# Capture Session

> Start a session at the beginning of a conversation

Call once per conversation. Reuse `session_id` on every event that follows.

## Body

| Field | Type | Required | Description |
| - | - | - | - |
| `session_id` | `string` (UUID) | Required | Session UUID. Reuse on every event in this conversation. |
| `user_data` | `object` | Required | End-user identity. Must contain `user_id`. |
| `metadata` | `object` | Optional | Free-form session metadata. |
| `timestamp` | `integer` (ms) | Optional | Unix time in ms when the session began. Defaults to server time. |
| `client_config` | `string` | Optional | Free-form client/SDK label. |

## Verify

After creating a session and sending at least one event, open **Events** in Voxmith and confirm the `session_id` appears on the event.

## Troubleshooting

* `session_id` must be a UUID.
* `user_data.user_id` is required.
* Reuse the same `session_id` for every event in the conversation.

## Next steps

* [Capture an event](/capture-event): add activity to the session you created.
* [Authentication](/authentication): review organization routing and API access.
* [Ingestion errors](/errors): troubleshoot rejected requests.