SOD-0.6B is a 0.6B student model distilled from a 4B teacher using SOD (Step-wise On-policy Distillation), a method designed for training small language model agents with tool-integrated reasoning capabilities.
SOD addresses the cascading error propagation problem in on-policy distillation for agentic reasoning by introducing an adaptive step-level weighting mechanism that suppresses distillation loss on drifted steps and restores supervision when the student recovers alignment — all at negligible additional computational cost.
We report average@32 over 5 runs on challenging math, science, and code benchmarks.
0.6B Student Results
Method
AIME 2024
AIME 2025
GPQA-Diamond
LiveCodeBench-v6
Average
Vanilla
7.71
12.81
13.24
14.89
12.16
SFT
5.67
5.42
15.20
9.61
8.97
GRPO
4.06
4.90
20.38
15.95
11.32
OPD
16.82
22.95
17.76
22.65
20.04
OPSD_gt
12.63
17.04
17.32
16.73
15.93
OPSD_hint
9.77
14.12
15.98
12.65
13.13
SOD (This Model)
20.84
26.13
22.19
27.72
24.22
Teacher Model (4B)
Method
AIME 2024
AIME 2025
GPQA-Diamond
LiveCodeBench-v6
Average
GRPO
67.60
60.42
55.19
63.13
61.59
Key Highlights
🏆Strong 0.6B agent: Achieves 26.13% on AIME 2025 (average@32)
📈+20.86% over second-best baseline (OPD) on average
💡Minimal extra compute: The divergence metric reuses log-probabilities already computed in the forward pass
Citation
@article{zhong2026sod,title={SOD: Step-wise On-policy Distillation for Small Language Model Agents},author={Zhong, Qiyong and Zheng, Mao and Song, Mingyang and Lin, Xin and Sun, Jie and Jiang, Houcheng and Wang, Xiang and Fang, Junfeng},journal={arXiv preprint arXiv:2605.07725},year={2026}}