> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.vapi.ai/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.vapi.ai/_mcp/server.

# What's New: Week of July 27, 2026

## New Models

1. **Anthropic Claude Sonnet 5**: Anthropic's Claude Sonnet 5 is now available as a model for assistants.

2. **OpenAI GPT-5.5 "Instant"**: OpenAI's [GPT-5.5](/providers/model/openai) (`gpt-5.5` and `chat-latest`) is now available as a model for assistants.

3. **OpenAI GPT-5.6 Models**: OpenAI's [GPT-5.6](/providers/model/openai) models (`sol`, `terra`, and `luna`) are now available for assistants.

4. **Inworld TTS-2**: Inworld's [TTS-2](/providers/voice/inworld) voice is now available for assistants.

## SIP Call Transfers

1. **SIP Warm Transfer Audio**: Warm [call transfers](/call-forwarding) on SIP calls now play hold audio to the operator and a completion sound (`transferCompleteAudioUrl`) when the transfer connects.