diff --git a/ui/public/sw.js b/ui/public/sw.js
index 4f9da070a7a..12a8c73c5d9 100644
--- a/ui/public/sw.js
+++ b/ui/public/sw.js
@@ -6,6 +6,15 @@
 // dev, where HMR (not the worker) drives refreshes.
 const BUILD_ID = "__PAPERCLIP_BUILD_ID__";
 const CACHE_NAME = `paperclip-${BUILD_ID}`;
+const privateRequests = new Set();
+const privateCacheControl = /(?:^|,)\s*(?:no-store|private)(?:\s*(?:,|=)|\s*$)/i;
+
+async function evictRequest(request) {
+  await Promise.all((await caches.keys()).map(async (key) => {
+    const cache = await caches.open(key);
+    await cache.delete(request, { ignoreVary: true });
+  }));
+}
 
 self.addEventListener("install", () => {
   self.skipWaiting();
@@ -26,28 +35,44 @@ self.addEventListener("fetch", (event) => {
 
   // Explicitly private requests must bypass BOTH cache writes and offline
   // fallback, including extension endpoints outside the host /api namespace.
-  if (request.method !== "GET" || url.pathname.startsWith("/api") || request.cache === "no-store") {
+  if (request.method !== "GET" || url.pathname.startsWith("/api")) {
+    return;
+  }
+  if (request.cache === "no-store") {
+    privateRequests.add(request.url);
+    event.waitUntil(evictRequest(request).catch(() => {}));
     return;
   }
 
   // Network-first for everything — cache is only an offline fallback
   event.respondWith(
     fetch(request)
-      .then((response) => {
+      .then(async (response) => {
         const cacheControl = response.headers.get("cache-control") ?? "";
-        if (response.ok && url.origin === self.location.origin && !/(?:^|,)\s*(?:no-store|private)(?:\s*(?:,|=)|\s*$)/i.test(cacheControl)) {
+        if (privateCacheControl.test(cacheControl)) {
+          // Revoke earlier cacheable responses too. Keep an in-memory denylist
+          // if storage is unavailable so offline fallback still fails closed.
+          privateRequests.add(request.url);
+          await evictRequest(request).catch(() => {});
+        } else if (response.ok && url.origin === self.location.origin && !privateRequests.has(request.url)) {
           const clone = response.clone();
-          caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
+          await caches.open(CACHE_NAME).then(async (cache) => {
+            await cache.put(request, clone);
+            // A concurrent response may have revoked this URL during put().
+            if (privateRequests.has(request.url)) await cache.delete(request, { ignoreVary: true });
+          }).catch(() => {});
         }
         return response;
       })
       .catch(async () => {
+        if (privateRequests.has(request.url)) return Response.error();
         // caches.match() resolves undefined on a miss (and the promise itself
         // is always truthy, so `||` can never supply a fallback). respondWith
         // must always receive a real Response — resolving undefined breaks
         // the navigation with "Failed to convert value to 'Response'" instead
         // of showing anything.
         if (request.mode === "navigate") {
+          if (privateRequests.has(new URL("/", self.location.origin).href)) return new Response("Offline", { status: 503 });
           return (await caches.match("/")) ?? new Response("Offline", { status: 503 });
         }
         return (await caches.match(request)) ?? Response.error();
diff --git a/ui/src/lib/service-worker-cache-policy.test.ts b/ui/src/lib/service-worker-cache-policy.test.ts
index 802be4ef178..9dca26cc7f4 100644
--- a/ui/src/lib/service-worker-cache-policy.test.ts
+++ b/ui/src/lib/service-worker-cache-policy.test.ts
@@ -7,17 +7,18 @@ function worker() {
   const handlers = new Map<string, (event: unknown) => void>();
   const put = vi.fn();
   const match = vi.fn();
+  const remove = vi.fn().mockResolvedValue(true);
   const fetch = vi.fn().mockResolvedValue(new Response("public asset"));
   vm.runInNewContext(readFileSync(new URL("../../public/sw.js", import.meta.url), "utf8"), {
     self: { location: { origin: "https://example.test" }, addEventListener: (type: string, fn: (event: unknown) => void) => handlers.set(type, fn) },
-    URL, Response, fetch, caches: { open: async () => ({ put }), match },
+    URL, Response, fetch, caches: { keys: async () => ["paperclip-old", "paperclip-current"], open: async () => ({ put, delete: remove }), match },
   });
   const request = (cache: RequestCache = "default") => {
     const respondWith = vi.fn();
-    handlers.get("fetch")!({ request: new Request("https://example.test/extension/history", { cache }), respondWith });
+    handlers.get("fetch")!({ request: new Request("https://example.test/extension/history", { cache }), respondWith, waitUntil: vi.fn() });
     return respondWith;
   };
-  return { request, fetch, put, match };
+  return { request, fetch, put, match, remove };
 }
 
 describe("service worker privacy boundaries", () => {
@@ -40,4 +41,23 @@ describe("service worker privacy boundaries", () => {
     await w.request().mock.calls[0]![0];
     expect(w.put).toHaveBeenCalledOnce();
   });
+  it.each(["private", "no-store"])("evicts stale entries when a response becomes %s and blocks offline reuse", async directive => {
+    const w = worker();
+    w.match.mockResolvedValue(new Response("stale personal content"));
+    w.fetch.mockResolvedValue(new Response("fresh", { headers: { "cache-control": directive } }));
+    await w.request().mock.calls[0]![0];
+    expect(w.remove).toHaveBeenCalledTimes(2);
+    expect(w.remove).toHaveBeenCalledWith(expect.any(Request), { ignoreVary: true });
+    w.fetch.mockRejectedValue(new Error("offline"));
+    const offline = await w.request().mock.calls[0]![0];
+    expect(offline.type).toBe("error"); expect(w.match).not.toHaveBeenCalled();
+  });
+  it("does not serve stale data when cache eviction itself fails", async () => {
+    const w = worker(); w.remove.mockRejectedValue(new Error("cache unavailable"));
+    w.fetch.mockResolvedValue(new Response("fresh", { headers: { "cache-control": "private" } }));
+    expect(await (await w.request().mock.calls[0]![0]).text()).toBe("fresh");
+    w.fetch.mockRejectedValue(new Error("offline"));
+    expect((await w.request().mock.calls[0]![0]).type).toBe("error");
+    expect(w.match).not.toHaveBeenCalled();
+  });
 });