diff --git a/crates/ml/src/trainers/dqn/trainer.rs b/crates/ml/src/trainers/dqn/trainer.rs
index 5ccc5c972..e7093d4b0 100644
--- a/crates/ml/src/trainers/dqn/trainer.rs
+++ b/crates/ml/src/trainers/dqn/trainer.rs
@@ -1850,10 +1850,11 @@ impl DQNTrainer {
                                 let configured = self.hyperparams.gpu_n_episodes;
                                 if configured >= 128 {
                                     match detect_gpu_hardware() {
+                                        // Cap at GPU experience collector's buffer limit (4096)
                                         Ok(hw) => configured.max(hw.optimal_n_episodes(
                                             state_dim,
                                             self.hyperparams.gpu_timesteps_per_episode,
-                                        )),
+                                        )).min(4096),
                                         Err(_) => configured,
                                     }
                                 } else {
@@ -1892,10 +1893,11 @@ impl DQNTrainer {
                                 let configured = self.hyperparams.gpu_n_episodes;
                                 if configured >= 128 {
                                     match detect_gpu_hardware() {
+                                        // Cap at GPU experience collector's buffer limit (4096)
                                         Ok(hw) => configured.max(hw.optimal_n_episodes(
                                             state_dim,
                                             self.hyperparams.gpu_timesteps_per_episode,
-                                        )),
+                                        )).min(4096),
                                         Err(_) => configured,
                                     }
                                 } else {
@@ -2001,7 +2003,8 @@ impl DQNTrainer {
                                     aligned_sd,
                                     self.hyperparams.gpu_timesteps_per_episode,
                                 );
-                                let chosen = configured.max(optimal);
+                                // Cap at GPU experience collector's buffer limit (4096)
+                                let chosen = configured.max(optimal).min(4096);
                                 if chosen != configured {
                                     info!(
                                         "GPU auto-scaled n_episodes: {} → {} (SMs={}, VRAM={:.0}MB)",