Contractive Restoring Flows: Robust Reasoning Distillation via Orbital Stability

Model distillation provides an alternative when computing resources are limited. How to transfer the reasoning ability from teacher model to student model influences the performance of model distillation. We develop a mathematical framework for reasoning distillation grounded in dynamical systems theory. By modeling the teacher model's residual stream as a discrete dynamical system, we define a precise notion of *orbital stability*: perturbations transversal to the teacher's reasoning trajectory should contract, while the tangential reasoning signal propagates without active suppression. We derive the **Contractive Restoring Flow (CRF)** loss from first principles and prove that, at the loss minimum, it achieves strict transversal contraction at a constant rate $1-\alpha$, leaves the tangential dynamics unconstrained (tangential agnosticism), and produces a global basin of attraction with bounded steady-state error within the linearisation regime. Empirically, reasoning-trajectory distillation with the CRF loss outperforms other distillation methods, and shows greater robustness on long-chain reasoning tasks, supporting the predicted effect of contracting transversal error. The code is avaiable at: https://anonymous.4open.science/r/CRF-5945/.