# Authority transfer

### Overview

Authority over state changes to an Entity is transferrable, so it is possible to move the authority over the simulation of an Entity between Clients and Simulation Servers. This is useful for things such as balancing the simulation load, or exchanging items. It is possible for an Entity to have no Client or Simulator as the authority - these Entities are considered orphaned and are not simulated.

### Types of authority transfer

In the design phase, **CoherenceSync** objects can be configured to handle authority transfer in different ways:

* **Request**. Authority transfer may be requested, but it may be rejected by the current authority.
* **Steal.** Authority will always be given to the requesting party on a FCFS ("first come first serve") basis.
* **Not transferable**. Authority cannot be transferred.

{% hint style="info" %}
**Note** that you need to set up Auto-adopt Orphan if you want orphans to be adopted automatically when an Entity's authority disconnects, otherwise an orphaned Entity is not simulated.
{% endhint %}

![](/files/RtseqDyjEg5e98WqyOfK)

When using Request, an optional callback `OnAuthorityRequestedByConnection` can be set on the **CoherenceSync** behaviour. If the callback is set, then the results of the callback will override the Approve Requests setting in the behaviour.

The request can be approved or rejected in the callback.

```csharp
// connectionID is the network connection ID of the requesting client.
// sync is the CoherenceSync behaviour of the object the other client is
// requesting authority over.
public bool OnRequest(ushort connectionID, CoherenceSync sync)
{
    return (sync == theRightSync && connectionID == goodConnectionID);
}
```

{% hint style="info" %}
Support for requests based on [`CoherenceClientConnection.ClientID`](/0.9/authority/client-messages.md) is coming soon.
{% endhint %}

### Requesting authority in code

Requesting authority is very straight-forward.

```csharp
var coherenceSync = target.GetComponent<CoherenceSync>();
coherenceSync.RequestAuthority(AuthorityType.Full);
```

As the transfer is asynchronous, we have to subscribe to one or more **Unity Events** in **CoherenceSync** to learn the result.

The request will first go to the Replication Server and be passed onto the receiving Simulator or Game Client, so it may take a few frames to get a response.

```csharp
// There Unity Events in CoherenceSync help us understand 
// what happened with authority requests and act accordingly.

// called when the CoherenceSync entity becomes the simulation authority
public UnityEvent OnAuthorityGained;

// called when the CoherenceSync entity loses simulatino authority
public UnityEvent OnAuthorityLost;

// called when a request to assume authority over the CoherenceSync entity
// is rejected
public UnityEvent OnAuthorityTransferRejected;
```

These events are also exposed to the Unity inspector in the *Events on authority transfer* section of the **CoherenceSync** behaviour.

![Authority events in the CoherenceSync inspector](/files/-Me1I-ooYkkX8Tj9brQn)


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