# ChatClientSlot

> Tracon documentation. Tracon is a .NET package family that adds a control
> plane on Microsoft Agent Framework, published as NuGet packages that run
> inside your own ASP.NET Core application.
>
> Page: https://tracon.dev/api/tracon.chatclientslot/
> Summary: ChatClientSlot: Where a chat client ring that an agent extension adds sits in the agent's model pipeline.

<div class="api-provenance">Namespace Tracon · Assembly <code>Tracon.Core.dll</code></div>

Where a chat client ring that an agent extension adds sits in the agent's model pipeline.

```csharp
public enum ChatClientSlot
```

## Fields

`ModelCall = 0` 

Inside the tool-call loop, above the run budget, the response cache, the `chat` span
and the content guard. The ring sees every model call of a turn, including the call that
takes a tool result to the model. A user or tool message that the ring adds reaches the
content guard, the budget counts the request that the ring sends, and the cache key is
built from that request.

`Turn = 1` 

Outside the tool-call loop, below attachment resolution, the circuit breaker and the
fallback chain. The ring sees one call for each agent turn, and the loop runs inside that
call. A turn that the fallback chain tries again on another model goes through the same
ring of that model.

## Remarks

Tracon builds the model pipeline of a compiled agent, from the outside in: error
normalization, finish-reason detection, the fallback chain, the circuit breaker,
attachment resolution, the tool-call loop, the run budget, the response cache, hosted tool
usage, the `chat` span, the content guard, the concurrency limit, and the provider's
raw client. A ring goes into one of two fixed places in that order. It never goes below
the content guard, so the guard inspects the user, assistant and tool messages that the
ring sends.

The guard does not inspect a system message or `ChatOptions.Instructions`, on any
agent, and a ring receives the response after the guard has inspected it. Do not let a
ring put text it did not write into a system message or into the instructions.

Add a ring with [AgentExtensionContext.UseChatClient](/api/tracon.agentextensioncontext/#Tracon_AgentExtensionContext_UseChatClient_Tracon_ChatClientSlot_System_Func_Microsoft_Extensions_AI_IChatClient_Microsoft_Extensions_AI_IChatClient__).