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

# Initiate signed URL upload to extend a measurement

> Mint a signed URL for uploading a delta time series extend file.



## OpenAPI

````yaml https://api.ionworks.com/openapi.json post /cell_measurements/{measurement_id}/initiate-extend
openapi: 3.1.0
info:
  title: FastAPI
  version: 0.1.0
servers:
  - url: https://api.ionworks.com
    description: Production
security: []
paths:
  /cell_measurements/{measurement_id}/initiate-extend:
    post:
      tags:
        - Cell Measurements
      summary: Initiate signed URL upload to extend a measurement
      description: Mint a signed URL for uploading a delta time series extend file.
      operationId: >-
        initiate_measurement_extend_cell_measurements__measurement_id__initiate_extend_post
      parameters:
        - name: measurement_id
          in: path
          required: true
          schema:
            type: string
            title: Measurement Id
      responses:
        '201':
          description: Successful Response
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/InitiateUploadResponse'
        '422':
          description: Validation Error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HTTPValidationError'
components:
  schemas:
    InitiateUploadResponse:
      properties:
        measurement_id:
          type: string
          title: Measurement Id
          description: Pre-generated measurement UUID
        uploads:
          items:
            $ref: '#/components/schemas/UploadInfo'
          type: array
          title: Uploads
          description: Signed URL info for each upload target
      type: object
      required:
        - measurement_id
        - uploads
      title: InitiateUploadResponse
      description: Response model after initiating a signed URL upload.
    HTTPValidationError:
      properties:
        detail:
          items:
            $ref: '#/components/schemas/ValidationError'
          type: array
          title: Detail
      type: object
      title: HTTPValidationError
    UploadInfo:
      properties:
        filename:
          anyOf:
            - type: string
            - type: 'null'
          title: Filename
          description: Original filename
        signed_url:
          type: string
          title: Signed Url
          description: Pre-signed URL for uploading
        token:
          type: string
          title: Token
          description: Upload token
        path:
          type: string
          title: Path
          description: Storage path for the file
        multipart:
          anyOf:
            - $ref: '#/components/schemas/MultipartUploadInfo'
            - type: 'null'
          description: >-
            Optional S3-multipart target for large files. Clients that do not
            understand this field fall back to PUTting the signed URL.
      type: object
      required:
        - signed_url
        - token
        - path
      title: UploadInfo
      description: Signed URL info for a single file upload.
    ValidationError:
      properties:
        loc:
          items:
            anyOf:
              - type: string
              - type: integer
          type: array
          title: Location
        msg:
          type: string
          title: Message
        type:
          type: string
          title: Error Type
        input:
          title: Input
        ctx:
          type: object
          title: Context
      type: object
      required:
        - loc
        - msg
        - type
      title: ValidationError
    MultipartUploadInfo:
      properties:
        endpoint:
          type: string
          title: Endpoint
          description: S3-compatible endpoint URL.
        region:
          type: string
          title: Region
          description: S3 region name.
        bucket:
          type: string
          title: Bucket
          description: Target storage bucket.
        object_path:
          type: string
          title: Object Path
          description: Object key within the bucket.
        access_key_id:
          type: string
          title: Access Key Id
          description: S3 access key id.
        secret_access_key:
          type: string
          title: Secret Access Key
          description: S3 secret access key.
        session_token:
          type: string
          title: Session Token
          description: S3 session token (caller's JWT).
        expires_at:
          anyOf:
            - type: string
            - type: 'null'
          title: Expires At
          description: ISO timestamp after which the credentials stop working.
      type: object
      required:
        - endpoint
        - region
        - bucket
        - object_path
        - access_key_id
        - secret_access_key
        - session_token
      title: MultipartUploadInfo
      description: >-
        S3-multipart credentials and target for a large direct-to-storage
        upload.


        Mirrors the SDK-side model. The session token is the caller's own JWT,
        so

        Supabase Storage RLS applies to the S3 operations -- the service key
        must

        never appear in this block.

````