diff --git a/crates/ml/src/hyperopt/adapters/dqn.rs b/crates/ml/src/hyperopt/adapters/dqn.rs
index 5aa0793c2..7562e6be0 100644
--- a/crates/ml/src/hyperopt/adapters/dqn.rs
+++ b/crates/ml/src/hyperopt/adapters/dqn.rs
@@ -482,7 +482,7 @@ impl ParameterSpace for DQNParams {
             // Q_max = max_reward / (1-gamma): gamma=0.88→3.75, gamma=0.99→45.
             // Range [10, 50] covers the full gamma search space [0.88, 0.99].
             (10.0, 50.0),                   // 10: v_range (symmetric: v_min=-v_range, v_max=+v_range)
-            (0.0, 1.0),                     // 11: use_branching (discrete: 0=standard dueling, 1=branching 3-head)
+            (1.0, 1.0),                     // 11: use_branching (FIXED: always true — GPU pipeline requires branching)
             (0.1_f64.ln(), 1.0_f64.ln()),   // 12: noisy_sigma_init (log scale)
             (128.0, 512.0),                 // 13: dueling_hidden_dim (linear, step=128)
             (3.0, 5.0),                     // 14: n_steps (raised min: n=3 is Rainbow standard)