Function paged_decode_attn_reduce_fp8 

pub fn paged_decode_attn_reduce_fp8(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    workspace: DevicePtr,
    output: DevicePtr,
    seq_lens: DevicePtr,
    num_q_heads: u32,
    head_dim: u32,
    num_splits: u32,
    num_seqs: u32,
    stream: u64,
) -> Result<()>

2026-09-25: Combine split-K partials into the BF16 output. The workspace is F32 [head_dim values, m, l] per split whatever the cache type, so the BF16 split-K’s reduce handle is launched through this function too (qwen3_attention/decode/splitk_dispatch.rs).