diff --git a/crates/ml-alpha/src/trainer/perception.rs b/crates/ml-alpha/src/trainer/perception.rs
index 78dce55e8..21a8d3005 100644
--- a/crates/ml-alpha/src/trainer/perception.rs
+++ b/crates/ml-alpha/src/trainer/perception.rs
@@ -2475,10 +2475,15 @@ impl PerceptionTrainer {
         let dt_s = self.cfg.decision_stride.max(1) as f32;
         let n_in_i = HIDDEN_DIM as i32;
         let n_hid_i = HIDDEN_DIM as i32;
-        let block_dim = 128u32;
-        let grid_dim = (HIDDEN_DIM as u32).div_ceil(block_dim);
+        // Phase B fix-up: block-per-batch (Phase B), same launch contract as
+        // training's K-loop. BEFORE this fix the eval path used the legacy
+        // grid=(1,1,1) config which only processed batch 0 — batches
+        // 1..B-1 got GARBAGE h_new. Caught by t6z89-vs-txftz cluster A/B
+        // (val_loss=0.83, mean_auc=chance) on 2026-05-17.
         let cfg_cfc = LaunchConfig {
-            grid_dim: (grid_dim, 1, 1), block_dim: (block_dim, 1, 1), shared_mem_bytes: 0,
+            grid_dim: (b_sz as u32, 1, 1),
+            block_dim: (HIDDEN_DIM as u32, 1, 1),
+            shared_mem_bytes: 0,
         };
         let cfg_grn_fwd = LaunchConfig {
             grid_dim: (b_sz as u32, 1, 1),