Enum FallbackReason 

pub enum FallbackReason {
    EmbeddingFailed(String),
    SlotExhausted,
    OAuthQuota {
        backend: &'static str,
    },
    BackendMismatch {
        requested: &'static str,
        resolved: &'static str,
    },
    DimZero,
    Cancelled,
    Timeout {
        operation: String,
        duration_secs: u64,
    },
}

G58/S1: reason an embedding call could not be completed and the caller must fall back to a non-vector retrieval path (FTS5 prefix + LIKE).

Returned by try_embed_query_with_fallback so the recall and hybrid-search handlers can surface a structured vec_degraded / warning envelope instead of a hard AppError::Embedding exit 11.

Variants

EmbeddingFailed(String)

The LLM subprocess failed (rate limit, OAuth contention, quota exhausted, model unparsable response, divergent dim, etc.). Carries the original error message for observability.

SlotExhausted

The LLM slot semaphore was exhausted: 8+ concurrent LLM subprocesses blocked the acquire beyond the backoff window (50ms + 100ms + 200ms + 400ms = 750ms total). Resolved at v1.0.85 (GAP-003 / ADR-0043).

OAuthQuota

OAuth usage quota exhausted on the named backend. The caller should retry with an alternative backend (codex ↔ claude) before falling back to FTS5-puro.

Fields

backend: &'static str

BackendMismatch

The user requested a backend that differs from the one that actually executed the embedding (legacy “synonym for codex” bug from v1.0.83). Resolved at v1.0.84 (GAP-002).

Fields

requested: &'static str

resolved: &'static str

DimZero

The embedding returned a zero-dimensional vector, signalling a structural bug (the LLM did not produce any floats). Distinct from OAuthQuota (quota exhausted) and EmbeddingFailed (subprocess error).

Cancelled

The embedding was cancelled by an external signal (SIGTERM, etc.).

Timeout

The embedding exceeded its time budget. Carries the operation name and the elapsed seconds for diagnostic logging.

Fields

operation: String

duration_secs: u64

Implementations

impl FallbackReason

pub fn reason_code(&self) -> &'static str

Stable, machine-friendly reason code used by JSON envelopes (vec_degraded_reason). Mirrors the v1.0.84 contract extended at v1.0.85 with 4 new variants (GAP-003 / ADR-0043).

Trait Implementations

impl Clone for FallbackReason

fn clone(&self) -> FallbackReason

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FallbackReason

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

Formats the value using the given formatter.

impl Display for FallbackReason

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

Formats the value using the given formatter.

impl Error for FallbackReason

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl PartialEq for FallbackReason

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for FallbackReason