ResearchResearch paperLarge Language Models · Reinforcement Learning1 source · Oct 19, 2026

OPDArena: Understanding Learning and Forgetting in On-Policy Distillation

On-policy distillation (OPD) is increasingly used for language model post-training, yet how teacher supervision shapes learning and forgetting remains unclear.

Key points

  • We present OPDArena, a framework comparing supervised fine-tuning (SFT), reinforcement learning with verifiable rewards (RLVR), and OPD across five pretrained models and diverse teacher sources.
  • Teacher choice strongly shapes retention: students of RLVR-trained teachers improve on the target task while retaining prior capabilities, whereas students of SFT-trained teachers incur greater capability loss.
  • Across post-training methods, out-of-domain (OOD) distribution change shows a more consistent positive association with forgetting than in-domain change.
  • Controlled teacher comparisons show that the task-specific preferences teachers acquire through post-training make student updates more concentrated in-domain.

Sources (1)

  • [1]OPDArena: Understanding Learning and Forgetting in On-Policy Distillation
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 19, 01:51 AM
    On-policy distillation (OPD) is increasingly used for language model post-training, yet how teacher supervision shapes learning and forgetting remains unclear.
    We present OPDArena, a framework comparing supervised fine-tuning (SFT), reinforcement learning with verifiable rewards (RLVR), and OPD across five pretrained models and diverse teacher sources.

Extractive summary: sentences quoted from the sources.

Before this

  1. Oct 18, 2026From Unverifiable Domain Text to Cross-Lingual RLVR via Code-Switched Task Synthesis
  2. Oct 18, 2026Conformal Prediction-Enabled Sequence-level Policy Optimization for Reasoning Language Models
  3. Oct 18, 2026Beyond the Teacher: Understanding and Preserving Distillation Overshoot in Agentic On-Policy Distillation
  4. Oct 17, 2026Which Long Documents Matter? A Controlled Study of Data Selection for Context Extension
  5. Oct 16, 2026SimOPD: Relational Knowledge Transfer for On-Policy Distillation
  6. Oct 16, 2026A Stronger Teacher Within: Strengthening MoE Models via On-Policy Bidirectional Distillation

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