diff --git a/server/app.js b/server/app.js
index 4ee54a3..edeaebc 100644
--- a/server/app.js
+++ b/server/app.js
@@ -50,7 +50,7 @@ function createApp({ skipRateLimits = false } = {}) {
           baseUri: ["'self'"],
           frameAncestors: ["'none'"],
           formAction: ["'self'"],
-          upgradeInsecureRequests: process.env.NODE_ENV === 'production' ? [] : null
+          upgradeInsecureRequests: process.env.TRUST_PROXY ? [] : null
         }
       },
       hsts: { maxAge: 31536000, includeSubDomains: true, preload: true },
diff --git a/server/index.js b/server/index.js
index f9badcb..b2e9583 100644
--- a/server/index.js
+++ b/server/index.js
@@ -137,7 +137,7 @@ app.use((req, res, next) => {
         baseUri: ["'self'"],
         frameAncestors: ["'none'"],
         formAction: ["'self'"],
-        upgradeInsecureRequests: process.env.NODE_ENV === 'production' ? [] : null
+        upgradeInsecureRequests: process.env.TRUST_PROXY ? [] : null
       }
     },
     hsts: {
@@ -214,15 +214,17 @@ app.use(express.static(PUBLIC_DIR, {
   }
 }));
 
-// Serve index.html with nonce injected into the <script> and <link> tags
+// Serve index.html with CSP nonce injected into <script> tags
 function serveIndex(req, res) {
   fs.readFile(INDEX_HTML, 'utf8', (err, html) => {
     if (err) return res.status(500).send('Internal Server Error');
     const nonce = res.locals.cspNonce;
-    // Inject nonce into <script> and <link rel="stylesheet"> tags
+    // Only inject nonce into <script> tags — style-src 'self' already permits
+    // same-origin <link rel=stylesheet> without a nonce, and injecting a nonce
+    // onto <link> breaks mobile browsers / caching proxies (stale HTML carries
+    // the old nonce which no longer matches the per-request CSP header).
     const patched = html
-      .replace(/<script([^>]*)>/gi, `<script nonce="${nonce}"$1>`)
-      .replace(/<link([^>]*rel=["']stylesheet["'][^>]*)>/gi, `<link nonce="${nonce}"$1>`);
+      .replace(/<script([^>]*)>/gi, `<script nonce="${nonce}"$1>`);
     res.setHeader('Content-Type', 'text/html; charset=utf-8');
     res.send(patched);
   });