refactor: improve AI event handling and conflict display in chat

- AI fetches events on-demand via callbacks for better efficiency
- Add conflict detection with warning display when proposing overlapping events
- Improve event search and display in chat interface
- Load full chat history for display while limiting AI context

CLAUDE.md

@@ -266,10 +266,10 @@ src/
 │   ├── 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
@@ -325,10 +325,12 @@ src/
 - `CalendarEvent`: id, userId, title, description?, startTime, endTime, note?, isRecurring?, recurrenceRule?, exceptionDates?
 - `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 +344,39 @@ 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
+
 ### Database Abstraction
 
 The repository pattern allows swapping databases:
@@ -402,7 +437,6 @@ 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)]"`
@@ -474,9 +508,11 @@ 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/`: Provider-agnostic shared utilities (systemPrompt, toolDefinitions, toolExecutor)
-  - `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/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 `isRecurring` and `recurrenceRule` parameters for adding UNTIL or modifying recurrence
+  - `ai/utils/toolDefinitions`: proposeUpdateEvent supports `isRecurring` and `recurrenceRule` parameters, 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
@@ -538,7 +574,7 @@ NODE_ENV=development        # development = pretty logs, production = JSON
 - `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
 - `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
 - `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.)

apps/client/src/app/editEvent.tsx

@@ -22,9 +22,6 @@ import { EventService, ChatService } from "../services";
 import { buildRRule, CreateEventDTO } from "@calchat/shared";
 import { useChatStore } from "../stores";
 
-// Direct store access for getting current state in callbacks
-const getChatStoreState = () => useChatStore.getState();
-
 type EditEventTextFieldProps = {
   titel: string;
   text?: string;
@@ -443,31 +440,25 @@ 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
+        // Persist to server - returns updated message with recalculated conflictingEvents
-        const currentMessages = getChatStoreState().messages;
+        const updatedMessage = await ChatService.updateProposalEvent(
-        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(
           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/components/ProposedEventCard.tsx

@@ -1,6 +1,6 @@
 import { View, Text, Pressable } from "react-native";
-import { Feather } from "@expo/vector-icons";
+import { Feather, Ionicons } from "@expo/vector-icons";
-import { ProposedEventChange, formatDate } from "@calchat/shared";
+import { ProposedEventChange, formatDate, formatTime } from "@calchat/shared";
 import { rrulestr } from "rrule";
 import { useThemeStore } from "../stores/ThemeStore";
 import { EventCardBase } from "./EventCardBase";
@@ -143,6 +143,29 @@ export const ProposedEventCard = ({
             </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/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
+        toolResults.push({ toolCall, content: result.content });
+      }
+
+      // Add assistant message with ALL tool calls at once
       messages.push({
         role: "assistant",
-          tool_calls: [toolCall],
+        tool_calls: assistantMessage.tool_calls,
+        content: assistantMessage.content,
       });
 
-        // Add tool result
+      // 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 +1,4 @@
-import {
+import { formatDate, formatTime, formatDateTime } from "@calchat/shared";
-  CalendarEvent,
-  formatDate,
-  formatTime,
-  formatDateTime,
-} from "@calchat/shared";
 
-// Re-export for backwards compatibility
+// Re-export from shared package for use in toolExecutor
 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 +1,4 @@
-export {
+export { formatDate, formatTime, formatDateTime } from "./eventFormatter";
-  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
+- 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]?"
-- Nutze searchEvents um nach Terminen zu suchen, wenn du die genaue ID brauchst
+- 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:
+WICHTIG - Unterscheide zwischen PROPOSALS und ABFRAGEN:
-${eventsText}`;
+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

@@ -8,6 +8,18 @@ import {
 import { AIContext } from "../../services/interfaces";
 import { formatDate, formatTime, formatDateTime } from "./eventFormatter";
 
+/**
+ * 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(
+      const existingEvent = await context.fetchEventById(eventId);
-        (e) => e.id === 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(
+      const existingEvent = await context.fetchEventById(eventId);
-        (e) => e.id === 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 query = args.query as string;
-      const matches = context.existingEvents.filter((e) =>
+      const matches = await context.searchEvents(query);
-        e.title.toLowerCase().includes(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.startTime);
+          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

@@ -96,8 +96,10 @@ 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/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/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)
+    // Only apply limit if explicitly specified (no default - load all messages)
-      .sort({ _id: -1 })
+    let queryBuilder = ChatMessageModel.find(query).sort({ _id: -1 });
-      .limit(limit);
+    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 +28,14 @@ export class MongoEventRepository implements EventRepository {
     return events.map((e) => e.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/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/services/ChatService.ts

@@ -9,8 +9,8 @@ import {
   CreateEventDTO,
   UpdateEventDTO,
   EventAction,
-  CreateMessageDTO,
   RecurringDeleteMode,
+  ConflictingEvent,
 } from "@calchat/shared";
 import { ChatRepository, EventRepository, AIProvider } from "./interfaces";
 import { EventService } from "./EventService";
@@ -570,7 +570,6 @@ export class ChatService {
       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 +577,16 @@ 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.eventRepo.searchByTitle(userId, query);
+        },
+        fetchEventById: async (eventId) => {
+          return this.eventService.getById(eventId, userId);
+        },
       });
     }
 
@@ -713,6 +720,56 @@ 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/interfaces/AIProvider.ts

@@ -1,14 +1,21 @@
 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/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 +8,7 @@ export interface EventRepository {
     startDate: Date,
     endDate: Date,
   ): Promise<CalendarEvent[]>;
+  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>;

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 {