Enum WireError 

pub enum WireError {
    Parse(String),
    Runtime(String),
}

The two failure classes the engine distinguishes, carrying the message the wire contract puts on the wire. Callers construct the correct variant (Parse vs Runtime) so the distinction is honest on the wire even though today’s encoders collapse both to the same bytes — a future bson kind field will surface it. Callers map the class to their surface (exit codes 2/3 for the CLI); the message bytes come from core::run_query.

Variants

Parse(String)

Runtime(String)