diff --git a/frontend/src/app.html b/frontend/src/app.html
index 440156d..6cdf730 100644
--- a/frontend/src/app.html
+++ b/frontend/src/app.html
@@ -42,8 +42,13 @@
         function report(reason) {
           if (sent) return; sent = true;             // one beacon per page
           try {
+            // The entry chunk's hashed filename identifies the build this page
+            // booted from — lets deploy-related errors correlate to a version.
+            var ver = '';
+            var pre = document.querySelector('link[rel="modulepreload"]');
+            if (pre) ver = (pre.getAttribute('href') || '').split('/').pop().slice(0, 60);
             var b = new Blob([JSON.stringify({ reason: String(reason || 'unknown').slice(0, 500),
-                                               path: location.pathname })], { type: 'application/json' });
+                                               path: location.pathname, version: ver })], { type: 'application/json' });
             navigator.sendBeacon && navigator.sendBeacon('/api/client-error', b);
           } catch (e) { /* best-effort telemetry */ }
         }
diff --git a/frontend/src/routes/admin/+page.svelte b/frontend/src/routes/admin/+page.svelte
index bd19ed5..9831e7f 100644
--- a/frontend/src/routes/admin/+page.svelte
+++ b/frontend/src/routes/admin/+page.svelte
@@ -462,7 +462,7 @@
               <span class="ce-when">{fdate(e.created_at)}</span>
               <span class="ce-reason">{e.reason || '—'}{#if e.bot}<span class="ce-bot">bot</span>{/if}</span>
               <span class="ce-path">{e.path || '/'}</span>
-              <span class="ce-ua">{e.user_agent}</span>
+              <span class="ce-ua">{e.user_agent}{#if e.app_version} · build {e.app_version}{/if}</span>
             </li>
           {/each}
         </ul>
diff --git a/frontend/src/service-worker.js b/frontend/src/service-worker.js
index f588f6a..1d3c15c 100644
--- a/frontend/src/service-worker.js
+++ b/frontend/src/service-worker.js
@@ -19,6 +19,25 @@ function isServerPath(p) {
   return p === '/openapi.json' || p === '/healthz' || p === '/today' || p === '/sitemap.xml';
 }
 
+// Mutable files Caddy serves with `no-cache` — the browser's HTTP cache
+// revalidates these correctly, but SW cache-as-you-go would pin them until the
+// next SW version and silently defeat that policy. version.json is the big one
+// (it's how the app detects a new deploy); stale word lists could drift from
+// the server's validated answer pool. Let the network/browser cache own them.
+function isMutablePath(p) {
+  return (
+    p === '/service-worker.js' ||
+    p === '/_app/version.json' ||
+    p === '/manifest.webmanifest' ||
+    p === '/words-5.json' ||
+    p === '/words-6.json' ||
+    p === '/favicon.svg' ||
+    p === '/logo.svg' ||
+    p === '/logo-email.png' ||
+    p.startsWith('/icon-')
+  );
+}
+
 self.addEventListener('install', (event) => {
   // Best-effort: grab the app shell as an offline fallback. No bulk precache.
   event.waitUntil(
@@ -40,7 +59,7 @@ self.addEventListener('fetch', (event) => {
   if (request.method !== 'GET') return;
   const url = new URL(request.url);
   if (url.origin !== location.origin) return;
-  if (isServerPath(url.pathname)) return; // let the network/server handle these
+  if (isServerPath(url.pathname) || isMutablePath(url.pathname)) return; // network/browser cache owns these
 
   // Navigations: network-first, but a SLOW network must not mean a white screen —
   // "slow" and "failed" both fall back to the cached shell. We race the fetch
diff --git a/goodnews/api.py b/goodnews/api.py
index c68e3fc..7f52811 100644
--- a/goodnews/api.py
+++ b/goodnews/api.py
@@ -959,7 +959,7 @@ def create_app() -> FastAPI:
         with get_conn() as conn:
             _require_admin(conn, request)
             rows = conn.execute(
-                "SELECT reason, path, user_agent, created_at FROM client_errors ORDER BY id DESC LIMIT 20"
+                "SELECT reason, path, user_agent, app_version, created_at FROM client_errors ORDER BY id DESC LIMIT 20"
             ).fetchall()
             # Bots stay visible in the list (tagged) but are excluded from the
             # headline counts — see queries.admin_stats.
diff --git a/tests/test_admin.py b/tests/test_admin.py
index 8b88e1a..bf89701 100644
--- a/tests/test_admin.py
+++ b/tests/test_admin.py
@@ -412,12 +412,14 @@ def test_word_pool_admin(tmp_path, monkeypatch):
 def test_client_error_telemetry(tmp_path, monkeypatch):
     app, api = _make(tmp_path, monkeypatch, admin_email="boss@x.com")
     anon = TestClient(app)
-    assert anon.post("/api/client-error", json={"reason": "boot-timeout", "path": "/play"}).json()["ok"] is True
+    assert anon.post("/api/client-error",
+                     json={"reason": "boot-timeout", "path": "/play", "version": "start.Bzfu1yPF.js"}).json()["ok"] is True
     assert anon.get("/api/admin/client-errors").status_code == 401  # gated
     tc = _signin(app, api, "boss@x.com")
     rows = tc.get("/api/admin/client-errors").json()
     assert len(rows) == 1 and rows[0]["reason"] == "boot-timeout" and rows[0]["path"] == "/play"
     assert rows[0]["user_agent"]  # captured from the request header
+    assert rows[0]["app_version"] == "start.Bzfu1yPF.js"  # build correlation for deploy-related errors
     assert rows[0]["bot"] is False
     assert tc.get("/api/admin/stats").json()["client_errors"]["today"] == 1
     # A throttled crawler tripping the beacon must NOT inflate the headline count,