diff --git a/src/components/Navbar.jsx b/src/components/Navbar.jsx
index 09f4db8..24aee32 100644
--- a/src/components/Navbar.jsx
+++ b/src/components/Navbar.jsx
@@ -16,10 +16,27 @@ import {
   IconLayoutSidebarLeftCollapse,
   IconLayoutSidebarLeftExpand,
   IconExternalLink,
+  IconMessages,
 } from '@tabler/icons-react'
 import { openProjectAdmin } from '../lib/employeeAdminApi'
 import { serverpulsApi } from '../lib/serverpulsApi'
 import { startsCollapsed } from '../lib/sidebar'
+import { buildNavLinks } from '../lib/navLinks'
+import { useChatUnread } from '../hooks/useChatUnread'
+
+const ICONS = {
+  tickets: <IconTicket />,
+  planboard: <IconCalendar />,
+  projects: <IconFolders />,
+  services: <IconLayoutGrid />,
+  customers: <IconUsers />,
+  chat: <IconMessages />,
+  leads: <IconTargetArrow />,
+  finance: <IconReportMoney />,
+  legal: <IconScale />,
+  serverpuls: <IconActivityHeartbeat />,
+  admin: <IconSettings />,
+}
 
 export default function Sidebar() {
   const { user, logout, isAdmin } = useAuth()
@@ -28,6 +45,7 @@ export default function Sidebar() {
   const [collapsed, setCollapsed] = useState(() => startsCollapsed())
   const [switching, setSwitching] = useState(false)
   const [pulseLevel, setPulseLevel] = useState('ok')
+  const chatUnread = useChatUnread()
 
   // Serverpuls-Punkt: nur Admins, beim Laden und alle 5 Minuten; Fehler bleiben still
   useEffect(() => {
@@ -53,20 +71,8 @@ export default function Sidebar() {
     navigate('/login')
   }
 
-  // Eine flache Liste: fuer ein kleines Team reichen acht Eintraege ohne Gruppen
-  const links = [
-    { label: 'Tickets', href: '/tickets', icon: <IconTicket /> },
-    { label: 'Planboard', href: '/planboard', icon: <IconCalendar /> },
-    { label: 'Projekte', href: '/projects', icon: <IconFolders /> },
-    { label: 'Services', href: '/services', icon: <IconLayoutGrid /> },
-    { label: 'Kunden', href: '/customers', icon: <IconUsers /> },
-    // Leads liegen auf Eis (Lead-Automatik gestoppt 2026-09-30): grau, nicht klickbar
-    { label: 'Leads', href: '/leads', icon: <IconTargetArrow />, paused: true },
-    ...(isAdmin ? [{ label: 'Finanzen', href: '/finance', also: '/finanzen', icon: <IconReportMoney /> }] : []),
-    { label: 'Rechtliches', href: '/rechtliches', icon: <IconScale /> },
-    ...(isAdmin ? [{ label: 'Serverpuls', href: '/serverpuls', icon: <IconActivityHeartbeat />, dot: pulseLevel }] : []),
-    ...(isAdmin ? [{ label: 'Admin', href: '/admin', icon: <IconSettings /> }] : []),
-  ]
+  // Eintraege und Unterpunkte (Kunden -> Chat) aus lib/navLinks.js, Icons ueber key
+  const links = buildNavLinks({ isAdmin, pulseLevel, chatUnread })
 
   const isActive = (href) =>
     location.pathname === href || location.pathname.startsWith(href + '/')
@@ -92,7 +98,7 @@ export default function Sidebar() {
               title={`${link.label} (pausiert)`}
               aria-disabled="true"
             >
-              {link.icon}
+              {ICONS[link.key]}
               <span className="side-link-label">{link.label}</span>
             </span>
           ) : (
@@ -102,7 +108,7 @@ export default function Sidebar() {
               className={`side-link ${isLinkActive(link) ? 'active' : ''}`}
               title={link.label}
             >
-              {link.icon}
+              {ICONS[link.key]}
               <span className="side-link-label">{link.label}</span>
               {link.dot && link.dot !== 'ok' && (
                 <span
@@ -112,7 +118,21 @@ export default function Sidebar() {
                 />
               )}
             </Link>
-          ))}
+          )).flatMap((item, i) => [
+            item,
+            ...(links[i].children || []).map((child) => (
+              <Link
+                key={child.href}
+                to={child.href}
+                className={`side-link side-sublink ${isActive(child.href) ? 'active' : ''}`}
+                title={child.count > 0 ? `${child.label} (${child.count} ungelesen)` : child.label}
+              >
+                {ICONS[child.key]}
+                <span className="side-link-label">{child.label}</span>
+                {child.count > 0 && <span className="side-count">{child.count}</span>}
+              </Link>
+            )),
+          ])}
           <button
             type="button"
             className="side-link side-link-button"
diff --git a/src/hooks/useChatUnread.js b/src/hooks/useChatUnread.js
new file mode 100644
index 0000000..b250333
--- /dev/null
+++ b/src/hooks/useChatUnread.js
@@ -0,0 +1,31 @@
+import { useEffect, useState } from 'react'
+import { getChatUnreadCount } from '../lib/teamApi'
+
+// Zahl ungelesener Kundennachrichten fuer die Sidebar: jede Minute bei sichtbarem Tab und sofort beim
+// Zurueckkehren; Fehler behalten den letzten Wert.
+const POLL_MS = 60 * 1000
+
+export function useChatUnread() {
+  const [unread, setUnread] = useState(0)
+
+  useEffect(() => {
+    let dead = false
+    const load = () => {
+      if (document.visibilityState === 'hidden') return
+      getChatUnreadCount()
+        .then((r) => { if (!dead) setUnread(Number(r?.unread) || 0) })
+        .catch(() => {})
+    }
+    load()
+    const iv = setInterval(load, POLL_MS)
+    const onVisible = () => { if (document.visibilityState === 'visible') load() }
+    document.addEventListener('visibilitychange', onVisible)
+    return () => {
+      dead = true
+      clearInterval(iv)
+      document.removeEventListener('visibilitychange', onVisible)
+    }
+  }, [])
+
+  return unread
+}
diff --git a/src/lib/chatFormat.js b/src/lib/chatFormat.js
new file mode 100644
index 0000000..14e9202
--- /dev/null
+++ b/src/lib/chatFormat.js
@@ -0,0 +1,31 @@
+import { formatViewLogTime } from './viewLog'
+
+// Chat im Ticketsystem: reine Hilfen fuer Liste, Hinweiszeile und Sprechblasen (unter Node testbar).
+
+/** Ungelesene zuerst, sonst die neueste Unterhaltung oben; die Eingabe bleibt unveraendert. */
+export function sortChats(chats) {
+  return [...chats].sort((a, b) => {
+    const unread = Number((b.unreadFromCustomer || 0) > 0) - Number((a.unreadFromCustomer || 0) > 0)
+    return unread || String(b.lastAt || '').localeCompare(String(a.lastAt || ''))
+  })
+}
+
+/** Ergebnis des Mail-Hinweises an den Kunden (K17), Texte wie im Admin-Panel. */
+export function noticeText(notice, time) {
+  if (!notice) return ''
+  if (notice.sent) return `E-Mail-Hinweis an ${notice.to} gesendet (${time})`
+  if (notice.reason === 'throttled') return 'Kein neuer E-Mail-Hinweis: Der Kunde wurde in den letzten 15 Minuten schon benachrichtigt.'
+  return `Kein E-Mail-Hinweis: ${notice.reason}`
+}
+
+export const lastLine = (chat) => `${chat.lastSender === 'admin' ? 'Du: ' : ''}${chat.lastText || ''}`
+
+/** Zeile unter der Sprechblase: Absender · dd.mm.yyyy hh:mm */
+export function messageMeta(msg, customerName) {
+  const who = msg.sender === 'admin' ? msg.senderName || 'Team' : customerName
+  return `${who} · ${formatViewLogTime(msg.createdAt)}`
+}
+
+// Signierte Anhang-Links gelten 15 Minuten: den Verlauf nach 10 Minuten komplett neu laden
+const FULL_REFRESH_MS = 10 * 60 * 1000
+export const needsFullRefresh = (lastFullAt, now) => now - lastFullAt >= FULL_REFRESH_MS
diff --git a/src/lib/navLinks.js b/src/lib/navLinks.js
new file mode 100644
index 0000000..7a6c2de
--- /dev/null
+++ b/src/lib/navLinks.js
@@ -0,0 +1,23 @@
+// Eintraege der Sidebar als reine Daten (unter Node testbar); Navbar.jsx ordnet die Icons ueber key zu.
+// Unterpunkte (children) erscheinen eingerueckt unter ihrem Eintrag, count zeigt eine Zahl (nur > 0).
+
+export function buildNavLinks({ isAdmin, pulseLevel, chatUnread }) {
+  return [
+    { key: 'tickets', label: 'Tickets', href: '/tickets' },
+    { key: 'planboard', label: 'Planboard', href: '/planboard' },
+    { key: 'projects', label: 'Projekte', href: '/projects' },
+    { key: 'services', label: 'Services', href: '/services' },
+    {
+      key: 'customers',
+      label: 'Kunden',
+      href: '/customers',
+      children: [{ key: 'chat', label: 'Chat', href: '/customers/chat', count: chatUnread }],
+    },
+    // Leads liegen auf Eis (Lead-Automatik gestoppt 2026-09-30): grau, nicht klickbar
+    { key: 'leads', label: 'Leads', href: '/leads', paused: true },
+    ...(isAdmin ? [{ key: 'finance', label: 'Finanzen', href: '/finance', also: '/finanzen' }] : []),
+    { key: 'legal', label: 'Rechtliches', href: '/rechtliches' },
+    ...(isAdmin ? [{ key: 'serverpuls', label: 'Serverpuls', href: '/serverpuls', dot: pulseLevel }] : []),
+    ...(isAdmin ? [{ key: 'admin', label: 'Admin', href: '/admin' }] : []),
+  ]
+}
diff --git a/src/styles/global.css b/src/styles/global.css
index 0978c91..00e5610 100644
--- a/src/styles/global.css
+++ b/src/styles/global.css
@@ -850,6 +850,15 @@ textarea.form-control {
 .side-link-button:disabled { opacity: 0.6; cursor: progress; }
 .side-link-paused, .side-link-paused:hover { opacity: 0.45; cursor: not-allowed; background: transparent; color: var(--text-muted); }
 .side-link.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
+.side-sublink { padding-left: calc(var(--sp-3) + 18px); font-size: 13.5px; }
+.side-sublink svg { width: 17px; height: 17px; }
+.side.collapsed .side-sublink { padding-left: var(--sp-3); }
+.side-count {
+  margin-left: auto; min-width: 20px; padding: 1px 6px; border-radius: 999px; text-align: center;
+  background: var(--accent); color: #04130d; font-size: 11.5px; font-weight: 700; line-height: 18px;
+}
+.side.collapsed .side-count { position: absolute; margin: -18px 0 0 14px; min-width: 16px; padding: 0 4px; font-size: 10px; line-height: 16px; }
+.side.collapsed .side-sublink { position: relative; }
 .side-link.active svg { color: var(--accent); }
 .side-foot { border-top: 1px solid var(--border); padding: var(--sp-3); }
 .side-toggle {
diff --git a/tests/unit/chatFormat.test.mjs b/tests/unit/chatFormat.test.mjs
new file mode 100644
index 0000000..faf1742
--- /dev/null
+++ b/tests/unit/chatFormat.test.mjs
@@ -0,0 +1,37 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { loadModule } from './load.mjs'
+
+// Chat im WOMS: Sortierung, Hinweis zur Kunden-Mail (K17, Texte wie im Admin-Panel), Zeilen und Neuladen
+const { sortChats, noticeText, lastLine, messageMeta, needsFullRefresh } = await loadModule('src/lib/chatFormat.js')
+
+test('sortChats: ungelesene zuerst, dann neueste', () => {
+  const chats = [
+    { customerId: 'a', lastAt: '2026-10-01T10:00:00.000Z', unreadFromCustomer: 0 },
+    { customerId: 'b', lastAt: '2026-10-01T08:00:00.000Z', unreadFromCustomer: 2 },
+    { customerId: 'c', lastAt: '2026-10-01T12:00:00.000Z', unreadFromCustomer: 0 },
+    { customerId: 'd', lastAt: '2026-10-01T09:00:00.000Z', unreadFromCustomer: 1 },
+  ]
+  assert.deepEqual(sortChats(chats).map((c) => c.customerId), ['d', 'b', 'c', 'a'])
+  assert.equal(chats[0].customerId, 'a', 'Eingabe bleibt unveraendert')
+})
+
+test('noticeText: gesendet, gedrosselt, Grund, leer', () => {
+  assert.equal(noticeText({ sent: true, to: 'k@x.de' }, '14:05'), 'E-Mail-Hinweis an k@x.de gesendet (14:05)')
+  assert.equal(noticeText({ sent: false, reason: 'throttled' }, '14:05'), 'Kein neuer E-Mail-Hinweis: Der Kunde wurde in den letzten 15 Minuten schon benachrichtigt.')
+  assert.equal(noticeText({ sent: false, reason: 'SMTP weg' }, '14:05'), 'Kein E-Mail-Hinweis: SMTP weg')
+  assert.equal(noticeText(null, '14:05'), '')
+})
+
+test('messageMeta und lastLine', () => {
+  assert.equal(messageMeta({ sender: 'admin', senderName: 'Andrej', createdAt: '2026-09-30T10:05:00.000Z' }, 'Berta Berg'), 'Andrej · 30.09.2026 12:05')
+  assert.equal(messageMeta({ sender: 'admin', senderName: '', createdAt: '2026-09-30T10:05:00.000Z' }, 'Berta Berg'), 'Team · 30.09.2026 12:05')
+  assert.equal(messageMeta({ sender: 'customer', senderName: 'x', createdAt: '2026-09-30T10:05:00.000Z' }, 'Berta Berg'), 'Berta Berg · 30.09.2026 12:05')
+  assert.equal(lastLine({ lastSender: 'admin', lastText: 'Erledigt' }), 'Du: Erledigt')
+  assert.equal(lastLine({ lastSender: 'customer', lastText: 'Danke' }), 'Danke')
+})
+
+test('needsFullRefresh ab 10 Minuten', () => {
+  assert.equal(needsFullRefresh(0, 599999), false)
+  assert.equal(needsFullRefresh(0, 600000), true)
+})
diff --git a/tests/unit/navLinks.test.mjs b/tests/unit/navLinks.test.mjs
new file mode 100644
index 0000000..635f63f
--- /dev/null
+++ b/tests/unit/navLinks.test.mjs
@@ -0,0 +1,19 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { loadModule } from './load.mjs'
+
+// Sidebar: Eintraege als reine Daten (Icons ordnet Navbar.jsx ueber key zu)
+const { buildNavLinks } = await loadModule('src/lib/navLinks.js')
+
+test('buildNavLinks: Chat unter Kunden mit Zahl, Admin-Eintraege nur fuer Admins', () => {
+  const links = buildNavLinks({ isAdmin: false, pulseLevel: 'ok', chatUnread: 3 })
+  const kunden = links.find((l) => l.key === 'customers')
+  assert.equal(kunden.href, '/customers')
+  assert.deepEqual(kunden.children, [{ key: 'chat', label: 'Chat', href: '/customers/chat', count: 3 }])
+  assert.deepEqual(links.map((l) => l.key), ['tickets', 'planboard', 'projects', 'services', 'customers', 'leads', 'legal'])
+  assert.equal(links.find((l) => l.key === 'leads').paused, true)
+  const admin = buildNavLinks({ isAdmin: true, pulseLevel: 'warn', chatUnread: 0 })
+  assert.deepEqual(admin.map((l) => l.key), ['tickets', 'planboard', 'projects', 'services', 'customers', 'leads', 'finance', 'legal', 'serverpuls', 'admin'])
+  assert.equal(admin.find((l) => l.key === 'serverpuls').dot, 'warn')
+  assert.equal(admin.find((l) => l.key === 'finance').also, '/finanzen')
+})