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

# Upload an attachment

> Streams one raw request body directly to Relay storage, up to 100 MB. `Content-Length` is required and Relay verifies it against the stored object size. `Content-Type` sets the stored MIME type; `X-Relay-Filename` names downloads. Agent tokens and user sessions both work; the attachment is private to its uploader.



## OpenAPI

````yaml /api-reference/openapi.yaml post /v1/attachments
openapi: 3.1.0
info:
  title: Relay developer API
  version: '0.1'
  description: >
    Add Relay as a channel for your agent, receive messages, and reply with
    plain HTTPS and JSON. Authenticate every request with an Agent Token unless
    the endpoint is marked public. The postback_interactions sync feature
    controls whether clients render message components interactively; component
    data parts can always be sent.
  x-relay-feature-availability:
    postback_interactions: off-by-default-preview
  license:
    name: Proprietary
    identifier: LicenseRef-Proprietary
servers:
  - url: https://api.relayapp.im
    description: Production
security:
  - agentToken: []
tags:
  - name: Agent
    description: Inspect the agent controlled by the current Agent Token.
  - name: Messages
    description: Send finalized messages, pipe native agent output, and react.
  - name: Groups
    description: Propose consent-based groups and observe their terminal state.
  - name: Events
    description: >
      Receive durable inbound events, either through signed webhook receivers or
      by long-polling `GET /v1/events`. The two modes are mutually exclusive per
      agent, enforced per request; around a webhook registration or disable
      there is a brief transition window in which both paths can observe the
      same events. Delivery is at least once everywhere — always deduplicate by
      `event_id`.
  - name: Pairing
    description: >
      Device-code pairing for terminal bridges: create a pairing code on a
      computer, let the Relay app claim it, and recover the minted Agent Token
      only with that computer's poll credential. The token never travels to the
      phone.
  - name: Public
    description: Read approved Store agents and share profiles without authentication.
paths:
  /v1/attachments:
    post:
      tags:
        - Attachments
      summary: Upload an attachment
      description: >-
        Streams one raw request body directly to Relay storage, up to 100 MB.
        `Content-Length` is required and Relay verifies it against the stored
        object size. `Content-Type` sets the stored MIME type;
        `X-Relay-Filename` names downloads. Agent tokens and user sessions both
        work; the attachment is private to its uploader.
      operationId: uploadAttachment
      parameters:
        - in: header
          name: Content-Length
          required: true
          schema:
            type: integer
            minimum: 1
            maximum: 104857600
          description: Exact raw request-body size in bytes.
        - in: header
          name: Content-Type
          schema:
            type: string
          example: image/png
        - in: header
          name: X-Relay-Filename
          schema:
            type: string
          example: chart.png
      requestBody:
        required: true
        content:
          application/octet-stream:
            schema:
              type: string
              format: binary
      responses:
        '201':
          description: Stored and available.
          content:
            application/json:
              schema:
                type: object
                properties:
                  attachment:
                    type: object
                    required:
                      - id
                      - url
                      - content_type
                      - size_bytes
                    properties:
                      id:
                        type: string
                        example: att_01KXGWNZFR
                      url:
                        type: string
                        description: Capability download URL.
                      content_type:
                        type: string
                        example: image/png
                      size_bytes:
                        type: integer
        '401':
          $ref: '#/components/responses/Unauthorized'
        '413':
          description: The declared attachment size exceeds 100 MB.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
        '422':
          description: >-
            Content-Length is missing or invalid, the body is empty, or the
            stored size does not match the declaration.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
components:
  responses:
    Unauthorized:
      description: Token is absent or invalid.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
  schemas:
    Error:
      type: object
      required:
        - error
      properties:
        error:
          type: object
          required:
            - code
            - message
          properties:
            code:
              type: string
              example: invalid_request
            message:
              type: string
              example: conversation_id is required
  securitySchemes:
    agentToken:
      type: http
      scheme: bearer
      description: Agent Token (`rly_live_…`), shown once at agent creation.

````