diff --git a/src/components/AssignedProjectCard.jsx b/src/components/AssignedProjectCard.jsx
index 923d485..2ea47e5 100644
--- a/src/components/AssignedProjectCard.jsx
+++ b/src/components/AssignedProjectCard.jsx
@@ -91,7 +91,7 @@ export default function AssignedProjectCard({ project, onUnassign, showActions =
           )}
         </div>
         <div style={{ display: 'flex', gap: 8, alignItems: 'center', flexShrink: 0 }}>
-          <PreviewLinkButton href={project.previewUrl} />
+          <PreviewLinkButton href={project.previewUrl} subdomain={project.subdomain} />
           <GiteaLinkButton href={project.giteaRepoUrl} />
           {showActions && onUnassign && (
             <button
diff --git a/src/components/PreviewLinkButton.jsx b/src/components/PreviewLinkButton.jsx
index bcdfbfa..46a2e0c 100644
--- a/src/components/PreviewLinkButton.jsx
+++ b/src/components/PreviewLinkButton.jsx
@@ -1,11 +1,24 @@
 import { FaEye } from 'react-icons/fa6'
+import { createPreviewLink } from '../lib/teamApi'
+import { openInNewTab } from '../lib/openInNewTab'
 
-export default function PreviewLinkButton({ href, title = 'Preview oeffnen', size = 16 }) {
+// Mit subdomain holt der Knopf einen Einmal-Link vom Portal (Mitarbeiter sind dort nicht mehr angemeldet);
+// ohne subdomain bleibt er ein einfacher Link.
+export default function PreviewLinkButton({ href, subdomain, title = 'Preview oeffnen', size = 16 }) {
   if (!href) return null
 
+  const open = (event) => {
+    if (!subdomain) return
+    event.preventDefault()
+    openInNewTab(() => createPreviewLink({ subdomain, previewUrl: href })).catch((err) =>
+      window.alert(err.message || 'Die Preview konnte nicht geöffnet werden.')
+    )
+  }
+
   return (
     <a
       href={href}
+      onClick={open}
       target="_blank"
       rel="noopener noreferrer"
       title={title}
diff --git a/src/components/customer/KundenansichtButton.jsx b/src/components/customer/KundenansichtButton.jsx
new file mode 100644
index 0000000..5090325
--- /dev/null
+++ b/src/components/customer/KundenansichtButton.jsx
@@ -0,0 +1,33 @@
+import { useState } from 'react'
+import { FaArrowUpRightFromSquare, FaSpinner } from 'react-icons/fa6'
+import { Button } from '../ui'
+import { createKundenansichtLink } from '../../lib/teamApi'
+import { openInNewTab } from '../../lib/openInNewTab'
+
+/** Kundenansicht im Portal in einem neuen Tab öffnen (Einmal-Link). Ohne Portal-Zugang ausgegraut. */
+export default function KundenansichtButton({ customer, variant = 'primary' }) {
+  const [busy, setBusy] = useState(false)
+  const hasAccess = Boolean(customer?.portalAccessEnabled && customer?.appwriteUserId)
+
+  const open = async () => {
+    setBusy(true)
+    try {
+      await openInNewTab(() => createKundenansichtLink(customer.$id))
+    } catch (err) {
+      window.alert(err.message || 'Die Kundenansicht konnte nicht geöffnet werden.')
+    } finally {
+      setBusy(false)
+    }
+  }
+
+  return (
+    <Button
+      variant={variant}
+      onClick={open}
+      disabled={!hasAccess || busy}
+      title={hasAccess ? 'Portal so öffnen, wie der Kunde es sieht' : 'Kein Portal-Zugang'}
+    >
+      {busy ? <FaSpinner className="spinner" /> : <FaArrowUpRightFromSquare />} Kundenansicht öffnen
+    </Button>
+  )
+}
diff --git a/src/lib/lastLogin.js b/src/lib/lastLogin.js
new file mode 100644
index 0000000..f1ba370
--- /dev/null
+++ b/src/lib/lastLogin.js
@@ -0,0 +1,10 @@
+import { formatViewLogTime } from './viewLog'
+
+// Letzter Portal-Login eines Kunden (Karte „Portal-Zugang“). Rein, unter Node testbar.
+
+/** ISO-Zeit -> "dd.mm.yyyy, hh:mm Uhr" in deutscher Zeit; ohne Login "noch nie". */
+export function formatLastLogin(iso) {
+  if (!iso) return 'noch nie'
+  const [day, time] = formatViewLogTime(iso).split(' ')
+  return `${day}, ${time} Uhr`
+}
diff --git a/src/pages/CustomerDetailPage.jsx b/src/pages/CustomerDetailPage.jsx
index f34f02b..6402bb9 100644
--- a/src/pages/CustomerDetailPage.jsx
+++ b/src/pages/CustomerDetailPage.jsx
@@ -1,6 +1,6 @@
 import { useState, useEffect, useCallback } from 'react'
 import { useParams, Link, useNavigate, useSearchParams } from 'react-router-dom'
-import { FaSpinner, FaStar, FaArrowLeft, FaFloppyDisk, FaArrowUp, FaKey, FaArrowUpRightFromSquare, FaBoxArchive, FaBoxOpen, FaTrash } from 'react-icons/fa6'
+import { FaSpinner, FaStar, FaArrowLeft, FaFloppyDisk, FaArrowUp, FaKey, FaBoxArchive, FaBoxOpen, FaTrash } from 'react-icons/fa6'
 import { databases, DATABASE_ID, COLLECTIONS, Query } from '../lib/appwrite'
 import { PageHeader, Card, Button, Badge, Tabs, EmptyState, Field } from '../components/ui'
 import { StatusPill, UrgentPill } from '../components/ui/StatusPill'
@@ -13,6 +13,9 @@ 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 KundenansichtButton from '../components/customer/KundenansichtButton'
+import { getCustomerPortalStatus } from '../lib/teamApi'
+import { formatLastLogin } from '../lib/lastLogin'
 
 const PORTAL_URL = 'https://project.webklar.com'
 
@@ -85,6 +88,7 @@ export default function CustomerDetailPage() {
         subtitle={[customer.location, customer.email, customer.phone].filter(Boolean).join(' · ')}
         actions={
           <>
+            <KundenansichtButton customer={customer} />
             <Button variant="ghost" onClick={toggleArchived}>
               {archived ? <><FaBoxOpen /> Wiederherstellen</> : <><FaBoxArchive /> Archivieren</>}
             </Button>
@@ -200,6 +204,15 @@ function PortalAccessCard({ customer, onSaved }) {
 
   const hasAccess = Boolean(customer.portalAccessEnabled && customer.appwriteUserId)
   const currentPassword = getCustomerPortalPassword(customer)
+  // Letzter Login kommt vom Portal (customerPortalAccess), nicht aus dem Kunden-Dokument
+  const [lastLogin, setLastLogin] = useState(undefined)
+  useEffect(() => {
+    let active = true
+    getCustomerPortalStatus(customer.$id)
+      .then((status) => active && setLastLogin(status.lastLoginAt || null))
+      .catch(() => active && setLastLogin(false))
+    return () => { active = false }
+  }, [customer.$id])
 
   const savePassword = async () => {
     if (!customer.email) {
@@ -232,6 +245,11 @@ function PortalAccessCard({ customer, onSaved }) {
           : <Badge tone="muted">kein Zugang</Badge>}
       </div>
 
+      <div className="flex items-center justify-between" style={{ marginBottom: 12 }}>
+        <span className="muted">Letzter Login</span>
+        <span>{lastLogin === undefined ? '…' : lastLogin === false ? 'nicht abrufbar' : formatLastLogin(lastLogin)}</span>
+      </div>
+
       <Field label="Login (E-Mail)">
         <CopyableCredential value={customer.email} label="Login" />
       </Field>
@@ -254,9 +272,7 @@ function PortalAccessCard({ customer, onSaved }) {
         <Button variant="primary" onClick={savePassword} disabled={busy}>
           {busy ? <FaSpinner className="spinner" /> : <><FaKey /> {hasAccess ? 'Passwort ändern' : 'Zugang anlegen'}</>}
         </Button>
-        <Button as="a" href={PORTAL_URL} target="_blank" rel="noreferrer" variant="ghost">
-          <FaArrowUpRightFromSquare /> Portal öffnen
-        </Button>
+        <KundenansichtButton customer={customer} variant="ghost" />
         {msg && <span className="muted">{msg}</span>}
       </div>
       <p className="muted" style={{ marginTop: 8, fontSize: 13 }}>
diff --git a/src/pages/ProjectsPage.jsx b/src/pages/ProjectsPage.jsx
index 99ee8d2..fe22b8c 100644
--- a/src/pages/ProjectsPage.jsx
+++ b/src/pages/ProjectsPage.jsx
@@ -574,7 +574,7 @@ export default function ProjectsPage() {
                       <FaGlobe style={hostBusyId === project.$id ? { animation: 'spin 1s linear infinite' } : undefined} />
                     </button>
                   ) : (
-                    <PreviewLinkButton href={project.previewUrl} />
+                    <PreviewLinkButton href={project.previewUrl} subdomain={project.subdomain} />
                   )}
                   {hosted && ready && !project.archived && (
                     <button
diff --git a/tests/unit/lastLogin.test.mjs b/tests/unit/lastLogin.test.mjs
new file mode 100644
index 0000000..ea8bf66
--- /dev/null
+++ b/tests/unit/lastLogin.test.mjs
@@ -0,0 +1,13 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { loadModule } from './load.mjs'
+
+// Karte „Portal-Zugang“: letzter Login des Kunden in deutscher Zeit
+const { formatLastLogin } = await loadModule('src/lib/lastLogin.js')
+
+test('formatLastLogin', () => {
+  assert.equal(formatLastLogin(null), 'noch nie')
+  assert.equal(formatLastLogin(''), 'noch nie')
+  assert.equal(formatLastLogin('2026-09-30T10:05:00.000Z'), '30.09.2026, 12:05 Uhr')
+  assert.equal(formatLastLogin('2026-01-15T07:00:00.000Z'), '15.01.2026, 08:00 Uhr')
+})