> ## Documentation Index > Fetch the complete documentation index at: https://docs-pos.solya.app/llms.txt > Use this file to discover all available pages before exploring further. # Open a register session > Opens a register session with its opening cash float and the salesperson taking the shift. The session is always created `open` with no movements; the actor and the opened-at instant are stamped server-side from the context. Amounts are integer cents. 409s when a session with the same id already exists (a double-open). ## OpenAPI ````yaml /openapi.json post /v1/sessions openapi: 3.0.3 info: title: Solya POS API version: 1.0.0 description: >- The Solya POS backend HTTP surface. Every documented operation is agent-ready: it carries an `operationId`, an agent-facing `description`, the `pos.*` scopes it enforces (`x-required-permissions`) and an `x-agent-tier`. Success responses return the payload as raw JSON; failures return the `ErrorResponse` envelope (`{ error: { code, message, statusCode } }`). servers: - url: / description: The backend, relative to its deployed origin. security: [] paths: /v1/sessions: post: tags: - Checkout summary: Open a register session description: >- Opens a register session with its opening cash float and the salesperson taking the shift. The session is always created `open` with no movements; the actor and the opened-at instant are stamped server-side from the context. Amounts are integer cents. 409s when a session with the same id already exists (a double-open). operationId: openSession requestBody: required: true content: application/json: schema: type: object properties: id: type: string minLength: 1 storeId: type: string minLength: 1 registerId: type: string minLength: 1 currency: type: string minLength: 3 maxLength: 3 salespersonId: type: string minLength: 1 openingFloatCents: type: integer minimum: 0 maximum: 9007199254740991 required: - id - storeId - registerId - currency - salespersonId - openingFloatCents example: id: sess-ok storeId: store-1 registerId: reg-1 currency: EUR salespersonId: cashier-1 openingFloatCents: 10000 responses: '201': description: The opened session at status `open`. content: application/json: schema: type: object properties: id: type: string storeId: type: string registerId: type: string currency: type: string salespersonId: type: string openingFloatCents: type: integer minimum: -9007199254740991 maximum: 9007199254740991 movements: type: array items: type: object properties: amountCents: type: integer minimum: -9007199254740991 maximum: 9007199254740991 reason: type: string at: type: string format: date-time pattern: >- ^(?:(?:\d\d[2468][048]|\d\d[13579][26]|\d\d0[48]|[02468][048]00|[13579][26]00)-02-29|\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\d|30)|(?:02)-(?:0[1-9]|1\d|2[0-8])))T(?:(?:[01]\d|2[0-3]):[0-5]\d(?::[0-5]\d(?:\.\d+)?)?(?:Z))$ required: - amountCents - reason - at additionalProperties: false status: type: string enum: - open - closed closing: nullable: true type: object properties: countedCents: type: integer minimum: -9007199254740991 maximum: 9007199254740991 expectedCents: type: integer minimum: -9007199254740991 maximum: 9007199254740991 varianceCents: type: integer minimum: -9007199254740991 maximum: 9007199254740991 closedAt: type: string format: date-time pattern: >- ^(?:(?:\d\d[2468][048]|\d\d[13579][26]|\d\d0[48]|[02468][048]00|[13579][26]00)-02-29|\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\d|30)|(?:02)-(?:0[1-9]|1\d|2[0-8])))T(?:(?:[01]\d|2[0-3]):[0-5]\d(?::[0-5]\d(?:\.\d+)?)?(?:Z))$ required: - countedCents - expectedCents - varianceCents - closedAt additionalProperties: false actorId: type: string openedAt: type: string format: date-time pattern: >- ^(?:(?:\d\d[2468][048]|\d\d[13579][26]|\d\d0[48]|[02468][048]00|[13579][26]00)-02-29|\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\d|30)|(?:02)-(?:0[1-9]|1\d|2[0-8])))T(?:(?:[01]\d|2[0-3]):[0-5]\d(?::[0-5]\d(?:\.\d+)?)?(?:Z))$ required: - id - storeId - registerId - currency - salespersonId - openingFloatCents - movements - status - closing - actorId - openedAt additionalProperties: false description: The opened session at status `open`. example: id: sess-ok storeId: store-1 registerId: reg-1 currency: EUR salespersonId: cashier-1 openingFloatCents: 10000 movements: [] status: open closing: null actorId: cashier-1 openedAt: '2026-01-02T09:00:00.000Z' '400': description: >- The request failed schema validation; `error.fieldErrors` lists the fields. content: application/json: schema: $ref: '#/components/schemas/ValidationErrorResponse' '401': description: No valid credential was presented — send a bearer token. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '403': description: The actor is authenticated but lacks the required `pos.*` scope. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '409': description: >- The request conflicts with current state (duplicate id or stale version). content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' '500': description: An unexpected server error — safe to retry idempotent requests. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' security: - bearerAuth: [] components: schemas: ValidationErrorResponse: type: object required: - error additionalProperties: false description: >- A `VALIDATION_FAILED` envelope carrying the offending fields in `fieldErrors`. properties: error: type: object required: - code - message - statusCode additionalProperties: false properties: code: type: string enum: - VALIDATION_FAILED message: type: string statusCode: type: integer fieldErrors: type: array description: >- One entry per rejected field: the field path and why it was rejected. items: type: object required: - field - message additionalProperties: false properties: field: type: string description: Dot-path of the offending field. message: type: string description: Why the field was rejected. ErrorResponse: type: object required: - error additionalProperties: false description: The uniform failure envelope every non-2xx response returns. properties: error: type: object required: - code - message - statusCode additionalProperties: false properties: code: type: string enum: - VALIDATION_FAILED - UNAUTHORIZED - FORBIDDEN - NOT_FOUND - CONFLICT - BUSINESS_RULE_VIOLATION - INTERNAL_ERROR description: >- Machine-readable kernel `ResultCode` — branch on this, not on `message`. message: type: string description: >- Human-readable explanation. Safe to surface; never leaks server internals. statusCode: type: integer description: >- The HTTP status, mirrored into the body so a client need not read headers. securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: JWT description: >- `Authorization: Bearer `. Accepts EITHER a Keycloak access token (scopes-in-token) OR an opaque POS session token; both resolve to the same `pos.*` scope vocabulary the route guards enforce. ````