accounted/CLAUDE.md

CLAUDE.md — Gnubok

Project Overview

gnubok is a Swedish-focused accounting SaaS for sole traders (enskild firma) and limited companies (aktiebolag). It implements double-entry bookkeeping compliant with Swedish accounting law (Bokforingslagen), including VAT handling, tax reporting, and 7-year document retention. Multi-tenant: each user can own or be a member of multiple companies, optionally grouped into teams (for consultants).

Tech stack: Next.js 16.1.5 (App Router), React 19.2.3, TypeScript 5 (strict), Zod 4, Supabase (PostgreSQL + RLS + email/password + TOTP MFA auth), Tailwind CSS 4 + shadcn/ui, Vercel hosting, Docker (self-hosted).

Integrations: Enable Banking (PSD2), TIC Identity, Anthropic SDK, AWS Bedrock, OpenAI, Resend, Sentry, Svix, web-push, Upstash Redis, Google Drive, JSZip, sharp, Framer Motion, Recharts, PDF.js, @react-pdf/renderer, xlsx, fuse.js, ics.

Path alias: @/* maps to the project root. Language: All code, comments, and commit messages in English. License: AGPL-3.0-or-later.

---

Commands

npm run dev              # Start dev server (runs setup:extensions first)
npm run build            # Production build (runs setup:extensions first)
npm run lint             # ESLint
npm test                 # Run all Vitest tests
npx vitest run <dir>     # Run tests in a specific directory
npm run setup:extensions # Regenerate extension registry from extensions.config.json
npm run skills:generate  # Regenerate agent_atom_registry seed migration from .claude/skills/**/SKILL.md (after editing a SKILL.md)
npm run skills:check     # CI guard: fail if a SKILL.md changed without regenerating the seed migration

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Key Architectural Relationships

• Multi-tenant model: companies owns all business data. company_members links users to companies (owner/admin/member/viewer). teams group companies. Context resolved via gnubok-company-id cookie in lib/supabase/middleware.ts.
• All journal entry creation routes through lib/bookkeeping/engine.ts. Lifecycle: createDraftEntry() → commitEntry() (atomic voucher via commit_journal_entry RPC). createJournalEntry() does both. Reversal: reverseEntry(). Correction: correctEntry() in lib/core/bookkeeping/storno-service.ts.
• API routes emitting events must call ensureInitialized() (lib/init.ts) at module level to load extensions and wire handlers.
• Event bus (lib/events/bus.ts) is a module-level singleton using Promise.allSettled. 36 event types in lib/events/types.ts. Persisted to event_log table (30-day TTL).
• Supabase clients: browser (client.ts), server cookies (createClient()), service role (createServiceClient()), cookieless service role for API keys (createServiceClientNoCookies()). Pagination: fetchAllRows().
• Extension system: Opt-in via extensions.config.json. Core runs with zero extensions. Enabled: enable-banking, email, arcim-migration, tic, mcp-server, cloud-backup.
• Core reports (lib/reports/): balance sheet, income statement, trial balance, general ledger, AR/supplier ledger + reconciliation, VAT declaration, journal register, monthly breakdown, continuity check, opening balances, KPI, NE-bilaga, INK2, SIE export, full archive, salary journal, vacation liability, avgifter basis.
• Types: Shared types in types/index.ts (~2,570 lines). Import via import type { T } from '@/types'. Event types in lib/events/types.ts. Extension types in lib/extensions/types.ts.
• Error messages: lib/errors/get-error-message.ts maps to Swedish (Zod → Postgres → HTTP → fallback).

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Multi-Tenant Architecture

• companies: Business unit. All business data has a company_id column.
• company_members: Roles owner/admin/member/viewer, source direct|team.
• teams: Consultant grouping. Team members auto-sync to company_members via DB triggers.
• user_preferences: Stores active_company_id.

Context resolution (lib/supabase/middleware.ts): cookie → user_preferences.active_company_id → first membership. RLS uses user_company_ids() helper.

Invitations: company_invitations/team_invitations with gnubok_inv_ tokens (SHA-256, 7-day TTL). See lib/auth/invite-tokens.ts.

---

Authentication

Supabase Auth: email+password (primary), magic link (fallback), TOTP MFA. MFA enforced application-side (middleware + API routes), not in RLS.

• NEXT_PUBLIC_SELF_HOSTED=true → MFA never enforced
• NEXT_PUBLIC_REQUIRE_MFA=true → middleware redirects to /mfa/enroll or /mfa/verify until AAL2

API route auth (lib/auth/require-auth.ts): requireAuth() returns { user, supabase, error }, enforces MFA on hosted. API keys (lib/auth/api-keys.ts): SHA-256 hashed, gnubok_sk_ prefix. Scoped via TOOL_SCOPE_MAP. Rate limited 100 RPM via validate_and_increment_api_key RPC. Cron auth (lib/auth/cron.ts): verifyCronSecret() constant-time comparison.

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Core Bookkeeping Engine

The engine (lib/bookkeeping/engine.ts) is the most critical system. All accounting flows route through it.

Lifecycle: createDraftEntry() → commitEntry() (atomic voucher via commit_journal_entry RPC). createJournalEntry() does both. reverseEntry() for storno; correctEntry() (lib/core/bookkeeping/storno-service.ts) for corrections.

Engine files: transaction-entries.ts, invoice-entries.ts (with generatePerRateLines() for mixed-rate), supplier-invoice-entries.ts, vat-entries.ts, currency-revaluation.ts, mapping-engine.ts, booking-templates.ts/counterparty-templates.ts, propose-payment-lines.ts/propose-send-lines.ts, handlers/supplier-invoice-handler.ts.

BAS data (bookkeeping/bas-data/): Full BAS 2026 chart by class (1–8) + SRU mapping.

Key BAS Accounts

1510 Accounts receivable | 1930 Business bank account | 2013 Private withdrawals (EF) | 2440 Accounts payable | 2611/2621/2631 Output VAT 25%/12%/6% | 2641 Input VAT | 2645 Calculated input VAT (EU) | 2893 Shareholder loan (AB) | 3001/3002/3003 Revenue 25%/12%/6% | 3305/3308 Export/EU service revenue

VAT Treatments

standard_25, reduced_12, reduced_6, reverse_charge, export, exempt

Invoice items support individual vat_rate values (mixed-rate invoices). Use getAvailableVatRates(customerType, vatNumberValidated) from lib/invoices/vat-rules.ts. VIES validation via lib/vat/vies-client.ts.

VAT Declaration Rutor (SKV 4700)

VatDeclarationRutor type maps to momsdeklaration:

• Ruta 05: Domestic taxable sales (3001+3002+3003)
• Ruta 06/07: Unused, always 0
• Ruta 10/11/12: Output VAT 25%/12%/6% (2611/2621/2631)
• Ruta 39/40: EU services / Export (3308/3305)
• Ruta 48: Input VAT (2641/2645)
• Ruta 49: Moms att betala/återfå = (10+11+12+30+31+32+60+61+62) − 48

---

Core Services (lib/core/)

• bookkeeping/period-service.ts — Fiscal period lifecycle management (open, close, lock)
• bookkeeping/year-end-service.ts — Year-end closing procedures
• bookkeeping/storno-service.ts — Reversal/correction entry generation
• tax/tax-code-service.ts — Tax code definitions and rates
• audit/audit-service.ts — Audit trail and compliance logging
• documents/document-service.ts — Document attachment lifecycle (WORM storage with version chains)

---

Accounting Guard Rails

These rules exist for legal compliance, enforced by database triggers. Never violate them.

1. Committed entries are immutable. Once status: 'posted', cannot be edited or deleted (DB trigger).
2. Never delete posted entries. Use reverseEntry() (storno) to cancel.
3. Every entry must balance. sum(debits) === sum(credits), both > 0.
4. Voucher numbers are sequential. Assigned atomically via commit_journal_entry DB RPC. Never set manually.
5. Voucher gap documentation. BFNAR 2013:2 requires documented explanations for gaps (voucher_gap_explanations table, detect_voucher_gaps RPC).
6. Period lock enforcement. DB trigger blocks writes to closed/locked periods. Company-wide lock date enforced via enforce_company_lock_date() trigger.
7. 7-year document retention. DB triggers prevent deletion of documents linked to posted entries.
8. Storno, never edit. Use correctEntry() from lib/core/bookkeeping/storno-service.ts.
9. Use Math.round(x * 100) / 100 for monetary calculations. Never toFixed().
10. Always use engine functions. Never insert directly into journal tables.
11. Account numbers are strings. '1930', never 1930.

---

Extension System

Extensions are opt-in plugins in extensions/general/<name>/, controlled by extensions.config.json. Core runs with zero extensions. npm run setup:extensions generates static imports in lib/extensions/_generated/ (auto via predev/prebuild). Extensions cannot use dynamic imports.

Available (12): Enabled — enable-banking (PSD2), email (Resend), arcim-migration, tic (org lookup), mcp-server, cloud-backup (Google Drive). Disabled — inbox-smart-match, invoice-inbox, push-notifications, calendar, skatteverket, example-logger.

Registration (lib/extensions/registry.ts): Singleton. register() wires handlers. get(id), getAll(), getByCapability(key). Context (lib/extensions/context-factory.ts): ExtensionContext = userId, companyId, extensionId, supabase, emit(), settings, storage, log, services. API routes: app/api/extensions/ext/[...path]/route.ts catch-all → /api/extensions/ext/{extensionId}/{routePath}. Path params as _paramName query. Service patterns: Interface registration (email — registerEmailService()/getEmailService()) or services record (extension exposes via services property). Creating: npx tsx scripts/create-extension.ts --name my-ext --sector general --category operations --description "...".

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MCP Server & API Keys

gnubok exposes its bookkeeping engine as an MCP server for Claude Desktop/Code.

MCP extension (extensions/general/mcp-server/): 35 tools covering transactions, categorization, customers/suppliers, invoices, accounts, fiscal periods, reports (trial balance, GL, BS, IS, AR/supplier ledger, VAT, KPI), reconciliation, salary runs, AGI, document upload. JSON-RPC 2.0. Endpoint: /api/extensions/ext/mcp-server/mcp.

API keys (lib/auth/api-keys.ts, api_keys table): SHA-256, gnubok_sk_ prefix, scoped via TOOL_SCOPE_MAP, 100 RPM via validate_and_increment_api_key RPC. createServiceClientNoCookies() — all queries filter by company_id (defense in depth).

OAuth 2.1 for Claude connectors: .well-known/oauth-protected-resource + .well-known/oauth-authorization-server discovery; /api/mcp-oauth/authorize, /token (PKCE), /register. Stateless AES-256-GCM auth codes (lib/auth/oauth-codes.ts). Single-use via oauth_used_codes. Allowlist: claude.ai/api/*, claude.com/api/*, localhost.

npm package (packages/gnubok-mcp): Stdio-to-HTTP bridge; users run npx gnubok-mcp with API key.

Tool authoring conventions (enforced by tests):

• Every inputSchema must declare additionalProperties: false at the top level. Guarded by extensions/general/mcp-server/__tests__/strict-schemas.test.ts.
• Tool descriptions must be ≤ 280 chars (guarded by output-schema.test.ts). No Args: / Returns: / Examples: blocks — those belong in JSON Schema, not description prose. Use agent-native hints like "Use to…" / "Call X first" instead.
• Completion-signal pattern: write tools that stage operations return STAGED_OPERATION_SCHEMA (server.ts:495) — { staged, risk_level, actor, message, preview, period_status?, next? }. The staged: true boolean is the explicit completion signal; agents must not infer completion from prose. Do NOT introduce a parallel { success, shouldContinue, output } envelope.
• Tools that touch a fiscal-period-bound date (categorize, mark paid, create voucher, correct/reverse entry, approve supplier invoice) pass dateForPeriodCheck to stagePendingOperation so the response includes period_status: { period_id, status: open|locked|closed, lock_date }. Widgets and agents use this to disable writes without round-trips.

---

API Route Pattern

import { createClient } from '@/lib/supabase/server'
import { NextResponse } from 'next/server'
import { ensureInitialized } from '@/lib/init'
import { validateBody } from '@/lib/api/validate'
import { MySchema } from '@/lib/api/schemas'

ensureInitialized()  // Module-level — loads extensions for event emission

export async function POST(request: Request) {
  const supabase = await createClient()
  const { data: { user } } = await supabase.auth.getUser()
  if (!user) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })

  const result = await validateBody(request, MySchema)
  if (!result.success) return result.response

  // Business logic... always filter by company_id (defense in depth alongside RLS)
  return NextResponse.json({ data: result })
}

• Dynamic route params: { params }: { params: Promise<{ id: string }> } (Next.js 16)
• Response shapes: { data } for success, { error } for failures
• Zod schemas in lib/api/schemas.ts — 30+ schemas with shared primitives (uuid, isoDate, accountNumber, nonNegativeAmount)

---

Key lib/ Directories

• bookkeeping/ — Engine, entry generators, mapping, templates, BAS data
• core/ — Period, year-end, storno, tax codes, audit, documents
• events/ — Bus singleton, 36 event types, event log handler
• auth/ — API keys, require-auth/write, MFA, OAuth codes, invite tokens, cron, BankID
• supabase/ — Clients, middleware, fetchAllRows pagination
• api/ — Zod validation (validateBody/validateQuery), schemas
• reports/ — 20 report generators
• invoices/ — Matching, payment log, reminders, VAT rules, PDF
• transactions/ — ingest.ts, AI suggestions
• import/ — SIE, bank file, opening balance, account mapper
• documents/ — Matchers (single + batch)
• extensions/ — Registry, loader, context factory
• email/ — Service interface, Resend, templates
• company/ — Context resolution, CRUD, fiscal period computation
• providers/ — Fortnox, Bokio, Briox, BL, Visma (OAuth, retry, consent)
• salary/ — Payroll engine, tax tables, AGI, KU, payslips, löneväxling, personnummer
• processing-history/, reconciliation/, tax/, vat/ (VIES, MOMS box), deadlines/, currency/ (Riksbanken), skatteverket/, bankgiro/ (Luhn), calendar/ (ICS)
• errors/ — Swedish error mapping (Zod → Postgres → HTTP → fallback)
• rate-limits/ — Postgres-backed checkInboxUploadRateLimit via check_and_increment_inbox_quota RPC; fails open
• hooks/, logger.ts, support.ts, utils.ts (cn(), formatCurrency(), formatDate(), formatOrgNumber())

---

App Routes

Pages: /login, /register, /reset-password, /mfa/{enroll,verify}, /onboarding, /companies/new, /invite/[token], / (dashboard), /transactions, /invoices[/new|/[id]|/[id]/credit], /supplier-invoices[/new|/[id]], /customers[/[id]], /suppliers[/[id]], /expenses[/new|/[id]], /receipts[/scan], /bookkeeping[/[id]|/year-end], /salary[/employees|/runs], /reports, /import, /kpi, /deadlines, /pending, /help, /extensions[/[sector]/[ext]], /e/[sector]/[slug] (workspace), /settings/*, /dpa, /privacy, /invoice-action/[token], /sandbox.

API endpoints:

• /api/bookkeeping/* — accounts, fiscal periods, journal entries (CRUD/reverse/correct), mapping rules, voucher gaps
• /api/invoices/*, /api/supplier-invoices/* — CRUD + state transitions
• /api/transactions/* — categorize, describe, book, match-{invoice,supplier-invoice}, batch, AI suggestions
• /api/customers/*, /api/suppliers/* — CRUD
• /api/documents/* — CRUD, versions, link, match-sweep, verify cron
• /api/reports/* — 19 endpoints (GL, TB, BS, IS, AR/supplier ledger, VAT, SIE, INK2, NE-bilaga, KPI, audit, continuity, monthly, full-archive, salary, vacation, avgifter)
• /api/salary/* — employees, payroll-config, tax-tables, KU, runs
• /api/import/* — bank-file, SIE (parse/execute/mappings)
• /api/reconciliation/bank/*, /api/settings/*, /api/company/*, /api/team/*
• /api/deadlines/*, /api/tax-deadlines/* — CRUD + crons
• /api/pending-operations/*, /api/events/*, /api/audit-trail/*
• /api/calendar/feed/[token], /api/mcp-oauth/*, /api/support/contact, /api/account/delete
• /api/log, /api/health, /api/vat/validate, /api/currency/rate, /api/sandbox/*
• /api/extensions/ext/[...path] — dynamic extension routes

---

Testing

Framework: Vitest 4, node env, tests in __tests__/. Scope: lib/ and app/api/. No component/E2E tests.

Helpers (tests/helpers.ts): createMockSupabase(), createQueuedMockSupabase(), createMockRequest(), parseJsonResponse(), createMockRouteParams(), plus fixture factories (makeTransaction, makeJournalEntry, makeInvoice, makeCustomer, makeSupplier, makeSupplierInvoice, makeFiscalPeriod, makeReceipt, makeDocumentAttachment, makeCompany, makeCompanySettings, makeTaxCode, makeSIEVoucher, makeBankConnection, etc.).

Patterns: Always mock @/lib/supabase/server. vi.clearAllMocks() + eventBus.clear() in beforeEach. Test auth (401), validation (400), 404, 500, happy path.

pg-real: Parallel Vitest project for triggers/RPCs/RLS using real Postgres (CI: supabase/postgres:15, migrations replayed). Local: npm run test:pg. File convention *.pg.test.ts. Helpers: tests/pg/setup.ts (getPool(), withUserContext()), tests/pg/fixtures.ts (seedCompany(), insertDraftJournalEntry(), etc.). Required: any PR touching a trigger/RPC/RLS/DEFERRABLE must include or extend a *.pg.test.ts.

---

Database & Migrations

Location: supabase/migrations/ — 118 files. Early migrations use sequential numbering (20240101000001–20240101000038), later ones use real timestamps.

Key Tables (~60)

• Multi-tenant: companies, company_members, company_invitations, teams, team_members, team_invitations, user_preferences, profiles
• Bookkeeping: chart_of_accounts, fiscal_periods, journal_entries, journal_entry_lines, account_balances, voucher_sequences, voucher_gap_explanations
• Invoicing: customers, invoices, invoice_items, invoice_payments, invoice_inbox_items
• Suppliers: suppliers, supplier_invoices, supplier_invoice_items
• Banking: bank_connections, transactions, bank_file_imports, payment_match_log
• Documents: document_attachments (WORM), receipts, receipt_line_items
• Settings: company_settings, mapping_rules, categorization_templates, booking_template_library, extension_data
• Dimensions: cost_centers, projects
• Tax/Deadlines: tax_rates, tax_table_rates, deadlines, calendar_feeds, skatteverket_tokens
• API/Auth: api_keys, oauth_used_codes, bankid_identities
• Audit/Ops: audit_log (immutable), event_log (30d TTL), pending_operations, processing_history, ai_usage_tracking, automation_webhooks
• Inbox: invoice_inbox_items, company_inboxes, email_connections
• Salary: employees, salary_runs, salary_run_employees, salary_line_items, salary_payroll_config, agi_declarations
• Providers: provider_consents, provider_consent_tokens, provider_otc
• Other: sandbox_users

Key RPC Functions

• create_company_with_owner() — Atomic company + owner creation
• commit_journal_entry() — Atomic draft→posted with voucher number
• next_voucher_number() — Concurrent-safe voucher generation
• detect_voucher_gaps() — BFNAR 2013:2 gap detection
• generate_invoice_number(), get_next_arrival_number(), generate_delivery_note_number() — Sequence generators
• seed_chart_of_accounts() — BAS chart seeding per entity type
• validate_and_increment_api_key() — Atomic rate limiting
• user_company_ids() — RLS helper returning user's company IDs
• get_unlinked_1930_lines() — Bank reconciliation helper
• cleanup_sandbox_user(), cleanup_expired_sandbox_users() — Sandbox lifecycle

Key Triggers

• check_journal_entry_balance() — Debit must equal credit
• enforce_journal_entry_immutability() — Posted entries cannot be modified
• enforce_period_lock() — No entries in closed/locked periods
• enforce_company_lock_date() — Company-wide bookkeeping lock date
• block_document_deletion() — WORM compliance
• enforce_retention_journal_entries() — 7-year retention
• audit_log_immutable() — Audit log cannot be modified
• write_audit_log() — Auto-audit on DML operations
• sync_team_member_to_companies() — Auto-sync team→company membership

Migration Rules

1. Enable RLS + policies using user_company_ids() for company-scoped data
2. Add updated_at trigger via update_updated_at_column()
3. UUID PKs: DEFAULT uuid_generate_v4()
4. Company ownership: company_id UUID REFERENCES companies NOT NULL + user_id UUID REFERENCES auth.users ON DELETE CASCADE NOT NULL
5. Never modify existing migrations — create new ones
6. Never modify enforcement triggers (migration 017) — legally required
7. Apply via Supabase MCP apply_migration
8. Always end with NOTIFY pgrst, 'reload schema' when altering table structure

Agent skill bodies (agent_atom_registry): skill content is authored in .claude/skills/**/SKILL.md and inlined into the DB body column at runtime (not read from disk — that doesn't bundle on Vercel/Docker). After editing any SKILL.md, run npm run skills:generate to emit a new *_seed_agent_atom_bodies.sql migration and commit it; npm run skills:check (wired into CI) fails the build if you forget. The MCP server exposes only atoms with mcp_exposed = true (swarm-* audit skills are never atoms).

---

Skills, Git & CI

Skills: Always use /frontend-design for new UI. Use vercel:deploy for deployment. Use /supabase-migration for new migrations. Use /erp-api-route for new API routes. Use /create-extension for new extensions. Use the Swedish domain skills (swedish-sie-import-export, swedish-accounting-compliance, swedish-vat, swedish-invoice-compliance, swedish-payroll, swedish-year-end-closing, swedish-financial-reporting, swedish-sru-filing, swedish-asset-accounting, swedish-project-accounting, swedish-tax-planning) for accounting domain questions.

Git: Conventional commits (feat:, fix:, refactor:, test:, docs:). Atomic commits, branch from main.

CI:

• .github/workflows/core-build.yml — resets extensions to empty, runs build + test, verifies no core code imports from @/extensions/ directly.
• .github/workflows/swedish-compliance-review.yml — Swedish accounting compliance review on PRs touching bookkeeping/reports/tax logic.
• .github/workflows/docker-publish.yml — pushes images to GHCR on main.

Docker (.github/workflows/docker-publish.yml): Pushes to GHCR (erp-mafia/erp-base) on main push. 4-stage Dockerfile (base → deps → builder → runner) with Node 22 Alpine. Runtime env placeholder replacement via docker-entrypoint.sh. Docker Compose with app + supercronic cron service.

---

Deployment

Vercel (Hosted)

Cron jobs in vercel.json: deadline status (6:00), invoice reminders (8:00), tax deadlines (yearly Jan 2), enable-banking sync (5:00), document verify (3:00), sandbox cleanup (4:00), event log cleanup (2:00, 30-day TTL), cloud-backup auto-sync (hourly).

Docker (Self-Hosted)

• Dockerfile: 4-stage Node 22 Alpine build with standalone output
• docker-compose.yml: App service + supercronic cron scheduler
• docker-entrypoint.sh: Validates required env vars, replaces build-time placeholders in .next/static/ JS
• Extension presets: docker/extensions.self-hosted.json, docker/extensions.hosted.json

Environment Variables

Required: NEXT_PUBLIC_SUPABASE_URL, NEXT_PUBLIC_SUPABASE_ANON_KEY, SUPABASE_SERVICE_ROLE_KEY, NEXT_PUBLIC_APP_URL, CRON_SECRET

Auth: NEXT_PUBLIC_REQUIRE_MFA (set true on hosted), NEXT_PUBLIC_SELF_HOSTED (set true for Docker)

Extension-specific (only when extension is enabled): ENABLE_BANKING_APP_ID/ENABLE_BANKING_APP_KEY, ANTHROPIC_API_KEY, OPENAI_API_KEY, RESEND_API_KEY, VAPID_PUBLIC_KEY/VAPID_PRIVATE_KEY

Optional: SENTRY_DSN, SENTRY_AUTH_TOKEN

Other

Never create a NUL/nul file: \gnubok\NUL

---

i18n

The app is Swedish-first and bilingual (Swedish + English) for UI chrome. Locale is per-user on user_preferences.locale ('sv' | 'en', default 'sv'), resolved server-side via next-intl. The user picker lives at /settings/account.

Pattern for new UI:

// Server component
import { getTranslations } from 'next-intl/server'
const t = await getTranslations('namespace')

// Client component
'use client'
import { useTranslations } from 'next-intl'
const t = useTranslations('namespace')

// In JSX
<button>{t('save')}</button>

Add new strings to both messages/sv.json and messages/en.json under the matching namespace (common, nav, auth, settings, empty, etc.). Never ship an English key without a Swedish counterpart — Swedish is the default and the fallback.

Locale-aware formatters:

• formatCurrency(amount) — stays SEK with sv-SE conventions in BOTH locales (Swedish accounting standard, not a UI string).
• formatDate(date) — ISO yyyy-MM-dd, locale-independent.
• formatDateLong(date, locale) — accepts locale. In client components use useFormat() (lib/hooks/use-format.ts) which pulls the active locale.

Error messages: getErrorMessage(err, { locale, context }) from lib/errors/get-error-message.ts is bilingual on the primary maps (Postgres codes, HTTP statuses, context fallbacks, generic fallback). The structured error envelope ({ error: { code, message, message_en } }) already carries both; the function picks the right one from locale. Pass useLocale() / getLocale() as the locale arg.

Stays Swedish — do NOT translate:

Surface	Reason
Invoice PDFs (lib/invoices/pdf-template.tsx)	Customer-facing — driven by customer.language (sv default, en opt-in). The template's chrome translates; statutory chapter refs (ML 17 kap 24§, ML 3 kap.) stay intact in both locales.
Customer email templates (lib/email/invoice-templates.ts, reminder-templates.ts)	Same — customer.language drives the output. reminder-templates.ts is still Swedish-only; mirror the PDF/invoice-templates approach if you add English here.
Year-end wizard (app/(dashboard)/bookkeeping/year-end/page.tsx)	Statutory bokslut terminology; English would be misleading
Journal entry editor (app/(dashboard)/bookkeeping/[id]/page.tsx)	Deeply regulatory (verifikat, voucher numbers, BAS)
INK2 / NE-bilaga / SRU (lib/reports/ink2/**, lib/reports/ne-bilaga/**, lib/reports/sru-*)	Skatteverket forms — field codes and labels are statutory
SIE export (lib/reports/sie-export.ts)	SIE format is Swedish-only by spec (#KONTO, #VER, etc.)
BAS chart names (lib/bookkeeping/bas-data/**)	Standardized Swedish account names per BAS 2026
VAT declaration ruta labels (lib/reports/vat-declaration*.ts)	Momsdeklaration field labels are Skatteverket form labels
Salary AGI / KU (lib/salary/agi*, lib/salary/ku*)	Skatteverket-bound forms
Bookkeeping engine domain errors ("Verifikationen balanserar inte", "Bokföringen är låst")	Regulatory concepts; English equivalents would be ambiguous

Anything in the table above stays Swedish in BOTH locales. If you find yourself reaching for t() inside one of these files, stop and reconsider.

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Design Context

Users

Swedish sole traders (enskild firma) and small business owners (aktiebolag) who need to manage their own bookkeeping. They are not accountants — they are professionals (consultants, freelancers, shop owners) who want to stay compliant without hiring one. They use gnubok in short, focused sessions: sending an invoice, categorizing bank transactions, filing a VAT declaration. Speed and clarity matter — every second spent in the app is a second away from their real work.

Brand & Aesthetic

Editorial monochrome. Paper-white surfaces, hairline borders, serif headlines. The interface should feel like a well-made instrument — considered, quiet, confident. Anti-references: enterprise software (SAP/Oracle density), neon SaaS coldness.

• Palette: Achromatic foundation. Pure white background, warm beige (40 11% 89%) for chips / active sidebar / hover / secondary buttons. Achromatic primary (no cool tint). Semantic colors (--success sage, --warning ochre, --destructive terracotta) exist but are data-only — they appear in charts and financial numbers (positive/negative deltas), never as chrome backgrounds. In chrome, only --destructive survives.
• Typography: Hedvig Letters Serif for display headings, Geist (sans) for body, forms, and tables. Hedvig is single-weight (400) — do not apply font-medium to display text; its natural high-contrast strokes carry the weight. Tabular numbers everywhere financial data appears.
• Surfaces: Cards sit flat on the page — no shadow, full-opacity hairline border (border-border), rounded-lg (8px). Card background matches page background; the border carries hierarchy. Dark mode drops the warm tint from secondary for a pure-gray mood shift; light mode keeps the beige.
• Spacing: Generous whitespace. Dense data (tables, ledgers) uses tighter spacing but never feels cramped.
• Motion: Functional, not decorative. No press-scale, no hover-lift, no spring overshoot. Hover state is a flat background shift (bg-secondary/60). transition-colors duration-150 is the default. Stagger animations on list entry are fine. Respect prefers-reduced-motion (already wired).
• Icons: Lucide — 15px in navigation, slightly larger in empty states.

Design Principles

1. Clarity over cleverness — Swedish labels, obvious hierarchy.
2. Earned minimalism — remove what doesn't serve the task, keep compliance context.
3. Numbers are first-class — tabular-nums, alignment, positive/negative clarity.
4. Trust through consistency.
5. Speed is a feature — optimize for the 90-second session.

Accessibility

WCAG AA (4.5:1 text, 3:1 UI). Keyboard-navigable + visible focus rings. Respect prefers-reduced-motion. Color never sole state indicator. Touch targets ≥40px (44px for mobile-critical). Icon-only buttons need aria-label.

Design System Tokens

These conventions are locked. Don't reinvent them in new code; deviating from them on existing pages is a regression.

Spacing scale. Only use Tailwind values 1, 2, 3, 4, 6, 8, 10, 12. Forbidden: 2.5, 5, hardcoded pixels in page logic.

Token	Tailwind	Use for
4	1	icon padding
8	2	tight inline gaps
12	3	dense list rows, badge gaps
16	4	default form / control / grid gap
24	6	card padding default (p-6)
32	8	between page sections (space-y-8 on page root)
40	10	hero spacing
48	12	top of page after header

Compact metric cards (e.g. dashboard tiles, salary KPI row) use p-4. Detail cards use p-6. Never mix p-5.

Layout.

• Sidebar width: md:w-64 (256px). Main content offset: md:pl-64.
• Main container: max-w-5xl mx-auto px-5 py-8 md:px-8 md:py-10 (via components/dashboard/MainContainer.tsx).
• Page root: <div className="space-y-8">.

Primitives — always use these, don't hand-roll.

Need	Component	Notes
Page title + action	components/ui/page-header.tsx PageHeader	Use this, not bespoke <h1> + <p> blocks. Drop the description prop when it just paraphrases the title.
Data table	components/ui/table.tsx Table / TableHeader / TableHead / TableRow / TableCell	Header style is baked in: text-[11px] font-medium uppercase tracking-wider text-muted-foreground. Wrap in <CardContent className="p-0"> when the table is a card's primary content. Add tabular-nums to numeric cells.
Status indicator	components/ui/badge.tsx <Badge variant>	Variants: default / secondary / success / warning / destructive / outline. Never use raw Tailwind colors (bg-blue-100, bg-emerald-500/10, etc.) for status. Map status → variant via a small Record per feature.
No-data state	components/ui/empty-state.tsx EmptyState	Don't hand-roll <div className="flex flex-col items-center py-12">…</div>. Preset variants exist (EmptyInvoices, EmptyCustomers, EmptyTransactions, etc.).
Loading placeholder	components/ui/skeleton.tsx <Skeleton>	Don't hand-roll bg-muted rounded animate-pulse divs.
Inline help / formulas	components/ui/info-tooltip.tsx InfoTooltip	Hover-revealed; don't use always-visible info buttons.
Fiscal year picker	components/common/FiscalYearSelector.tsx	Don't use raw <select> for fiscal periods.

Tabular display rules.

• All financial values get tabular-nums.
• Dates in tables: tabular-nums for fixed width.
• Right-align numeric columns (text-right).
• For group bands inside tables (Resultatrapport-style): <tr className="bg-muted/30"><td colSpan={n} className="px-4 py-2 text-[12px] font-semibold text-muted-foreground">{label}</td></tr>.

Date formatting. Two helpers in lib/utils.ts:

• formatDate(x) → 2026-05-11 (ISO yyyy-MM-dd). Use for accounting data — transaction dates, invoice dates, payment dates, voucher dates. Aligns in tables, matches SIE/BFL convention.
• formatDateLong(x) → 11 maj 2026 (Swedish long form). Use for metadata — when something was created, linked, verified, expires. Settings panels and audit displays.

Never render raw {x.invoice_date} directly — always route through formatDate() for code consistency.

Currency. formatCurrency(n, currency?) from lib/utils.ts. Default SEK.

Typography.

• Page title: use PageHeader (renders font-display text-3xl md:text-4xl tracking-tight). Do not hand-roll an <h1>.
• Card title: <CardTitle className="text-base"> for sections, default for primary cards. The primitive already drops font-medium — do not add it back.
• Section divider header inside a page: <h2 className="text-sm font-medium uppercase tracking-wider text-muted-foreground">.
• Headline number: font-display text-xl tabular-nums. No font-medium — Hedvig's natural weight carries the gravitas.
• Display font (font-display, Hedvig Letters Serif) reserved for h1/h2/h3 and primary financial numbers. If a specific font-display numeral reads weak inside a compact metric card, override that call site with font-sans tabular-nums (Geist) — better legibility on small numerals.

Forbidden / dead patterns.

• Page descriptions that paraphrase the page title (e.g. <PageHeader title="Fakturor" description="Hantera dina fakturor">) → drop the description.
• Two different status indicators on the same element (e.g. colored card border and Badge for status) → pick one (prefer Badge).
• Mobile-specific <select> duplicating desktop tabs in code — use a single Tabs primitive or a single grouped Select.
• Hand-rolled icon buttons smaller than h-10 w-10. Use shadcn Button size="icon".
• Color-coded status using full-rainbow Tailwind palette (bg-amber-100, bg-emerald-500/10, etc.). Use Badge variants tied to the brand palette.
• shadow-sm / shadow-md / shadow-lg on cards, buttons, or list items. The aesthetic is flat-with-hairlines — surfaces use border-border, not elevation. Shadows survive only on dialogs/popovers/dropdowns (anything that overlays the page).
• active:scale-[...] on buttons. Buttons do not bounce.
• bg-gradient-to-* on page or card backgrounds. Flat surfaces only.
• font-medium on display elements (font-display, h1/h2/h3, CardTitle, PageHeader title). Hedvig is single-weight by design.
• rounded-xl (12px) on cards. Cards are rounded-lg (8px). rounded-xl survives only on prominent hero-style surfaces if absolutely needed.
• Opacity-suffixed border classes (border-border/30, border-border/60) on cards and primary surfaces. Use full-opacity border-border — the new border token is calibrated for that.