Function prefill_rows 

pub fn prefill_rows() -> usize

2026-09-25: PREFILL_ROWS, overridable at launch with METRALE_GLM_PREFILL_ROWS (values below 1 or unparsable are ignored). 1 selects the per-token walk: Glm5NextLayer::prefill takes the batched sub-chunk path only when rows > 1. A width above DENSE_GEMV_BATCHM_MAX_M changes the projection numerics as well as the speed.