I am wondering whether Vapi provides any features or options to manage an excess number of inbound Twilio calls through to the Vapi agent such as an inbound call queue system? For example, if I have a Vapi call concurrency limit of 10 calls and I have 10 calls already occurring at once and an 11th inbound call is made to my Twilio number which routes to our Vapi agent, does the Vapi agent or Vapi server provide any out of the box queueing system, or do we need to somehow introduce logic and state management on our end to manage this ourselves before the Twilio call is routed to the Vapi agent? Building on this example from a technical execution pov - the twilio number instead of it making a POST request to the Vapi server endpoint (https://api.vapi.ai/twilio/inbound_call) it would hit our server end point first (e.g https://myserver.com/inbound) and we would respond back to Twilio with something like this....

const twimlResponse = `
    <Response>
      <Start>
        <Stream url="${vapiWsUrl}" />
      </Start>
      <Say>Connecting you now...</Say>
    </Response>
  `;

the above code is a twiML action that tells twilio to connect the call to a bidirectiona;l stream using the vapi WSS transport as the connecting url. Can you please advise if that is a viable way of using the Vapi WSS transport in conjunction with Twilio a call?

Vapi does not provide a built-in inbound call queueing system for Twilio calls. If your concurrency limit is reached, you will need to implement your own logic—such as using Twilio's queueing features or custom server-side state management—to handle excess calls before routing them to Vapi. This ensures callers are queued or managed appropriately when your Vapi agent is at capacity. Sources: - [Vapi Phone Calling Documentation](https://docs.vapi.ai/phone-calling) - [Vapi & Twilio Call Handling](https://docs.vapi.ai/calls/call-handling-with-vapi-and-twilio)

@Jeremy L In a short answer - NO. First of all, Twilio's

<Start><Stream>

is a uni-directional stream, while the correct stream will be

<Connect>

- however, putting that aside, Twilio's queuing mechanism requires that VAPI be actively registered with Twilio's endpoints - which it doesn't. You can create a "Virtual Queuing" mechanism by using a platform like Cloudonix (or similar) and building a "concurrency control and routing" mechanism, that will put calls into a waiting pattern, when your VAPI concurrently hits the limit. If you would like, DM me and I'll show you how you can create something thing like that.

Vapi does not provide a built-in inbound call queueing system for Twilio calls. To manage excess inbound calls, you should implement your own queuing logic—such as using Twilio's queueing features or a custom server endpoint—to hold calls until your Vapi agent has available capacity. Only then should you connect the call to Vapi. For example, your Twilio webhook can check current concurrency and respond with a waiting message or queue logic before forwarding to Vapi:

xml
<Response>
  <Say>Please hold, all agents are busy.</Say>
  <!-- Add Twilio queue logic here -->
</Response>

[See Vapi Phone Calling Documentation](https://docs.vapi.ai/phone-calling) Sources: - [Vapi Phone Calling Documentation](https://docs.vapi.ai/phone-calling) - [Vapi & Twilio Call Handling](https://docs.vapi.ai/calls/call-handling-with-vapi-and-twilio)

Hey @Nir S (CEO/Founder @Cloudonix) thanks for the response. Yes you're right - it should be . So for abit more context we have actually our own internal queueing system we have setup, so we won't be relying on Twilio's inbuilt system. The only dependency on the integration is that we're able to connect the twilio call resource to the vapi agent by connecting the Twilio call to the vapi agent wss url at a later time when the queue has cleared up for the next call. Hence the reason why i wanted to ask whether connecting the Vapi agent wss url in the twiML action is actually viable. I don't know if Vapi's server would be able to support the usage of their agent WSS url in that way with Twilio.

If your objective is to "hold people in a queue" in order to exceed your VAPI concurrent limit, you can do it using Cloudonix - no WSS or streams required.

**Vapi does not provide a built-in inbound call queueing system for Twilio calls**—you must implement your own queuing logic before routing calls to Vapi ([Vapi Phone Calling Documentation](https://docs.vapi.ai/phone-calling)). Regarding your approach: the documentation and community responses indicate that using Twilio's

<Start><Stream>

to connect directly to a Vapi WSS URL is **not supported**—Twilio's stream is uni-directional, and Vapi is not registered for this type of endpoint ([Vapi & Twilio Call Handling](https://docs.vapi.ai/calls/call-handling-with-vapi-and-twilio)). The recommended integration is via webhooks and server logic, not direct WSS streaming. Could you clarify if you are looking for a fully bi-directional audio stream between Twilio and Vapi, or are you open to using webhook-based integration as described in the Vapi documentation? Sources: - [Vapi Phone Calling Documentation](https://docs.vapi.ai/phone-calling) - [Vapi & Twilio Call Handling](https://docs.vapi.ai/calls/call-handling-with-vapi-and-twilio)

No, we don't have any inbound call queue.

Thanks Sahil. Can you explain what happens when someone attempts to call the Vapi assistant and we're already at our max line concurrency limit?

@Jeremy L simple, the call is dropped and the person will hear a busy tone.

Vapi does not support connecting Twilio calls to a Vapi agent via a WSS URL using TwiML

<Start><Stream>

or

<Connect>

. Instead, queue calls on your server and only initiate a new Vapi call when ready. For example, respond to Twilio with a holding message until your queue clears:

xml
<Response>
  <Say>Please hold, all agents are busy.</Say>
  <!-- Add your queue logic here -->
</Response>

When ready, use the standard Vapi call initiation flow to connect the caller. [See Vapi & Twilio Call Handling](https://docs.vapi.ai/calls/call-handling-with-vapi-and-twilio) Sources: - [Vapi & Twilio Call Handling](https://docs.vapi.ai/calls/call-handling-with-vapi-and-twilio) - [Vapi Phone Calling Documentation](https://docs.vapi.ai/phone-calling)

thanks