accounted/CLAUDE.md

CLAUDE.md — erp-base

Project Overview

erp-base 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.

Tech stack: Next.js 16 (App Router), React 19, TypeScript (strict), Supabase (PostgreSQL + RLS + magic link auth), Tailwind CSS 4 + shadcn/ui, Vercel hosting.

Integrations: Enable Banking (PSD2), Anthropic SDK, OpenAI (embeddings), Resend (email), web-push (VAPID).

Path alias: @/* maps to the project root (tsconfig.json).

Language: All code, comments, and commit messages must be in English.

---

Commands

npm run dev          # Start development server
npm run build        # Production build
npm run lint         # ESLint
npm test             # Run all Vitest tests
npx vitest run <dir> # Run tests in a specific directory

---

Architecture

app/
  (auth)/                 Login, auth callback
  (onboarding)/           6-step setup wizard
  (dashboard)/            Authenticated routes (invoices, customers, transactions,
                          bookkeeping, reports, suppliers, supplier-invoices,
                          receipts, settings, calendar, help, import)
  (public)/               Public invoice action links (no auth)
  api/                    API routes organized by domain

components/
  ui/                     shadcn/ui primitives (button, card, dialog, table, etc.)
  bookkeeping/            Chart of accounts manager, account combobox, add/edit dialogs
  calendar/               Calendar views, deadline cards, payment summary, todo widgets
  chat/                   ChatWidget, ChatPanel, ChatInput, ChatMessage
  dashboard/              DashboardContent, DashboardNav, FSkattWarningCard
  reports/                Report views (including BankReconciliationView)
  settings/               CalendarFeedSettings
  [feature]/              Feature-organized components (invoices, suppliers, import, etc.)

extensions/               First-party extension implementations
  ai-categorization/      AI-powered transaction categorization
  ai-chat/                Claude-based chat assistant
  enable-banking/         PSD2 bank integration via Enable Banking (JWT auth, sync)
  ne-bilaga/              NE tax form attachment generation
  push-notifications/     Web push notification system
  receipt-ocr/            Receipt image OCR processing
  sru-export/             SRU file export
  example-logger/         Minimal reference extension (not loaded by default)

lib/
  bookkeeping/            Core journal entry engine and all entry generators
    engine.ts             Draft/commit workflow, balance validation, voucher numbering
    invoice-entries.ts    Sales invoice journal entries (supports per-line VAT rates)
    transaction-entries.ts Bank transaction journal entries
    supplier-invoice-entries.ts Purchase invoice journal entries
    category-mapping.ts   Category-to-BAS-account mapping
    mapping-engine.ts     Rule-based auto-categorization (MCC codes, merchant patterns)
    vat-entries.ts        VAT line generation
    bas-reference.ts      BAS account catalog (~180 accounts with metadata, SRU codes)
    account-descriptions.ts Human-readable account name lookup
    validate-period-duration.ts Fiscal period duration validation (BFL 3 kap.)
  core/
    bookkeeping/          Period service, storno reversal, year-end closing
    documents/            Document archive (upload, versioning, SHA-256 integrity)
    audit/                Audit trail service
    tax/                  Tax code service
  calendar/               Calendar and scheduling utilities
  currency/               Riksbanken exchange rates
  customers/              Customer management helpers
  deadlines/              Tax deadline tracking
  email/                  Email service (Resend integration)
  events/                 Event bus (bus.ts, types.ts)
  extensions/             Extension registry, loader, types
  import/                 SIE and bank file parser
    bank-file/            Bank file parser with format modules
      formats/            camt053, generic-csv, handelsbanken, nordea, seb, swedbank
  invoice/                VAT rules, invoice matching (vat-rules.ts, invoice-matching.ts)
  invoices/               Invoice business logic (reminder-processor)
  reconciliation/         Bank reconciliation engine (4-pass matching algorithm)
  reports/                Financial reports (trial-balance, income-statement,
                          balance-sheet, vat-declaration, sie-export,
                          supplier-ledger, supplier-reconciliation,
                          general-ledger, journal-register,
                          ar-ledger, ar-reconciliation, monthly-breakdown)
  supabase/               Client setup (client.ts = browser, server.ts = server/admin,
                          fetch-all.ts = pagination helper for large queries)
  tax/                    Tax calculations, deadlines, Swedish holidays
  transactions/           Transaction processing helpers
  init.ts                 Extension loader (idempotent, called by API routes)
  utils.ts                Shared utility functions

types/index.ts            Canonical type definitions (120+ types, single source of truth)
types/chat.ts             Chat-specific type definitions
tests/helpers.ts          Mock factories and fixture builders
supabase/migrations/      SQL migration files
scripts/                  Utility scripts (clear-user-data.sql)
dev_docs/                 Extensive project documentation (PRD, architecture, BAS guide, etc.)

Key Relationships

• All journal entry creation routes through lib/bookkeeping/engine.ts. The entry generators (invoice-entries.ts, transaction-entries.ts, supplier-invoice-entries.ts) call createJournalEntry() from the engine.
• API routes that emit events must call ensureInitialized() (from lib/init.ts) at module level to load extensions.
• Event bus (lib/events/bus.ts) is a module-level singleton. Core services emit, extensions subscribe.
• Supabase clients: browser (lib/supabase/client.ts), server with user cookies (createClient() from lib/supabase/server.ts), and service role (createServiceClient()).

---

Core Bookkeeping Engine

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

Journal Entry Lifecycle

1. createDraftEntry(userId, input) — Creates entry with status: 'draft', voucher_number: 0. Validates balance. Emits journal_entry.drafted.
2. commitEntry(userId, entryId) — Assigns voucher number via DB RPC (next_voucher_number, concurrent-safe). Sets status: 'posted'. DB trigger sets committed_at. Emits journal_entry.committed.
3. createJournalEntry(userId, input) — Convenience: draft + commit in one call. This is what all entry generators use.
4. reverseEntry(userId, entryId) — Storno reversal: swaps debit/credit, links via reverses_id/reversed_by_id. Original marked 'reversed'.

Entry Generators

Function	File	Purpose
createInvoiceJournalEntry()	invoice-entries.ts	Debit 1510, Credit 30xx + 26xx VAT (per-line VAT rates)
createInvoicePaymentJournalEntry()	invoice-entries.ts	Debit 1930, Credit 1510
createCreditNoteJournalEntry()	invoice-entries.ts	Reverses original invoice entry (per-rate lines)
createInvoiceCashEntry()	invoice-entries.ts	Cash method: revenue + VAT at payment (per-rate)
createTransactionJournalEntry()	transaction-entries.ts	Maps bank transactions via MappingResult
createSupplierInvoiceRegistrationEntry()	supplier-invoice-entries.ts	Debit expense + 2641, Credit 2440
createSupplierInvoicePaymentEntry()	supplier-invoice-entries.ts	Debit 2440, Credit 1930

Key BAS Accounts

Account	Description
1510	Accounts receivable
1930	Business bank account
2013	Private withdrawals (enskild firma)
2440	Accounts payable
2611 / 2621 / 2631	Output VAT 25% / 12% / 6%
2614	Output VAT reverse charge
2641	Input VAT (deductible)
2645	Calculated input VAT (EU reverse charge)
2893	Loan from shareholders (aktiebolag)
3001 / 3002 / 3003	Revenue by VAT rate (25% / 12% / 6%)
3305 / 3308	Export / EU service revenue
3960 / 7960	Exchange rate gains / losses

VAT Treatments

standard_25, reduced_12, reduced_6, reverse_charge, export, exempt

Per-Line VAT

Invoice items support individual vat_rate values, enabling mixed-rate invoices. The helper generatePerRateLines() in invoice-entries.ts groups items by VAT rate and creates separate revenue + VAT account lines per rate group. Available rates depend on customer type — use getAvailableVatRates(customerType, vatNumberValidated) from lib/invoice/vat-rules.ts.

Bank Reconciliation

The reconciliation engine (lib/reconciliation/bank-reconciliation.ts) matches bank transactions to journal entry lines on account 1930 using a 4-pass algorithm:

Pass	Method	Confidence	Match Criteria
1	auto_exact	0.95	Exact amount + exact date
2	auto_reference	0.90	Exact amount + reference/description match
3	auto_date_range	0.85	Exact amount + date within ±3 days
4	auto_fuzzy	0.75	Fuzzy amount (±0.01) + exact date

Manual linking (manual method) is also supported. Only SEK transactions are reconciled. Greedy assignment prevents double-matching.

---

Accounting Guard Rails

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

1. Committed entries are immutable. Once status: 'posted', an entry cannot be edited or deleted. Enforced by DB trigger enforce_journal_entry_immutability.
2. Never delete posted entries. Use reverseEntry() (storno) to cancel. The reversal creates a new entry with swapped debit/credit and bidirectional linking.
3. Every entry must balance. sum(debits) === sum(credits), both must be > 0. Checked by validateBalance() before insert.
4. Voucher numbers are sequential. Assigned via DB RPC next_voucher_number (concurrent-safe). Never set manually.
5. Period lock enforcement. DB trigger enforce_period_lock blocks writes to closed/locked fiscal periods. Check period status before creating entries.
6. 7-year document retention. DB triggers prevent deletion of documents linked to posted entries. retention_expires_at is auto-calculated as period_end + 7 years.
7. Storno, never edit. To correct an error: reverse the wrong entry, then create a new correct one. Use correctEntry() from lib/core/bookkeeping/storno-service.ts for atomic correction.
8. Use Math.round(x * 100) / 100 for all monetary calculations. Never use toFixed() (returns strings, has rounding edge cases).
9. Always use engine functions. Never insert directly into journal_entries or journal_entry_lines tables. Always go through lib/bookkeeping/engine.ts.
10. Account numbers are strings. BAS account numbers like '1930' are always strings, never numbers.

---

Extension Development

Extensions are first-party plugins in the /extensions/ directory, loaded statically at startup.

Creating a New Extension

1. Create extensions/<name>/index.ts
2. Export an object implementing the Extension interface from lib/extensions/types.ts
3. Add a static import to the FIRST_PARTY_EXTENSIONS array in lib/extensions/loader.ts
4. Extensions cannot use dynamic imports (Next.js bundling constraint)

Extension Interface

interface Extension {
  id: string              // Unique identifier (e.g. 'receipt-ocr')
  name: string            // Display name
  version: string         // Semver

  // Surfaces (all optional)
  routes?: RouteDefinition[]
  apiRoutes?: ApiRouteDefinition[]
  sidebarItems?: SidebarItem[]
  eventHandlers?: ExtensionEventHandler[]
  mappingRuleTypes?: MappingRuleTypeDefinition[]
  reportTypes?: ReportDefinition[]
  settingsPanel?: SettingsPanelDefinition
  taxCodes?: TaxCodeDefinition[]
  dimensionTypes?: DimensionDefinition[]

  // Lifecycle hooks
  onInstall?(ctx: ExtensionContext): Promise<void>
  onUninstall?(ctx: ExtensionContext): Promise<void>
}

Minimal Example

See extensions/example-logger/index.ts:

import type { Extension } from '@/lib/extensions/types'
import type { EventPayload } from '@/lib/events/types'

export const myExtension: Extension = {
  id: 'my-extension',
  name: 'My Extension',
  version: '0.1.0',
  eventHandlers: [
    {
      eventType: 'journal_entry.committed',
      handler: async (payload: EventPayload<'journal_entry.committed'>) => {
        // React to committed journal entries
      },
    },
  ],
}

Available Event Types

All defined in lib/events/types.ts:

Event	Payload
journal_entry.drafted	{ entry, userId }
journal_entry.committed	{ entry, userId }
journal_entry.corrected	{ original, storno, corrected, userId }
document.uploaded	{ document, userId }
invoice.created	{ invoice, userId }
invoice.sent	{ invoice, userId }
invoice.paid	{ invoice, transaction, kursdifferens?, userId }
invoice.overdue	{ invoice, days, userId }
credit_note.created	{ creditNote, userId }
transaction.synced	{ transactions[], userId }
transaction.categorized	{ transaction, account, taxCode, userId }
bank.statement_received	{ statement, userId }
bank.payment_notification	{ notification, userId }
period.locked	{ period, userId }
period.year_closed	{ period, userId }
customer.created	{ customer, userId }
customer.pseudonymized	{ customerId, userId }
receipt.extracted	{ receipt, documentId, confidence, userId }
receipt.matched	{ receipt, transaction, confidence, autoMatched, userId }
receipt.confirmed	{ receipt, businessTotal, privateTotal, userId }
transaction.reconciled	{ transaction, journalEntryId, method, userId }
audit.security_event	{ event, userId }

Event Bus Behavior

• Handlers run concurrently via Promise.allSettled — a failing handler never crashes the emitter
• Module-level singleton, persists across requests in the same process
• One-way: core services emit, extensions subscribe
• Call eventBus.clear() in tests to reset state

---

Testing Guidelines

Scope

Test business logic in lib/ and API routes in app/api/. No component tests, no E2E tests.

Framework

Vitest 4 with globals: true and environment: 'node'. Config in vitest.config.ts.

Test Location

Colocated __tests__/ directories alongside source files in lib/.

Test Helpers (tests/helpers.ts)

Supabase mock:

const { supabase, mockResult } = createMockSupabase()
mockResult({ data: makeTransaction(), error: null })
// supabase.from('x').select('*').eq('id', '1') resolves to the mocked result

Fixture factories (all accept Partial<T> overrides):

• makeReceipt() — Receipt with default merchant, amounts, dates
• makeTransaction() — Transaction with default category, amount
• makeFiscalPeriod() — FiscalPeriod with default date range
• makeJournalEntry() — Posted JournalEntry with voucher number
• makeJournalEntryLine() — Line with account number, zero amounts
• makeDocumentAttachment() — Document with hash, storage path
• makeTaxCode() — TaxCode with default output VAT 25%

Patterns

• Always mock @/lib/supabase/server to avoid real DB calls
• Use vi.clearAllMocks() and eventBus.clear() in beforeEach
• Test balance validation edge cases (floating point precision, zero amounts)
• Test error paths (missing fiscal period, unbalanced entries)
• Verify events are emitted correctly

API Route Tests

• Colocated __tests__/ directories alongside route files (e.g., app/api/invoices/__tests__/route.test.ts)
• Mock @/lib/supabase/server, @/lib/init, and lib functions — do NOT re-test lib business logic
• Use createMockRequest(), parseJsonResponse(), createMockRouteParams() from tests/helpers.ts
• Use createQueuedMockSupabase() for routes with multiple sequential Supabase calls
• Test: auth (401), validation (400), not found (404), errors (500), happy path, non-blocking journal entry failures

Reference Tests

• lib/bookkeeping/__tests__/engine.test.ts — Balance validation
• lib/bookkeeping/__tests__/invoice-entries.test.ts — Per-line VAT, mixed-rate invoices, credit notes
• lib/core/bookkeeping/__tests__/storno-service.test.ts — Complex mock queues
• lib/core/documents/__tests__/document-service.test.ts — Storage mocking
• lib/events/__tests__/bus.test.ts — Event bus behavior
• lib/extensions/__tests__/registry.test.ts — Extension registration
• lib/import/__tests__/sie-parser.test.ts — SIE file parsing
• lib/import/bank-file/__tests__/parser.test.ts — Bank file format parsing
• lib/reconciliation/__tests__/bank-reconciliation.test.ts — Reconciliation matching algorithm
• lib/reports/__tests__/vat-declaration.test.ts — VAT declaration report
• lib/tax/__tests__/deadline-config.test.ts — Tax deadline configuration
• lib/transactions/__tests__/ingest.test.ts — Transaction ingestion and dedup

---

Database & Migrations

Location

supabase/migrations/ — currently 32 files numbered 20240101000001 through 20240101000032.

Naming Convention

YYYYMMDD00NNNN_descriptive_name.sql — next migration: 20240101000033_*.sql

Migration Rules

1. Always enable RLS on new tables: ALTER TABLE public.tablename ENABLE ROW LEVEL SECURITY;
2. Always create RLS policies using auth.uid() = user_id:

   CREATE POLICY "tablename_select" ON public.tablename FOR SELECT USING (auth.uid() = user_id);
   CREATE POLICY "tablename_insert" ON public.tablename FOR INSERT WITH CHECK (auth.uid() = user_id);
   CREATE POLICY "tablename_update" ON public.tablename FOR UPDATE USING (auth.uid() = user_id);
   

3. Always add updated_at trigger:

   CREATE TRIGGER tablename_updated_at BEFORE UPDATE ON public.tablename
     FOR EACH ROW EXECUTE FUNCTION public.update_updated_at_column();
   

4. UUID primary keys: id UUID PRIMARY KEY DEFAULT uuid_generate_v4()
5. User ownership: user_id UUID REFERENCES auth.users ON DELETE CASCADE NOT NULL
6. Never modify existing migrations — create new ones instead
7. Never modify enforcement triggers (migration 20240101000017) — these are legally required
8. Never hardcode IDs in data migrations — use subqueries or variables
9. Apply via Supabase MCP tool: mcp__plugin_supabase_supabase__apply_migration
10. Test on a branch database before applying to production (use create_branch MCP tool)

Key Enforcement Triggers (migration 017)

• enforce_journal_entry_immutability — Blocks edits/deletes on posted/reversed entries
• enforce_journal_entry_line_immutability — Blocks line modifications on committed entries
• enforce_period_lock — Blocks writes to closed/locked fiscal periods
• block_document_deletion — Prevents deletion of documents linked to committed entries
• enforce_retention_journal_entries — 7-year retention enforcement
• set_committed_at — Auto-sets timestamp on draft-to-posted transition
• calculate_retention_expiry — Auto-sets retention_expires_at = period_end + 7 years

Recent Migrations

• Migration 030 (bank_reconciliation) — Adds reconciliation_method column to transactions (CHECK constraint for method types), indexes for unmatched transaction lookup, and RPC get_unlinked_1930_lines() for finding unreconciled GL lines.
• Migration 031 (invoice_document_type) — Adds document_type column to invoices (CHECK: invoice/proforma/delivery_note, default 'invoice') and converted_from_id FK for tracking proforma-to-invoice conversions.
• Migration 032 (add_accounting_method) — Adds accounting_method column to company_settings (CHECK: accrual/cash, default 'accrual') to support kontantmetoden vs faktureringsmetoden.

---

Type System

• All shared types live in types/index.ts — this is the single source of truth
• Import via import type { TypeName } from '@/types'
• When adding new domain types, add them to types/index.ts
• Event types are the exception — they live in lib/events/types.ts (since they reference domain types)

---

API Route Patterns

Standard pattern for new API routes:

import { createClient } from '@/lib/supabase/server'
import { NextResponse } from 'next/server'
import { ensureInitialized } from '@/lib/init'

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 })
  }

  // Business logic...
  // Always filter by user_id (defense in depth alongside RLS)
  // Wrap journal entry creation in try/catch (non-blocking side effect)
  // Emit events after successful operations

  return NextResponse.json({ data: result })
}

Key conventions:

• Call ensureInitialized() at module level in any route that emits events
• Dynamic route params use { params }: { params: Promise<{ id: string }> } (Next.js 16)
• Response shapes: { data } for success, { error } for failures
• Journal entry creation is non-blocking: catch errors and continue

---

Skills Usage

• Always use the /frontend-design skill when creating new UI pages or significant components. This ensures consistent use of shadcn/ui, Tailwind CSS 4, and the existing component library.
• Use the langchain skill when building or modifying AI features (ai-chat, ai-categorization extensions).
• Use vercel:deploy for deployment tasks.

---

Git Conventions

Use conventional commits:

feat: add supplier invoice payment tracking
fix: correct VAT calculation for reduced 12% rate
refactor: extract VAT line generation into vat-entries.ts
test: add balance validation edge cases
docs: update CLAUDE.md with extension guide

• Atomic commits — one logical change per commit
• Branch from main for new work

---

Deployment

Hosted on Vercel with cron jobs defined in vercel.json:

Cron Job	Schedule
/api/extensions/enable-banking/sync/cron	Daily 05:00
/api/deadlines/status/cron	Daily 06:00
/api/invoices/reminders/cron	Daily 08:00
/api/extensions/push-notifications/cron	Daily 09:00
/api/tax-deadlines/cron	Yearly, January 2nd at 00:00
/api/documents/verify/cron	Weekly, Sunday 03:00

Required Environment Variables

NEXT_PUBLIC_SUPABASE_URL          # Supabase project URL
NEXT_PUBLIC_SUPABASE_ANON_KEY     # Supabase anonymous key
SUPABASE_SERVICE_ROLE_KEY         # Supabase service role key
ENABLE_BANKING_APP_ID             # Enable Banking app ID
ENABLE_BANKING_PRIVATE_KEY        # Enable Banking private key (base64-encoded)
ANTHROPIC_API_KEY                 # Claude API key (ai-chat)
OPENAI_API_KEY                    # OpenAI API key (embeddings)
NEXT_PUBLIC_APP_URL               # App base URL
NEXT_PUBLIC_VAPID_PUBLIC_KEY      # Web push public key
VAPID_PRIVATE_KEY                 # Web push private key

Other

We should never create a nul file