diff --git a/services/platform/server.test.ts b/services/platform/server.test.ts
index a553e93328..e1f382308d 100644
--- a/services/platform/server.test.ts
+++ b/services/platform/server.test.ts
@@ -264,6 +264,20 @@ describe('security headers', () => {
       "connect-src 'self' https://acc.r2.cloudflarestorage.com",
     );
   });
+
+  test('content-hashed assets bypass the CSP/nonce middleware', async () => {
+    const app = createApp(baseEnv);
+    // A content-hashed asset path skips secureHeaders (no per-request CSP +
+    // crypto nonce), so its response carries no CSP — while a normal path still
+    // does (control). Independent of whether the file exists on disk.
+    const asset = await app.fetch(
+      new Request('http://localhost/assets/vendor-katex-DUoGyCxW.js'),
+    );
+    expect(asset.headers.get('content-security-policy')).toBeNull();
+
+    const normal = await app.fetch(new Request('http://localhost/api/health'));
+    expect(normal.headers.get('content-security-policy')).not.toBeNull();
+  });
 });
 
 describe('POST /canvas-preview', () => {
diff --git a/services/platform/server.ts b/services/platform/server.ts
index 8a4f54f54e..132910b619 100644
--- a/services/platform/server.ts
+++ b/services/platform/server.ts
@@ -669,6 +669,12 @@ export function createApp(
     if (c.req.path === '/canvas-preview') return next();
     if (c.req.path.startsWith('/dav/') || c.req.path === '/dav')
       return secureForDav(c, next);
+    // Content-hashed JS/CSS chunks are static and never use the nonce'd CSP, so
+    // skip the per-request CSP + crypto-nonce build for them — a cold load's
+    // ~150-asset burst would otherwise pay it on the single event loop. The
+    // static file handler re-adds the one header that matters for a script
+    // response, `X-Content-Type-Options: nosniff`.
+    if (IMMUTABLE_ASSET.test(c.req.path)) return next();
     return currentSecure()(c, next);
   });
 
@@ -913,10 +919,16 @@ export function createApp(
       if (filePath.startsWith(distDir)) {
         const file = Bun.file(filePath);
         if (await file.exists()) {
-          // Bun infers Content-Type from the file extension; we only add the
-          // caching directive (immutable for content-hashed chunks).
+          // Bun infers Content-Type from the file extension; we add the caching
+          // directive plus `nosniff`. Content-hashed assets skip the security-
+          // headers middleware above, so we re-assert the one header that
+          // matters for a script/style byte stream here (harmless duplicate for
+          // the other static files, which also get it from that middleware).
           return new Response(file, {
-            headers: { 'Cache-Control': cacheControlForStaticPath(pathname) },
+            headers: {
+              'Cache-Control': cacheControlForStaticPath(pathname),
+              'X-Content-Type-Options': 'nosniff',
+            },
           });
         }
       }