# 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, LangChain, 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

```bash
npm run dev              # Start development 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
```

---

## Architecture

```
app/
  (auth)/                 Login, auth callback
  (onboarding)/           6-step setup wizard
  (dashboard)/            Authenticated routes (invoices, customers, transactions,
                          bookkeeping, reports, suppliers, supplier-invoices,
                          receipts, deadlines, settings, help, import,
                          extensions, e/[sector]/[slug])
  (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,
                          journal entry form/list/review, document upload, correction dialog
  chat/                   ChatWidget, ChatPanel, ChatInput, ChatMessage
  customers/              CustomerForm
  dashboard/              DashboardContent, DashboardNav, FSkattWarningCard
  deadlines/              DeadlineCard, DeadlineFilters, DeadlineForm, DeadlineList,
                          TaxTodoWidget, UpcomingDeadlinesWidget
  extensions/             Extension marketplace UI (ExtensionCard, SectorCard,
                          ExtensionToggleButton, workspace components,
                          general/ subdirectory for general extension workspaces)
  import/                 Bank file import workflow components (SIE + bank file steps)
  invoices/               InvoiceReviewContent
  onboarding/             NewUserChecklist, setup step components
  reports/                Report views (BankReconciliationView, charts)
  settings/               CalendarFeedSettings
  suppliers/              SupplierForm, SupplierInvoiceReviewContent
  transactions/           Transaction list, categorization, booking, swipe review,
                          batch operations, invoice matching, VAT treatment

extensions/               Config-driven extension directory (general only)
  general/                General-purpose extensions (all businesses)
    ai-categorization/    AI-powered transaction categorization
    ai-chat/              Claude-based chat assistant (LangChain RAG)
    calendar/             Payment calendar views, deadline cards, payment summary
    email/                Email service (Resend) — registers via EmailService interface
    enable-banking/       PSD2 bank integration (opt-in)
    example-logger/       Minimal reference extension (not loaded)
    invoice-inbox/        Supplier invoice intake via email/upload with AI extraction
    push-notifications/   Web push notification system
    receipt-ocr/          Receipt image OCR processing (includes components/pages)
    user-description-match/ User description matching for transaction categorization

lib/
  api/                    Zod validation schemas and utilities for API routes
    schemas.ts            Zod schemas for all API request bodies and query params
    validate.ts           validateBody() and validateQuery() helpers
  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
    booking-templates.ts  Booking template patterns for AI suggestions
    template-embeddings.ts AI embeddings for booking template matching
    client-account-names.ts Custom account name management
    validate-period-duration.ts Fiscal period duration validation (BFL 3 kap.)
    handlers/             Booking handler functions (supplier-invoice-handler.ts)
  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 utilities, ICS feed generation
  currency/               Riksbanken exchange rates
  deadlines/              Tax deadline tracking, status engine
  email/                  Email service interface and registry
    service.ts            EmailService interface, NoopEmailService default,
                          getEmailService()/registerEmailService() registry
    resend.ts             Legacy Resend helpers (invoice/reminder templates)
  errors/                 Error message utilities (get-error-message.ts)
  events/                 Event bus (bus.ts, types.ts)
  extensions/             Extension system
    loader.ts             Loads extensions from generated FIRST_PARTY_EXTENSIONS
    registry.ts           Runtime extension registry
    types.ts              Extension, Sector, ExtensionDefinition, toggle types
    sectors.ts            Sector shells + generated extension definitions
    hooks.ts              React hooks for extension state
    context-factory.ts    Extension context builder
    toggle-check.ts       Extension enable/disable logic
    validation.ts         Extension data validation
    workspace-registry.tsx Workspace component lookup from generated map
    icon-resolver.tsx     Dynamic icon lookup for extensions
    use-account-totals.ts Hook for account balance queries
    use-extension-data.ts Hook for extension-specific data
    invoice-inbox-utils.ts Utilities for supplier invoice inbox
    use-mock-data.ts      Mock data utilities for development
    _generated/           Code-generated files (DO NOT EDIT)
      extension-list.ts   FIRST_PARTY_EXTENSIONS array
      sector-definitions.ts EXTENSION_DEFINITIONS per sector
      workspace-map.tsx   Lazy-loaded workspace component registry
      enabled-extensions.ts Set of enabled extension IDs
  hooks/                  React hooks (use-unsaved-changes.ts)
  import/                 SIE parser, SIE import orchestrator, bank file parser
    bank-file/            Bank file parser with format modules
      formats/            camt053, generic-csv, handelsbanken, nordea, seb, swedbank,
                          ica-banken, lansforsakringar, lunar, skandia
  invoices/               VAT rules, invoice matching, PDF template, reminder processor
  reconciliation/         Bank reconciliation engine (4-pass matching algorithm)
  reports/                Financial reports
    trial-balance.ts      Trial balance report
    income-statement.ts   Income statement (resultatrakning)
    balance-sheet.ts      Balance sheet (balansrakning)
    vat-declaration.ts    VAT declaration (momsdeklaration)
    sie-export.ts         SIE file export
    general-ledger.ts     General ledger (huvudbok)
    journal-register.ts   Journal register (grundbok)
    ar-ledger.ts          Accounts receivable ledger
    ar-reconciliation.ts  AR reconciliation
    supplier-ledger.ts    Supplier/AP ledger
    supplier-reconciliation.ts Supplier reconciliation
    monthly-breakdown.ts  Monthly breakdown report
    ne-bilaga/            NE tax form attachment (core report, not extension)
      ne-engine.ts        NE declaration engine
      types.ts            NE-specific types
    sru-export/           SRU file export (core report, not extension)
      sru-engine.ts       SRU generation engine
      sru-generator.ts    SRU file generator
      sru-generic-generator.ts Generic SRU generator
      types.ts            SRU-specific types
  supabase/               Client setup (client.ts = browser, server.ts = server/admin,
                          fetch-all.ts = pagination helper, middleware.ts)
  tax/                    Tax calculations, deadlines, deadline generator,
                          Swedish holidays, expense warnings
  transactions/           Transaction processing, category suggestions
  vat/                    VAT utilities
    vies-client.ts        VIES EU VAT number validation
    moms-box-mapping.ts   BAS account to momsdeklaration box mapping
  init.ts                 Extension loader (idempotent, called by API routes)
  logger.ts               Centralized logging utility
  utils.ts                Shared utility functions

types/index.ts            Canonical type definitions (single source of truth)
types/chat.ts             Chat-specific type definitions
tests/helpers.ts          Mock factories and fixture builders
supabase/migrations/      SQL migration files (45 files)
scripts/
  generate-extension-registry.ts  Code generator for extension system
  create-extension.ts     Helper for creating new extensions
  clear-user-data.sql     Utility SQL for data cleanup
dev_docs/                 Project documentation (BAS account guides, gap analysis,
                          Enable Banking docs, Bokio reference screenshots)
extensions.config.json    Extension opt-in configuration (controls which extensions load)
extensions.schema.json    JSON Schema for extensions.config.json
extensions.md             Extension system design document
.github/workflows/        CI workflows
  core-build.yml          PR build — verifies core builds/tests with zero extensions
```

### 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()`).
- **Extension system**: Extensions are opt-in via `extensions.config.json`. Code generation (`npm run setup:extensions`) produces static imports from manifests. Core builds and runs with zero extensions.
- **Email service**: Core defines `EmailService` interface in `lib/email/service.ts` with a `NoopEmailService` default. The `email` extension registers the real Resend implementation at load time. Core uses `getEmailService()` which degrades gracefully.
- **NE-bilaga and SRU export** are core reports (in `lib/reports/`), not extensions. They are always available.

---

## 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/invoices/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 System

Extensions are opt-in plugins controlled by `extensions.config.json`. The system uses a manifest-driven, code-generated architecture where core builds and runs with zero extensions.

### How It Works

1. Each extension has a `manifest.json` declaring its metadata, entry point, workspace component, dependencies, and required env vars.
2. `extensions.config.json` lists which extensions to load (by ID).
3. `npm run setup:extensions` reads the config and manifests, then generates four files in `lib/extensions/_generated/`:
   - `extension-list.ts` — `FIRST_PARTY_EXTENSIONS` array (static imports)
   - `sector-definitions.ts` — `EXTENSION_DEFINITIONS` map for marketplace UI
   - `workspace-map.tsx` — Lazy-loaded workspace component registry
   - `enabled-extensions.ts` — Set of enabled extension IDs
4. `predev` and `prebuild` hooks run this automatically.

### Enabling Extensions

Edit `extensions.config.json`:
```json
{
  "$schema": "./extensions.schema.json",
  "extensions": ["receipt-ocr", "ai-categorization", "email"]
}
```

Then run `npm run setup:extensions` (or just `npm run dev`/`npm run build`).

### Available Extensions

All extensions live in `extensions/general/` with `manifest.json` files:

| Extension | Category | Data Pattern | Env Vars Required |
|-----------|----------|--------------|-------------------|
| `receipt-ocr` | import | manual | `ANTHROPIC_API_KEY` |
| `ai-categorization` | operations | core | `OPENAI_API_KEY` |
| `ai-chat` | operations | manual | `ANTHROPIC_API_KEY`, `OPENAI_API_KEY` |
| `push-notifications` | operations | core | `NEXT_PUBLIC_VAPID_PUBLIC_KEY`, `VAPID_PRIVATE_KEY`, `VAPID_SUBJECT` |
| `invoice-inbox` | import | manual | `ANTHROPIC_API_KEY` |
| `calendar` | operations | core | — |
| `enable-banking` | import | manual | `ENABLE_BANKING_APP_ID`, `ENABLE_BANKING_PRIVATE_KEY` |
| `email` | operations | core | `RESEND_API_KEY`, `RESEND_FROM_EMAIL` |
| `user-description-match` | operations | core | — |

### Sector System

Only the `general` sector exists. Extensions are grouped under it.

Key types (from `lib/extensions/types.ts`):
- `SectorSlug` — `'general'`
- `ExtensionDefinition` — Marketplace metadata (slug, name, sector, category, icon, dataPattern, description, longDescription, readsCoreTables, hasOwnData)
- `ExtensionCategory` — `'import' | 'operations' | 'reports' | 'accounting'`
- `ExtensionDataPattern` — `'core' | 'manual' | 'both'` (how extension accesses data)
- `ExtensionToggle` — Per-user enable/disable state for extensions

### Creating a New Extension

Use the scaffolding script:

```bash
npx tsx scripts/create-extension.ts \
  --name my-extension \
  --sector general \
  --category operations \
  --description "Short description"
```

This creates:
1. `extensions/general/my-extension/manifest.json` — Full manifest template
2. `extensions/general/my-extension/index.ts` — Extension object skeleton
3. `extensions/general/my-extension/api-routes.ts` — Empty API routes array
4. Updates `extensions.schema.json` with the new ID

Then to activate:
1. Add `"my-extension"` to `extensions.config.json`
2. Run `npm run setup:extensions` to regenerate

**Manual steps** (if not using the script):
1. Create `extensions/general/<name>/manifest.json` (see Manifest Format below)
2. Create `extensions/general/<name>/index.ts` exporting an `Extension` object
3. Optionally create `extensions/general/<name>/api-routes.ts` for API endpoints
4. Add the extension ID to `extensions.schema.json` and `extensions.config.json`
5. Run `npm run setup:extensions`

**Constraints**: Extensions **cannot** use dynamic imports (Next.js bundling constraint).

### Manifest Format

Every extension declares a `manifest.json`. All fields are required unless noted:

```json
{
  "id": "my-extension",
  "sector": "general",
  "exportName": "myExtensionExtension",
  "entryPoint": "@/extensions/general/my-extension",
  "workspace": "@/components/extensions/general/MyExtensionWorkspace",
  "requiredEnvVars": ["MY_API_KEY"],
  "optionalEnvVars": [],
  "npmDependencies": ["some-sdk"],
  "definition": {
    "name": "My Extension",
    "category": "operations",
    "icon": "Wrench",
    "dataPattern": "core",
    "readsCoreTables": ["transactions"],
    "hasOwnData": false,
    "description": "Short one-line description (Swedish)",
    "longDescription": "Multi-line description (Swedish)",
    "quickAction": {
      "label": "Do Thing",
      "description": "Does the thing",
      "icon": "Wrench",
      "href": "/my-page"
    },
    "subscriptionNotice": "Optional notice shown when enabling"
  }
}
```

| Field | Type | Description |
|-------|------|-------------|
| `id` | string | Unique kebab-case ID |
| `sector` | string | Always `"general"` |
| `exportName` | string \| null | Named export from `entryPoint` (null = metadata-only, no runtime code) |
| `entryPoint` | string \| null | Import path to Extension definition (null if no runtime code) |
| `workspace` | string \| null | Import path to React workspace component (null if no UI) |
| `requiredEnvVars` | string[] | Env vars that must be set for the extension to function |
| `optionalEnvVars` | string[] | Env vars that enhance but are not required |
| `npmDependencies` | string[] | npm packages the extension needs |
| `definition.name` | string | Display name for marketplace UI |
| `definition.category` | string | `'import'` \| `'operations'` \| `'reports'` \| `'accounting'` |
| `definition.icon` | string | Lucide icon name (e.g., `"Camera"`, `"Brain"`) |
| `definition.dataPattern` | string | `'core'` (reads existing data), `'manual'` (user submits data), `'both'` |
| `definition.readsCoreTables` | string[] | Optional. Which tables it reads (for `core`/`both` pattern) |
| `definition.hasOwnData` | boolean | Optional. Whether users submit data (for `manual`/`both` pattern) |
| `definition.description` | string | One-line description (Swedish) |
| `definition.longDescription` | string | Multi-line description (Swedish) |
| `definition.quickAction` | object | Optional. Dashboard quick action button |
| `definition.subscriptionNotice` | string | Optional. Notice shown when user enables the extension |

### Extension Interface

```typescript
interface Extension {
  id: string              // Unique identifier (e.g. 'receipt-ocr')
  name: string            // Display name
  version: string         // Semver
  sector?: SectorSlug     // Always 'general'

  // Surfaces (all optional)
  routes?: RouteDefinition[]
  apiRoutes?: ApiRouteDefinition[]
  sidebarItems?: SidebarItem[]
  eventHandlers?: ExtensionEventHandler[]
  mappingRuleTypes?: MappingRuleTypeDefinition[]
  reportTypes?: ReportDefinition[]
  settingsPanel?: SettingsPanelDefinition
  taxCodes?: TaxCodeDefinition[]
  dimensionTypes?: DimensionDefinition[]
  services?: Record<string, (...args: any[]) => Promise<any>>

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

### Extension Context

Event handlers and API route handlers receive an `ExtensionContext` (`lib/extensions/context-factory.ts`):

```typescript
interface ExtensionContext {
  userId: string              // Current authenticated user
  extensionId: string         // Which extension is running
  supabase: SupabaseClient    // Pre-authenticated Supabase client
  emit(event: CoreEvent): Promise<void>  // Emit events to event bus
  settings: ExtensionSettings // Key-value store (JSONB in extension_data table)
  storage: ExtensionStorage   // Supabase Storage wrapper
  log: ExtensionLogger        // Scoped logging (prefixed "ext:extension-id")
  services: ExtensionServices // Core services (ingestTransactions, etc.)
}
```

**ExtensionSettings** — Key-value JSONB persisted in `extension_data` table:
```typescript
await ctx.settings.get<MySettings>()           // Get 'settings' key (default)
await ctx.settings.get<MyConfig>('config')     // Get specific key
await ctx.settings.set('settings', newValue)   // Set value
```

**ExtensionStorage** — Supabase Storage wrapper:
```typescript
await ctx.storage.upload('receipts', path, data, { contentType: 'image/jpeg' })
await ctx.storage.download('receipts', path)
ctx.storage.getPublicUrl('receipts', path)
```

**ExtensionLogger** — Namespaced logging:
```typescript
ctx.log.info('Processing receipt')   // logs: "ext:receipt-ocr: Processing receipt"
ctx.log.warn('Low confidence')
ctx.log.error('OCR failed', error)
```

### Extension API Routes

Extensions expose API endpoints via `apiRoutes`. These are dispatched through a single catch-all route at `app/api/extensions/ext/[...path]/route.ts`.

**URL scheme**: `/api/extensions/ext/{extensionId}/{...routePath}`

Examples:
- `POST /api/extensions/ext/receipt-ocr/upload` → matches `POST /upload`
- `GET /api/extensions/ext/receipt-ocr/abc123` → matches `GET /:id`
- `POST /api/extensions/ext/ai-categorization/suggestions` → matches `POST /suggestions`

**Defining routes** (in `api-routes.ts`):
```typescript
import type { ApiRouteDefinition, ExtensionContext } from '@/lib/extensions/types'
import { NextResponse } from 'next/server'

export const myApiRoutes: ApiRouteDefinition[] = [
  {
    method: 'GET',
    path: '/',
    handler: async (request: Request, ctx?: ExtensionContext) => {
      const userId = ctx!.userId
      const { data } = await ctx!.supabase
        .from('my_table')
        .select('*')
        .eq('user_id', userId)
      return NextResponse.json({ data })
    },
  },
  {
    method: 'GET',
    path: '/:id',
    handler: async (request: Request, ctx?: ExtensionContext) => {
      // Path params are extracted as _paramName search params
      const id = new URL(request.url).searchParams.get('_id')
      // ...
    },
  },
  {
    method: 'POST',
    path: '/:id/confirm',
    handler: async (request: Request, ctx?: ExtensionContext) => {
      const id = new URL(request.url).searchParams.get('_id')
      const body = await request.json()
      // Emit events after success:
      await ctx!.emit({ type: 'receipt.confirmed', payload: { ... } })
      return NextResponse.json({ data: result })
    },
  },
]
```

**Dispatcher behavior**:
1. Authenticates user (401 if not logged in)
2. Looks up extension in registry (404 if not found)
3. Checks extension toggle for user (403 if disabled)
4. Matches HTTP method + path pattern (supports `:param` wildcards)
5. Builds `ExtensionContext` and calls the matched handler

### Service Provider Pattern

Extensions can register capabilities that core calls without direct imports. Two patterns:

**1. Interface registration (email pattern)**:

Core defines an interface with a no-op default (`lib/email/service.ts`):
```typescript
export interface EmailService {
  sendEmail(options: SendEmailOptions): Promise<SendEmailResult>
  isConfigured(): boolean
}

let emailService: EmailService = new NoopEmailService()
export function getEmailService(): EmailService { return emailService }
export function registerEmailService(svc: EmailService): void { emailService = svc }
```

Extension registers the real implementation at load time (`extensions/general/email/index.ts`):
```typescript
import { registerEmailService } from '@/lib/email/service'
import { ResendEmailService } from './lib/resend-service'

registerEmailService(new ResendEmailService())

export const emailExtension: Extension = {
  id: 'email',
  name: 'E-post (Resend)',
  version: '1.0.0',
}
```

Core callers use `getEmailService()` — gracefully degrades if extension not loaded.

**2. Services record (ai-categorization pattern)**:

Extension exposes named functions via `services`:
```typescript
export const aiCategorizationExtension: Extension = {
  id: 'ai-categorization',
  name: 'AI Kategorisering',
  version: '1.0.0',
  services: {
    findSimilarTemplates: async (...args: unknown[]) => {
      const { findSimilarTemplates } = await import('./lib/template-embeddings')
      return findSimilarTemplates(args[0], args[1], args[2], args[3])
    },
  },
}
```

Core looks up via registry (no direct import):
```typescript
const ext = extensionRegistry.get('ai-categorization')
const results = await ext?.services?.findSimilarTemplates(tx, entityType, limit)
if (results) { /* use results */ } // Gracefully degrades if not loaded
```

### Extension Examples

**Minimal** — `extensions/general/example-logger/index.ts`:
```typescript
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
      },
    },
  ],
}
```

**Full-featured** — Receipt OCR extension (`extensions/general/receipt-ocr/index.ts`):
```typescript
export const receiptOcrExtension: Extension = {
  id: 'receipt-ocr',
  name: 'Receipt OCR',
  version: '1.0.0',
  sector: 'general',
  apiRoutes: receiptOcrApiRoutes,     // GET /, POST /upload, GET /:id, POST /:id/confirm, etc.
  eventHandlers: [
    { eventType: 'document.uploaded', handler: handleDocumentUploaded },
    { eventType: 'transaction.synced', handler: handleTransactionSynced },
  ],
  mappingRuleTypes: [
    { id: 'receipt-ocr-merchant', name: 'OCR Merchant Match', description: '...' },
  ],
  settingsPanel: {
    label: 'Receipt OCR',
    path: '/settings/extensions/receipt-ocr',
  },
  async onInstall(ctx) {
    await ctx.settings.set('settings', DEFAULT_SETTINGS)
  },
}
```

### Key Extension Files

| File | Purpose |
|------|---------|
| `extensions/general/*/manifest.json` | Metadata for each extension |
| `extensions/general/*/index.ts` | Extension object (services, handlers, etc.) |
| `extensions/general/*/api-routes.ts` | API route definitions |
| `extensions.config.json` | Which extensions are enabled |
| `extensions.schema.json` | JSON Schema for config validation |
| `scripts/generate-extension-registry.ts` | Generator script |
| `scripts/create-extension.ts` | Scaffolding helper |
| `app/api/extensions/ext/[...path]/route.ts` | Catch-all API route dispatcher |
| `lib/extensions/context-factory.ts` | Builds ExtensionContext for handlers |
| `lib/extensions/loader.ts` | Loads FIRST_PARTY_EXTENSIONS into registry |
| `lib/extensions/_generated/*` | Auto-generated files (DO NOT EDIT) |

### 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 }` |
| `credit_note.created` | `{ creditNote, userId }` |
| `transaction.synced` | `{ transactions[], userId }` |
| `transaction.categorized` | `{ transaction, account, taxCode, userId }` |
| `transaction.reconciled` | `{ transaction, journalEntryId, method, userId }` |
| `period.locked` | `{ period, userId }` |
| `period.year_closed` | `{ period, userId }` |
| `customer.created` | `{ customer, userId }` |
| `receipt.extracted` | `{ receipt, documentId, confidence, userId }` |
| `receipt.matched` | `{ receipt, transaction, confidence, autoMatched, userId }` |
| `receipt.confirmed` | `{ receipt, businessTotal, privateTotal, userId }` |
| `supplier_invoice.received` | `{ inboxItem, userId }` |
| `supplier_invoice.extracted` | `{ inboxItem, confidence, userId }` |
| `supplier_invoice.confirmed` | `{ inboxItem, supplierInvoice, 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**:
```typescript
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%
- `makeInvoice()` — Invoice with default customer, amounts, dates
- `makeCustomer()` — Customer with default name, address
- `makeSupplier()` — Supplier with default details
- `makeSupplierInvoice()` — Supplier invoice with default amounts
- `makeCompanySettings()` — Company settings with defaults
- `makeInvoiceInboxItem()` — Invoice inbox item for supplier invoice intake
- `makeExtensionToggle()` — Extension toggle state

### 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/api/__tests__/schemas.test.ts` — Zod schema validation
- `lib/api/__tests__/validate.test.ts` — Body/query validation helpers
- `lib/bookkeeping/__tests__/engine.test.ts` — Balance validation
- `lib/bookkeeping/__tests__/invoice-entries.test.ts` — Per-line VAT, mixed-rate invoices, credit notes
- `lib/bookkeeping/__tests__/mapping-engine.test.ts` — Auto-categorization rule matching
- `lib/bookkeeping/__tests__/category-mapping.test.ts` — Category-to-account mapping
- `lib/bookkeeping/__tests__/booking-templates.test.ts` — Booking template patterns
- `lib/bookkeeping/__tests__/template-embeddings.test.ts` — AI embedding matching
- `lib/bookkeeping/__tests__/validate-period-duration.test.ts` — Fiscal period duration
- `lib/bookkeeping/handlers/__tests__/supplier-invoice-handler.test.ts` — Supplier booking handler
- `lib/core/bookkeeping/__tests__/storno-service.test.ts` — Complex mock queues
- `lib/core/bookkeeping/__tests__/period-service.test.ts` — Fiscal period management
- `lib/core/bookkeeping/__tests__/year-end-service.test.ts` — Year-end closing
- `lib/core/documents/__tests__/document-service.test.ts` — Storage mocking
- `lib/core/tax/__tests__/tax-code-service.test.ts` — Tax code management
- `lib/currency/__tests__/riksbanken.test.ts` — Exchange rate fetching
- `lib/events/__tests__/bus.test.ts` — Event bus behavior
- `lib/extensions/__tests__/registry.test.ts` — Extension registration
- `lib/extensions/__tests__/loader.test.ts` — Extension loader
- `lib/extensions/__tests__/toggle-check.test.ts` — Extension toggle logic
- `lib/extensions/__tests__/validation.test.ts` — Extension data validation
- `lib/extensions/__tests__/sectors.test.ts` — Sector registry
- `lib/extensions/__tests__/context-factory.test.ts` — Extension context builder
- `lib/extensions/__tests__/invoice-inbox-utils.test.ts` — Invoice inbox utilities
- `lib/import/__tests__/sie-parser.test.ts` — SIE file parsing
- `lib/import/__tests__/sie-import.test.ts` — SIE import orchestration
- `lib/import/__tests__/account-mapper.test.ts` — SIE account mapping
- `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
- `lib/vat/__tests__/vies-client.test.ts` — VIES VAT number validation

---

## Database & Migrations

### Location

`supabase/migrations/` — currently 45 files numbered `20240101000001` through `20240101000045`.

### Naming Convention

`YYYYMMDD00NNNN_descriptive_name.sql` — next migration: `20240101000046_*.sql`

### Placeholder Migrations

Some migrations are no-op placeholders to preserve the numbering sequence:
- **012** (`tax_codes`) — Planned but never deployed. The system operates without the `tax_codes` table.
- **023** (`document_version_chain`) — Planned but never deployed. Document versioning columns/functions do not exist in production.

### 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`:
   ```sql
   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**:
   ```sql
   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 039 (`invoice_inbox`)** — Invoice inbox table with document type classification, AI extraction, supplier/transaction matching, and receipt linking.
- **Migration 040 (`booking_template_embeddings`)** — Booking templates with AI embeddings for suggestion matching.
- **Migration 041 (`user_description_matching`)** — User description matching for transaction categorization.
- **Migration 042 (`prevent_overlapping_fiscal_periods`)** — Exclusion constraint preventing overlapping fiscal periods per user.
- **Migration 043 (`enforce_fiscal_period_month_boundaries`)** — Ensures fiscal periods start/end on month boundaries.
- **Migration 044 (`full_bas_2026`)** — Full BAS 2026 account catalog, K2-excluded flag, and SRU code backfill.
- **Migration 045 (`expand_account_type_untaxed_reserves`)** — Adds `untaxed_reserves` to `chart_of_accounts.account_type` CHECK constraint for BAS 21xx accounts (obeskattade reserver).

---

## 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:

```typescript
import { createClient } from '@/lib/supabase/server'
import { NextResponse } from 'next/server'
import { ensureInitialized } from '@/lib/init'
import { validateBody } from '@/lib/api/validate'
import { CreateInvoiceSchema } 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 })
  }

  // Validate request body with Zod schema
  const result = await validateBody(request, CreateInvoiceSchema)
  if (!result.success) return result.response
  const { data } = result

  // Business logic using validated `data`...
  // 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
- **Validate all input** with `validateBody()` / `validateQuery()` from `lib/api/validate.ts` using schemas from `lib/api/schemas.ts`
- 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

---

## CI

GitHub Actions workflow (`.github/workflows/core-build.yml`) runs on pull requests:
- Resets `extensions.config.json` to empty (zero extensions)
- Runs `setup:extensions`, `build`, and `test`
- Verifies no core code (`lib/`, `app/api/`, `components/`) imports directly from `@/extensions/` (only generated files and the loader are allowed)

This ensures the core application always builds and passes tests independently of any extensions.

---

## 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
NEXT_PUBLIC_APP_URL               # App base URL
CRON_SECRET                       # Auth secret for Vercel cron jobs

# Extension-dependent (only needed when extension is enabled)
RESEND_API_KEY                    # Resend email service API key (email extension)
RESEND_FROM_EMAIL                 # Sender email (email extension)
RESEND_WEBHOOK_SECRET             # Webhook auth for Resend (email extension)
ENABLE_BANKING_APP_ID             # Enable Banking app ID (enable-banking extension)
ENABLE_BANKING_PRIVATE_KEY        # Enable Banking private key, base64 (enable-banking extension)
ENABLE_BANKING_SANDBOX            # Enable Banking sandbox mode (enable-banking extension)
ANTHROPIC_API_KEY                 # Claude API key (ai-chat, ai-categorization, receipt-ocr)
OPENAI_API_KEY                    # OpenAI API key for embeddings (ai-categorization)
NEXT_PUBLIC_VAPID_PUBLIC_KEY      # Web push public key (push-notifications extension)
VAPID_PRIVATE_KEY                 # Web push private key (push-notifications extension)
VAPID_SUBJECT                     # VAPID subject mailto: URI (push-notifications extension)
```

## Other
Never create a NUL/nul file: C:\Users\emilm\projects\erp-base\NUL