pipeline

Re-enable build/test/format pipelines, rename deploy_server to
deploy_latest, add upload_tag (tag-triggered k3s deploy) and
upload_commit (promote-triggered k3s deploy). Update CLAUDE.md.

.dockerignore

@@ -0,0 +1,8 @@
+node_modules
+*/node_modules
+*/*/node_modules
+**/dist
+apps/client
+.git
+.env
+*.md

.drone.yml

@@ -0,0 +1,171 @@
+kind: pipeline
+type: docker
+name: server_build_and_test
+
+trigger:
+  branch:
+    - main
+  event:
+    - push
+
+steps:
+  - name: build_server
+    image: node
+    commands:
+      - npm ci -w @calchat/shared
+      - npm ci -w @calchat/server
+      - npm run build -w @calchat/server
+
+  - name: jest_server
+    image: node
+    commands:
+      - npm run test -w @calchat/server
+
+---
+
+kind: pipeline
+type: docker
+name: check_for_formatting
+
+trigger:
+  branch:
+    - main
+  event:
+    - push
+
+steps:
+  - name: format_check
+    image: node
+    commands:
+      - npm ci
+      - npm run check_format
+
+---
+
+kind: pipeline
+type: docker
+name: deploy_latest
+
+trigger:
+  branch:
+    - main
+  event:
+    - push
+
+steps:
+  - name: upload_latest
+    image: plugins/docker
+    settings:
+      registry: gitea.gilmour109.de
+      repo: gitea.gilmour109.de/gilmour109/calchat-server
+      dockerfile: apps/server/docker/Dockerfile
+      tags:
+        - latest
+      username:
+        from_secret: gitea_username
+      password:
+        from_secret: gitea_password
+
+  - name: deploy_to_vps
+    image: appleboy/drone-ssh
+    settings:
+      host:
+        - 10.0.0.1
+      username: root
+      password:
+        from_secret: vps_ssh_password
+      envs:
+        - gitea_username
+        - gitea_password
+      port: 22
+      command_timeout: 2m
+      script:
+        - docker login -u $GITEA_USERNAME -p $GITEA_PASSWORD gitea.gilmour109.de
+        - docker pull gitea.gilmour109.de/gilmour109/calchat-server:latest
+        - docker compose -f /root/calchat-mongo/docker-compose.yml up -d
+
+depends_on:
+  - server_build_and_test
+  - check_for_formatting
+
+---
+
+kind: pipeline
+type: docker
+name: upload_tag
+
+trigger:
+  event:
+    - tag
+
+steps:
+  - name: upload_tag
+    image: plugins/docker
+    settings:
+      registry: gitea.gilmour109.de
+      repo: gitea.gilmour109.de/gilmour109/calchat-server
+      dockerfile: apps/server/docker/Dockerfile
+      tags:
+        - ${DRONE_TAG}
+      username:
+        from_secret: gitea_username
+      password:
+        from_secret: gitea_password
+
+  - name: deploy_to_k3s
+    image: appleboy/drone-ssh
+    settings:
+      host:
+        - 192.168.178.201
+      username: debian
+      password:
+        from_secret: k3s_ssh_password
+      envs:
+        - drone_tag
+      port: 22
+      command_timeout: 2m
+      script:
+        - export TAG=$DRONE_TAG
+        - export NAME=$(echo $DRONE_TAG | tr -d '.')
+        - envsubst < /home/debian/manifest.yml | sudo kubectl apply -f -
+
+---
+
+kind: pipeline
+type: docker
+name: upload_commit
+
+trigger:
+  event:
+    - promote
+
+steps:
+  - name: upload_commit
+    image: plugins/docker
+    settings:
+      registry: gitea.gilmour109.de
+      repo: gitea.gilmour109.de/gilmour109/calchat-server
+      dockerfile: apps/server/docker/Dockerfile
+      tags:
+        - ${DRONE_COMMIT_SHA:0:8}
+      username:
+        from_secret: gitea_username
+      password:
+        from_secret: gitea_password
+
+  - name: deploy_to_k3s
+    image: appleboy/drone-ssh
+    settings:
+      host:
+        - 192.168.178.201
+      username: debian
+      password:
+        from_secret: k3s_ssh_password
+      envs:
+        - drone_commit_sha
+      port: 22
+      command_timeout: 2m
+      script:
+        - export TAG=$(echo $DRONE_COMMIT_SHA | cut -c1-8)
+        - export NAME=$TAG
+        - envsubst < /home/debian/manifest.yml | sudo kubectl apply -f -

.gitignore

@@ -3,3 +3,5 @@ node_modules
 docs/praesi_2_context.md
 docs/*.png
 .env
+apps/server/docker/radicale/config/
+apps/server/docker/radicale/data/

CLAUDE.md

@@ -14,6 +14,7 @@ This is a fullstack TypeScript monorepo with npm workspaces.
 ```bash
 npm install          # Install all dependencies for all workspaces
 npm run format       # Format all TypeScript files with Prettier
+npm run check_format # Check formatting without modifying files (used in CI)
 ```
 
 ### Client (apps/client) - Expo React Native app
@@ -26,11 +27,17 @@ npm run lint -w @calchat/client         # Run ESLint
 npm run build:apk -w @calchat/client    # Build APK locally with EAS
 ```
 
+### Shared (packages/shared)
+```bash
+npm run build -w @calchat/shared        # Compile shared types to dist/
+```
+
 ### Server (apps/server) - Express.js backend
 ```bash
-npm run dev -w @calchat/server          # Start dev server with hot reload (tsx watch)
-npm run build -w @calchat/server        # Compile TypeScript
+npm run dev -w @calchat/server          # Build shared + start dev server with hot reload (tsx watch)
+npm run build -w @calchat/server        # Build shared + compile TypeScript
 npm run start -w @calchat/server        # Run compiled server (port 3000)
+npm run test -w @calchat/server         # Run Jest unit tests
 ```
 
 ## Technology Stack
@@ -48,9 +55,14 @@ npm run start -w @calchat/server        # Run compiled server (port 3000)
 | | MongoDB | Database |
 | | Mongoose | ODM |
 | | GPT (OpenAI) | AI/LLM for chat |
-| | X-User-Id Header | Authentication (simple, no JWT yet) |
+| | X-User-Id Header | Authentication |
 | | pino / pino-http | Structured logging |
 | | react-native-logs | Client-side logging |
+| | tsdav | CalDAV client library |
+| | ical.js | iCalendar parsing/generation |
+| Testing | Jest / ts-jest | Server unit tests |
+| Deployment | Docker | Server containerization (multi-stage build) |
+| | Drone CI | CI/CD pipelines (build, test, format check, deploy) |
 | Planned | iCalendar | Event export/import |
 
 ## Architecture
@@ -74,15 +86,15 @@ src/
 │   ├── (tabs)/                 # Tab navigation group
 │   │   ├── _layout.tsx         # Tab bar configuration (themed)
 │   │   ├── chat.tsx            # Chat screen (AI conversation)
-│   │   ├── calendar.tsx        # Calendar overview
-│   │   └── settings.tsx        # Settings screen (theme switcher, logout)
+│   │   ├── calendar.tsx        # Calendar overview (with CalendarToolbar: sync + logout)
+│   │   └── settings.tsx        # Settings screen (theme switcher, logout, CalDAV config with feedback)
 │   ├── editEvent.tsx           # Event edit screen (dual-mode: calendar/chat)
 │   ├── event/
 │   │   └── [id].tsx            # Event detail screen (dynamic route)
 │   └── note/
 │       └── [id].tsx            # Note editor for event (dynamic route)
 ├── components/
-│   ├── AuthGuard.tsx           # Auth wrapper: loads user, shows loading, redirects if unauthenticated
+│   ├── AuthGuard.tsx           # Auth wrapper: loads user, preloads app data (events + CalDAV config), CalDAV sync, shows loading, redirects if unauthenticated. Exports preloadAppData()
 │   ├── BaseBackground.tsx      # Common screen wrapper (themed)
 │   ├── BaseButton.tsx          # Reusable button component (themed, supports children)
 │   ├── Header.tsx              # Header component (themed)
@@ -96,6 +108,7 @@ src/
 │   ├── EventConfirmDialog.tsx  # AI-proposed event confirmation modal (skeleton)
 │   ├── ProposedEventCard.tsx   # Chat event proposal (uses EventCardBase + confirm/reject/edit buttons)
 │   ├── DeleteEventModal.tsx    # Delete confirmation modal (uses ModalBase)
+│   ├── CustomTextInput.tsx     # Themed text input with focus border (used in login, register, CaldavSettings, editEvent)
 │   ├── DateTimePicker.tsx      # Date and time picker components
 │   └── ScrollableDropdown.tsx  # Scrollable dropdown component
 ├── Themes.tsx                  # Theme definitions: THEMES object with defaultLight/defaultDark, Theme type
@@ -107,13 +120,15 @@ src/
 │   ├── ApiClient.ts            # HTTP client with X-User-Id header injection, request logging, handles empty responses (204)
 │   ├── AuthService.ts          # login(), register(), logout() - calls API and updates AuthStore
 │   ├── EventService.ts         # getAll(), getById(), getByDateRange(), create(), update(), delete(mode, occurrenceDate)
-│   └── ChatService.ts          # sendMessage(), confirmEvent(deleteMode, occurrenceDate), rejectEvent(), getConversations(), getConversation(), updateProposalEvent()
+│   ├── ChatService.ts          # sendMessage(), confirmEvent(deleteMode, occurrenceDate), rejectEvent(), getConversations(), getConversation(), updateProposalEvent()
+│   └── CaldavConfigService.ts  # saveConfig(), getConfig(), deleteConfig(), pull(), pushAll(), sync()
 ├── stores/                     # Zustand state management
 │   ├── index.ts                # Re-exports all stores
 │   ├── AuthStore.ts            # user, isAuthenticated, isLoading, login(), logout(), loadStoredUser()
 │   │                           # Uses expo-secure-store (native) / localStorage (web)
 │   ├── ChatStore.ts            # messages[], isWaitingForResponse, addMessage(), addMessages(), updateMessage(), clearMessages(), setWaitingForResponse(), chatMessageToMessageData()
 │   ├── EventsStore.ts          # events[], setEvents(), addEvent(), updateEvent(), deleteEvent()
+│   ├── CaldavConfigStore.ts    # config (CaldavConfig | null), setConfig() - cached CalDAV config
 │   └── ThemeStore.ts           # theme, setTheme() - reactive theme switching with Zustand
 └── hooks/
     └── useDropdownPosition.ts  # Hook for positioning dropdowns relative to trigger element
@@ -124,9 +139,12 @@ src/
 **Authentication Flow:**
 - `AuthGuard` component wraps the tab layout in `(tabs)/_layout.tsx`
 - On app start, `AuthGuard` calls `loadStoredUser()` and shows loading indicator
+- After auth, `preloadAppData()` loads events (current month) + CalDAV config into stores before dismissing spinner
 - If not authenticated, redirects to `/login`
+- `login.tsx` also calls `preloadAppData()` after successful login (spinner stays visible during preload)
 - `index.tsx` simply redirects to `/(tabs)/chat` - AuthGuard handles the rest
 - This pattern handles Expo Router's navigation state caching (avoids race conditions)
+- Preloading prevents empty screens when navigating to Calendar or Settings tabs for the first time
 
 ### Theme System
 
@@ -227,9 +245,10 @@ CardBase
 src/
 ├── app.ts                    # Entry point, DI setup, Express config
 ├── controllers/              # Request handlers + middleware (per architecture diagram)
-│   ├── AuthController.ts     # login(), register(), refresh(), logout()
-│   ├── ChatController.ts     # sendMessage(), confirmEvent(), rejectEvent(), getConversations(), getConversation(), updateProposalEvent()
-│   ├── EventController.ts    # create(), getById(), getAll(), getByDateRange(), update(), delete()
+│   ├── AuthController.ts     # login(), register()
+│   ├── ChatController.ts     # sendMessage(), confirmEvent() + CalDAV push, rejectEvent(), getConversations(), getConversation(), updateProposalEvent()
+│   ├── EventController.ts    # create(), getById(), getAll(), getByDateRange(), update(), delete() - pushes/deletes to CalDAV on mutations
+│   ├── CaldavController.ts   # saveConfig(), loadConfig(), deleteConfig(), pullEvents(), pushEvents(), pushEvent()
 │   ├── AuthMiddleware.ts     # authenticate() - X-User-Id header validation
 │   └── LoggingMiddleware.ts  # httpLogger - pino-http request logging
 ├── logging/
@@ -240,16 +259,19 @@ src/
 │   ├── index.ts              # Combines all routes under /api
 │   ├── auth.routes.ts        # /api/auth/*
 │   ├── chat.routes.ts        # /api/chat/* (protected)
-│   └── event.routes.ts       # /api/events/* (protected)
+│   ├── event.routes.ts       # /api/events/* (protected)
+│   └── caldav.routes.ts      # /api/caldav/* (protected)
 ├── services/                 # Business logic
 │   ├── interfaces/           # DB-agnostic interfaces (for dependency injection)
 │   │   ├── AIProvider.ts     # processMessage()
 │   │   ├── UserRepository.ts # findById, findByEmail, findByUserName, create + CreateUserData
 │   │   ├── EventRepository.ts
-│   │   └── ChatRepository.ts
+│   │   ├── ChatRepository.ts
+│   │   └── CaldavRepository.ts
 │   ├── AuthService.ts
 │   ├── ChatService.ts
-│   └── EventService.ts
+│   ├── EventService.ts
+│   └── CaldavService.ts      # connect(), pullEvents(), pushEvent(), pushAll(), deleteEvent(), sync logic
 ├── repositories/             # Data access (DB-specific implementations)
 │   ├── index.ts              # Re-exports from ./mongo
 │   └── mongo/                # MongoDB implementation
@@ -257,21 +279,22 @@ src/
 │       │   ├── types.ts      # Shared types (IdVirtual interface)
 │       │   ├── UserModel.ts
 │       │   ├── EventModel.ts
-│       │   └── ChatModel.ts
+│       │   ├── ChatModel.ts
+│       │   └── CaldavConfigModel.ts
 │       ├── MongoUserRepository.ts  # findById, findByEmail, findByUserName, create
 │       ├── MongoEventRepository.ts
-│       └── MongoChatRepository.ts
+│       ├── MongoChatRepository.ts
+│       └── MongoCaldavRepository.ts
 ├── ai/
 │   ├── GPTAdapter.ts         # Implements AIProvider using OpenAI GPT
 │   ├── index.ts              # Re-exports GPTAdapter
 │   └── utils/                # Shared AI utilities (provider-agnostic)
 │       ├── index.ts          # Re-exports
-│       ├── eventFormatter.ts # formatExistingEvents() for system prompt
+│       ├── eventFormatter.ts # Re-exports formatDate/Time/DateTime from shared
 │       ├── systemPrompt.ts   # buildSystemPrompt() - German calendar assistant prompt
 │       ├── toolDefinitions.ts # TOOL_DEFINITIONS - provider-agnostic tool specs
-│       └── toolExecutor.ts   # executeToolCall() - handles getDay, proposeCreate/Update/Delete, searchEvents
+│       └── toolExecutor.ts   # executeToolCall() - handles getDay, proposeCreate/Update/Delete, searchEvents, getEventsInRange
 ├── utils/
-│   ├── jwt.ts                # signToken(), verifyToken() - NOT USED YET (no JWT)
 │   ├── password.ts           # hash(), compare() using bcrypt
 │   ├── eventFormatters.ts    # getWeeksOverview(), getMonthOverview() - formatted event listings
 │   └── recurrenceExpander.ts # expandRecurringEvents() - expand recurring events into occurrences
@@ -282,8 +305,6 @@ src/
 **API Endpoints:**
 - `POST /api/auth/login` - User login
 - `POST /api/auth/register` - User registration
-- `POST /api/auth/refresh` - Refresh JWT token
-- `POST /api/auth/logout` - User logout
 - `GET /api/events` - Get all events (protected)
 - `GET /api/events/range` - Get events by date range (protected)
 - `GET /api/events/:id` - Get single event (protected)
@@ -296,18 +317,27 @@ src/
 - `GET /api/chat/conversations` - Get all conversations (protected)
 - `GET /api/chat/conversations/:id` - Get messages of a conversation with cursor-based pagination (protected)
 - `PUT /api/chat/messages/:messageId/proposal` - Update proposal event data before confirming (protected)
+- `PUT /api/caldav/config` - Save CalDAV config (protected)
+- `GET /api/caldav/config` - Load CalDAV config (protected)
+- `DELETE /api/caldav/config` - Delete CalDAV config (protected)
+- `POST /api/caldav/pull` - Pull events from CalDAV server (protected)
+- `POST /api/caldav/pushAll` - Push all unsynced events (protected)
+- `POST /api/caldav/push/:caldavUUID` - Push single event (protected)
 - `GET /health` - Health check
 - `POST /api/ai/test` - AI test endpoint (development only)
 
 ### Shared Package (packages/shared)
 
+The shared package is compiled to `dist/` (CommonJS). All imports must use `@calchat/shared` (NOT `@calchat/shared/src/...`). Server `dev` and `build` scripts automatically build shared first.
+
 ```
 src/
 ├── index.ts
 ├── models/
 │   ├── index.ts
 │   ├── User.ts           # User, CreateUserDTO, LoginDTO, AuthResponse
-│   ├── CalendarEvent.ts  # CalendarEvent, CreateEventDTO, UpdateEventDTO, ExpandedEvent
+│   ├── CalendarEvent.ts  # CalendarEvent, CreateEventDTO, UpdateEventDTO, ExpandedEvent, CaldavSyncStatus
+│   ├── CaldavConfig.ts   # CaldavConfig
 │   ├── ChatMessage.ts    # ChatMessage, Conversation, SendMessageDTO, CreateMessageDTO,
 │   │                     # GetMessagesOptions, ChatResponse, ConversationSummary,
 │   │                     # ProposedEventChange, EventAction, RespondedAction, UpdateMessageDTO
@@ -317,18 +347,22 @@ src/
     ├── index.ts
     ├── dateHelpers.ts    # getDay() - get date for specific weekday relative to today
     ├── formatters.ts     # formatDate(), formatTime(), formatDateTime(), formatDateWithWeekday() - German locale
-    └── rruleHelpers.ts   # parseRRule() - parse RRULE strings to extract freq, until, count, interval, byDay
+    └── rruleHelpers.ts   # parseRRule(), buildRRule(), formatRecurrenceRule() - RRULE parsing, building, and German formatting
 ```
 
 **Key Types:**
 - `User`: id, email, userName, passwordHash?, createdAt?, updatedAt?
-- `CalendarEvent`: id, userId, title, description?, startTime, endTime, note?, isRecurring?, recurrenceRule?, exceptionDates?
+- `CalendarEvent`: id, userId, caldavUUID?, etag?, title, description?, startTime, endTime, note?, recurrenceRule?, exceptionDates?, caldavSyncStatus?
+- `CaldavConfig`: userId, serverUrl, username, password, syncIntervalSeconds?
+- `CaldavSyncStatus`: 'synced' | 'error'
 - `ExpandedEvent`: Extends CalendarEvent with occurrenceStart, occurrenceEnd (for recurring event instances)
 - `ChatMessage`: id, conversationId, sender ('user' | 'assistant'), content, proposedChanges?
-- `ProposedEventChange`: id, action ('create' | 'update' | 'delete'), eventId?, event?, updates?, respondedAction?, deleteMode?, occurrenceDate?
+- `ProposedEventChange`: id, action ('create' | 'update' | 'delete'), eventId?, event?, updates?, respondedAction?, deleteMode?, occurrenceDate?, conflictingEvents?
   - Each proposal has unique `id` (e.g., "proposal-0") for individual confirm/reject
   - `respondedAction` tracks user response per proposal (not per message)
   - `deleteMode` ('single' | 'future' | 'all') and `occurrenceDate` for recurring event deletion
+  - `conflictingEvents` contains events that overlap with the proposed time (for conflict warnings)
+- `ConflictingEvent`: title, startTime, endTime - simplified event info for conflict display
 - `RecurringDeleteMode`: 'single' | 'future' | 'all' - delete modes for recurring events
 - `DeleteRecurringEventDTO`: mode, occurrenceDate? - DTO for recurring event deletion
 - `Conversation`: id, userId, createdAt?, updatedAt? (messages loaded separately via lazy loading)
@@ -342,6 +376,69 @@ src/
 - `Day`: "Monday" | "Tuesday" | ... | "Sunday"
 - `Month`: "January" | "February" | ... | "December"
 
+### AI Context Architecture
+
+The AI assistant fetches calendar data on-demand rather than receiving pre-loaded events. This reduces token usage significantly.
+
+**AIContext Interface:**
+```typescript
+interface AIContext {
+  userId: string;
+  conversationHistory: ChatMessage[];  // Last 20 messages for context
+  currentDate: Date;
+  // Callbacks for on-demand data fetching:
+  fetchEventsInRange: (start: Date, end: Date) => Promise<ExpandedEvent[]>;
+  searchEvents: (query: string) => Promise<CalendarEvent[]>;
+  fetchEventById: (eventId: string) => Promise<CalendarEvent | null>;
+}
+```
+
+**Available AI Tools:**
+- `getDay` - Calculate relative dates (e.g., "next Friday")
+- `getCurrentDateTime` - Get current timestamp
+- `proposeCreateEvent` - Propose new event (includes automatic conflict detection)
+- `proposeUpdateEvent` - Propose event modification
+- `proposeDeleteEvent` - Propose event deletion (supports recurring delete modes)
+- `searchEvents` - Search events by title (returns IDs for update/delete)
+- `getEventsInRange` - Load events for a date range (for "what's today?" queries)
+
+**Conflict Detection:**
+When creating events, `toolExecutor` automatically:
+1. Fetches events for the target day via `fetchEventsInRange`
+2. Checks for time overlaps using `occurrenceStart/occurrenceEnd` (important for recurring events)
+3. Returns `conflictingEvents` array in the proposal for UI display
+4. Adds ⚠️ warning to tool result so AI can inform user
+
+### CalDAV Synchronization
+
+CalDAV sync with external calendar servers (e.g., Radicale) using `tsdav` and `ical.js`.
+
+**Naming Convention:** All CalDAV-related identifiers use `Caldav` (PascalCase) / `caldav` (camelCase), NOT `CalDav`. The only exception is the protocol name "CalDAV" in comments and log messages.
+
+**Sync Triggers (client-side via `CaldavConfigService.sync()`):**
+- **Login** (`login.tsx`): After successful authentication
+- **Auto-login** (`AuthGuard.tsx`): After `loadStoredUser()` if authenticated
+- **Calendar timer** (`calendar.tsx`): Events load instantly from DB on focus (`loadEvents`), CalDAV sync runs in background (`syncAndReload`) and reloads events after. Repeats every 10s via `setInterval`
+- **Sync button** (`settings.tsx`): Manual trigger in CaldavSettings
+
+**Lazy sync (server-side in ChatService):**
+- AI data access callbacks (`fetchEventsInRange`, `searchEvents`, `fetchEventById`) trigger `syncOnce()` before the first DB query
+- Uses `CaldavService.sync()` which checks config internally (silent no-op without config)
+
+**Single-event sync (server-side in controllers):**
+- `EventController`: `pushToCaldav()` after create/update, `deleteFromCaldav()` after delete
+- `ChatController`: `pushAll()` after confirming an event proposal
+
+**Sync Flow:**
+1. `sync()` calls `pushAll` (push unsynced local events) then `pull` (fetch remote events)
+2. `pullEvents`: Compares etags to skip unchanged events, creates/updates local events, deletes locally if removed remotely
+3. `pushEvent`: Creates or updates remote event, fetches new etag after push
+
+**Architecture:**
+- `CaldavService` depends on `CaldavRepository` (config storage) and `EventService` (event CRUD)
+- `ChatService` depends on `EventService` and `CaldavService` (lazy CalDAV sync on AI data access)
+- `EventController` and `ChatController` both receive `CaldavService` for CalDAV push on mutations
+
 ### Database Abstraction
 
 The repository pattern allows swapping databases:
@@ -402,7 +499,6 @@ The decorator uses a Proxy to intercept method calls lazily, preserves sync/asyn
 **Log Summarization:**
 The `@Logged` decorator automatically summarizes large arguments to keep logs readable:
 - `conversationHistory` → `"[5 messages]"`
-- `existingEvents` → `"[3 events]"`
 - `proposedChanges` → logged in full (for debugging AI issues)
 - Long strings (>100 chars) → truncated
 - Arrays → `"[Array(n)]"`
@@ -426,7 +522,7 @@ The `@Logged` decorator automatically summarizes large arguments to keep logs re
 ### Nice-to-Have
 - iCalendar import/export
 - Multiple calendars
-- CalDAV synchronization with external services
+- ~~CalDAV synchronization with external services~~ (implemented)
 
 ## Development Environment
 
@@ -439,11 +535,24 @@ docker compose down                   # Stop services
 - MongoDB: `localhost:27017` (root/mongoose)
 - Mongo Express UI: `localhost:8083` (admin/admin)
 
+### Radicale CalDAV Server (Docker)
+```bash
+cd apps/server/docker/radicale
+docker compose up -d                  # Start Radicale CalDAV server
+```
+- Radicale: `localhost:5232`
+
+### Server Docker Image
+```bash
+# Build (requires local build context):
+docker build -f apps/server/docker/Dockerfile -t calchat-server .
+docker run -p 3001:3001 --env-file apps/server/.env calchat-server
+```
+Multi-stage COPY-based build: copies `package.json` files first for layer caching, then source code. Compiles shared + server, then copies only `dist/` and production dependencies to the runtime stage. Exposes port 3001. In CI, the `plugins/docker` Drone plugin builds and pushes the image automatically.
+
 ### Environment Variables
 Server requires `.env` file in `apps/server/`:
 ```
-JWT_SECRET=your-secret-key
-JWT_EXPIRES_IN=1h
 MONGODB_URI=mongodb://root:mongoose@localhost:27017/calchat?authSource=admin
 OPENAI_API_KEY=sk-proj-...
 USE_TEST_RESPONSES=false    # true = static test responses, false = real GPT AI
@@ -474,22 +583,28 @@ NODE_ENV=development        # development = pretty logs, production = JSON
   - `MongoChatRepository`: Full CRUD implemented (getConversationsByUser, createConversation, getMessages with cursor pagination, createMessage, updateMessage, updateProposalResponse, updateProposalEvent)
   - `ChatRepository` interface: updateMessage(), updateProposalResponse(), updateProposalEvent() for per-proposal tracking
   - `GPTAdapter`: Full implementation with OpenAI GPT (gpt-4o-mini model), function calling for calendar operations, collects multiple proposals per response
-  - `ai/utils/`: Provider-agnostic shared utilities (systemPrompt, toolDefinitions, toolExecutor, eventFormatter)
-  - `ai/utils/systemPrompt`: Includes RRULE documentation - AI knows to create separate events when times differ by day, warns AI not to put RRULE in description field
-  - `ai/utils/toolDefinitions`: proposeUpdateEvent supports `isRecurring` and `recurrenceRule` parameters for adding UNTIL or modifying recurrence
+  - `ai/utils/`: Provider-agnostic shared utilities (systemPrompt, toolDefinitions, toolExecutor)
+  - `ai/utils/systemPrompt`: AI fetches events on-demand (no pre-loaded context), includes RRULE documentation, warns AI not to put RRULE in description field, instructs AI not to show event IDs to users
+  - `ai/utils/toolDefinitions`: proposeUpdateEvent supports `recurrenceRule` parameter, getEventsInRange tool for on-demand event loading
+  - `ai/utils/toolExecutor`: Async execution, conflict detection uses `occurrenceStart/occurrenceEnd` for recurring events, returns `conflictingEvents` in proposals
+  - `MongoEventRepository`: Includes `searchByTitle()` for case-insensitive title search
   - `utils/recurrenceExpander`: Handles RRULE parsing, strips `RRULE:` prefix if present (AI may include it), filters out exceptionDates
   - `logging/`: Structured logging with pino, pino-http middleware, @Logged decorator
   - All repositories and GPTAdapter decorated with @Logged for automatic method logging
+  - `CaldavService`: Full CalDAV sync (connect, pullEvents, pushEvent, pushAll, deleteEvent, sync, getConfig, saveConfig, deleteConfig). `sync()` checks config internally and is a silent no-op without config.
+  - `CaldavController`: REST endpoints for config CRUD, pull, push
+  - `MongoCaldavRepository`: Config persistence with createOrUpdate, findByUserId, deleteByUserId
+  - `EventController`: CalDAV push on create/update, CalDAV delete on delete (via pushToCaldav/deleteFromCaldav helpers)
+  - `ChatController`: CalDAV pushAll after confirmEvent (ensures chat-created events sync)
+  - `ChatService`: Uses EventService + CaldavService (lazy sync on AI data access via syncOnce pattern)
+  - `EventService`: Extended with searchByTitle(), findByCaldavUUID()
+  - `utils/eventFormatters`: Refactored to use EventService instead of EventRepository
   - CORS configured to allow X-User-Id header
-- **Stubbed (TODO):**
-  - `AuthController`: refresh(), logout()
-  - `AuthService`: refreshToken()
-  - JWT authentication (currently using simple X-User-Id header)
 
 **Shared:**
-- Types, DTOs, constants (Day, Month with German translations), ExpandedEvent type defined and exported
-- `rruleHelpers.ts`: `parseRRule()` parses RRULE strings using rrule library, returns `ParsedRRule` with freq, until, count, interval, byDay
-- `formatters.ts`: German date/time formatters (`formatDate`, `formatTime`, `formatDateTime`, `formatDateWithWeekday`) used by both client and server
+- Types, DTOs, constants (Day, Month with German translations), ExpandedEvent type, CaldavConfig, CaldavSyncStatus defined and exported
+- `rruleHelpers.ts`: `parseRRule()` parses RRULE strings using rrule library, returns `ParsedRRule` with freq, until, count, interval, byDay. `buildRRule()` builds RRULE from RepeatType + interval. `formatRecurrenceRule()` formats RRULE into German description (e.g., "Jede Woche", "Alle 2 Monate"). Exports `REPEAT_TYPE_LABELS` and `RepeatType`.
+- `formatters.ts`: German date/time formatters (`formatDate`, `formatTime`, `formatDateTime`, `formatDateWithWeekday`, `formatDateKey`) used by both client and server
 - rrule library added as dependency for RRULE parsing
 
 **Frontend:**
@@ -497,9 +612,9 @@ NODE_ENV=development        # development = pretty logs, production = JSON
   - `AuthStore`: Manages user state with expo-secure-store (native) / localStorage (web)
   - `AuthService`: login(), register(), logout() - calls backend API
   - `ApiClient`: Automatically injects X-User-Id header for authenticated requests, handles empty responses (204)
-  - `AuthGuard`: Reusable component that wraps protected routes - loads user, shows loading, redirects if unauthenticated
-  - Login screen: Supports email OR userName login
-  - Register screen: Email validation, checks for existing email/userName
+  - `AuthGuard`: Reusable component that wraps protected routes - loads user, preloads app data (events + CalDAV config) into stores before dismissing spinner, triggers CalDAV sync, shows loading, redirects if unauthenticated. Exports `preloadAppData()` (also called by `login.tsx`)
+  - Login screen: Supports email OR userName login, uses CustomTextInput with focus border, preloads app data + triggers CalDAV sync after successful login
+  - Register screen: Email validation, checks for existing email/userName, uses CustomTextInput with focus border
   - `AuthButton`: Reusable button component with themed shadow
   - `Header`: Themed header component (logout moved to Settings)
   - `(tabs)/_layout.tsx`: Wraps tabs with AuthGuard for protected access
@@ -508,7 +623,7 @@ NODE_ENV=development        # development = pretty logs, production = JSON
   - `ThemeStore`: Zustand store with theme state and setTheme()
   - `Themes.tsx`: THEMES object with defaultLight/defaultDark variants
   - All components use `useThemeStore()` for reactive theme colors
-  - Settings screen with theme switcher (light/dark)
+  - Settings screen with theme switcher (light/dark) and CalDAV configuration (url, username, password with save/sync buttons, loads existing config on mount). Save/Sync buttons show independent feedback via `FeedbackRow` component: spinner + loading text during request, then success (green) or error (red) message that auto-clears after 3s. Both feedbacks can be visible simultaneously.
   - `BaseButton`: Reusable themed button component
 - Tab navigation (Chat, Calendar, Settings) implemented with themed UI
 - Calendar screen fully functional:
@@ -518,7 +633,7 @@ NODE_ENV=development        # development = pretty logs, production = JSON
   - Orange dot indicator for days with events
   - Tap-to-open modal overlay showing EventCards for selected day
   - Supports events from adjacent months visible in grid
-  - Uses `useFocusEffect` for automatic reload on tab focus
+  - Events load instantly from local DB on tab focus, CalDAV sync runs non-blocking in background (`syncAndReload`) with 10s interval
   - DeleteEventModal integration for recurring event deletion with three modes
   - EventOverlay hides when DeleteEventModal is open (fixes modal stacking on web)
 - Chat screen fully functional with FlashList, message sending, and event confirm/reject
@@ -530,19 +645,23 @@ NODE_ENV=development        # development = pretty logs, production = JSON
   - Tracks conversationId for message continuity across sessions
   - ChatStore with addMessages() for bulk loading, chatMessageToMessageData() helper
   - KeyboardAvoidingView for proper keyboard handling (iOS padding, Android height)
-  - Auto-scroll to end on new messages and keyboard show
+  - Auto-scroll to end on new messages and keyboard show; initial load uses `onContentSizeChange` with `animated: false` to start at bottom without visible scrolling
   - keyboardDismissMode="interactive" and keyboardShouldPersistTaps="handled"
 - `EventService`: getAll(), getById(), getByDateRange(), create(), update(), delete(mode, occurrenceDate) - fully implemented with recurring delete modes
 - `ChatService`: sendMessage(), confirmEvent(deleteMode, occurrenceDate), rejectEvent(), getConversations(), getConversation(), updateProposalEvent() - fully implemented with cursor pagination, recurring delete support, and proposal editing
+- `CaldavConfigService`: saveConfig(), getConfig(), deleteConfig(), pull(), pushAll(), sync() - CalDAV config management and sync trigger
+- `CustomTextInput`: Themed text input with focus border highlight. Props: `text`, `onValueChange`, `placeholder`, `placeholderTextColor`, `secureTextEntry`, `autoCapitalize`, `keyboardType`, `className`, `multiline`. No default padding — callers must set padding via `className` (e.g., `px-3 py-2` or `p-4`). When not focused, cursor is reset to start (`selection={{ start: 0 }}`) to avoid text appearing scrolled to the end.
 - `CardBase`: Reusable card component with header (title/subtitle), content area, and optional footer button - configurable padding, border, text size via props, ScrollView uses `nestedScrollEnabled` for Android
 - `ModalBase`: Reusable modal wrapper with backdrop (absolute-positioned behind card), uses CardBase internally - provides click-outside-to-close, Android back button support, and proper scrolling on Android
-- `EventCardBase`: Event card with date/time/recurring icons - uses CardBase for structure
+- `EventCardBase`: Event card with date/time/recurring icons - uses CardBase for structure. Accepts `recurrenceRule` string (not boolean) and displays German-formatted recurrence via `formatRecurrenceRule()`
 - `EventCard`: Uses EventCardBase + edit/delete buttons (TouchableOpacity with delayPressIn for scroll-friendly touch handling)
-- `ProposedEventCard`: Uses EventCardBase + confirm/reject/edit buttons for chat proposals, displays green highlighted text for new changes ("Neue Ausnahme: [date]" for single delete, "Neues Ende: [date]" for UNTIL updates). Edit button allows modifying proposals before confirming.
+- `ProposedEventCard`: Uses EventCardBase + confirm/reject/edit buttons for chat proposals, displays green highlighted text for new changes ("Neue Ausnahme: [date]" for single delete, "Neues Ende: [date]" for UNTIL updates), shows yellow conflict warnings when proposed time overlaps with existing events. Edit button allows modifying proposals before confirming.
 - `DeleteEventModal`: Delete confirmation modal using ModalBase - shows three options for recurring events (single/future/all), simple confirm for non-recurring
+- `CalendarToolbar` (in calendar.tsx): Toolbar between header and weekdays with Sync button (CalDAV sync with spinner/green checkmark/red X feedback, disabled without config) and Logout button
 - `EventOverlay` (in calendar.tsx): Day events overlay using ModalBase - shows EventCards for selected day
 - `Themes.tsx`: Theme definitions with THEMES object (defaultLight, defaultDark) including all color tokens (textPrimary, borderPrimary, eventIndicator, secondaryBg, shadowColor, etc.)
-- `EventsStore`: Zustand store with setEvents(), addEvent(), updateEvent(), deleteEvent() - stores ExpandedEvent[]
+- `EventsStore`: Zustand store with setEvents(), addEvent(), updateEvent(), deleteEvent() - stores ExpandedEvent[], preloaded by AuthGuard
+- `CaldavConfigStore`: Zustand store with config (CaldavConfig | null), setConfig() - cached CalDAV config, preloaded by AuthGuard, used by Settings to avoid API call on mount
 - `ChatStore`: Zustand store with addMessage(), addMessages(), updateMessage(), clearMessages(), isWaitingForResponse/setWaitingForResponse() for typing indicator - loads from server on mount and persists across tab switches
 - `ThemeStore`: Zustand store with theme/setTheme() for reactive theme switching across all components
 - `ChatBubble`: Reusable chat bubble component with Tailwind styling, used by ChatMessage and TypingIndicator
@@ -577,6 +696,29 @@ This uses the `preview` profile from `eas.json` which builds an APK with:
 - Package name: `com.gilmour109.calchat`
 - EAS Project ID: `b722dde6-7d89-48ff-9095-e007e7c7da87`
 
+## CI/CD (Drone)
+
+The project uses Drone CI (`.drone.yml`) with five pipelines:
+
+**On push to main:**
+1. **`server_build_and_test`**: Builds the server (`npm ci` + `npm run build`) and runs Jest tests (`npm run test`)
+2. **`check_for_formatting`**: Checks Prettier formatting across all workspaces (`npm run check_format`)
+3. **`deploy_latest`**: Builds Docker image, pushes to Gitea Container Registry (`gitea.gilmour109.de/gilmour109/calchat-server:latest`), then SSHs into VPS (`10.0.0.1`) to pull and restart via `docker compose`. Depends on both pipelines above passing first.
+
+**On tag:**
+4. **`upload_tag`**: Builds Docker image tagged with the git tag (`${DRONE_TAG}`), pushes to registry, then deploys to k3s cluster (`192.168.178.201`) via SSH using `envsubst` with a Kubernetes manifest template.
+
+**On promote:**
+5. **`upload_commit`**: Builds Docker image tagged with short commit SHA (first 8 chars), pushes to registry, then deploys to k3s cluster (`192.168.178.201`) via SSH using `envsubst` with a Kubernetes manifest template.
+
+## Testing
+
+Server uses Jest with ts-jest for unit testing. Config in `apps/server/jest.config.js` ignores `/node_modules/` and `/dist/`.
+
+**Existing tests:**
+- `src/utils/password.test.ts` - Tests for bcrypt hash() and compare()
+- `src/utils/recurrenceExpander.test.ts` - Tests for expandRecurringEvents() (non-recurring, weekly/daily/UNTIL recurrence, EXDATE filtering, RRULE: prefix stripping, invalid RRULE fallback, multi-day events, sorting)
+
 ## Documentation
 
 Detailed architecture diagrams are in `docs/`:

README.md

@@ -1,50 +1,141 @@
-# Welcome to your Expo app 👋
+# CalChat
 
-This is an [Expo](https://expo.dev) project created with [`create-expo-app`](https://www.npmjs.com/package/create-expo-app).
+Kalender-App mit KI-Chatbot. Termine lassen sich per Chat in natuerlicher Sprache erstellen, bearbeiten und loeschen.
 
-## Get started
+## Tech Stack
 
-1. Install dependencies
+| Bereich | Technologie |
+|---------|-------------|
+| Frontend | React Native, Expo, Expo-Router, NativeWind, Zustand |
+| Backend | Express.js, MongoDB, Mongoose, OpenAI GPT |
+| Shared | TypeScript Monorepo mit npm Workspaces |
+| Optional | CalDAV-Sync (z.B. Radicale) |
 
-   ```bash
-   npm install
-   ```
+## Voraussetzungen
 
-2. Start the app
+- Node.js (>= 20)
+- npm
+- Docker & Docker Compose (fuer MongoDB)
+- OpenAI API Key (fuer KI-Chat)
+- Android SDK + Java (nur fuer APK-Build)
 
-   ```bash
-   npx expo start
-   ```
+## Projekt aufsetzen
 
-In the output, you'll find options to open the app in a
-
-- [development build](https://docs.expo.dev/develop/development-builds/introduction/)
-- [Android emulator](https://docs.expo.dev/workflow/android-studio-emulator/)
-- [iOS simulator](https://docs.expo.dev/workflow/ios-simulator/)
-- [Expo Go](https://expo.dev/go), a limited sandbox for trying out app development with Expo
-
-You can start developing by editing the files inside the **app** directory. This project uses [file-based routing](https://docs.expo.dev/router/introduction).
-
-## Get a fresh project
-
-When you're ready, run:
+### 1. Repository klonen
 
 ```bash
-npm run reset-project
+git clone <repo-url>
+cd calchat
 ```
 
-This command will move the starter code to the **app-example** directory and create a blank **app** directory where you can start developing.
+### 2. Dependencies installieren
 
-## Learn more
+```bash
+npm install
+```
 
-To learn more about developing your project with Expo, look at the following resources:
+Installiert alle Dependencies fuer Client, Server und Shared.
 
-- [Expo documentation](https://docs.expo.dev/): Learn fundamentals, or go into advanced topics with our [guides](https://docs.expo.dev/guides).
-- [Learn Expo tutorial](https://docs.expo.dev/tutorial/introduction/): Follow a step-by-step tutorial where you'll create a project that runs on Android, iOS, and the web.
+### 3. MongoDB starten
 
-## Join the community
+```bash
+cd apps/server/docker/mongo
+docker compose up -d
+```
 
-Join our community of developers creating universal apps.
+- MongoDB: `localhost:27017` (root/mongoose)
+- Mongo Express UI: `localhost:8083` (admin/admin)
 
-- [Expo on GitHub](https://github.com/expo/expo): View our open source platform and contribute.
-- [Discord community](https://chat.expo.dev): Chat with Expo users and ask questions.
+### 4. Server konfigurieren
+
+```bash
+cp apps/server/.env.example apps/server/.env
+```
+
+`apps/server/.env` bearbeiten:
+
+```env
+MONGODB_URI=mongodb://root:mongoose@localhost:27017/calchat?authSource=admin
+OPENAI_API_KEY=sk-proj-...    # Eigenen Key eintragen
+USE_TEST_RESPONSES=false       # true = statische Testantworten ohne GPT
+LOG_LEVEL=debug
+NODE_ENV=development
+PORT=3000
+```
+
+### 5. Client konfigurieren
+
+```bash
+cp apps/client/.env.example apps/client/.env
+```
+
+`apps/client/.env` bearbeiten:
+
+```env
+# Fuer Emulator/Web:
+EXPO_PUBLIC_API_URL=http://localhost:3000/api
+
+# Fuer physisches Geraet im gleichen Netzwerk:
+EXPO_PUBLIC_API_URL=http://<DEINE-LOKALE-IP>:3000/api
+```
+
+### 6. Server starten
+
+```bash
+npm run dev -w @calchat/server
+```
+
+Startet den Server auf Port 3000 (mit `tsx watch` - startet bei Dateiänderungen automatisch neu (oder sollte es zumindest)).
+
+### 7. Client starten
+
+```bash
+npm run start -w @calchat/client
+```
+
+Dann im Expo-Menue die gewuenschte Plattform waehlen:
+- `a` - Android Emulator
+- `i` - iOS Simulator
+- `w` - Web Browser
+
+Oder direkt:
+
+```bash
+npm run android -w @calchat/client
+npm run ios -w @calchat/client
+npm run web -w @calchat/client
+```
+
+## CalDAV (optional)
+
+Fuer CalDAV-Synchronisation kann ein Radicale-Server gestartet werden:
+
+```bash
+cd apps/server/docker/radicale
+docker compose up -d
+```
+
+Radicale ist dann unter `localhost:5232` erreichbar. Die CalDAV-Verbindung wird in der App unter Einstellungen konfiguriert.
+
+## Weitere Befehle
+
+```bash
+npm run format                          # Prettier auf alle TS/TSX-Dateien
+npm run lint -w @calchat/client         # ESLint (Client)
+npm run build -w @calchat/server        # TypeScript kompilieren (Server)
+npm run build:apk -w @calchat/client    # APK lokal bauen (EAS)
+```
+
+## Projektstruktur
+
+```
+calchat/
+├── apps/
+│   ├── client/          # Expo React Native App
+│   └── server/          # Express.js Backend
+│       └── docker/
+│           ├── mongo/   # MongoDB + Mongo Express
+│           └── radicale/ # CalDAV Server
+└── packages/
+    └── shared/          # Geteilte Types und Utilities
+```

apps/client/.env.example

@@ -0,0 +1,8 @@
+# Base URL of the CalChat API server
+# Must include the /api path suffix
+# Use your local network IP for mobile device testing, or localhost for emulator/web
+# Examples:
+#   http://192.168.178.22:3001/api   (local network, for physical device)
+#   http://localhost:3001/api         (emulator or web)
+#   https://calchat.example.com/api   (production)
+EXPO_PUBLIC_API_URL=http://localhost:3001/api

apps/client/eas.json

@@ -15,7 +15,8 @@
         "withoutCredentials": true
       },
       "env": {
-        "ORG_GRADLE_PROJECT_reactNativeArchitectures": "arm64-v8a"
+        "ORG_GRADLE_PROJECT_reactNativeArchitectures": "arm64-v8a",
+        "EXPO_PUBLIC_API_URL": "https://calchat.gilmour109.de/api"
       }
     },
     "production": {

apps/client/src/app/(tabs)/calendar.tsx

@@ -1,4 +1,4 @@
-import { Pressable, Text, View } from "react-native";
+import { ActivityIndicator, Pressable, Text, View } from "react-native";
 import {
   DAYS,
   MONTHS,
@@ -11,19 +11,16 @@ import { EventCard } from "../../components/EventCard";
 import { DeleteEventModal } from "../../components/DeleteEventModal";
 import { ModalBase } from "../../components/ModalBase";
 import { ScrollableDropdown } from "../../components/ScrollableDropdown";
-import React, {
-  useCallback,
-  useEffect,
-  useMemo,
-  useState,
-} from "react";
+import React, { useCallback, useEffect, useMemo, useState } from "react";
 import { router, useFocusEffect } from "expo-router";
 import { Ionicons } from "@expo/vector-icons";
 import { useThemeStore } from "../../stores/ThemeStore";
 import BaseBackground from "../../components/BaseBackground";
-import { EventService } from "../../services";
+import { AuthService, EventService } from "../../services";
 import { useEventsStore } from "../../stores";
 import { useDropdownPosition } from "../../hooks/useDropdownPosition";
+import { CaldavConfigService } from "../../services/CaldavConfigService";
+import { useCaldavConfigStore } from "../../stores/CaldavConfigStore";
 
 // MonthSelector types and helpers
 type MonthItem = {
@@ -84,7 +81,7 @@ const Calendar = () => {
 
   const { events, setEvents, deleteEvent } = useEventsStore();
 
-  // Function to load events for current view
+  // Load events from local DB (fast, no network sync)
   const loadEvents = useCallback(async () => {
     try {
       // Calculate first visible day (up to 6 days before month start)
@@ -112,17 +109,20 @@ const Calendar = () => {
     }
   }, [monthIndex, currentYear, setEvents]);
 
-  // Load events when tab gains focus or month/year changes
-  // NOTE: Wrapper needed because loadEvents is async (returns Promise)
-  // and useFocusEffect expects a sync function (optionally returning cleanup)
-  // Also re-open overlay if selectedDate exists (for back navigation from editEvent)
+  // Load events from DB on focus
   useFocusEffect(
     useCallback(() => {
       loadEvents();
+    }, [loadEvents]),
+  );
+
+  // Re-open overlay after back navigation from editEvent
+  useFocusEffect(
+    useCallback(() => {
       if (selectedDate) {
         setOverlayVisible(true);
       }
-    }, [loadEvents, selectedDate]),
+    }, [selectedDate]),
   );
 
   // Group events by date (YYYY-MM-DD format)
@@ -203,7 +203,7 @@ const Calendar = () => {
     const occurrenceDate = getDateKey(new Date(event.occurrenceStart));
 
     try {
-      if (event.isRecurring) {
+      if (event.recurrenceRule) {
         // Recurring event: use mode and occurrenceDate
         await EventService.delete(event.id, mode, occurrenceDate);
         // Reload events to reflect changes
@@ -241,6 +241,7 @@ const Calendar = () => {
         setMonthIndex={setMonthIndex}
         setYear={setCurrentYear}
       />
+      <CalendarToolbar loadEvents={loadEvents} />
       <WeekDaysLine />
       <CalendarGrid
         month={MONTHS[monthIndex]}
@@ -260,7 +261,7 @@ const Calendar = () => {
       <DeleteEventModal
         visible={deleteModalVisible}
         eventTitle={eventToDelete?.title || ""}
-        isRecurring={eventToDelete?.isRecurring || false}
+        isRecurring={!!eventToDelete?.recurrenceRule}
         onConfirm={handleDeleteConfirm}
         onCancel={handleDeleteCancel}
       />
@@ -545,6 +546,131 @@ const ChangeMonthButton = (props: ChangeMonthButtonProps) => {
   );
 };
 
+type CalendarToolbarProps = {
+  loadEvents: () => Promise<void>;
+};
+
+const CalendarToolbar = ({ loadEvents }: CalendarToolbarProps) => {
+  const { theme } = useThemeStore();
+  const { config } = useCaldavConfigStore();
+  const [isSyncing, setIsSyncing] = useState(false);
+  const [syncResult, setSyncResult] = useState<"success" | "error" | null>(
+    null,
+  );
+
+  const handleSync = async () => {
+    if (!config || isSyncing) return;
+    setSyncResult(null);
+    setIsSyncing(true);
+    try {
+      await CaldavConfigService.sync();
+      await loadEvents();
+      setSyncResult("success");
+    } catch (error) {
+      console.error("CalDAV sync failed:", error);
+      setSyncResult("error");
+    } finally {
+      setIsSyncing(false);
+    }
+  };
+
+  useEffect(() => {
+    if (!syncResult) return;
+    const timer = setTimeout(() => setSyncResult(null), 3000);
+    return () => clearTimeout(timer);
+  }, [syncResult]);
+
+  const handleLogout = async () => {
+    await AuthService.logout();
+    router.replace("/login");
+  };
+
+  const syncIcon = () => {
+    if (isSyncing) {
+      return <ActivityIndicator size="small" color={theme.primeFg} />;
+    }
+    if (syncResult === "success") {
+      return (
+        <Ionicons
+          name="checkmark-circle"
+          size={20}
+          color={theme.confirmButton}
+        />
+      );
+    }
+    if (syncResult === "error") {
+      return (
+        <Ionicons name="close-circle" size={20} color={theme.rejectButton} />
+      );
+    }
+    return (
+      <Ionicons
+        name="sync-outline"
+        size={20}
+        color={config ? theme.primeFg : theme.textMuted}
+      />
+    );
+  };
+
+  const buttonStyle = {
+    backgroundColor: theme.chatBot,
+    borderColor: theme.borderPrimary,
+    borderWidth: 1,
+    shadowColor: theme.shadowColor,
+    shadowOffset: { width: 0, height: 2 },
+    shadowOpacity: 0.25,
+    shadowRadius: 4,
+    elevation: 4,
+  };
+
+  const className = "flex flex-row items-center gap-2 px-3 py-1 rounded-lg";
+
+  return (
+    <View
+      className="flex flex-row items-center justify-around py-2"
+      style={{
+        backgroundColor: theme.primeBg,
+        borderBottomWidth: 0,
+        borderBottomColor: theme.borderPrimary,
+      }}
+    >
+      <Pressable
+        onPress={handleSync}
+        disabled={!config || isSyncing}
+        className={className}
+        style={{
+          ...buttonStyle,
+          ...(config
+            ? {}
+            : {
+                backgroundColor: theme.disabledButton,
+                borderColor: theme.disabledButton,
+              }),
+        }}
+      >
+        {syncIcon()}
+        <Text
+          style={{ color: config ? theme.textPrimary : theme.textMuted }}
+          className="font-medium"
+        >
+          Sync
+        </Text>
+      </Pressable>
+
+      <Pressable
+        onPress={handleLogout}
+        className={className}
+        style={buttonStyle}
+      >
+        <Ionicons name="log-out-outline" size={20} color={theme.primeFg} />
+        <Text style={{ color: theme.textPrimary }} className="font-medium">
+          Logout
+        </Text>
+      </Pressable>
+    </View>
+  );
+};
+
 const WeekDaysLine = () => {
   const { theme } = useThemeStore();
   return (

apps/client/src/app/(tabs)/chat.tsx

@@ -64,11 +64,11 @@ const Chat = () => {
     string | undefined
   >();
   const [hasLoadedMessages, setHasLoadedMessages] = useState(false);
+  const needsInitialScroll = useRef(false);
 
   useEffect(() => {
-    const keyboardDidShow = Keyboard.addListener(
-      "keyboardDidShow",
-      scrollToEnd,
+    const keyboardDidShow = Keyboard.addListener("keyboardDidShow", () =>
+      scrollToEnd(),
     );
     return () => keyboardDidShow.remove();
   }, []);
@@ -90,7 +90,7 @@ const Chat = () => {
               await ChatService.getConversation(conversationId);
             const clientMessages = serverMessages.map(chatMessageToMessageData);
             addMessages(clientMessages);
-            scrollToEnd();
+            needsInitialScroll.current = true;
           }
         } catch (error) {
           console.error("Failed to load messages:", error);
@@ -102,9 +102,9 @@ const Chat = () => {
     }, [isAuthLoading, isAuthenticated, hasLoadedMessages]),
   );
 
-  const scrollToEnd = () => {
+  const scrollToEnd = (animated = true) => {
     setTimeout(() => {
-      listRef.current?.scrollToEnd({ animated: true });
+      listRef.current?.scrollToEnd({ animated });
     }, 100);
   };
 
@@ -175,7 +175,11 @@ const Chat = () => {
       params: {
         mode: "chat",
         eventData: JSON.stringify(proposal.event),
-        proposalContext: JSON.stringify({ messageId, proposalId, conversationId }),
+        proposalContext: JSON.stringify({
+          messageId,
+          proposalId,
+          conversationId,
+        }),
       },
     });
   };
@@ -273,6 +277,12 @@ const Chat = () => {
           keyExtractor={(item) => item.id}
           keyboardDismissMode="interactive"
           keyboardShouldPersistTaps="handled"
+          onContentSizeChange={() => {
+            if (needsInitialScroll.current) {
+              needsInitialScroll.current = false;
+              listRef.current?.scrollToEnd({ animated: false });
+            }
+          }}
           ListFooterComponent={
             isWaitingForResponse ? <TypingIndicator /> : null
           }

apps/client/src/app/(tabs)/settings.tsx

@@ -1,18 +1,212 @@
-import { Text, View } from "react-native";
+import { ActivityIndicator, Text, View } from "react-native";
 import BaseBackground from "../../components/BaseBackground";
-import BaseButton from "../../components/BaseButton";
+import BaseButton, { BaseButtonProps } from "../../components/BaseButton";
 import { useThemeStore } from "../../stores/ThemeStore";
 import { AuthService } from "../../services/AuthService";
 import { router } from "expo-router";
 import { Ionicons } from "@expo/vector-icons";
 import { SimpleHeader } from "../../components/Header";
 import { THEMES } from "../../Themes";
+import CustomTextInput from "../../components/CustomTextInput";
+import { useCallback, useRef, useState } from "react";
+import { CaldavConfigService } from "../../services/CaldavConfigService";
+import { useCaldavConfigStore } from "../../stores";
 
 const handleLogout = async () => {
   await AuthService.logout();
   router.replace("/login");
 };
 
+const SettingsButton = (props: BaseButtonProps) => {
+  return (
+    <BaseButton
+      onPress={props.onPress}
+      solid={props.solid}
+      className={"w-11/12"}
+    >
+      {props.children}
+    </BaseButton>
+  );
+};
+
+type CaldavTextInputProps = {
+  title: string;
+  value: string;
+  onValueChange: (text: string) => void;
+  secureTextEntry?: boolean;
+};
+
+const CaldavTextInput = ({
+  title,
+  value,
+  onValueChange,
+  secureTextEntry,
+}: CaldavTextInputProps) => {
+  const { theme } = useThemeStore();
+  return (
+    <View className="flex flex-row items-center py-1">
+      <Text className="ml-4 w-24" style={{ color: theme.textPrimary }}>
+        {title}:
+      </Text>
+      <CustomTextInput
+        className="flex-1 mr-4 px-3 py-2"
+        text={value}
+        onValueChange={onValueChange}
+        secureTextEntry={secureTextEntry}
+      />
+    </View>
+  );
+};
+
+type Feedback = { text: string; isError: boolean; loading: boolean };
+
+const FeedbackRow = ({ feedback }: { feedback: Feedback | null }) => {
+  const { theme } = useThemeStore();
+  if (!feedback) return null;
+  return (
+    <View className="flex flex-row items-center justify-center mt-2 mx-4 gap-2">
+      {feedback.loading && (
+        <ActivityIndicator size="small" color={theme.textMuted} />
+      )}
+      <Text
+        style={{
+          color: feedback.loading
+            ? theme.textMuted
+            : feedback.isError
+              ? theme.rejectButton
+              : theme.confirmButton,
+        }}
+      >
+        {feedback.text}
+      </Text>
+    </View>
+  );
+};
+
+const CaldavSettings = () => {
+  const { theme } = useThemeStore();
+  const { config, setConfig } = useCaldavConfigStore();
+
+  const [serverUrl, setServerUrl] = useState(config?.serverUrl ?? "");
+  const [username, setUsername] = useState(config?.username ?? "");
+  const [password, setPassword] = useState(config?.password ?? "");
+  const [saveFeedback, setSaveFeedback] = useState<Feedback | null>(null);
+  const [syncFeedback, setSyncFeedback] = useState<Feedback | null>(null);
+  const saveTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const syncTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
+
+  const showFeedback = useCallback(
+    (
+      setter: typeof setSaveFeedback,
+      timer: typeof saveTimer,
+      text: string,
+      isError: boolean,
+      loading = false,
+    ) => {
+      if (timer.current) clearTimeout(timer.current);
+      setter({ text, isError, loading });
+      if (!loading) {
+        timer.current = setTimeout(() => setter(null), 3000);
+      }
+    },
+    [],
+  );
+
+  const saveConfig = async () => {
+    showFeedback(
+      setSaveFeedback,
+      saveTimer,
+      "Speichere Konfiguration...",
+      false,
+      true,
+    );
+    try {
+      const saved = await CaldavConfigService.saveConfig(
+        serverUrl,
+        username,
+        password,
+      );
+      setConfig(saved);
+      showFeedback(
+        setSaveFeedback,
+        saveTimer,
+        "Konfiguration wurde gespeichert",
+        false,
+      );
+    } catch {
+      showFeedback(
+        setSaveFeedback,
+        saveTimer,
+        "Fehler beim Speichern der Konfiguration",
+        true,
+      );
+    }
+  };
+
+  const sync = async () => {
+    showFeedback(setSyncFeedback, syncTimer, "Synchronisiere...", false, true);
+    try {
+      await CaldavConfigService.sync();
+      showFeedback(
+        setSyncFeedback,
+        syncTimer,
+        "Synchronisierung erfolgreich",
+        false,
+      );
+    } catch {
+      showFeedback(
+        setSyncFeedback,
+        syncTimer,
+        "Fehler beim Synchronisieren",
+        true,
+      );
+    }
+  };
+
+  return (
+    <>
+      <View>
+        <Text
+          className="text-center text-2xl"
+          style={{ color: theme.textPrimary }}
+        >
+          Caldav Config
+        </Text>
+      </View>
+      <View>
+        <View className="pb-1">
+          <CaldavTextInput
+            title="url"
+            value={serverUrl}
+            onValueChange={setServerUrl}
+          />
+          <CaldavTextInput
+            title="username"
+            value={username}
+            onValueChange={setUsername}
+          />
+          <CaldavTextInput
+            title="password"
+            value={password}
+            onValueChange={setPassword}
+            secureTextEntry
+          />
+        </View>
+        <View className="flex flex-row">
+          <BaseButton className="mx-4 w-1/5" solid={true} onPress={saveConfig}>
+            Save
+          </BaseButton>
+          <BaseButton className="w-1/5" solid={true} onPress={sync}>
+            Sync
+          </BaseButton>
+        </View>
+        <FeedbackRow feedback={saveFeedback} />
+        <FeedbackRow feedback={syncFeedback} />
+      </View>
+    </>
+  );
+};
+
 const Settings = () => {
   const { theme, setTheme } = useThemeStore();
 
@@ -20,10 +214,10 @@ const Settings = () => {
     <BaseBackground>
       <SimpleHeader text="Settings" />
       <View className="flex items-center mt-4">
-        <BaseButton onPress={handleLogout} solid={true}>
+        <SettingsButton onPress={handleLogout} solid={true}>
           <Ionicons name="log-out-outline" size={24} color={theme.primeFg} />{" "}
           Logout
-        </BaseButton>
+        </SettingsButton>
         <View>
           <Text
             className="text-center text-2xl"
@@ -32,23 +226,24 @@ const Settings = () => {
             Select Theme
           </Text>
         </View>
-        <BaseButton
+        <SettingsButton
           solid={theme == THEMES.defaultLight}
           onPress={() => {
             setTheme("defaultLight");
           }}
         >
           Default Light
-        </BaseButton>
-        <BaseButton
+        </SettingsButton>
+        <SettingsButton
           solid={theme == THEMES.defaultDark}
           onPress={() => {
             setTheme("defaultDark");
           }}
         >
           Default Dark
-        </BaseButton>
+        </SettingsButton>
       </View>
+      <CaldavSettings />
     </BaseBackground>
   );
 };

apps/client/src/app/editEvent.tsx

@@ -19,43 +19,34 @@ import { Ionicons } from "@expo/vector-icons";
 import { ScrollableDropdown } from "../components/ScrollableDropdown";
 import { useDropdownPosition } from "../hooks/useDropdownPosition";
 import { EventService, ChatService } from "../services";
-import { buildRRule, CreateEventDTO } from "@calchat/shared";
+import {
+  buildRRule,
+  CreateEventDTO,
+  REPEAT_TYPE_LABELS,
+  RepeatType,
+} from "@calchat/shared";
 import { useChatStore } from "../stores";
+import CustomTextInput, {
+  CustomTextInputProps,
+} from "../components/CustomTextInput";
 
-// Direct store access for getting current state in callbacks
-const getChatStoreState = () => useChatStore.getState();
-
-type EditEventTextFieldProps = {
+type EditEventTextFieldProps = CustomTextInputProps & {
   titel: string;
-  text?: string;
-  focused?: boolean;
-  className?: string;
-  multiline?: boolean;
-  onValueChange?: (text: string) => void;
 };
 
 const EditEventTextField = (props: EditEventTextFieldProps) => {
   const { theme } = useThemeStore();
-  const [focused, setFocused] = useState(props.focused ?? false);
 
   return (
     <View className={props.className}>
       <Text className="text-xl" style={{ color: theme.textPrimary }}>
         {props.titel}
       </Text>
-      <TextInput
-        onChangeText={props.onValueChange}
-        value={props.text}
+      <CustomTextInput
+        className="flex-1 px-3 py-2"
+        text={props.text}
         multiline={props.multiline}
-        className="flex-1 border border-solid rounded-2xl px-3 py-2 w-full h-11/12"
-        style={{
-          backgroundColor: theme.messageBorderBg,
-          color: theme.textPrimary,
-          textAlignVertical: "top",
-          borderColor: focused ? theme.chatBot : theme.borderPrimary,
-        }}
-        onFocus={() => setFocused(true)}
-        onBlur={() => setFocused(false)}
+        onValueChange={props.onValueChange}
       />
     </View>
   );
@@ -100,15 +91,6 @@ const PickerRow = ({
   );
 };
 
-type RepeatType = "Tag" | "Woche" | "Monat" | "Jahr";
-
-const REPEAT_TYPE_LABELS: Record<RepeatType, string> = {
-  Tag: "Tage",
-  Woche: "Wochen",
-  Monat: "Monate",
-  Jahr: "Jahre",
-};
-
 type RepeatPressableProps = {
   focused: boolean;
   repeatType: RepeatType;
@@ -443,31 +425,25 @@ const EditEventScreen = () => {
         : undefined,
     };
 
-    // Chat mode: update proposal locally and on server
+    // Chat mode: update proposal on server and sync response to local store
     if (mode === "chat" && proposalContext) {
       try {
         const context = JSON.parse(proposalContext) as ProposalContext;
 
-        // Update locally in ChatStore
-        const currentMessages = getChatStoreState().messages;
-        const message = currentMessages.find((m) => m.id === context.messageId);
-
-        if (message?.proposedChanges) {
-          const updatedProposals = message.proposedChanges.map((p) =>
-            p.id === context.proposalId ? { ...p, event: eventObject } : p,
-          );
-          updateMessage(context.messageId, {
-            proposedChanges: updatedProposals,
-          });
-        }
-
-        // Persist to server
-        await ChatService.updateProposalEvent(
+        // Persist to server - returns updated message with recalculated conflictingEvents
+        const updatedMessage = await ChatService.updateProposalEvent(
           context.messageId,
           context.proposalId,
           eventObject,
         );
 
+        // Update local ChatStore with server response (includes updated conflicts)
+        if (updatedMessage?.proposedChanges) {
+          updateMessage(context.messageId, {
+            proposedChanges: updatedMessage.proposedChanges,
+          });
+        }
+
         router.back();
       } catch (error) {
         console.error("Failed to update proposal:", error);

apps/client/src/app/login.tsx

@@ -1,9 +1,12 @@
 import { useState } from "react";
-import { View, Text, TextInput, Pressable } from "react-native";
+import { View, Text, Pressable } from "react-native";
 import { Link, router } from "expo-router";
 import BaseBackground from "../components/BaseBackground";
 import AuthButton from "../components/AuthButton";
+import CustomTextInput from "../components/CustomTextInput";
 import { AuthService } from "../services";
+import { CaldavConfigService } from "../services/CaldavConfigService";
+import { preloadAppData } from "../components/AuthGuard";
 import { useThemeStore } from "../stores/ThemeStore";
 
 const LoginScreen = () => {
@@ -24,6 +27,12 @@ const LoginScreen = () => {
     setIsLoading(true);
     try {
       await AuthService.login({ identifier, password });
+      await preloadAppData();
+      try {
+        await CaldavConfigService.sync();
+      } catch {
+        // No CalDAV config or sync failed — not critical
+      }
       router.replace("/(tabs)/chat");
     } catch {
       setError("Anmeldung fehlgeschlagen. Überprüfe deine Zugangsdaten.");
@@ -51,34 +60,22 @@ const LoginScreen = () => {
           </Text>
         )}
 
-        <TextInput
+        <CustomTextInput
           placeholder="E-Mail oder Benutzername"
           placeholderTextColor={theme.textMuted}
-          value={identifier}
-          onChangeText={setIdentifier}
+          text={identifier}
+          onValueChange={setIdentifier}
           autoCapitalize="none"
           className="w-full rounded-lg p-4 mb-4"
-          style={{
-            backgroundColor: theme.secondaryBg,
-            color: theme.textPrimary,
-            borderWidth: 1,
-            borderColor: theme.borderPrimary,
-          }}
         />
 
-        <TextInput
+        <CustomTextInput
           placeholder="Passwort"
           placeholderTextColor={theme.textMuted}
-          value={password}
-          onChangeText={setPassword}
+          text={password}
+          onValueChange={setPassword}
           secureTextEntry
           className="w-full rounded-lg p-4 mb-6"
-          style={{
-            backgroundColor: theme.secondaryBg,
-            color: theme.textPrimary,
-            borderWidth: 1,
-            borderColor: theme.borderPrimary,
-          }}
         />
 
         <AuthButton

apps/client/src/app/register.tsx

@@ -1,8 +1,9 @@
 import { useState } from "react";
-import { View, Text, TextInput, Pressable } from "react-native";
+import { View, Text, Pressable } from "react-native";
 import { Link, router } from "expo-router";
 import BaseBackground from "../components/BaseBackground";
 import AuthButton from "../components/AuthButton";
+import CustomTextInput from "../components/CustomTextInput";
 import { AuthService } from "../services";
 import { useThemeStore } from "../stores/ThemeStore";
 
@@ -59,50 +60,32 @@ const RegisterScreen = () => {
           </Text>
         )}
 
-        <TextInput
+        <CustomTextInput
           placeholder="E-Mail"
           placeholderTextColor={theme.textMuted}
-          value={email}
-          onChangeText={setEmail}
+          text={email}
+          onValueChange={setEmail}
           autoCapitalize="none"
           keyboardType="email-address"
           className="w-full rounded-lg p-4 mb-4"
-          style={{
-            backgroundColor: theme.secondaryBg,
-            color: theme.textPrimary,
-            borderWidth: 1,
-            borderColor: theme.borderPrimary,
-          }}
         />
 
-        <TextInput
+        <CustomTextInput
           placeholder="Benutzername"
           placeholderTextColor={theme.textMuted}
-          value={userName}
-          onChangeText={setUserName}
+          text={userName}
+          onValueChange={setUserName}
           autoCapitalize="none"
           className="w-full rounded-lg p-4 mb-4"
-          style={{
-            backgroundColor: theme.secondaryBg,
-            color: theme.textPrimary,
-            borderWidth: 1,
-            borderColor: theme.borderPrimary,
-          }}
         />
 
-        <TextInput
+        <CustomTextInput
           placeholder="Passwort"
           placeholderTextColor={theme.textMuted}
-          value={password}
-          onChangeText={setPassword}
+          text={password}
+          onValueChange={setPassword}
           secureTextEntry
           className="w-full rounded-lg p-4 mb-6"
-          style={{
-            backgroundColor: theme.secondaryBg,
-            color: theme.textPrimary,
-            borderWidth: 1,
-            borderColor: theme.borderPrimary,
-          }}
         />
 
         <AuthButton

apps/client/src/components/AuthGuard.tsx

@@ -1,16 +1,52 @@
-import { useEffect, ReactNode } from "react";
+import { useEffect, useState, ReactNode } from "react";
 import { View, ActivityIndicator } from "react-native";
 import { Redirect } from "expo-router";
 import { useAuthStore } from "../stores";
 import { useThemeStore } from "../stores/ThemeStore";
+import { useEventsStore } from "../stores/EventsStore";
+import { useCaldavConfigStore } from "../stores/CaldavConfigStore";
+import { EventService } from "../services";
+import { CaldavConfigService } from "../services/CaldavConfigService";
 
 type AuthGuardProps = {
   children: ReactNode;
 };
 
+/**
+ * Preloads app data (events + CalDAV config) into stores.
+ * Called before the loading spinner is dismissed so screens have data immediately.
+ */
+export const preloadAppData = async () => {
+  const now = new Date();
+  const firstOfMonth = new Date(now.getFullYear(), now.getMonth(), 1);
+  const dayOfWeek = firstOfMonth.getDay();
+  const daysFromPrevMonth = dayOfWeek === 0 ? 6 : dayOfWeek - 1;
+  const startDate = new Date(
+    now.getFullYear(),
+    now.getMonth(),
+    1 - daysFromPrevMonth,
+  );
+  const endDate = new Date(startDate);
+  endDate.setDate(startDate.getDate() + 41);
+  endDate.setHours(23, 59, 59);
+
+  const [eventsResult, configResult] = await Promise.allSettled([
+    EventService.getByDateRange(startDate, endDate),
+    CaldavConfigService.getConfig(),
+  ]);
+
+  if (eventsResult.status === "fulfilled") {
+    useEventsStore.getState().setEvents(eventsResult.value);
+  }
+  if (configResult.status === "fulfilled") {
+    useCaldavConfigStore.getState().setConfig(configResult.value);
+  }
+};
+
 /**
  * Wraps content that requires authentication.
  * - Loads stored user on mount
+ * - Preloads app data (events, CalDAV config) before dismissing spinner
  * - Shows loading indicator while checking auth state
  * - Redirects to login if not authenticated
  * - Renders children if authenticated
@@ -18,12 +54,19 @@ type AuthGuardProps = {
 export const AuthGuard = ({ children }: AuthGuardProps) => {
   const { theme } = useThemeStore();
   const { isAuthenticated, isLoading, loadStoredUser } = useAuthStore();
+  const [dataReady, setDataReady] = useState(false);
 
   useEffect(() => {
-    loadStoredUser();
+    const init = async () => {
+      await loadStoredUser();
+      if (!useAuthStore.getState().isAuthenticated) return;
+      await preloadAppData();
+      setDataReady(true);
+    };
+    init();
   }, [loadStoredUser]);
 
-  if (isLoading) {
+  if (isLoading || (isAuthenticated && !dataReady)) {
     return (
       <View
         style={{

apps/client/src/components/BaseButton.tsx

@@ -2,17 +2,23 @@ import { Pressable, Text } from "react-native";
 import { useThemeStore } from "../stores/ThemeStore";
 import { ReactNode } from "react";
 
-type BaseButtonProps = {
+export type BaseButtonProps = {
   children?: ReactNode;
+  className?: string;
   onPress: () => void;
   solid?: boolean;
 };
 
-const BaseButton = ({ children, onPress, solid = false }: BaseButtonProps) => {
+const BaseButton = ({
+  className,
+  children,
+  onPress,
+  solid = false,
+}: BaseButtonProps) => {
   const { theme } = useThemeStore();
   return (
     <Pressable
-      className="w-11/12 rounded-lg p-4 mb-4 border-4"
+      className={`rounded-lg p-4 mb-4 border-4 ${className}`}
       onPress={onPress}
       style={{
         borderColor: theme.borderPrimary,

apps/client/src/components/CustomTextInput.tsx

@@ -0,0 +1,46 @@
+import { TextInput, TextInputProps } from "react-native";
+import { useThemeStore } from "../stores/ThemeStore";
+import { useState } from "react";
+
+export type CustomTextInputProps = {
+  text?: string;
+  focused?: boolean;
+  className?: string;
+  multiline?: boolean;
+  onValueChange?: (text: string) => void;
+  placeholder?: string;
+  placeholderTextColor?: string;
+  secureTextEntry?: boolean;
+  autoCapitalize?: TextInputProps["autoCapitalize"];
+  keyboardType?: TextInputProps["keyboardType"];
+};
+
+const CustomTextInput = (props: CustomTextInputProps) => {
+  const { theme } = useThemeStore();
+  const [focused, setFocused] = useState(props.focused ?? false);
+
+  return (
+    <TextInput
+      className={`border border-solid rounded-2xl ${props.className}`}
+      onChangeText={props.onValueChange}
+      value={props.text}
+      multiline={props.multiline}
+      placeholder={props.placeholder}
+      placeholderTextColor={props.placeholderTextColor}
+      secureTextEntry={props.secureTextEntry}
+      autoCapitalize={props.autoCapitalize}
+      keyboardType={props.keyboardType}
+      selection={!focused ? { start: 0 } : undefined}
+      style={{
+        backgroundColor: theme.messageBorderBg,
+        color: theme.textPrimary,
+        textAlignVertical: "top",
+        borderColor: focused ? theme.chatBot : theme.borderPrimary,
+      }}
+      onFocus={() => setFocused(true)}
+      onBlur={() => setFocused(false)}
+    />
+  );
+};
+
+export default CustomTextInput;

apps/client/src/components/DateTimePicker.tsx

@@ -126,11 +126,11 @@ const DateTimePickerButton = ({
 
 // Convenience wrappers for simpler usage
 export const DatePickerButton = (
-  props: Omit<DateTimePickerButtonProps, "mode">
+  props: Omit<DateTimePickerButtonProps, "mode">,
 ) => <DateTimePickerButton {...props} mode="date" />;
 
 export const TimePickerButton = (
-  props: Omit<DateTimePickerButtonProps, "mode">
+  props: Omit<DateTimePickerButtonProps, "mode">,
 ) => <DateTimePickerButton {...props} mode="time" />;
 
 export default DateTimePickerButton;

apps/client/src/components/EventCard.tsx

@@ -19,7 +19,7 @@ export const EventCard = ({ event, onEdit, onDelete }: EventCardProps) => {
         startTime={event.occurrenceStart}
         endTime={event.occurrenceEnd}
         description={event.description}
-        isRecurring={event.isRecurring}
+        recurrenceRule={event.recurrenceRule}
       >
         {/* Action buttons - TouchableOpacity with delayPressIn allows ScrollView to detect scroll gestures */}
         <View className="flex-row justify-end mt-3 gap-3">

apps/client/src/components/EventCardBase.tsx

@@ -8,6 +8,7 @@ import {
   formatDateWithWeekday,
   formatDateWithWeekdayShort,
   formatTime,
+  formatRecurrenceRule,
 } from "@calchat/shared";
 
 type EventCardBaseProps = {
@@ -16,7 +17,7 @@ type EventCardBaseProps = {
   startTime: Date;
   endTime: Date;
   description?: string;
-  isRecurring?: boolean;
+  recurrenceRule?: string;
   children?: ReactNode;
 };
 
@@ -46,7 +47,7 @@ export const EventCardBase = ({
   startTime,
   endTime,
   description,
-  isRecurring,
+  recurrenceRule,
   children,
 }: EventCardBaseProps) => {
   const { theme } = useThemeStore();
@@ -95,7 +96,7 @@ export const EventCardBase = ({
       </View>
 
       {/* Recurring indicator */}
-      {isRecurring && (
+      {recurrenceRule && (
         <View className="flex-row items-center mb-1">
           <Feather
             name="repeat"
@@ -103,7 +104,9 @@ export const EventCardBase = ({
             color={theme.textPrimary}
             style={{ marginRight: 8 }}
           />
-          <Text style={{ color: theme.textPrimary }}>Wiederkehrend</Text>
+          <Text style={{ color: theme.textPrimary }}>
+            {formatRecurrenceRule(recurrenceRule)}
+          </Text>
         </View>
       )}
 

apps/client/src/components/ProposedEventCard.tsx

@@ -1,6 +1,6 @@
 import { View, Text, Pressable } from "react-native";
-import { Feather } from "@expo/vector-icons";
-import { ProposedEventChange, formatDate } from "@calchat/shared";
+import { Feather, Ionicons } from "@expo/vector-icons";
+import { ProposedEventChange, formatDate, formatTime } from "@calchat/shared";
 import { rrulestr } from "rrule";
 import { useThemeStore } from "../stores/ThemeStore";
 import { EventCardBase } from "./EventCardBase";
@@ -113,7 +113,7 @@ export const ProposedEventCard = ({
         startTime={event.startTime}
         endTime={event.endTime}
         description={event.description}
-        isRecurring={!!event.recurrenceRule}
+        recurrenceRule={event.recurrenceRule}
       >
         {/* Show new exception date for delete/single actions */}
         {newExceptionDate && (
@@ -124,8 +124,12 @@ export const ProposedEventCard = ({
               color={theme.confirmButton}
               style={{ marginRight: 8 }}
             />
-            <Text style={{ color: theme.confirmButton }} className="font-medium">
-              Neue Ausnahme: {formatDate(new Date(proposedChange.occurrenceDate!))}
+            <Text
+              style={{ color: theme.confirmButton }}
+              className="font-medium"
+            >
+              Neue Ausnahme:{" "}
+              {formatDate(new Date(proposedChange.occurrenceDate!))}
             </Text>
           </View>
         )}
@@ -138,11 +142,37 @@ export const ProposedEventCard = ({
               color={theme.confirmButton}
               style={{ marginRight: 8 }}
             />
-            <Text style={{ color: theme.confirmButton }} className="font-medium">
+            <Text
+              style={{ color: theme.confirmButton }}
+              className="font-medium"
+            >
               Neues Ende: {formatDate(newUntilDate)}
             </Text>
           </View>
         )}
+        {/* Show conflicting events warning */}
+        {proposedChange.conflictingEvents &&
+          proposedChange.conflictingEvents.length > 0 && (
+            <View className="mb-2">
+              {proposedChange.conflictingEvents.map((conflict, index) => (
+                <View key={index} className="flex-row items-center mt-1">
+                  <Ionicons
+                    name="alert-circle"
+                    size={16}
+                    color={theme.rejectButton}
+                    style={{ marginRight: 8 }}
+                  />
+                  <Text
+                    style={{ color: theme.rejectButton }}
+                    className="text-sm flex-1"
+                  >
+                    Konflikt: {conflict.title} ({formatTime(conflict.startTime)}{" "}
+                    - {formatTime(conflict.endTime)})
+                  </Text>
+                </View>
+              ))}
+            </View>
+          )}
         <ActionButtons
           isDisabled={isDisabled}
           respondedAction={proposedChange.respondedAction}

apps/client/src/services/CaldavConfigService.ts

@@ -0,0 +1,32 @@
+import { CalendarEvent, CaldavConfig } from "@calchat/shared";
+import { ApiClient } from "./ApiClient";
+
+export const CaldavConfigService = {
+  saveConfig: async (
+    serverUrl: string,
+    username: string,
+    password: string,
+  ): Promise<CaldavConfig> => {
+    return ApiClient.put<CaldavConfig>("/caldav/config", {
+      serverUrl,
+      username,
+      password,
+    });
+  },
+  getConfig: async (): Promise<CaldavConfig> => {
+    return ApiClient.get<CaldavConfig>("/caldav/config");
+  },
+  deleteConfig: async (): Promise<void> => {
+    return ApiClient.delete<void>("/caldav/config");
+  },
+  pull: async (): Promise<CalendarEvent[]> => {
+    return ApiClient.post<CalendarEvent[]>("/caldav/pull");
+  },
+  pushAll: async (): Promise<void> => {
+    return ApiClient.post<void>("/caldav/pushAll");
+  },
+  sync: async (): Promise<void> => {
+    await ApiClient.post<void>("/caldav/pushAll");
+    await ApiClient.post<CalendarEvent[]>("/caldav/pull");
+  },
+};

apps/client/src/stores/CaldavConfigStore.ts

@@ -0,0 +1,14 @@
+import { create } from "zustand";
+import { CaldavConfig } from "@calchat/shared";
+
+interface CaldavConfigState {
+  config: CaldavConfig | null;
+  setConfig: (config: CaldavConfig | null) => void;
+}
+
+export const useCaldavConfigStore = create<CaldavConfigState>((set) => ({
+  config: null,
+  setConfig: (config: CaldavConfig | null) => {
+    set({ config });
+  },
+}));

apps/client/src/stores/index.ts

@@ -5,3 +5,4 @@ export {
   type MessageData,
 } from "./ChatStore";
 export { useEventsStore } from "./EventsStore";
+export { useCaldavConfigStore } from "./CaldavConfigStore";

apps/server/.env.example

@@ -0,0 +1,28 @@
+# OpenAI API key for GPT-based chat assistant
+# Required for AI chat functionality
+OPENAI_API_KEY=sk-proj-your-key-here
+
+# Port the server listens on
+# Default: 3000
+PORT=3000
+
+# MongoDB connection URI
+# Default: mongodb://localhost:27017/calchat
+# The Docker Compose setup uses root:mongoose credentials with authSource=admin
+MONGODB_URI=mongodb://root:mongoose@localhost:27017/calchat?authSource=admin
+
+# Use static test responses instead of real GPT calls
+# Values: true | false
+# Default: false
+USE_TEST_RESPONSES=false
+
+# Log level for pino logger
+# Values: debug | info | warn | error | fatal
+# Default: debug (development), info (production)
+LOG_LEVEL=debug
+
+# Node environment
+# Values: development | production
+# development = pretty-printed logs, production = JSON logs
+# Default: development
+NODE_ENV=development

apps/server/docker/Dockerfile

@@ -0,0 +1,31 @@
+FROM node:alpine AS build
+
+WORKDIR /app
+
+COPY package.json package-lock.json tsconfig.json ./
+COPY packages/shared/package.json ./packages/shared/
+COPY apps/server/package.json ./apps/server/
+
+RUN npm ci -w @calchat/server -w @calchat/shared --include-workspace-root
+
+COPY packages/shared/ packages/shared/
+COPY apps/server/ apps/server/
+
+RUN npm run build -w @calchat/shared && npm run build -w @calchat/server
+
+FROM node:alpine
+
+WORKDIR /app
+
+COPY --from=build /app/package.json /app/package-lock.json ./
+COPY --from=build /app/packages/shared/package.json packages/shared/
+COPY --from=build /app/apps/server/package.json apps/server/
+
+RUN npm ci --omit=dev -w @calchat/server -w @calchat/shared
+
+COPY --from=build /app/packages/shared/dist/ packages/shared/dist/
+COPY --from=build /app/apps/server/dist/ apps/server/dist/
+
+EXPOSE 3001
+
+CMD ["node", "apps/server/dist/app.js"]

apps/server/docker/radicale/docker-compose.yml

@@ -0,0 +1,25 @@
+name: Radicale
+services:
+    radicale:
+        image: ghcr.io/kozea/radicale:stable
+        ports:
+        - 5232:5232
+        volumes:
+          - config:/etc/radicale
+          - data:/var/lib/radicale
+
+volumes:
+  config:
+    name: radicale-config
+    driver: local
+    driver_opts:
+      type: none
+      o: bind
+      device: ./config
+  data:
+    name: radicale-data
+    driver: local
+    driver_opts:
+      type: none
+      o: bind
+      device: ./data

apps/server/jest.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  preset: "ts-jest",
+  testEnvironment: "node",
+  testPathIgnorePatterns: ["/node_modules/", "/dist/"],
+};

apps/server/package.json

@@ -3,28 +3,33 @@
   "version": "1.0.0",
   "private": true,
   "scripts": {
-    "dev": "tsx watch src/app.ts",
-    "build": "tsc",
-    "start": "node dist/app.js"
+    "dev": "npm run build --workspace=@calchat/shared && tsx watch src/app.ts",
+    "build": "npm run build --workspace=@calchat/shared && tsc",
+    "start": "node dist/app.js",
+    "test": "jest"
   },
   "dependencies": {
     "@calchat/shared": "*",
     "bcrypt": "^6.0.0",
     "dotenv": "^16.4.7",
     "express": "^5.2.1",
-    "jsonwebtoken": "^9.0.3",
+    "ical.js": "^2.2.1",
     "mongoose": "^9.1.1",
     "openai": "^6.15.0",
     "pino": "^10.1.1",
     "pino-http": "^11.0.0",
-    "rrule": "^2.8.1"
+    "pino-pretty": "^13.1.3",
+    "rrule": "^2.8.1",
+    "tsdav": "^2.1.6"
   },
   "devDependencies": {
     "@types/bcrypt": "^6.0.0",
     "@types/express": "^5.0.6",
-    "@types/jsonwebtoken": "^9.0.10",
+    "@types/ical": "^0.8.3",
+    "@types/jest": "^30.0.0",
     "@types/node": "^24.10.1",
-    "pino-pretty": "^13.1.3",
+    "jest": "^30.2.0",
+    "ts-jest": "^29.4.6",
     "tsx": "^4.21.0",
     "typescript": "^5.9.3"
   }

apps/server/src/ai/GPTAdapter.ts

@@ -8,6 +8,11 @@ import {
   ToolDefinition,
 } from "./utils";
 import { Logged } from "../logging";
+import {
+  ChatCompletionMessageParam,
+  ChatCompletionMessageToolCall,
+  ChatCompletionTool,
+} from "openai/resources/chat/completions/completions";
 
 /**
  * Convert tool definitions to OpenAI format.
@@ -29,7 +34,7 @@ function toOpenAITools(
 export class GPTAdapter implements AIProvider {
   private client: OpenAI;
   private model: string;
-  private tools: OpenAI.Chat.Completions.ChatCompletionTool[];
+  private tools: ChatCompletionTool[];
 
   constructor(apiKey?: string, model: string = "gpt-5-mini") {
     this.client = new OpenAI({
@@ -46,7 +51,7 @@ export class GPTAdapter implements AIProvider {
     const systemPrompt = buildSystemPrompt(context);
 
     // Build messages array with conversation history
-    const messages: OpenAI.Chat.Completions.ChatCompletionMessageParam[] = [
+    const messages: ChatCompletionMessageParam[] = [
       { role: "developer", content: systemPrompt },
     ];
 
@@ -87,17 +92,21 @@ export class GPTAdapter implements AIProvider {
         };
       }
 
-      // Process tool calls
+      // Process all tool calls and collect results
+      const toolResults: Array<{
+        toolCall: ChatCompletionMessageToolCall;
+        content: string;
+      }> = [];
+
       for (const toolCall of assistantMessage.tool_calls) {
-        // Skip non-function tool calls
         if (toolCall.type !== "function") continue;
 
         const { name, arguments: argsRaw } = toolCall.function;
         const args = JSON.parse(argsRaw);
 
-        const result = executeToolCall(name, args, context);
+        const result = await executeToolCall(name, args, context);
 
-        // If the tool returned a proposedChange, add it to the array with unique ID
+        // Collect proposed changes
         if (result.proposedChange) {
           proposedChanges.push({
             id: `proposal-${proposalIndex++}`,
@@ -105,17 +114,22 @@ export class GPTAdapter implements AIProvider {
           });
         }
 
-        // Add assistant message with tool call
-        messages.push({
-          role: "assistant",
-          tool_calls: [toolCall],
-        });
+        toolResults.push({ toolCall, content: result.content });
+      }
 
-        // Add tool result
+      // Add assistant message with ALL tool calls at once
+      messages.push({
+        role: "assistant",
+        tool_calls: assistantMessage.tool_calls,
+        content: assistantMessage.content,
+      });
+
+      // Add all tool results
+      for (const { toolCall, content } of toolResults) {
         messages.push({
           role: "tool",
           tool_call_id: toolCall.id,
-          content: result.content,
+          content,
         });
       }
     }

apps/server/src/ai/utils/eventFormatter.ts

@@ -1,30 +0,0 @@
-import {
-  CalendarEvent,
-  formatDate,
-  formatTime,
-  formatDateTime,
-} from "@calchat/shared";
-
-// Re-export for backwards compatibility
-export { formatDate, formatTime, formatDateTime };
-
-/**
- * Format a list of events for display in the system prompt.
- * Output is in German with date/time formatting.
- */
-export function formatExistingEvents(events: CalendarEvent[]): string {
-  if (events.length === 0) {
-    return "Keine Termine vorhanden.";
-  }
-
-  return events
-    .map((e) => {
-      const start = new Date(e.startTime);
-      const end = new Date(e.endTime);
-      const timeStr = `${formatTime(start)} - ${formatTime(end)}`;
-      const recurring = e.isRecurring ? " (wiederkehrend)" : "";
-      const desc = e.description ? ` | ${e.description}` : "";
-      return `- ${e.title} (ID: ${e.id}) | ${formatDate(start)} ${timeStr}${recurring}${desc}`;
-    })
-    .join("\n");
-}

apps/server/src/ai/utils/index.ts

@@ -1,9 +1,3 @@
-export {
-  formatExistingEvents,
-  formatDate,
-  formatTime,
-  formatDateTime,
-} from "./eventFormatter";
 export { buildSystemPrompt } from "./systemPrompt";
 export {
   TOOL_DEFINITIONS,

apps/server/src/ai/utils/systemPrompt.ts

@@ -1,5 +1,4 @@
 import { AIContext } from "../../services/interfaces";
-import { formatExistingEvents } from "./eventFormatter";
 
 /**
  * Build the system prompt for the AI assistant.
@@ -15,8 +14,6 @@ export function buildSystemPrompt(context: AIContext): string {
     minute: "2-digit",
   });
 
-  const eventsText = formatExistingEvents(context.existingEvents);
-
   return `Du bist ein hilfreicher Kalender-Assistent für die App "CalChat".
 Du hilfst Benutzern beim Erstellen, Ändern und Löschen von Terminen.
 Antworte immer auf Deutsch.
@@ -29,8 +26,16 @@ Wichtige Regeln:
 - Wenn der Benutzer einen Termin ändern will, nutze proposeUpdateEvent mit der Event-ID
 - Wenn der Benutzer einen Termin löschen will, nutze proposeDeleteEvent mit der Event-ID
 - Du kannst mehrere Event-Vorschläge in einer Antwort machen (z.B. für mehrere Termine auf einmal)
-- Wenn der Benutzer nach seinen Terminen fragt, nutze die unten stehende Liste
-- Nutze searchEvents um nach Terminen zu suchen, wenn du die genaue ID brauchst
+- WICHTIG: Bei Terminen in der VERGANGENHEIT: Weise den Benutzer darauf hin und erstelle KEIN Event. Beispiel: "Das Datum liegt in der Vergangenheit. Meintest du vielleicht [nächstes Jahr]?"
+- KRITISCH: Wenn ein Tool-Result eine ⚠️-Warnung enthält (z.B. "Zeitkonflikt mit..."), MUSST du diese dem Benutzer mitteilen! Ignoriere NIEMALS solche Warnungen! Beispiel: "An diesem Tag hast du bereits 'Jannes Geburtstag'. Soll ich den Termin trotzdem erstellen?"
+
+WICHTIG - Event-Abfragen:
+- Du hast KEINEN vorgeladenen Kalender-Kontext!
+- Nutze IMMER getEventsInRange um Events zu laden, wenn der Benutzer nach Terminen fragt
+- Nutze searchEvents um nach Terminen per Titel zu suchen (gibt auch die Event-ID zurück)
+- Beispiel: "Was habe ich heute?" → getEventsInRange für heute
+- Beispiel: "Was habe ich diese Woche?" → getEventsInRange für die Woche
+- Beispiel: "Wann ist der Zahnarzt?" → searchEvents mit "Zahnarzt"
 
 WICHTIG - Tool-Verwendung:
 - Du MUSST die proposeCreateEvent/proposeUpdateEvent/proposeDeleteEvent Tools verwenden, um Termine vorzuschlagen!
@@ -50,18 +55,21 @@ WICHTIG - Wiederkehrende Termine (RRULE):
 - WICHTIG: Schreibe die RRULE NIEMALS in das description-Feld! Nutze IMMER das recurrenceRule-Feld!
 
 WICHTIG - Antwortformat:
-- Halte deine Textantworten SEHR KURZ (1-2 Sätze maximal)
-- Die Event-Details (Titel, Datum, Uhrzeit, Beschreibung) werden dem Benutzer automatisch in separaten Karten angezeigt
-- Wiederhole NIEMALS die Event-Details im Text! Der Benutzer sieht sie bereits in den Karten
 - Verwende kontextbezogene Antworten in der GEGENWARTSFORM je nach Aktion:
   - Bei Termin-Erstellung: "Ich schlage folgenden Termin vor:" oder "Neuer Termin:"
   - Bei Termin-Änderung: "Ich schlage folgende Änderung vor:" oder "Änderung:"
   - Bei Termin-Löschung: "Ich schlage vor, diesen Termin zu löschen:" oder "Löschung:"
-  - Bei Übersichten: "Hier sind deine Termine:"
 - WICHTIG: Verwende NIEMALS Vergangenheitsform wie "Ich habe ... vorgeschlagen" - immer Gegenwartsform!
-- Schlechte Beispiele: "Alles klar!" (zu unspezifisch), lange Listen mit Termin-Details im Text
-- Bei Rückfragen oder wenn keine Termine erstellt werden, kannst du ausführlicher antworten
 
-Existierende Termine des Benutzers:
-${eventsText}`;
+WICHTIG - Unterscheide zwischen PROPOSALS und ABFRAGEN:
+1. Bei PROPOSALS (proposeCreateEvent/proposeUpdateEvent/proposeDeleteEvent):
+   - Halte deine Textantworten SEHR KURZ (1-2 Sätze)
+   - Die Event-Details werden automatisch in Karten angezeigt
+   - Wiederhole NICHT die Details im Text
+2. Bei ABFRAGEN (searchEvents, getEventsInRange, oder Fragen zu existierenden Terminen):
+   - Du MUSST die gefundenen Termine im Text nennen!
+   - Liste die relevanten Termine mit Titel, Datum und Uhrzeit auf
+   - NIEMALS Event-IDs dem Benutzer zeigen! Die IDs sind nur für dich intern
+   - Wenn keine Termine gefunden wurden, sage das explizit (z.B. "In diesem Zeitraum hast du keine Termine.")
+   - Beispiel: "Heute hast du: Zahnarzt um 10:00 Uhr, Meeting um 14:00 Uhr."`;
 }

apps/server/src/ai/utils/toolDefinitions.ts

@@ -179,4 +179,23 @@ export const TOOL_DEFINITIONS: ToolDefinition[] = [
       required: ["query"],
     },
   },
+  {
+    name: "getEventsInRange",
+    description:
+      "Load events from a specific date range. Use this when the user asks about a time period beyond the default 4 weeks (e.g., 'birthdays in the next 6 months', 'what do I have planned for summer').",
+    parameters: {
+      type: "object",
+      properties: {
+        startDate: {
+          type: "string",
+          description: "Start date as ISO string (YYYY-MM-DD)",
+        },
+        endDate: {
+          type: "string",
+          description: "End date as ISO string (YYYY-MM-DD)",
+        },
+      },
+      required: ["startDate", "endDate"],
+    },
+  },
 ];

apps/server/src/ai/utils/toolExecutor.ts

@@ -6,7 +6,19 @@ import {
   RecurringDeleteMode,
 } from "@calchat/shared";
 import { AIContext } from "../../services/interfaces";
-import { formatDate, formatTime, formatDateTime } from "./eventFormatter";
+import { formatDate, formatTime, formatDateTime } from "@calchat/shared";
+
+/**
+ * Check if two time ranges overlap.
+ */
+function hasTimeOverlap(
+  start1: Date,
+  end1: Date,
+  start2: Date,
+  end2: Date,
+): boolean {
+  return start1 < end2 && end1 > start2;
+}
 
 /**
  * Proposed change without ID - ID is added by GPTAdapter when collecting proposals
@@ -24,12 +36,13 @@ export interface ToolResult {
 /**
  * Execute a tool call and return the result.
  * This function is provider-agnostic and can be used with any LLM.
+ * Async to support tools that need to fetch data (e.g., getEventsInRange).
  */
-export function executeToolCall(
+export async function executeToolCall(
   name: string,
   args: Record<string, unknown>,
   context: AIContext,
-): ToolResult {
+): Promise<ToolResult> {
   switch (name) {
     case "getDay": {
       const date = getDay(
@@ -62,20 +75,52 @@ export function executeToolCall(
       const dateStr = formatDate(event.startTime);
       const startStr = formatTime(event.startTime);
       const endStr = formatTime(event.endTime);
+
+      // Check for conflicts - fetch events for the specific day
+      const dayStart = new Date(event.startTime);
+      dayStart.setHours(0, 0, 0, 0);
+      const dayEnd = new Date(dayStart);
+      dayEnd.setDate(dayStart.getDate() + 1);
+
+      const dayEvents = await context.fetchEventsInRange(dayStart, dayEnd);
+
+      // Use occurrenceStart/occurrenceEnd for expanded recurring events
+      const conflicts = dayEvents.filter((e) =>
+        hasTimeOverlap(
+          event.startTime,
+          event.endTime,
+          new Date(e.occurrenceStart),
+          new Date(e.occurrenceEnd),
+        ),
+      );
+
+      // Build conflict warning if any
+      let conflictWarning = "";
+      if (conflicts.length > 0) {
+        const conflictNames = conflicts.map((c) => `"${c.title}"`).join(", ");
+        conflictWarning = `\n⚠️ ACHTUNG: Zeitkonflikt mit ${conflictNames}!`;
+      }
+
       return {
-        content: `Event-Vorschlag erstellt: "${event.title}" am ${dateStr} von ${startStr} bis ${endStr} Uhr`,
+        content: `Event-Vorschlag erstellt: "${event.title}" am ${dateStr} von ${startStr} bis ${endStr} Uhr${conflictWarning}`,
         proposedChange: {
           action: "create",
           event,
+          conflictingEvents:
+            conflicts.length > 0
+              ? conflicts.map((c) => ({
+                  title: c.title,
+                  startTime: new Date(c.occurrenceStart),
+                  endTime: new Date(c.occurrenceEnd),
+                }))
+              : undefined,
         },
       };
     }
 
     case "proposeUpdateEvent": {
       const eventId = args.eventId as string;
-      const existingEvent = context.existingEvents.find(
-        (e) => e.id === eventId,
-      );
+      const existingEvent = await context.fetchEventById(eventId);
 
       if (!existingEvent) {
         return { content: `Event mit ID ${eventId} nicht gefunden.` };
@@ -116,9 +161,7 @@ export function executeToolCall(
       const eventId = args.eventId as string;
       const deleteMode = (args.deleteMode as RecurringDeleteMode) || "all";
       const occurrenceDate = args.occurrenceDate as string | undefined;
-      const existingEvent = context.existingEvents.find(
-        (e) => e.id === eventId,
-      );
+      const existingEvent = await context.fetchEventById(eventId);
 
       if (!existingEvent) {
         return { content: `Event mit ID ${eventId} nicht gefunden.` };
@@ -162,25 +205,46 @@ export function executeToolCall(
     }
 
     case "searchEvents": {
-      const query = (args.query as string).toLowerCase();
-      const matches = context.existingEvents.filter((e) =>
-        e.title.toLowerCase().includes(query),
-      );
+      const query = args.query as string;
+      const matches = await context.searchEvents(query);
 
       if (matches.length === 0) {
-        return { content: `Keine Termine mit "${args.query}" gefunden.` };
+        return { content: `Keine Termine mit "${query}" gefunden.` };
       }
 
       const results = matches
         .map((e) => {
           const start = new Date(e.startTime);
-          return `- ${e.title} (ID: ${e.id}) am ${formatDate(start)} um ${formatTime(start)} Uhr`;
+          const recurrenceInfo = e.recurrenceRule ? " (wiederkehrend)" : "";
+          return `- ${e.title} (ID: ${e.id}) am ${formatDate(start)} um ${formatTime(start)} Uhr${recurrenceInfo}`;
         })
         .join("\n");
 
       return { content: `Gefundene Termine:\n${results}` };
     }
 
+    case "getEventsInRange": {
+      const startDate = new Date(args.startDate as string);
+      const endDate = new Date(args.endDate as string);
+      const events = await context.fetchEventsInRange(startDate, endDate);
+
+      if (events.length === 0) {
+        return { content: "Keine Termine in diesem Zeitraum." };
+      }
+
+      const eventsText = events
+        .map((e) => {
+          const start = new Date(e.occurrenceStart);
+          const recurrenceInfo = e.recurrenceRule ? " (wiederkehrend)" : "";
+          return `- ${e.title} (ID: ${e.id}) am ${formatDate(start)} um ${formatTime(start)} Uhr${recurrenceInfo}`;
+        })
+        .join("\n");
+
+      return {
+        content: `Termine von ${formatDate(startDate)} bis ${formatDate(endDate)}:\n${eventsText}`,
+      };
+    }
+
     default:
       return { content: `Unbekannte Funktion: ${name}` };
   }

apps/server/src/app.ts

@@ -17,6 +17,9 @@ import {
 } from "./repositories";
 import { GPTAdapter } from "./ai";
 import { logger } from "./logging";
+import { MongoCaldavRepository } from "./repositories/mongo/MongoCaldavRepository";
+import { CaldavService } from "./services/CaldavService";
+import { CaldavController } from "./controllers/CaldavController";
 
 const app = express();
 const port = process.env.PORT || 3000;
@@ -51,6 +54,7 @@ if (process.env.NODE_ENV !== "production") {
 const userRepo = new MongoUserRepository();
 const eventRepo = new MongoEventRepository();
 const chatRepo = new MongoChatRepository();
+const caldavRepo = new MongoCaldavRepository();
 
 // Initialize AI provider
 const aiProvider = new GPTAdapter();
@@ -58,17 +62,14 @@ const aiProvider = new GPTAdapter();
 // Initialize services
 const authService = new AuthService(userRepo);
 const eventService = new EventService(eventRepo);
-const chatService = new ChatService(
-  chatRepo,
-  eventRepo,
-  eventService,
-  aiProvider,
-);
+const caldavService = new CaldavService(caldavRepo, eventService);
+const chatService = new ChatService(chatRepo, eventService, aiProvider);
 
 // Initialize controllers
 const authController = new AuthController(authService);
-const chatController = new ChatController(chatService);
-const eventController = new EventController(eventService);
+const chatController = new ChatController(chatService, caldavService);
+const eventController = new EventController(eventService, caldavService);
+const caldavController = new CaldavController(caldavService);
 
 // Setup routes
 app.use(
@@ -77,6 +78,7 @@ app.use(
     authController,
     chatController,
     eventController,
+    caldavController,
   }),
 );
 
@@ -96,8 +98,10 @@ app.post("/api/ai/test", async (req, res) => {
     const result = await aiProvider.processMessage(message, {
       userId: "test-user",
       conversationHistory: [],
-      existingEvents: [],
       currentDate: new Date(),
+      fetchEventsInRange: async () => [],
+      searchEvents: async () => [],
+      fetchEventById: async () => null,
     });
     res.json(result);
   } catch (error) {

apps/server/src/controllers/AuthController.ts

@@ -21,12 +21,4 @@ export class AuthController {
       res.status(400).json({ error: (error as Error).message });
     }
   }
-
-  async refresh(req: Request, res: Response): Promise<void> {
-    throw new Error("Not implemented");
-  }
-
-  async logout(req: Request, res: Response): Promise<void> {
-    throw new Error("Not implemented");
-  }
 }

apps/server/src/controllers/CaldavController.ts

@@ -0,0 +1,103 @@
+import { Response } from "express";
+import { createLogger } from "../logging/logger";
+import { AuthenticatedRequest } from "./AuthMiddleware";
+import { CaldavConfig } from "@calchat/shared";
+import { CaldavService } from "../services/CaldavService";
+
+const log = createLogger("CaldavController");
+
+export class CaldavController {
+  constructor(private caldavService: CaldavService) {}
+
+  async saveConfig(req: AuthenticatedRequest, res: Response): Promise<void> {
+    try {
+      const config: CaldavConfig = { userId: req.user!.userId, ...req.body };
+      const response = await this.caldavService.saveConfig(config);
+      res.json(response);
+    } catch (error) {
+      log.error(
+        { err: error, userId: req.user?.userId },
+        "Error saving config",
+      );
+      res.status(500).json({ error: "Failed to save config" });
+    }
+  }
+
+  async loadConfig(req: AuthenticatedRequest, res: Response): Promise<void> {
+    try {
+      const config = await this.caldavService.getConfig(req.user!.userId);
+      if (!config) {
+        res.status(404).json({ error: "No CalDAV config found" });
+        return;
+      }
+      // Don't expose the password to the client
+      res.json(config);
+    } catch (error) {
+      log.error(
+        { err: error, userId: req.user?.userId },
+        "Error loading config",
+      );
+      res.status(500).json({ error: "Failed to load config" });
+    }
+  }
+
+  async deleteConfig(req: AuthenticatedRequest, res: Response): Promise<void> {
+    try {
+      await this.caldavService.deleteConfig(req.user!.userId);
+      res.status(204).send();
+    } catch (error) {
+      log.error(
+        { err: error, userId: req.user?.userId },
+        "Error deleting config",
+      );
+      res.status(500).json({ error: "Failed to delete config" });
+    }
+  }
+
+  async pullEvents(req: AuthenticatedRequest, res: Response): Promise<void> {
+    try {
+      const events = await this.caldavService.pullEvents(req.user!.userId);
+      res.json(events);
+    } catch (error) {
+      log.error(
+        { err: error, userId: req.user?.userId },
+        "Error pulling events",
+      );
+      res.status(500).json({ error: "Failed to pull events" });
+    }
+  }
+
+  async pushEvents(req: AuthenticatedRequest, res: Response): Promise<void> {
+    try {
+      await this.caldavService.pushAll(req.user!.userId);
+      res.status(204).send();
+    } catch (error) {
+      log.error(
+        { err: error, userId: req.user?.userId },
+        "Error pushing events",
+      );
+      res.status(500).json({ error: "Failed to push events" });
+    }
+  }
+
+  async pushEvent(req: AuthenticatedRequest, res: Response): Promise<void> {
+    try {
+      const event = await this.caldavService.findEventByCaldavUUID(
+        req.user!.userId,
+        req.params.caldavUUID,
+      );
+      if (!event) {
+        res.status(404).json({ error: "Event not found" });
+        return;
+      }
+      await this.caldavService.pushEvent(req.user!.userId, event);
+      res.status(204).send();
+    } catch (error) {
+      log.error(
+        { err: error, userId: req.user?.userId },
+        "Error pushing event",
+      );
+      res.status(500).json({ error: "Failed to push event" });
+    }
+  }
+}

apps/server/src/controllers/ChatController.ts

@@ -8,13 +8,17 @@ import {
   RecurringDeleteMode,
 } from "@calchat/shared";
 import { ChatService } from "../services";
+import { CaldavService } from "../services/CaldavService";
 import { createLogger } from "../logging";
 import { AuthenticatedRequest } from "./AuthMiddleware";
 
 const log = createLogger("ChatController");
 
 export class ChatController {
-  constructor(private chatService: ChatService) {}
+  constructor(
+    private chatService: ChatService,
+    private caldavService: CaldavService,
+  ) {}
 
   async sendMessage(req: AuthenticatedRequest, res: Response): Promise<void> {
     try {
@@ -24,7 +28,7 @@ export class ChatController {
       res.json(response);
     } catch (error) {
       log.error(
-        { error, userId: req.user?.userId },
+        { err: error, userId: req.user?.userId },
         "Error processing message",
       );
       res.status(500).json({ error: "Failed to process message" });
@@ -68,10 +72,20 @@ export class ChatController {
         deleteMode,
         occurrenceDate,
       );
+
+      // Sync confirmed event to CalDAV
+      try {
+        if (await this.caldavService.getConfig(userId)) {
+          await this.caldavService.pushAll(userId);
+        }
+      } catch (error) {
+        log.error({ err: error, userId }, "CalDAV push after confirm failed");
+      }
+
       res.json(response);
     } catch (error) {
       log.error(
-        { error, conversationId: req.params.conversationId },
+        { err: error, conversationId: req.params.conversationId },
         "Error confirming event",
       );
       res.status(500).json({ error: "Failed to confirm event" });
@@ -92,7 +106,7 @@ export class ChatController {
       res.json(response);
     } catch (error) {
       log.error(
-        { error, conversationId: req.params.conversationId },
+        { err: error, conversationId: req.params.conversationId },
         "Error rejecting event",
       );
       res.status(500).json({ error: "Failed to reject event" });
@@ -109,7 +123,7 @@ export class ChatController {
       res.json(conversations);
     } catch (error) {
       log.error(
-        { error, userId: req.user?.userId },
+        { err: error, userId: req.user?.userId },
         "Error getting conversations",
       );
       res.status(500).json({ error: "Failed to get conversations" });
@@ -143,7 +157,7 @@ export class ChatController {
         res.status(404).json({ error: "Conversation not found" });
       } else {
         log.error(
-          { error, conversationId: req.params.id },
+          { err: error, conversationId: req.params.id },
           "Error getting conversation",
         );
         res.status(500).json({ error: "Failed to get conversation" });
@@ -173,7 +187,7 @@ export class ChatController {
       }
     } catch (error) {
       log.error(
-        { error, messageId: req.params.messageId },
+        { err: error, messageId: req.params.messageId },
         "Error updating proposal event",
       );
       res.status(500).json({ error: "Failed to update proposal event" });

apps/server/src/controllers/EventController.ts

@@ -1,20 +1,49 @@
 import { Response } from "express";
-import { RecurringDeleteMode } from "@calchat/shared";
+import { CalendarEvent, RecurringDeleteMode } from "@calchat/shared";
 import { EventService } from "../services";
 import { createLogger } from "../logging";
 import { AuthenticatedRequest } from "./AuthMiddleware";
+import { CaldavService } from "../services/CaldavService";
 
 const log = createLogger("EventController");
 
 export class EventController {
-  constructor(private eventService: EventService) {}
+  constructor(
+    private eventService: EventService,
+    private caldavService: CaldavService,
+  ) {}
+
+  private async pushToCaldav(userId: string, event: CalendarEvent) {
+    if (await this.caldavService.getConfig(userId)) {
+      try {
+        await this.caldavService.pushEvent(userId, event);
+      } catch (error) {
+        log.error({ err: error, userId }, "Error pushing event to CalDAV");
+      }
+    }
+  }
+
+  private async deleteFromCaldav(userId: string, event: CalendarEvent) {
+    if (event.caldavUUID && (await this.caldavService.getConfig(userId))) {
+      try {
+        await this.caldavService.deleteEvent(userId, event.caldavUUID);
+      } catch (error) {
+        log.error({ err: error, userId }, "Error deleting event from CalDAV");
+      }
+    }
+  }
 
   async create(req: AuthenticatedRequest, res: Response): Promise<void> {
     try {
-      const event = await this.eventService.create(req.user!.userId, req.body);
+      const userId = req.user!.userId;
+      const event = await this.eventService.create(userId, req.body);
+      await this.pushToCaldav(userId, event);
       res.status(201).json(event);
     } catch (error) {
-      log.error({ error, userId: req.user?.userId }, "Error creating event");
+      log.error(
+        { err: error, userId: req.user?.userId },
+        "Error creating event",
+      );
       res.status(500).json({ error: "Failed to create event" });
     }
   }
@@ -31,7 +60,7 @@ export class EventController {
       }
       res.json(event);
     } catch (error) {
-      log.error({ error, eventId: req.params.id }, "Error getting event");
+      log.error({ err: error, eventId: req.params.id }, "Error getting event");
       res.status(500).json({ error: "Failed to get event" });
     }
   }
@@ -41,7 +70,10 @@ export class EventController {
       const events = await this.eventService.getAll(req.user!.userId);
       res.json(events);
     } catch (error) {
-      log.error({ error, userId: req.user?.userId }, "Error getting events");
+      log.error(
+        { err: error, userId: req.user?.userId },
+        "Error getting events",
+      );
       res.status(500).json({ error: "Failed to get events" });
     }
   }
@@ -74,7 +106,7 @@ export class EventController {
       res.json(events);
     } catch (error) {
       log.error(
-        { error, start: req.query.start, end: req.query.end },
+        { err: error, start: req.query.start, end: req.query.end },
         "Error getting events by range",
       );
       res.status(500).json({ error: "Failed to get events" });
@@ -83,67 +115,69 @@ export class EventController {
 
   async update(req: AuthenticatedRequest, res: Response): Promise<void> {
     try {
+      const userId = req.user!.userId;
       const event = await this.eventService.update(
         req.params.id,
-        req.user!.userId,
+        userId,
         req.body,
       );
       if (!event) {
         res.status(404).json({ error: "Event not found" });
         return;
       }
+
+      await this.pushToCaldav(userId, event);
+
       res.json(event);
     } catch (error) {
-      log.error({ error, eventId: req.params.id }, "Error updating event");
+      log.error({ err: error, eventId: req.params.id }, "Error updating event");
       res.status(500).json({ error: "Failed to update event" });
     }
   }
 
   async delete(req: AuthenticatedRequest, res: Response): Promise<void> {
     try {
+      const userId = req.user!.userId;
       const { mode, occurrenceDate } = req.query as {
         mode?: RecurringDeleteMode;
         occurrenceDate?: string;
       };
 
+      // Fetch event before deletion to get caldavUUID for sync
+      const event = await this.eventService.getById(req.params.id, userId);
+      if (!event) {
+        res.status(404).json({ error: "Event not found" });
+        return;
+      }
+
       // If mode is specified, use deleteRecurring
       if (mode) {
         const result = await this.eventService.deleteRecurring(
           req.params.id,
-          req.user!.userId,
+          userId,
           mode,
           occurrenceDate,
         );
 
-        // For 'all' mode or when event was completely deleted, return 204
-        if (result === null && mode === "all") {
-          res.status(204).send();
-          return;
-        }
-
-        // For 'single' or 'future' modes, return updated event
+        // Event was updated (single/future mode) - push update to CalDAV
         if (result) {
+          await this.pushToCaldav(userId, result);
           res.json(result);
           return;
         }
 
-        // result is null but mode wasn't 'all' - event not found or was deleted
+        // Event was fully deleted (all mode, or future from first occurrence)
+        await this.deleteFromCaldav(userId, event);
         res.status(204).send();
         return;
       }
 
       // Default behavior: delete completely
-      const deleted = await this.eventService.delete(
-        req.params.id,
-        req.user!.userId,
-      );
-      if (!deleted) {
-        res.status(404).json({ error: "Event not found" });
-        return;
-      }
+      await this.eventService.delete(req.params.id, userId);
+      await this.deleteFromCaldav(userId, event);
       res.status(204).send();
     } catch (error) {
-      log.error({ error, eventId: req.params.id }, "Error deleting event");
+      log.error({ err: error, eventId: req.params.id }, "Error deleting event");
       res.status(500).json({ error: "Failed to delete event" });
     }
   }

apps/server/src/controllers/index.ts

@@ -3,3 +3,4 @@ export * from "./ChatController";
 export * from "./EventController";
 export * from "./AuthMiddleware";
 export * from "./LoggingMiddleware";
+export * from "./CaldavController";

apps/server/src/logging/Logged.ts

@@ -4,7 +4,7 @@ import { createLogger } from "./logger";
  * Summarize args for logging to avoid huge log entries.
  * - Arrays: show length only
  * - Long strings: truncate
- * - Objects with conversationHistory/existingEvents: summarize
+ * - Objects with conversationHistory: summarize
  */
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 function summarizeArgs(args: any[]): any[] {
@@ -31,8 +31,6 @@ function summarizeValue(value: any, depth = 0): any {
     for (const [key, val] of Object.entries(value)) {
       if (key === "conversationHistory" && Array.isArray(val)) {
         summarized[key] = `[${val.length} messages]`;
-      } else if (key === "existingEvents" && Array.isArray(val)) {
-        summarized[key] = `[${val.length} events]`;
       } else if (key === "proposedChanges" && Array.isArray(val)) {
         // Log full proposedChanges for debugging AI issues
         summarized[key] = val.map((p) => summarizeValue(p, depth + 1));

apps/server/src/repositories/mongo/MongoCaldavRepository.ts

@@ -0,0 +1,31 @@
+import { CaldavConfig } from "@calchat/shared";
+import { Logged } from "../../logging/Logged";
+import { CaldavRepository } from "../../services/interfaces/CaldavRepository";
+import { CaldavConfigModel } from "./models/CaldavConfigModel";
+
+@Logged("MongoCaldavRepository")
+export class MongoCaldavRepository implements CaldavRepository {
+  async findByUserId(userId: string): Promise<CaldavConfig | null> {
+    const config = await CaldavConfigModel.findOne({ userId });
+    if (!config) return null;
+    return config.toJSON() as unknown as CaldavConfig;
+  }
+
+  async createOrUpdate(config: CaldavConfig): Promise<CaldavConfig> {
+    const caldavConfig = await CaldavConfigModel.findOneAndUpdate(
+      { userId: config.userId },
+      config,
+      {
+        upsert: true,
+        new: true,
+      },
+    );
+    // NOTE: Casting required because Mongoose's toJSON() type doesn't reflect our virtual 'id' field
+    return caldavConfig.toJSON() as unknown as CaldavConfig;
+  }
+
+  async deleteByUserId(userId: string): Promise<boolean> {
+    const result = await CaldavConfigModel.findOneAndDelete({ userId });
+    return result !== null;
+  }
+}

apps/server/src/repositories/mongo/MongoChatRepository.ts

@@ -5,6 +5,7 @@ import {
   CreateEventDTO,
   GetMessagesOptions,
   UpdateMessageDTO,
+  ConflictingEvent,
 } from "@calchat/shared";
 import { ChatRepository } from "../../services/interfaces";
 import { Logged } from "../../logging";
@@ -25,12 +26,20 @@ export class MongoChatRepository implements ChatRepository {
     return conversation.toJSON() as unknown as Conversation;
   }
 
+  async getConversationById(
+    conversationId: string,
+  ): Promise<Conversation | null> {
+    const conversation = await ConversationModel.findById(conversationId);
+    return conversation
+      ? (conversation.toJSON() as unknown as Conversation)
+      : null;
+  }
+
   // Messages (cursor-based pagination)
   async getMessages(
     conversationId: string,
     options?: GetMessagesOptions,
   ): Promise<ChatMessage[]> {
-    const limit = options?.limit ?? 20;
     const query: Record<string, unknown> = { conversationId };
 
     // Cursor: load messages before this ID (for "load more" scrolling up)
@@ -39,9 +48,12 @@ export class MongoChatRepository implements ChatRepository {
     }
 
     // Fetch newest first, then reverse for chronological order
-    const docs = await ChatMessageModel.find(query)
-      .sort({ _id: -1 })
-      .limit(limit);
+    // Only apply limit if explicitly specified (no default - load all messages)
+    let queryBuilder = ChatMessageModel.find(query).sort({ _id: -1 });
+    if (options?.limit) {
+      queryBuilder = queryBuilder.limit(options.limit);
+    }
+    const docs = await queryBuilder;
 
     return docs.reverse().map((doc) => doc.toJSON() as unknown as ChatMessage);
   }
@@ -88,12 +100,28 @@ export class MongoChatRepository implements ChatRepository {
     messageId: string,
     proposalId: string,
     event: CreateEventDTO,
+    conflictingEvents?: ConflictingEvent[],
   ): Promise<ChatMessage | null> {
+    // Always set both fields - use empty array when no conflicts
+    // (MongoDB has issues combining $set and $unset on positional operator)
+    const setFields: Record<string, unknown> = {
+      "proposedChanges.$.event": event,
+      "proposedChanges.$.conflictingEvents":
+        conflictingEvents && conflictingEvents.length > 0
+          ? conflictingEvents
+          : [],
+    };
+
     const doc = await ChatMessageModel.findOneAndUpdate(
       { _id: messageId, "proposedChanges.id": proposalId },
-      { $set: { "proposedChanges.$.event": event } },
+      { $set: setFields },
       { new: true },
     );
     return doc ? (doc.toJSON() as unknown as ChatMessage) : null;
   }
+
+  async getMessageById(messageId: string): Promise<ChatMessage | null> {
+    const doc = await ChatMessageModel.findById(messageId);
+    return doc ? (doc.toJSON() as unknown as ChatMessage) : null;
+  }
 }

apps/server/src/repositories/mongo/MongoEventRepository.ts

@@ -28,6 +28,23 @@ export class MongoEventRepository implements EventRepository {
     return events.map((e) => e.toJSON() as unknown as CalendarEvent);
   }
 
+  async findByCaldavUUID(
+    userId: string,
+    caldavUUID: string,
+  ): Promise<CalendarEvent | null> {
+    const event = await EventModel.findOne({ userId, caldavUUID });
+    if (!event) return null;
+    return event.toJSON() as unknown as CalendarEvent;
+  }
+
+  async searchByTitle(userId: string, query: string): Promise<CalendarEvent[]> {
+    const events = await EventModel.find({
+      userId,
+      title: { $regex: query, $options: "i" },
+    }).sort({ startTime: 1 });
+    return events.map((e) => e.toJSON() as unknown as CalendarEvent);
+  }
+
   async create(userId: string, data: CreateEventDTO): Promise<CalendarEvent> {
     const event = await EventModel.create({ userId, ...data });
     // NOTE: Casting required because Mongoose's toJSON() type doesn't reflect our virtual 'id' field

apps/server/src/repositories/mongo/models/CaldavConfigModel.ts

@@ -0,0 +1,22 @@
+import { CaldavConfig } from "@calchat/shared";
+import mongoose, { Document, Schema } from "mongoose";
+
+export interface CaldavConfigDocument extends CaldavConfig, Document {
+  toJSON(): CaldavConfig;
+}
+
+const CaldavConfigSchema = new Schema<CaldavConfigDocument>(
+  {
+    userId: { type: String, required: true, index: true },
+    serverUrl: { type: String, required: true },
+    username: { type: String, required: true },
+    password: { type: String, required: true },
+    syncIntervalSeconds: { type: Number },
+  },
+  { _id: false },
+);
+
+export const CaldavConfigModel = mongoose.model<CaldavConfigDocument>(
+  "CaldavConfig",
+  CaldavConfigSchema,
+);

apps/server/src/repositories/mongo/models/ChatModel.ts

@@ -5,6 +5,7 @@ import {
   CreateEventDTO,
   UpdateEventDTO,
   ProposedEventChange,
+  ConflictingEvent,
 } from "@calchat/shared";
 import { IdVirtual } from "./types";
 
@@ -41,6 +42,15 @@ const UpdatesSchema = new Schema<UpdateEventDTO>(
   { _id: false },
 );
 
+const ConflictingEventSchema = new Schema<ConflictingEvent>(
+  {
+    title: { type: String, required: true },
+    startTime: { type: Date, required: true },
+    endTime: { type: Date, required: true },
+  },
+  { _id: false },
+);
+
 const ProposedChangeSchema = new Schema<ProposedEventChange>(
   {
     id: { type: String, required: true },
@@ -61,6 +71,7 @@ const ProposedChangeSchema = new Schema<ProposedEventChange>(
       enum: ["single", "future", "all"],
     },
     occurrenceDate: { type: String },
+    conflictingEvents: { type: [ConflictingEventSchema] },
   },
   { _id: false },
 );

apps/server/src/repositories/mongo/models/EventModel.ts

@@ -2,22 +2,16 @@ import mongoose, { Schema, Document, Model } from "mongoose";
 import { CalendarEvent } from "@calchat/shared";
 import { IdVirtual } from "./types";
 
-interface EventVirtuals extends IdVirtual {
-  isRecurring: boolean;
-}
-
-export interface EventDocument
-  extends Omit<CalendarEvent, "id" | "isRecurring">,
-    Document {
+export interface EventDocument extends Omit<CalendarEvent, "id">, Document {
   toJSON(): CalendarEvent;
 }
 
 const EventSchema = new Schema<
   EventDocument,
-  Model<EventDocument, {}, {}, EventVirtuals>,
+  Model<EventDocument, {}, {}, IdVirtual>,
   {},
   {},
-  EventVirtuals
+  IdVirtual
 >(
   {
     userId: {
@@ -25,6 +19,12 @@ const EventSchema = new Schema<
       required: true,
       index: true,
     },
+    caldavUUID: {
+      type: String,
+    },
+    etag: {
+      type: String,
+    },
     title: {
       type: String,
       required: true,
@@ -61,11 +61,6 @@ const EventSchema = new Schema<
           return this._id.toString();
         },
       },
-      isRecurring: {
-        get() {
-          return !!this.recurrenceRule;
-        },
-      },
     },
     toJSON: {
       virtuals: true,

apps/server/src/routes/auth.routes.ts

@@ -6,8 +6,6 @@ export function createAuthRoutes(authController: AuthController): Router {
 
   router.post("/login", (req, res) => authController.login(req, res));
   router.post("/register", (req, res) => authController.register(req, res));
-  router.post("/refresh", (req, res) => authController.refresh(req, res));
-  router.post("/logout", (req, res) => authController.logout(req, res));
 
   return router;
 }

apps/server/src/routes/caldav.routes.ts

@@ -0,0 +1,22 @@
+import { Router } from "express";
+import { authenticate } from "../controllers";
+import { CaldavController } from "../controllers/CaldavController";
+
+export function createCaldavRoutes(caldavController: CaldavController): Router {
+  const router = Router();
+
+  router.use(authenticate);
+
+  router.put("/config", (req, res) => caldavController.saveConfig(req, res));
+  router.get("/config", (req, res) => caldavController.loadConfig(req, res));
+  router.delete("/config", (req, res) =>
+    caldavController.deleteConfig(req, res),
+  );
+  router.post("/pull", (req, res) => caldavController.pullEvents(req, res));
+  router.post("/pushAll", (req, res) => caldavController.pushEvents(req, res));
+  router.post("/push/:caldavUUID", (req, res) =>
+    caldavController.pushEvent(req, res),
+  );
+
+  return router;
+}

apps/server/src/routes/index.ts

@@ -6,12 +6,15 @@ import {
   AuthController,
   ChatController,
   EventController,
+  CaldavController,
 } from "../controllers";
+import { createCaldavRoutes } from "./caldav.routes";
 
 export interface Controllers {
   authController: AuthController;
   chatController: ChatController;
   eventController: EventController;
+  caldavController: CaldavController;
 }
 
 export function createRoutes(controllers: Controllers): Router {
@@ -20,6 +23,7 @@ export function createRoutes(controllers: Controllers): Router {
   router.use("/auth", createAuthRoutes(controllers.authController));
   router.use("/chat", createChatRoutes(controllers.chatController));
   router.use("/events", createEventRoutes(controllers.eventController));
+  router.use("/caldav", createCaldavRoutes(controllers.caldavController));
 
   return router;
 }

apps/server/src/services/AuthService.ts

@@ -1,6 +1,5 @@
-import { User, CreateUserDTO, LoginDTO, AuthResponse } from "@calchat/shared";
+import { CreateUserDTO, LoginDTO, AuthResponse } from "@calchat/shared";
 import { UserRepository } from "./interfaces";
-import * as jwt from "../utils/jwt";
 import * as password from "../utils/password";
 
 export class AuthService {
@@ -45,12 +44,4 @@ export class AuthService {
 
     return { user, accessToken: "" };
   }
-
-  async refreshToken(refreshToken: string): Promise<AuthResponse> {
-    throw new Error("Not implemented");
-  }
-
-  async logout(userId: string): Promise<void> {
-    throw new Error("Not implemented");
-  }
 }

apps/server/src/services/CaldavService.ts

@@ -0,0 +1,271 @@
+import crypto from "crypto";
+import { DAVClient } from "tsdav";
+import ICAL from "ical.js";
+import { createLogger } from "../logging/logger";
+import { CaldavRepository } from "./interfaces/CaldavRepository";
+import {
+  CalendarEvent,
+  CreateEventDTO,
+  CaldavConfig,
+  formatDateKey,
+} from "@calchat/shared";
+import { EventService } from "./EventService";
+
+const logger = createLogger("CaldavService");
+
+export class CaldavService {
+  constructor(
+    private caldavRepo: CaldavRepository,
+    private eventService: EventService,
+  ) {}
+
+  /**
+   * Login to CalDAV server and return client + first calendar.
+   */
+  async connect(userId: string) {
+    const config = await this.caldavRepo.findByUserId(userId);
+    if (config === null) {
+      throw new Error(`Coudn't find config by user id ${userId}`);
+    }
+    const client = new DAVClient({
+      serverUrl: config.serverUrl,
+      credentials: {
+        username: config.username,
+        password: config.password,
+      },
+      authMethod: "Basic",
+      defaultAccountType: "caldav",
+    });
+
+    try {
+      await client.login();
+    } catch (error) {
+      throw new Error("Caldav login failed");
+    }
+
+    const calendars = await client.fetchCalendars();
+    if (calendars.length === 0) {
+      throw new Error("No calendars found on CalDAV server");
+    }
+
+    return { client, calendar: calendars[0] };
+  }
+
+  /**
+   * Pull events from CalDAV server and sync with local database.
+   * - Compares etags to skip unchanged events
+   * - Creates new or updates existing events in the database
+   * - Deletes local events that were removed on the CalDAV server
+   *
+   * @returns List of newly created or updated events
+   */
+  async pullEvents(userId: string): Promise<CalendarEvent[]> {
+    const { client, calendar } = await this.connect(userId);
+    const calendarEvents: CalendarEvent[] = [];
+    const caldavEventUUIDs = new Set<string>();
+
+    const events = await client.fetchCalendarObjects({ calendar });
+    for (const event of events) {
+      const etag = event.etag;
+      const jcal = ICAL.parse(event.data);
+      const comp = new ICAL.Component(jcal);
+      // A CalendarObject (.ics file) can contain multiple VEVENTs (e.g.
+      // recurring events with RECURRENCE-ID exceptions), but the etag belongs
+      // to the whole file, not individual VEVENTs. We only need the first
+      // VEVENT since we handle recurrence via RRULE/exceptionDates, not as
+      // separate events.
+      const vevent = comp.getFirstSubcomponent("vevent");
+      if (!vevent) continue;
+
+      const icalEvent = new ICAL.Event(vevent);
+      caldavEventUUIDs.add(icalEvent.uid);
+
+      const exceptionDates = vevent
+        .getAllProperties("exdate")
+        .flatMap((prop) => prop.getValues())
+        .map((time: ICAL.Time) => formatDateKey(time.toJSDate()));
+
+      const existingEvent = await this.eventService.findByCaldavUUID(
+        userId,
+        icalEvent.uid,
+      );
+
+      const didChange = existingEvent?.etag !== etag;
+
+      if (existingEvent && !didChange) {
+        continue;
+      }
+
+      const eventObject: CreateEventDTO = {
+        caldavUUID: icalEvent.uid,
+        etag,
+        title: icalEvent.summary,
+        description: icalEvent.description,
+        startTime: icalEvent.startDate.toJSDate(),
+        endTime: icalEvent.endDate.toJSDate(),
+        recurrenceRule: vevent.getFirstPropertyValue("rrule")?.toString(),
+        exceptionDates,
+        caldavSyncStatus: "synced",
+      };
+
+      const calendarEvent = existingEvent
+        ? await this.eventService.update(existingEvent.id, userId, eventObject)
+        : await this.eventService.create(userId, eventObject);
+
+      if (calendarEvent) {
+        calendarEvents.push(calendarEvent);
+      }
+    }
+
+    // delete all events, that got deleted remotely
+    const localEvents = await this.eventService.getAll(userId);
+    for (const localEvent of localEvents) {
+      if (
+        localEvent.caldavUUID &&
+        !caldavEventUUIDs.has(localEvent.caldavUUID)
+      ) {
+        await this.eventService.delete(localEvent.id, userId);
+      }
+    }
+
+    return calendarEvents;
+  }
+
+  /**
+   * Push a single event to the CalDAV server.
+   * Creates a new event if no caldavUUID exists, updates otherwise.
+   */
+  async pushEvent(userId: string, event: CalendarEvent): Promise<void> {
+    const { client, calendar } = await this.connect(userId);
+
+    try {
+      if (event.caldavUUID) {
+        await client.updateCalendarObject({
+          calendarObject: {
+            url: `${calendar.url}${event.caldavUUID}.ics`,
+            data: this.toICalString(event.caldavUUID, event),
+            etag: event.etag || "",
+          },
+        });
+      } else {
+        const uid = crypto.randomUUID();
+        await client.createCalendarObject({
+          calendar,
+          filename: `${uid}.ics`,
+          iCalString: this.toICalString(uid, event),
+        });
+        await this.eventService.update(event.id, userId, { caldavUUID: uid });
+      }
+
+      // Fetch updated etag from server
+      const objects = await client.fetchCalendarObjects({ calendar });
+      const caldavUUID =
+        event.caldavUUID ||
+        (await this.eventService.getById(event.id, userId))?.caldavUUID;
+      const pushed = objects.find((o) => o.data?.includes(caldavUUID!));
+
+      await this.eventService.update(event.id, userId, {
+        etag: pushed?.etag || undefined,
+        caldavSyncStatus: "synced",
+      });
+    } catch (error) {
+      await this.eventService.update(event.id, userId, {
+        caldavSyncStatus: "error",
+      });
+      throw error;
+    }
+  }
+
+  /**
+   * Build an iCalendar string from a CalendarEvent using ical.js.
+   */
+  private toICalString(uid: string, event: CalendarEvent): string {
+    const vcalendar = new ICAL.Component("vcalendar");
+    vcalendar.addPropertyWithValue("version", "2.0");
+    vcalendar.addPropertyWithValue("prodid", "-//CalChat//EN");
+
+    const vevent = new ICAL.Component("vevent");
+    vevent.addPropertyWithValue("uid", uid);
+    vevent.addPropertyWithValue("summary", event.title);
+    vevent.addPropertyWithValue(
+      "dtstart",
+      ICAL.Time.fromJSDate(new Date(event.startTime)),
+    );
+    vevent.addPropertyWithValue(
+      "dtend",
+      ICAL.Time.fromJSDate(new Date(event.endTime)),
+    );
+
+    if (event.description) {
+      vevent.addPropertyWithValue("description", event.description);
+    }
+
+    if (event.recurrenceRule) {
+      // Strip RRULE: prefix if present — fromString expects only the value part,
+      // and addPropertyWithValue("rrule", ...) adds the RRULE: prefix automatically.
+      const rule = event.recurrenceRule.replace(/^RRULE:/i, "");
+      vevent.addPropertyWithValue("rrule", ICAL.Recur.fromString(rule));
+    }
+
+    if (event.exceptionDates?.length) {
+      for (const exdate of event.exceptionDates) {
+        vevent.addPropertyWithValue("exdate", ICAL.Time.fromDateString(exdate));
+      }
+    }
+
+    vcalendar.addSubcomponent(vevent);
+    return vcalendar.toString();
+  }
+
+  async pushAll(userId: string): Promise<void> {
+    const allEvents = await this.eventService.getAll(userId);
+    for (const event of allEvents) {
+      if (event.caldavSyncStatus !== "synced") {
+        await this.pushEvent(userId, event);
+      }
+    }
+  }
+
+  async deleteEvent(userId: string, caldavUUID: string) {
+    const { client, calendar } = await this.connect(userId);
+
+    await client.deleteCalendarObject({
+      calendarObject: {
+        url: `${calendar.url}${caldavUUID}.ics`,
+      },
+    });
+  }
+
+  async findEventByCaldavUUID(userId: string, caldavUUID: string) {
+    return this.eventService.findByCaldavUUID(userId, caldavUUID);
+  }
+
+  async getConfig(userId: string): Promise<CaldavConfig | null> {
+    return this.caldavRepo.findByUserId(userId);
+  }
+
+  async saveConfig(config: CaldavConfig): Promise<CaldavConfig> {
+    const savedConfig = await this.caldavRepo.createOrUpdate(config);
+    try {
+      await this.connect(savedConfig.userId);
+    } catch (error) {
+      await this.caldavRepo.deleteByUserId(savedConfig.userId);
+      throw new Error("failed to connect");
+    }
+    return savedConfig;
+  }
+
+  async deleteConfig(userId: string) {
+    return await this.caldavRepo.deleteByUserId(userId);
+  }
+
+  /**
+   * Sync with CalDAV server if config exists. Silent no-op if no config.
+   */
+  async sync(userId: string): Promise<void> {
+    const config = await this.getConfig(userId);
+    if (!config) return;
+    await this.pushAll(userId);
+    await this.pullEvents(userId);
+  }
+}

apps/server/src/services/ChatService.ts

@@ -9,10 +9,10 @@ import {
   CreateEventDTO,
   UpdateEventDTO,
   EventAction,
-  CreateMessageDTO,
   RecurringDeleteMode,
+  ConflictingEvent,
 } from "@calchat/shared";
-import { ChatRepository, EventRepository, AIProvider } from "./interfaces";
+import { ChatRepository, AIProvider } from "./interfaces";
 import { EventService } from "./EventService";
 import { getWeeksOverview, getMonthOverview } from "../utils/eventFormatters";
 
@@ -333,7 +333,7 @@ const staticResponses: TestResponse[] = [
 
 async function getTestResponse(
   index: number,
-  eventRepo: EventRepository,
+  eventService: EventService,
   userId: string,
 ): Promise<TestResponse> {
   const responseIdx = index % staticResponses.length;
@@ -341,7 +341,7 @@ async function getTestResponse(
   // === SPORT TEST SCENARIO (Dynamic responses) ===
   // Response 1: Add exception to "Sport" (2 weeks later)
   if (responseIdx === 1) {
-    const events = await eventRepo.findByUserId(userId);
+    const events = await eventService.getAll(userId);
     const sportEvent = events.find((e) => e.title === "Sport");
     if (sportEvent) {
       // Calculate date 2 weeks from the first occurrence
@@ -362,9 +362,7 @@ async function getTestResponse(
             event: {
               title: sportEvent.title,
               startTime: exceptionDate,
-              endTime: new Date(
-                exceptionDate.getTime() + 90 * 60 * 1000,
-              ), // +90 min
+              endTime: new Date(exceptionDate.getTime() + 90 * 60 * 1000), // +90 min
               description: sportEvent.description,
               recurrenceRule: sportEvent.recurrenceRule,
               exceptionDates: sportEvent.exceptionDates,
@@ -374,25 +372,26 @@ async function getTestResponse(
       };
     }
     return {
-      content: "Ich konnte keinen Termin 'Sport' finden. Bitte erstelle ihn zuerst.",
+      content:
+        "Ich konnte keinen Termin 'Sport' finden. Bitte erstelle ihn zuerst.",
     };
   }
 
   // Response 2: Add UNTIL to "Sport" (after 6 weeks total)
   if (responseIdx === 2) {
-    const events = await eventRepo.findByUserId(userId);
+    const events = await eventService.getAll(userId);
     const sportEvent = events.find((e) => e.title === "Sport");
     if (sportEvent) {
       // Calculate UNTIL date: 6 weeks from start
       const untilDate = new Date(sportEvent.startTime);
       untilDate.setDate(untilDate.getDate() + 42); // 6 weeks
-      const untilStr = untilDate.toISOString().replace(/[-:]/g, "").split(".")[0] + "Z";
+      const untilStr =
+        untilDate.toISOString().replace(/[-:]/g, "").split(".")[0] + "Z";
 
       const newRule = `FREQ=WEEKLY;BYDAY=WE;UNTIL=${untilStr}`;
 
       return {
-        content:
-          "Alles klar! Ich beende die Sport-Serie nach 6 Wochen:",
+        content: "Alles klar! Ich beende die Sport-Serie nach 6 Wochen:",
         proposedChanges: [
           {
             id: "sport-until",
@@ -412,13 +411,14 @@ async function getTestResponse(
       };
     }
     return {
-      content: "Ich konnte keinen Termin 'Sport' finden. Bitte erstelle ihn zuerst.",
+      content:
+        "Ich konnte keinen Termin 'Sport' finden. Bitte erstelle ihn zuerst.",
     };
   }
 
   // Response 3: Add another exception to "Sport" (2 weeks after the first exception)
   if (responseIdx === 3) {
-    const events = await eventRepo.findByUserId(userId);
+    const events = await eventService.getAll(userId);
     const sportEvent = events.find((e) => e.title === "Sport");
     if (sportEvent) {
       // Calculate date 4 weeks from the first occurrence (2 weeks after the first exception)
@@ -439,9 +439,7 @@ async function getTestResponse(
             event: {
               title: sportEvent.title,
               startTime: exceptionDate,
-              endTime: new Date(
-                exceptionDate.getTime() + 90 * 60 * 1000,
-              ), // +90 min
+              endTime: new Date(exceptionDate.getTime() + 90 * 60 * 1000), // +90 min
               description: sportEvent.description,
               recurrenceRule: sportEvent.recurrenceRule,
               exceptionDates: sportEvent.exceptionDates,
@@ -451,19 +449,20 @@ async function getTestResponse(
       };
     }
     return {
-      content: "Ich konnte keinen Termin 'Sport' finden. Bitte erstelle ihn zuerst.",
+      content:
+        "Ich konnte keinen Termin 'Sport' finden. Bitte erstelle ihn zuerst.",
     };
   }
 
   // Dynamic responses: fetch events from DB and format
   // (Note: indices shifted by +3 due to new sport responses)
   if (responseIdx === 6) {
-    return { content: await getWeeksOverview(eventRepo, userId, 2) };
+    return { content: await getWeeksOverview(eventService, userId, 2) };
   }
 
   if (responseIdx === 7) {
     // Delete "Meeting mit Jens"
-    const events = await eventRepo.findByUserId(userId);
+    const events = await eventService.getAll(userId);
     const jensEvent = events.find((e) => e.title === "Meeting mit Jens");
     if (jensEvent) {
       return {
@@ -487,12 +486,12 @@ async function getTestResponse(
   }
 
   if (responseIdx === 11) {
-    return { content: await getWeeksOverview(eventRepo, userId, 1) };
+    return { content: await getWeeksOverview(eventService, userId, 1) };
   }
 
   if (responseIdx === 13) {
     // Update "Telefonat mit Mama" +3 days and change time to 13:00
-    const events = await eventRepo.findByUserId(userId);
+    const events = await eventService.getAll(userId);
     const mamaEvent = events.find((e) => e.title === "Telefonat mit Mama");
     if (mamaEvent) {
       const newStart = new Date(mamaEvent.startTime);
@@ -527,7 +526,7 @@ async function getTestResponse(
     const now = new Date();
     return {
       content: await getMonthOverview(
-        eventRepo,
+        eventService,
         userId,
         now.getFullYear(),
         now.getMonth(),
@@ -541,7 +540,6 @@ async function getTestResponse(
 export class ChatService {
   constructor(
     private chatRepo: ChatRepository,
-    private eventRepo: EventRepository,
     private eventService: EventService,
     private aiProvider: AIProvider,
   ) {}
@@ -566,11 +564,14 @@ export class ChatService {
 
     if (process.env.USE_TEST_RESPONSES === "true") {
       // Test mode: use static responses
-      response = await getTestResponse(responseIndex, this.eventRepo, userId);
+      response = await getTestResponse(
+        responseIndex,
+        this.eventService,
+        userId,
+      );
       responseIndex++;
     } else {
       // Production mode: use real AI
-      const events = await this.eventRepo.findByUserId(userId);
       const history = await this.chatRepo.getMessages(conversationId, {
         limit: 20,
       });
@@ -578,8 +579,16 @@ export class ChatService {
       response = await this.aiProvider.processMessage(data.content, {
         userId,
         conversationHistory: history,
-        existingEvents: events,
         currentDate: new Date(),
+        fetchEventsInRange: async (start, end) => {
+          return this.eventService.getByDateRange(userId, start, end);
+        },
+        searchEvents: async (query) => {
+          return this.eventService.searchByTitle(userId, query);
+        },
+        fetchEventById: async (eventId) => {
+          return this.eventService.getById(eventId, userId);
+        },
       });
     }
 
@@ -616,10 +625,14 @@ export class ChatService {
     let content: string;
 
     if (action === "create" && event) {
-      const createdEvent = await this.eventRepo.create(userId, event);
+      const createdEvent = await this.eventService.create(userId, event);
       content = `Der Termin "${createdEvent.title}" wurde erstellt.`;
     } else if (action === "update" && eventId && updates) {
-      const updatedEvent = await this.eventRepo.update(eventId, updates);
+      const updatedEvent = await this.eventService.update(
+        eventId,
+        userId,
+        updates,
+      );
       content = updatedEvent
         ? `Der Termin "${updatedEvent.title}" wurde aktualisiert.`
         : "Termin nicht gefunden.";
@@ -713,6 +726,56 @@ export class ChatService {
     proposalId: string,
     event: CreateEventDTO,
   ): Promise<ChatMessage | null> {
-    return this.chatRepo.updateProposalEvent(messageId, proposalId, event);
+    // Get the message to find the conversation
+    const message = await this.chatRepo.getMessageById(messageId);
+    if (!message) {
+      return null;
+    }
+
+    // Get the conversation to find the userId
+    const conversation = await this.chatRepo.getConversationById(
+      message.conversationId,
+    );
+    if (!conversation) {
+      return null;
+    }
+    const userId = conversation.userId;
+
+    // Get event times
+    const eventStart = new Date(event.startTime);
+    const eventEnd = new Date(event.endTime);
+
+    // Get day range for conflict checking
+    const dayStart = new Date(eventStart);
+    dayStart.setHours(0, 0, 0, 0);
+    const dayEnd = new Date(dayStart);
+    dayEnd.setDate(dayStart.getDate() + 1);
+
+    // Fetch events for the day
+    const dayEvents = await this.eventService.getByDateRange(
+      userId,
+      dayStart,
+      dayEnd,
+    );
+
+    // Check for time overlaps (use occurrenceStart/End for expanded recurring events)
+    const conflicts: ConflictingEvent[] = dayEvents
+      .filter(
+        (e) =>
+          new Date(e.occurrenceStart) < eventEnd &&
+          new Date(e.occurrenceEnd) > eventStart,
+      )
+      .map((e) => ({
+        title: e.title,
+        startTime: new Date(e.occurrenceStart),
+        endTime: new Date(e.occurrenceEnd),
+      }));
+
+    return this.chatRepo.updateProposalEvent(
+      messageId,
+      proposalId,
+      event,
+      conflicts.length > 0 ? conflicts : undefined,
+    );
   }
 }

apps/server/src/services/EventService.ts

@@ -24,10 +24,21 @@ export class EventService {
     return event;
   }
 
+  async findByCaldavUUID(
+    userId: string,
+    caldavUUID: string,
+  ): Promise<CalendarEvent | null> {
+    return this.eventRepo.findByCaldavUUID(userId, caldavUUID);
+  }
+
   async getAll(userId: string): Promise<CalendarEvent[]> {
     return this.eventRepo.findByUserId(userId);
   }
 
+  async searchByTitle(userId: string, query: string): Promise<CalendarEvent[]> {
+    return this.eventRepo.searchByTitle(userId, query);
+  }
+
   async getByDateRange(
     userId: string,
     startDate: Date,
@@ -37,8 +48,8 @@ export class EventService {
     const allEvents = await this.eventRepo.findByUserId(userId);
 
     // Separate recurring and non-recurring events
-    const recurringEvents = allEvents.filter((e) => e.isRecurring);
-    const nonRecurringEvents = allEvents.filter((e) => !e.isRecurring);
+    const recurringEvents = allEvents.filter((e) => e.recurrenceRule);
+    const nonRecurringEvents = allEvents.filter((e) => !e.recurrenceRule);
 
     // Expand all events (recurring get multiple instances, non-recurring stay as-is)
     const expanded = expandRecurringEvents(
@@ -90,7 +101,7 @@ export class EventService {
     }
 
     // For non-recurring events, always delete completely
-    if (!event.isRecurring || !event.recurrenceRule) {
+    if (!event.recurrenceRule) {
       await this.eventRepo.delete(id);
       return null;
     }

apps/server/src/services/interfaces/AIProvider.ts

@@ -1,14 +1,24 @@
 import {
-  CalendarEvent,
   ChatMessage,
   ProposedEventChange,
+  ExpandedEvent,
+  CalendarEvent,
 } from "@calchat/shared";
 
 export interface AIContext {
   userId: string;
   conversationHistory: ChatMessage[];
-  existingEvents: CalendarEvent[];
   currentDate: Date;
+  // Callback to load events from a specific date range
+  // Returns ExpandedEvent[] with occurrenceStart/occurrenceEnd for recurring events
+  fetchEventsInRange: (
+    startDate: Date,
+    endDate: Date,
+  ) => Promise<ExpandedEvent[]>;
+  // Callback to search events by title
+  searchEvents: (query: string) => Promise<CalendarEvent[]>;
+  // Callback to fetch a single event by ID
+  fetchEventById: (eventId: string) => Promise<CalendarEvent | null>;
 }
 
 export interface AIResponse {

apps/server/src/services/interfaces/CaldavRepository.ts

@@ -0,0 +1,7 @@
+import { CaldavConfig } from "@calchat/shared";
+
+export interface CaldavRepository {
+  findByUserId(userId: string): Promise<CaldavConfig | null>;
+  createOrUpdate(config: CaldavConfig): Promise<CaldavConfig>;
+  deleteByUserId(userId: string): Promise<boolean>;
+}

apps/server/src/services/interfaces/ChatRepository.ts

@@ -5,11 +5,13 @@ import {
   CreateEventDTO,
   GetMessagesOptions,
   UpdateMessageDTO,
+  ConflictingEvent,
 } from "@calchat/shared";
 
 export interface ChatRepository {
   // Conversations
   getConversationsByUser(userId: string): Promise<Conversation[]>;
+  getConversationById(conversationId: string): Promise<Conversation | null>;
   createConversation(userId: string): Promise<Conversation>;
 
   // Messages (cursor-based pagination)
@@ -38,5 +40,8 @@ export interface ChatRepository {
     messageId: string,
     proposalId: string,
     event: CreateEventDTO,
+    conflictingEvents?: ConflictingEvent[],
   ): Promise<ChatMessage | null>;
+
+  getMessageById(messageId: string): Promise<ChatMessage | null>;
 }

apps/server/src/services/interfaces/EventRepository.ts

@@ -8,6 +8,11 @@ export interface EventRepository {
     startDate: Date,
     endDate: Date,
   ): Promise<CalendarEvent[]>;
+  findByCaldavUUID(
+    userId: string,
+    caldavUUID: string,
+  ): Promise<CalendarEvent | null>;
+  searchByTitle(userId: string, query: string): Promise<CalendarEvent[]>;
   create(userId: string, data: CreateEventDTO): Promise<CalendarEvent>;
   update(id: string, data: UpdateEventDTO): Promise<CalendarEvent | null>;
   delete(id: string): Promise<boolean>;

apps/server/src/utils/eventFormatters.ts

@@ -6,7 +6,7 @@ import {
   MONTH_TO_GERMAN,
   ExpandedEvent,
 } from "@calchat/shared";
-import { EventRepository } from "../services/interfaces";
+import { EventService } from "../services/EventService";
 import { expandRecurringEvents } from "./recurrenceExpander";
 
 // Private formatting helpers
@@ -107,13 +107,13 @@ function formatMonthText(events: ExpandedEvent[], monthName: string): string {
  * Recurring events are expanded to show all occurrences within the range.
  */
 export async function getWeeksOverview(
-  eventRepo: EventRepository,
+  eventService: EventService,
   userId: string,
   weeks: number,
 ): Promise<string> {
   const now = new Date();
   const endDate = new Date(now.getTime() + weeks * 7 * 24 * 60 * 60 * 1000);
-  const events = await eventRepo.findByUserId(userId);
+  const events = await eventService.getAll(userId);
   const expanded = expandRecurringEvents(events, now, endDate);
   return formatWeeksText(expanded, weeks);
 }
@@ -123,14 +123,14 @@ export async function getWeeksOverview(
  * Recurring events are expanded to show all occurrences within the month.
  */
 export async function getMonthOverview(
-  eventRepo: EventRepository,
+  eventService: EventService,
   userId: string,
   year: number,
   month: number,
 ): Promise<string> {
   const startOfMonth = new Date(year, month, 1);
   const endOfMonth = new Date(year, month + 1, 0, 23, 59, 59);
-  const events = await eventRepo.findByUserId(userId);
+  const events = await eventService.getAll(userId);
   const expanded = expandRecurringEvents(events, startOfMonth, endOfMonth);
   const monthName = MONTH_TO_GERMAN[MONTHS[month]];
   return formatMonthText(expanded, monthName);

apps/server/src/utils/index.ts

@@ -1,2 +1 @@
-export * from "./jwt";
 export * from "./password";

apps/server/src/utils/jwt.ts

@@ -1,26 +0,0 @@
-import jwt from "jsonwebtoken";
-
-export interface TokenPayload {
-  userId: string;
-  email: string;
-}
-
-export interface JWTConfig {
-  secret: string;
-  expiresIn: string;
-}
-
-const JWT_SECRET = process.env.JWT_SECRET || "your-secret-key";
-const JWT_EXPIRES_IN = process.env.JWT_EXPIRES_IN || "1h";
-
-export function signToken(payload: TokenPayload): string {
-  throw new Error("Not implemented");
-}
-
-export function verifyToken(token: string): TokenPayload {
-  throw new Error("Not implemented");
-}
-
-export function decodeToken(token: string): TokenPayload | null {
-  throw new Error("Not implemented");
-}

apps/server/src/utils/password.test.ts

@@ -0,0 +1,37 @@
+import { hash, compare } from "./password";
+
+describe("password", () => {
+  describe("hash()", () => {
+    it("returns a valid bcrypt hash", async () => {
+      const result = await hash("testpassword");
+      expect(result).toMatch(/^\$2b\$/);
+    });
+
+    it("produces different hashes for the same password (salt)", async () => {
+      const hash1 = await hash("samepassword");
+      const hash2 = await hash("samepassword");
+      expect(hash1).not.toBe(hash2);
+    });
+  });
+
+  describe("compare()", () => {
+    it("returns true for the correct password", async () => {
+      const hashed = await hash("correct");
+      const result = await compare("correct", hashed);
+      expect(result).toBe(true);
+    });
+
+    it("returns false for a wrong password", async () => {
+      const hashed = await hash("correct");
+      const result = await compare("wrong", hashed);
+      expect(result).toBe(false);
+    });
+
+    it("handles special characters and unicode", async () => {
+      const password = "p@$$w0rd!#%& äöü 🔑";
+      const hashed = await hash(password);
+      expect(await compare(password, hashed)).toBe(true);
+      expect(await compare("other", hashed)).toBe(false);
+    });
+  });
+});

apps/server/src/utils/recurrenceExpander.test.ts

@@ -0,0 +1,210 @@
+import { CalendarEvent } from "@calchat/shared";
+import { expandRecurringEvents } from "./recurrenceExpander";
+
+// Helper: create a CalendarEvent with sensible defaults
+function makeEvent(
+  overrides: Partial<CalendarEvent> & { startTime: Date; endTime: Date },
+): CalendarEvent {
+  return {
+    id: "evt-1",
+    userId: "user-1",
+    title: "Test Event",
+    ...overrides,
+  };
+}
+
+// Helper: create a date from "YYYY-MM-DD HH:mm" (local time)
+function d(dateStr: string): Date {
+  const [datePart, timePart] = dateStr.split(" ");
+  const [y, m, day] = datePart.split("-").map(Number);
+  if (timePart) {
+    const [h, min] = timePart.split(":").map(Number);
+    return new Date(y, m - 1, day, h, min);
+  }
+  return new Date(y, m - 1, day);
+}
+
+describe("expandRecurringEvents", () => {
+  // Range: 2025-06-01 to 2025-06-30
+  const rangeStart = d("2025-06-01 00:00");
+  const rangeEnd = d("2025-06-30 23:59");
+
+  describe("non-recurring events", () => {
+    it("returns event within the range", () => {
+      const event = makeEvent({
+        startTime: d("2025-06-10 09:00"),
+        endTime: d("2025-06-10 10:00"),
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      expect(result).toHaveLength(1);
+      expect(result[0].occurrenceStart).toEqual(d("2025-06-10 09:00"));
+      expect(result[0].occurrenceEnd).toEqual(d("2025-06-10 10:00"));
+    });
+
+    it("excludes event outside the range", () => {
+      const event = makeEvent({
+        startTime: d("2025-07-05 09:00"),
+        endTime: d("2025-07-05 10:00"),
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      expect(result).toHaveLength(0);
+    });
+
+    it("includes event that starts before range and ends within", () => {
+      const event = makeEvent({
+        startTime: d("2025-05-31 22:00"),
+        endTime: d("2025-06-01 02:00"),
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      expect(result).toHaveLength(1);
+    });
+
+    it("includes event that spans the entire range", () => {
+      const event = makeEvent({
+        startTime: d("2025-05-01 00:00"),
+        endTime: d("2025-07-31 23:59"),
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      expect(result).toHaveLength(1);
+    });
+
+    it("returns empty array for empty input", () => {
+      const result = expandRecurringEvents([], rangeStart, rangeEnd);
+
+      expect(result).toEqual([]);
+    });
+  });
+
+  describe("recurring events", () => {
+    it("expands weekly event to all occurrences in range", () => {
+      // Weekly on Mondays, starting 2025-06-02 (a Monday)
+      const event = makeEvent({
+        startTime: d("2025-06-02 10:00"),
+        endTime: d("2025-06-02 11:00"),
+        recurrenceRule: "FREQ=WEEKLY;BYDAY=MO",
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      // Mondays in June 2025: 2, 9, 16, 23, 30
+      expect(result).toHaveLength(5);
+      expect(result[0].occurrenceStart).toEqual(d("2025-06-02 10:00"));
+      expect(result[1].occurrenceStart).toEqual(d("2025-06-09 10:00"));
+      expect(result[2].occurrenceStart).toEqual(d("2025-06-16 10:00"));
+      expect(result[3].occurrenceStart).toEqual(d("2025-06-23 10:00"));
+      expect(result[4].occurrenceStart).toEqual(d("2025-06-30 10:00"));
+    });
+
+    it("daily event with UNTIL stops at the right date", () => {
+      const event = makeEvent({
+        startTime: d("2025-06-01 08:00"),
+        endTime: d("2025-06-01 09:00"),
+        recurrenceRule: "FREQ=DAILY;UNTIL=20250605T235959",
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      // June 1, 2, 3, 4, 5
+      expect(result).toHaveLength(5);
+      expect(result[4].occurrenceStart).toEqual(d("2025-06-05 08:00"));
+    });
+
+    it("skips occurrences on exception dates (EXDATE)", () => {
+      const event = makeEvent({
+        startTime: d("2025-06-02 10:00"),
+        endTime: d("2025-06-02 11:00"),
+        recurrenceRule: "FREQ=WEEKLY;BYDAY=MO",
+        exceptionDates: ["2025-06-09", "2025-06-23"],
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      // 5 Mondays minus 2 exceptions = 3
+      expect(result).toHaveLength(3);
+      const dates = result.map((r) => r.occurrenceStart.getDate());
+      expect(dates).toEqual([2, 16, 30]);
+    });
+
+    it("handles RRULE: prefix (strips it)", () => {
+      const event = makeEvent({
+        startTime: d("2025-06-01 08:00"),
+        endTime: d("2025-06-01 09:00"),
+        recurrenceRule: "RRULE:FREQ=DAILY;COUNT=3",
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      expect(result).toHaveLength(3);
+    });
+
+    it("falls back to single occurrence on invalid RRULE", () => {
+      const consoleSpy = jest.spyOn(console, "error").mockImplementation();
+
+      const event = makeEvent({
+        startTime: d("2025-06-10 09:00"),
+        endTime: d("2025-06-10 10:00"),
+        recurrenceRule: "COMPLETELY_INVALID_RULE",
+      });
+
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      expect(result).toHaveLength(1);
+      expect(result[0].occurrenceStart).toEqual(d("2025-06-10 09:00"));
+      expect(consoleSpy).toHaveBeenCalled();
+
+      consoleSpy.mockRestore();
+    });
+  });
+
+  describe("multi-day events", () => {
+    it("finds event starting before range that ends within range", () => {
+      // 3-day recurring event starting May 15, weekly
+      const event = makeEvent({
+        startTime: d("2025-05-15 08:00"),
+        endTime: d("2025-05-18 08:00"),
+        recurrenceRule: "FREQ=WEEKLY",
+      });
+
+      // The occurrence starting May 29 ends June 1 → overlaps with range
+      const result = expandRecurringEvents([event], rangeStart, rangeEnd);
+
+      const starts = result.map((r) => r.occurrenceStart.getDate());
+      // May 29 (ends June 1), June 5, 12, 19, 26
+      expect(starts).toContain(29); // May 29
+    });
+  });
+
+  describe("sorting", () => {
+    it("returns events sorted by occurrenceStart", () => {
+      const laterEvent = makeEvent({
+        id: "evt-later",
+        startTime: d("2025-06-20 14:00"),
+        endTime: d("2025-06-20 15:00"),
+      });
+      const earlierEvent = makeEvent({
+        id: "evt-earlier",
+        startTime: d("2025-06-05 09:00"),
+        endTime: d("2025-06-05 10:00"),
+      });
+
+      // Pass in reverse order
+      const result = expandRecurringEvents(
+        [laterEvent, earlierEvent],
+        rangeStart,
+        rangeEnd,
+      );
+
+      expect(result).toHaveLength(2);
+      expect(result[0].id).toBe("evt-earlier");
+      expect(result[1].id).toBe("evt-later");
+    });
+  });
+});

apps/server/src/utils/recurrenceExpander.ts

@@ -1,5 +1,5 @@
 import { RRule, rrulestr } from "rrule";
-import { CalendarEvent, ExpandedEvent } from "@calchat/shared";
+import { CalendarEvent, ExpandedEvent, formatDateKey } from "@calchat/shared";
 
 // Convert local time to "fake UTC" for rrule
 // rrule interprets all dates as UTC internally, so we need to trick it
@@ -48,7 +48,7 @@ export function expandRecurringEvents(
     // to find events that start before rangeStart but extend into the range
     const adjustedRangeStart = new Date(rangeStart.getTime() - duration);
 
-    if (!event.isRecurring || !event.recurrenceRule) {
+    if (!event.recurrenceRule) {
       // Non-recurring event: add if it overlaps with the range
       if (endTime >= rangeStart && startTime <= rangeEnd) {
         expanded.push({
@@ -133,11 +133,3 @@ function formatRRuleDateString(date: Date): string {
   const seconds = String(date.getSeconds()).padStart(2, "0");
   return `${year}${month}${day}T${hours}${minutes}${seconds}`;
 }
-
-// Format date as YYYY-MM-DD for exception date comparison
-function formatDateKey(date: Date): string {
-  const year = date.getFullYear();
-  const month = String(date.getMonth() + 1).padStart(2, "0");
-  const day = String(date.getDate()).padStart(2, "0");
-  return `${year}-${month}-${day}`;
-}

apps/server/tsconfig.json

@@ -8,7 +8,8 @@
     "esModuleInterop": true,
     "forceConsistentCasingInFileNames": true,
     "experimentalDecorators": true,
-    "emitDecoratorMetadata": true
+    "emitDecoratorMetadata": true,
+    "skipLibCheck": true
   },
   "include": ["src"]
 }

docs/api-routes.md

@@ -11,15 +11,13 @@ Base URL: `/api`
 |--------|----------|--------------|
 | POST | `/auth/login` | User Login |
 | POST | `/auth/register` | User Registrierung |
-| POST | `/auth/refresh` | JWT Token erneuern |
-| POST | `/auth/logout` | User Logout |
 
 ---
 
 ## Events
 
 ### Event Endpoints (`/api/events`)
-Alle Endpoints erfordern JWT-Authentifizierung.
+Alle Endpoints erfordern Authentifizierung (X-User-Id Header).
 
 | Method | Endpoint | Beschreibung |
 |--------|----------|--------------|
@@ -35,7 +33,7 @@ Alle Endpoints erfordern JWT-Authentifizierung.
 ## Chat
 
 ### Chat Endpoints (`/api/chat`)
-Alle Endpoints erfordern JWT-Authentifizierung.
+Alle Endpoints erfordern Authentifizierung (X-User-Id Header).
 
 | Method | Endpoint | Beschreibung |
 |--------|----------|--------------|

docs/architecture-class-diagram.puml

@@ -30,6 +30,8 @@ package "Controller Layer" #ADD8E6 {
     }
 
     class EventController {
+        ' -pushToCaldav()
+        ' -deleteFromCaldav()
         ' +create()
         ' +getById()
         ' +getAll()
@@ -38,6 +40,15 @@ package "Controller Layer" #ADD8E6 {
         ' +delete()
     }
 
+    class CaldavController {
+        ' +saveConfig()
+        ' +loadConfig()
+        ' +deleteConfig()
+        ' +pullEvents()
+        ' +pushEvents()
+        ' +pushEvent()
+    }
+
     class AuthMiddleware {
         ' +authenticate()
     }
@@ -59,9 +70,12 @@ package "Service Layer" #90EE90 {
             ' +findById()
             ' +findByUserId()
             ' +findByDateRange()
+            ' +findByCaldavUUID()
+            ' +searchByTitle()
             ' +create()
             ' +update()
             ' +delete()
+            ' +addExceptionDate()
         }
 
         interface ChatRepository {
@@ -69,6 +83,14 @@ package "Service Layer" #90EE90 {
             ' +createConversation()
             ' +getMessages()
             ' +createMessage()
+            ' +updateProposalResponse()
+            ' +updateProposalEvent()
+        }
+
+        interface CaldavRepository {
+            ' +findByUserId()
+            ' +createOrUpdate()
+            ' +deleteByUserId()
         }
     }
 
@@ -80,7 +102,7 @@ package "Service Layer" #90EE90 {
 
     class ChatService {
         ' -chatRepo: ChatRepository
-        ' -eventRepo: EventRepository
+        ' -eventService: EventService
         ' -aiProvider: AIProvider
         ' +processMessage()
         ' +confirmEvent()
@@ -95,13 +117,29 @@ package "Service Layer" #90EE90 {
         ' +getById()
         ' +getAll()
         ' +getByDateRange()
+        ' +searchByTitle()
+        ' +findByCaldavUUID()
         ' +update()
         ' +delete()
+        ' +deleteRecurring()
+    }
+
+    class CaldavService {
+        ' -caldavRepo: CaldavRepository
+        ' -eventService: EventService
+        ' +connect()
+        ' +pullEvents()
+        ' +pushEvent()
+        ' +pushAll()
+        ' +deleteEvent()
+        ' +getConfig()
+        ' +saveConfig()
+        ' +deleteConfig()
     }
 }
 
 package "AI Implementations" #FFA07A {
-    class ClaudeAdapter implements AIProvider {
+    class GPTAdapter implements AIProvider {
         ' -apiKey: string
         ' +processMessage()
     }
@@ -119,6 +157,10 @@ package "Data Access Implementations" #FFD700 {
     class MongoChatRepository implements ChatRepository {
         ' -model: ChatModel
     }
+
+    class MongoCaldavRepository implements CaldavRepository {
+        ' -model: CaldavConfigModel
+    }
 }
 
 package "Models" #D3D3D3 {
@@ -146,11 +188,6 @@ package "Models" #D3D3D3 {
 }
 
 package "Utils" #DDA0DD {
-    class JWT {
-        ' +signToken()
-        ' +verifyToken()
-    }
-
     class Password {
         ' +hash()
         ' +compare()
@@ -169,18 +206,20 @@ package "Utils" #DDA0DD {
 ' Controller -> Service
 AuthController --> AuthService
 ChatController --> ChatService
+ChatController --> CaldavService
 EventController --> EventService
-AuthMiddleware --> JWT
-
+EventController --> CaldavService
+CaldavController --> CaldavService
 ' Service -> Interfaces (intern)
 AuthService --> UserRepository
 ChatService --> ChatRepository
-ChatService --> EventRepository
+ChatService --> EventService
 ChatService --> AIProvider
 EventService --> EventRepository
+CaldavService --> CaldavRepository
+CaldavService --> EventService
 
 ' Auth uses Utils
-AuthService --> JWT
 AuthService --> Password
 
 ' Event/Chat uses Utils

docs/component-diagram.puml

@@ -16,6 +16,8 @@ package "apps/client (Expo React Native)" as ClientPkg #87CEEB {
         [Login/Register] as AuthScreens
         [Calendar View] as CalendarScreen
         [Chat View] as ChatScreen
+        [Settings] as SettingsScreen
+        [Edit Event] as EditEventScreen
         [Event Detail] as EventDetail
         [Note Editor] as NoteScreen
     }
@@ -25,17 +27,20 @@ package "apps/client (Expo React Native)" as ClientPkg #87CEEB {
         [Auth Service] as ClientAuth
         [Event Service] as ClientEvent
         [Chat Service] as ClientChat
+        [Caldav Config Service] as ClientCaldav
     }
 
     package "Components" {
         [UI Components] as UIComponents
         [Event Cards] as EventCards
+        [Auth Guard] as AuthGuard
     }
 
     package "Stores" {
         [Auth Store] as AuthStore
         [Events Store] as EventsStore
         [Chat Store] as ChatStore
+        [Theme Store] as ThemeStore
     }
 }
 
@@ -59,10 +64,11 @@ package "apps/server (Express.js)" as ServerPkg #98FB98 {
         [AuthService] as AuthSvc
         [ChatService] as ChatSvc
         [EventService] as EventSvc
+        [CaldavService] as CaldavSvc
     }
 
     package "AI Implementations" {
-        [ClaudeAdapter] as Claude
+        [GPTAdapter] as GPT
     }
 
     package "Data Access Implementations" {
@@ -71,7 +77,6 @@ package "apps/server (Express.js)" as ServerPkg #98FB98 {
     }
 
     package "Utils" {
-        [JWT] as JWTUtil
         [Password] as PwdUtil
         [RecurrenceExpander] as RecExpander
         [EventFormatters] as EvtFormatters
@@ -80,25 +85,35 @@ package "apps/server (Express.js)" as ServerPkg #98FB98 {
 
 ' ===== ROW 4: EXTERNAL =====
 database "MongoDB" as MongoDB
-cloud "Claude API" as ClaudeAPI
+cloud "OpenAI API" as OpenAIAPI
+cloud "CalDAV Server" as CaldavServer
 
 ' ===== CONNECTIONS =====
 
 ' Frontend: Screens -> Services
 AuthScreens --> ClientAuth
 CalendarScreen --> ClientEvent
+CalendarScreen --> ClientCaldav
 ChatScreen --> ClientChat
+SettingsScreen --> ClientCaldav
+EditEventScreen --> ClientEvent
 EventDetail --> ClientEvent
 NoteScreen --> ClientEvent
 
 ClientAuth --> ApiClient
 ClientEvent --> ApiClient
 ClientChat --> ApiClient
+ClientCaldav --> ApiClient
 
 ApiClient --> AuthStore
 ClientEvent --> EventsStore
 ClientChat --> ChatStore
 
+' Frontend: Auth
+AuthGuard --> AuthStore
+AuthGuard --> ClientCaldav
+AuthScreens --> ClientCaldav
+
 ' Frontend: Screens -> Components
 CalendarScreen --> EventCards
 ChatScreen --> EventCards
@@ -121,20 +136,24 @@ Routes --> Controllers
 Controllers --> AuthSvc
 Controllers --> ChatSvc
 Controllers --> EventSvc
+Controllers --> CaldavSvc
 
 ' Backend: Service -> Interfaces
 AuthSvc --> Interfaces
 ChatSvc --> Interfaces
 EventSvc --> Interfaces
+CaldavSvc --> Interfaces
+
+' Backend: Service dependencies
+ChatSvc --> EventSvc
+CaldavSvc --> EventSvc
 
 ' Backend: AI & Data Access implement Interfaces
-Claude ..|> Interfaces
+GPT ..|> Interfaces
 Repos ..|> Interfaces
 
 ' Backend: Service -> Utils
-AuthSvc --> JWTUtil
 AuthSvc --> PwdUtil
-Middleware --> JWTUtil
 EventSvc --> RecExpander
 ChatSvc --> EvtFormatters
 
@@ -143,6 +162,7 @@ Repos --> Schemas
 
 ' Backend -> External
 Schemas --> MongoDB
-Claude --> ClaudeAPI
+GPT --> OpenAIAPI
+CaldavSvc --> CaldavServer
 
 @enduml

docs/frontend-class-diagram.puml

@@ -12,58 +12,73 @@ skinparam wrapWidth 100
 skinparam nodesep 30
 skinparam ranksep 30
 
-top to bottom direction
+left to right direction
 
 title Frontend (Expo React Native)
 
+' ===== COMPONENTS =====
+package "Components" #FFA07A  {
+    class AuthGuard
+    class BaseBackground
+    class Header
+    class BaseButton
+    class CardBase
+    class ModalBase
+    class EventCardBase
+    class EventCard
+    class ProposedEventCard
+    class DeleteEventModal
+    class ChatBubble
+    class TypingIndicator
+}
+
 ' ===== SCREENS =====
 package "Screens" #87CEEB {
     class LoginScreen
     class RegisterScreen
     class CalendarScreen
     class ChatScreen
+    class SettingsScreen
+    class EditEventScreen
     class EventDetailScreen
     class NoteScreen
 }
 
-' ===== COMPONENTS =====
-package "Components" #FFA07A  {
-    class BaseBackground
-    class Header
-    class EventCardBase
-    class EventCard
-    class ProposedEventCard
-    class EventConfirmDialog
-}
-
 ' ===== SERVICES =====
 package "Services" #90EE90 {
     class ApiClient {
-        +get()
-        +post()
-        +put()
-        +delete()
+        ' +get()
+        ' +post()
+        ' +put()
+        ' +delete()
     }
     class AuthService {
-        +login()
-        +register()
-        +logout()
-        +refresh()
+        ' +login()
+        ' +register()
+        ' +logout()
+        ' +refresh()
     }
     class EventService {
-        +getAll()
-        +getById()
-        +getByDateRange()
-        +create()
-        +update()
-        +delete()
+        ' +getAll()
+        ' +getById()
+        ' +getByDateRange()
+        ' +create()
+        ' +update()
+        ' +delete()
     }
     class ChatService {
-        +sendMessage()
-        +confirmEvent()
-        +rejectEvent()
-        +getConversations()
-        +getConversation()
+        ' +sendMessage()
+        ' +confirmEvent()
+        ' +rejectEvent()
+        ' +getConversations()
+        ' +getConversation()
+        ' +updateProposalEvent()
+    }
+    class CaldavConfigService {
+        ' +getConfig()
+        ' +saveConfig()
+        ' +deleteConfig()
+        ' +sync()
     }
 }
 
@@ -71,11 +86,10 @@ package "Services" #90EE90 {
 package "Stores" #FFD700 {
     class AuthStore {
         ' +user
-        ' +token
         ' +isAuthenticated
         ' +login()
         ' +logout()
-        ' +setToken()
+        ' +loadStoredUser()
     }
     class EventsStore {
         ' +events
@@ -86,10 +100,16 @@ package "Stores" #FFD700 {
     }
     class ChatStore {
         ' +messages
+        ' +isWaitingForResponse
         ' +addMessage()
+        ' +addMessages()
         ' +updateMessage()
         ' +clearMessages()
     }
+    class ThemeStore {
+        ' +theme
+        ' +setTheme()
+    }
 }
 
 ' ===== MODELS =====
@@ -97,31 +117,47 @@ package "Models (shared)" #D3D3D3 {
     class User
     class CalendarEvent
     class ChatMessage
+    class CaldavConfig
 }
 
 ' ===== RELATIONSHIPS =====
 
-' Screens -> Services
-LoginScreen --> AuthService
-CalendarScreen --> EventService
-ChatScreen --> ChatService
-NoteScreen --> EventService
-
 ' Screens -> Components
 CalendarScreen --> EventCard
 ChatScreen --> ProposedEventCard
-ChatScreen --> EventConfirmDialog
+ChatScreen --> ChatBubble
+ChatScreen --> TypingIndicator
 EventCard --> EventCardBase
 ProposedEventCard --> EventCardBase
+EventCardBase --> CardBase
+ModalBase --> CardBase
+DeleteEventModal --> ModalBase
+
+' Screens -> Services
+LoginScreen --> AuthService
+CalendarScreen --> EventService
+CalendarScreen --> CaldavConfigService
+ChatScreen --> ChatService
+NoteScreen --> EventService
+EditEventScreen --> EventService
+EditEventScreen --> ChatService
+SettingsScreen --> CaldavConfigService
+
+' Auth
+AuthGuard --> AuthStore
+AuthGuard --> CaldavConfigService
+LoginScreen --> CaldavConfigService
 
 ' Services -> ApiClient
 AuthService --> ApiClient
 EventService --> ApiClient
 ChatService --> ApiClient
+CaldavConfigService --> ApiClient
 
 ' Services/Screens -> Stores
 AuthService --> AuthStore
-EventService --> EventsStore
+CalendarScreen --> EventsStore
 ChatScreen --> ChatStore
+SettingsScreen --> ThemeStore
 
 @enduml

docs/technisches_brainstorm.tex

@@ -66,7 +66,7 @@ Backend & Express.js & Web-App Framework \\
         & MongoDB & Datenbank \\
         & Mongoose & ODM \\
         & Claude (Anthropic) & KI / LLM \\
-        & JWT & Authentifizierung \\
+        & X-User-Id Header & Authentifizierung \\
 \hline
 Geplant & iCalendar & Event-Export \\
 \hline
@@ -112,8 +112,9 @@ Der wichtigste Teil der App ist die KI-Integration über \textbf{Claude}
 (Anthropic). Dieses LLM verarbeitet natürlichsprachliche Eingaben der Nutzer und
 generiert daraus strukturierte Event-Vorschläge.
 
-Die Authentifizierung läuft über \textbf{JSON Web Tokens} (JWT). Der Vorteil:
-zustandslose Sessions, bei denen der Server keine Session-Daten speichern muss.
+Die Authentifizierung erfolgt über einen \textbf{X-User-Id Header}, der bei
+jedem Request die User-ID mitschickt. Diese einfache Lösung reicht für den
+aktuellen Entwicklungsstand aus.
 
 Geplant ist außerdem die Unterstützung des \textbf{iCalendar}-Formats (ICAL)
 für den Export von Kalender-Events.
@@ -157,7 +158,7 @@ Notiz-Feld) und ChatMessage.
 Der Controller Layer bildet die Schnittstelle zwischen Frontend und
 Backend-Logik. Die Routes definieren die API-Endpunkte, die Controller
 verarbeiten die eingehenden Requests und reichen diese an die Services weiter.
-Eine Auth Middleware prüft bei geschützten Routen den JWT-Token.
+Eine Auth Middleware prüft bei geschützten Routen den X-User-Id Header.
 
 \subsubsection{Service Layer}
 

package.json

@@ -7,7 +7,8 @@
     "packages/*"
   ],
   "scripts": {
-    "format": "prettier --write \"apps/*/src/**/*.{ts,tsx}\" \"packages/*/src/**/*.ts\""
+    "format": "prettier --write \"apps/*/src/**/*.{ts,tsx}\" \"packages/*/src/**/*.ts\"",
+    "check_format": "prettier --check \"apps/*/src/**/*.{ts,tsx}\" \"packages/*/src/**/*.ts\""
   },
   "devDependencies": {
     "eslint": "^9.25.0",

packages/shared/.gitignore

@@ -0,0 +1 @@
+dist/

packages/shared/package.json

@@ -2,11 +2,14 @@
   "name": "@calchat/shared",
   "version": "1.0.0",
   "private": true,
-  "main": "./src/index.ts",
-  "types": "./src/index.ts",
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
   "exports": {
-    ".": "./src/index.ts",
-    "./*": "./src/*"
+    ".": "./dist/index.js",
+    "./*": "./dist/*"
+  },
+  "scripts": {
+    "build": "tsc"
   },
   "dependencies": {
     "rrule": "^2.8.1"

packages/shared/src/models/CaldavConfig.ts

@@ -0,0 +1,7 @@
+export interface CaldavConfig {
+  userId: string;
+  serverUrl: string;
+  username: string;
+  password: string;
+  syncIntervalSeconds?: number;
+}

packages/shared/src/models/CalendarEvent.ts

@@ -1,19 +1,22 @@
 export interface CalendarEvent {
   id: string;
   userId: string;
+  caldavUUID?: string;
+  etag?: string;
   title: string;
   description?: string;
   startTime: Date;
   endTime: Date;
   note?: string;
-  isRecurring?: boolean;
   recurrenceRule?: string;
   exceptionDates?: string[]; // ISO date strings (YYYY-MM-DD) for excluded occurrences
   createdAt?: Date;
   updatedAt?: Date;
+  caldavSyncStatus?: CaldavSyncStatus;
 }
 
 export type RecurringDeleteMode = "single" | "future" | "all";
+export type CaldavSyncStatus = "synced" | "error";
 
 export interface DeleteRecurringEventDTO {
   mode: RecurringDeleteMode;
@@ -21,6 +24,8 @@ export interface DeleteRecurringEventDTO {
 }
 
 export interface CreateEventDTO {
+  caldavUUID?: string;
+  etag?: string;
   title: string;
   description?: string;
   startTime: Date;
@@ -28,9 +33,12 @@ export interface CreateEventDTO {
   note?: string;
   recurrenceRule?: string;
   exceptionDates?: string[]; // For display in proposals
+  caldavSyncStatus?: CaldavSyncStatus;
 }
 
 export interface UpdateEventDTO {
+  caldavUUID?: string;
+  etag?: string;
   title?: string;
   description?: string;
   startTime?: Date;
@@ -38,6 +46,7 @@ export interface UpdateEventDTO {
   note?: string;
   recurrenceRule?: string;
   exceptionDates?: string[];
+  caldavSyncStatus?: CaldavSyncStatus;
 }
 
 export interface ExpandedEvent extends CalendarEvent {

packages/shared/src/models/ChatMessage.ts

@@ -10,6 +10,12 @@ export type EventAction = "create" | "update" | "delete";
 
 export type RespondedAction = "confirm" | "reject";
 
+export interface ConflictingEvent {
+  title: string;
+  startTime: Date;
+  endTime: Date;
+}
+
 export interface ProposedEventChange {
   id: string; // Unique ID for each proposal
   action: EventAction;
@@ -19,6 +25,7 @@ export interface ProposedEventChange {
   respondedAction?: RespondedAction; // User's response to this specific proposal
   deleteMode?: RecurringDeleteMode; // For recurring event deletion
   occurrenceDate?: string; // ISO date string of specific occurrence for single/future delete
+  conflictingEvents?: ConflictingEvent[]; // Overlapping events for conflict warnings
 }
 
 export interface ChatMessage {

packages/shared/src/models/index.ts

@@ -2,3 +2,4 @@ export * from "./User";
 export * from "./CalendarEvent";
 export * from "./ChatMessage";
 export * from "./Constants";
+export * from "./CaldavConfig";

packages/shared/src/utils/formatters.ts

@@ -69,3 +69,11 @@ export function formatDateWithWeekdayShort(date: Date): string {
     month: "2-digit",
   });
 }
+
+// Format date as YYYY-MM-DD for exception date comparison
+export function formatDateKey(date: Date): string {
+  const year = date.getFullYear();
+  const month = String(date.getMonth() + 1).padStart(2, "0");
+  const day = String(date.getDate()).padStart(2, "0");
+  return `${year}-${month}-${day}`;
+}

packages/shared/src/utils/rruleHelpers.ts

@@ -11,6 +11,24 @@ const REPEAT_TYPE_TO_FREQ: Record<RepeatType, string> = {
   Jahr: "YEARLY",
 };
 
+const FREQ_TO_REPEAT_TYPE: Record<string, RepeatType> = Object.fromEntries(
+  Object.entries(REPEAT_TYPE_TO_FREQ).map(([k, v]) => [v, k as RepeatType]),
+);
+
+export const REPEAT_TYPE_LABELS: Record<RepeatType, string> = {
+  Tag: "Tage",
+  Woche: "Wochen",
+  Monat: "Monate",
+  Jahr: "Jahre",
+};
+
+const REPEAT_TYPE_SINGULAR: Record<RepeatType, string> = {
+  Tag: "Jeden Tag",
+  Woche: "Jede Woche",
+  Monat: "Jeden Monat",
+  Jahr: "Jedes Jahr",
+};
+
 /**
  * Build an RRULE string from repeat count and type.
  *
@@ -18,7 +36,10 @@ const REPEAT_TYPE_TO_FREQ: Record<RepeatType, string> = {
  * @param interval - The interval between repetitions (default: 1)
  * @returns RRULE string like "FREQ=WEEKLY;INTERVAL=2"
  */
-export function buildRRule(repeatType: RepeatType, interval: number = 1): string {
+export function buildRRule(
+  repeatType: RepeatType,
+  interval: number = 1,
+): string {
   const freq = REPEAT_TYPE_TO_FREQ[repeatType];
 
   if (interval <= 1) {
@@ -27,3 +48,30 @@ export function buildRRule(repeatType: RepeatType, interval: number = 1): string
 
   return `FREQ=${freq};INTERVAL=${interval}`;
 }
+
+/**
+ * Format an RRULE string into a human-readable German description.
+ *
+ * @param rrule - RRULE string like "FREQ=WEEKLY;INTERVAL=2"
+ * @returns German description like "Alle 2 Wochen" or "Wöchentlich"
+ */
+export function formatRecurrenceRule(rrule: string): string {
+  const rule = rrule.replace(/^RRULE:/, "");
+  const parts = Object.fromEntries(
+    rule.split(";").map((p) => p.split("=") as [string, string]),
+  );
+
+  const freq = parts.FREQ;
+  const interval = parts.INTERVAL ? parseInt(parts.INTERVAL, 10) : 1;
+  const repeatType = FREQ_TO_REPEAT_TYPE[freq];
+
+  if (!repeatType) {
+    return "Wiederkehrend";
+  }
+
+  if (interval <= 1) {
+    return REPEAT_TYPE_SINGULAR[repeatType];
+  }
+
+  return `Alle ${interval} ${REPEAT_TYPE_LABELS[repeatType]}`;
+}

packages/shared/tsconfig.json

@@ -1,10 +1,10 @@
 {
   "extends": "../../tsconfig.json",
   "compilerOptions": {
-    "composite": true,
     "declaration": true,
-    "declarationMap": true,
-    "module": "ESNext",
+    "outDir": "dist",
+    "rootDir": "src",
+    "module": "CommonJS",
     "target": "ES2020",
     "moduleResolution": "Node",
     "esModuleInterop": true,