diff --git a/crates/ml/src/trainers/dqn/fused_training.rs b/crates/ml/src/trainers/dqn/fused_training.rs
index bf7018dd7..8d06c0a19 100644
--- a/crates/ml/src/trainers/dqn/fused_training.rs
+++ b/crates/ml/src/trainers/dqn/fused_training.rs
@@ -792,7 +792,10 @@ impl FusedTrainingCtx {
             &self.stream,
         ).map_err(|e| anyhow::anyhow!("PER seg_tree_update: {e}"))?;
 
-        eprintln!("FUSED_DIAG: step {} — PER update done", self.steps_since_varmap_sync);
+        eprintln!("FUSED_DIAG: step {} — PER update done, syncing full step", self.steps_since_varmap_sync);
+        self.trainer.stream().synchronize()
+            .map_err(|e| anyhow::anyhow!("post-step sync: {e}"))?;
+        eprintln!("FUSED_DIAG: step {} — full step GPU sync complete", self.steps_since_varmap_sync);
         // Bookkeeping.
         agent.fused_post_step_gpu_bookkeeping()
             .map_err(|e| anyhow::anyhow!("Fused GPU bookkeeping: {e}"))?;