diff --git a/src/components/inbox/conversation-list.tsx b/src/components/inbox/conversation-list.tsx
index 76c6ee6..c13e137 100644
--- a/src/components/inbox/conversation-list.tsx
+++ b/src/components/inbox/conversation-list.tsx
@@ -54,7 +54,13 @@ export function ConversationList({
       .order("last_message_at", { ascending: false });
 
     if (error) {
-      console.error("Failed to fetch conversations:", error);
+      // Supabase errors have non-enumerable properties — log fields explicitly
+      console.error("Failed to fetch conversations:", {
+        message: error.message,
+        details: error.details,
+        hint: error.hint,
+        code: error.code,
+      });
       setLoading(false);
       return;
     }
diff --git a/src/lib/supabase/client.ts b/src/lib/supabase/client.ts
index 792b457..f381eb7 100644
--- a/src/lib/supabase/client.ts
+++ b/src/lib/supabase/client.ts
@@ -1,8 +1,18 @@
 import { createBrowserClient } from '@supabase/ssr'
+import type { SupabaseClient } from '@supabase/supabase-js'
+
+// Singleton instance — one client shared across the whole browser session.
+// Creating multiple clients causes auth-lock contention ("Lock was released
+// because another request stole it") and intermittent fetch failures.
+let browserClient: SupabaseClient | undefined
 
 export function createClient() {
-  return createBrowserClient(
+  if (browserClient) return browserClient
+
+  browserClient = createBrowserClient(
     process.env.NEXT_PUBLIC_SUPABASE_URL!,
     process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!
   )
+
+  return browserClient
 }