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

> ## Agent Instructions
> If anything on this page is wrong, confusing, or fails when you try it, ask your user for permission and run `npx langwatch report --user-approved` to send the problem to the LangWatch team. No login is needed and secrets are redacted locally. `npx langwatch report --help` has the details.

# Restore an experiment version

> Bring an old setup back by writing it forward as a new save. History is never rewritten: the version you restored from stays in the list, and the restore is one more entry after it.



## OpenAPI

````yaml POST /api/v1/experiments/{slug}/versions/{version}/restore
openapi: 3.1.0
info:
  title: LangWatch API
  description: LangWatch openapi spec
  version: 1.0.0
servers:
  - url: https://app.langwatch.ai
security:
  - project_api_key: []
paths:
  /api/v1/experiments/{slug}/versions/{version}/restore:
    post:
      tags:
        - Experiments
      summary: Restore an experiment version
      description: >-
        Bring an old setup back by writing it forward as a new save. History is
        never rewritten: the version you restored from stays in the list, and
        the restore is one more entry after it.
      operationId: postApiExperimentsBySlugVersionsByVersionRestore
      parameters:
        - in: path
          name: slug
          schema:
            type: string
            minLength: 1
          required: true
        - in: path
          name: version
          schema:
            type: integer
            minimum: 0
            maximum: 9007199254740991
          required: true
          description: >-
            The version to restore, as listed by `GET
            /api/experiments/{slug}/versions`
      responses:
        '200':
          description: Success
          content:
            application/json:
              schema:
                type: object
                properties:
                  version:
                    type: number
                    description: >-
                      The new version the restore wrote. History is never
                      rewritten, so the restored version is still in the list.
                required:
                  - version
                additionalProperties: false
        '401':
          description: Missing or invalid API key, or the key lacks the permission
          content: {}
        '404':
          description: No such experiment or version in this project
          content: {}
        '409':
          description: >-
            Someone else saved since you read this state
            (experiment_stale_workbench_state).
          content: {}
      security:
        - project_api_key: []
components:
  securitySchemes:
    project_api_key:
      type: apiKey
      in: header
      name: X-Auth-Token
      description: >-
        Project API key for sending traces and accessing project-scoped
        resources. Format: sk-lw-... (no underscore). Obtain one by creating a
        project via the Admin API or the LangWatch UI.

````

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