/**
 * @module koi/model-fallback-sticky
 *
 * Session-sticky model fallback memory. Once a primary model fails and a
 * fallback answers, the switch must not replay on every message — each turn
 * would re-pay the primary's failure latency and re-announce the switch. This
 * map remembers, per requested primary ("provider/model" key), which candidate
 * answered last; `runWithModelFallback` starts THERE on subsequent runs.
 *
 * Scope is the gateway process: cleared by a manual model switch (the person
 * re-choosing a model re-arms the primary) and naturally reset on restart.
 * Dependency-free on purpose — imported from both the koi runner side and the
 * session model-override side without creating a cycle.
 */
export declare function getStickyModelFallback(primaryKey: string): string | undefined;
export declare function setStickyModelFallback(primaryKey: string, candidateKey: string): void;
export declare function deleteStickyModelFallback(primaryKey: string): void;
/** A manual model switch (or restart) re-arms the primary everywhere. */
export declare function clearStickyModelFallbacks(): void;