Add changelog updates for 2025-03-13 (#255)

Author: quantstruct-bot

fern/changelog/2025-03-13.mdx

@@ -0,0 +1,103 @@
+## New Workflows API, Telnyx Phone Number Support, Voice Options, and much more
+
+1. **Workflows Replace Blocks**: The API has migrated from blocks to workflows with new `/workflow` endpoints. [Introduction to Workflows](https://docs.vapi.ai/workflows)
+You can now use [`UpdateWorkflowDTO`](https://api.vapi.ai/api#:~:text=UpdateWorkflowDTO) where conversation components (`Say`, `Gather`, `ApiRequest`, `Hangup`, `Transfer` nodes) are explicitly connected via edges to create directed conversation flows.
+
+<Accordion title='Example workflow (simplified)'>
+   ```json
+   {
+     "name": "Customer Support Workflow",
+     "nodes": [
+       {
+         "id": "greeting",
+         "type": "Say",
+         "text": "Hello, welcome to customer support. Do you need help with billing or technical issues?"
+       },
+       {
+         "id": "menu",
+         "type": "Gather",
+         "options": ["billing", "technical", "other"]
+       },
+       {
+         "id": "billing",
+         "type": "Say",
+         "text": "I'll connect you with our billing department."
+       },
+       {
+         "id": "technical",
+         "type": "Say",
+         "text": "I'll connect you with our technical support team."
+       },
+       {
+         "id": "transfer_billing",
+         "type": "Transfer",
+         "destination": {
+           "type": "number",
+           "number": "+1234567890"
+         }
+       },
+       {
+         "id": "transfer_technical",
+         "type": "Transfer",
+         "destination": {
+           "type": "number",
+           "number": "+1987654321"
+         }
+       }
+     ],
+     "edges": [
+       {
+         "from": "greeting",
+         "to": "menu"
+       },
+       {
+         "from": "menu",
+         "to": "billing",
+         "condition": {
+           "type": "logic",
+           "liquid": "{% if input == 'billing' %} true {% endif %}"
+         }
+       },
+       {
+         "from": "menu",
+         "to": "technical",
+         "condition": {
+           "type": "logic",
+           "liquid": "{% if input == 'technical' %} true {% endif %}"
+         }
+       },
+       {
+         "from": "billing",
+         "to": "transfer_billing"
+       },
+       {
+         "from": "technical",
+         "to": "transfer_technical"
+       }
+     ]
+   }
+   ```
+</Accordion>
+
+2. **Telnyx Phone Number Support**: Telnyx is now available as a phone number provider alongside Twilio and Vonage. 
+    - Use the [`TelnyxPhoneNumber`](https://api.vapi.ai/api#:~:text=TelnyxPhoneNumber), [`CreateTelnyxPhoneNumberDTO`](https://api.vapi.ai/api#:~:text=CreateTelnyxPhoneNumberDTO), and [`UpdateTelnyxPhoneNumberDTO`](https://api.vapi.ai/api#:~:text=UpdateTelnyxPhoneNumberDTO) schemas with [`/phone-number`](https://api.vapi.ai/api#/Phone%20Numbers) endpoints to create and update Telnyx phone numbers.
+    - The `Call.phoneCallProviderId` now includes Telnyx's `callControlId` alongside Twilio's `callSid` and Vonage's `conversationUuid`.
+
+3. **New Voice Options**: 
+   - **Vapi Voices**: New Vapi voices - `Elliot`, `Rohan`, `Lily`, `Savannah`, and `Hana` 
+   - **Hume Voice**: New provider with `octave` model and customizable voice settings
+   - **Neuphonic Voice**: New provider with `neu_hq` (higher quality) and `neu_fast` (faster) models
+
+4. **New Cerebras Model**: [`CerebrasModel`](https://api.vapi.ai/api#:~:text=CerebrasModel) Supports `llama3.1-8b` and `llama-3.3-70b` models
+   
+5. **Enhanced Transcription**:
+   - **New Providers**: [ElevenLabs](https://api.vapi.ai/api#:~:text=ElevenLabsTranscriber) and [Speechmatics](https://api.vapi.ai/api#:~:text=SpeechmaticsTranscriber) transcribers now available.
+   - **DeepgramTranscriber Numerals**: New `numerals` option converts spoken numbers to digits (e.g., "nine-seven-two" → "972")
+
+6. **Improved Voicemail Detection**: You can now use multiple provider implementations for `assistant.voicemailDetection` (Google, OpenAI, Twilio). OpenAI implementation allows configuring detection duration (5-60 seconds, default: 15).
+
+7. **Smart Endpointing Upgrade**: Now supports LiveKit as an alternative to Vapi's custom-trained model in [`StartSpeakingPlan.smartEndpointingEnabled`](https://api.vapi.ai/api#:~:text=StartSpeakingPlan). LiveKit only supports English but may offer different endpointing characteristics.
+
+8. **Observability with Langfuse**: New `assistant.observabilityPlan` property allows integration with Langfuse for tracing and monitoring of assistant calls. Configure with [LangfuseObservabilityPlan](https://api.vapi.ai/api#:~:text=LangfuseObservabilityPlan).
+
+9. **More Credential Support**: Added support for Cerebras, Google, Hume, InflectionAI, Mistral, Trieve, and Neuphonic credentials in `assistant.credentials`