ResearchResearch paperLarge Language Models1 source · Oct 9, 2026

BoundaryEvo: Data-Model Co-Evolution at the Capability Boundary for Long-Chain Reasoning Distillation

Distilling long-chain reasoning trajectories from large teacher models provides an effective way to improve the reasoning ability of small language models.

Key points

  • We propose BoundaryEvo, a two-stage data--model co-evolution framework.
  • In Capability Priming, we directly distill a small set of teacher-generated long reasoning trajectories without using a separate model to judge and filter them, allowing the student to acquire an initial reasoning capability before capability-aware data selection.
  • In Capability-Boundary Co-Evolution, we repeatedly select questions that the current student has not mastered but the expert can reliably solve, and update the training data as the student evolves.
  • With only 1,000 training examples, BoundaryEvo consistently outperforms static and dynamic data selection baselines across 11 reasoning benchmarks, raising the original Qwen3.5-4B accuracy from 62.9 to 75.3 on IMO-AnswerBench and from 26.8 to 46.0 on AMO-Bench.

Sources (1)

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Before this

  1. Oct 9, 2026Continually Post-training Small Models via Synthetic Self-distillation
  2. Oct 8, 2026When Do We Need On-Policy Distillation? Distilling on Offline Student Rollouts Is Often Better
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  4. Oct 8, 2026SpatialOPSD: Self-Distilling Spatial Intelligence from Verified Coding Agent Traces
  5. Oct 8, 2026Distilling Routed 3D Privilege for Spatial Reasoning in Vision-Language Models
  6. Oct 8, 2026ViSkill: Reinforcing VLM Agents with Evolving Visual-Native Skills

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