> ## Documentation Index
> Fetch the complete documentation index at: https://docs.modulate.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Velma

> Velma is an audio-native voice intelligence model over REST or WebSocket — surface behaviors and risks in voice conversations using pre-built or custom detectors.

It analyzes audio signals alongside the words to surface behaviors and risks in voice conversations — fraud, customer churn, compliance violations, and more. Configure it with 150+ pre-built behaviors or define your own in plain language, either the built-in `default` or a JSON `BatchConfig` — and behaviors can be pulled from a catalog of ready-made presets.

|                                                    | Batch                                                   | Streaming                                            |
| -------------------------------------------------- | ------------------------------------------------------- | ---------------------------------------------------- |
| **Use case**                                       | Analyze a complete recording                            | Analyze a live conversation in real time             |
| **Protocol**                                       | HTTP POST (multipart upload)                            | WebSocket                                            |
| **Configuration**                                  | `config` form field — `default` or a JSON `BatchConfig` | First text frame — `default` or a JSON `BatchConfig` |
| **Output**                                         | Full `BatchResponse` after processing                   | Discrete events emitted as results are produced      |
| **Max file size**                                  | 100 MB                                                  | — (streaming)                                        |
| **Transcription + diarization**                    | ✓                                                       | ✓                                                    |
| **Conversation-type & participant-role inference** | ✓                                                       | ✓                                                    |
| **Behavior detection (with presets)**              | ✓                                                       | ✓                                                    |
| **Topics, topic sentiment, summary**               | ✓                                                       | ✓                                                    |

For a side-by-side comparison with the other Modulate capabilities, see [Which API should I use?](/guides/which-api).

## Configuration

Both endpoints take the same configuration: either the literal string `default` to use the built-in configuration, or a JSON `BatchConfig` describing the conversation types, participant roles, behaviors, STT options, and which aggregate outputs (topics, sentiments, summary) to produce. The full `BatchConfig` schema is rendered on the [Batch](/api-reference/velma/batch) reference.

Behaviors can be specified inline or referenced from a catalog of presets using the `preset:<identifier>` syntax. List the available presets with [List behavior presets](/api-reference/velma/presets).

## Authentication

Batch uses the `X-API-Key` header. Streaming uses an `api_key` query parameter at connection time. See [Authentication and rate limits](/guides/authentication).