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

# Preview a pending compose update

> Returns current and pending docker compose file and pre-launch script for diffing before applying an update.



## OpenAPI

````yaml /openapi.json get /api/v1/apps/{app_id}/pending-updates/{vm_uuid}/{compose_hash}/preview
openapi: 3.1.0
info:
  title: Phala Cloud API
  version: 0.1.0
servers:
  - url: https://cloud-api.phala.com
security: []
tags:
  - name: CVMs
    description: Confidential Virtual Machine (CVM) lifecycle management on Phala Network
  - name: Apps
    description: App template management and CVM deployment from app blueprints
  - name: Webhooks
    description: Manage webhook endpoints and monitor delivery history
  - name: SSH Keys
    description: SSH public key management for CVM access
  - name: KMS
    description: >-
      Key Management Service — key derivation, on-chain anchoring, and
      inspection
  - name: Instance Types
    description: Available hardware configurations for CVM deployment
  - name: Attestations
    description: Remote attestation and TEE verification endpoints
paths:
  /api/v1/apps/{app_id}/pending-updates/{vm_uuid}/{compose_hash}/preview:
    get:
      tags:
        - Apps
        - apps-pending-updates
      summary: Preview a pending compose update
      description: >-
        Returns current and pending docker compose file and pre-launch script
        for diffing before applying an update.
      operationId: >-
        get_pending_update_preview_api_v1_apps__app_id__pending_updates__vm_uuid___compose_hash__preview_get
      parameters:
        - name: app_id
          in: path
          required: true
          schema:
            type: string
            title: App Id
            description: Hex app identifier
          description: Hex app identifier
        - name: vm_uuid
          in: path
          required: true
          schema:
            type: string
            title: Vm Uuid
            description: VM UUID
          description: VM UUID
        - name: compose_hash
          in: path
          required: true
          schema:
            type: string
            description: Compose hash of the pending update
            title: Compose Hash
          description: Compose hash of the pending update
      responses:
        '200':
          description: Preview data
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/PendingUpdatePreview'
        '401':
          description: Not authenticated
        '404':
          description: App or pending update not found
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
components:
  schemas:
    PendingUpdatePreview:
      properties:
        current_docker_compose:
          anyOf:
            - type: string
            - type: 'null'
          title: Current Docker Compose
        pending_docker_compose:
          anyOf:
            - type: string
            - type: 'null'
          title: Pending Docker Compose
        current_pre_launch_script:
          anyOf:
            - type: string
            - type: 'null'
          title: Current Pre Launch Script
        pending_pre_launch_script:
          anyOf:
            - type: string
            - type: 'null'
          title: Pending Pre Launch Script
      type: object
      title: PendingUpdatePreview
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
              - type: string
              - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
      type: object
      required:
        - loc
        - msg
        - type
      title: ValidationError

````