diff --git a/src/primaite/agents/agent.py b/src/primaite/agents/agent.py
index 1f06a371..90860f7d 100644
--- a/src/primaite/agents/agent.py
+++ b/src/primaite/agents/agent.py
@@ -5,7 +5,7 @@ import time
 from abc import ABC, abstractmethod
 from datetime import datetime
 from pathlib import Path
-from typing import Dict, Final, Union
+from typing import Any, Dict, Final, TYPE_CHECKING, Union
 from uuid import uuid4
 
 import yaml
@@ -17,7 +17,13 @@ from primaite.config.training_config import TrainingConfig
 from primaite.data_viz.session_plots import plot_av_reward_per_episode
 from primaite.environment.primaite_env import Primaite
 
-_LOGGER = getLogger(__name__)
+if TYPE_CHECKING:
+    from logging import Logger
+
+    import numpy as np
+
+
+_LOGGER: "Logger" = getLogger(__name__)
 
 
 def get_session_path(session_timestamp: datetime) -> Path:
@@ -47,7 +53,7 @@ class AgentSessionABC(ABC):
     """
 
     @abstractmethod
-    def __init__(self, training_config_path, lay_down_config_path):
+    def __init__(self, training_config_path: Union[str, Path], lay_down_config_path: Union[str, Path]) -> None:
         """
         Initialise an agent session from config files.
 
@@ -107,11 +113,11 @@ class AgentSessionABC(ABC):
         return path
 
     @property
-    def uuid(self):
+    def uuid(self) -> str:
         """The Agent Session UUID."""
         return self._uuid
 
-    def _write_session_metadata_file(self):
+    def _write_session_metadata_file(self) -> None:
         """
         Write the ``session_metadata.json`` file.
 
@@ -147,7 +153,7 @@ class AgentSessionABC(ABC):
             json.dump(metadata_dict, file)
             _LOGGER.debug("Finished writing session metadata file")
 
-    def _update_session_metadata_file(self):
+    def _update_session_metadata_file(self) -> None:
         """
         Update the ``session_metadata.json`` file.
 
@@ -176,7 +182,7 @@ class AgentSessionABC(ABC):
             _LOGGER.debug("Finished updating session metadata file")
 
     @abstractmethod
-    def _setup(self):
+    def _setup(self) -> None:
         _LOGGER.info(
             "Welcome to the Primary-level AI Training Environment " f"(PrimAITE) (version: {primaite.__version__})"
         )
@@ -186,14 +192,14 @@ class AgentSessionABC(ABC):
         self._can_evaluate = False
 
     @abstractmethod
-    def _save_checkpoint(self):
+    def _save_checkpoint(self) -> None:
         pass
 
     @abstractmethod
     def learn(
         self,
-        **kwargs,
-    ):
+        **kwargs: Any,
+    ) -> None:
         """
         Train the agent.
 
@@ -210,8 +216,8 @@ class AgentSessionABC(ABC):
     @abstractmethod
     def evaluate(
         self,
-        **kwargs,
-    ):
+        **kwargs: Any,
+    ) -> None:
         """
         Evaluate the agent.
 
@@ -224,7 +230,7 @@ class AgentSessionABC(ABC):
             _LOGGER.info("Finished evaluation")
 
     @abstractmethod
-    def _get_latest_checkpoint(self):
+    def _get_latest_checkpoint(self) -> None:
         pass
 
     @classmethod
@@ -264,7 +270,6 @@ class AgentSessionABC(ABC):
             msg = f"Failed to load PrimAITE Session, path does not exist: {path}"
             _LOGGER.error(msg)
             raise FileNotFoundError(msg)
-        pass
 
     @property
     def _saved_agent_path(self) -> Path:
@@ -276,21 +281,21 @@ class AgentSessionABC(ABC):
         return self.learning_path / file_name
 
     @abstractmethod
-    def save(self):
+    def save(self) -> None:
         """Save the agent."""
         pass
 
     @abstractmethod
-    def export(self):
+    def export(self) -> None:
         """Export the agent to transportable file format."""
         pass
 
-    def close(self):
+    def close(self) -> None:
         """Closes the agent."""
         self._env.episode_av_reward_writer.close()  # noqa
         self._env.transaction_writer.close()  # noqa
 
-    def _plot_av_reward_per_episode(self, learning_session: bool = True):
+    def _plot_av_reward_per_episode(self, learning_session: bool = True) -> None:
         # self.close()
         title = f"PrimAITE Session {self.timestamp_str} "
         subtitle = str(self._training_config)
@@ -318,7 +323,7 @@ class HardCodedAgentSessionABC(AgentSessionABC):
     implemented.
     """
 
-    def __init__(self, training_config_path, lay_down_config_path):
+    def __init__(self, training_config_path: Union[str, Path], lay_down_config_path: Union[str, Path]) -> None:
         """
         Initialise a hardcoded agent session.
 
@@ -331,7 +336,7 @@ class HardCodedAgentSessionABC(AgentSessionABC):
         super().__init__(training_config_path, lay_down_config_path)
         self._setup()
 
-    def _setup(self):
+    def _setup(self) -> None:
         self._env: Primaite = Primaite(
             training_config_path=self._training_config_path,
             lay_down_config_path=self._lay_down_config_path,
@@ -342,16 +347,16 @@ class HardCodedAgentSessionABC(AgentSessionABC):
         self._can_learn = False
         self._can_evaluate = True
 
-    def _save_checkpoint(self):
+    def _save_checkpoint(self) -> None:
         pass
 
-    def _get_latest_checkpoint(self):
+    def _get_latest_checkpoint(self) -> None:
         pass
 
     def learn(
         self,
-        **kwargs,
-    ):
+        **kwargs: Any,
+    ) -> None:
         """
         Train the agent.
 
@@ -360,13 +365,13 @@ class HardCodedAgentSessionABC(AgentSessionABC):
         _LOGGER.warning("Deterministic agents cannot learn")
 
     @abstractmethod
-    def _calculate_action(self, obs):
+    def _calculate_action(self, obs: np.ndarray) -> None:
         pass
 
     def evaluate(
         self,
-        **kwargs,
-    ):
+        **kwargs: Any,
+    ) -> None:
         """
         Evaluate the agent.
 
@@ -398,14 +403,14 @@ class HardCodedAgentSessionABC(AgentSessionABC):
         super().evaluate()
 
     @classmethod
-    def load(cls):
+    def load(cls) -> None:
         """Load an agent from file."""
         _LOGGER.warning("Deterministic agents cannot be loaded")
 
-    def save(self):
+    def save(self) -> None:
         """Save the agent."""
         _LOGGER.warning("Deterministic agents cannot be saved")
 
-    def export(self):
+    def export(self) -> None:
         """Export the agent to transportable file format."""
         _LOGGER.warning("Deterministic agents cannot be exported")
diff --git a/src/primaite/agents/hardcoded_acl.py b/src/primaite/agents/hardcoded_acl.py
index 166ff415..98c1d7d9 100644
--- a/src/primaite/agents/hardcoded_acl.py
+++ b/src/primaite/agents/hardcoded_acl.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, List, Union
+from typing import Dict, List, Union
 
 import numpy as np
 
@@ -32,7 +32,7 @@ class HardCodedACLAgent(HardCodedAgentSessionABC):
 
     def get_blocked_green_iers(
         self, green_iers: Dict[str, IER], acl: AccessControlList, nodes: Dict[str, NodeUnion]
-    ) -> Dict[Any, Any]:
+    ) -> Dict[str, IER]:
         """Get blocked green IERs.
 
         :param green_iers: Green IERs to check for being
@@ -60,7 +60,9 @@ class HardCodedACLAgent(HardCodedAgentSessionABC):
 
         return blocked_green_iers
 
-    def get_matching_acl_rules_for_ier(self, ier: IER, acl: AccessControlList, nodes: Dict[str, NodeUnion]):
+    def get_matching_acl_rules_for_ier(
+        self, ier: IER, acl: AccessControlList, nodes: Dict[str, NodeUnion]
+    ) -> Dict[int, ACLRule]:
         """Get list of ACL rules which are relevant to an IER.
 
         :param ier: Information Exchange Request to query against the ACL list
@@ -83,7 +85,7 @@ class HardCodedACLAgent(HardCodedAgentSessionABC):
 
     def get_blocking_acl_rules_for_ier(
         self, ier: IER, acl: AccessControlList, nodes: Dict[str, NodeUnion]
-    ) -> Dict[str, Any]:
+    ) -> Dict[int, ACLRule]:
         """
         Get blocking ACL rules for an IER.
 
@@ -111,7 +113,7 @@ class HardCodedACLAgent(HardCodedAgentSessionABC):
 
     def get_allow_acl_rules_for_ier(
         self, ier: IER, acl: AccessControlList, nodes: Dict[str, NodeUnion]
-    ) -> Dict[str, Any]:
+    ) -> Dict[int, ACLRule]:
         """Get all allowing ACL rules for an IER.
 
         :param ier: Information Exchange Request to query against the ACL list
@@ -141,7 +143,7 @@ class HardCodedACLAgent(HardCodedAgentSessionABC):
         acl: AccessControlList,
         nodes: Dict[str, Union[ServiceNode, ActiveNode]],
         services_list: List[str],
-    ) -> Dict[str, ACLRule]:
+    ) -> Dict[int, ACLRule]:
         """Filter ACL rules to only those which are relevant to the specified nodes.
 
         :param source_node_id: Source node
@@ -186,7 +188,7 @@ class HardCodedACLAgent(HardCodedAgentSessionABC):
         acl: AccessControlList,
         nodes: Dict[str, NodeUnion],
         services_list: List[str],
-    ) -> Dict[str, ACLRule]:
+    ) -> Dict[int, ACLRule]:
         """List ALLOW rules relating to specified nodes.
 
         :param source_node_id: Source node id
@@ -233,7 +235,7 @@ class HardCodedACLAgent(HardCodedAgentSessionABC):
         acl: AccessControlList,
         nodes: Dict[str, NodeUnion],
         services_list: List[str],
-    ) -> Dict[str, ACLRule]:
+    ) -> Dict[int, ACLRule]:
         """List DENY rules relating to specified nodes.
 
         :param source_node_id: Source node id
diff --git a/src/primaite/agents/rllib.py b/src/primaite/agents/rllib.py
index 6253f574..6674a8df 100644
--- a/src/primaite/agents/rllib.py
+++ b/src/primaite/agents/rllib.py
@@ -4,7 +4,7 @@ import json
 import shutil
 from datetime import datetime
 from pathlib import Path
-from typing import Union
+from typing import Any, Callable, Dict, TYPE_CHECKING, Union
 from uuid import uuid4
 
 from ray.rllib.algorithms import Algorithm
@@ -18,10 +18,14 @@ from primaite.agents.agent import AgentSessionABC
 from primaite.common.enums import AgentFramework, AgentIdentifier
 from primaite.environment.primaite_env import Primaite
 
-_LOGGER = getLogger(__name__)
+if TYPE_CHECKING:
+    from logging import Logger
+
+_LOGGER: "Logger" = getLogger(__name__)
 
 
-def _env_creator(env_config):
+# TODO: verify type of env_config
+def _env_creator(env_config: Dict[str, Any]) -> Primaite:
     return Primaite(
         training_config_path=env_config["training_config_path"],
         lay_down_config_path=env_config["lay_down_config_path"],
@@ -30,11 +34,12 @@ def _env_creator(env_config):
     )
 
 
-def _custom_log_creator(session_path: Path):
+# TODO: verify type hint return type
+def _custom_log_creator(session_path: Path) -> Callable[[Dict], UnifiedLogger]:
     logdir = session_path / "ray_results"
     logdir.mkdir(parents=True, exist_ok=True)
 
-    def logger_creator(config):
+    def logger_creator(config: Dict) -> UnifiedLogger:
         return UnifiedLogger(config, logdir, loggers=None)
 
     return logger_creator
@@ -43,7 +48,7 @@ def _custom_log_creator(session_path: Path):
 class RLlibAgent(AgentSessionABC):
     """An AgentSession class that implements a Ray RLlib agent."""
 
-    def __init__(self, training_config_path, lay_down_config_path):
+    def __init__(self, training_config_path: Union[str, Path], lay_down_config_path: Union[str, Path]) -> None:
         """
         Initialise the RLLib Agent training session.
 
@@ -82,7 +87,7 @@ class RLlibAgent(AgentSessionABC):
             f"{self._training_config.deep_learning_framework}"
         )
 
-    def _update_session_metadata_file(self):
+    def _update_session_metadata_file(self) -> None:
         """
         Update the ``session_metadata.json`` file.
 
@@ -110,7 +115,7 @@ class RLlibAgent(AgentSessionABC):
             json.dump(metadata_dict, file)
             _LOGGER.debug("Finished updating session metadata file")
 
-    def _setup(self):
+    def _setup(self) -> None:
         super()._setup()
         register_env("primaite", _env_creator)
         self._agent_config = self._agent_config_class()
@@ -147,8 +152,8 @@ class RLlibAgent(AgentSessionABC):
 
     def learn(
         self,
-        **kwargs,
-    ):
+        **kwargs: Any,
+    ) -> None:
         """
         Evaluate the agent.
 
@@ -168,8 +173,8 @@ class RLlibAgent(AgentSessionABC):
 
     def evaluate(
         self,
-        **kwargs,
-    ):
+        **kwargs: None,
+    ) -> None:
         """
         Evaluate the agent.
 
@@ -177,7 +182,7 @@ class RLlibAgent(AgentSessionABC):
         """
         raise NotImplementedError
 
-    def _get_latest_checkpoint(self):
+    def _get_latest_checkpoint(self) -> None:
         raise NotImplementedError
 
     @classmethod
@@ -185,7 +190,7 @@ class RLlibAgent(AgentSessionABC):
         """Load an agent from file."""
         raise NotImplementedError
 
-    def save(self, overwrite_existing: bool = True):
+    def save(self, overwrite_existing: bool = True) -> None:
         """Save the agent."""
         # Make temp dir to save in isolation
         temp_dir = self.learning_path / str(uuid4())
@@ -205,6 +210,6 @@ class RLlibAgent(AgentSessionABC):
         # Drop the temp directory
         shutil.rmtree(temp_dir)
 
-    def export(self):
+    def export(self) -> None:
         """Export the agent to transportable file format."""
         raise NotImplementedError
diff --git a/src/primaite/agents/sb3.py b/src/primaite/agents/sb3.py
index cb00985a..5f04acc0 100644
--- a/src/primaite/agents/sb3.py
+++ b/src/primaite/agents/sb3.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from pathlib import Path
-from typing import Union
+from typing import Any, TYPE_CHECKING, Union
 
 import numpy as np
 from stable_baselines3 import A2C, PPO
@@ -12,13 +12,16 @@ from primaite.agents.agent import AgentSessionABC
 from primaite.common.enums import AgentFramework, AgentIdentifier
 from primaite.environment.primaite_env import Primaite
 
-_LOGGER = getLogger(__name__)
+if TYPE_CHECKING:
+    from logging import Logger
+
+_LOGGER: "Logger" = getLogger(__name__)
 
 
 class SB3Agent(AgentSessionABC):
     """An AgentSession class that implements a Stable Baselines3 agent."""
 
-    def __init__(self, training_config_path, lay_down_config_path):
+    def __init__(self, training_config_path: Union[str, Path], lay_down_config_path: Union[str, Path]) -> None:
         """
         Initialise the SB3 Agent training session.
 
@@ -57,7 +60,7 @@ class SB3Agent(AgentSessionABC):
 
         self.is_eval = False
 
-    def _setup(self):
+    def _setup(self) -> None:
         super()._setup()
         self._env = Primaite(
             training_config_path=self._training_config_path,
@@ -75,7 +78,7 @@ class SB3Agent(AgentSessionABC):
             seed=self._training_config.seed,
         )
 
-    def _save_checkpoint(self):
+    def _save_checkpoint(self) -> None:
         checkpoint_n = self._training_config.checkpoint_every_n_episodes
         episode_count = self._env.episode_count
         save_checkpoint = False
@@ -86,13 +89,13 @@ class SB3Agent(AgentSessionABC):
             self._agent.save(checkpoint_path)
             _LOGGER.debug(f"Saved agent checkpoint: {checkpoint_path}")
 
-    def _get_latest_checkpoint(self):
+    def _get_latest_checkpoint(self) -> None:
         pass
 
     def learn(
         self,
-        **kwargs,
-    ):
+        **kwargs: Any,
+    ) -> None:
         """
         Train the agent.
 
@@ -115,8 +118,8 @@ class SB3Agent(AgentSessionABC):
 
     def evaluate(
         self,
-        **kwargs,
-    ):
+        **kwargs: Any,
+    ) -> None:
         """
         Evaluate the agent.
 
@@ -150,10 +153,10 @@ class SB3Agent(AgentSessionABC):
         """Load an agent from file."""
         raise NotImplementedError
 
-    def save(self):
+    def save(self) -> None:
         """Save the agent."""
         self._agent.save(self._saved_agent_path)
 
-    def export(self):
+    def export(self) -> None:
         """Export the agent to transportable file format."""
         raise NotImplementedError
diff --git a/src/primaite/agents/simple.py b/src/primaite/agents/simple.py
index b429a2f5..2c130c0c 100644
--- a/src/primaite/agents/simple.py
+++ b/src/primaite/agents/simple.py
@@ -1,6 +1,11 @@
+from typing import TYPE_CHECKING
+
 from primaite.agents.agent import HardCodedAgentSessionABC
 from primaite.agents.utils import get_new_action, transform_action_acl_enum, transform_action_node_enum
 
+if TYPE_CHECKING:
+    import numpy as np
+
 
 class RandomAgent(HardCodedAgentSessionABC):
     """
@@ -9,7 +14,7 @@ class RandomAgent(HardCodedAgentSessionABC):
     Get a completely random action from the action space.
     """
 
-    def _calculate_action(self, obs):
+    def _calculate_action(self, obs: "np.ndarray") -> int:
         return self._env.action_space.sample()
 
 
@@ -20,7 +25,7 @@ class DummyAgent(HardCodedAgentSessionABC):
     All action spaces setup so dummy action is always 0 regardless of action type used.
     """
 
-    def _calculate_action(self, obs):
+    def _calculate_action(self, obs: "np.ndarray") -> int:
         return 0
 
 
@@ -31,7 +36,7 @@ class DoNothingACLAgent(HardCodedAgentSessionABC):
     A valid ACL action that has no effect; does nothing.
     """
 
-    def _calculate_action(self, obs):
+    def _calculate_action(self, obs: "np.ndarray") -> int:
         nothing_action = ["NONE", "ALLOW", "ANY", "ANY", "ANY", "ANY"]
         nothing_action = transform_action_acl_enum(nothing_action)
         nothing_action = get_new_action(nothing_action, self._env.action_dict)
@@ -46,7 +51,7 @@ class DoNothingNodeAgent(HardCodedAgentSessionABC):
     A valid Node action that has no effect; does nothing.
     """
 
-    def _calculate_action(self, obs):
+    def _calculate_action(self, obs: "np.ndarray") -> int:
         nothing_action = [1, "NONE", "ON", 0]
         nothing_action = transform_action_node_enum(nothing_action)
         nothing_action = get_new_action(nothing_action, self._env.action_dict)
diff --git a/src/primaite/agents/utils.py b/src/primaite/agents/utils.py
index 8858fa6a..2e6b3f0c 100644
--- a/src/primaite/agents/utils.py
+++ b/src/primaite/agents/utils.py
@@ -38,7 +38,7 @@ def transform_action_node_readable(action: List[int]) -> List[Union[int, str]]:
     return new_action
 
 
-def transform_action_acl_readable(action: List[str]) -> List[Union[str, int]]:
+def transform_action_acl_readable(action: List[int]) -> List[Union[str, int]]:
     """
     Transform an ACL action to a more readable format.
 
diff --git a/src/primaite/common/custom_typing.py b/src/primaite/common/custom_typing.py
index 37b10efe..e01c8713 100644
--- a/src/primaite/common/custom_typing.py
+++ b/src/primaite/common/custom_typing.py
@@ -1,8 +1,8 @@
-from typing import Type, Union
+from typing import TypeVar
 
 from primaite.nodes.active_node import ActiveNode
 from primaite.nodes.passive_node import PassiveNode
 from primaite.nodes.service_node import ServiceNode
 
-NodeUnion: Type = Union[ActiveNode, PassiveNode, ServiceNode]
+NodeUnion = TypeVar("NodeUnion", ServiceNode, ActiveNode, PassiveNode)
 """A Union of ActiveNode, PassiveNode, and ServiceNode."""
diff --git a/src/primaite/common/protocol.py b/src/primaite/common/protocol.py
index ad6a1d83..f7a757e8 100644
--- a/src/primaite/common/protocol.py
+++ b/src/primaite/common/protocol.py
@@ -5,17 +5,17 @@
 class Protocol(object):
     """Protocol class."""
 
-    def __init__(self, _name):
+    def __init__(self, _name: str) -> None:
         """
         Initialise a protocol.
 
         :param _name: The name of the protocol
         :type _name: str
         """
-        self.name = _name
-        self.load = 0  # bps
+        self.name: str = _name
+        self.load: int = 0  # bps
 
-    def get_name(self):
+    def get_name(self) -> str:
         """
         Gets the protocol name.
 
@@ -24,7 +24,7 @@ class Protocol(object):
         """
         return self.name
 
-    def get_load(self):
+    def get_load(self) -> int:
         """
         Gets the protocol load.
 
@@ -33,7 +33,7 @@ class Protocol(object):
         """
         return self.load
 
-    def add_load(self, _load):
+    def add_load(self, _load: int) -> None:
         """
         Adds load to the protocol.
 
@@ -42,6 +42,6 @@ class Protocol(object):
         """
         self.load += _load
 
-    def clear_load(self):
+    def clear_load(self) -> None:
         """Clears the load on this protocol."""
         self.load = 0
diff --git a/src/primaite/common/service.py b/src/primaite/common/service.py
index 258ac8f9..f3dddcc7 100644
--- a/src/primaite/common/service.py
+++ b/src/primaite/common/service.py
@@ -15,12 +15,12 @@ class Service(object):
         :param port: The service port.
         :param software_state: The service SoftwareState.
         """
-        self.name = name
-        self.port = port
-        self.software_state = software_state
-        self.patching_count = 0
+        self.name: str = name
+        self.port: str = port
+        self.software_state: SoftwareState = software_state
+        self.patching_count: int = 0
 
-    def reduce_patching_count(self):
+    def reduce_patching_count(self) -> None:
         """Reduces the patching count for the service."""
         self.patching_count -= 1
         if self.patching_count <= 0:
diff --git a/src/primaite/config/lay_down_config.py b/src/primaite/config/lay_down_config.py
index 3a85b9da..2cc5f9c2 100644
--- a/src/primaite/config/lay_down_config.py
+++ b/src/primaite/config/lay_down_config.py
@@ -1,12 +1,15 @@
 # Crown Copyright (C) Dstl 2022. DEFCON 703. Shared in confidence.
 from pathlib import Path
-from typing import Any, Dict, Final, Union
+from typing import Any, Dict, Final, TYPE_CHECKING, Union
 
 import yaml
 
 from primaite import getLogger, USERS_CONFIG_DIR
 
-_LOGGER = getLogger(__name__)
+if TYPE_CHECKING:
+    from logging import Logger
+
+_LOGGER: "Logger" = getLogger(__name__)
 
 _EXAMPLE_LAY_DOWN: Final[Path] = USERS_CONFIG_DIR / "example_config" / "lay_down"
 
diff --git a/src/primaite/config/training_config.py b/src/primaite/config/training_config.py
index 785d9757..5cf62174 100644
--- a/src/primaite/config/training_config.py
+++ b/src/primaite/config/training_config.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Any, Dict, Final, Optional, Union
+from typing import Any, Dict, Final, Optional, TYPE_CHECKING, Union
 
 import yaml
 
@@ -18,7 +18,10 @@ from primaite.common.enums import (
     SessionType,
 )
 
-_LOGGER = getLogger(__name__)
+if TYPE_CHECKING:
+    from logging import Logger
+
+_LOGGER: Logger = getLogger(__name__)
 
 _EXAMPLE_TRAINING: Final[Path] = USERS_CONFIG_DIR / "example_config" / "training"
 
diff --git a/src/primaite/environment/observations.py b/src/primaite/environment/observations.py
index 53c173fd..cb9872d1 100644
--- a/src/primaite/environment/observations.py
+++ b/src/primaite/environment/observations.py
@@ -14,17 +14,19 @@ from primaite.nodes.service_node import ServiceNode
 # TYPE_CHECKING is False at runtime and True when typecheckers are performing typechecking
 # Therefore, this avoids circular dependency problem.
 if TYPE_CHECKING:
+    from logging import Logger
+
     from primaite.environment.primaite_env import Primaite
 
 
-_LOGGER = logging.getLogger(__name__)
+_LOGGER: "Logger" = logging.getLogger(__name__)
 
 
 class AbstractObservationComponent(ABC):
     """Represents a part of the PrimAITE observation space."""
 
     @abstractmethod
-    def __init__(self, env: "Primaite"):
+    def __init__(self, env: "Primaite") -> None:
         """
         Initialise observation component.
 
@@ -39,7 +41,7 @@ class AbstractObservationComponent(ABC):
         return NotImplemented
 
     @abstractmethod
-    def update(self):
+    def update(self) -> None:
         """Update the observation based on the current state of the environment."""
         self.current_observation = NotImplemented
 
@@ -74,7 +76,7 @@ class NodeLinkTable(AbstractObservationComponent):
     _MAX_VAL: int = 1_000_000_000
     _DATA_TYPE: type = np.int64
 
-    def __init__(self, env: "Primaite"):
+    def __init__(self, env: "Primaite") -> None:
         """
         Initialise a NodeLinkTable observation space component.
 
@@ -101,7 +103,7 @@ class NodeLinkTable(AbstractObservationComponent):
 
         self.structure = self.generate_structure()
 
-    def update(self):
+    def update(self) -> None:
         """
         Update the observation based on current environment state.
 
@@ -148,7 +150,7 @@ class NodeLinkTable(AbstractObservationComponent):
                 protocol_index += 1
             item_index += 1
 
-    def generate_structure(self):
+    def generate_structure(self) -> List[str]:
         """Return a list of labels for the components of the flattened observation space."""
         nodes = self.env.nodes.values()
         links = self.env.links.values()
@@ -211,7 +213,7 @@ class NodeStatuses(AbstractObservationComponent):
 
     _DATA_TYPE: type = np.int64
 
-    def __init__(self, env: "Primaite"):
+    def __init__(self, env: "Primaite") -> None:
         """
         Initialise a NodeStatuses observation component.
 
@@ -237,7 +239,7 @@ class NodeStatuses(AbstractObservationComponent):
         self.current_observation = np.zeros(len(shape), dtype=self._DATA_TYPE)
         self.structure = self.generate_structure()
 
-    def update(self):
+    def update(self) -> None:
         """
         Update the observation based on current environment state.
 
@@ -268,7 +270,7 @@ class NodeStatuses(AbstractObservationComponent):
             )
         self.current_observation[:] = obs
 
-    def generate_structure(self):
+    def generate_structure(self) -> List[str]:
         """Return a list of labels for the components of the flattened observation space."""
         services = self.env.services_list
 
@@ -317,7 +319,7 @@ class LinkTrafficLevels(AbstractObservationComponent):
         env: "Primaite",
         combine_service_traffic: bool = False,
         quantisation_levels: int = 5,
-    ):
+    ) -> None:
         """
         Initialise a LinkTrafficLevels observation component.
 
@@ -359,7 +361,7 @@ class LinkTrafficLevels(AbstractObservationComponent):
 
         self.structure = self.generate_structure()
 
-    def update(self):
+    def update(self) -> None:
         """
         Update the observation based on current environment state.
 
@@ -385,7 +387,7 @@ class LinkTrafficLevels(AbstractObservationComponent):
 
         self.current_observation[:] = obs
 
-    def generate_structure(self):
+    def generate_structure(self) -> List[str]:
         """Return a list of labels for the components of the flattened observation space."""
         structure = []
         for _, link in self.env.links.items():
@@ -415,7 +417,7 @@ class ObservationsHandler:
         "LINK_TRAFFIC_LEVELS": LinkTrafficLevels,
     }
 
-    def __init__(self):
+    def __init__(self) -> None:
         """Initialise the observation handler."""
         self.registered_obs_components: List[AbstractObservationComponent] = []
 
@@ -430,7 +432,7 @@ class ObservationsHandler:
 
         self.flatten: bool = False
 
-    def update_obs(self):
+    def update_obs(self) -> None:
         """Fetch fresh information about the environment."""
         current_obs = []
         for obs in self.registered_obs_components:
@@ -443,7 +445,7 @@ class ObservationsHandler:
             self._observation = tuple(current_obs)
         self._flat_observation = spaces.flatten(self._space, self._observation)
 
-    def register(self, obs_component: AbstractObservationComponent):
+    def register(self, obs_component: AbstractObservationComponent) -> None:
         """
         Add a component for this handler to track.
 
@@ -453,7 +455,7 @@ class ObservationsHandler:
         self.registered_obs_components.append(obs_component)
         self.update_space()
 
-    def deregister(self, obs_component: AbstractObservationComponent):
+    def deregister(self, obs_component: AbstractObservationComponent) -> None:
         """
         Remove a component from this handler.
 
@@ -464,7 +466,7 @@ class ObservationsHandler:
         self.registered_obs_components.remove(obs_component)
         self.update_space()
 
-    def update_space(self):
+    def update_space(self) -> None:
         """Rebuild the handler's composite observation space from its components."""
         component_spaces = []
         for obs_comp in self.registered_obs_components:
@@ -481,7 +483,7 @@ class ObservationsHandler:
             self._flat_space = spaces.Box(0, 1, (0,))
 
     @property
-    def space(self):
+    def space(self) -> spaces.Space:
         """Observation space, return the flattened version if flatten is True."""
         if self.flatten:
             return self._flat_space
@@ -489,7 +491,7 @@ class ObservationsHandler:
             return self._space
 
     @property
-    def current_observation(self):
+    def current_observation(self) -> Union[np.ndarray, Tuple[np.ndarray]]:
         """Current observation, return the flattened version if flatten is True."""
         if self.flatten:
             return self._flat_observation
@@ -497,7 +499,7 @@ class ObservationsHandler:
             return self._observation
 
     @classmethod
-    def from_config(cls, env: "Primaite", obs_space_config: dict):
+    def from_config(cls, env: "Primaite", obs_space_config: dict) -> "ObservationsHandler":
         """
         Parse a config dictinary, return a new observation handler populated with new observation component objects.
 
@@ -543,7 +545,7 @@ class ObservationsHandler:
         handler.update_obs()
         return handler
 
-    def describe_structure(self):
+    def describe_structure(self) -> List[str]:
         """
         Create a list of names for the features of the obs space.
 
diff --git a/src/primaite/environment/primaite_env.py b/src/primaite/environment/primaite_env.py
index b92c434e..5bf843f1 100644
--- a/src/primaite/environment/primaite_env.py
+++ b/src/primaite/environment/primaite_env.py
@@ -5,7 +5,7 @@ import logging
 import uuid as uuid
 from pathlib import Path
 from random import choice, randint, sample, uniform
-from typing import Dict, Final, Tuple, Union
+from typing import Dict, Final, List, Tuple, TYPE_CHECKING, Union
 
 import networkx as nx
 import numpy as np
@@ -20,6 +20,7 @@ from primaite.common.custom_typing import NodeUnion
 from primaite.common.enums import (
     ActionType,
     AgentFramework,
+    AgentIdentifier,
     FileSystemState,
     HardwareState,
     NodePOLInitiator,
@@ -48,7 +49,10 @@ from primaite.pol.red_agent_pol import apply_red_agent_iers, apply_red_agent_nod
 from primaite.transactions.transaction import Transaction
 from primaite.utils.session_output_writer import SessionOutputWriter
 
-_LOGGER = getLogger(__name__)
+if TYPE_CHECKING:
+    from logging import Logger
+
+_LOGGER: "Logger" = getLogger(__name__)
 
 
 class Primaite(Env):
@@ -66,7 +70,7 @@ class Primaite(Env):
         lay_down_config_path: Union[str, Path],
         session_path: Path,
         timestamp_str: str,
-    ):
+    ) -> None:
         """
         The Primaite constructor.
 
@@ -77,13 +81,14 @@ class Primaite(Env):
         """
         self.session_path: Final[Path] = session_path
         self.timestamp_str: Final[str] = timestamp_str
-        self._training_config_path = training_config_path
-        self._lay_down_config_path = lay_down_config_path
+        self._training_config_path: Union[str, Path] = training_config_path
+        self._lay_down_config_path: Union[str, Path] = lay_down_config_path
 
         self.training_config: TrainingConfig = training_config.load(training_config_path)
         _LOGGER.info(f"Using: {str(self.training_config)}")
 
         # Number of steps in an episode
+        self.episode_steps: int
         if self.training_config.session_type == SessionType.TRAIN:
             self.episode_steps = self.training_config.num_train_steps
         elif self.training_config.session_type == SessionType.EVAL:
@@ -94,7 +99,7 @@ class Primaite(Env):
         super(Primaite, self).__init__()
 
         # The agent in use
-        self.agent_identifier = self.training_config.agent_identifier
+        self.agent_identifier: AgentIdentifier = self.training_config.agent_identifier
 
         # Create a dictionary to hold all the nodes
         self.nodes: Dict[str, NodeUnion] = {}
@@ -113,36 +118,38 @@ class Primaite(Env):
         self.green_iers_reference: Dict[str, IER] = {}
 
         # Create a dictionary to hold all the node PoLs (this will come from an external source)
+        # TODO: figure out type
         self.node_pol = {}
 
         # Create a dictionary to hold all the red agent IERs (this will come from an external source)
-        self.red_iers = {}
+        self.red_iers: Dict[str, IER] = {}
 
         # Create a dictionary to hold all the red agent node PoLs (this will come from an external source)
-        self.red_node_pol = {}
+        self.red_node_pol: Dict[str, NodeStateInstructionRed] = {}
 
         # Create the Access Control List
-        self.acl = AccessControlList()
+        self.acl: AccessControlList = AccessControlList()
 
         # Create a list of services (enums)
-        self.services_list = []
+        self.services_list: List[str] = []
 
         # Create a list of ports
-        self.ports_list = []
+        self.ports_list: List[str] = []
 
         # Create graph (network)
-        self.network = nx.MultiGraph()
+        self.network: nx.Graph = nx.MultiGraph()
 
         # Create a graph (network) reference
-        self.network_reference = nx.MultiGraph()
+        self.network_reference: nx.Graph = nx.MultiGraph()
 
         # Create step count
-        self.step_count = 0
+        self.step_count: int = 0
 
         self.total_step_count: int = 0
         """The total number of time steps completed."""
 
         # Create step info dictionary
+        # TODO: figure out type
         self.step_info = {}
 
         # Total reward
@@ -152,22 +159,23 @@ class Primaite(Env):
         self.average_reward: float = 0
 
         # Episode count
-        self.episode_count = 0
+        self.episode_count: int = 0
 
         # Number of nodes - gets a value by examining the nodes dictionary after it's been populated
-        self.num_nodes = 0
+        self.num_nodes: int = 0
 
         # Number of links - gets a value by examining the links dictionary after it's been populated
-        self.num_links = 0
+        self.num_links: int = 0
 
         # Number of services - gets a value when config is loaded
-        self.num_services = 0
+        self.num_services: int = 0
 
         # Number of ports - gets a value when config is loaded
-        self.num_ports = 0
+        self.num_ports: int = 0
 
         # The action type
-        self.action_type = 0
+        # TODO: confirm type
+        self.action_type: int = 0
 
         # TODO fix up with TrainingConfig
         # stores the observation config from the yaml, default is NODE_LINK_TABLE
@@ -179,7 +187,7 @@ class Primaite(Env):
         # It will be initialised later.
         self.obs_handler: ObservationsHandler
 
-        self._obs_space_description = None
+        self._obs_space_description: List[str] = None
         "The env observation space description for transactions writing"
 
         # Open the config file and build the environment laydown
@@ -211,9 +219,13 @@ class Primaite(Env):
             _LOGGER.error("Could not save network diagram", exc_info=True)
 
         # Initiate observation space
+        self.observation_space: spaces.Space
+        self.env_obs: np.ndarray
         self.observation_space, self.env_obs = self.init_observations()
 
         # Define Action Space - depends on action space type (Node or ACL)
+        self.action_dict: Dict[int, List[int]]
+        self.action_space: spaces.Space
         if self.training_config.action_type == ActionType.NODE:
             _LOGGER.debug("Action space type NODE selected")
             # Terms (for node action space):
@@ -241,8 +253,12 @@ class Primaite(Env):
         else:
             _LOGGER.error(f"Invalid action type selected: {self.training_config.action_type}")
 
-        self.episode_av_reward_writer = SessionOutputWriter(self, transaction_writer=False, learning_session=True)
-        self.transaction_writer = SessionOutputWriter(self, transaction_writer=True, learning_session=True)
+        self.episode_av_reward_writer: SessionOutputWriter = SessionOutputWriter(
+            self, transaction_writer=False, learning_session=True
+        )
+        self.transaction_writer: SessionOutputWriter = SessionOutputWriter(
+            self, transaction_writer=True, learning_session=True
+        )
 
     @property
     def actual_episode_count(self) -> int:
@@ -251,7 +267,7 @@ class Primaite(Env):
             return self.episode_count - 1
         return self.episode_count
 
-    def set_as_eval(self):
+    def set_as_eval(self) -> None:
         """Set the writers to write to eval directories."""
         self.episode_av_reward_writer = SessionOutputWriter(self, transaction_writer=False, learning_session=False)
         self.transaction_writer = SessionOutputWriter(self, transaction_writer=True, learning_session=False)
@@ -260,12 +276,12 @@ class Primaite(Env):
         self.total_step_count = 0
         self.episode_steps = self.training_config.num_eval_steps
 
-    def _write_av_reward_per_episode(self):
+    def _write_av_reward_per_episode(self) -> None:
         if self.actual_episode_count > 0:
             csv_data = self.actual_episode_count, self.average_reward
             self.episode_av_reward_writer.write(csv_data)
 
-    def reset(self):
+    def reset(self) -> np.ndarray:
         """
         AI Gym Reset function.
 
@@ -299,7 +315,7 @@ class Primaite(Env):
 
         return self.env_obs
 
-    def step(self, action):
+    def step(self, action: int) -> tuple(np.ndarray, float, bool, Dict):
         """
         AI Gym Step function.
 
@@ -418,7 +434,7 @@ class Primaite(Env):
         # Return
         return self.env_obs, reward, done, self.step_info
 
-    def close(self):
+    def close(self) -> None:
         """Override parent close and close writers."""
         # Close files if last episode/step
         # if self.can_finish:
@@ -427,18 +443,18 @@ class Primaite(Env):
         self.transaction_writer.close()
         self.episode_av_reward_writer.close()
 
-    def init_acl(self):
+    def init_acl(self) -> None:
         """Initialise the Access Control List."""
         self.acl.remove_all_rules()
 
-    def output_link_status(self):
+    def output_link_status(self) -> None:
         """Output the link status of all links to the console."""
         for link_key, link_value in self.links.items():
             _LOGGER.debug("Link ID: " + link_value.get_id())
             for protocol in link_value.protocol_list:
                 print("    Protocol: " + protocol.get_name().name + ", Load: " + str(protocol.get_load()))
 
-    def interpret_action_and_apply(self, _action):
+    def interpret_action_and_apply(self, _action: int) -> None:
         """
         Applies agent actions to the nodes and Access Control List.
 
@@ -458,7 +474,7 @@ class Primaite(Env):
         else:
             logging.error("Invalid action type found")
 
-    def apply_actions_to_nodes(self, _action):
+    def apply_actions_to_nodes(self, _action: int) -> None:
         """
         Applies agent actions to the nodes.