Where Does Long-Context Supervision Actually Go? Effective-Context Exposure Balancing
Not on the map. Why?
Abstract (arXiv)
Long-context adaptation is often viewed as window scaling, but this misses a token-level supervision mismatch: in packed training with document masking, each target token's effective context remains short. We introduce EXACT, a supervision-allocation objective that assigns extra weight to long effective-context targets by inverse frequency within the long tail. Across seven Qwen/LLaMA CPT configurations, EXACT improves all 28 trained/extrapolated NoLiMa and RULER comparisons. On Qwen2.5-0.5B, NoLiMa improves by +10.09 (trained) and +5.34 (extrapolated); RULER by +10.69 and +5.55. On LLaMA-3.2-3B, RULER improves by +17.91 and +16.11. Standard QA/reasoning are preserved (+0.24 macro change across six benchmarks). A distance-resolved probe shows gains arise when evidence is thousands of tokens away, while short cases remain unchanged. Results support a supervision-centric thesis: long-context adaptation depends on how strongly training supervises long-context predictions.
Key facts. Cited by 4 papers in the map (data through 14 Oct 2026). Builds on 45 of its 51 references that are in the map. First posted on arXiv 11 May 2026.
Builds on
45 of 51 references.
References · 45
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33 more
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Citing papers per year: 2026: 4.
4 papers.
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