Function gdn_exact_chain 

pub fn gdn_exact_chain(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    h_state: DevicePtr,
    query: DevicePtr,
    key: DevicePtr,
    value: DevicePtr,
    gate: DevicePtr,
    beta: DevicePtr,
    output: DevicePtr,
    h_inter: [DevicePtr; 3],
    num_k_heads: u32,
    num_v_heads: u32,
    k_dim: u32,
    strides: [u32; 4],
    stream: u64,
) -> Result<()>

2026-10-01: The single-sequence exact verify (gdn_exact_chain{2,3,4}, chosen by the caller’s kernel): K rows of one sequence’s strided-decode chain in one launch. h_state is updated to the state after the last row, h_inter[t] receives the state after row t (t < K - 1; the other entries must still be valid pointers and are not written). Rows are strides = [qk, v, gate|beta, out] floats apart.