diff --git a/apps/editor/lib/supabase/server.ts b/apps/editor/lib/supabase/server.ts
index 2e2b072c..4803d0bc 100644
--- a/apps/editor/lib/supabase/server.ts
+++ b/apps/editor/lib/supabase/server.ts
@@ -2,6 +2,26 @@ import { createClient } from '@supabase/supabase-js'
 import type { SupabaseDatabase } from '@pascal-app/db'
 import { env } from '@/env.mjs'
 
+/**
+ * Safety check: warn loudly if a Vercel preview deployment is using
+ * the production Supabase instance. This catches misconfigured branching.
+ */
+if (
+  process.env.VERCEL_ENV === 'preview' &&
+  process.env.SUPABASE_URL &&
+  env.NEXT_PUBLIC_SUPABASE_URL === process.env.SUPABASE_URL
+) {
+  // If the Supabase integration set a branch-specific SUPABASE_URL,
+  // it should differ from NEXT_PUBLIC_SUPABASE_URL (which comes from the
+  // generic env vars pointing at production). When they match, the
+  // integration likely skipped branch creation for this PR.
+  console.warn(
+    '⚠️  [supabase] Preview deployment appears to be using the PRODUCTION ' +
+    'Supabase instance. Supabase branching may not be configured for this PR. ' +
+    'See: https://supabase.com/docs/guides/deployment/branching',
+  )
+}
+
 /**
  * Supabase client for server-side use with service role key
  * Bypasses Row Level Security (RLS) - use with caution