diff --git a/.gitignore b/.gitignore
index 18787626d..c3f7b497c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -91,3 +91,9 @@ public/sitemap.xml
 /blob-report/
 /playwright/.cache/
 /playwright/.auth/
+
+# TypeScript build info
+tsconfig.tsbuildinfo
+
+# MCP config (local tool settings)
+.mcp.json
diff --git a/components/Forms/UpdateProfileForm/UpdateProfileForm.tsx b/components/Forms/UpdateProfileForm/UpdateProfileForm.tsx
index 1cfe7c26f..607b17dda 100644
--- a/components/Forms/UpdateProfileForm/UpdateProfileForm.tsx
+++ b/components/Forms/UpdateProfileForm/UpdateProfileForm.tsx
@@ -80,7 +80,17 @@ function UpdateProfileForm({
       }
     }
 
-    await updateUser(values);
+    try {
+      await updateUser(values);
+    } catch (error) {
+      const axiosError = error as AxiosError;
+      if (axiosError.response?.status === 404) {
+        // Record no longer exists — cookie was cleared by the API, redirect to re-register
+        push('/join');
+        return;
+      }
+      throw error;
+    }
   };
 
   const goToProfile = async () => {
diff --git a/pages/api/registration/update.ts b/pages/api/registration/update.ts
index b0d77c718..c96968642 100644
--- a/pages/api/registration/update.ts
+++ b/pages/api/registration/update.ts
@@ -12,6 +12,13 @@ export default async function handler(req: NextApiRequest, res: NextApiResponse)
 
   const email = req.cookies?.opCodeApplicantEmail;
 
+  // The cookie is cleared on the final successful step (when all fields are filled).
+  // Additional PATCH requests can still arrive after that (e.g. user double-clicking),
+  // so we need to bail out early rather than querying Airtable with an undefined email.
+  if (!email) {
+    return res.status(401).json({ message: 'Missing registration cookie' });
+  }
+
   try {
     // Search for a record with the relevant email
     const records = await base(AIR_TABLE_TABLE_NAME)
@@ -96,10 +103,11 @@ export default async function handler(req: NextApiRequest, res: NextApiResponse)
       return res.status(200).json({ message: 'Success' });
     }
 
-    // No record found, add a new row to the table
-    return res
-      .writeHead(404, { Location: '/' })
-      .json({ message: `No record found for this email (${email})` });
+    // No record found — clear the stale cookie so the page guard redirects to /
+    res.setHeader('Set-Cookie', [
+      `opCodeApplicantEmail=; path=/; expires=Thu, 01 Jan 1970 00:00:00 GMT`,
+    ]);
+    return res.status(404).json({ message: `No record found for this email (${email})` });
   } catch (error) {
     console.error('Error with /api/registration/update PATCH request:', error);
     return res.status(500).json({ message: 'Server Error' });