> ## Documentation Index > Fetch the complete documentation index at: https://docs.slng.ai/llms.txt > Use this file to discover all available pages before exploring further. # Preview version restore > Compute what restoring this version would change, without applying anything. The preview returns the changed fields, any configuration issues, and the hashes needed to accept the restore: copy `acceptance_hash` from the preview and `candidate_hash`, `resource_hash`, and `dependency_hash` from its `preparation` object into the accept request. The request body is optional; when `restore_historical_name` is set here it must be sent with the same value on accept. ## OpenAPI ````yaml /api-reference/agents/agents.oas.yaml post /v1/agents/{agent_id}/versions/{version_number}/restore/preview openapi: 3.0.3 info: title: SLNG Voice Agents API version: 1.0.0 description: > Public API for managing Voice Agents, dispatching outbound calls, and creating web (non-telephony) sessions. Base URL: `https://api.agents.slng.ai` contact: name: SLNG Support email: support@slng.ai servers: - url: https://api.agents.slng.ai description: Production security: - bearerAuth: [] tags: - name: Agents description: Voice agent CRUD. - name: Versions description: Agent configuration version history and restore. - name: Calls description: Call dispatch and status. - name: Sessions description: Web (non-telephony) sessions. paths: /v1/agents/{agent_id}/versions/{version_number}/restore/preview: parameters: - $ref: '#/components/parameters/AgentIdPath' - $ref: '#/components/parameters/VersionNumberPath' post: tags: - Versions summary: Preview version restore description: > Compute what restoring this version would change, without applying anything. The preview returns the changed fields, any configuration issues, and the hashes needed to accept the restore: copy `acceptance_hash` from the preview and `candidate_hash`, `resource_hash`, and `dependency_hash` from its `preparation` object into the accept request. The request body is optional; when `restore_historical_name` is set here it must be sent with the same value on accept. operationId: previewAgentVersionRestore requestBody: required: false content: application/json: schema: $ref: '#/components/schemas/AgentConfigRestoreOptions' responses: '200': description: >- Restore preview. Check `state` — `ready` previews can be accepted; `failed` previews list blocking `issues`. content: application/json: schema: $ref: '#/components/schemas/AgentConfigRestorePreview' '202': description: > The restored config references organisation resources that require resolution before it can be activated. Retry the preview after the delay indicated by the `Retry-After` header. headers: Retry-After: schema: type: integer description: Suggested delay in seconds before retrying. content: application/json: schema: $ref: '#/components/schemas/AgentConfigRestorePreview' '401': $ref: '#/components/responses/UnauthorizedError' '403': $ref: '#/components/responses/ForbiddenError' '404': $ref: '#/components/responses/NotFoundError' '409': description: Conflict. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: history-unsafe: summary: Historical config cannot be activated safely value: detail: The historical AgentConfig cannot be activated safely. '422': $ref: '#/components/responses/ValidationError' '500': $ref: '#/components/responses/InternalServerError' components: parameters: AgentIdPath: name: agent_id in: path required: true schema: $ref: '#/components/schemas/UUID' description: Voice agent ID. VersionNumberPath: name: version_number in: path required: true schema: type: integer minimum: 1 description: Agent config version number. schemas: AgentConfigRestoreOptions: type: object additionalProperties: false properties: restore_historical_name: type: boolean default: false description: | When `true`, also restore the agent name recorded in the version. By default the agent keeps its current name. AgentConfigRestorePreview: type: object required: - state - restore_kind - target_version - target_version_id - current_version - current_version_id - current_config_hash - target_config_hash properties: state: type: string enum: - ready - preparing - failed description: > - `ready`: the restore can be accepted with the returned hashes. - `preparing`: referenced organisation resources are still being resolved; retry the preview. - `failed`: the restore is blocked by the listed `issues`. restore_kind: type: string enum: - exact target_version: type: integer description: Version number being restored. target_version_id: $ref: '#/components/schemas/UUID' current_version: type: integer nullable: true description: The agent's latest version number. current_version_id: $ref: '#/components/schemas/UUID' nullable: true current_config_hash: type: string description: Content hash of the agent's current config. target_config_hash: type: string description: Content hash of the version being restored. candidate_config_hash: type: string nullable: true description: Content hash of the config that would be applied. acceptance_hash: type: string nullable: true description: >- Opaque hash binding this preview; pass it unchanged to the accept endpoint. Present when `state` is `ready`. changed_fields: type: array items: type: string description: Top-level config fields that would change. issues: type: array items: $ref: '#/components/schemas/DependencyIssue' preparation: $ref: '#/components/schemas/AgentConfigPreparationStatus' nullable: true description: >- Source of `candidate_hash`, `resource_hash`, and `dependency_hash` for the accept request. candidate: $ref: '#/components/schemas/AgentConfigDocument' nullable: true description: The config document that would be applied. ErrorResponse: type: object additionalProperties: true description: > Error payloads can vary depending on where the error is raised (edge gateway vs backend). Common shapes include: - `{ "error": "message" }` - `{ "detail": "message" }` - `{ "detail": [ { "loc": [...], "msg": "...", "type": "..." } ] }` (validation) properties: error: type: string detail: oneOf: - type: string - type: array items: type: object UUID: type: string format: uuid example: 550e8400-e29b-41d4-a716-446655440000 DependencyIssue: type: object additionalProperties: false required: - path - code - resource_type - message properties: path: type: string description: Path of the config field the issue relates to. code: type: string resource_type: type: string resource_id: type: string nullable: true message: type: string remediation: type: string nullable: true description: >- A dependency issue detected while validating an agent config document against the organisation's current resources. AgentConfigPreparationStatus: type: object required: - state - candidate_hash - resource_hash - config properties: state: type: string enum: - ready - preparing - failed candidate_hash: type: string pattern: ^[0-9a-f]{64}$ description: Content hash of the prepared config document. resource_hash: type: string pattern: ^[0-9a-f]{64}$ description: Hash of the organisation resources the config depends on. dependency_hash: type: string pattern: ^[0-9a-f]{64}$ nullable: true preparation_operation_id: type: string nullable: true retry_after_seconds: type: integer minimum: 1 maximum: 60 nullable: true description: >- Suggested delay in seconds before retrying (also sent as the `Retry-After` header). config: $ref: '#/components/schemas/AgentConfigDocument' description: > Status returned while a config document references organisation resources that require resolution before it can be activated. AgentConfigDocument: type: object additionalProperties: true description: > Canonical agent configuration document, exactly as produced by the agent config download endpoints. The document is a portable, secret-free representation of the agent's configuration; webhook auth is carried as organisation Vault secret references. Treat it as an opaque file: download, store, and re-import it without modification. responses: UnauthorizedError: description: Unauthorized. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: unauthorized: summary: Authentication failed value: detail: Authentication is required for this endpoint. ForbiddenError: description: Forbidden. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: forbidden: summary: Access denied value: detail: You do not have access to this resource. NotFoundError: description: Not found. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: not-found: summary: Resource not found value: detail: The requested resource was not found. ValidationError: description: Validation error. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: validation-error: summary: Request validation failed value: detail: - loc: - body - language msg: Input should be a valid string type: string_type InternalServerError: description: Internal server error. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: internal-server-error: summary: Unexpected application error value: detail: An unexpected internal error occurred. securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: API key ````