diff --git a/helx/envs/brax.py b/helx/envs/brax.py
index 8fb675b..19cba37 100644
--- a/helx/envs/brax.py
+++ b/helx/envs/brax.py
@@ -19,7 +19,7 @@
 from jax.random import KeyArray
 
 from helx.base.spaces import MAX_INT_ARR, Continuous
-from helx.base.mdp import Timestep, TRANSITION, TERMINATION
+from helx.base.mdp import Timestep, StepType
 from .environment import EnvironmentWrapper
 
 
@@ -46,7 +46,7 @@ def reset(self, key: KeyArray) -> Timestep:
             t=jnp.asarray(0),
             observation=state.obs,
             reward=state.reward,
-            step_type=TRANSITION,
+            step_type=StepType.TRANSITION,
             action=self.action_space.sample(key),
             state=state.pipeline_state,
             info={**state.info, **state.metrics}
@@ -58,7 +58,7 @@ def _step(self, key: KeyArray, timestep: Timestep, action: jax.Array) -> Timeste
             pipeline_state=timestep.state,
             obs=timestep.observation,
             reward=timestep.reward,
-            done=timestep.step_type == TERMINATION,
+            done=timestep.step_type == StepType.TERMINATION,
             info=timestep.info,
             metrics=timestep.info
         )
diff --git a/helx/envs/dm_env.py b/helx/envs/dm_env.py
index 00e3970..65801bd 100644
--- a/helx/envs/dm_env.py
+++ b/helx/envs/dm_env.py
@@ -22,7 +22,7 @@
 import jax.numpy as jnp
 from jax.random import KeyArray
 
-from helx.base.mdp import Timestep, TERMINATION, TRANSITION, TRUNCATION
+from helx.base.mdp import Timestep, StepType
 from helx.base.spaces import Space, Discrete, Continuous
 from .environment import EnvironmentWrapper
 
@@ -68,11 +68,11 @@ def timestep_to_helx(
     discount = timestep.discount
 
     if timestep.step_type == dm_env.StepType.LAST:
-        step_type = TERMINATION
+        step_type = StepType.TERMINATION
     elif discount is not None and float(discount) == 0.0:
-        step_type = TRUNCATION
+        step_type = StepType.TRUNCATION
     else:
-        step_type = TRANSITION
+        step_type = StepType.TRANSITION
 
     return Timestep(
         observation=obs,
diff --git a/helx/envs/environment.py b/helx/envs/environment.py
index 2ec9e47..b80d56e 100644
--- a/helx/envs/environment.py
+++ b/helx/envs/environment.py
@@ -24,7 +24,7 @@
 import jax
 from jax.random import KeyArray
 
-from helx.base.mdp import Timestep, TRANSITION
+from helx.base.mdp import Timestep, StepType
 from helx.base.spaces import Space
 
 
@@ -46,7 +46,7 @@ def step(
     ) -> Timestep:
         # autoreset
         next_timestep = jax.lax.cond(
-            timestep.step_type == TRANSITION,
+            timestep.step_type == StepType.TRANSITION,
             lambda timestep: self._step(key, timestep, action),
             lambda timestep: self.reset(key),
             timestep,
@@ -57,7 +57,7 @@ def step(
 class EnvironmentWrapper(Environment):
     env: Any = struct.field(pytree_node=False)
 
-    @abc.abstractclassmethod
+    @abc.abstractmethod
     def wraps(cls, env: Any) -> EnvironmentWrapper:
         raise NotImplementedError()
 
diff --git a/helx/envs/gym.py b/helx/envs/gym.py
index 2baa24e..f123070 100644
--- a/helx/envs/gym.py
+++ b/helx/envs/gym.py
@@ -27,7 +27,7 @@
 import numpy as np
 from gym.utils.step_api_compatibility import TerminatedTruncatedStepType as GymTimestep
 
-from helx.base.mdp import Timestep, TERMINATION, TRANSITION, TRUNCATION
+from helx.base.mdp import Timestep, StepType
 from helx.base.spaces import Continuous, Discrete, Space
 from .environment import EnvironmentWrapper
 
@@ -61,11 +61,11 @@ def timestep_from_gym(gym_step: GymTimestep, action: Array, t: Array) -> Timeste
     obs, reward, terminated, truncated, _ = gym_step
 
     if terminated:
-        step_type = TERMINATION
+        step_type = StepType.TERMINATION
     elif truncated:
-        step_type = TRUNCATION
+        step_type = StepType.TRUNCATION
     else:
-        step_type = TRANSITION
+        step_type = StepType.TRANSITION
 
     obs = jnp.asarray(obs)
     reward = jnp.asarray(reward)
@@ -101,7 +101,7 @@ def reset(self, seed: int | None = None) -> Timestep:
             # TODO(epignatelli): remove try/except when gym3 is updated.
             # see: https://github.com/openai/gym3/issues/8
             timestep = self.env.reset()
-        return timestep_from_gym(timestep, action=jnp.asarray(-1), t=jnp.asarray(0))
+        return timestep_from_gym(timestep, action=jnp.asarray(-1), t=jnp.asarray(0))  # type: ignore
 
     def _step(self, key: KeyArray, timestep: Timestep, action: Array) -> Timestep:
         next_step = self.env.step(np.asarray(action))
diff --git a/helx/envs/gymnasium.py b/helx/envs/gymnasium.py
index f7c5711..ae881bf 100644
--- a/helx/envs/gymnasium.py
+++ b/helx/envs/gymnasium.py
@@ -25,7 +25,7 @@
 from gymnasium.utils.step_api_compatibility import (
     TerminatedTruncatedStepType as GymnasiumTimestep,
 )
-from helx.base.mdp import Timestep, TRANSITION, TERMINATION, TRUNCATION
+from helx.base.mdp import Timestep, StepType
 from helx.base.spaces import Continuous, Discrete, Space
 from .environment import EnvironmentWrapper
 
@@ -59,11 +59,11 @@ def timestep_from_gym(gym_step: GymnasiumTimestep, action: Array, t: Array) -> T
     obs, reward, terminated, truncated, _ = gym_step
 
     if terminated:
-        step_type = TERMINATION
+        step_type = StepType.TERMINATION
     elif truncated:
-        step_type = TRUNCATION
+        step_type = StepType.TRUNCATION
     else:
-        step_type = TRANSITION
+        step_type = StepType.TRANSITION
 
     obs = jnp.asarray(obs)
     reward = jnp.asarray(reward)
@@ -80,6 +80,7 @@ def timestep_from_gym(gym_step: GymnasiumTimestep, action: Array, t: Array) -> T
 
 class GymnasiumWrapper(EnvironmentWrapper):
     """Static class to convert between gymnasium and helx environments."""
+
     env: gymnasium.Env
 
     @classmethod
@@ -96,7 +97,7 @@ def wraps(cls, env: gymnasium.Env) -> GymnasiumWrapper:
 
     def reset(self, seed: int | None = None) -> Timestep:
         timestep = self.env.reset(seed=seed)
-        return timestep_from_gym(timestep, action=jnp.asarray(-1), t=jnp.asarray(0))
+        return timestep_from_gym(timestep, action=jnp.asarray(-1), t=jnp.asarray(0))  # type: ignore
 
     def _step(self, key: KeyArray, timestep: Timestep, action: Array) -> Timestep:
         next_step = self.env.step(np.asarray(action))
diff --git a/helx/envs/gymnax.py b/helx/envs/gymnax.py
index d99524e..ef272d4 100644
--- a/helx/envs/gymnax.py
+++ b/helx/envs/gymnax.py
@@ -25,7 +25,7 @@
 from jax.random import KeyArray
 
 from helx.base.spaces import Space, Continuous
-from helx.base.mdp import Timestep, TRANSITION, TERMINATION, TRUNCATION
+from helx.base.mdp import Timestep, StepType
 
 from .environment import EnvironmentWrapper
 from .gym import to_helx as gym_to_helx
@@ -42,7 +42,7 @@ def timestep_from_gym(
     return Timestep(
         observation=jnp.asarray(obs),
         reward=jnp.asarray(reward),
-        step_type=(TRANSITION, TERMINATION)[done],
+        step_type=(StepType.TRANSITION, StepType.TERMINATION)[done],
         action=jnp.asarray(action),
         t=t,
         state=state,
@@ -72,7 +72,7 @@ def reset(self, key: KeyArray) -> Timestep:
             t=jnp.asarray(0),
             observation=jnp.asarray(obs),
             reward=jnp.asarray(0.0),
-            step_type=TRANSITION,
+            step_type=StepType.TRANSITION,
             action=jnp.asarray(-1),
             state=state,
         )
@@ -87,9 +87,9 @@ def _step(self, key: KeyArray, timestep: Timestep, action: jax.Array) -> Timeste
         step_type = jax.lax.switch(
             idx,
             (
-                lambda: TRANSITION,
-                lambda: TRUNCATION,
-                lambda: TERMINATION,
+                lambda: StepType.TRANSITION,
+                lambda: StepType.TRUNCATION,
+                lambda: StepType.TERMINATION,
             ),
         )
         return Timestep(
diff --git a/helx/envs/navix.py b/helx/envs/navix.py
index f8d27c1..1021e45 100644
--- a/helx/envs/navix.py
+++ b/helx/envs/navix.py
@@ -20,7 +20,7 @@
 from jax.random import KeyArray
 
 from helx.base.spaces import Continuous, Discrete, Space
-from helx.base.mdp import TRANSITION, Timestep
+from helx.base.mdp import StepType, Timestep
 from .environment import EnvironmentWrapper
 
 
@@ -73,7 +73,7 @@ def reset(self, key: KeyArray) -> Timestep:
             t=jnp.asarray(0),
             observation=timestep.observation,
             reward=timestep.reward,
-            step_type=TRANSITION,
+            step_type=StepType.TRANSITION,
             action=jnp.asarray(-1),
             state=timestep.state,
             info=timestep.info
diff --git a/helx/experiment/logging.py b/helx/experiment/logging.py
index 8c2a522..37d5e55 100644
--- a/helx/experiment/logging.py
+++ b/helx/experiment/logging.py
@@ -10,7 +10,7 @@
 import flax.linen as nn
 
 from helx.agents import Log
-from helx.base.mdp import TRANSITION
+from helx.base.mdp import StepType
 
 
 T = TypeVar("T", bound=nn.Module)
@@ -40,7 +40,7 @@ def log_wandb(logs: Log) -> Log:
         if k == "returns":
             if not "step_type" in log_dict:
                 raise ValueError("Log must have step_type to log returns")
-            if log_dict["step_type"] == TRANSITION:
+            if log_dict["step_type"] == StepType.TRANSITION:
                 continue
         wandb.log({k: v}, commit=False)
     wandb.log({})  # commit flush
diff --git a/helx/experiment/running.py b/helx/experiment/running.py
index b18c98d..fb9c7a2 100644
--- a/helx/experiment/running.py
+++ b/helx/experiment/running.py
@@ -17,7 +17,7 @@
 import jax.numpy as jnp
 import wandb
 
-from helx.base.mdp import Timestep, TRANSITION
+from helx.base.mdp import Timestep, StepType
 from helx.agents import Agent, AgentState
 from helx.envs.environment import Environment
 
@@ -35,7 +35,7 @@ def run_episode(
     key, k1 = jax.random.split(key)
     timestep = env.reset(k1)
     timesteps = [timestep]
-    while timestep.step_type == TRANSITION:
+    while timestep.step_type == StepType.TRANSITION:
         key, k1, k2 = jax.random.split(key, 3)
         action = agent.sample_action(
             agent_state, timestep.observation, key=k1, eval=eval