diff --git a/entrypoints/content.ts b/entrypoints/content.ts
index ee7bac1..09975a5 100644
--- a/entrypoints/content.ts
+++ b/entrypoints/content.ts
@@ -200,12 +200,42 @@ export default defineContentScript({
       }
     }
 
+    // ─── Extension context guard ──────────────────────────────────────────────
+
+    function isExtensionValid(): boolean {
+      try {
+        return !!chrome.runtime?.id;
+      } catch {
+        return false;
+      }
+    }
+
+    function showErrorToast(msg: string) {
+      const toast = document.createElement('div');
+      toast.style.cssText = `
+        position: fixed; bottom: 20px; right: 20px; z-index: 999999;
+        background: #f38ba8; color: #1e1e2e; padding: 10px 16px;
+        border-radius: 8px; font-family: system-ui, sans-serif;
+        font-size: 13px; box-shadow: 0 4px 12px rgba(0,0,0,0.3);
+      `;
+      toast.textContent = msg;
+      document.body.appendChild(toast);
+      setTimeout(() => toast.remove(), 4000);
+    }
+
     // ─── LLM call ─────────────────────────────────────────────────────────────
 
     async function runAction(action: string) {
       if (!selectedText) return;
       const textToProcess = selectedText;
 
+      // Guard: extension may have been reloaded/updated
+      if (!isExtensionValid()) {
+        hideToolbar();
+        showErrorToast('LexAI was updated. Please refresh the page.');
+        return;
+      }
+
       // Show loading in toolbar
       if (toolbar) {
         toolbar.innerHTML = '';
@@ -235,7 +265,11 @@ export default defineContentScript({
         }
       } catch (err) {
         hideToolbar();
-        showModal(`❌ Error: ${String(err)}`, null);
+        if (String(err).includes('Extension context invalidated')) {
+          showErrorToast('LexAI was updated. Please refresh the page.');
+        } else {
+          showModal(`❌ Error: ${String(err)}`, null);
+        }
       }
     }