Voicemail Detection Override — Calls Ending Before...
# supportg
Growifai
02/19/2026, 4:25 AMVoicemail Detection Override — Calls Ending Before Voicemail Tool Can Fire (part 1)
Assistant ID: 3b28bf5e-04f8-412d-84bb-faac27d87047
Org ID: 5940c407-7a4a-426c-b589-9b73072111a5
Phone Number ID: 08e4b8a3-0a07-4975-8337-601837472d93
Problem
Outbound calls that hit voicemail are being terminated with endedReason: voicemail before our voicemail tool has a chance to fire and leave a message. This happens even with voicemailDetection completely removed from the assistant configuration.
What We've Tried (in order)
Vapi detection (voicemailDetection.provider: vapi) — Tried multiple times, same results.
Twilio AMD (voicemailDetection.provider: twilio, machineDetectionTimeout: 5) — Gloria spoke her firstMessage over the VM greeting every time. 3/4 calls ended as silence-timed-out, not even classified as voicemail.
Vapi detection (voicemailDetection.provider: vapi) — Tried multiple times, same results.
Voicemail tool (type: voicemail, beepDetectionEnabled: true) — Added to assistant with strong prompt instructions to detect VM greetings and trigger the tool. Tool works correctly when it gets the chance (see passing calls below).
Removed hardcoded firstMessage — Set firstMessage: "" and firstMessageMode: assistant-speaks-first-with-model-generated-message to give detection time before Gloria speaks.
Disabled voicemailDetection entirely — Set enabled: false, then fully removed the voicemailDetection object from the assistant.
Cleared voicemailMessage — Removed the static TTS message to prevent it from competing with the voicemail tool.
Evidence
Calls where something kills the call before the tool fires (ended as voicemail with no AI response):
019c72d3-a424-744c-8b2c-e7fccaf46d27 — VM greeting transcribed fully, Gloria never spoke, call terminated. voicemailDetection was completely removed from assistant at this point.
019c72c2-81b3-7006-8fde-9f76245a89a8 — Same pattern.
019c72c6-9485-733f-b062-25b81f2d293c — Gloria only got out "Hi." before call was killed.
Growifai
02/19/2026, 4:25 AMVoicemail Detection Override — Calls Ending Before Voicemail Tool Can Fire (part 2)
Current Assistant Config
voicemailDetection: fully removed (not present on assistant object)
voicemailMessage: cleared ("")
firstMessage: cleared ("")
firstMessageMode: assistant-speaks-first-with-model-generated-message
Voicemail tool (c7268b65-9b3f-4633-a426-0611e8357b44): beepDetectionEnabled: true
Prompt includes explicit voicemail detection instructions at highest priority
Question
Something at the platform level appears to be detecting voicemail and terminating the call (endedReason: voicemail) independently of the voicemailDetection assistant setting. This prevents the voicemail tool from ever executing.
Is there a platform-level voicemail detection that operates outside the assistant config? How do we disable it so the voicemail tool is the sole handler?
I have been trying to fix this for two weeks - and has caused major consternation with our clients.
I also tried to post this in discord support channel, though it find that I don’t have permission to post there.
Please advise ASAP.
Growifai
02/19/2026, 8:12 PMWhy are outbound calls being ended with endedReason: voicemail before the assistant produces a response turn?
Is there transport-layer voicemail detection independent of the assistant config?
Can it be fully disabled?
As I've been trying to get voicemail detection to function, now the assistant isn't engaging live callers!
Growifai
02/19/2026, 8:24 PMWe turned assistant-speaks-first back on because real user's weren't being spoken to
Look at the most recent call - you can hear the user vmail pick-up and she doesn't leave a message
3:19 PM
GET /v2/call
Success
Request
Response
json
{
"method" "GET",
"endpoint" "GET /v2/call",
"body" {
"limit" 1,
"sortOrder" "DESC",
"assistantId" "3b28bf5e-04f8-412d-84bb-faac27d87047"
}
}
Good — this one tells us something important.
Call 019c778b-1a48
Transcript:
Copy
User: Your call has been forwarded to voice mail...
There is no AI message at all no greeting.
That means:
Gloria never spoke
Voicemail tool never fired
Call ended before the assistant layer produced any turn.
Since we are back on assistant-speaks-first, she should have spoken immediately.
The fact that she didn’t means:
Call is being classified & terminated at the transport layer before the assistant is allowed to speak.
This confirms:
It is NOT assistant-waits-for-user
It is NOT the voicemail tool
It is NOT firstMessageMode
It is NOT prompt logic
This is carrier / Vapi outbound orchestration behavior
The moment the system hears:
“Your call has been forwarded to voice mail"
It is auto-ending the call with endedReason: voicemail
And it is doing so before your assistant layer runs
What This Means
platform-level voicemail short‑circuit happening
Even though:
voicemailDetection is removed
voicemailMessage is cleared
Voicemail tool exists
Beep detection is on
The transport engine is still intercepting and ending the call.
This is outside assistant configuration control.
The Only Honest Conclusion
You cannot force the voicemail tool to fire until Vapi disables the transport-layer voicemail auto-termination for your assistant or phone number.
This is 100% something they must toggle on VAPI side.
019c778b-1a48-7ff9-acae-6d29b52d7e0d
Assistant never got a turn. No AI greeting. No voicemail tool. Call was terminated immediately after voicemail greeting began.
That is the smoking gun.
Growifai
02/21/2026, 10:48 PM@VAPI Tech please help!