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

# Start a checkout session

> Starts a subscription upgrade by creating a checkout session for the named plan and
returns a hosted checkout URL to redirect the customer to. Workspace admin only. The
plan_slug must reference an active plan that has a configured price (otherwise 400);
the actual plan provisioning happens asynchronously once payment completes. Returns
503 if billing is not configured.

## Returns a Stripe redirect URL

This doesn't change the subscription directly — it creates a Stripe Checkout session and returns `{ "url": "https://checkout.stripe.com/..." }`. **Redirect the customer to that URL** to complete payment. The new plan is provisioned asynchronously after Stripe confirms payment, so it appears shortly afterward, not in this response. Admin only; returns `503` if billing isn't configured.


## OpenAPI

````yaml POST /v1/api/billing/checkout
openapi: 3.1.0
info:
  title: HQ API
  description: >-
    Public HTTP API for HQ. Authenticate with a Personal Access Token
    (`Authorization: Bearer hq_pat_...`) for server-side integrations, or an
    OAuth 2.1 authorization-code + PKCE flow for browser apps acting on a user's
    behalf. Both grant from the same resource:action scope vocabulary; an
    endpoint's required scope is listed under its `security`.
  license:
    name: Apache-2.0
    identifier: Apache-2.0
  version: 1.0.0
servers:
  - url: https://api.hq.zone
    description: HQ API (production)
security: []
tags:
  - name: me
    description: The signed-in user's own account
  - name: conversations
    description: Conversations and their messages
  - name: documents
    description: The content-addressed documents library
  - name: schedules
    description: Scheduled prompts and recurring tasks
  - name: agents
    description: Agents, their skills and integrations
  - name: memory
    description: What the assistant remembers (L5 governance)
  - name: tokens
    description: Personal Access Token management
  - name: billing
    description: Usage and billing
  - name: notifications
    description: In-app notification center
  - name: admin
    description: Workspace administration
  - name: integrations
    description: Workspace integrations (Slack, MCP, skills)
  - name: onboarding
    description: New-workspace onboarding wizard
  - name: auth
    description: Sign-in, sessions, and OAuth
paths:
  /v1/api/billing/checkout:
    post:
      tags:
        - billing
      summary: Start a checkout session
      description: >-
        Starts a subscription upgrade by creating a checkout session for the
        named plan and

        returns a hosted checkout URL to redirect the customer to. Workspace
        admin only. The

        plan_slug must reference an active plan that has a configured price
        (otherwise 400);

        the actual plan provisioning happens asynchronously once payment
        completes. Returns

        503 if billing is not configured.
      operationId: checkout
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CheckoutReq'
        required: true
      responses:
        '200':
          description: Stripe Checkout URL
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/UrlResp'
        '400':
          description: Plan has no Stripe price
        '403':
          description: Admin role required
        '503':
          description: Billing not configured
      security:
        - bearer_pat:
            - admin
        - oauth2:
            - admin
components:
  schemas:
    CheckoutReq:
      type: object
      required:
        - plan_slug
      properties:
        plan_slug:
          type: string
    UrlResp:
      type: object
      required:
        - url
      properties:
        url:
          type: string
  securitySchemes:
    bearer_pat:
      type: http
      scheme: bearer
      bearerFormat: hq_pat
      description: 'Personal Access Token. Send as `Authorization: Bearer hq_pat_...`.'
    oauth2:
      type: oauth2
      flows:
        authorizationCode:
          authorizationUrl: https://app.hq.zone/v1/oauth/authorize
          tokenUrl: https://api.hq.zone/v1/oauth/token
          refreshUrl: https://api.hq.zone/v1/oauth/token
          scopes:
            admin: Administer the workspace (users, settings, integrations)
            agents:read: View the agents in your workspace
            agents:write: Create and configure agents
            billing:read: View usage and billing information
            conversations:read: Read your conversations and their messages
            conversations:write: Start conversations and send messages on your behalf
            documents:read: Read your documents library
            documents:write: Upload and manage documents in your library
            memory:read: Read what the assistant remembers about you
            memory:write: Correct or delete what the assistant remembers
            schedules:read: View your scheduled tasks
            schedules:write: Create and manage scheduled tasks
            tables:read: Read your tables and their rows
            tables:write: Create tables and add, edit, or delete rows

````