diff --git a/dsv4/kernels/attention/fmha_6warp_multirow.cuh b/dsv4/kernels/attention/fmha_6warp_multirow.cuh
index d4bf44a3..c5bdc17a 100644
--- a/dsv4/kernels/attention/fmha_6warp_multirow.cuh
+++ b/dsv4/kernels/attention/fmha_6warp_multirow.cuh
@@ -225,15 +225,18 @@ fmha_6warp_multirow_kernel(FmhaMultiRowParams params) {
             }
         }
 
-        // Warp-level max reduction (only active lanes participate meaningfully)
-        // Inactive lanes have row_max = -INFINITY, which is safe for fmax
-        row_max = wmax(row_max);
+        // Per-row max: each lane has its own row's values.
+        // NO cross-lane reduction — each row's max is independent.
+        // For T=1, only lane 0 has data; we still skip wmax because
+        // the single row's max is already in lane 0.
+        // However, for T=1 backward compat: lane 0 needs its value
+        // written to sRowMax. No broadcast needed for multi-row.
 
         if (lane < (unsigned)warp_num_rows) {
             sRowMax[warp_row_start + lane] = row_max;
         }
 
-        // Compute exp and sum per row
+        // Compute exp and sum per row (independent per lane)
         float row_sum = 0.0f;
         if (lane < (unsigned)warp_num_rows) {
             for (int j = 0; j < SK_TILE; j++) {
@@ -241,7 +244,7 @@ fmha_6warp_multirow_kernel(FmhaMultiRowParams params) {
                 row_sum += s_vals[j];
             }
         }
-        row_sum = wsum(row_sum);
+        // No cross-lane sum reduction — each row's sum is in its lane
 
         if (lane < (unsigned)warp_num_rows) {
             sRowSum[warp_row_start + lane] = row_sum;