June 8, 2025

Eleven v3 (alpha): Released Eleven v3 (alpha), our most expressive Text to Speech model, as a research preview.

Custom voice settings in multi-voice: Added support for configuring individual voice settings per supported voice in multi-voice agents, allowing fine-tuned control over stability, speed, similarity boost, and streaming latency for each voice.
Silent transfer to human in Twilio: Added backend configuration support for silent (cold) transfer to number in the Twilio native integration, enabling seamless handoff without announcing the transfer to callers.
Batch calling retry and cancel: Added support for retrying outbound calls to phone numbers that did not respond during a batch call, along with the ability to cancel ongoing batch operations for better campaign management.
LLM pinning: Added support for versioned LLM models with explicit checkpoint identifiers
Custom LLM headers: Added support for passing custom headers to custom LLMs
Fixed issue in non-latin languages: Fixed an issue causing some conversations in non latin alphabet languages to fail.

View API changes

New Endpoints

Batch Calling:
- Cancel batch call - Cancel a running batch call and set all recipients to cancelled status
- Retry batch call - Retry a batch call by setting completed recipients back to pending status
Knowledge Base RAG:
- Get document RAG indexes - Get information about all RAG indexes of a knowledge base document
- Delete document RAG index - Delete a specific RAG index for a knowledge base document
- RAG index overview - Get total size and information of RAG indexes used by knowledge base documents

Supported Voices:
- Agent configuration - Added optimize_streaming_latency, stability, speed, and similarity_boost parameters for per-voice TTS customization
Transfer to Number:
- Agent configuration - Added enable_client_message parameter to control whether a message is played to the client during transfer
Knowledge Base:
- Knowledge base documents now use supported_usages instead of prompt_injectable for better usage mode control
- RAG index creation now returns enhanced response model with usage information
Custom LLM:
- Agent configuration - Added request_headers parameter for custom header configuration
Widget Configuration:
- Agent platform settings - Added comprehensive styles configuration for widget appearance customization
LLM:
- Added support for versioned LLM models with explicit version identifiers