diff --git a/client/src/App.tsx b/client/src/App.tsx
index 0a097a9..23a3949 100644
--- a/client/src/App.tsx
+++ b/client/src/App.tsx
@@ -15,7 +15,11 @@ import InvitationAcceptance from './components/InvitationAcceptance.tsx'
 import AppTourOverlay from './components/AppTourOverlay.tsx'
 import { AppTourProvider, useAppTour, type AppTab } from './context/AppTourContext.tsx'
 import { UnsavedChangesProvider, useUnsavedChangesContext } from './context/UnsavedChangesContext.tsx'
-import { logoutUser, checkServerSession, hasUnlockedLocalSession } from './services/auth.js'
+import {
+  logoutUser,
+  checkServerSession,
+  hasUnlockedLocalCrypto
+} from './services/auth.js'
 import AppErrorBoundary from './components/AppErrorBoundary.tsx'
 import { PlausibleEvents, trackPlausibleEvent } from './services/analytics.js'
 import {
@@ -221,7 +225,7 @@ function App() {
   /** After PWA/bfcache resume, React state may still say "logged in" while the master key is gone. */
   const enforceUnlockedSession = useCallback(() => {
     if (isViewerMode || isDemoMode || isAcceptingInvite) return
-    if (isAuthenticated && !hasUnlockedLocalSession()) {
+    if (isAuthenticated && !hasUnlockedLocalCrypto()) {
       clearAuthenticatedAppState()
     }
   }, [
@@ -267,7 +271,7 @@ function App() {
           localStorage.setItem('active_userid', session.userId)
         }
 
-        if (session.authenticated && hasUnlockedLocalSession()) {
+        if (session.authenticated && hasUnlockedLocalCrypto()) {
           setIsAuthenticated(true)
           const savedLogbookId = localStorage.getItem('active_logbook_id')
           const savedLogbookTitle = localStorage.getItem('active_logbook_title')
@@ -275,9 +279,8 @@ function App() {
             setActiveLogbookId(savedLogbookId)
             setActiveLogbookTitle(savedLogbookTitle)
           }
-        } else if (session.authenticated) {
-          clearAuthenticatedAppState()
         }
+        // authenticated without local crypto: stay on login (cookie alone is not enough)
       } catch (err) {
         if (!cancelled) {
           console.warn('Session restore failed:', err)
diff --git a/client/src/services/auth.ts b/client/src/services/auth.ts
index 778c064..5c4a4a0 100644
--- a/client/src/services/auth.ts
+++ b/client/src/services/auth.ts
@@ -46,13 +46,14 @@ export async function checkServerSession(): Promise<{ authenticated: boolean; us
   }
 }
 
-/** Master key is memory-only; after process kill the HTTP session may outlive local crypto state. */
+/** Master key + username in memory/storage — enough to stay in the unlocked UI. */
+export function hasUnlockedLocalCrypto(): boolean {
+  return !!(getActiveMasterKey() && localStorage.getItem('active_username'))
+}
+
+/** Crypto unlock plus user id for authenticated API calls (userId may already be in localStorage). */
 export function hasUnlockedLocalSession(): boolean {
-  return !!(
-    getActiveMasterKey() &&
-    localStorage.getItem('active_username') &&
-    localStorage.getItem('active_userid')
-  )
+  return hasUnlockedLocalCrypto() && !!localStorage.getItem('active_userid')
 }
 
 export async function reauthWithPasskey(): Promise<boolean> {
diff --git a/client/src/services/authSession.test.ts b/client/src/services/authSession.test.ts
new file mode 100644
index 0000000..9b8d900
--- /dev/null
+++ b/client/src/services/authSession.test.ts
@@ -0,0 +1,34 @@
+import { beforeEach, describe, expect, it } from 'vitest'
+import {
+  hasUnlockedLocalCrypto,
+  hasUnlockedLocalSession,
+  setActiveMasterKey
+} from './auth.js'
+
+describe('local session unlock checks', () => {
+  beforeEach(() => {
+    localStorage.clear()
+    setActiveMasterKey(null)
+  })
+
+  it('hasUnlockedLocalCrypto with master key and username only', () => {
+    setActiveMasterKey(new ArrayBuffer(32))
+    localStorage.setItem('active_username', 'skipper')
+    expect(hasUnlockedLocalCrypto()).toBe(true)
+    expect(hasUnlockedLocalSession()).toBe(false)
+  })
+
+  it('hasUnlockedLocalSession when userId is present', () => {
+    setActiveMasterKey(new ArrayBuffer(32))
+    localStorage.setItem('active_username', 'skipper')
+    localStorage.setItem('active_userid', 'user-1')
+    expect(hasUnlockedLocalCrypto()).toBe(true)
+    expect(hasUnlockedLocalSession()).toBe(true)
+  })
+
+  it('hasUnlockedLocalCrypto false without master key', () => {
+    localStorage.setItem('active_username', 'skipper')
+    localStorage.setItem('active_userid', 'user-1')
+    expect(hasUnlockedLocalCrypto()).toBe(false)
+  })
+})