diff --git a/single_shot_inference.py b/single_shot_inference.py
index cc8eafd4..d33f4160 100644
--- a/single_shot_inference.py
+++ b/single_shot_inference.py
@@ -728,7 +728,8 @@ def main():
                 isc_v = gate_isc.float().item() if gate_isc is not None else 1.0/(6.0*448.0)
                 gate_lin.gs = [1.0]
                 gate_lin.ws2 = [torch.tensor([ws2_v], device=dev, dtype=torch.float32)]
-                gate_lin._activation_global_scale = isc_v
+                gate_lin._activation_global_scale = isc_v  # placeholder — runtime gsa overrides this
+                gate_lin._use_runtime_gsa = True  # compute gsa from actual input to avoid E4M3 overflow
                 gate_lin.finalize_weights()
                 router.load_nvfp4_gate(gate_lin)
                 router.load_weights(e_bias=eb.to(dev, torch.float32))
@@ -746,7 +747,8 @@ def main():
                     gate_lin.sf = [g_sf]
                     gate_lin.gs = [g_gs]
                     gate_lin.ws2 = [torch.tensor([g_gs], device=dev, dtype=torch.float32)]
-                    gate_lin._activation_global_scale = 1.0 / (6.0 * 448.0)
+                    gate_lin._activation_global_scale = 1.0 / (6.0 * 448.0)  # placeholder — runtime gsa overrides
+                    gate_lin._use_runtime_gsa = True  # compute gsa from actual input to avoid E4M3 overflow
                     gate_lin.finalize_weights()
                     router.load_nvfp4_gate(gate_lin)
                     router.load_weights(e_bias=eb.to(dev, torch.float32))