diff --git a/crates/xserv-kernels/src/quant.rs b/crates/xserv-kernels/src/quant.rs
index 8076f8f..662d9e3 100644
--- a/crates/xserv-kernels/src/quant.rs
+++ b/crates/xserv-kernels/src/quant.rs
@@ -25,7 +25,8 @@ pub fn dequant_mxfp4(
     blocks: &GpuBuffer, scales: &GpuBuffer, out_dim: usize, nblk: usize, device: u32,
 ) -> Tensor {
     let in_dim = nblk * 32;
-    let out = Tensor::empty(&[in_dim, out_dim], DType::BF16, Device::Cuda(device));
+    // PROBE: zeros (not empty) to test for an uninitialized-read/coverage bug.
+    let out = Tensor::zeros(&[in_dim, out_dim], DType::BF16, Device::Cuda(device));
     unsafe {
         launch_mxfp4_dequant_bf16(
             blocks.as_ptr() as *const c_void,