Paper Detail

Jet-Long: Efficient Long-Context Extension with Dynamic Bifocal RoPE

Haozhan Tang, Zerui Wang, Yuxian Gu, Song Han, Han Cai

huggingface Score 17.5

Published 2026-07-08 · First seen 2026-07-10

General AI

Abstract

Modern LLMs are increasingly deployed in long-context applications such as retrieval-augmented generation, repository-level coding, and agentic workflows whose accumulated reasoning and tool traces routinely push the input an order of magnitude past the pretraining window, making zero-shot context extension the dominant deployment path for open-weight checkpoints. Most existing zero-shot methods fix a single rescaling factor up front, so an aggressive factor sacrifices short-context fidelity while a conservative one breaks down at long contexts. We propose Jet-Long, a tuning-free zero-shot method that pairs a local RoPE-faithful window with a long-range window whose rescaling factor adapts dynamically to the current sequence length, recovering the base model exactly at short inputs while extrapolating cleanly at long ones. An inclusion-exclusion attention merge and an on-the-fly RoPE correction rotation make the bifocal construction essentially free at inference; fused into a single CuTe kernel, long-context prefill reaches up to 1.39times FA2 throughput on H100 (approaching the Hopper-only FA4), and single-batch generation incurs le 4% overhead at every length. On Qwen3-1.7B/4B/8B up to 128K context, Jet-Long leads RULER by +4.79/+2.18/+2.03~pp over the strongest baseline at 1.7B/4B/8B, achieves the best overall accuracy on HELMET-RAG (a benchmark identified by HELMET as the most efficient predictor of downstream long-context performance) and attains the lowest PG-19 perplexity. Jet-Long also generalizes to hybrid attention architectures such as Jet-Nemotron for further long-context improvement without retraining, and remains hyperparameter-resilient for ease of deployment.

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BibTeX

@misc{tang2026jet,
  title = {Jet-Long: Efficient Long-Context Extension with Dynamic Bifocal RoPE},
  author = {Haozhan Tang and Zerui Wang and Yuxian Gu and Song Han and Han Cai},
  year = {2026},
  abstract = {Modern LLMs are increasingly deployed in long-context applications such as retrieval-augmented generation, repository-level coding, and agentic workflows whose accumulated reasoning and tool traces routinely push the input an order of magnitude past the pretraining window, making zero-shot context extension the dominant deployment path for open-weight checkpoints. Most existing zero-shot methods fix a single rescaling factor up front, so an aggressive factor sacrifices short-context fidelity whi},
  url = {https://huggingface.co/papers/2607.07740},
  keywords = {LLMs, long-context applications, retrieval-augmented generation, agentic workflows, zero-shot context extension, RoPE-faithful window, long-range window, attention merge, RoPE correction rotation, bifocal construction, CuTe kernel, FA2, FA4, H100, Hopper, RULER, HELMET-RAG, PG-19 perplexity, hybrid attention architectures, Jet-Nemotron, code available, huggingface daily},
  eprint = {2607.07740},
  archiveprefix = {arXiv},
}

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