docs(phone-numbers): free Vapi numbers cannot be ported out

fern/customization/voice-pipeline-configuration.mdx

@@ -217,8 +217,8 @@ Uses AI models to analyze speech patterns, context, and audio cues to predict wh
     - **livekit**: Advanced model trained on conversation data (English only)
     - **vapi**: VAPI-trained model (non-English conversations or LiveKit alternative)
 
-    **Audio-based providers:**
-    - **krisp**: Audio-based model analyzing prosodic features (intonation, pitch, rhythm)
+    **Custom providers:**
+    - **custom-endpointing-model**: Sends each endpointing decision to your own server, which returns a `timeoutSeconds` value
 
     **Audio-text based providers:**
     - **deepgram-flux**: Deepgram's latest transcriber model with built-in conversational speech recognition. Use `flux-general-en` for English-only conversations or `flux-general-multi` for multilingual conversations.
@@ -235,7 +235,7 @@ Uses AI models to analyze speech patterns, context, and audio cues to predict wh
 - **AssemblyAI**: Use when AssemblyAI is already your transcriber provider and you want integrated end-of-turn detection
 - **LiveKit**: English conversations where Deepgram is not the transcriber of choice.
 - **Vapi**: Non-English conversations with default stop speaking plan settings
-- **Krisp**: Non-English conversations with a robustly configured stop speaking plan
+- **Custom endpointing model**: When your own server should decide the endpointing timeout for each turn
 
 ### Deepgram Flux configuration
 
@@ -357,31 +357,52 @@ The system continuously analyzes the latest user message and applies the first m
 - Scenarios requiring predictable, rule-based endpointing behavior
 - Fallback option when other smart endpointing providers aren't suitable
 
-### Krisp threshold configuration
+### Custom endpointing model configuration
 
-Krisp's audio-base model returns a probability between 0 and 1, where 1 means the user definitely stopped speaking and 0 means they're still speaking.
-
-**Threshold settings:**
-
-- **0.0-0.3:** Very aggressive detection - responds quickly but may interrupt users mid-sentence
-- **0.4-0.6:** Balanced detection (default: 0.5) - good balance between responsiveness and accuracy
-- **0.7-1.0:** Conservative detection - waits longer to ensure users have finished speaking
+Sends each endpointing decision to your own server instead of a built-in model. Vapi POSTs the current transcript to `server.url`; your server responds with a `timeoutSeconds` value, the number of seconds to wait before considering the user's turn finished. The timeout resets each time a new transcript is received.
 
 **Configuration example:**
 
 ```json
 {
   "startSpeakingPlan": {
     "smartEndpointingPlan": {
-      "provider": "krisp",
-      "threshold": 0.5
+      "provider": "custom-endpointing-model",
+      "server": {
+        "url": "https://your-server.com/endpointing"
+      }
     }
   }
 }
 ```
 
-**Important considerations:**
-Since Krisp is audio-based, it always notifies when the user is done speaking, even for brief acknowledgments. Configure the stop speaking plan with appropriate `acknowledgementPhrases` and `numWords` settings to handle backchanneling properly.
+**Request sent to your server:**
+
+```json
+{
+  "message": {
+    "type": "call.endpointing.request",
+    "messages": [
+      {
+        "role": "user",
+        "message": "Hello, how are you?",
+        "time": 1234567890,
+        "secondsFromStart": 0
+      }
+    ]
+  }
+}
+```
+
+**Expected response:**
+
+```json
+{
+  "timeoutSeconds": 0.5
+}
+```
+
+If `server` is not provided, the request is sent to `assistant.server`, then `org.server` if that isn't set either.
 
 ### Assembly turn detection
 
@@ -665,35 +686,6 @@ User Interrupts → Assistant Audio Stopped → backoffSeconds Blocks All Output
 
 **Optimized for:** Text-based endpointing with longer timeouts for different speech patterns and international support.
 
-### Audio-based endpointing (Krisp example)
-
-```json
-{
-  "startSpeakingPlan": {
-    "waitSeconds": 0.4,
-    "smartEndpointingPlan": {
-      "provider": "krisp",
-      "threshold": 0.5
-    }
-  },
-  "stopSpeakingPlan": {
-    "numWords": 2,
-    "voiceSeconds": 0.2,
-    "backoffSeconds": 1.0,
-    "acknowledgementPhrases": [
-      "okay",
-      "right",
-      "uh-huh",
-      "yeah",
-      "mm-hmm",
-      "got it"
-    ]
-  }
-}
-```
-
-**Optimized for:** Non-English conversations with robust backchanneling configuration to handle audio-based detection limitations.
-
 ### Audio-text based endpointing (Assembly example)
 
 ```json

fern/phone-numbers/free-telephony.mdx

@@ -55,6 +55,7 @@ This guide details how to create free phone numbers on the Vapi platform, which
 - **Free Vapi numbers are for US national use.** They cannot make international calls. For international use, [import a number from another provider](/phone-numbers/import-twilio).
 - **Outbound calling not supported.** Free Vapi numbers are inbound only. Import a number from a supported telephony provider to make outbound calls. See [Outbound calling](/calls/outbound-calling).
 - **Outbound Campaigns require an imported number.** Free Vapi numbers cannot be used to launch [Outbound Campaigns](/outbound-campaigns/quickstart).
+- **Porting out is not supported.** A free Vapi number is provisioned on Vapi's own carrier accounts, not a carrier account you hold, so there is no account number or port-out PIN to request and the number cannot be ported to another carrier.
 - **You are responsible for lawful use.** Obtain the required consent before making outbound calls and follow applicable calling, telemarketing, and do-not-call rules. See the [TCPA consent guide](/tcpa-consent) and [Vapi Terms of Service](https://vapi.ai/terms-of-service).
 
 ### Frequently Asked Questions
@@ -69,4 +70,7 @@ This guide details how to create free phone numbers on the Vapi platform, which
     <Accordion title="Does free mean calls cost nothing?" icon="phone" iconType="regular">
         No. The Vapi-managed phone number is free, but calls and other platform usage still consume credits and are billed according to Vapi pricing.
     </Accordion>
+    <Accordion title="Can I port a free Vapi number out to my own carrier account?" icon="phone" iconType="regular">
+        No. Free Vapi numbers are provisioned on Vapi's own carrier accounts, so there is no account number or port-out PIN Vapi can provide. To manage a number under your own carrier account, buy or port it into that provider directly, then [import it into Vapi](/phone-numbers/import-twilio).
+    </Accordion>
 </AccordionGroup>