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Migrating to the ml-agents-envs 0.30.0 package

  • Python 3.10.12 is now the minimum version of python supported due to python3.6 EOL. Please update your python installation to 3.10.12 or higher.
  • The gym-unity package has been refactored into the ml-agents-envs package. Please update your imports accordingly.
  • Example:
  • Before python from gym_unity.unity_gym_env import UnityToGymWrapper
  • After: python from mlagents_envs.envs.unity_gym_env import UnityToGymWrapper

Migrating the package to version 3.x

  • The official version of Unity ML-Agents supports is now 2023.2. If you run into issues, please consider deleting your project's Library folder and reopening your project.

Migrating the package to version 2.x

  • The official version of Unity ML-Agents supports is now 2022.3 LTS. If you run into issues, please consider deleting your project's Library folder and reopening your project.
  • If you used any of the APIs that were deprecated before version 2.0, you need to use their replacement. These deprecated APIs have been removed. See the migration steps bellow for specific API replacements.

Deprecated methods removed

Deprecated API Suggested Replacement
IActuator ActuatorComponent.CreateActuator() IActuator[] ActuatorComponent.CreateActuators()
IActionReceiver.PackActions(in float[] destination) none
Agent.CollectDiscreteActionMasks(DiscreteActionMasker actionMasker) Agent.WriteDiscreteActionMask(IDiscreteActionMask actionMask)
Agent.Heuristic(float[] actionsOut) Agent.Heuristic(in ActionBuffers actionsOut)
Agent.OnActionReceived(float[] vectorAction) Agent.OnActionReceived(ActionBuffers actions)
Agent.GetAction() Agent.GetStoredActionBuffers()
BrainParameters.SpaceType, VectorActionSize, VectorActionSpaceType, and NumActions BrainParameters.ActionSpec
ObservationWriter.AddRange(IEnumerable<float> data, int writeOffset = 0) ObservationWriter. AddList(IList<float> data, int writeOffset = 0
SensorComponent.IsVisual() and IsVector() none
VectorSensor.AddObservation(IEnumerable<float> observation) VectorSensor.AddObservation(IList<float> observation)
SideChannelsManager SideChannelManager

IDiscreteActionMask changes

  • The interface for disabling specific discrete actions has changed. IDiscreteActionMask.WriteMask() was removed, and replaced with SetActionEnabled(). Instead of returning an IEnumerable with indices to disable, you can now call SetActionEnabled for each index to disable (or enable). As an example, if you overrode Agent.WriteDiscreteActionMask() with something that looked like:
public override void WriteDiscreteActionMask(IDiscreteActionMask actionMask)
    var branch = 2;
    var actionsToDisable = new[] {1, 3};
    actionMask.WriteMask(branch, actionsToDisable);

the equivalent code would now be

public override void WriteDiscreteActionMask(IDiscreteActionMask actionMask)
    var branch = 2;
    actionMask.SetActionEnabled(branch, 1, false);
    actionMask.SetActionEnabled(branch, 3, false);

IActuator changes

  • The IActuator interface now implements IHeuristicProvider. Please add the corresponding Heuristic(in ActionBuffers) method to your custom Actuator classes.

ISensor and SensorComponent changes

  • The ISensor.GetObservationShape() method and ITypedSensor and IDimensionPropertiesSensor interfaces were removed, and GetObservationSpec() was added. You can use ObservationSpec.Vector() or ObservationSpec.Visual() to generate ObservationSpecs that are equivalent to the previous shape. For example, if your old ISensor looked like:
public override int[] GetObservationShape()
    return new[] { m_Height, m_Width, m_NumChannels };

the equivalent code would now be

public override ObservationSpec GetObservationSpec()
    return ObservationSpec.Visual(m_Height, m_Width, m_NumChannels);
  • The ISensor.GetCompressionType() method and ISparseChannelSensor interface was removed, and GetCompressionSpec() was added. You can use CompressionSpec.Default() or CompressionSpec.Compressed() to generate CompressionSpecs that are equivalent to the previous values. For example, if your old ISensor looked like: ```csharp public virtual SensorCompressionType GetCompressionType() { return SensorCompressionType.None; }

the equivalent code would now be

public CompressionSpec GetCompressionSpec()
    return CompressionSpec.Default();
  • The abstract method SensorComponent.GetObservationShape() was removed.
  • The abstract method SensorComponent.CreateSensor() was replaced with CreateSensors(), which returns an ISensor[].

Match3 integration changes

The Match-3 integration utilities were moved from to

The AbstractBoard interface was changed: * AbstractBoard no longer contains Rows, Columns, NumCellTypes, and NumSpecialTypes fields. * public abstract BoardSize GetMaxBoardSize() was added as an abstract method. BoardSize is a new struct that contains Rows, Columns, NumCellTypes, and NumSpecialTypes fields, with the same meanings as the old AbstractBoard fields. * public virtual BoardSize GetCurrentBoardSize() is an optional method; by default it returns GetMaxBoardSize(). If you wish to use a single behavior to work with multiple board sizes, override GetCurrentBoardSize() to return the current BoardSize. The values returned by GetCurrentBoardSize() must be less than or equal to the corresponding values from GetMaxBoardSize().

GridSensor changes

The sensor configuration has changed: * The sensor implementation has been refactored and existing GridSensor created from extension package will not work in newer version. Some errors might show up when loading the old sensor in the scene. You'll need to remove the old sensor and create a new GridSensor. * These parameters names have changed but still refer to the same concept in the sensor: GridNumSide -> GridSize, RotateToAgent -> RotateWithAgent, ObserveMask -> ColliderMask, DetectableObjects -> DetectableTags * DepthType (ChanelBase/ChannelHot) option and ChannelDepth are removed. Now the default is one-hot encoding for detected tag. If you were using original GridSensor without overriding any method, switching to new GridSensor will produce similar effect for training although the actual observations will be slightly different.

For creating your GridSensor implementation with custom data: * To create custom GridSensor, derive from GridSensorBase instead of GridSensor. Besides overriding GetObjectData(), you will also need to consider override GetCellObservationSize(), IsDataNormalized() and GetProcessCollidersMethod() according to the data you collect. Also you'll need to override GridSensorComponent.GetGridSensors() and return your custom GridSensor. * The input argument tagIndex in GetObjectData() has changed from 1-indexed to 0-indexed and the data type changed from float to int. The index of first detectable tag will be 0 instead of 1. normalizedDistance was removed from input. * The observation data should be written to the input dataBuffer instead of creating and returning a new array. * Removed the constraint of all data required to be normalized. You should specify it in IsDataNormalized(). Sensors with non-normalized data cannot use PNG compression type. * The sensor will not further encode the data received from GetObjectData() anymore. The values received from GetObjectData() will be the observation sent to the trainer.

LSTM models from previous releases no longer supported

The way that Sentis processes LSTM (recurrent neural networks) has changed. As a result, models trained with previous versions of ML-Agents will not be usable at inference if they were trained with a memory setting in the .yaml config file. If you want to use a model that has a recurrent neural network in this release of ML-Agents, you need to train the model using the python trainer from this release.

Migrating to Release 13

Implementing IHeuristic in your IActuator implementations

  • If you have any custom actuators, you can now implement the IHeuristicProvider interface to have your actuator handle the generation of actions when an Agent is running in heuristic mode.
  • VectorSensor.AddObservation(IEnumerable<float>) is deprecated. Use VectorSensor.AddObservation(IList<float>) instead.
  • ObservationWriter.AddRange() is deprecated. Use ObservationWriter.AddList() instead.
  • ActuatorComponent.CreateActuator() is deprecated. Please use override ActuatorComponent.CreateActuators instead. Since ActuatorComponent.CreateActuator() is abstract, you will still need to override it in your class until it is removed. It is only ever called if you don't override ActuatorComponent.CreateActuators. You can suppress the warnings by surrounding the method with the following pragma: c# #pragma warning disable 672 public IActuator CreateActuator() { ... } #pragma warning restore 672


Migrating to Release 11

Agent virtual method deprecation

  • Agent.CollectDiscreteActionMasks() was deprecated and should be replaced with Agent.WriteDiscreteActionMask()
  • Agent.Heuristic(float[]) was deprecated and should be replaced with Agent.Heuristic(ActionBuffers).
  • Agent.OnActionReceived(float[]) was deprecated and should be replaced with Agent.OnActionReceived(ActionBuffers).
  • Agent.GetAction() was deprecated and should be replaced with Agent.GetStoredActionBuffers().

The default implementation of these will continue to call the deprecated versions where appropriate. However, the deprecated versions may not be compatible with continuous and discrete actions on the same Agent.

BrainParameters field and method deprecation

  • BrainParameters.VectorActionSize was deprecated; you can now set BrainParameters.ActionSpec.NumContinuousActions or BrainParameters.ActionSpec.BranchSizes instead.
  • BrainParameters.VectorActionSpaceType was deprecated, since both continuous and discrete actions can now be used.
  • BrainParameters.NumActions() was deprecated. Use BrainParameters.ActionSpec.NumContinuousActions and BrainParameters.ActionSpec.NumDiscreteActions instead.

Migrating from Release 7 to latest

Important changes

  • Some trainer files were moved. If you were using the TrainerFactory class, it was moved to the trainers/trainer folder.
  • The components folder containing bc and reward_signals code was moved to the trainers/tf folder

Steps to Migrate

  • Replace calls to from mlagents.trainers.trainer_util import TrainerFactory to from mlagents.trainers.trainer import TrainerFactory
  • Replace calls to from mlagents.trainers.trainer_util import handle_existing_directories to from mlagents.trainers.directory_utils import validate_existing_directories
  • Replace mlagents.trainers.components with in your import statements.

Migrating from Release 3 to Release 7

Important changes

  • The Parameter Randomization feature has been merged with the Curriculum feature. It is now possible to specify a sampler in the lesson of a Curriculum. Curriculum has been refactored and is now specified at the level of the parameter, not the behavior. More information here.(#4160)

Steps to Migrate

  • The configuration format for curriculum and parameter randomization has changed. To upgrade your configuration files, an upgrade script has been provided. Run python -m mlagents.trainers.upgrade_config -h to see the script usage. Note that you will have had to upgrade to/install the current version of ML-Agents before running the script. To update manually:
  • If your config file used a parameter_randomization section, rename that section to environment_parameters
  • If your config file used a curriculum section, you will need to rewrite your curriculum with this format.

Migrating from Release 1 to Release 3

Important changes

  • Training artifacts (trained models, summaries) are now found under results/ instead of summaries/ and models/.
  • Trainer configuration, curriculum configuration, and parameter randomization configuration have all been moved to a single YAML file. (#3791)
  • Trainer configuration format has changed, and using a "default" behavior name has been deprecated. (#3936)
  • max_step in the TerminalStep and TerminalSteps objects was renamed interrupted.
  • On the UnityEnvironment API, get_behavior_names() and get_behavior_specs() methods were combined into the property behavior_specs that contains a mapping from behavior names to behavior spec.
  • use_visual and allow_multiple_visual_obs in the UnityToGymWrapper constructor were replaced by allow_multiple_obs which allows one or more visual observations and vector observations to be used simultaneously.
  • --save-freq has been removed from the CLI and is now configurable in the trainer configuration file.
  • --lesson has been removed from the CLI. Lessons will resume when using --resume. To start at a different lesson, modify your Curriculum configuration.

Steps to Migrate

  • To upgrade your configuration files, an upgrade script has been provided. Run python -m mlagents.trainers.upgrade_config -h to see the script usage. Note that you will have had to upgrade to/install the current version of ML-Agents before running the script.

To do it manually, copy your <BehaviorName> sections from trainer_config.yaml into a separate trainer configuration file, under a behaviors section. The default section is no longer needed. This new file should be specific to your environment, and not contain configurations for multiple environments (unless they have the same Behavior Names). - You will need to reformat your trainer settings as per the example. - If your training uses curriculum, move those configurations under a curriculum section. - If your training uses parameter randomization, move the contents of the sampler config to parameter_randomization in the main trainer configuration. - If you are using UnityEnvironment directly, replace max_step with interrupted in the TerminalStep and TerminalSteps objects. - Replace usage of get_behavior_names() and get_behavior_specs() in UnityEnvironment with behavior_specs. - If you use the UnityToGymWrapper, remove use_visual and allow_multiple_visual_obs from the constructor and add allow_multiple_obs = True if the environment contains either both visual and vector observations or multiple visual observations. - If you were setting --save-freq in the CLI, add a checkpoint_interval value in your trainer configuration, and set it equal to save-freq * n_agents_in_scene.

Migrating from 0.15 to Release 1

Important changes

  • The MLAgents C# namespace was renamed to Unity.MLAgents, and other nested namespaces were similarly renamed (#3843).
  • The --load and --train command-line flags have been deprecated and replaced with --resume and --inference.
  • Running with the same --run-id twice will now throw an error.
  • The play_against_current_self_ratio self-play trainer hyperparameter has been renamed to play_against_latest_model_ratio
  • Removed the multi-agent gym option from the gym wrapper. For multi-agent scenarios, use the Low Level Python API.
  • The low level Python API has changed. You can look at the document Low Level Python API documentation for more information. If you use mlagents-learn for training, this should be a transparent change.
  • The obsolete Agent methods GiveModel, Done, InitializeAgent, AgentAction and AgentReset have been removed.
  • The signature of Agent.Heuristic() was changed to take a float[] as a parameter, instead of returning the array. This was done to prevent a common source of error where users would return arrays of the wrong size.
  • The SideChannel API has changed (#3833, #3660) :
  • Introduced the SideChannelManager to register, unregister and access side channels.
  • EnvironmentParameters replaces the default FloatProperties. You can access the EnvironmentParameters with Academy.Instance.EnvironmentParameters on C#. If you were previously creating a UnityEnvironment in python and passing it a FloatPropertiesChannel, create an EnvironmentParametersChannel instead.
  • SideChannel.OnMessageReceived is now a protected method (was public)
  • SideChannel IncomingMessages methods now take an optional default argument, which is used when trying to read more data than the message contains.
  • Added a feature to allow sending stats from C# environments to TensorBoard (and other python StatsWriters). To do this from your code, use Academy.Instance.StatsRecorder.Add(key, value)(#3660)
  • num_updates and train_interval for SAC have been replaced with steps_per_update.
  • The UnityEnv class from the gym-unity package was renamed UnityToGymWrapper and no longer creates the UnityEnvironment. Instead, the UnityEnvironment must be passed as input to the constructor of UnityToGymWrapper
  • Public fields and properties on several classes were renamed to follow Unity's C# style conventions. All public fields and properties now use "PascalCase" instead of "camelCase"; for example, Agent.maxStep was renamed to Agent.MaxStep. For a full list of changes, see the pull request. (#3828)
  • WriteAdapter was renamed to ObservationWriter. (#3834)

Steps to Migrate

  • In C# code, replace using MLAgents with using Unity.MLAgents. Replace other nested namespaces such as using MLAgents.Sensors with using Unity.MLAgents.Sensors
  • Replace the --load flag with --resume when calling mlagents-learn, and don't use the --train flag as training will happen by default. To run without training, use --inference.
  • To force-overwrite files from a pre-existing run, add the --force command-line flag.
  • The Jupyter notebooks have been removed from the repository.
  • If your Agent class overrides Heuristic(), change the signature to public override void Heuristic(float[] actionsOut) and assign values to actionsOut instead of returning an array.
  • If you used SideChannels you must:
  • Replace Academy.FloatProperties with Academy.Instance.EnvironmentParameters.
  • Academy.RegisterSideChannel and Academy.UnregisterSideChannel were removed. Use SideChannelManager.RegisterSideChannel and SideChannelManager.UnregisterSideChannel instead.
  • Set steps_per_update to be around equal to the number of agents in your environment, times num_updates and divided by train_interval.
  • Replace UnityEnv with UnityToGymWrapper in your code. The constructor no longer takes a file name as input but a fully constructed UnityEnvironment instead.
  • Update uses of "camelCase" fields and properties to "PascalCase".

Migrating from 0.14 to 0.15

Important changes

  • The Agent.CollectObservations() virtual method now takes as input a VectorSensor sensor as argument. The Agent.AddVectorObs() methods were removed.
  • The SetMask was renamed to SetMask method must now be called on the DiscreteActionMasker argument of the CollectDiscreteActionMasks virtual method.
  • We consolidated our API for DiscreteActionMasker. SetMask takes two arguments : the branch index and the list of masked actions for that branch.
  • The Monitor class has been moved to the Examples Project. (It was prone to errors during testing)
  • The MLAgents.Sensors namespace has been introduced. All sensors classes are part of the MLAgents.Sensors namespace.
  • The MLAgents.SideChannels namespace has been introduced. All side channel classes are part of the MLAgents.SideChannels namespace.
  • The interface for RayPerceptionSensor.PerceiveStatic() was changed to take an input class and write to an output class, and the method was renamed to Perceive().
  • The SetMask method must now be called on the DiscreteActionMasker argument of the CollectDiscreteActionMasks method.
  • The method GetStepCount() on the Agent class has been replaced with the property getter StepCount
  • The --multi-gpu option has been removed temporarily.
  • AgentInfo.actionMasks has been renamed to AgentInfo.discreteActionMasks.
  • BrainParameters and SpaceType have been removed from the public API
  • BehaviorParameters have been removed from the public API.
  • DecisionRequester has been made internal (you can still use the DecisionRequesterComponent from the inspector). RepeatAction was renamed TakeActionsBetweenDecisions for clarity.
  • The following methods in the Agent class have been renamed. The original method names will be removed in a later release:
  • InitializeAgent() was renamed to Initialize()
  • AgentAction() was renamed to OnActionReceived()
  • AgentReset() was renamed to OnEpisodeBegin()
  • Done() was renamed to EndEpisode()
  • GiveModel() was renamed to SetModel()
  • The IFloatProperties interface has been removed.
  • The interface for SideChannels was changed:
  • In C#, OnMessageReceived now takes a IncomingMessage argument, and QueueMessageToSend takes an OutgoingMessage argument.
  • In python, on_message_received now takes a IncomingMessage argument, and queue_message_to_send takes an OutgoingMessage argument.
  • Automatic stepping for Academy is now controlled from the AutomaticSteppingEnabled property.

Steps to Migrate

  • Add the using MLAgents.Sensors; in addition to using MLAgents; on top of your Agent's script.
  • Replace your Agent's implementation of CollectObservations() with CollectObservations(VectorSensor sensor). In addition, replace all calls to AddVectorObs() with sensor.AddObservation() or sensor.AddOneHotObservation() on the VectorSensor passed as argument.
  • Replace your calls to SetActionMask on your Agent to DiscreteActionMasker.SetActionMask in CollectDiscreteActionMasks.
  • If you call RayPerceptionSensor.PerceiveStatic() manually, add your inputs to a RayPerceptionInput. To get the previous float array output, iterate through RayPerceptionOutput.rayOutputs and call RayPerceptionOutput.RayOutput.ToFloatArray().
  • Replace all calls to Agent.GetStepCount() with Agent.StepCount
  • We strongly recommend replacing the following methods with their new equivalent as they will be removed in a later release:
  • InitializeAgent() to Initialize()
  • AgentAction() to OnActionReceived()
  • AgentReset() to OnEpisodeBegin()
  • Done() to EndEpisode()
  • GiveModel() to SetModel()
  • Replace IFloatProperties variables with FloatPropertiesChannel variables.
  • If you implemented custom SideChannels, update the signatures of your methods, and add your data to the OutgoingMessage or read it from the IncomingMessage.
  • Replace calls to Academy.EnableAutomaticStepping()/DisableAutomaticStepping() with Academy.AutomaticSteppingEnabled = true/false.

Migrating from 0.13 to 0.14

Important changes

  • The UnitySDK folder has been split into a Unity Package ( and an examples project (Project). Please follow the Installation Guide to get up and running with this new repo structure.
  • Several changes were made to how agents are reset and marked as done:
  • Calling Done() on the Agent will now reset it immediately and call the AgentReset virtual method. (This is to simplify the previous logic in which the Agent had to wait for the next EnvironmentStep to reset)
  • The "Reset on Done" setting in AgentParameters was removed; this is now effectively always true. AgentOnDone virtual method on the Agent has been removed.
  • The Decision Period and On Demand decision checkbox have been removed from the Agent. On demand decision is now the default (calling RequestDecision on the Agent manually.)
  • The Academy class was changed to a singleton, and its virtual methods were removed.
  • Trainer steps are now counted per-Agent, not per-environment as in previous versions. For instance, if you have 10 Agents in the scene, 20 environment steps now corresponds to 200 steps as printed in the terminal and in Tensorboard.
  • Curriculum config files are now YAML formatted and all curricula for a training run are combined into a single file.
  • The --num-runs command-line option has been removed from mlagents-learn.
  • Several fields on the Agent were removed or made private in order to simplify the interface.
  • The agentParameters field of the Agent has been removed. (Contained only maxStep information)
  • maxStep is now a public field on the Agent. (Was moved from agentParameters)
  • The Info field of the Agent has been made private. (Was only used internally and not meant to be modified outside of the Agent)
  • The GetReward() method on the Agent has been removed. (It was being confused with GetCumulativeReward())
  • The AgentAction struct no longer contains a value field. (Value estimates were not set during inference)
  • The GetValueEstimate() method on the Agent has been removed.
  • The UpdateValueAction() method on the Agent has been removed.
  • The deprecated RayPerception3D and RayPerception2D classes were removed, and the legacyHitFractionBehavior argument was removed from RayPerceptionSensor.PerceiveStatic().
  • RayPerceptionSensor was inconsistent in how it handle scale on the Agent's transform. It now scales the ray length and sphere size for casting as the transform's scale changes.

Steps to Migrate

  • Follow the instructions on how to install the package into your project in the Installation Guide.
  • If your Agent implemented AgentOnDone and did not have the checkbox Reset On Done checked in the inspector, you must call the code that was in AgentOnDone manually.
  • If you give your Agent a reward or penalty at the end of an episode (e.g. for reaching a goal or falling off of a platform), make sure you call AddReward() or SetReward() before calling Done(). Previously, the order didn't matter.
  • If you were not using On Demand Decision for your Agent, you must add a DecisionRequester component to your Agent GameObject and set its Decision Period field to the old Decision Period of the Agent.
  • If you have a class that inherits from Academy:
  • If the class didn't override any of the virtual methods and didn't store any additional data, you can just remove the old script from the scene.
  • If the class had additional data, create a new MonoBehaviour and store the data in the new MonoBehaviour instead.
  • If the class overrode the virtual methods, create a new MonoBehaviour and move the logic to it:
    • Move the InitializeAcademy code to MonoBehaviour.Awake
    • Move the AcademyStep code to MonoBehaviour.FixedUpdate
    • Move the OnDestroy code to MonoBehaviour.OnDestroy.
    • Move the AcademyReset code to a new method and add it to the Academy.OnEnvironmentReset action.
  • Multiply max_steps and summary_freq in your trainer_config.yaml by the number of Agents in the scene.
  • Combine curriculum configs into a single file. See the WallJump curricula for an example of the new curriculum config format. A tool like may be useful to help with the conversion.
  • If you have a model trained which uses RayPerceptionSensor and has non-1.0 scale in the Agent's transform, it must be retrained.

Migrating from ML-Agents Toolkit v0.12.0 to v0.13.0

Important changes

  • The low level Python API has changed. You can look at the document Low Level Python API documentation for more information. This should only affect you if you're writing a custom trainer; if you use mlagents-learn for training, this should be a transparent change.
  • reset() on the Low-Level Python API no longer takes a train_mode argument. To modify the performance/speed of the engine, you must use an EngineConfigurationChannel
  • reset() on the Low-Level Python API no longer takes a config argument. UnityEnvironment no longer has a reset_parameters field. To modify float properties in the environment, you must use a FloatPropertiesChannel. For more information, refer to the Low Level Python API documentation
  • CustomResetParameters are now removed.
  • The Academy no longer has a Training Configuration nor Inference Configuration field in the inspector. To modify the configuration from the Low-Level Python API, use an EngineConfigurationChannel. To modify it during training, use the new command line arguments --width, --height, --quality-level, --time-scale and --target-frame-rate in mlagents-learn.
  • The Academy no longer has a Default Reset Parameters field in the inspector. The Academy class no longer has a ResetParameters. To access shared float properties with Python, use the new FloatProperties field on the Academy.
  • Offline Behavioral Cloning has been removed. To learn from demonstrations, use the GAIL and Behavioral Cloning features with either PPO or SAC.
  • mlagents.envs was renamed to mlagents_envs. The previous repo layout depended on PEP420, which caused problems with some of our tooling such as mypy and pylint.
  • The official version of Unity ML-Agents supports is now 2022.3 LTS. If you run into issues, please consider deleting your library folder and reopening your projects. You will need to install the Sentis package into your project in order to ML-Agents to compile correctly.

Steps to Migrate

  • If you had a custom Training Configuration in the Academy inspector, you will need to pass your custom configuration at every training run using the new command line arguments --width, --height, --quality-level, --time-scale and --target-frame-rate.
  • If you were using --slow in mlagents-learn, you will need to pass your old Inference Configuration of the Academy inspector with the new command line arguments --width, --height, --quality-level, --time-scale and --target-frame-rate instead.
  • Any imports from mlagents.envs should be replaced with mlagents_envs.

Migrating from ML-Agents Toolkit v0.11.0 to v0.12.0

Important Changes

  • Text actions and observations, and custom action and observation protos have been removed.
  • RayPerception3D and RayPerception2D are marked deprecated, and will be removed in a future release. They can be replaced by RayPerceptionSensorComponent3D and RayPerceptionSensorComponent2D.
  • The Use Heuristic checkbox in Behavior Parameters has been replaced with a Behavior Type dropdown menu. This has the following options:
  • Default corresponds to the previous unchecked behavior, meaning that Agents will train if they connect to a python trainer, otherwise they will perform inference.
  • Heuristic Only means the Agent will always use the Heuristic() method. This corresponds to having "Use Heuristic" selected in 0.11.0.
  • Inference Only means the Agent will always perform inference.
  • ML-Agents was upgraded to use Sentis 1.2.0-exp.2 and is installed via the package manager.

Steps to Migrate

  • We fixed a bug in RayPerception3d.Perceive() that was causing the endOffset to be used incorrectly. However this may produce different behavior from previous versions if you use a non-zero startOffset. To reproduce the old behavior, you should increase the value of endOffset by startOffset. You can verify your raycasts are performing as expected in scene view using the debug rays.
  • If you use RayPerception3D, replace it with RayPerceptionSensorComponent3D (and similarly for 2D). The settings, such as ray angles and detectable tags, are configured on the component now. RayPerception3D would contribute (# of rays) * (# of tags + 2) to the State Size in Behavior Parameters, but this is no longer necessary, so you should reduce the State Size by this amount. Making this change will require retraining your model, since the observations that RayPerceptionSensorComponent3D produces are different from the old behavior.
  • If you see messages such as The type or namespace 'Sentis' could not be found or The type or namespace 'Google' could not be found, you will need to install the Sentis preview package.

Migrating from ML-Agents Toolkit v0.10 to v0.11.0

Important Changes

  • The definition of the gRPC service has changed.
  • The online BC training feature has been removed.
  • The BroadcastHub has been deprecated. If there is a training Python process, all LearningBrains in the scene will automatically be trained. If there is no Python process, inference will be used.
  • The Brain ScriptableObjects have been deprecated. The Brain Parameters are now on the Agent and are referred to as Behavior Parameters. Make sure the Behavior Parameters is attached to the Agent GameObject.
  • To use a heuristic behavior, implement the Heuristic() method in the Agent class and check the use heuristic checkbox in the Behavior Parameters.
  • Several changes were made to the setup for visual observations (i.e. using Cameras or RenderTextures):
  • Camera resolutions are no longer stored in the Brain Parameters.
  • AgentParameters no longer stores lists of Cameras and RenderTextures
  • To add visual observations to an Agent, you must now attach a CameraSensorComponent or RenderTextureComponent to the agent. The corresponding Camera or RenderTexture can be added to these in the editor, and the resolution and color/grayscale is configured on the component itself.

Steps to Migrate

  • In order to be able to train, make sure both your ML-Agents Python package and UnitySDK code come from the v0.11 release. Training will not work, for example, if you update the ML-Agents Python package, and only update the API Version in UnitySDK.
  • If your Agents used visual observations, you must add a CameraSensorComponent corresponding to each old Camera in the Agent's camera list (and similarly for RenderTextures).
  • Since Brain ScriptableObjects have been removed, you will need to delete all the Brain ScriptableObjects from your Assets folder. Then, add a Behavior Parameters component to each Agent GameObject. You will then need to complete the fields on the new Behavior Parameters component with the BrainParameters of the old Brain.

Migrating from ML-Agents Toolkit v0.9 to v0.10

Important Changes

  • We have updated the C# code in our repository to be in line with Unity Coding Conventions. This has changed the name of some public facing classes and enums.
  • The example environments have been updated. If you were using these environments to benchmark your training, please note that the resulting rewards may be slightly different in v0.10.

Steps to Migrate

  • UnitySDK/Assets/ML-Agents/Scripts/Communicator.cs and its class Communicator have been renamed to UnitySDK/Assets/ML-Agents/Scripts/ICommunicator.cs and ICommunicator respectively.
  • The SpaceType Enums discrete, and continuous have been renamed to Discrete and Continuous.
  • We have removed the Done call as well as the capacity to set Max Steps on the Academy. Therefore an AcademyReset will never be triggered from C# (only from Python). If you want to reset the simulation after a fixed number of steps, or when an event in the simulation occurs, we recommend looking at our multi-agent example environments (such as FoodCollector). In our examples, groups of Agents can be reset through an "Area" that can reset groups of Agents.
  • The import for mlagents.envs.UnityEnvironment was removed. If you are using the Python API, change from mlagents_envs import UnityEnvironment to from mlagents_envs.environment import UnityEnvironment.

Migrating from ML-Agents Toolkit v0.8 to v0.9

Important Changes

  • We have changed the way reward signals (including Curiosity) are defined in the trainer_config.yaml.
  • When using multiple environments, every "step" is recorded in TensorBoard.
  • The steps in the command line console corresponds to a single step of a single environment. Previously, each step corresponded to one step for all environments (i.e., num_envs steps).

Steps to Migrate

  • If you were overriding any of these following parameters in your config file, remove them from the top-level config and follow the steps below:
  • gamma: Define a new extrinsic reward signal and set it's gamma to your new gamma.
  • use_curiosity, curiosity_strength, curiosity_enc_size: Define a curiosity reward signal and set its strength to curiosity_strength, and encoding_size to curiosity_enc_size. Give it the same gamma as your extrinsic signal to mimic previous behavior.
  • TensorBoards generated when running multiple environments in v0.8 are not comparable to those generated in v0.9 in terms of step count. Multiply your v0.8 step count by num_envs for an approximate comparison. You may need to change max_steps in your config as appropriate as well.

Migrating from ML-Agents Toolkit v0.7 to v0.8

Important Changes

  • We have split the Python packages into two separate packages ml-agents and ml-agents-envs.
  • --worker-id option of has been removed, use --base-port instead if you'd like to run multiple instances of

Steps to Migrate

  • If you are installing via PyPI, there is no change.
  • If you intend to make modifications to ml-agents or ml-agents-envs please check the Installing for Development in the Installation documentation.

Migrating from ML-Agents Toolkit v0.6 to v0.7

Important Changes

  • We no longer support TFS and are now using the Sentis

Steps to Migrate

  • Make sure to remove the ENABLE_TENSORFLOW flag in your Unity Project settings

Migrating from ML-Agents Toolkit v0.5 to v0.6

Important Changes

  • Brains are now Scriptable Objects instead of MonoBehaviors.
  • You can no longer modify the type of a Brain. If you want to switch between PlayerBrain and LearningBrain for multiple agents, you will need to assign a new Brain to each agent separately. Note: You can pass the same Brain to multiple agents in a scene by leveraging Unity's prefab system or look for all the agents in a scene using the search bar of the Hierarchy window with the word Agent.

  • We replaced the Internal and External Brain with Learning Brain. When you need to train a model, you need to drag it into the Broadcast Hub inside the Academy and check the Control checkbox.

  • We removed the Broadcast checkbox of the Brain, to use the broadcast functionality, you need to drag the Brain into the Broadcast Hub.
  • When training multiple Brains at the same time, each model is now stored into a separate model file rather than in the same file under different graph scopes.
  • The Learning Brain graph scope, placeholder names, output names and custom placeholders can no longer be modified.

Steps to Migrate

  • To update a scene from v0.5 to v0.6, you must:
  • Remove the Brain GameObjects in the scene. (Delete all of the Brain GameObjects under Academy in the scene.)
  • Create new Brain Scriptable Objects using Assets -> Create -> ML-Agents for each type of the Brain you plan to use, and put the created files under a folder called Brains within your project.
  • Edit their Brain Parameters to be the same as the parameters used in the Brain GameObjects.
  • Agents have a Brain field in the Inspector, you need to drag the appropriate Brain ScriptableObject in it.
  • The Academy has a Broadcast Hub field in the inspector, which is list of brains used in the scene. To train or control your Brain from the mlagents-learn Python script, you need to drag the relevant LearningBrain ScriptableObjects used in your scene into entries into this list.

Migrating from ML-Agents Toolkit v0.4 to v0.5


  • The Unity project unity-environment has been renamed UnitySDK.
  • The python folder has been renamed to ml-agents. It now contains two packages, mlagents.env and mlagents.trainers. mlagents.env can be used to interact directly with a Unity environment, while mlagents.trainers contains the classes for training agents.
  • The supported Unity version has changed from 2017.1 or later to 2017.4 or later. 2017.4 is an LTS (Long Term Support) version that helps us maintain good quality and support. Earlier versions of Unity might still work, but you may encounter an error listed here.

Unity API

  • Discrete Actions now use branches. You can now specify concurrent discrete actions. You will need to update the Brain Parameters in the Brain Inspector in all your environments that use discrete actions. Refer to the discrete action documentation for more information.

Python API

  • In order to run a training session, you can now use the command mlagents-learn instead of python3 after installing the mlagents packages. This change is documented here. For example, if we previously ran

sh python3 3DBall --train

from the python subdirectory (which is changed to ml-agents subdirectory in v0.5), we now run

sh mlagents-learn config/trainer_config.yaml --env=3DBall --train

from the root directory where we installed the ML-Agents Toolkit.

  • It is now required to specify the path to the yaml trainer configuration file when running mlagents-learn. For an example trainer configuration file, see trainer_config.yaml. An example of passing a trainer configuration to mlagents-learn is shown above.
  • The environment name is now passed through the --env option.
  • Curriculum learning has been changed. In summary:
  • Curriculum files for the same environment must now be placed into a folder. Each curriculum file should be named after the Brain whose curriculum it specifies.
  • min_lesson_length now specifies the minimum number of episodes in a lesson and affects reward thresholding.
  • It is no longer necessary to specify the Max Steps of the Academy to use curriculum learning.

Migrating from ML-Agents Toolkit v0.3 to v0.4

Unity API

  • using MLAgents; needs to be added in all of the C# scripts that use ML-Agents.

Python API

  • We've changed some of the Python packages dependencies in requirement.txt file. Make sure to run pip3 install -e . within your ml-agents/python folder to update your Python packages.

Migrating from ML-Agents Toolkit v0.2 to v0.3

There are a large number of new features and improvements in the ML-Agents toolkit v0.3 which change both the training process and Unity API in ways which will cause incompatibilities with environments made using older versions. This page is designed to highlight those changes for users familiar with v0.1 or v0.2 in order to ensure a smooth transition.


  • The ML-Agents Toolkit is no longer compatible with Python 2.

Python Training

  • The training script and PPO.ipynb Python notebook have been replaced with a single script as the launching point for training with ML-Agents. For more information on using, see here.
  • Hyperparameters for training Brains are now stored in the trainer_config.yaml file. For more information on using this file, see here.

Unity API

  • Modifications to an Agent's rewards must now be done using either AddReward() or SetReward().
  • Setting an Agent to done now requires the use of the Done() method.
  • CollectStates() has been replaced by CollectObservations(), which now no longer returns a list of floats.
  • To collect observations, call AddVectorObs() within CollectObservations(). Note that you can call AddVectorObs() with floats, integers, lists and arrays of floats, Vector3 and Quaternions.
  • AgentStep() has been replaced by AgentAction().
  • WaitTime() has been removed.
  • The Frame Skip field of the Academy is replaced by the Agent's Decision Frequency field, enabling the Agent to make decisions at different frequencies.
  • The names of the inputs in the Internal Brain have been changed. You must replace state with vector_observation and observation with visual_observation. In addition, you must remove the epsilon placeholder.


In order to more closely align with the terminology used in the Reinforcement Learning field, and to be more descriptive, we have changed the names of some of the concepts used in ML-Agents. The changes are highlighted in the table below.

Old - v0.2 and earlier New - v0.3 and later
State Vector Observation
Observation Visual Observation
Action Vector Action
N/A Text Observation
N/A Text Action