Function w4a16_gemv_qkvz 

pub fn w4a16_gemv_qkvz(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    input: DevicePtr,
    weight: &QuantizedWeight,
    output: DevicePtr,
    n: u32,
    k: u32,
    num_groups: u32,
    head_k_dim: u32,
    vheads_per_group: u32,
    head_v_dim: u32,
    stream: u64,
) -> Result<()>

2026-09-25: w4a16_gemv over a weight whose rows interleave Q, K, V and Z per group; the output is stored deinterleaved as [Q | K | V | Z].