Rethinking Large Language Model Distillation: A Constrained Markov
  Decision Process Perspective
Authors: name: Matthieu Zimmer; name: Xiaotong Ji; name: Tu Nguyen; name: Haitham Bou Ammar
Published: 2025-09-26 20:47:49

Abstract: We introduce a novel approach to large language model (LLM) distillation by
formulating it as a constrained reinforcement learning problem. While recent
work has begun exploring the integration of task-specific rewards into
distillation processes, existing methods typically rely on ad-hoc reward
weighting. We propose a principled optimization framework that maximizes
task-specific rewards while constraining the divergence from the teacher model
to remain below a specified threshold. Our approach adapts constrained state
augmented reinforcement learning to the distillation setting, introducing a
modified reward function that maintains theoretical guarantees of constraint
satisfaction without requiring state augmentation or teacher model access
during deployment and without the computational overhead of the dual Lagrangian
methods. Through extensive experiments on mathematical reasoning tasks, we
demonstrate that our method achieves better constraint satisfaction rates and
better reasoning compared to the soft Lagrangian relaxation baselines while
maintaining competitive task performance. Our framework provides a
theoretically grounded and practically efficient solution for reward-aware
distillation in resource-constrained settings.