FUSE Health Checkout Sessions API

openapi: 3.2.0
info:
  title: FUSE Brand API (External) Checkout Sessions API
  version: 1.0.0
  description: 'Server-to-server API exposing the FUSE brand-admin surface so a single brand/tenant can build its own admin frontend. Every request is authenticated with an API key bound to exactly one clinic; all data is auto-scoped to that clinic and cannot reach another brand''s data. Isolation is enforced by application-layer clinic filtering on every query.


    COVERAGE: 218 operations across 180 paths, and EVERY ONE is available to every brand. There is no per-clinic enablement step. What governs access: your API key and its scopes, the clinic the key belongs to (every read and write is filtered to it), your plan''s entitlements for the two commercially-gated areas — Affiliates (`AFFILIATES_TIER_REQUIRED`) and CRM Connect (`CRM_TIER_REQUIRED`) — and rate limits.


    AUTH: the external /api/v1 surface uses an API key (`x-api-key`, ApiKeyAuth). Key management (/api-keys) and /auth/signin live at the API root and use a brand-admin JWT (BearerAuth); /auth/signin itself is unauthenticated.


    SCOPES: every key carries scopes; read-only is the default and mutating endpoints require the `write` scope (403 INSUFFICIENT_SCOPE otherwise). Keys default to a 1-year expiry.


    RATE LIMITING: every endpoint may additionally return `429 Too Many Requests` with a `Retry-After` header; 429 is not repeated on each operation below.


    PLATFORM FIELDS: product cost, fees, pharmacy routing, doctor questions and FUSE approvals are set by FUSE, not by the brand. Any write (POST/PUT/PATCH/DELETE) whose JSON body carries one of those fields at any depth — for example `pharmacyPrice`, `shippingFeeUsd`, `coolerFeeUsd`, `pharmacyId`, `preferredPharmacyId`, `pharmacyProvider`, `requiredDoctorQuestions`, `facilitationFee`, `placeholderPrice`, `legalBusinessName`, `isTemplate` or `tenantManagerApproved` — is refused with `403 PLATFORM_FIELD`, whose `fields` array lists the offending paths; remove them and resend. (One exception: `POST /api/v1/products` still accepts the `pharmacyPrice` its schema requires, and ignores it.) 403 PLATFORM_FIELD is not repeated on each operation below.'
servers:
- url: https://api-dev.fusehealth.com
  description: Development
- url: https://api.fusehealth.com
  description: Production
security:
- ApiKeyAuth: []
tags:
- name: Checkout Sessions
paths:
  /api/v1/checkout/sessions:
    post:
      tags:
      - Checkout Sessions
      summary: Create a checkout session for one of the clinic's own programs
      operationId: postApiV1CheckoutSessions
      description: Creates the session bookkeeping row for the FUSE-hosted, iframe-isolated intake+checkout component. Computes and stores questionnaireVersionHash (the legal audit trail — sha256 over the program's questionnaire content at creation time) and returns an opaque sessionToken + embedUrl the brand mounts in an iframe. This is the ONE endpoint a PUBLISHABLE key (`fuse_pk_…`) may call — every other endpoint on this surface, including GET /checkout/sessions/{id}, 403s a publishable key with `KEY_KIND_NOT_ALLOWED`. Publishable keys are additionally hard rate-limited on this route.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CheckoutSessionCreate'
      responses:
        '201':
          description: Created
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                  data:
                    $ref: '#/components/schemas/CheckoutSessionCreated'
        '400':
          description: Bad request (missing/invalid programId, metadata, or successUrl) or NO_QUESTIONNAIRE_CONFIGURED
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorEnvelope'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '403':
          description: Insufficient scope (INSUFFICIENT_SCOPE) — read-only key attempted a write
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorEnvelope'
        '404':
          $ref: '#/components/responses/NotFound'
        '429':
          $ref: '#/components/responses/TooManyRequests'
  /api/v1/checkout/sessions/{id}:
    get:
      tags:
      - Checkout Sessions
      summary: Get checkout session status (own-clinic only)
      operationId: getApiV1CheckoutSessionsById
      description: 'Returns session status + orderId (once completed) — NEVER intake questions or answers. Secret keys only: a publishable key gets 403 `KEY_KIND_NOT_ALLOWED` here too, even though it authenticated successfully.'
      parameters:
      - name: id
        in: path
        required: true
        schema:
          type: string
          format: uuid
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                type: object
                properties:
                  success:
                    type: boolean
                  data:
                    $ref: '#/components/schemas/CheckoutSessionStatus'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '403':
          description: Publishable key used on a route it may not call (KEY_KIND_NOT_ALLOWED)
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorEnvelope'
        '404':
          $ref: '#/components/responses/NotFound'
components:
  schemas:
    CheckoutSessionCreate:
      type: object
      required:
      - programId
      properties:
        programId:
          type: string
          format: uuid
          description: Must belong to the key's own clinic (404 otherwise).
        metadata:
          type: object
          additionalProperties: true
          description: 'Brand-supplied data, stored verbatim and capped at 16 KiB (DB CHECK constraint plus model-layer validation). FUSE never displays or acts on it, with one exception: the marketing-attribution keys lead_id (or legacy leadId), utm_source, utm_medium, utm_campaign, utm_content, gclid and fbclid are copied onto the resulting order and echoed on the intake.started webhook. Every other key is ignored.

            '
        successUrl:
          type:
          - string
          - 'null'
          format: uri
          description: 'Absolute https:// URL only — http/javascript:/data: and relative paths are rejected. Navigates the checkout IFRAME after payment, never the brand''s page — move your own page from the fuse:completed event instead.

            '
    CheckoutSessionStatus:
      type: object
      properties:
        sessionId:
          type: string
          format: uuid
        status:
          type: string
          enum:
          - created
          - in_progress
          - completed
          - expired
          - abandoned
        orderId:
          type:
          - string
          - 'null'
          format: uuid
          description: Set once the embed flow completes checkout.
        expiresAt:
          type: string
          format: date-time
    CheckoutSessionCreated:
      type: object
      properties:
        sessionId:
          type: string
          format: uuid
        sessionToken:
          type: string
          description: 'Opaque, HMAC-signed, short-lived (~30 min) credential for the embed page (not this API-key-authenticated surface) to load and render the session''s questionnaire.

            '
        embedUrl:
          type: string
          format: uri
          description: Mount this in an iframe on the brand's page.
        expiresAt:
          type: string
          format: date-time
    ErrorEnvelope:
      description: 'Failure shape. NOTE: most modules use `message`; programs endpoints use `error`. Read both. Some errors include a machine-readable `code` and/or a `data` payload.'
      type: object
      properties:
        success:
          type: boolean
          enum:
          - false
        message:
          type: string
        error:
          type: string
        code:
          type: string
        data: {}
  responses:
    NotFound:
      description: Resource not found (or not owned by the key's clinic)
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorEnvelope'
    TooManyRequests:
      description: Rate limit exceeded for this key. Respect the `Retry-After` header. Applies to every endpoint.
      headers:
        Retry-After:
          schema:
            type: integer
          description: Seconds to wait before retrying
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorEnvelope'
    Unauthorized:
      description: Missing, invalid, inactive, or expired API key (or JWT)
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/ErrorEnvelope'
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: header
      name: x-api-key
      description: Clinic-scoped API key. Keep server-side; never expose in a browser or app bundle.
    BearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT
      description: FUSE brand-admin JWT (from POST /auth/signin). Used ONLY by the key-management endpoints — the external /api/v1 surface never accepts JWTs, and API keys never work on key management.