diff --git a/crates/ml-alpha/cuda/nan_scan.cu b/crates/ml-alpha/cuda/nan_scan.cu
index 2bfe38637..1623e6a14 100644
--- a/crates/ml-alpha/cuda/nan_scan.cu
+++ b/crates/ml-alpha/cuda/nan_scan.cu
@@ -269,6 +269,9 @@ extern "C" __global__ void nan_scan(
             case 44: label = "mamba2_l1_fwd_b_proj_pre_scan"; break;
             case 45: label = "mamba2_l1_fwd_x_pre_scan";      break;
             case 46: label = "mamba2_l1_fwd_h_s2_pre_scan";   break;
+            case 47: label = "train_vsn_out";       break;
+            case 48: label = "step_entry_w_in_W";   break;
+            case 49: label = "step_entry_w_in_b";   break;
             default: break;
         }
         const int step = (int)isv[RL_STEP_COUNTER_ISV_INDEX];
diff --git a/crates/ml-alpha/src/trainer/perception.rs b/crates/ml-alpha/src/trainer/perception.rs
index 913476b80..aad1cd442 100644
--- a/crates/ml-alpha/src/trainer/perception.rs
+++ b/crates/ml-alpha/src/trainer/perception.rs
@@ -5200,6 +5200,21 @@ impl PerceptionTrainer {
             (w.raw_ptr(), w.len())
         };
         self.nan_scan(41, l1_w_a_ptr, l1_w_a_len)?;
+        // 2026-05-29: w_in weights at step entry were uncovered by 41
+        // (which only covers w_a). PROJ verdict identified the L1 w_in
+        // gemm path as a NaN producer — scan its weights here to
+        // disambiguate "w_in weights NaN at step entry" vs
+        // "w_in weights clean but gemm produces NaN from clean inputs".
+        let (l1_w_in_w_ptr, l1_w_in_w_len) = {
+            let w = &self.trunk.mamba2_l1().w_in.weight;
+            (w.raw_ptr(), w.len())
+        };
+        self.nan_scan(48, l1_w_in_w_ptr, l1_w_in_w_len)?;
+        let (l1_w_in_b_ptr, l1_w_in_b_len) = {
+            let b = &self.trunk.mamba2_l1().w_in.bias;
+            (b.raw_ptr(), b.len())
+        };
+        self.nan_scan(49, l1_w_in_b_ptr, l1_w_in_b_len)?;
         let (l2_w_a_ptr, l2_w_a_len) = {
             let w = &self.trunk.mamba2_l2().w_a.weight;
             (w.raw_ptr(), w.len())
@@ -5307,6 +5322,12 @@ impl PerceptionTrainer {
                 .map_err(|e| anyhow::anyhow!("variable_selection_fwd: {:?}", e))?;
             }
         }
+        // 2026-05-29: scan VSN output in the TRAIN path (label 6 only
+        // covers the forward-graph dispatch path, not this train path).
+        // PROJ verdict from prior coder identified Mamba2 L1 projections
+        // as NaN producers — disambiguate "VSN output NaN feeds
+        // gemms" vs "VSN out clean, gemms still NaN".
+        self.nan_scan(47, self.vsn_out_d.cuda_data().raw_ptr(), self.vsn_out_d.numel())?;
 
         // ── 2. Mamba2 stack-1 forward — writes into mamba2_fwd_scratch.
         //       Consumes vsn_out_d (gated features). in_dim = FEATURE_DIM (40).