diff --git a/electron/main.cjs b/electron/main.cjs
index 429f91b..39e9733 100644
--- a/electron/main.cjs
+++ b/electron/main.cjs
@@ -54,10 +54,14 @@ function getStoredCredentials() {
 
 function writeCredentials(credentials) {
   if (!safeStorage.isEncryptionAvailable()) {
-    throw new Error('Secure credential storage is not available on this system')
+    throw new Error('macOS Keychain is locked or unavailable. Unlock Keychain and try signing in again.')
+  }
+  try {
+    const encrypted = safeStorage.encryptString(JSON.stringify(credentials))
+    fs.writeFileSync(userDataPath(credentialFileName), encrypted)
+  } catch (err) {
+    throw new Error(`Could not save credentials to secure storage: ${err.message || err}`)
   }
-  const encrypted = safeStorage.encryptString(JSON.stringify(credentials))
-  fs.writeFileSync(userDataPath(credentialFileName), encrypted)
 }
 
 function clearCredentials() {
@@ -162,6 +166,7 @@ async function syncNotes(credentials, pruneBefore) {
 }
 
 function createWindow() {
+  const appIndex = path.join(__dirname, '..', 'dist', 'index.html')
   const window = new BrowserWindow({
     width: 1180,
     height: 780,
@@ -187,14 +192,23 @@ function createWindow() {
     callback(false)
   })
 
-  window.webContents.on('will-navigate', event => {
-    if (!isDev) event.preventDefault()
+  window.webContents.on('will-navigate', (event, url) => {
+    const allowedUrl = isDev ? 'http://127.0.0.1:5173/' : `file://${appIndex}`
+    if (url !== allowedUrl) event.preventDefault()
+  })
+
+  window.webContents.on('render-process-gone', (_event, details) => {
+    console.error('Renderer process gone:', details.reason, details.exitCode)
+  })
+
+  window.webContents.on('console-message', (_event, level, message, line, sourceId) => {
+    console.log(`[renderer:${level}] ${message} (${sourceId}:${line})`)
   })
 
   if (isDev) {
     window.loadURL('http://127.0.0.1:5173')
   } else {
-    window.loadFile(path.join(__dirname, '..', 'dist', 'index.html'))
+    window.loadFile(appIndex)
   }
 }
 
diff --git a/package-lock.json b/package-lock.json
index b189682..78cafc4 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "nextcloud-notes-desktop",
-  "version": "0.1.2",
+  "version": "0.1.3",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "nextcloud-notes-desktop",
-      "version": "0.1.2",
+      "version": "0.1.3",
       "dependencies": {
         "react": "^19.2.6",
         "react-dom": "^19.2.6",
diff --git a/package.json b/package.json
index d8171ce..826cc22 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "nextcloud-notes-desktop",
-  "version": "0.1.2",
+  "version": "0.1.3",
   "private": true,
   "description": "Fast cross-platform desktop client for Nextcloud Notes",
   "author": {
diff --git a/src/main.jsx b/src/main.jsx
index a8cacb0..3b4608f 100644
--- a/src/main.jsx
+++ b/src/main.jsx
@@ -102,6 +102,37 @@ function Login({ onLogin }) {
   )
 }
 
+class ErrorBoundary extends React.Component {
+  constructor(props) {
+    super(props)
+    this.state = { error: null }
+  }
+
+  static getDerivedStateFromError(error) {
+    return { error }
+  }
+
+  componentDidCatch(error, errorInfo) {
+    console.error('Renderer error:', error, errorInfo)
+  }
+
+  render() {
+    if (this.state.error) {
+      return (
+        <main className="login-shell">
+          <section className="login-card">
+            <div className="brand-mark">!</div>
+            <h1>Nextcloud Notes hit an error</h1>
+            <p>The app did not start cleanly. This message replaces the blank screen so the issue can be diagnosed.</p>
+            <div className="error-box">{this.state.error.message || String(this.state.error)}</div>
+          </section>
+        </main>
+      )
+    }
+    return this.props.children
+  }
+}
+
 function App() {
   const [account, setAccount] = React.useState(null)
   const [notes, setNotes] = React.useState([])
@@ -375,6 +406,8 @@ function App() {
 
 createRoot(document.getElementById('root')).render(
   <React.StrictMode>
-    <App />
+    <ErrorBoundary>
+      <App />
+    </ErrorBoundary>
   </React.StrictMode>
 )