---
title: "Volunteer claim-and-launch for a day-of no-show (MED-1006 AC8)"
method: POST
path: "/api/participant/sessions/{sessionId}/volunteer-start"
tags: ["Waiting Room"]
---

# Volunteer claim-and-launch for a day-of no-show (MED-1006 AC8)

`POST /api/participant/sessions/{sessionId}/volunteer-start`

## Request

- Base URL: `https://api.production.yourmedley.com`
- URL: `https://api.production.yourmedley.com/api/participant/sessions/{sessionId}/volunteer-start`
- Auth: HTTP bearer

The single "I'll lead" action. Atomically claims leadership
(sets session_leader_id to the caller) and launches the session
(scheduled → in_progress) for a peer-led Live Session Delivery session
in the no-show window. Exactly one starter wins; `became_leader: false`
means another member won the race and the caller should land in the
participant active view (AC9 — not an error).

Authorization: peer-led + Live Session Delivery enabled, within the
volunteer window, the caller has not opted out (did not decline the
volunteer call / "Keep waiting"), and is a current group member.

## Path parameters

- `sessionId` string, uuid, required

## Response `200`

Claim-and-launch result

- object
  - `success` boolean
  - `data` object
    - `became_leader` boolean: true if this caller won the launch race
    - `session_id` string, uuid
    - `cohort_id` string, uuid

## Other responses

- `401`: Unauthorized
- `403`: Not eligible (opted out
- `404`: Session not found OR live_session_delivery flag off
- `409`: Volunteer window not open

---

[API](https://skmtc.dev/withmedley/apis/medley-api.md) - [All operations](https://skmtc.dev/withmedley/apis/medley-api/llms.txt) - [OpenAPI document](https://skmtc.dev/withmedley/apis/medley-api/revisions/40aaac5ca6bd?raw)