diff --git a/crates/ml-alpha/src/trainer/integrated.rs b/crates/ml-alpha/src/trainer/integrated.rs
index 32e16d481..263885f23 100644
--- a/crates/ml-alpha/src/trainer/integrated.rs
+++ b/crates/ml-alpha/src/trainer/integrated.rs
@@ -3782,12 +3782,11 @@ impl IntegratedTrainer {
         // The perception trainer's `step_batched_from_device` records a
         // CUDA event after its training graph launch instead of
         // host-blocking via `cuStreamSynchronize`. By the time we
-        // reach this point, the GPU has executed the entire reward /
-        // PER / controller pipeline since the event was recorded, so
-        // the sync completes instantly (~0 us). This guarantees the
-        // mapped-pinned loss values below are host-visible.
-        self.perception.sync_training_event()
-            .context("sync perception training event")?;
+        // REMOVED: sync_training_event() blocked the host for 5-11ms
+        // every step (87.9% of CUDA API wall time per nsys). The LR
+        // controller uses EMA smoothing over hundreds of steps, so
+        // 2-step deferred mapped-pinned reads are acceptable. The
+        // event is still RECORDED for checkpoint save correctness.
 
         // ── Step 0b: read PREVIOUS step's losses from mapped-pinned ────
         // Mapped-pinned buffers are GPU+host visible. The GPU wrote loss
@@ -4708,9 +4707,14 @@ impl IntegratedTrainer {
         debug_assert_eq!(self.sampled_h_t_d.len(), b_size * HIDDEN_DIM);
         debug_assert_eq!(self.sampled_h_tp1_d.len(), b_size * HIDDEN_DIM);
 
-        // Zero persistent per-iter scratch — raw memset bypasses cudarc's
-        // bind_to_thread + event tracking (~200us overhead per call).
-        {
+        // REMOVED: 24 raw_memset_d8_zero calls that zeroed DQN/outcome/IQN
+        // scratch buffers before each K-loop replay iteration. These buffers
+        // are OVERWRITTEN by backward kernels and reduce_axis0 — the zeroing
+        // was pure waste. At K_max=4, this was 72 memsets/step. nsys measured
+        // 458ms total for cuMemsetD8Async (26% of CUDA API time).
+        // Same pattern already fixed in step_synthetic_body (documented as
+        // "36 memset_zeros REMOVED").
+        if false {
             let s = self.raw_stream;
             unsafe {
                 raw_memset_d8_zero(self.ss_q_loss_dev_ptr, std::mem::size_of::<f32>(), s)