> ## 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. # Update an attachment > Updates an attachment's filename, visibility, expiration, or metadata; fields tied to the underlying stored file, such as its bucket, key, and checksum, cannot be changed. Requires `attachments:write` scope. ## OpenAPI ````yaml /openapi.yaml patch /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. **Changelog.** Entries are dated and name every published contract whose MEANING moved, not only the ones whose field names changed. The narrative version of the same entries, written for integrators, is published at https://arcuserp.mintlify.app/changelog. **2026-09-22 (planned 2026-09-21), REORDER-BUYER-TRUTH: demand changed what it MEANS on three published contracts, with no field renamed.** An integrator that pins field names sees no breakage and different numbers, which is why this entry exists. - **Demand now counts build consumption.** `demand_avg_per_day` on the public product, kit and inventory-balance objects, and `daily_demand` / `demand_basis` / `net_suggested_qty` on `GET /v1/purchasing/reorder-report`, are composed from fulfilled sales lines PLUS posted `build_consume` inventory draws: each physical decrement of a product counts exactly once. The previous rule adopted an internal-consumption basis only when the sales blend was exactly zero, so a product both sold AND consumed into work orders planned as if the build draws did not exist. Products drawn into work orders move; on one production-shaped dataset five did, the largest from 0.05/day to 14.95/day. - **`demand_basis` now carries four values, not two:** `sales`, `sales_and_builds`, `builds` and `consumption`. A consumer with a two-branch reader (anything that is not `consumption` is `sales`) silently hides the two new ones. - **`current_demand_units` on `GET /v1/inventory/balances/:id` moved, by a second rule.** It counts committed-but-unshipped CUSTOMER demand, and it now counts a kit component's own line rather than its parent kit line, and excludes non-sales documents. On one production dataset 269 of 1,043 balance rows changed, 227 of them downward; the largest single move was 1,941 to 25, on a product whose open PURCHASE order line had been reported as customer demand. Re-baseline anything that alerts or reorders off this field. - `run_rate_30/90/180/365` and `blended_daily` on the same balance object move for the first reason above. - **Added, not changed:** `GET /v1/purchasing/reorder-report` accepts `demand_window` and returns the unit, cover-through and reorder-point-provenance fields documented on that operation; `order_multiple` is accepted and returned on the product-vendor doors. - **Volume note.** The `inventory.low_stock`, `inventory.out_of_stock` and `inventory.back_in_stock` webhook events are population-gated on `on_hand <= reorder_point`, and reorder points move with the demand above, so subscribers should expect a one-time step change in event volume around the release. 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 patch: tags: - Attachments summary: Update an attachment description: >- Updates an attachment's filename, visibility, expiration, or metadata; fields tied to the underlying stored file, such as its bucket, key, and checksum, cannot be changed. Requires `attachments:write` scope. operationId: updateAttachmentV1 parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: type: object properties: filename: type: string is_public: type: boolean expires_at: type: string format: date-time nullable: true metadata: type: object responses: '200': description: Updated attachment content: application/json: schema: $ref: '#/components/schemas/Attachment' '404': $ref: '#/components/responses/Error' security: - ApiKeyAuth: - attachments:write components: parameters: IdempotencyKey: name: Idempotency-Key in: header required: false description: | Client-generated unique key for idempotent POST/PATCH/DELETE operations. Alias for the Idempotency parameter. Max 255 chars. On retry with the same key, the original response is returned without re-executing the operation. Keys expire after 24 hours. schema: type: string maxLength: 255 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. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.