Auto-Research System Finds Numerical Bug in vLLM/SGLang Kernels

PMinervini · x · 2026-08-28

An auto-research system at RecursiveSI discovered that some FlashInfer kernels (underpinning vLLM and SGLang) used a hardcoded value of -50,000 as a masked-attention sentinel, which can be smaller than valid QK values and cause instability. The edge case was identified and has been fixed. Silent numerical bugs like this can cause significant debugging headaches.

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