Function hc_head_site 

pub fn hc_head_site(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    streams: DevicePtr,
    head: &HcHeadWeights,
    hc: &HcWeights,
    y_out: DevicePtr,
    scratch: DevicePtr,
    num_tokens: u32,
    hidden_size: u32,
    norm_eps: f32,
    stream: u64,
) -> Result<()>

2026-09-25: The model-level final collapse before the LM head. In the low-rank family this is also the model’s final normalization: the Qwen3.8-Flash-Next config parser sets final_norm_identity (config/src/parsers/qwen4_exp.rs), and the mixer’s hc_norm normalizes.