diff --git a/frontend/src/lib/auth.ts b/frontend/src/lib/auth.ts
index 368cdeb..219da7c 100644
--- a/frontend/src/lib/auth.ts
+++ b/frontend/src/lib/auth.ts
@@ -26,7 +26,10 @@ function metadataString(user: SupabaseUser, ...keys: string[]): string | undefin
 }
 
 export function toAppUser(user: SupabaseUser): User {
-  const handle = metadataString(user, 'user_name', 'preferred_username') ?? user.email?.split('@')[0] ?? user.id
+  // The auth trigger stores profile handles lowercase (profiles_handle_format), while GitHub's
+  // user_name keeps its original casing. Handles are compared exactly everywhere (profile routes,
+  // owner filters), so the session handle must be derived the same way the trigger does.
+  const handle = (metadataString(user, 'user_name', 'preferred_username') ?? user.email?.split('@')[0] ?? user.id).toLowerCase()
 
   return {
     id: user.id,
diff --git a/frontend/src/pages/Profile.tsx b/frontend/src/pages/Profile.tsx
index 8642555..9f9f1df 100644
--- a/frontend/src/pages/Profile.tsx
+++ b/frontend/src/pages/Profile.tsx
@@ -1,4 +1,4 @@
-import { Link, useParams, useSearchParams } from 'react-router-dom'
+import { Link, Navigate, useParams, useSearchParams } from 'react-router-dom'
 import { ExternalLink, GitFork } from 'lucide-react'
 import { Skeleton } from '@/components/ui/skeleton'
 import { UserAvatar } from '@/components/UserAvatar'
@@ -33,11 +33,17 @@ export default function Profile() {
   const [sp, setSp] = useSearchParams()
   const tab = (sp.get('tab') as Tab) || 'rigs'
   const cat = useCatalog()
+  // Handles are stored lowercase, but profile URLs are often typed or shared with
+  // GitHub's casing (e.g. /u/SergiioB). Resolve against the lowercase handle and
+  // canonicalize the address bar without dropping the tab query.
+  const canonical = handle.toLowerCase()
   const data = useAsync(
-    () => Promise.all([api.user(handle), api.userRigs(handle), api.userResults(handle), api.customRuntimes({ owner: handle })]),
-    [handle],
+    () => Promise.all([api.user(canonical), api.userRigs(canonical), api.userResults(canonical), api.customRuntimes({ owner: canonical })]),
+    [canonical],
   )
-  usePageTitle(handle ? `@${handle}` : 'Profile')
+  usePageTitle(canonical ? `@${canonical}` : 'Profile')
+  if (canonical !== handle)
+    return <Navigate to={{ pathname: `/u/${canonical}`, search: sp.toString() }} replace />
   if (data.error)
     return (
       <Block>