diff --git a/ui/public/sw.js b/ui/public/sw.js
index c5f43d34ae0..213c029362e 100644
--- a/ui/public/sw.js
+++ b/ui/public/sw.js
@@ -50,6 +50,15 @@ self.addEventListener("fetch", (event) => {
     return;
   }
 
+  // Vite development modules use the browser's conditional-response cache.
+  // Passing their requests through fetch/respondWith can return a bodyless 304
+  // to the module loader on reload and leave the app root empty. They are not
+  // build assets and have no offline contract, so leave them to the browser.
+  if (url.origin === self.location.origin &&
+      /^\/(?:@fs|@vite|@id|src|node_modules)\//.test(url.pathname)) {
+    return;
+  }
+
   // Network-first; only public build assets can use an offline fallback.
   event.respondWith(
     fetch(request)
diff --git a/ui/src/lib/service-worker-cache-policy.test.ts b/ui/src/lib/service-worker-cache-policy.test.ts
index 92116966484..01911911059 100644
--- a/ui/src/lib/service-worker-cache-policy.test.ts
+++ b/ui/src/lib/service-worker-cache-policy.test.ts
@@ -22,6 +22,17 @@ function worker() {
 }
 
 describe("service worker privacy boundaries", () => {
+  it.each([
+    "/@fs/tmp/runner/vite-cache/deps/@assistant-ui_react.js?v=fixture",
+    "/@vite/client", "/@id/__x00__virtual:module", "/src/main.tsx", "/node_modules/.vite/deps/react.js",
+  ])("leaves conditional Vite module request %s to the browser", pathname => {
+    const w = worker();
+    w.fetch.mockResolvedValue(new Response(null, { status: 304 }));
+    expect(w.request("default", pathname)).not.toHaveBeenCalled();
+    expect(w.fetch).not.toHaveBeenCalled();
+    expect(w.put).not.toHaveBeenCalled();
+    expect(w.match).not.toHaveBeenCalled();
+  });
   it("bypasses both caching and offline fallback for a no-store request outside /api", () => {
     const w = worker();
     expect(w.request("no-store")).not.toHaveBeenCalled();