💡 The paper introduces JetSpec, a speculative decoding framework designed to improve the inference speed and acceptance rates of large language models. The problem addressed is the scaling limitation of speculative decoding, which accelerates autoregressive large language models by drafting multiple tokens and verifying them in parallel. However, increasing the draft budget only improves speed when acceptance remains high and drafting overhead stays low, creating a scaling ceiling.

The proposed JetSpec framework combines efficient forward drafting with causal conditioning to break this ceiling. It trains a causal parallel draft head over fused hidden states from the frozen target model, producing candidate trees whose scores align with the target model's autoregressive factorization. This approach enables JetSpec to convert larger draft budgets into longer accepted prefixes and higher end-to-end speedup.

The method is compared to bidirectional-head and tree-based speculative decoding baselines across various benchmarks, including math, coding, and chat tasks on dense and MoE models. The results show that JetSpec consistently outperforms these baselines, achieving significant speedup on different workloads. Specifically, JetSpec achieves up to 9.64x speedup on math tasks and 4.58x on open-ended conversational workloads, with further latency gains demonstrated through integration with virtual large language models under realistic serving loads.

Overall, the paper contributes a novel speculative decoding framework that breaks the scaling ceiling of prior methods, enabling faster and more efficient large language model inference. The code and models are made available for further research and development.