A SQL compiler that pushes parameters into an array ($1, $2, ...) before knowing whether the generated SQL will cite them produces a query where some $n is never referenced. When the driver sends parameters with unknown type (postgres.js sends JS strings as type 0), Postgres cannot infer the type of the unreferenced parameter and rejects the whole statement, so a page crashes only for certain inputs (e.g. a quoted search term on an object without enum fields).