diff --git a/src/App.jsx b/src/App.jsx
index f6986d5..54f4579 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -9,6 +9,7 @@ import ProjectsPage from './pages/ProjectsPage'
 import AdminPage from './pages/AdminPage'
 import CustomersPage from './pages/CustomersPage'
 import CustomerDetailPage from './pages/CustomerDetailPage'
+import CustomerChatPage from './pages/CustomerChatPage'
 import FinancePage from './pages/FinancePage'
 import FinanceSettingsPage from './pages/FinanceSettingsPage'
 import LegalPage from './pages/LegalPage'
@@ -49,6 +50,8 @@ function AppRoutes() {
       <Route path="/" element={<Navigate to="/tickets" replace />} />
       <Route path="/tickets" element={<ProtectedRoute><TicketsPage /></ProtectedRoute>} />
       <Route path="/customers" element={<ProtectedRoute><CustomersPage /></ProtectedRoute>} />
+      {/* Messenger (Kunden -> Chat); statische Pfade gehen in react-router vor /customers/:id */}
+      <Route path="/customers/chat" element={<ProtectedRoute><CustomerChatPage /></ProtectedRoute>} />
       <Route path="/customers/:id" element={<ProtectedRoute><CustomerDetailPage /></ProtectedRoute>} />
       <Route path="/leads" element={<Navigate to="/tickets" replace />} />
       {/* Finanzen: nur Admins, alle anderen gehen zu /tickets */}
diff --git a/src/components/chat/ChatThread.jsx b/src/components/chat/ChatThread.jsx
new file mode 100644
index 0000000..d5eee50
--- /dev/null
+++ b/src/components/chat/ChatThread.jsx
@@ -0,0 +1,126 @@
+import { useEffect, useRef, useState } from 'react'
+import { FaRotateRight } from 'react-icons/fa6'
+import { Button } from '../ui'
+import { PORTAL_URL, chatUploadUrl, getChatMessages, markChatRead, sendChatMessage, teamAuthHeaders } from '../../lib/teamApi'
+import { loadChatComposer } from '../../lib/loadChatComposer'
+import { messageMeta, needsFullRefresh, noticeText } from '../../lib/chatFormat'
+import '../../styles/chat.css'
+
+const POLL_MS = 15 * 1000
+
+/**
+ * Gespraech mit einem Kunden (Messenger und Reiter "Chat"). Sprechblasen und Eingabezeile kommen aus dem
+ * Chat-Baustein des Portals (window.ChatComposer); React verwaltet nur die leeren Container.
+ * Antworten fuer einen inzwischen gewechselten Kunden werden verworfen (alive je Effekt).
+ */
+export default function ChatThread({ customerId, customerName }) {
+  const zoneRef = useRef(null)
+  const boxRef = useRef(null)
+  const composerRef = useRef(null)
+  const [error, setError] = useState(null)
+  const [notice, setNotice] = useState('')
+  const [reloadKey, setReloadKey] = useState(0)
+
+  useEffect(() => {
+    let alive = true
+    let composer = null
+    let timer = null
+    let chat = null
+    const state = { shown: new Set(), last: '', fullAt: 0 }
+    setError(null)
+    setNotice('')
+
+    const append = (messages) => {
+      const box = boxRef.current
+      if (!alive || !box || !chat) return
+      let added = false
+      for (const msg of messages) {
+        if (state.shown.has(msg.id)) continue
+        state.shown.add(msg.id)
+        box.appendChild(chat.renderMessage(msg, {
+          mine: msg.sender === 'admin',
+          meta: messageMeta(msg, customerName),
+          fileUrl: (att) => att.url,
+        }))
+        if (msg.createdAt > state.last) state.last = msg.createdAt
+        added = true
+      }
+      if (added) box.scrollTop = box.scrollHeight
+    }
+
+    // Ganzer Verlauf mit frischen signierten Links (beim Oeffnen und nach 10 Minuten)
+    const loadAll = async () => {
+      const { messages } = await getChatMessages(customerId)
+      if (!alive) return
+      boxRef.current?.replaceChildren()
+      state.shown = new Set()
+      state.last = ''
+      state.fullAt = Date.now()
+      append(messages || [])
+      markChatRead(customerId).catch(() => {})
+    }
+
+    const poll = async () => {
+      if (!alive || document.visibilityState === 'hidden' || !chat) return
+      try {
+        if (needsFullRefresh(state.fullAt, Date.now())) return await loadAll()
+        const { messages } = await getChatMessages(customerId, state.last)
+        if (!alive) return
+        append(messages || [])
+        if ((messages || []).some((m) => m.sender === 'customer')) markChatRead(customerId).catch(() => {})
+      } catch {
+        /* naechste Abfrage versucht es erneut */
+      }
+    }
+
+    ;(async () => {
+      try {
+        chat = await loadChatComposer({ baseUrl: PORTAL_URL })
+        if (!alive) return
+        chat.trackScroll(boxRef.current)
+        composer = chat.create({
+          root: composerRef.current,
+          dropZone: zoneRef.current,
+          uploadUrl: chatUploadUrl(customerId),
+          requestHeaders: teamAuthHeaders,
+          placeholder: `Antwort an ${customerName || 'Kunde'}…`,
+          placeholderShort: 'Antwort…',
+          send: async ({ text, attachmentIds }) => {
+            const { message, notice: result } = await sendChatMessage(customerId, { text, attachmentIds })
+            const time = new Date().toLocaleTimeString('de-DE', { hour: '2-digit', minute: '2-digit' })
+            if (alive) setNotice(noticeText(result, time))
+            return message
+          },
+          onSent: (message) => append([message]),
+        })
+        await loadAll()
+        timer = setInterval(poll, POLL_MS)
+      } catch (err) {
+        if (alive) setError(err.message || 'Die Unterhaltung konnte nicht geladen werden.')
+      }
+    })()
+
+    const onVisible = () => { if (document.visibilityState === 'visible') poll() }
+    document.addEventListener('visibilitychange', onVisible)
+    return () => {
+      alive = false
+      clearInterval(timer)
+      document.removeEventListener('visibilitychange', onVisible)
+      composer?.destroy()
+    }
+  }, [customerId, customerName, reloadKey])
+
+  return (
+    <div className="woms-chat" ref={zoneRef}>
+      {error && (
+        <div className="flex items-center gap-2 wrap">
+          <span className="muted">{error}</span>
+          <Button variant="ghost" onClick={() => setReloadKey((k) => k + 1)}><FaRotateRight /> Erneut versuchen</Button>
+        </div>
+      )}
+      <div className="chat-messages" ref={boxRef} aria-live="polite" />
+      {notice && <div className="chat-notice muted">{notice}</div>}
+      <div ref={composerRef} />
+    </div>
+  )
+}
diff --git a/src/lib/customerTabs.js b/src/lib/customerTabs.js
index a3b058c..8d3dda8 100644
--- a/src/lib/customerTabs.js
+++ b/src/lib/customerTabs.js
@@ -6,6 +6,8 @@ const BASE_TABS = [
   { id: 'tickets', label: 'Tickets' },
   { id: 'invoices', label: 'Rechnungen', adminOnly: true },
   { id: 'projects', label: 'Projekte' },
+  // Chat mit dem Kunden (derselbe Gespraechsbaustein wie im Messenger unter Kunden -> Chat)
+  { id: 'chat', label: 'Chat' },
   // Protokoll der Kundenansicht (wer wann das Portal des Kunden geöffnet oder darin etwas geändert hat): alle Mitarbeiter
   { id: 'protokoll', label: 'Protokoll' },
 ]
diff --git a/src/pages/CustomerChatPage.jsx b/src/pages/CustomerChatPage.jsx
new file mode 100644
index 0000000..80bc8a0
--- /dev/null
+++ b/src/pages/CustomerChatPage.jsx
@@ -0,0 +1,109 @@
+import { useEffect, useMemo, useState } from 'react'
+import { useSearchParams } from 'react-router-dom'
+import { FaArrowLeft, FaRotateRight } from 'react-icons/fa6'
+import { PageHeader, Card, Button, EmptyState, AutocompleteInput } from '../components/ui'
+import ChatThread from '../components/chat/ChatThread'
+import { useCustomers } from '../hooks/useCustomers'
+import { listChats } from '../lib/teamApi'
+import { formatViewLogTime } from '../lib/viewLog'
+import { lastLine, sortChats } from '../lib/chatFormat'
+import '../styles/chat.css'
+
+const LIST_POLL_MS = 30 * 1000
+
+// Messenger unter Kunden -> Chat: links alle Unterhaltungen, rechts das gewaehlte Gespraech (?kunde=<id>)
+export default function CustomerChatPage() {
+  const [params, setParams] = useSearchParams()
+  const kunde = params.get('kunde') || ''
+  const { customers } = useCustomers()
+  const [chats, setChats] = useState(null)
+  const [error, setError] = useState(null)
+  const [query, setQuery] = useState('')
+  const [reload, setReload] = useState(0)
+
+  useEffect(() => {
+    let alive = true
+    const load = () => {
+      if (document.visibilityState === 'hidden') return
+      listChats()
+        .then(({ chats: list }) => { if (alive) { setChats(list || []); setError(null) } })
+        .catch((err) => { if (alive) setError(err.message || 'Unterhaltungen konnten nicht geladen werden.') })
+    }
+    load()
+    const iv = setInterval(load, LIST_POLL_MS)
+    return () => { alive = false; clearInterval(iv) }
+  }, [reload, kunde])
+
+  const sorted = useMemo(() => sortChats(chats || []), [chats])
+  const nameOf = (id) =>
+    sorted.find((c) => c.customerId === id)?.customerName || customers.find((c) => c.$id === id)?.name || 'Kunde'
+
+  const open = (id) => setParams({ kunde: id })
+  const suggestions = (text) => {
+    const q = String(text || '').trim().toLowerCase()
+    if (!q) return []
+    return customers
+      .filter((c) => (c.name || '').toLowerCase().includes(q))
+      .slice(0, 8)
+      .map((c) => ({ value: c.name, hint: c.code || c.email || '' }))
+  }
+  const onPick = (value) => {
+    setQuery(value)
+    const hit = customers.find((c) => c.name === value)
+    if (hit) {
+      setQuery('')
+      open(hit.$id)
+    }
+  }
+
+  return (
+    <div className="page">
+      <PageHeader title="Chat" subtitle="Unterhaltungen mit Kunden aus dem Kundenportal" />
+      <div className={`chat-page ${kunde ? 'has-thread' : ''}`}>
+        <div className="chat-side">
+          <AutocompleteInput value={query} onChange={onPick} getSuggestions={suggestions} placeholder="Neue Nachricht an Kunde…" />
+          <Card pad={false}>
+            {error && (
+              <div className="flex items-center gap-2 wrap" style={{ padding: 12 }}>
+                <span className="muted">{error}</span>
+                <Button variant="ghost" onClick={() => setReload((k) => k + 1)}><FaRotateRight /> Erneut versuchen</Button>
+              </div>
+            )}
+            {!error && chats && sorted.length === 0 && <EmptyState title="Noch keine Unterhaltungen" />}
+            <div className="chat-list">
+              {sorted.map((c) => (
+                <button
+                  key={c.customerId}
+                  type="button"
+                  className={`chat-list-item ${c.customerId === kunde ? 'active' : ''}`}
+                  onClick={() => open(c.customerId)}
+                >
+                  <span className="chat-list-top">
+                    <strong>{c.customerName}</strong>
+                    {c.unreadFromCustomer > 0 && <span className="side-count">{c.unreadFromCustomer}</span>}
+                  </span>
+                  <span className="chat-list-last">{lastLine(c)}</span>
+                  <span className="chat-list-time">{formatViewLogTime(c.lastAt)}</span>
+                </button>
+              ))}
+            </div>
+          </Card>
+        </div>
+        <div className="chat-main">
+          {kunde ? (
+            <Card title={
+              <span className="flex items-center gap-2">
+                <Button variant="ghost" size="sm" className="chat-back" onClick={() => setParams({})}><FaArrowLeft /> Alle Unterhaltungen</Button>
+                {nameOf(kunde)}
+              </span>
+            }>
+              <ChatThread key={kunde} customerId={kunde} customerName={nameOf(kunde)} />
+            </Card>
+          ) : (
+            <Card><EmptyState title="Unterhaltung links auswählen" hint="Oder oben eine neue Nachricht an einen Kunden beginnen." /></Card>
+          )}
+        </div>
+      </div>
+    </div>
+  )
+}
diff --git a/src/pages/CustomerDetailPage.jsx b/src/pages/CustomerDetailPage.jsx
index 6402bb9..3473f58 100644
--- a/src/pages/CustomerDetailPage.jsx
+++ b/src/pages/CustomerDetailPage.jsx
@@ -13,6 +13,7 @@ import { useWebsiteProjects } from '../hooks/useWebsiteProjects'
 import { customerTabs, resolveCustomerTab } from '../lib/customerTabs'
 import { customerStage, isArchived, isInvoiceReady, setCustomerArchived, upgradeToCustomer } from '../lib/leads'
 import CustomerViewLog from '../components/customer/CustomerViewLog'
+import ChatThread from '../components/chat/ChatThread'
 import KundenansichtButton from '../components/customer/KundenansichtButton'
 import { getCustomerPortalStatus } from '../lib/teamApi'
 import { formatLastLogin } from '../lib/lastLogin'
@@ -104,6 +105,7 @@ export default function CustomerDetailPage() {
       {activeTab === 'tickets' && <CustomerTickets customerId={customer.$id} />}
       {activeTab === 'invoices' && <CustomerInvoices customer={customer} onShowOverview={() => setTab('overview')} />}
       {activeTab === 'projects' && <CustomerProjects customerId={customer.$id} />}
+      {activeTab === 'chat' && <Card><ChatThread customerId={customer.$id} customerName={customer.name} /></Card>}
       {activeTab === 'protokoll' && <CustomerViewLog customerId={customer.$id} />}
     </div>
   )
diff --git a/src/styles/chat.css b/src/styles/chat.css
new file mode 100644
index 0000000..8c70d06
--- /dev/null
+++ b/src/styles/chat.css
@@ -0,0 +1,52 @@
+/* Chat im Ticketsystem (Messenger und Reiter "Chat"). Eingabezeile, Anhaenge und Sprachnachrichten kommen aus
+   chat-composer.css des Kundenportals; hier Farben (--chat-*), Verlauf, Sprechblasen und die Liste. */
+.woms-chat {
+  --chat-accent: var(--accent);
+  --chat-accent-hover: var(--accent-2);
+  --chat-accent-soft: var(--accent-soft);
+  --chat-accent-line: rgba(16, 185, 129, 0.5);
+  --chat-accent-text: var(--accent);
+  --chat-on-accent: #04130d;
+  --chat-surface: var(--surface-2);
+  display: flex; flex-direction: column; gap: var(--sp-2); min-width: 0;
+}
+.woms-chat .chat-messages {
+  display: flex; flex-direction: column; gap: 8px; min-height: 280px; max-height: 60vh; overflow-y: auto;
+  padding: 12px; border: 1px solid var(--border); border-radius: var(--r-sm); background: var(--surface);
+}
+.woms-chat .chat-bubble {
+  align-self: flex-start; max-width: 78%; padding: 8px 12px; border-radius: 14px;
+  background: var(--surface-2); color: var(--text); overflow-wrap: anywhere;
+}
+.woms-chat .chat-bubble.mine { align-self: flex-end; background: var(--accent-soft); border: 1px solid rgba(16, 185, 129, 0.35); }
+.woms-chat .chat-meta { display: block; margin-top: 4px; font-size: 11.5px; color: var(--text-muted); }
+.woms-chat .chat-notice { font-size: 12px; }
+/* Eingabefeld: Grundstil wie im Admin-Panel (chat-composer.css setzt nur das Layout) */
+.woms-chat .chat-input-row textarea {
+  resize: none; min-height: 46px; max-height: 130px; padding: 11px 14px; border-radius: 14px;
+  border: 1px solid var(--border); background: var(--surface-2); color: var(--text); font: inherit; line-height: 1.4;
+}
+.woms-chat .chat-input-row textarea:focus { outline: none; border-color: var(--accent); }
+
+.chat-page { display: grid; grid-template-columns: 320px minmax(0, 1fr); gap: var(--sp-4); align-items: start; }
+.chat-side { display: flex; flex-direction: column; gap: var(--sp-3); min-width: 0; }
+.chat-list { display: flex; flex-direction: column; max-height: 70vh; overflow-y: auto; }
+.chat-list-item {
+  display: grid; gap: 2px; padding: 10px 14px; border: none; border-bottom: 1px solid var(--border);
+  background: transparent; color: var(--text); font: inherit; text-align: left; cursor: pointer;
+}
+.chat-list-item:hover { background: var(--surface-2); }
+.chat-list-item.active { background: var(--accent-soft); }
+.chat-list-top { display: flex; align-items: center; gap: 8px; justify-content: space-between; }
+.chat-list-last { color: var(--text-muted); font-size: 13px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
+.chat-list-time { color: var(--text-faint); font-size: 11.5px; }
+.chat-main { min-width: 0; }
+.chat-back { display: none; }
+
+@media (max-width: 720px) {
+  .chat-page { grid-template-columns: minmax(0, 1fr); }
+  .chat-page.has-thread .chat-side { display: none; }
+  .chat-page:not(.has-thread) .chat-main { display: none; }
+  .chat-back { display: inline-flex; }
+  .woms-chat .chat-bubble { max-width: 90%; }
+}
diff --git a/tests/unit/customerTabs.test.mjs b/tests/unit/customerTabs.test.mjs
index e71c443..41e14a8 100644
--- a/tests/unit/customerTabs.test.mjs
+++ b/tests/unit/customerTabs.test.mjs
@@ -4,19 +4,20 @@ import { loadModule } from './load.mjs'
 
 const { customerTabs, resolveCustomerTab } = await loadModule('src/lib/customerTabs.js')
 
-test('customerTabs: Rechnungen nur für Admins, Reihenfolge mit Protokoll, Übersicht mit Umlaut', () => {
+test('customerTabs: Rechnungen nur für Admins, Reihenfolge mit Chat und Protokoll, Übersicht mit Umlaut', () => {
   assert.deepEqual(customerTabs(true), [
     { id: 'overview', label: 'Übersicht' },
     { id: 'tickets', label: 'Tickets' },
     { id: 'invoices', label: 'Rechnungen' },
     { id: 'projects', label: 'Projekte' },
+    { id: 'chat', label: 'Chat' },
     { id: 'protokoll', label: 'Protokoll' },
   ])
   const staff = customerTabs(false)
-  assert.deepEqual(staff.map((t) => t.id), ['overview', 'tickets', 'projects', 'protokoll'])
+  assert.deepEqual(staff.map((t) => t.id), ['overview', 'tickets', 'projects', 'chat', 'protokoll'])
   // unbekannt oder nicht eindeutig true gilt als kein Admin
   for (const v of [undefined, null, 0, '', 'true']) {
-    assert.deepEqual(customerTabs(v).map((t) => t.id), ['overview', 'tickets', 'projects', 'protokoll'], String(v))
+    assert.deepEqual(customerTabs(v).map((t) => t.id), ['overview', 'tickets', 'projects', 'chat', 'protokoll'], String(v))
   }
   // die Einträge tragen nur id und label (kein internes Feld)
   assert.deepEqual(Object.keys(customerTabs(true)[2]), ['id', 'label'])
@@ -30,6 +31,7 @@ test('resolveCustomerTab: erlaubter Reiter bleibt, sonst Übersicht', () => {
   assert.equal(resolveCustomerTab('projects', false), 'projects')
   assert.equal(resolveCustomerTab('overview', false), 'overview')
   assert.equal(resolveCustomerTab('protokoll', false), 'protokoll')
+  assert.equal(resolveCustomerTab('chat', false), 'chat')
   assert.equal(resolveCustomerTab('gibtsnicht', true), 'overview')
   assert.equal(resolveCustomerTab(undefined, true), 'overview')
 })