Enum FailureMode 

pub enum FailureMode {
    Answers,
    DeliberatelySilent,
}

What a server puts on the wire when the model cannot or will not answer.

This replaces a prose list, and the prose list was wrong in both directions. The root CLAUDE.md names ~20 “deliberately silent” protocols; auditing them found NDP logging its own transmit failure as decision=model_silent (so grep decision=fail_closed_ found nothing for a real outage), and several BLE profiles on the list by family membership rather than by anyone deciding. A paragraph cannot be checked; a declaration can.

The distinction is not a style choice. It follows from one question: is every reply this protocol can send a positive assertion? If so, inventing one on failure is worse than saying nothing — openvpn’s only pre-TLS server message is P_CONTROL_HARD_RESET_SERVER_V2, and sending it is admitting the peer, so “fixing the silence” there would turn a backend outage into an authentication bypass. ARP would write a fabricated MAC into a stranger’s neighbour cache. If instead the protocol has an error vocabulary — an HTTP status, a RESP -LOADING, a Modbus exception — silence just makes the peer wait out its own timeout, and answering is strictly better.

Variants

Answers

The protocol answers, in its own error vocabulary, with a crate::utils::wire_failure category — never the error text.

Keep the two categories distinct where the protocol can express them (503 vs 500, RESP LOADING vs ERR, MySQL 1205 vs 1105): a client that can tell “overloaded” from “broken” backs off instead of recording a permanent fault.

DeliberatelySilent

The protocol writes nothing, because every frame it could send would assert something it does not know to be true.

A protocol declaring this still owes the log the distinction the wire cannot carry: decision=model_reject / model_silent / fail_closed_llm_error, as src/server/radius/ does. Silence on the wire is not silence in the log.

Trait Implementations

impl Clone for FailureMode

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for FailureMode

impl Debug for FailureMode

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for FailureMode

impl PartialEq for FailureMode

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for FailureMode