> ## Documentation Index > Fetch the complete documentation index at: https://docs.lastaccountingcompany.com/llms.txt > Use this file to discover all available pages before exploring further. # Download one retained file referenced by chat > Returns retained bytes only when the exact document and SHA-256 are referenced by a visible human chat message or committed on a terminal Björn receipt. A document row, hidden transport, unauthorized internal message, or another tenant's reference is never sufficient authority. ## OpenAPI ````yaml /openapi.yaml get /chat-artifacts/{document_id} openapi: 3.1.0 info: title: LAC Customer API version: 2026-10-06.2 description: > Last Accounting Company (LAC) is an AI-native accounting firm for Finnish SMBs: continuous reconciliation, daily close, real-time dashboards, and full Vero reporting. This API is the same surface the LAC customer portal UI uses. It gives you programmatic access to your books (read-only general-ledger views), financial statements, documents, invoicing, payroll, source-system connections, and the message channel to Björn, the accounting agent. ## Authentication Customer API requests carry `Authorization: Bearer `. Two token kinds are accepted: - **Portal API key** (`lac_sk_...`) — minted in portal Settings → API access. Keys have a scope of `read` or `write`. Read-scoped keys are refused on all mutating methods (POST/PATCH/DELETE). Write-scoped keys act as the `operator` role: they can never use payroll endpoints (reads included), change company settings, grant access, approve or return an invoice, or manage API keys. Payroll and company settings require an interactive admin or existing broad approver. Invoice decisions require the matching invoice review permission. Write-scoped keys can prepare draft partner seller profiles. An interactive company admin must review the evidence and activate a profile or change an active profile. - **Firebase ID token** — the interactive session token used by the portal UI itself. The Shopify App endpoints are provider-facing exceptions with explicit per-operation security: App Home assets are public, App Bridge actions use a Shopify session JWT, and privacy webhooks use Shopify's raw-body HMAC. API keys are pinned to a single company, so the `customer_id` parameter (query string on GETs, body field on writes) can always be omitted when authenticating with an API key. Interactive tokens with access to multiple companies use `customer_id` to select one. ## Conventions - All field names are `snake_case` on the wire. - Monetary amounts are **integer cents** (fields suffixed `_cents`). - Rates and percentages are **basis points** (fields suffixed `_basis_points`; 10000 = 100%, e.g. Finnish standard VAT 25.5% = 2550). - Quantities on invoice lines are decimal strings (e.g. `"1"`, `"2.5"`). - Dates are `YYYY-MM-DD`; periods are `YYYY-MM`; ranges accept `YYYY-MM`, `YYYY-Qn`, `YYYY`, `all`, `this_month`, or `last_6_months`. ## Limits - Document uploads: at most 20 files and 25 MB per request. - Sheet pagination: `limit` is capped at 200 rows per page (0 = unpaginated). ## Errors Errors return a JSON envelope `{"error": "...", "detail": "..."}` with a conventional HTTP status code (401 missing/invalid token, 403 insufficient scope or role, 404 not found, 422 validation failure). More at [docs.lastaccountingcompany.com](https://docs.lastaccountingcompany.com). contact: name: Last Accounting Company url: https://docs.lastaccountingcompany.com servers: - url: https://api.app.lastaccountingcompany.com/portal description: Production (note the /portal base path). security: - apiKey: [] tags: - name: Company description: Company profile, identity, overview, and agent status. - name: Onboarding description: Saved customer onboarding facts, source inventory, and opening statements. - name: Books description: >- Read-only windows into the canonical general ledger: the spreadsheet-style Books/VAT sheet, financial statements, and analytics. There is no cell-edit or batch-edit API — the books are maintained by LAC. The one write here is a row declaration: your answer about a row (no receipt exists, private, a split, or a different booking), recorded as evidence for Björn. - name: Dimensions description: >- Project, cost-centre, department, and customer-defined reporting lenses over posted general-ledger lines. Provider catalogs are read-only; local axes and values are available for bank/file-only books. - name: Documents description: Receipt/invoice/contract uploads and per-file ingest metadata. - name: Messages description: The chat channel to Björn, the accounting agent. - name: Work log description: >- Append-only work-hours log (date, minutes, note). Hours are records for invoicing and payroll evidence; they do not post to the books. Kilometres are not logged here — vehicle travel is submitted as an expense claim in the portal, where statutory reimbursement rates apply. - name: Filings description: Filing authorization, review requests, and produced output packages. - name: Invoicing description: >- Sales invoicing — drafts, partner seller profiles, e-invoice sending, PDF finalizing, credit notes, reminders, recurring templates, and the invoice-customer register. LAC sends buyer invoices on the e-invoice network only. A partner-profile invoice also sends its legal seller a bookkeeping PDF copy. - name: Payroll description: >- Payroll workspace — employees, tax cards, employer settings, draft runs, and payslips. Every payroll operation (reads included) requires an interactive admin or existing broad-approver session and is NOT available to API keys. - name: Payments description: >- Review and named-human release for source-bound purchase, payroll, and reimbursement payments. Direct Open Payments delivery is the only rail: there is no manual payment composer and no bank or Wise file. A batch that cannot be delivered directly to the bank fails closed rather than becoming the customer's manual task. - name: Connections description: >- Source-system connections (bank, settlement providers, commerce, accounting systems, inbox/Gmail, Google Sheets) and service-connection requests/confirmations. PayPal connects with the company's own PayPal app, whose Client ID and Secret this API accepts, or with PayPal partner consent, which depends on PayPal approving LAC as a partner and returns a URL that a company admin must open. Other browser-interactive consent flows remain portal-only. - name: Shopify App description: >- Public Shopify App Home, App Bridge token exchange, installation handoff, and mandatory privacy webhooks. Offline access tokens never enter a browser. - name: Imports description: Historical import runs (e.g. migrated books) and their artifacts. - name: API keys description: >- Manage portal API keys. These endpoints require an interactive admin session (Firebase token) and are NOT available to API-key bearers, which receive 403. - name: Lens description: >- Typed, display-ready read models over the books: the transactions window (full row universe, three-state status, keyset pagination), the per-row booking view, data coverage, and the connections catalog. - name: Accounting description: >- The accountant's read models: general ledger, journal entries, context cards, the filings strip with previews, and the SQL explorer. Every endpoint here requires LAC staff access or the company admin role; other bearers receive 403. paths: /chat-artifacts/{document_id}: get: tags: - Messages - Documents summary: Download one retained file referenced by chat description: >- Returns retained bytes only when the exact document and SHA-256 are referenced by a visible human chat message or committed on a terminal Björn receipt. A document row, hidden transport, unauthorized internal message, or another tenant's reference is never sufficient authority. operationId: downloadChatArtifact parameters: - name: document_id in: path required: true schema: type: string minLength: 1 maxLength: 300 - $ref: '#/components/parameters/CustomerIdQuery' responses: '200': description: Exact retained attachment bytes. headers: Content-Disposition: schema: type: string content: application/octet-stream: {} '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '404': description: No customer-visible receipt attachment has this document ID. '503': description: >- The retained object is temporarily unavailable or failed verification. components: parameters: CustomerIdQuery: name: customer_id in: query required: false description: >- Target company. Optional — API keys are pinned to one company, and single-company sessions default to it. schema: type: string responses: Unauthorized: description: Missing or invalid bearer token. content: application/json: schema: $ref: '#/components/schemas/Error' Forbidden: description: >- Insufficient scope or role — e.g. a read-scoped key on a mutating method, or an API key on an interactive-session-only endpoint. content: application/json: schema: $ref: '#/components/schemas/Error' schemas: Error: type: object description: Standard error envelope. properties: error: type: string description: Machine-readable error message. detail: type: string description: Human-readable detail. securitySchemes: apiKey: type: http scheme: bearer bearerFormat: lac_sk_... description: >- Portal API key minted in portal Settings → API access. Scope `read` or `write`; pinned to one company. Send as `Authorization: Bearer lac_sk_...`. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.