| title | Diagnosing and Calibrating Tool-Call Boundary Drift in Multi-Teacher On-Policy Distillation |
|---|---|
| authors | Jiabin Shen, Guang Chen, Chengjun Mao |
| date | 2026-07-15 |
| venue | arXiv (preprint, not peer reviewed) |
| id | arXiv:2607.07050 |
| affiliation | Ant Group |
| upvotes | 4 (Hugging Face Daily Papers, 2026-11-01) |
| links | abs pdf hf |
| abstract | Agentic language models must learn when to call tools, when to consume tool responses, and when to answer directly. This makes multi-teacher on-policy distillation a natural training strategy: one teacher can specialize in tool calls, another in direct responses, and the student can learn from both on its own generated distribution. We show that this strategy can induce a behavior shift that is invisible from aggregate losses alone. In a two-teacher tool-use setting, vanilla generalized knowledge distillation improves tool-call recall but also moves the model toward over-calling, where it calls tools on examples that should be answered directly. Aggregate explanations are insufficient: tool-call samples do not receive more token exposure, and full-sequence per-token divergence is not larger for the tool-call teacher. We instead analyze behavior leverage imbalance: local token-level signals at mode- entry and structural positions, such as <tool_call> and function names, can have disproportionate control over the global generation mode. We propose Soft Clamp, a per-token divergence calibration method that dynamically compresses extreme token-level Jensen-Shannon divergence while preserving nonzero gradients. On APIGen-MT, Soft Clamp reduces over-calling from 13.7% to 9.0% relative to vanilla GKD while matching its decision accuracy. In a BFCL multi-turn diagnostic, it also lowers tool-call loops and repeated calls among GKD variants. These results suggest that multi-teacher OPD should monitor where teacher signals act, not only how large they are in aggregate. |
cite
@misc{shen2026diagnosing,
title={Diagnosing and Calibrating Tool-Call Boundary Drift in Multi-Teacher On-Policy Distillation},
author={Jiabin Shen and Guang Chen and Chengjun Mao},
year={2026},
eprint={2607.07050},
archivePrefix={arXiv},
url={https://arxiv.org/abs/2607.07050}
}