---
title: "Start session (with traffic split)"
method: POST
path: "/v4/project/{projectID}/session"
tags: ["Session", "Public-Docs"]
---

# Start session (with traffic split)

`POST /v4/project/{projectID}/session`

Start a new conversation and get a session key for interacting with an agent, routing traffic based on its [traffic split](/documentation/deploy/environments/traffic-split).

## Path parameters

- `projectID` string, required — The ID of the target Voiceflow project. You can find it in the settings for your agent.

## Request body

- object
  - `userID` string, required — Unique ID for the user. If a session already exists for this user, the existing session will end and a new session will be created with a new session key.

## Response `200`

- object
  - `sessionKey` string, required — A session-scoped authentication key. Pass this as the `authorization` header when calling the interact endpoints.

---

[API](https://skmtc.dev/voiceflow/apis/general-runtime.md) · [All operations](https://skmtc.dev/voiceflow/apis/general-runtime/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/voiceflow/general-runtime/revisions/6b1c4f778c56/schema)