diff --git a/reproductions/offline/qdt.py b/reproductions/offline/qdt.py
new file mode 100644
index 00000000..94910e94
--- /dev/null
+++ b/reproductions/offline/qdt.py
@@ -0,0 +1,332 @@
+import argparse
+from datetime import datetime
+from typing import Optional, Union
+
+import gym
+import numpy as np
+from torch.optim.lr_scheduler import CosineAnnealingLR
+
+import d3rlpy
+from d3rlpy.algos import CQL, IQL
+from d3rlpy.dataset import InfiniteBuffer, ReplayBuffer
+from d3rlpy.types import NDArray
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--dataset", type=str, default="hopper-medium-v2")
+    parser.add_argument("--context_size", type=int, default=20)
+    parser.add_argument("--model_file", type=str, default=None)
+    parser.add_argument(
+        "--q_learning_type", type=str, default="cql"
+    )  # Q-learning algorithm ("cql" or "iql")
+    parser.add_argument("--seed", type=int, default=1)
+    parser.add_argument("--gpu", type=int)
+    args = parser.parse_args()
+
+    # get timestamp
+    timestamp = datetime.now().strftime("%Y%m%d%H%M%S")
+
+    dataset, env = d3rlpy.datasets.get_dataset(args.dataset)
+
+    # first fit Q-learning algorithm to the dataset
+    if args.model_file is not None:
+        # load model and assert type
+        q_algo_loaded = d3rlpy.load_learnable(args.model_file)
+        if not isinstance(q_algo_loaded, (CQL, IQL)):
+            raise ValueError(
+                "The loaded model is not an instance of CQL or IQL."
+            )
+        # cast to the expected type
+        q_algo = q_algo_loaded
+    else:
+        if args.q_learning_type == "cql":
+            q_algo = fit_cql(dataset, env, args.seed, args.gpu, timestamp)
+        elif args.q_learning_type == "iql":
+            q_algo = fit_iql(dataset, env, args.seed, args.gpu, timestamp)
+
+    # relabel dataset RTGs with the learned value functions
+    print("Relabeling dataset with RTGs...")
+    if not isinstance(dataset._buffer, InfiniteBuffer):
+        raise ValueError("Dataset must be an InfiniteBuffer.")
+
+    relabel_dataset_rtg(
+        dataset._buffer, q_algo, args.context_size, seed=args.seed
+    )
+
+    # fit decision transformer to the relabeled dataset
+    fit_dt(
+        dataset, env, args.context_size, args.seed, args.gpu, False, timestamp
+    )
+
+    return
+
+
+""" --------------------------------------------------------------------
+    Aargument dataset
+-------------------------------------------------------------------- """
+
+
+def relabel_dataset_rtg(
+    buffer: InfiniteBuffer,
+    q_algo: Union[CQL, IQL],
+    k: int,
+    num_action_samples: int = 10,
+    seed: int = 0,
+) -> None:
+    """
+    Relabel RTG (reward-to-go) to the given dataset using the given Q-function.
+
+    Args:
+        buffer (InfiniteBuffer): Buffer holding trajectory dataset.
+        q_algo: Trained Q-learning algoirthm.
+        k (int): Context length for DT.
+        seed (int): The random seed.
+        num_action_samples (int, optional): The number of action samples for
+            V function estimation. Defaults to 10.
+        gpu (int, optional): The GPU device ID. Defaults to None.
+        timestamp (str, optional): The timestamp for experiment name.
+            Defaults to None.
+    """
+    # fix seed
+    d3rlpy.seed(seed)
+
+    prev_idx = -1
+    for n in range(buffer.transition_count):
+        episode, idx = buffer._transitions[-n - 1]  # get transitions backwards
+        if idx > prev_idx:
+            # get values for all observations in the episode
+            values = []
+            for _ in range(num_action_samples):
+                sampled_actions = q_algo.sample_action(episode.observations)
+                values.append(
+                    q_algo.predict_value(episode.observations, sampled_actions)
+                )
+            value = np.array(values).mean(axis=0)
+            rewards = np.squeeze(episode.rewards, axis=1)
+            rtg = 0
+        else:
+            start = max(0, idx - k + 1)
+            rtg = rewards[idx] + np.maximum(rtg, value[idx + 1])  # relabel rtg
+            relabelled_rewards = np.zeros_like(rewards)
+            relabelled_rewards[idx] = rtg
+            relabelled_rewards[start:idx] = rewards[start:idx]
+            relabelled_episode = d3rlpy.dataset.components.Episode(
+                observations=episode.observations,
+                actions=episode.actions,
+                rewards=np.expand_dims(relabelled_rewards, axis=1),
+                terminated=episode.terminated,
+            )
+            buffer._transitions[-n - 1] = (relabelled_episode, idx)
+
+        prev_idx = idx
+
+    return
+
+
+""" --------------------------------------------------------------------
+    Fit offline RL algorithms to the given dataset.
+-------------------------------------------------------------------- """
+
+
+def fit_cql(
+    dataset: ReplayBuffer,
+    env: gym.Env[NDArray, int],
+    seed: int = 1,
+    gpu: Optional[int] = None,
+    timestamp: Optional[str] = None,
+) -> "CQL":
+    """
+    Fit the CQL algorithm to the given dataset and environment.
+
+    Args:
+        dataset (MDPdataset): Dataset for the training.
+        env (gym.Env): The environment instance.
+        seed (int): The random seed.
+        gpu (int, optional): The GPU device ID. Defaults to None.
+        timestamp (str, optional): The timestamp for experiment name.
+            Defaults to None.
+    """
+    # fix seed
+    d3rlpy.seed(seed)
+    d3rlpy.envs.seed_env(env, seed)
+
+    encoder = d3rlpy.models.encoders.VectorEncoderFactory([256, 256, 256])
+
+    if "medium-v0" in env.spec.id:
+        conservative_weight = 10.0
+    else:
+        conservative_weight = 5.0
+
+    cql = d3rlpy.algos.CQLConfig(
+        actor_learning_rate=1e-4,
+        critic_learning_rate=3e-4,
+        temp_learning_rate=1e-4,
+        actor_encoder_factory=encoder,
+        critic_encoder_factory=encoder,
+        batch_size=256,
+        n_action_samples=10,
+        alpha_learning_rate=0.0,
+        conservative_weight=conservative_weight,
+    ).create(device=gpu)
+
+    cql.fit(
+        dataset,
+        n_steps=500000,
+        n_steps_per_epoch=1000,
+        save_interval=50,
+        evaluators={"environment": d3rlpy.metrics.EnvironmentEvaluator(env)},
+        experiment_name=(
+            f"CQL_{env.spec.id}_{seed}"
+            if timestamp is None
+            else f"CQL_{env.spec.id}_{seed}_{timestamp}"
+        ),
+        with_timestamp=False,
+    )
+
+    return cql
+
+
+def fit_iql(
+    dataset: ReplayBuffer,
+    env: gym.Env[NDArray, int],
+    seed: int = 1,
+    gpu: Optional[int] = None,
+    timestamp: Optional[str] = None,
+) -> "IQL":
+    """
+    Fit the IQL algorithm to the given dataset and environment.
+
+    Args:
+        dataset (MDPdataset): Dataset for the training.
+        env (gym.Env): The environment instance.
+        seed (int): The random seed.
+        gpu (int, optional): The GPU device ID. Defaults to None.
+        timestamp (str, optional): The timestamp for experiment name.
+            Defaults to None.
+    """
+    # fix seed
+    d3rlpy.seed(seed)
+    d3rlpy.envs.seed_env(env, seed)
+
+    reward_scaler = d3rlpy.preprocessing.ReturnBasedRewardScaler(
+        multiplier=1000.0
+    )
+
+    iql = d3rlpy.algos.IQLConfig(
+        actor_learning_rate=3e-4,
+        critic_learning_rate=3e-4,
+        batch_size=256,
+        gamma=0.99,
+        weight_temp=3.0,
+        max_weight=100.0,
+        expectile=0.7,
+        reward_scaler=reward_scaler,
+    ).create(device=gpu)
+
+    # workaround for learning scheduler
+    iql.build_with_dataset(dataset)
+    assert iql.impl
+    scheduler = CosineAnnealingLR(
+        iql.impl._modules.actor_optim,  # pylint: disable=protected-access
+        500000,
+    )
+
+    def callback(algo: d3rlpy.algos.IQL, epoch: int, total_step: int) -> None:
+        scheduler.step()
+
+    iql.fit(
+        dataset,
+        n_steps=500000,
+        n_steps_per_epoch=1000,
+        save_interval=10,
+        callback=callback,
+        evaluators={
+            "environment": d3rlpy.metrics.EnvironmentEvaluator(env, n_trials=10)
+        },
+        experiment_name=(
+            f"IQL_{env.spec.id}_{seed}"
+            if timestamp is None
+            else f"IQL_{env.spec.id}_{seed}_{timestamp}"
+        ),
+        with_timestamp=False,
+    )
+
+    return iql
+
+
+def fit_dt(
+    dataset: ReplayBuffer,
+    env: gym.Env[NDArray, int],
+    context_size: int = 20,
+    seed: int = 1,
+    gpu: Optional[int] = None,
+    compile: bool = False,
+    timestamp: Optional[str] = None,
+) -> None:
+    """
+    Fit decisiton transformer to the given dataset and environment.
+
+    Args:
+        dataset (MDPdataset): Dataset for the training.
+        env (gym.Env): The environment instance.
+        seed (int): The random seed.
+        gpu (int, optional): The GPU device ID. Defaults to None.
+        timestamp (str, optional): The timestamp for experiment name.
+            Defaults to None.
+    """
+    # fix seed
+    d3rlpy.seed(seed)
+    d3rlpy.envs.seed_env(env, seed)
+
+    if "halfcheetah" in env.spec.id:
+        target_return = 6000
+    elif "hopper" in env.spec.id:
+        target_return = 3600
+    elif "walker" in env.spec.id:
+        target_return = 5000
+    else:
+        raise ValueError("unsupported dataset")
+
+    dt = d3rlpy.algos.DecisionTransformerConfig(
+        batch_size=64,
+        learning_rate=1e-4,
+        optim_factory=d3rlpy.optimizers.AdamWFactory(
+            weight_decay=1e-4,
+            clip_grad_norm=0.25,
+            lr_scheduler_factory=d3rlpy.optimizers.WarmupSchedulerFactory(
+                warmup_steps=10000
+            ),
+        ),
+        encoder_factory=d3rlpy.models.VectorEncoderFactory(
+            [128],
+            exclude_last_activation=True,
+        ),
+        observation_scaler=d3rlpy.preprocessing.StandardObservationScaler(),
+        reward_scaler=d3rlpy.preprocessing.MultiplyRewardScaler(0.001),
+        position_encoding_type=d3rlpy.PositionEncodingType.SIMPLE,
+        context_size=context_size,
+        num_heads=1,
+        num_layers=3,
+        max_timestep=1000,
+        compile_graph=compile,
+    ).create(device=gpu)
+
+    dt.fit(
+        dataset,
+        n_steps=100000,
+        n_steps_per_epoch=1000,
+        save_interval=10,
+        eval_env=env,
+        eval_target_return=target_return,
+        experiment_name=(
+            f"QDT_{env.spec.id}_{seed}"
+            if timestamp is None
+            else f"QDT_{env.spec.id}_{seed}_{timestamp}"
+        ),
+        with_timestamp=False,
+    )
+
+
+if __name__ == "__main__":
+    main()