JSSA makes token-level sparse decoding gather-free, reaching up to full-KV throughput at 128K context
Long-context decoding is bottlenecked by repeatedly reading a growing KV cache, and sparse attention reads only part of it, yet token-level selection has not reliably delivered both accuracy and lower latency. JSSA scores candidate tokens in a shared low-dimensional query–key subspace and pairs it with a gather-free indexed-attention kernel that keeps a distinct selected token set for each KV head. Across GQA, hybrid sliding-window/global attention and MLA models it stays closest to full-KV accuracy, and on a B200 at 128K context its decoding throughput reaches up to that of full-KV attention.