Hey there, We're using a Telnyx-purchased phone number with VAPI's Voice API Application integration (api.vapi.ai/telnyx/inbound_call webhook). On outbound calls placed via VAPI through this number, we're seeing 3-4 seconds of additional per-turn latency compared to identical calls placed through a VAPI-native number. The inbound calls using the Telnyx number work fine as well and do not have this latency issue. For outbound calls the delay is consistent and happens between every conversational turn in the call, not just at setup. These calls are solely within the US and the only allowed destination for the Telnyx outbound voice profile is US. Looking at the Latency Summary in VAPI the breakdown does not show a significant difference from an inbound call, but it looks as though the human responses are coming through about 2-3 seconds delayed. Has anyone dealt with this before? Is this just a limitation of outbound calls with Telnyx or a possible misconfiguration? Appreciate any help and advice.

Hi, can you please share call id for same

Yes, here is one - 019e941e-9a97-7000-b889-c7fe1402a137 I can do a longer call if necessary. In the call recording I can see my responses are logged about 4 seconds late, when in reality I was responding immediately after the agent stopped talking. I believe this is the cause of the perceived delay (user responds immediately, agent gets it about 3-4 seconds late, then additional 1200 ms for transcription/tts/stt pipeline)

Hi, I’ve worked with VAPI and Telnyx integrations and can help troubleshoot this. A consistent 3–4 second delay on outbound calls usually points to media routing, RTP handling, or Telnyx voice profile configuration rather than the AI pipeline itself. I’d be happy to review the call logs, latency metrics, and setup to pinpoint the bottleneck and help reduce the delay. @sewerboy

Hi, As checked and investigated, we can see that the audio is being received late, which causes it to be processed and forwarded late as well. This is why you're experiencing a delay of approximately 3–4 seconds before the agent receives the audio. From our review, the delay appears to be occurring in the incoming audio stream itself. For reference, we've attached the customer specific relevant audio observations from our investigation. The assistant is responding as soon as it receives the audio, so the delay is happening before the audio reaches the assistant. It's possible that this is related to the telephony provider or network path. https://storage.vapi.ai/019e941e-9a97-7000-b889-c7fe1402a137-1780601578061-b2d0ace4-b3c9-48ed-b22a-457ceb542287-mono.wav Thank you.

This makes sense. I will troubleshoot it from the telephony side. Thank you for your help!

Thank you, have a great day