> ## Documentation Index > Fetch the complete documentation index at: https://docs.member.dev/llms.txt > Use this file to discover all available pages before exploring further. # Launch Hub Handoff > Start a hub handoff for a verified User whose hub Contact link is proven. Writes a one-use launch that snapshots the User, hub, destination and purpose. The hub page registers its browser against it before any code exists. A team owner with no link yet is linked here to the hub's owner or admin Contact when both emails are verified and identical and the User's email proof is newer than any proof on the Contact. When only that last rule fails, the answer is 403 contact_identity_confirmation_sent: a one-time link is emailed to the shared address. meta.email_sent is false when this hub's launch in the last 5 minutes already answered with one; meta.expires_at is when the live link expires and meta.resend_available_at is when opening the hub again can send a new one. An address gets at most 3 of these emails in 15 minutes across all Users and hubs; a launch over that limit sends nothing, but it and the launches after it answer exactly as a send would (the same email_sent and times), so the answer never reveals other accounts' emails. The wording is conditional for that reason. The signed-in User completes it with POST /api/contact-auth/identity-link-confirmations. Every other refusal, including an account already linked elsewhere, is 403 contact_identity_link_required, with no email. ## OpenAPI ````yaml /openapi/mio-openapi.json post /api/v1/contact-auth/handoff/launches openapi: 3.1.0 info: description: >- Production API reference for Membership.io. Use the authored guides for workflows and the generated endpoint pages for exact parameters and schemas. title: Membership.io API version: 0.1.0 servers: - description: Production url: https://api.member.dev security: - bearerAuth: [] paths: /api/v1/contact-auth/handoff/launches: post: tags: - contact-auth summary: Launch Hub Handoff description: >- Start a hub handoff for a verified User whose hub Contact link is proven. Writes a one-use launch that snapshots the User, hub, destination and purpose. The hub page registers its browser against it before any code exists. A team owner with no link yet is linked here to the hub's owner or admin Contact when both emails are verified and identical and the User's email proof is newer than any proof on the Contact. When only that last rule fails, the answer is 403 contact_identity_confirmation_sent: a one-time link is emailed to the shared address. meta.email_sent is false when this hub's launch in the last 5 minutes already answered with one; meta.expires_at is when the live link expires and meta.resend_available_at is when opening the hub again can send a new one. An address gets at most 3 of these emails in 15 minutes across all Users and hubs; a launch over that limit sends nothing, but it and the launches after it answer exactly as a send would (the same email_sent and times), so the answer never reveals other accounts' emails. The wording is conditional for that reason. The signed-in User completes it with POST /api/contact-auth/identity-link-confirmations. Every other refusal, including an account already linked elsewhere, is 403 contact_identity_link_required, with no email. operationId: contact_auth.post_contact_auth_post_contact_auth_handoff_launches requestBody: content: application/vnd.api+json: schema: $ref: '#/components/schemas/HubHandoffLaunchEnvelope' required: true responses: '201': content: application/vnd.api+json: schema: $ref: '#/components/schemas/HubHandoffLaunchResponse' description: Successful Response '422': content: application/vnd.api+json: schema: $ref: '#/components/schemas/HTTPValidationError' description: Validation Error security: - HTTPBearer: [] components: schemas: HubHandoffLaunchEnvelope: additionalProperties: false properties: data: $ref: '#/components/schemas/HubHandoffLaunchRequestResource' required: - data title: HubHandoffLaunchEnvelope type: object HubHandoffLaunchResponse: additionalProperties: false properties: data: $ref: '#/components/schemas/HubHandoffLaunchResource' required: - data title: HubHandoffLaunchResponse type: object HTTPValidationError: properties: detail: items: $ref: '#/components/schemas/ValidationError' title: Detail type: array title: HTTPValidationError type: object HubHandoffLaunchRequestResource: additionalProperties: false properties: attributes: $ref: '#/components/schemas/_HubHandoffLaunchRequestAttributes' type: const: hub_handoff_launches title: Type type: string required: - type - attributes title: HubHandoffLaunchRequestResource type: object HubHandoffLaunchResource: additionalProperties: false properties: attributes: $ref: '#/components/schemas/HubHandoffLaunchAttributes' id: title: Id type: string type: const: hub_handoff_launches default: hub_handoff_launches title: Type type: string required: - id - attributes title: HubHandoffLaunchResource type: object ValidationError: properties: ctx: title: Context type: object input: title: Input loc: items: anyOf: - type: string - type: integer title: Location type: array msg: title: Message type: string type: title: Error Type type: string required: - loc - msg - type title: ValidationError type: object _HubHandoffLaunchRequestAttributes: additionalProperties: false properties: destination_path: description: >- Canonical hub URL path. Include /{encoded hub slug} as the first segment for shared-host and custom-domain handoff requests. maxLength: 2048 minLength: 1 title: Destination Path type: string hub_id: maxLength: 36 minLength: 1 title: Hub Id type: string purpose: default: view description: >- view: redeem on the hub's canonical origin (its active custom domain, otherwise the platform hub host). preview: always redeem on the platform hub host, so the session works inside the admin's preview frame. enum: - view - preview title: Purpose type: string required: - hub_id - destination_path title: _HubHandoffLaunchRequestAttributes type: object HubHandoffLaunchAttributes: additionalProperties: false properties: deadline: description: Every step of this handoff must finish before it. format: date-time title: Deadline type: string expires_at: format: date-time title: Expires At type: string launch_id: description: >- One-use launch id. Carry it only in URL fragments, never a query string. title: Launch Id type: string purpose: enum: - view - preview title: Purpose type: string start_url: description: Open this in the tab or frame that will hold the hub session. title: Start Url type: string target_origin: title: Target Origin type: string required: - launch_id - start_url - target_origin - purpose - expires_at - deadline title: HubHandoffLaunchAttributes type: object securitySchemes: bearerAuth: bearerFormat: JWT or mio_sk API key description: >- Send platform JWTs, contact JWTs, or team API keys as `Authorization: Bearer `. scheme: bearer type: http HTTPBearer: scheme: bearer type: http ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.