diff --git a/backend/src/modules/collaboration/federation.ts b/backend/src/modules/collaboration/federation.ts
index c51592ff..27c36511 100644
--- a/backend/src/modules/collaboration/federation.ts
+++ b/backend/src/modules/collaboration/federation.ts
@@ -242,9 +242,11 @@ export class FederationService {
         for (const b of bindings) {
             if (b.status === "pending" && new Date(b.invitation.expiresAt).getTime() > Date.now()) result.invitations.push({ ...b.invitation, id: b.id, remote: true })
             if (b.status === "active") {
-                const [unread] = await rows(this.service.db, sql`SELECT count(*)::int AS count FROM collaboration_remote_messages WHERE binding_id=${b.id} AND seq>${b.last_read_seq} AND (payload->>'own')='false'`)
+                const [unread] = await rows(this.service.db, sql`SELECT count(*)::int AS count,
+                    (SELECT payload->>'createdAt' FROM collaboration_remote_messages WHERE binding_id=${b.id} ORDER BY seq DESC LIMIT 1) AS "lastActivityAt"
+                    FROM collaboration_remote_messages WHERE binding_id=${b.id} AND seq>${b.last_read_seq} AND (payload->>'own')='false'`)
                 result.rooms.push({ id: b.id, name: b.snapshot?.name || b.invitation.name, topic: b.snapshot?.topic || b.invitation.topic,
-                    ownerName: b.invitation.ownerName, status: b.snapshot?.status || 'active', remote: true, unread: unread.count })
+                    ownerName: b.invitation.ownerName, status: b.snapshot?.status || 'active', remote: true, unread: unread.count, lastActivityAt: unread.lastActivityAt || null })
             }
         }
         return result
diff --git a/backend/src/modules/collaboration/service.ts b/backend/src/modules/collaboration/service.ts
index 3c763885..f5ef2118 100644
--- a/backend/src/modules/collaboration/service.ts
+++ b/backend/src/modules/collaboration/service.ts
@@ -144,6 +144,8 @@ export class CollaborationService {
             t.name AS "ownerName", m.overview_allowed AS "overviewAllowed",
             (SELECT count(*)::int FROM collaboration_messages cm WHERE cm.room_id=r.id
              AND cm.seq>=m.history_from_seq AND cm.seq>m.last_read_seq AND cm.principal_id<>${principal.id}) AS unread
+            ,coalesce((SELECT max(cm.created_at) FROM collaboration_messages cm WHERE cm.room_id=r.id
+             AND cm.seq>=m.history_from_seq), r.created_at) AS "lastActivityAt"
             FROM collaboration_members m JOIN collaboration_rooms r ON r.id=m.room_id JOIN tenants t ON t.id=r.tenant_id
             LEFT JOIN projects p ON p.id=r.project_id
             WHERE m.principal_id=${principal.id} AND m.status='active' AND (m.expires_at IS NULL OR m.expires_at>now())
diff --git a/backend/src/routes/communication.ts b/backend/src/routes/communication.ts
index db58e290..12530b54 100644
--- a/backend/src/routes/communication.ts
+++ b/backend/src/routes/communication.ts
@@ -158,6 +158,16 @@ export default async function communicationRoutes(server: FastifyInstance) {
         entityUuid: room.entityUuid,
         exists: true,
     })
+    // Rooms without messages fall back to their creation date so new rooms still sort by recency.
+    const withActivity = async <T extends { room: typeof communicationRooms.$inferSelect }>(rows: T[]) => {
+        const ids = rows.map(({ room }) => room.id)
+        const latest = ids.length ? await server.db.select({
+            roomId: communicationMessages.roomId,
+            at: sql<Date>`max(${communicationMessages.createdAt})`.mapWith(communicationMessages.createdAt),
+        }).from(communicationMessages).where(inArray(communicationMessages.roomId, ids)).groupBy(communicationMessages.roomId) : []
+        const byRoom = new Map(latest.map((row) => [row.roomId, row.at]))
+        return (room: typeof communicationRooms.$inferSelect) => (byRoom.get(room.id) || room.createdAt).toISOString()
+    }
 
     const messagesForRoom = async (roomId: string, currentUserId: string, tenantId: number, afterId = 0, limit = 50) => {
         const conditions = [eq(communicationMessages.roomId, roomId)]
@@ -295,7 +305,8 @@ export default async function communicationRoutes(server: FastifyInstance) {
                 eq(communicationRooms.archived, false),
                 eq(communicationRoomMembers.userId, req.user.user_id)
             )).orderBy(asc(communicationRooms.name))
-        return { rooms: rows.map(({ room }) => roomToApi(room)) }
+        const activity = await withActivity(rows)
+        return { rooms: rows.map(({ room }) => ({ ...roomToApi(room), lastActivityAt: activity(room) })) }
     })
 
     server.post("/communication/chat/rooms", async (req: any, reply) => {
@@ -335,9 +346,10 @@ export default async function communicationRoutes(server: FastifyInstance) {
             projectChatAccess(server.db, req),
         ])
         const roomsByProject = new Map(roomRows.map(({ room }) => [room.entityId, room]))
+        const activity = await withActivity(roomRows)
         return { rooms: projectRows.map((project) => {
             const room = roomsByProject.get(project.id)
-            return room ? { ...roomToApi(room), projectId: project.id, projectNumber: project.projectNumber } : {
+            return room ? { ...roomToApi(room), lastActivityAt: activity(room), projectId: project.id, projectNumber: project.projectNumber } : {
                 key: `project_${project.id}`,
                 name: project.projectNumber ? `${project.projectNumber} · ${project.name}` : project.name,
                 topic: `Projektkommunikation zu ${project.name}`,
@@ -387,11 +399,13 @@ export default async function communicationRoutes(server: FastifyInstance) {
             .innerJoin(communicationRoomMembers, eq(communicationRoomMembers.roomId, communicationRooms.id))
             .where(and(eq(communicationRooms.tenantId, tenantId), eq(communicationRooms.type, "direct"), eq(communicationRoomMembers.userId, req.user.user_id)))
         const roomsByKey = new Map(existingRows.map(({ room }) => [room.key, room]))
+        const activity = await withActivity(existingRows)
         return { rooms: users.map((user) => {
             const key = directRoomKey(req.user.user_id, user.userId)
             const room = roomsByKey.get(key)
             return room ? {
                 ...roomToApi(room),
+                lastActivityAt: activity(room),
                 name: displayName(user),
                 topic: `Direktnachricht mit ${displayName(user)}`,
                 entityUuid: user.userId,
diff --git a/mobile/app/(tabs)/communication.tsx b/mobile/app/(tabs)/communication.tsx
index 15aa34a8..8cce0684 100644
--- a/mobile/app/(tabs)/communication.tsx
+++ b/mobile/app/(tabs)/communication.tsx
@@ -10,7 +10,7 @@ import {
 import { ChatConversation, type ChatDraft } from '@/components/chat-conversation';
 import { apiRequest } from '@/src/lib/api';
 import { chatApi } from '@/src/lib/chat-api';
-import { collaborationKey, isChatAccessError, matchesChatSearch, visibleChatRooms, type ChatDirectory, type MobileChatRoom } from '@/src/lib/chat';
+import { collaborationKey, isChatAccessError, matchesChatSearch, touchChatRoom, visibleChatRooms, type ChatDirectory, type MobileChatRoom } from '@/src/lib/chat';
 import { getApiBaseUrlSync } from '@/src/lib/server-config';
 import { useAuth } from '@/src/providers/auth-provider';
 
@@ -181,7 +181,10 @@ function ChatScreen({ token }: { token: string }) {
       <ChatConversation key={activeRoom.key} token={token} room={activeRoom} enabled={enabled} hiding={!!busy}
         draft={drafts[activeKey] || emptyDraft} onHide={() => void hide(activeRoom, true)}
         onDraft={value => setDrafts(previous => ({ ...previous, [activeKey]: { ...value, clientId: randomUUID() } }))}
-        onSent={clientId => setDrafts(previous => { if (previous[activeKey]?.clientId !== clientId) return previous; const next = { ...previous }; delete next[activeKey]; return next; })} />
+        onSent={clientId => {
+          setDirectory(previous => { const next = previous && { ...previous, rooms: touchChatRoom(previous.rooms, activeRoom.key) }; directoryRef.current = next; return next; });
+          setDrafts(previous => { if (previous[activeKey]?.clientId !== clientId) return previous; const next = { ...previous }; delete next[activeKey]; return next; });
+        }} />
       : <View style={styles.empty}><Ionicons name="chatbubbles-outline" size={36} color="#69c350" /><Text>Wähle einen Chat aus.</Text></View>}
     <Modal transparent visible={showHidden} animationType="slide" onRequestClose={() => setShowHidden(false)}>
       <View style={styles.overlay}><View style={styles.modal}><Text style={styles.title}>Ausgeblendete Chats</Text><Text style={styles.hint}>Diese Einstellung gilt auch im Web.</Text>
diff --git a/mobile/components/chat-conversation.tsx b/mobile/components/chat-conversation.tsx
index 93287bbe..9162de4b 100644
--- a/mobile/components/chat-conversation.tsx
+++ b/mobile/components/chat-conversation.tsx
@@ -1,7 +1,7 @@
 import { Ionicons } from '@expo/vector-icons';
 import { Image } from 'expo-image';
 import * as ImagePicker from 'expo-image-picker';
-import { useCallback, useEffect, useRef, useState } from 'react';
+import { useEffect, useMemo, useRef, useState } from 'react';
 import { ActivityIndicator, FlatList, Modal, Pressable, ScrollView, StyleSheet, Text, TextInput, View } from 'react-native';
 
 import { useChatConversation } from '@/hooks/use-chat-conversation';
@@ -58,7 +58,6 @@ export function ChatConversation({ token, room, enabled, draft, onDraft, onSent,
   const [imageError, setImageError] = useState('');
   const list = useRef<FlatList<MobileChatMessage>>(null);
   const alive = useRef(true);
-  const nearBottom = useRef(true);
   const pickerGeneration = useRef(0);
   const allowed = enabled && !!chat.detail?.canSend && !chat.loading;
   useEffect(() => { alive.current = true; return () => { alive.current = false; }; }, []);
@@ -82,13 +81,13 @@ export function ChatConversation({ token, room, enabled, draft, onDraft, onSent,
   const send = async () => {
     if (!allowed || preparing || (!draft.text.trim() && !draft.image)) return;
     const sent = await chat.send(draft.text.trim(), draft.image, draft.clientId);
-    if (sent) { onSent(draft.clientId); nearBottom.current = true; list.current?.scrollToEnd({ animated: true }); }
+    if (sent) { onSent(draft.clientId); list.current?.scrollToOffset({ offset: 0, animated: true }); }
   };
   const time = (message: MobileChatMessage) => {
     const value = message.createdAt || message.timestamp;
     return value ? new Date(value).toLocaleString('de-DE', { day: '2-digit', month: '2-digit', hour: '2-digit', minute: '2-digit' }) : '';
   };
-  const older = () => { nearBottom.current = false; void chat.older(); };
+  const older = () => void chat.older();
   const renderMessage = ({ item }: { item: MobileChatMessage }) => {
     const canReact = allowed && !chat.detail?.offline && !item.pending && !item.failed;
     return <View style={[styles.messageRow, item.own && styles.ownRow]}>
@@ -110,7 +109,8 @@ export function ChatConversation({ token, room, enabled, draft, onDraft, onSent,
       </View>
     </View>;
   };
-  const scrollToEnd = useCallback(() => { if (nearBottom.current) list.current?.scrollToEnd({ animated: false }); }, []);
+  // The inverted list renders the newest message at the bottom and always opens there.
+  const newestFirst = useMemo(() => [...chat.messages].reverse(), [chat.messages]);
   return <View style={styles.container}>
     <View style={styles.header}>
       <View style={styles.grow}><Text style={styles.title} numberOfLines={1}>{chat.detail?.name || room.name}</Text>
@@ -126,13 +126,11 @@ export function ChatConversation({ token, room, enabled, draft, onDraft, onSent,
       {Object.entries(chat.detail.overview).filter(([, value]) => !!value).map(([key, value]) => <Text key={key}>{key === 'status' ? 'Status: ' : key === 'date' ? 'Termin: ' : ''}{value}</Text>)}
     </View>}
     {chat.loading ? <View style={styles.empty}><ActivityIndicator /><Text>Nachrichten werden geladen …</Text></View> :
-      <FlatList ref={list} data={chat.messages} keyExtractor={item => String(item.id)} renderItem={renderMessage}
+      !chat.messages.length ? <View style={styles.grow}><Text style={[styles.hint, styles.messages]}>Noch keine Nachrichten in diesem Chat.</Text></View> :
+      <FlatList ref={list} inverted data={newestFirst} keyExtractor={item => String(item.id)} renderItem={renderMessage}
         style={styles.grow} contentContainerStyle={styles.messages} keyboardShouldPersistTaps="handled"
-        maintainVisibleContentPosition={{ minIndexForVisible: 0 }}
-        onScroll={event => { const { contentOffset, contentSize, layoutMeasurement } = event.nativeEvent; nearBottom.current = contentSize.height - contentOffset.y - layoutMeasurement.height < 100; }}
-        scrollEventThrottle={100} onContentSizeChange={scrollToEnd}
-        ListHeaderComponent={chat.hasMore ? <Pressable disabled={chat.olderLoading} onPress={older} style={styles.loadOlder}><Text style={styles.link}>{chat.olderLoading ? 'Wird geladen …' : 'Ältere Nachrichten laden'}</Text></Pressable> : null}
-        ListEmptyComponent={<Text style={styles.hint}>Noch keine Nachrichten in diesem Chat.</Text>} />}
+        maintainVisibleContentPosition={{ minIndexForVisible: 1, autoscrollToTopThreshold: 100 }}
+        ListFooterComponent={chat.hasMore ? <Pressable disabled={chat.olderLoading} onPress={older} style={styles.loadOlder}><Text style={styles.link}>{chat.olderLoading ? 'Wird geladen …' : 'Ältere Nachrichten laden'}</Text></Pressable> : null} />}
     {chat.detail && <View style={styles.composer}>
       {!chat.detail.canSend && <Text style={styles.hint}>Dieser Chat ist nur lesbar.</Text>}
       {!!imageError && <Text accessibilityRole="alert" style={styles.error}>{imageError}</Text>}
diff --git a/mobile/src/lib/chat.ts b/mobile/src/lib/chat.ts
index f5c15d8e..96984e58 100644
--- a/mobile/src/lib/chat.ts
+++ b/mobile/src/lib/chat.ts
@@ -6,7 +6,7 @@ export type MobileChatRoom = {
   key: string; id?: string; name: string; topic?: string | null;
   source: 'internal' | 'collaboration'; group: string; exists: boolean;
   type?: string; projectId?: number; projectNumber?: string | null; userId?: string; email?: string | null;
-  ownerName?: string; remote?: boolean; status?: string; unread?: number;
+  ownerName?: string; remote?: boolean; status?: string; unread?: number; lastActivityAt?: string | null;
 };
 export type ChatInvitation = {
   id: string; name: string; ownerName?: string; role: string;
@@ -45,6 +45,11 @@ export const chatEndpoint = (room: MobileChatRoom, suffix = '') => room.source =
   ? `/api/collaboration/rooms/${encodeURIComponent(room.id!)}${suffix}`
   : `/api/communication/chat/rooms/${encodeURIComponent(room.key)}${suffix}`;
 export const visibleChatRooms = (directory: ChatDirectory) => directory.rooms.filter(room => !directory.hiddenRoomKeys.includes(room.key));
+const activity = (room: MobileChatRoom) => (room.lastActivityAt && Date.parse(room.lastActivityAt)) || 0;
+// Most recently used chats first; rooms without activity keep their server order at the end.
+export const sortChatRooms = (rooms: MobileChatRoom[]) => [...rooms].sort((a, b) => activity(b) - activity(a));
+export const touchChatRoom = (rooms: MobileChatRoom[], key: string, at = new Date().toISOString()) =>
+  sortChatRooms(rooms.map(room => room.key === key ? { ...room, lastActivityAt: at } : room));
 export const chatCursor = (room: MobileChatRoom, messages: MobileChatMessage[]) => Math.max(0,
   ...messages.map(message => room.source === 'collaboration' ? message.seq || 0 : Number(message.id)));
 export function mergeChatMessages(current: MobileChatMessage[], incoming: MobileChatMessage[], collaboration: boolean) {
@@ -98,9 +103,9 @@ export function createChatApi(request: Request) {
         ...room, source: 'internal', group, unread: unread.rooms?.[room.key]?.count || 0,
       }));
       return {
-        rooms: [...decorate(base.rooms, 'Räume'), ...decorate(projects.rooms, 'Projekte'), ...decorate(direct.rooms, 'Direkt'),
+        rooms: sortChatRooms([...decorate(base.rooms, 'Räume'), ...decorate(projects.rooms, 'Projekte'), ...decorate(direct.rooms, 'Direkt'),
           ...collaboration.rooms.map(room => ({ ...room, key: collaborationKey(room.id),
-            source: 'collaboration' as const, group: 'Zusammenarbeit', exists: true }))],
+            source: 'collaboration' as const, group: 'Zusammenarbeit', exists: true }))]),
         hiddenRoomKeys: hidden.hiddenRoomKeys, invitations: collaboration.invitations,
         canManage: collaboration.canManage === true, projects: collaboration.projects || [],
       };
diff --git a/mobile/tests/chat.test.mjs b/mobile/tests/chat.test.mjs
index ab137ed9..bf21c3f0 100644
--- a/mobile/tests/chat.test.mjs
+++ b/mobile/tests/chat.test.mjs
@@ -2,7 +2,7 @@ import assert from 'node:assert/strict';
 import { test } from 'node:test';
 import {
   applyChatAccess, chatCursor, chatEndpoint, collaborationKey, createChatApi, matchesChatSearch,
-  mergeChatMessages, validChatImage, visibleChatRooms,
+  mergeChatMessages, sortChatRooms, touchChatRoom, validChatImage, visibleChatRooms,
 } from '../src/lib/chat.ts';
 
 const id = '11111111-1111-4111-8111-111111111111';
@@ -131,3 +131,22 @@ test('Noch nicht angelegte Direkt- und Projektchats werden gezielt provisioniert
   assert.equal(calls[1].path, '/api/communication/chat/direct-rooms/user%2Fid/provision');
   assert.equal(chatEndpoint(remote), `/api/collaboration/rooms/${id}`);
 });
+
+test('Chats werden nach letzter Aktivität sortiert, neue Nachrichten rücken nach oben', () => {
+  const rooms = [
+    { key: 'ohne', name: 'Ohne Aktivität', source: 'internal', exists: false },
+    { key: 'alt', name: 'Alt', source: 'internal', exists: true, lastActivityAt: '2026-01-01T10:00:00.000Z' },
+    { key: 'neu', name: 'Neu', source: 'collaboration', exists: true, lastActivityAt: '2026-03-01T10:00:00.000Z' },
+  ];
+  assert.deepEqual(sortChatRooms(rooms).map(room => room.key), ['neu', 'alt', 'ohne']);
+  assert.deepEqual(touchChatRoom(rooms, 'alt', '2026-04-01T10:00:00.000Z').map(room => room.key), ['alt', 'neu', 'ohne']);
+  assert.equal(rooms[1].lastActivityAt, '2026-01-01T10:00:00.000Z');
+});
+test('Verzeichnis sortiert Räume aller Gruppen gemeinsam nach Aktivität', async () => {
+  const { api } = fixture({
+    '/api/communication/chat/rooms': { rooms: [{ ...internal, lastActivityAt: '2026-01-01T00:00:00.000Z' }] },
+    '/api/collaboration': { rooms: [{ id, name: 'Partner', lastActivityAt: '2026-02-01T00:00:00.000Z' }], invitations: [] },
+  });
+  const result = await api.directory('token');
+  assert.deepEqual(result.rooms.map(room => room.key), [collaborationKey(id), 'allgemein', 'project_42']);
+});