> ## Documentation Index > Fetch the complete documentation index at: https://docs.arcuserp.com/llms.txt > Use this file to discover all available pages before exploring further. # Retrieve an attachment ## OpenAPI ````yaml /openapi.yaml get /attachments/{id} openapi: 3.1.0 info: title: Arcus ERP Public API version: 1.0.0 description: > Arcus ERP public REST API. Designed for external integrations and data migration. **Authentication.** Bearer token (API key) via the `Authorization` header. Format: `Authorization: Bearer ark_live_ent__` (or `ark_test_*` for sandbox). API keys are issued per-entity in **Settings > Developers > API Keys**. **Entity scoping.** The entity is encoded in the API key prefix; routes are flat (e.g. `/v1/accounts`, `/v1/orders`, `/v1/products`). A small set of platform endpoints (migration, reconciliation, events, webhook endpoints, API keys) use the `/v1/entities/{entity_id}/...` form -- those are noted in their tags. **Key capabilities.** - Related-resource hydration via `?expand[]=` (see `x-arcus-expand` on each resource). - Cursor-based pagination (`starting_after` / `ending_before` / `limit`). - Idempotency via the `Idempotency-Key` header. - Webhook events for asynchronous notification. - Conditional requests / ETag for cache validation. servers: - url: https://api.arcuserp.com/v1 description: Arcus ERP API (accepts both live `ark_live_*` and test `ark_test_*` keys) - url: https://dev-api.arcuserp.com/v1 description: >- Dev sandbox API (test-only data, accepts `ark_test_*` keys against dev RDS) security: [] paths: /attachments/{id}: parameters: - name: id in: path required: true schema: type: string format: uuid get: tags: - Attachments summary: Retrieve an attachment operationId: getAttachmentV1 responses: '200': description: Attachment content: application/json: schema: $ref: '#/components/schemas/Attachment' '404': $ref: '#/components/responses/Error' security: - ApiKeyAuth: - attachments:read components: schemas: Attachment: type: object description: > A file attached to a parent resource via `parent_type` + `parent_id`. The two-step upload flow (`POST /attachments/upload-url` then `POST /attachments`) persists bytes in S3 and the row in `public.attachments`. `s3_bucket` and `s3_key` are operator-internal; clients fetch the file by minting a fresh presigned URL via `POST /attachments/{id}/download-url`. Soft-delete clears `deleted_at` but does NOT delete the S3 object; an out-of-band sweeper sets `s3_deleted_at` once bytes are purged. Scope: attachments:read / attachments:write / attachments:delete. properties: id: type: string format: uuid readOnly: true object: type: string example: attachment entity_id: type: string format: uuid readOnly: true parent_type: type: string description: Parent resource family (order, account, ap_bill, etc.). 1..30 chars. parent_id: type: string format: uuid filename: type: string description: Operator-supplied file name. 1..255 chars. mime_type: type: string description: Content type at upload time. 1..100 chars. size_bytes: type: integer format: int64 description: File size at upload time in bytes. s3_bucket: type: string readOnly: true description: Operator-internal; clients should never need this. s3_key: type: string readOnly: true description: Operator-internal; clients should never need this. s3_etag: type: string nullable: true readOnly: true checksum_sha256: type: string nullable: true readOnly: true description: SHA-256 of the bytes if supplied at upload time. uploaded_by_user_id: type: string format: uuid nullable: true readOnly: true uploaded_via: type: string enum: - web - api - portal - migration default: web description: Origin of the upload. Set automatically; not caller-writable. is_public: type: boolean default: false description: If true, exposes via tokenized portal URL. expires_at: type: string format: date-time nullable: true description: Optional auto-expiry; the sweeper soft-deletes past this date. external_source: type: string nullable: true description: Migration provenance (versa, bubble). external_id: type: string nullable: true metadata: type: object description: Free-form caller metadata. Default {}. deleted_at: type: string format: date-time nullable: true readOnly: true s3_deleted_at: type: string format: date-time nullable: true readOnly: true description: Set once the sweeper purges S3 bytes. created_at: type: string format: date-time readOnly: true ErrorEnvelope: type: object description: | Canonical error response envelope. All API errors use this shape. required: - error - code properties: error: type: string description: Machine-readable error key example: not_found code: type: string description: Machine-readable error code (often same as error) example: not_found type: type: string enum: - validation_error - permission_error - not_found - conflict - rate_limit - internal - expand_error - not_implemented example: not_found hint: type: string description: Human-readable one-sentence explanation (English) example: >- The requested order does not exist or does not belong to this entity. param: type: string description: The parameter that caused the error, if applicable example: expand[0] required: type: string description: The scope required (only on insufficient_scope errors) example: accounts:read request_id: type: string description: >- Unique request ID for support tracing (maps to CloudWatch log stream) example: req_abc123 responses: Error: description: Error response (400/401/403/404/409/422/429/500) content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' securitySchemes: ApiKeyAuth: type: http scheme: bearer description: | API key issued per entity via Settings > Developers > API Keys. Each key carries scopes (e.g. orders:read, products:write). Bearer token format: Authorization: Bearer ark_live_ent__ Test keys use ark_test_ent__. Both are issued per entity via Settings > Developers > API Keys. ````