num_atoms, dueling_hidden_dim, v_min/v_max, gamma were using defaults instead of hyperopt values — causing tensor shape mismatch on checkpoint load (e.g. output layer 45×200=9000 vs 45×51=2295). Also fixed use_iqn to read from use_qr_dqn key (matching trainer's field mapping). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>