Waypoint-OPD: Alibaba Gates On-Policy Distillation via Early-Late Teacher Shift Agreement

Bingxi Hou · hf · 2026-10-16

Alibaba Cloud researchers propose Waypoint-OPD, an improvement over policy-shift distillation. Standard approaches use the log-probability difference of a teacher before and after RL as supervision on student-generated trajectories, but this endpoint shift cannot reveal whether local action preferences evolved consistently during teacher training—early and late shifts can reinforce or partially cancel each other.

Waypoint-OPD uses an intermediate teacher checkpoint from the same RL run to compare early and late shifts in relative action preferences at student-visited prefixes, gating the endpoint shift by directional agreement and suppressing it when shifts point in opposing directions. Compared to endpoint-only transfer, it requires just one extra frozen-teacher scoring pass, improving reasoning on students like Qwen3-8B/14B/30B distilled from Qwen3-4B teachers with minimal overhead.

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