diff --git a/plugins/sync/frontend/src/SyncSettings.svelte b/plugins/sync/frontend/src/SyncSettings.svelte
index c8df788..0c72417 100644
--- a/plugins/sync/frontend/src/SyncSettings.svelte
+++ b/plugins/sync/frontend/src/SyncSettings.svelte
@@ -193,6 +193,11 @@
   {#if resultMsg && !errorMsg}
     <div style="padding:0.5rem 0.75rem;margin-bottom:0.75rem;border-radius:6px;font-size:0.85rem;{resultKind === 'warning' ? 'background:rgba(245,158,11,0.1);border:1px solid rgba(245,158,11,0.3);color:#f59e0b;' : 'background:rgba(52,211,153,0.1);border:1px solid rgba(52,211,153,0.3);color:#34d399;'}">{resultMsg}</div>
   {/if}
+  {#if settings && settings.lastError && !errorMsg}
+    <div style="padding:0.5rem 0.75rem;margin-bottom:0.75rem;background:rgba(255,107,107,0.1);border:1px solid rgba(255,107,107,0.3);border-radius:6px;color:#ff6b6b;font-size:0.85rem;">
+      Last sync error: {sanitizeError(settings.lastError)}
+    </div>
+  {/if}
 
   <div style="background:#16213e;border:1px solid #0f3460;border-radius:8px;padding:1rem 1.25rem;margin-bottom:1rem;">
     <h3 style="margin:0 0 0.75rem;color:#e0e0f0;font-size:0.95rem;">Server</h3>
diff --git a/scripts/check.sh b/scripts/check.sh
index d6081b9..ca03daf 100755
--- a/scripts/check.sh
+++ b/scripts/check.sh
@@ -223,6 +223,8 @@ if command -v node &>/dev/null; then
   report "browser inbox frontend behavior" $?
   node "$ROOT/scripts/smoke-search-plugin.js"
   report "search frontend behavior" $?
+  node "$ROOT/scripts/smoke-sync-plugin.js"
+  report "sync frontend behavior" $?
 else
   echo "  ⚠️  node not available — skipping frontend smoke"
 fi
diff --git a/scripts/smoke-sync-plugin.js b/scripts/smoke-sync-plugin.js
new file mode 100644
index 0000000..543dfb5
--- /dev/null
+++ b/scripts/smoke-sync-plugin.js
@@ -0,0 +1,19 @@
+#!/usr/bin/env node
+const fs = require('fs');
+const path = require('path');
+
+const root = path.resolve(__dirname, '..');
+const sourcePath = path.join(root, 'plugins', 'sync', 'frontend', 'src', 'SyncSettings.svelte');
+const source = fs.readFileSync(sourcePath, 'utf8');
+
+if (!source.includes('settings.lastError')) {
+  throw new Error('SyncSettings must render persisted settings.lastError');
+}
+if (!source.includes('sanitizeError(settings.lastError)')) {
+  throw new Error('SyncSettings must sanitize persisted sync errors before rendering');
+}
+if (!source.includes('Last sync error')) {
+  throw new Error('SyncSettings must label the persisted sync error');
+}
+
+console.log('sync plugin smoke passed');