> 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.

# Background Speech Denoising, Cartesia Transcriber, Workflow Enhancements, and Call Error Handling

1. **Background Speech Denoising Plan**: You can now enhance call quality by configuring advanced background speech denoising options using the new [`assistant.backgroundSpeechDenoisingPlan.smartDenoisingPlan`](https://api.vapi.ai/api#:~:text=SessionPaginatedResponse-,Assistant,-AssistantPaginatedResponse) (default: `false`), which replaces the previous `backgroundDenoisingEnabled` setting.

#### Enable Smart Denoising (Krisp)

Use the `SmartDenoisingPlan` to filter out background speech and noise using [Krisp technology](https://krisp.ai/).

#### Customize Fourier Denoising

Fine-tune noise reduction with the new `FourierDenoisingPlan` for more control over audio clarity.

> **Info**
>
> Smart and Fourier denoising can be combined for optimal results. Order of precedence: Smart denoising, then Fourier denoising.

2. **Workflow Server Property**: Workflows now support a [`server`](https://api.vapi.ai/api#:~:text=TrieveKnowledgeBaseImport-,Workflow,-UpdateWorkflowDTO) property, allowing you to specify a server URL to receive webhook callbacks for workflow events directly.

3. **New Workflow Models**: You can now integrate Google's LLMs or custom models into your workflows by specifying [`Google`](https://api.vapi.ai/api#:~:text=WorkflowGoogleModel) or [`Custom LLM`](https://api.vapi.ai/api#:~:text=WorkflowCustomModel) in your workflow model settings. Select your model under [Model Settings](https://dashboard.vapi.ai/workflows#:~:text=Model%20Settings)

![Workflow Google Custom LLM](/_fern-img/9a62ece92326433ae0b9e8992e4c9894c20c46066d3930efa8e2ddbaa2737588.webp)

4. **Enhanced Error Reporting for Cartesia Services**: A new `endedReason` value `pipeline-error-cartesia-502-server-error` has been added to help you identify and handle specific errors related to Cartesia server issues.

5. **Enhanced Error Handling and Status Enums**: We've added new error enums and status codes to help you better handle and debug call-related issues:

   * **VAPI Fault Errors**: Detect specific VAPI-related errors during call start using `call.start.error-vapifault-get-org` and `call.start.error-vapifault-get-subscription`

   * **Subscription Status Errors**: Identify subscription-related issues with new enums:
     * `call.start.error-subscription-frozen` (replaces `unknown-error`)
     * `call.start.error-subscription-insufficient-credits`

   * **Call Completion Statuses**: Track how calls are completed with new enums:
     * `call.in-progress.twilio-completed-call`
     * `call.in-progress.sip-completed-call`

   * **In-Call Error Detection**: Handle specific errors during active calls using enums like `call.in-progress.error-vapifault-chat-pipeline-failed-to-start`