Hun and Choi, Yoonyoung and Yoon, Sungroh},
  year          = {2026},
  eprint        = {2602.22508},
  archivePrefix = {arXiv},
  primaryClass  = {cs.AI},
  url           = {https://arxiv.org/abs/2602.22508}
}
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