> ## 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. # Adjust inventory -- single or multi-item atomic (cycle count, shrinkage, revaluation) > ATOMIC-CREATE (2026-05-12): accepts items[] for multi-line atomic adjustments OR top-level product_id/quantity for single-item compat mode. All items adjust in one DB transaction; any failure rolls back all items (no partial writes). Positive or negative delta per item. Hard-blocks negative balance and zero-cost positives. GL: DR/CR Inventory + DR/CR Suspense or Shrinkage via glPostInventoryAdjustment, fires per item in same transaction (Rule 21). Connector: triggers async pushInventoryToMarketplaces. Response: {object:inventory_adjustment_result, items:[{index,product_id,balance,transaction,gl_amount,journal_entry_id,consumed_layers}], summary} for items[]; single object for compat mode. On failure: {error, code, hint, items_completed_before_failure} -- all items rolled back regardless of items_completed_before_failure. migration:write scope: documents authorization for opening-balance loads. Hard-blocks still apply. ## OpenAPI ````yaml /openapi.yaml post /inventory/adjustments 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: /inventory/adjustments: post: tags: - Inventory summary: >- Adjust inventory -- single or multi-item atomic (cycle count, shrinkage, revaluation) description: > ATOMIC-CREATE (2026-05-12): accepts items[] for multi-line atomic adjustments OR top-level product_id/quantity for single-item compat mode. All items adjust in one DB transaction; any failure rolls back all items (no partial writes). Positive or negative delta per item. Hard-blocks negative balance and zero-cost positives. GL: DR/CR Inventory + DR/CR Suspense or Shrinkage via glPostInventoryAdjustment, fires per item in same transaction (Rule 21). Connector: triggers async pushInventoryToMarketplaces. Response: {object:inventory_adjustment_result, items:[{index,product_id,balance,transaction,gl_amount,journal_entry_id,consumed_layers}], summary} for items[]; single object for compat mode. On failure: {error, code, hint, items_completed_before_failure} -- all items rolled back regardless of items_completed_before_failure. migration:write scope: documents authorization for opening-balance loads. Hard-blocks still apply. operationId: postInventoryAdjustment parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: oneOf: - type: object description: Multi-item atomic mode required: - location_id - items properties: location_id: type: string format: uuid description: Layer 4 -- required reason: type: string items: type: array minItems: 1 items: type: object required: - product_id - quantity_delta properties: product_id: type: string format: uuid quantity_delta: type: integer description: Signed delta (positive=add, negative=remove) unit_cost: type: number description: Required for positive adjustments notes: type: string allow_negative: type: boolean description: Requires inventory.allow_negative permission - type: object description: Single-item compat mode required: - product_id - location_id - quantity properties: product_id: type: string format: uuid location_id: type: string format: uuid description: Layer 4 -- required quantity: type: integer description: Signed delta (positive=add, negative=remove) unit_cost: type: number description: Required for positive adjustments reason: type: string notes: type: string allow_negative: type: boolean description: Requires inventory.allow_negative permission examples: cycle_count_multi: summary: Cycle count -- mixed positive and negative deltas (atomic) description: > Adjust two SKUs in a single atomic transaction. Item 0 adds 3 units (positive delta, unit_cost required to establish new FIFO layer). Item 1 removes 2 units (negative delta, FIFO layers consumed automatically, unit_cost not required). On any failure both items roll back -- no partial writes. value: location_id: 91aa7588-4dc7-4edd-b172-7de91f5e1f78 reason: cycle_count memo: Monthly cycle count Q2 2026 items: - product_id: 7f6f3e14-eaad-4c45-b922-209f6dc6d140 quantity_delta: 3 unit_cost: 12.5 notes: Count correction -- physical count higher than system - product_id: ec9288c3-12b1-474f-bb09-b0b15bb7a8ff quantity_delta: -2 notes: Shrinkage discovered during count shrinkage_single: summary: Single-item shrinkage write-down value: product_id: 7f6f3e14-eaad-4c45-b922-209f6dc6d140 location_id: 91aa7588-4dc7-4edd-b172-7de91f5e1f78 quantity: -5 reason: shrinkage notes: Damaged goods -- water exposure responses: '201': description: Adjustment applied content: application/json: schema: type: object properties: object: type: string enum: - inventory_adjustment_result examples: cycle_count_result: summary: Cycle count adjustment result value: object: inventory_adjustment_result items: - index: 0 product_id: 7f6f3e14-eaad-4c45-b922-209f6dc6d140 location_id: 91aa7588-4dc7-4edd-b172-7de91f5e1f78 quantity_delta: 3 gl_amount: 37.5 journal_entry_id: c79ab8cf-b840-471f-bea9-6a24df80f550 balance: on_hand: 13 allocated: 0 available: 13 total_value: '162.50' transaction: id: 10e06976-8096-48bc-bbbd-5fe71626f544 type: adjustment quantity: 3 unit_price: '12.5000' total_price: '37.50' transaction_id: IVT-0000155 consumed_layers: [] - index: 1 product_id: ec9288c3-12b1-474f-bb09-b0b15bb7a8ff location_id: 91aa7588-4dc7-4edd-b172-7de91f5e1f78 quantity_delta: -2 gl_amount: -17.5 journal_entry_id: a8c5c8c6-b0b0-4e63-918d-a247189735f3 balance: on_hand: 3 allocated: 0 available: 3 total_value: '26.25' transaction: id: 93659e88-f3ba-4709-9798-388886820ea0 type: adjustment quantity: -2 unit_price: '8.7500' total_price: '17.50' transaction_id: IVT-0000156 consumed_layers: - layer_id: 3de7680e-fba2-444a-a204-7290cc6f08e1 qty_used: 2 qty_after: 3 unit_cost: 8.75 layer_cogs: 17.5 summary: total_items: 2 total_gl_impact: 20 '400': $ref: '#/components/responses/Error' '401': $ref: '#/components/responses/Error' '403': $ref: '#/components/responses/Error' security: - ApiKeyAuth: [] 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 responses: Error: description: Error response (400/401/403/404/409/422/429/500) content: application/json: schema: $ref: '#/components/schemas/ErrorEnvelope' schemas: 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 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. ````