diff --git a/app/api/projects/[projectId]/design-surfaces/route.ts b/app/api/projects/[projectId]/design-surfaces/route.ts
index c507813..709ce11 100644
--- a/app/api/projects/[projectId]/design-surfaces/route.ts
+++ b/app/api/projects/[projectId]/design-surfaces/route.ts
@@ -83,9 +83,11 @@ export async function PATCH(
       return NextResponse.json({ error: 'Invalid body' }, { status: 400 });
     }
 
+    // Put projectId as $1 (matches known-working pattern in other routes)
+    // and cast id::text to avoid "could not determine data type of parameter" (42P18)
     await query(
-      `UPDATE fs_projects SET data = $1::jsonb WHERE id = $2`,
-      [JSON.stringify(updated), projectId]
+      `UPDATE fs_projects SET data = $2::jsonb WHERE id::text = $1`,
+      [projectId, JSON.stringify(updated)]
     );
 
     return NextResponse.json({ success: true });