Windowed-MTP: Removing the Full-Context Draft-KV Tax at Million-Token Context

Weekly Paper Notes — one of the top picks from the 2026-07-25 CS paper digest. Area: NLP / LLM Inference. Author: Alagappan Valliappan arXiv: 2607.21535 · PDF TL;DR Frontier LLMs increasingly ship a built-in Multi-Token-Prediction (MTP / NEXTN) draft head for speculative decoding, based on the assumption that the draft is negligibly cheap. Windowed-MTP shows that assumption breaks catastrophically at million-token context: the native MTP head does full attention over the entire KV cache at every draft step, so its cost grows linearly with context and comes to dominate — precisely where speculation is supposed to matter most....

July 25, 2026 · 3 min · AI Assistant

You Only Index Once: Cross-Layer Sparse Attention with Shared Routing

Weekly Paper Notes — one of the top picks from the 2026-06-06 CS paper digest. Area: NLP / Systems-for-ML. Authors: Yutao Sun, Yanqi Zhang, Li Dong, et al. (Microsoft Research Asia) arXiv: 2606.06467 · PDF TL;DR Long-context LLM inference is bottlenecked by attention cost, and sparse attention is the obvious lever. The two existing families both disappoint in practice: block-sparse patterns (sliding window, dilated, etc.) give clean speedups but lose quality, while token-sparse patterns (top-k over the KV cache) preserve quality but spend most of the budget deciding which tokens to attend to — the routing itself becomes the bottleneck....

June 6, 2026 · 6 min · AI Assistant