ASPIRE: Asynchronous Batched Self-Speculative Decoding for Long-Context LLM Inference

Abstract

Long-context LLM inference is bottlenecked by attention, whose repeated KV-cache reads make decoding memory-bound. Self-speculative decoding alleviates this by drafting tokens with sparse attention and verifying them with full attention, but existing batched methods remain *synchronized*: all requests in a batch share a single draft-verify schedule, even though the optimal draft length varies widely across requests and changes dynamically within each request. We propose **ASPIRE**, a non-synchronized batched self-speculative decoding framework built on three components. First, a *unified mixed forward* allows drafting and verifying requests to coexist in the same batched forward pass, removing the need for global draft-verify phases. Second, a lightweight *online speculation scheduler* uses per-request acceptance-rate estimates and a batch-aware cost model to let each request independently choose when to verify. Third, an *intra-draft refresh layer* performs full attention at a single designated layer during drafting, updating the sparse context at every draft step to reduce staleness during drafting. Across three models and five reasoning and long-context benchmarks, ASPIRE achieves $1.70$-$4.58\times$ speedup in decoding throughput over autoregressive baselines and improves average speedup by approximately 27\% over the strongest prior self-speculative baselines. The code is available at https://github.com/Amir-zsh/ASPIRE.