Hi, I'm experiencing an issue with delayed agent responses using a Telnyx SIP Trunk number. The number was successfully created using the same values as the vapi tutorial: https://docs.vapi.ai/advanced/sip/telnyx * The assistant works correctly on Twilio or Vapi numbers, so it's not about the assistant configuration. Agent answers are real-time when calls are made with these providers * The recording on the Vapi logs has the agent's answers as expected, but those answers get an 8-10 second delay to be heard on the line * The logs on the Telnyx side show the connection was correctly made An example of this problem is call d2473f96-a453-4358-b203-5cf5bd02df16. The recording has an immediate response from the agent, but in Telnyx, it was heard after a few seconds of silence. No errors shown on the vapi logs. Has someone encountered a similar problem or knows how to solve it? https://cdn.discordapp.com/attachments/1415463659165061220/1415463659836018719/image.png?ex=68c34cc2&is=68c1fb42&hm=1abcd5297dcc2aafc32798eef033c76952106c99724def700fccbde203804b1e& https://cdn.discordapp.com/attachments/1415463659165061220/1415463660213501972/image.png?ex=68c34cc2&is=68c1fb42&hm=b432ef190108ce914b9fdf7dae0485b3b0ddab8af53bf4517366788da1185cad& https://cdn.discordapp.com/attachments/1415463659165061220/1415463660805160990/image.png?ex=68c34cc2&is=68c1fb42&hm=09cb1dcfe4848926c9f54af8f9e0a8946724dd3051c80966a04976ff24fa5dda& https://cdn.discordapp.com/attachments/1415463659165061220/1415463661287243926/image.png?ex=68c34cc2&is=68c1fb42&hm=c5d5741c73d71d8d33f1cc5dea7438c2d589d2482f40bad3d1647dcda640fb31&

Suggestion: Double-check your Telnyx SIP trunk's codec settings to ensure only one common codec (e.g.,

G711U

or

OPUS

) is enabled on both Vapi and Telnyx, as having multiple codecs enabled can cause negotiation delays. Try disabling all but one supported codec and test again:

# Example: Enable only G711U
- OPUS: Disabled
- G729: Disabled
- G711A: Disabled
- G711U: Enabled

This can help eliminate codec negotiation as the source of the delay. If the issue persists, review any recent SIP trunk or webhook configuration changes as intermittent SIP misconfigurations can also cause such symptoms ([source](https://discord.com/channels/1211482211119796234/1372358449761091584)). Source: - [Vapi outbound call not triggering (Discord)](https://discord.com/channels/1211482211119796234/1372358449761091584)

@Vapi Support Bot It didn't work. I changed the config for only one option to be enabled, but the delay still remains. I tried leaving OPUS first, and then changed it to G711U, but the problem persist.

Thank you for confirming the codec changes. To help narrow down the cause of the delay, could you let me know if there have been any recent changes to your Telnyx SIP trunk or webhook configurations just before this issue started? Even small changes can sometimes introduce unexpected delays. Source: - [Vapi outbound call not triggering (Discord)](https://discord.com/channels/1211482211119796234/1372358449761091584)

@Vapi Support Bot No changes. The connection is new. Just to clarify, the call is triggering, but the assistant voice response has a delay.

Hello, Thanks for reaching out to us.We are sorry for the inconvenience. There are several key configuration points that could affect audio latency: 1. Verify your SIP trunk configuration: - Check that port 5060 is correctly set - Ensure FQDN is set to

sip.vapi.ai

- Verify inbound settings are properly configured - Check outbound authentication settings 2. For outbound voice profile settings: - Make sure you've configured the appropriate country settings - The documentation recommends creating separate SIP Trunks for each country you're making calls to - Check your outbound voice profile settings in Telnyx portal 3. Check your Telnyx credential configuration in Vapi:

{
  "provider": "byo-sip-trunk",
  "gateways": [
    {
      "ip": "sip.telnyx.com",
      "inboundEnabled": false
    }
  ],
  "outboundAuthenticationPlan": {
    "authUsername": "YOUR_SIP_USERNAME",
    "authPassword": "YOUR_SIP_PASSWORD",
    "sipRegisterPlan": {
      "realm": "sip.telnyx.com"
    }
  }
}

Since you're seeing consistent 8-10 second delays specifically with Telnyx (but not with other providers), you should: 1. Compare your configuration with these reference settings 2. Check network latency between Telnyx and Vapi servers 3. Monitor SIP packet timing in Telnyx logs 4. Report this issue to support with: - Telnyx configuration details - Comparison of timing between recording and actual call

I just completed a job on that, I could help you with fixing this right on call with speed

please let us know and we’ll be happy to step in and assist further.

I worked on something similar 3days back on telnyx, user was having a 12seconds delay instead and issue got fixed right on our consultation call. If you’re serious about getting this issue I might be of great help..

We’re here if you need any more assistance.