/**
 * Provider health and degradation.
 *
 * Bounded rolling evidence per provider/model/endpoint. Uses decay rather than
 * permanent blacklisting. Authentication failures never trigger futile retries;
 * rate limits respect retry hints; fallback is deterministic and preserves task
 * requirements. Health state is durable for resume but bounded in retention.
 */
export type HealthSignal = "success" | "rate_limit" | "timeout" | "authentication_failure" | "schema_incompatibility" | "tool_call_corruption" | "empty_response" | "context_overflow" | "provider_outage" | "cancellation";
export type HealthLevel = "healthy" | "degraded" | "unhealthy" | "unknown";
export interface HealthSample {
    signal: HealthSignal;
    recordedAt: string;
    sequence: number;
}
export interface ProviderHealthState {
    provider: string;
    model?: string;
    endpoint?: string;
    /** Bounded window of recent samples (oldest first). */
    samples: readonly HealthSample[];
    /** Deterministic snapshot used for routing. */
    level: HealthLevel;
    lastSuccessfulAt?: string;
}
export declare const MAX_HEALTH_SAMPLES = 32;
export declare function createHealthState(provider: string, model?: string, endpoint?: string): ProviderHealthState;
/**
 * Record a health signal, keeping a bounded window of samples, and derive the
 * level from the window. Authentication failures mark the provider degraded
 * (never retried blindly). Successful newest sample restores health.
 */
export declare function recordHealthSignal(state: ProviderHealthState, signal: HealthSignal, recordedAt: string, sequence: number): ProviderHealthState;
/** A retry is allowed only for retryable signals, and only with a cooldown. */
export declare function shouldRetry(state: ProviderHealthState, cooldownMs: number, nowMs: number): boolean;
/** Count of a given signal within the window (used for bounded evidence). */
export declare function countSignal(state: ProviderHealthState, signal: HealthSignal): number;
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