diff --git a/desktop/index.html b/desktop/index.html
index 4cf2a5cd..12d7107d 100644
--- a/desktop/index.html
+++ b/desktop/index.html
@@ -2,6 +2,18 @@
 <html lang="zh-CN" data-theme="white">
   <head>
     <meta charset="UTF-8" />
+    <!--
+      Conservative CSP: hardens default/object/base-uri without breaking the app.
+      script/style keep 'unsafe-inline' + 'unsafe-eval' on purpose - Emotion CSS-in-JS
+      injects runtime <style> tags, the startup watchdog below is inline, and shiki/
+      mermaid/Vite rely on eval. connect-src stays permissive (localhost sidecar + ws +
+      https) so renderer fetches and dev HMR keep working. Tighten only after verifying
+      on a packaged build.
+    -->
+    <meta
+      http-equiv="Content-Security-Policy"
+      content="default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline'; font-src 'self' data:; img-src 'self' data: blob: https: http://127.0.0.1:* http://localhost:*; connect-src 'self' https: http://127.0.0.1:* http://localhost:* ws://127.0.0.1:* ws://localhost:*; worker-src 'self' blob:; object-src 'none'; base-uri 'self'"
+    />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>Claude Code Companion</title>
     <!-- Fonts are self-hosted in /fonts/ and declared via @font-face in globals.css -->
