> ## 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.

# Save an experiment's setup

> Replace the experiment's setup. Send `expectedVersion` with the version you read and the save is refused with a 409 when someone else wrote first, instead of overwriting their work.



## OpenAPI

````yaml PUT /api/v1/experiments/{slug}/workbench-state
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}/workbench-state:
    put:
      tags:
        - Experiments
      summary: Save an experiment's setup
      description: >-
        Replace the experiment's setup. Send `expectedVersion` with the version
        you read and the save is refused with a 409 when someone else wrote
        first, instead of overwriting their work.
      operationId: putApiExperimentsBySlugWorkbenchState
      parameters:
        - in: path
          name: slug
          schema:
            type: string
            minLength: 1
          required: true
          description: The experiment's slug, or its id
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                state:
                  type: object
                  propertyNames:
                    type: string
                  additionalProperties: {}
                  description: The full setup to save
                expectedVersion:
                  description: >-
                    The version you read. Sending it refuses the save when
                    someone else already wrote on top of it.
                  type: integer
                  minimum: -9007199254740991
                  maximum: 9007199254740991
                commitMessage:
                  description: Names this version in the history list
                  type: string
              required:
                - state
      responses:
        '200':
          description: Success
          content:
            application/json:
              schema:
                type: object
                properties:
                  version:
                    type: integer
                    minimum: -9007199254740991
                    maximum: 9007199254740991
                    description: The version the save produced
                required:
                  - version
                additionalProperties: false
        '400':
          description: >-
            The setup did not match the schema
            (experiment_invalid_workbench_state), points at something that no
            longer exists (experiment_workbench_missing_reference), or the
            experiment is not an evaluations workbench
            (experiment_type_mismatch)
          content: {}
        '401':
          description: Missing or invalid API key, or the key lacks the permission
          content: {}
        '404':
          description: No such experiment in this project
          content: {}
        '409':
          description: >-
            Someone else saved since you read this state
            (experiment_stale_workbench_state). `currentVersion` carries the
            version to read again.
          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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