diff --git a/frontend/testserver/index.cjs b/frontend/testserver/index.cjs
index e237df0..8ebe931 100644
--- a/frontend/testserver/index.cjs
+++ b/frontend/testserver/index.cjs
@@ -12,6 +12,44 @@ let draft = null
 let linkedAccount = null
 let mockNotes = []
 const deviceData = {}
+let contactSequence = 2
+const contacts = [
+  {
+    created_at: '2026-08-04 12:00:00',
+    id: 'contact-1',
+    name: 'Jenica Chong',
+    phone_number: '5558675309',
+    updated_at: '2026-08-04 12:00:00',
+  },
+]
+const attachmentAssets = {
+  gif: new Set(['celebrate', 'hearts', 'party', 'thumbs_up', 'wow']),
+  image: new Set([
+    'camera-1', 'camera-2', 'camera-3', 'city-lights', 'desert-road',
+    'ocean-air', 'sunset-drive',
+  ]),
+  video: new Set(['city-loop', 'ocean-loop', 'sunset-loop']),
+}
+const gifMocks = [
+  ['ICOgUNjpvO0PC', 'Cat reaction'],
+  ['MDJ9IbxxvDUQM', 'Happy dog'],
+  ['l0HlPystfePnAI3G8', 'Celebrate'],
+  ['26ufdipQqU2lhNA4g', 'Wow'],
+  ['3o7abKhOpu0NwenH3O', 'Perfect'],
+  ['xT0xeJpnrWC4XWblEk', 'Party'],
+  ['111ebonMs90YLu', 'Thumbs up'],
+  ['5GoVLqeAOo6PK', 'Excited'],
+  ['TdfyKrN7HGTIY', 'Happy dance'],
+  ['14udF3WUwwGMaA', 'Surprised'],
+  ['3o6Zt6ML6BklcajjsA', 'Applause'],
+  ['13CoXDiaCcCoyk', 'Let us go'],
+  ['R6gvnAxj2ISzJdbA63', 'Yes'],
+  ['xUPGcEliCc7bETyfO8', 'Laughing'],
+  ['26BRuo6sLetdllPAQ', 'Dancing'],
+  ['l46CyJmS9KUbokzsI', 'Amazing'],
+  ['g9582DNuQppxC', 'Celebration'],
+  ['artj92V8o75VPL7AeQ', 'High five'],
+]
 const accountDevices = [
   {
     created_at: '2026-08-04 12:00:00',
@@ -75,6 +113,38 @@ const messages = [
     trashed_at: '2026-08-04 08:00:00',
   },
 ]
+const smsMessages = [
+  {
+    body: 'Bin gleich am Würfelpark. Kommst du auch?',
+    created_at: '2026-08-06 13:04:00',
+    direction: 'received',
+    id: 'sms-1',
+    media_duration_ms: null,
+    media_mime: null,
+    media_payload: null,
+    media_waveform: null,
+    message_type: 'text',
+    media_asset_id: null,
+    read_at: null,
+    recipient_number: '5551234567',
+    sender_number: '5558675309',
+  },
+  {
+    body: 'Ja, gib mir fünf Minuten.',
+    created_at: '2026-08-06 13:05:00',
+    direction: 'sent',
+    id: 'sms-2',
+    media_duration_ms: null,
+    media_mime: null,
+    media_payload: null,
+    media_waveform: null,
+    message_type: 'text',
+    media_asset_id: null,
+    read_at: null,
+    recipient_number: '5558675309',
+    sender_number: '5551234567',
+  },
+]
 
 function counts() {
   return {
@@ -114,6 +184,196 @@ app.post('/api/:endpoint', (request, response) => {
     })
     return
   }
+  if (endpoint === 'messages:conversations') {
+    const grouped = new Map()
+    for (const message of [...smsMessages].reverse()) {
+      const phoneNumber =
+        message.direction === 'sent'
+          ? message.recipient_number
+          : message.sender_number
+      const conversation = grouped.get(phoneNumber)
+      if (conversation) {
+        if (message.direction === 'received' && !message.read_at)
+          conversation.unread += 1
+        continue
+      }
+      grouped.set(phoneNumber, {
+        lastMessage: message.body,
+        lastMessageAt: message.created_at,
+        lastMessageType: message.message_type,
+        phoneNumber,
+        unread: message.direction === 'received' && !message.read_at ? 1 : 0,
+      })
+    }
+    response.json({ success: true, data: [...grouped.values()] })
+    return
+  }
+  if (endpoint === 'messages:gifs') {
+    const offset = Math.max(0, Number(request.body.offset ?? 0))
+    const pageSize = 6
+    const results = gifMocks.slice(offset, offset + pageSize).map(([id, title]) => ({
+      height: 200,
+      id,
+      previewUrl: `https://media.giphy.com/media/${id}/200w.gif`,
+      title,
+      url: `https://media.giphy.com/media/${id}/giphy.gif`,
+      width: 200,
+    }))
+    response.json({
+      success: true,
+      data: {
+        hasMore: offset + results.length < gifMocks.length,
+        nextOffset: offset + results.length,
+        results,
+      },
+    })
+    return
+  }
+  if (endpoint === 'messages:thread') {
+    const number = String(request.body.phoneNumber)
+    const thread = smsMessages.filter(
+      (message) =>
+        message.sender_number === number || message.recipient_number === number,
+    )
+    for (const message of thread) {
+      if (message.direction === 'received') message.read_at = message.read_at ?? '2026-08-06 13:06:00'
+    }
+    response.json({
+      success: true,
+      data: thread.map(({ media_payload, ...message }) => ({
+        ...message,
+        media_asset_id: ['image', 'gif', 'video'].includes(message.message_type)
+          ? media_payload
+          : null,
+      })),
+    })
+    return
+  }
+  if (endpoint === 'messages:media') {
+    const message = smsMessages.find(
+      (item) => item.id === request.body.id && item.message_type === 'voice',
+    )
+    response.json(
+      message
+        ? {
+            success: true,
+            data: {
+              mime: message.media_mime,
+              payload: message.media_payload,
+            },
+          }
+        : { success: false, error: 'message_not_found' },
+    )
+    return
+  }
+  if (endpoint === 'messages:send') {
+    const body = String(request.body.body ?? '').trim()
+    const phoneNumber = String(request.body.phoneNumber ?? '')
+    const messageType = request.body.messageType ?? 'text'
+    const isAttachment = ['image', 'gif', 'video'].includes(messageType)
+    const attachmentId = String(request.body.mediaAssetId ?? '')
+    if (
+      !phoneNumber ||
+      (messageType === 'text' && !body) ||
+      (messageType === 'voice' && !request.body.mediaPayload) ||
+      (isAttachment &&
+        !attachmentAssets[messageType].has(attachmentId) &&
+        !attachmentId.startsWith('https://'))
+    ) {
+      response.json({ success: false, error: 'invalid_message' })
+      return
+    }
+    const message = {
+      body,
+      created_at: new Date().toISOString().slice(0, 19).replace('T', ' '),
+      direction: 'sent',
+      id: `sms-${Date.now()}`,
+      media_duration_ms:
+        ['voice', 'video'].includes(messageType)
+          ? request.body.mediaDurationMs ?? null
+          : null,
+      media_mime:
+        messageType === 'voice'
+          ? request.body.mediaMime
+          : messageType === 'image'
+            ? 'image/jpeg'
+            : messageType === 'gif'
+              ? 'image/gif'
+              : messageType === 'video'
+                ? 'video/mp4'
+                : null,
+      media_payload:
+        messageType === 'voice'
+          ? request.body.mediaPayload
+          : isAttachment
+            ? attachmentId
+            : null,
+      media_waveform:
+        messageType === 'voice' ? request.body.mediaWaveform : null,
+      message_type: messageType,
+      media_asset_id: isAttachment ? attachmentId : null,
+      read_at: null,
+      recipient_number: phoneNumber,
+      sender_number: '5551234567',
+    }
+    smsMessages.push(message)
+    const { media_payload, ...publicMessage } = message
+    response.json({ success: true, data: publicMessage })
+    return
+  }
+  if (endpoint === 'messages:delete') {
+    const phoneNumbers = new Set(
+      Array.isArray(request.body.phoneNumbers)
+        ? request.body.phoneNumbers.map(String)
+        : [],
+    )
+    for (let index = smsMessages.length - 1; index >= 0; index -= 1) {
+      const message = smsMessages[index]
+      const otherNumber =
+        message.direction === 'sent'
+          ? message.recipient_number
+          : message.sender_number
+      if (phoneNumbers.has(otherNumber)) smsMessages.splice(index, 1)
+    }
+    response.json({ success: true })
+    return
+  }
+  if (endpoint === 'contacts:list') {
+    response.json({ success: true, data: contacts })
+    return
+  }
+  if (endpoint === 'contacts:save') {
+    const name = String(request.body.name ?? '').trim()
+    const phoneNumber = String(request.body.phoneNumber ?? '').trim()
+    if (!name || !phoneNumber) {
+      response.json({ success: false, error: 'invalid_contact' })
+      return
+    }
+    let contact = contacts.find((item) => item.id === request.body.id)
+    if (contact) {
+      contact.name = name
+      contact.phone_number = phoneNumber
+      contact.updated_at = new Date().toISOString().slice(0, 19).replace('T', ' ')
+    } else {
+      const now = new Date().toISOString().slice(0, 19).replace('T', ' ')
+      contact = {
+        created_at: now,
+        id: `contact-${contactSequence++}`,
+        name,
+        phone_number: phoneNumber,
+        updated_at: now,
+      }
+      contacts.push(contact)
+    }
+    response.json({ success: true, data: contact })
+    return
+  }
+  if (endpoint === 'contacts:delete') {
+    const index = contacts.findIndex((item) => item.id === request.body.id)
+    if (index >= 0) contacts.splice(index, 1)
+    response.json({ success: true })
+    return
+  }
   if (endpoint === 'account:login' || endpoint === 'account:register') {
     authenticated = true
     linkedAccount = {