---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/api/errors/80616#article
headline: "80616: Unsupported Identifier Type For Session Mode"
url: https://www.twilio.com/docs/api/errors/80616
inLanguage: en
dateModified: 2026-06-08T12:04:59.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# 80616: Unsupported Identifier Type For Session Mode

Log Level: ERROR

## Description

This error occurs when you add a Participant `identifier` that does not match the Proxy Session `mode`. Proxy Sessions support `message-only`, `voice-only`, and `voice-and-message`. Proxy also supports non-phone channel identifiers for messaging use cases, but those identifiers must be used in a messaging flow that matches the Session mode.

### Possible causes

* You created a `voice-only` or `voice-and-message` Session, then tried to add a channel or chat identifier instead of a phone number as the Participant `identifier`.
* You are building a messaging app or chat integration, but the Session was not created as `message-only`. Twilio's channel-based examples use channel identifiers in `message-only` Sessions.
* You reused an `identifier` or `proxyIdentifier` from a channel-based messaging setup in a Session that is expected to handle voice traffic. Proxy separates voice-capable and message-only session behavior through the Session `mode`.

### Possible solutions

* Check the Session `mode` before you add Participants. Use `message-only` for chat or messaging channel identifiers. Use `voice-only` or `voice-and-message` only when the Participant can be represented by a phone number.
* If you are using Proxy with messaging channels, pass the messaging app or chat value as the Participant `identifier` and use the channel or contact address as `proxyIdentifier` in a `message-only` Session.
* If the Session needs to support calls, recreate or update the flow so the Participant uses a phone number identifier, then verify your Proxy number pool includes numbers with the Voice or SMS capabilities required for that Session.

#### Additional resources

* [Session Resource](/docs/proxy/api/session)
* [Participant](/docs/proxy/api/participant)
* [Using Proxy with Channels](/docs/proxy/channels)