diff --git a/extension/background.firefox.js b/extension/background.firefox.js
index 1412d30..27fa209 100644
--- a/extension/background.firefox.js
+++ b/extension/background.firefox.js
@@ -53,7 +53,7 @@ if (!chrome.storage.session) {
 
 // ── Idle lock (timeout-based, no chrome.idle) ─────────────────────────────────
 
-const DEFAULT_IDLE_LOCK_SECONDS = 600;
+const DEFAULT_IDLE_LOCK_SECONDS = 0;
 const IDLE_TIMEOUT_KEY = 'idle_lock_seconds';
 let _idleTimer = null;
 
diff --git a/extension/background.js b/extension/background.js
index bbccbcb..930b3cf 100644
--- a/extension/background.js
+++ b/extension/background.js
@@ -10,8 +10,8 @@
 
 // ── Idle lock ─────────────────────────────────────────────────────────────────
 
-// Default: 10 minutes. User can change via the Account view in the popup.
-const DEFAULT_IDLE_LOCK_SECONDS = 600;
+// Default: never lock (session clears naturally on browser close via chrome.storage.session).
+const DEFAULT_IDLE_LOCK_SECONDS = 0;
 const IDLE_TIMEOUT_KEY = "idle_lock_seconds";
 
 /** Apply the idle detection interval, reading the user's saved preference. */
diff --git a/extension/popup/popup.html b/extension/popup/popup.html
index aca995b..04bd1f8 100644
--- a/extension/popup/popup.html
+++ b/extension/popup/popup.html
@@ -450,9 +450,9 @@
             <select id="acct-idle-timeout" class="acct-select">
               <option value="60">1 minute</option>
               <option value="300">5 minutes</option>
-              <option value="600" selected>10 minutes (default)</option>
+              <option value="600">10 minutes</option>
               <option value="1800">30 minutes</option>
-              <option value="0">Never</option>
+              <option value="0" selected>Never (default)</option>
             </select>
             <p id="acct-idle-saved" class="acct-saved hidden">✓ Saved</p>
           </div>