very rough sketch for TeamManager interface

com.unity.ml-agents/Runtime/Agent.cs

         /// </summary>
         float[] m_LegacyActionCache;
 
+        private ITeamManager m_TeamManager;
+
         /// <summary>
         /// Called when the attached [GameObject] becomes enabled and active.
         /// [GameObject]: https://docs.unity3d.com/Manual/GameObjects.html
         /// <summary>
         /// The reason that the Agent has been set to "done".
         /// </summary>
-        enum DoneReason
+        public enum DoneReason
         {
             /// <summary>
             /// The episode was ended manually by calling <see cref="EndEpisode"/>.
                 }
             }
             // Request the last decision with no callbacks
-            // We request a decision so Python knows the Agent is done immediately
-            m_Brain?.RequestDecision(m_Info, sensors);
-            ResetSensors();
+            if (m_TeamManager != null)
+            {
+                // Send final observations to TeamManager if it exists.
+                // The TeamManager is responsible to keeping track of the Agent after it's
+                // done, including propagating any "posthumous" rewards.
+                m_TeamManager.OnAgentDone(this, doneReason, sensors);
+            }
+            else
+            {
+                // We request a decision so Python knows the Agent is done immediately
+                m_Brain?.RequestDecision(m_Info, sensors);
+                ResetSensors();
+            }
 
             // We also have to write any to any DemonstationStores so that they get the "done" flag.
             foreach (var demoWriter in DemonstrationWriters)
             var actions = m_Brain?.DecideAction() ?? new ActionBuffers();
             m_Info.CopyActions(actions);
             m_ActuatorManager.UpdateActions(actions);
+        }
+
+        public void SetTeamManager(ITeamManager teamManager)
+        {
+            m_TeamManager = teamManager;
+            teamManager?.RegisterAgent(this);
         }
     }
 }

com.unity.ml-agents.extensions/Runtime/Teams.meta

+fileFormatVersion: 2
+guid: 77124df6c18c4f669052016b3116147e
+timeCreated: 1610064454

com.unity.ml-agents/Runtime/ITeamManager.cs

+using System.Collections.Generic;
+using Unity.MLAgents.Sensors;
+
+namespace Unity.MLAgents
+{
+    public interface ITeamManager
+    {
+        void RegisterAgent(Agent agent);
+        // TODO not sure this is all the info we need, maybe pass a class/struct instead.
+        void OnAgentDone(Agent agent, Agent.DoneReason doneReason, List<ISensor> sensors);
+    }
+}

com.unity.ml-agents/Runtime/ITeamManager.cs.meta

+fileFormatVersion: 2
+guid: 75810d91665e4477977eb78c9b15aeb3
+timeCreated: 1610057818

com.unity.ml-agents.extensions/Runtime/Teams/BaseTeamManager.cs

+using System.Collections.Generic;
+using Unity.MLAgents;
+using Unity.MLAgents.Sensors;
+
+namespace Teams
+{
+    // TODO abstract? inherit from MonoBehavior?
+    public class BaseTeamManager : ITeamManager
+    {
+        public void RegisterAgent(Agent agent)
+        {
+            throw new System.NotImplementedException();
+        }
+
+        public void OnAgentDone(Agent agent, Agent.DoneReason doneReason, List<ISensor> sensors)
+        {
+            // Possible implementation - save reference to Agent's IPolicy so that we can repeatedly
+            // call IPolicy.RequestDecision on behalf of the Agent after it's dead
+            // If so, we'll need dummy sensor impls with the same shape as the originals.
+            throw new System.NotImplementedException();
+        }
+
+        public void AddTeamReward(float reward)
+        {
+
+        }
+
+    }
+}

com.unity.ml-agents.extensions/Runtime/Teams/BaseTeamManager.cs.meta

+fileFormatVersion: 2
+guid: b2967f9c3bd4449a98ad309085094769
+timeCreated: 1610064493