Raincheck deferred multimodal prefill recovered 77.7 percent of the quality that hard token pruning throws away, at up to 24.1 percent lower first-token latency
AspireAI community · arXiv
Multi-turn conversations with multimodal models reuse input context, but long multimodal inputs push up time to first token. Query-aware hard pruning cuts prefill tokens - and permanently drops information a later question may need.
Raincheck decouples initial token selection from later information availability. A pruning method picks tokens for the initial prefill; Raincheck preserves and progressively prefills the unselected tokens in source order, using spare compute capacity during decode, and unfinished prefill continues after the answer is returned during scheduling gaps. Attention visibility control and affine state mapping make context updates work in both full-attention and hybrid recurrent models.
Evaluated on Qwen3-VL-8B and Qwen3.5-9B with 30% initial multimodal-token retention, it recovers on average 77.7% and 60.4% of the quality lost to matched hard pruning on MultiVerse and ConvBench. On MultiVerse the SGLang implementation cuts mean first-turn time to first token by up to 24.1% against full prefill, with under 0.5% increase in mean time per output token. The limitation is the narrow model and benchmark set.
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