## Overview
This approach makes the agent a **callable Teams identity**. A user searches for it by name and calls it 1:1, and the agent answers in real time — no phone number, PSTN, or Communications Credits. It’s the only approach callable by name, and the most involved to run.
It uses a **Microsoft Graph real-time media bot** (the Cloud Communications calling platform). The media SDK (`Microsoft.Skype.Bots.Media`) is **.NET on Windows Server only** — there is no Linux or non-.NET path for raw audio in Teams calls.
:::callout{intent="note"}
This is the only approach that’s callable **by name** inside Teams. Prefer the [widget tab](/guides/elevenagents-phone-numbers-microsoft-teams-widget-tab) for a lighter setup, or [ACS](/guides/elevenagents-phone-numbers-microsoft-teams-azure-communication-services) when you specifically want a phone number.
:::
## How it works
Call by name → media bot → ElevenLabs
The bot answers with **application-hosted media**, receives 50 audio frames/sec (20 ms PCM 16 kHz), bridges them to the ElevenLabs agent over a WebSocket, and streams the agent’s audio back into the call.
## Requirements
1. An **Azure Bot** registration + app (Entra app registration).
2. **Graph application permissions** with admin consent: `Calls.AccessMedia.All` (raw media) plus `Calls.Initiate.All`.
3. A **Windows Server VM** (≥ **2 physical cores** — e.g. `Standard_D4s_v3`) with a public IP and open media ports.
4. A **CA-signed TLS certificate** on a public FQDN for the media/signaling endpoint (the media platform rejects self-signed certs).
5. An [ElevenLabs agent](/guides/elevenagents-quickstart) set to **PCM 16000 Hz** on both legs: TTS output format on the **Voice** tab, user input audio format on the **Advanced** tab.
:::callout{intent="warning"}
A `D2s_v3` (2 vCPU = **1 physical core**) fails with `MediaPlatform needs a system with at least 2 cores`. Use a size with ≥ 2 physical cores (e.g. `D4s_v3`).
:::
## Permissions & roles
| Scope | Role / permission | Why |
| ----------------------------- | ------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------ |
| Entra | **Application Administrator** | create the app registration + Azure Bot |
| Entra | **Global Administrator / Privileged Role Administrator** | grant admin consent for the Graph calling permissions — app permissions cannot be self-consented |
| Microsoft Graph (application) | `Calls.AccessMedia.All`, `Calls.Initiate.All` | answer 1:1 calls and access raw media |
| Azure RBAC | **Contributor** on the resource group | create the Windows VM + Azure Bot |
| Teams admin | allow [**custom app upload**](https://admin.teams.microsoft.com/policies/manage-apps); enable the bot **Calling** channel | sideload the app and receive calls |
## Step 1 — Register the bot + Graph permissions
Create an app registration and an Azure Bot bound to it, then grant + consent the calling permissions (you need Global Admin / Privileged Role Admin to consent):
```bash
APPID=$(az ad app create --display-name "ElevenLabs Teams Agent" \
--sign-in-audience AzureADMyOrg --query appId -o tsv)
az ad sp create --id "$APPID"
# create a client secret and record it
az ad app credential reset --id "$APPID" --display-name bot --query password -o tsv
# Azure Bot bound to the app
az bot create --resource-group $RG --name el-teams-agent-bot \
--app-type SingleTenant --appid "$APPID" --tenant-id $TENANT \
--endpoint "https://YOUR_FQDN/api/messages" --sku S1
```
Grant the two Graph application roles and **admin consent** (needs Global Admin / Privileged Role Admin), then confirm the assignments landed:
```bash
# Graph app roles: Calls.AccessMedia.All, Calls.Initiate.All
az ad app permission add --id "$APPID" --api 00000003-0000-0000-c000-000000000000 \
--api-permissions a7a681dc-756e-4909-b988-f160edc6655f=Role \
284383ee-7f6e-4e40-a2a8-e85dcb029101=Role
az ad app permission admin-consent --id "$APPID"
# Verify — should print both role ids
az rest --method GET \
--url "https://graph.microsoft.com/v1.0/servicePrincipals(appId='$APPID')/appRoleAssignments" \
--query "value[].appRoleId" -o tsv
```
:::callout{intent="note"}
If `admin-consent` returns `Consent validation failed`, grant the app roles directly on the service principal instead:
```bash
GRAPH_SP=$(az ad sp show --id 00000003-0000-0000-c000-000000000000 --query id -o tsv)
BOT_SP=$(az ad sp show --id "$APPID" --query id -o tsv)
for ROLE in a7a681dc-756e-4909-b988-f160edc6655f 284383ee-7f6e-4e40-a2a8-e85dcb029101; do
az rest --method POST \
--url "https://graph.microsoft.com/v1.0/servicePrincipals/$GRAPH_SP/appRoleAssignedTo" \
--body "{\"principalId\": \"$BOT_SP\", \"resourceId\": \"$GRAPH_SP\", \"appRoleId\": \"$ROLE\"}"
done
```
:::
In the portal, verify in the [Entra admin center](https://entra.microsoft.com/#view/Microsoft_AAD_RegisteredApps/RegisteredAppsListBlade) under **App registrations → your app → API permissions**: both permissions should show **Granted** with green checks.
App registration → API permissions after admin consent
## Step 2 — Provision the Windows VM, cert and ports
```bash
az vm create -g $RG -n teams-media-bot --image Win2022Datacenter \
--size Standard_D4s_v3 --admin-username azureuser --admin-password '' \
--public-ip-sku Standard --public-ip-address-dns-name elevenmediabot
az vm open-port -g $RG -n teams-media-bot --port 80,443,8445,9441 --priority 300
```
On the VM (the media platform’s native code needs these — Windows Server lacks them by default):
```powershell
# VC++ runtime + Media Foundation feature (required by NativeMedia.dll)
choco install -y vcredist140
Install-WindowsFeature Server-Media-Foundation
# CA cert for the VM's FQDN via win-acme (HTTP-01), then import to LocalMachine\My
& wacs.exe --target manual --host .cloudapp.azure.com `
--validation selfhosting --store pfxfile --pfxfilepath C:\bot\certs --accepttos
```
Open the same ports in the **Windows firewall**, and note the cert **thumbprint** — the bot binds Kestrel (443 + a notifications port) and the media platform (8445) to it.
:::callout{intent="tip"}
The VM’s own `*.cloudapp.azure.com` FQDN works for a Let’s Encrypt cert — no separate domain needed.
:::
## Step 3 — Build and run the bot
Start from Microsoft’s [`microsoft-graph-comms-samples`](https://github.com/microsoftgraph/microsoft-graph-comms-samples) **PublicSamples/EchoBot** — it targets `net6.0` and builds with the .NET SDK (no Visual Studio Build Tools needed):
```powershell
git clone --depth 1 https://github.com/microsoftgraph/microsoft-graph-comms-samples.git C:\bot\samples
cd C:\bot\samples\Samples\PublicSamples\EchoBot\src
dotnet build EchoBot.sln -c Release
```
Configure the `AppSettings` section of `appsettings.json` with your `AadAppId`, `AadAppSecret`, `ServiceDnsName`/`MediaDnsName` (the VM FQDN), `CertificateThumbprint`, and ports (calling `443`, notifications `9441`, media `8445`). Add two settings for the ElevenLabs bridge below: `ElevenLabsAgentId` and `ElevenLabsOrigin` (`wss://api.elevenlabs.io`, or your residency host). Run it as a Windows scheduled task / service so it survives reboots.
:::callout{intent="warning"}
Task Scheduler’s default **execution time limit (72 hours)** silently kills long-running tasks — a bot started at boot dies three days later and calls fail with “we couldn’t connect you”. Disable the limit and add restart-on-failure:
```powershell
$s = New-ScheduledTaskSettingsSet -ExecutionTimeLimit (New-TimeSpan -Seconds 0) `
-RestartCount 999 -RestartInterval (New-TimeSpan -Minutes 1) -StartWhenAvailable
Set-ScheduledTask -TaskName EchoBot -Settings $s
```
:::
:::callout{intent="warning"}
The stock EchoBot crashes on a call placed to the standard port 443: `HttpHelpers.SetAbsoluteUri` calls `req.Host.Port.Value`, which is null when the Host header has no explicit port. Patch it to `req.Host.Port ?? (req.IsHttps ? 443 : 80)`.
:::
### Swap the echo for ElevenLabs
EchoBot’s audio seam is clean: `SpeechService.AppendAudioBuffer(in)` and an `OnSendMediaBufferEventArgs(out)` event. Replace its Azure-Speech body with an ElevenLabs agent WebSocket bridge that keeps the same surface:
```csharp title="SpeechService.cs — ElevenLabs bridge (core)"
public class SpeechService
{
private readonly AppSettings _settings;
private readonly ILogger _logger;
private ClientWebSocket _ws;
private bool _started;
private bool _connecting;
public event EventHandler SendMediaBuffer; // agent audio -> call
public event EventHandler FlushMedia; // barge-in: drop queued audio
public SpeechService(AppSettings settings, ILogger logger) { _settings = settings; _logger = logger; }
// Caller audio -> ElevenLabs
public async Task AppendAudioBuffer(AudioMediaBuffer buffer)
{
if (!_started)
{
if (_connecting) return; // a connect attempt is already in flight
_connecting = true;
try { await Connect(); _started = true; }
catch (Exception ex) { _logger.Error(ex, "ElevenLabs connect failed; retry on next frame"); return; }
finally { _connecting = false; }
}
if (_ws?.State != WebSocketState.Open || buffer.Length <= 0) return;
var pcm = new byte[buffer.Length];
Marshal.Copy(buffer.Data, pcm, 0, (int)buffer.Length);
var msg = JsonSerializer.Serialize(new { user_audio_chunk = Convert.ToBase64String(pcm) });
await _ws.SendAsync(Encoding.UTF8.GetBytes(msg), WebSocketMessageType.Text, true, default);
}
private async Task Connect()
{
_ws = new ClientWebSocket();
// ElevenLabsOrigin: wss://api.elevenlabs.io, or a residency host (.eu./.in./.sg.)
var url = $"{_settings.ElevenLabsOrigin}/v1/convai/conversation?agent_id={_settings.ElevenLabsAgentId}";
await _ws.ConnectAsync(new Uri(url), default);
await _ws.SendAsync(Encoding.UTF8.GetBytes(
JsonSerializer.Serialize(new { type = "conversation_initiation_client_data" })),
WebSocketMessageType.Text, true, default);
_ = Task.Run(ReceiveLoop);
}
private async Task ReceiveLoop()
{
var buf = new byte[32768]; var sb = new StringBuilder();
while (_ws.State == WebSocketState.Open)
{
sb.Clear(); WebSocketReceiveResult r;
do { r = await _ws.ReceiveAsync(buf, default); sb.Append(Encoding.UTF8.GetString(buf, 0, r.Count)); }
while (!r.EndOfMessage);
using var doc = JsonDocument.Parse(sb.ToString());
var type = doc.RootElement.GetProperty("type").GetString();
if (type == "audio") // ElevenLabs audio -> call
Emit(Convert.FromBase64String(doc.RootElement
.GetProperty("audio_event").GetProperty("audio_base_64").GetString()));
else if (type == "ping")
await _ws.SendAsync(Encoding.UTF8.GetBytes(JsonSerializer.Serialize(new {
type = "pong", event_id = doc.RootElement.GetProperty("ping_event").GetProperty("event_id").GetInt32() })),
WebSocketMessageType.Text, true, default);
else if (type == "interruption") // barge-in: drop any agent audio still queued
FlushMedia?.Invoke(this, EventArgs.Empty);
}
}
// slice PCM into 20 ms / 640-byte frames the media platform expects
private void Emit(byte[] pcm)
{
var all = new List(); long tick = DateTime.Now.Ticks;
for (int off = 0; off < pcm.Length; off += 640)
{
var frame = new byte[640];
Array.Copy(pcm, off, frame, 0, Math.Min(640, pcm.Length - off));
all.AddRange(Utilities.CreateAudioMediaBuffers(frame, tick, _logger));
tick += 20 * 10000;
}
if (all.Count > 0) SendMediaBuffer?.Invoke(this, new MediaStreamEventArgs { AudioMediaBuffers = all });
}
}
```
Both sides are PCM 16 kHz mono, so it’s a base64 passthrough — set the agent to `pcm_16000`. On an ElevenLabs `interruption` (barge-in), the bridge raises `FlushMedia`; wire that to your media stream so it drops any queued `AudioMediaBuffer`s, otherwise the agent keeps talking over the caller. The full message reference is in the [WebSocket docs](/guides/elevenagents-libraries-web-sockets). End-of-call hangup and warm transfer are covered in the sections below.
:::callout{intent="note"}
The URL in `Connect()` reaches a **public** agent. For a private agent, request a short-lived signed URL server-side — `GET /v1/convai/conversation/get-signed-url?agent_id=...` with your API key — and connect to the returned URL instead. On [data residency](/guides/overview-administration-data-residency), set `ElevenLabsOrigin` to your residency host (`wss://api.eu.residency.elevenlabs.io`, `.in.`, or `.sg.`) — signed-URL requests use the matching `https://` host.
:::
## Step 4 — Make it callable in Teams
1. **Enable Calling** on the Azure Bot’s Teams channel and set the **calling webhook** to `https://YOUR_FQDN/api/calling`:
```bash
az bot msteams create -g $RG -n el-teams-agent-bot \
--enable-calling --calling-web-hook "https://YOUR_FQDN/api/calling"
```
In the portal this lives at your Azure Bot resource → **Channels** → **Microsoft Teams** → **Calling** tab:
Azure Bot → Channels — the connected Microsoft Teams channel
Microsoft Teams channel → Calling — calling enabled with the bot's webhook
2. Build a **Teams app manifest** with `bots[0].supportsCalling: true` and the bot’s app ID, then sideload it (**Apps → Manage your apps → Upload a custom app**), or publish it org-wide without the UI: `New-TeamsApp -DistributionMethod organization -Path ./bot-app.zip` (MicrosoftTeams PowerShell module).
Search the app by name in Teams and call it — the bot answers and the ElevenLabs agent speaks.
A live 1:1 call with the agent — note Transfer and Consult in the call toolbar
:::callout{intent="note"}
No phone number or resource account is needed for 1:1 call-by-name — those are only for PSTN dial-in. `Calls.AccessMedia.All` is what enables the raw-audio bridge.
:::
## Text chat (same bot)
The same Azure Bot can also answer **text** in Teams — so users can either call the agent or chat with it. Calling and messaging are independent channels on the bot: the calling webhook handles voice, and a Bot Framework **messaging endpoint** (`/api/messages`) handles chat.
Chatting with the same bot in Teams
Point the bot’s messaging endpoint at whichever host serves it (the media bot, or any other service — it doesn’t have to be the Windows VM):
```bash
az bot update -g $RG -n el-teams-agent-bot --endpoint "https://YOUR_FQDN/api/messages"
```
Implement the endpoint with the Bot Framework SDK and relay each message to the agent in **text mode** over the same conversation WebSocket used for voice — send a [`user_message`](/guides/elevenagents-customization-events-client-to-server-events) event, read the [`agent_response`](/guides/elevenagents-customization-events-client-events) event. First enable the **first message** field under the agent’s [overrides](/guides/elevenagents-customization-personalization-overrides) settings — the code below overrides it to empty so the reply is the answer to the user’s message rather than the agent’s greeting:
```csharp title="ChatBot.cs — Teams text chat -> ElevenLabs (text mode)"
public class ChatBot : ActivityHandler
{
private readonly AppSettings _settings;
public ChatBot(AppSettings settings) => _settings = settings;
protected override async Task OnMessageActivityAsync(
ITurnContext turn, CancellationToken ct)
{
var reply = await AskAgent(turn.Activity.Text, ct);
await turn.SendActivityAsync(MessageFactory.Text(reply), ct);
}
private async Task AskAgent(string text, CancellationToken ct)
{
using var ws = new ClientWebSocket();
var url = $"{_settings.ElevenLabsOrigin}/v1/convai/conversation?agent_id={_settings.ElevenLabsAgentId}";
await ws.ConnectAsync(new Uri(url), ct);
// Suppress the agent's greeting: with no override, the first agent_response is the
// configured first message, not the answer to this user_message.
await Send(ws, new
{
type = "conversation_initiation_client_data",
conversation_config_override = new { agent = new { first_message = "" } },
}, ct);
await Send(ws, new { type = "user_message", text }, ct);
var buf = new byte[16384]; var sb = new StringBuilder();
while (ws.State == WebSocketState.Open)
{
sb.Clear(); WebSocketReceiveResult r;
do { r = await ws.ReceiveAsync(buf, ct); sb.Append(Encoding.UTF8.GetString(buf, 0, r.Count)); }
while (!r.EndOfMessage);
using var doc = JsonDocument.Parse(sb.ToString());
switch (doc.RootElement.GetProperty("type").GetString())
{
case "agent_response":
return doc.RootElement.GetProperty("agent_response_event")
.GetProperty("agent_response").GetString();
case "ping":
await Send(ws, new { type = "pong", event_id = doc.RootElement
.GetProperty("ping_event").GetProperty("event_id").GetInt32() }, ct);
break;
}
}
return "Sorry, I couldn't reach the agent.";
}
private static Task Send(ClientWebSocket ws, object msg, CancellationToken ct) =>
ws.SendAsync(Encoding.UTF8.GetBytes(JsonSerializer.Serialize(msg)),
WebSocketMessageType.Text, true, ct);
}
```
Register it the standard way (a `CloudAdapter`, the bot via `AddTransient()`, and a `/api/messages` controller), and add chat scopes to the manifest’s bot entry:
```json
"bots": [
{ "botId": "YOUR_APP_ID", "supportsCalling": true, "scopes": ["personal", "team", "groupChat"] }
]
```
:::callout{intent="note"}
The snippet opens a fresh conversation per message, so each turn is independent. For chat **memory**, keep one WebSocket open per Teams `conversation.id` (reuse it across turns) and reap idle sessions — the agent then remembers earlier messages in that chat. The `first_message` override must be enabled under the agent’s [overrides](/guides/elevenagents-customization-personalization-overrides) settings — the server **closes the conversation** if a disallowed override is sent. If you can’t enable it, omit the override and instead discard the first `agent_response` of each session (the greeting) and return the next one.
:::
:::callout{intent="tip"}
If chat replies never arrive, enable the **`agent_response`** [client event](/guides/elevenagents-customization-events-client-events) in the agent’s **Advanced** settings — text responses are delivered through that event.
:::
## End of call
When ElevenLabs ends the conversation (its **End Call** tool closes the WebSocket), hang up the Teams leg:
```csharp
await this.Call.DeleteAsync(); // after a short delay so the goodbye audio finishes
```
## Warm transfer to a human
The agent fires a custom `transfer_to_human` client tool; the bot **invites a Teams user** into the live call (consultative add), then steps back:
```csharp
var target = new IdentitySet { User = new Identity { Id = humanObjectId } };
await this.Call.Participants.InviteAsync(target, replacesCallId: null);
// suppress the end-call hangup while transferring, and mute the bot
```
:::callout{intent="tip"}
Consultative transfer (`replacesCallId`) requires both parties be Teams users in the **same tenant**; PSTN transfer targets require an application instance. To brief the human first, pass a `reason` parameter from the agent and play it to the human before bridging.
:::
## Troubleshooting
:::accordion{title="MediaPlatform needs a system with at least 2 cores"}
The VM has only one physical core. Resize to ≥ 2 physical cores (e.g. `D4s_v3`) and restart.
:::
:::accordion{title="Unable to load DLL 'NativeMedia'"}
Install the **VC++ Redistributable** (`vcredist140`) and the **Server-Media-Foundation** Windows feature, then restart the bot.
:::
:::accordion{title="Incoming call returns 500 / call won't connect"}
The EchoBot port-null bug on 443 — patch `HttpHelpers.SetAbsoluteUri` (see Step 3). Also confirm the cert is CA-signed and reachable on 443.
:::
:::accordion{title="Calling the bot says 'we couldn't connect you'"}
Confirm Calling is enabled on the Teams channel with the correct `/api/calling` webhook, the Graph `Calls.AccessMedia.All` permission is consented, and ports 443/8445/9441 are open on both the NSG and the Windows firewall. If calling **used to work and stopped**, check the bot process is still running on the VM — Task Scheduler’s default 72-hour execution limit kills it a few days after boot (see the warning in Step 3).
:::
## Useful links
- [Calls & meetings bots overview](https://learn.microsoft.com/en-us/microsoftteams/platform/bots/calls-and-meetings/calls-meetings-bots-overview)
- [Real-time media concepts](https://learn.microsoft.com/en-us/microsoftteams/platform/bots/calls-and-meetings/real-time-media-concepts)
- [Register a calling bot](https://learn.microsoft.com/en-us/microsoftteams/platform/bots/calls-and-meetings/registering-calling-bot)
- [microsoft-graph-comms-samples (EchoBot)](https://github.com/microsoftgraph/microsoft-graph-comms-samples)
- [call: transfer (consultative)](https://learn.microsoft.com/en-us/graph/api/call-transfer)
- [Agent WebSocket protocol](/guides/elevenagents-libraries-web-sockets)
## Related pages
- [Administration](./administration-index.md)
- [API reference](./api-reference-index.md)
- [Changelog](./changelog-index.md)
- [ElevenAgents](./elevenagents-index.md)
- [ElevenAPI](./elevenapi-index.md)
- [ElevenCreative](./elevencreative-index.md)
- [ElevenLabs Documentation Docs](../index.md)
- [General Troubleshooting FAQ](./troubleshooting-index.md)
- [General Website FAQ](./website-index.md)
- [Help Center](./help-center-2-index.md)
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