diff --git a/crates/specialized/rtx-fsi/tests/fsi2_interface_noise.rs b/crates/specialized/rtx-fsi/tests/fsi2_interface_noise.rs
index 16cd97a..9ef4288 100644
--- a/crates/specialized/rtx-fsi/tests/fsi2_interface_noise.rs
+++ b/crates/specialized/rtx-fsi/tests/fsi2_interface_noise.rs
@@ -113,6 +113,13 @@ fn fsi2_interface_noise_floor() {
             "  multigrid smoother: RED-BLACK symmetric Gauss–Seidel (PERF-2 regime, RTX_FSI2_MG_RB)"
         );
     }
+    // PERF-2 P3-ii (`RTX_FSI2_MG_DEVICE=1`, a cuda-feature build): the V-cycle on the device.
+    if env_or("RTX_FSI2_MG_DEVICE", 0.0) != 0.0 {
+        solver.set_poisson_device(true);
+        println!(
+            "  multigrid V-cycle: CUDA DEVICE, f32 red-black (PERF-2 regime, RTX_FSI2_MG_DEVICE)"
+        );
+    }
     let dt_fluid = harness.dt_fluid;
 
     // Rigid march to operating loads (the floor rides with the loads —