/**
 * Pure helpers for multi-API-key rotation within a single provider.
 *
 * Single key: many time-increasing retries (router owns the count).
 * Multiple keys: circular order from sticky start; 2 attempts per key.
 */
/** Max stored API keys per LLM provider (UI + save clamp). */
export declare const MAX_PROVIDER_KEYS = 10;
/** Attempts per key when multiple keys are configured (initial + one retry). */
export declare const MULTI_KEY_ATTEMPTS = 2;
/**
 * Circular attempt order of length `n` starting at `startIndex`.
 * Example: n=4, start=2 → [2, 3, 0, 1]
 */
export declare function buildKeyAttemptPlan(n: number, startIndex: number): number[];
/**
 * How many attempts the router should make for one key slot.
 * Single-key mode uses the router's MAX_RETRIES budget (passed in).
 * Multi-key mode is always MULTI_KEY_ATTEMPTS.
 */
export declare function attemptsPerKey(keyCount: number, singleKeyMaxAttempts: number): number;
/** Auth failures: rotate to another key, but do not backoff-retry the same key. */
export declare function isAuthKeyError(error: unknown): boolean;
/**
 * Per-key billing / balance / quota failures (e.g. HTTP 402 insufficient credits).
 * These will not recover on the same key mid-request — rotate immediately.
 */
export declare function isQuotaKeyError(error: unknown): boolean;
/**
 * Failures that should move to the next key without sleeping on the same key
 * (auth revoked, empty wallet). Still try the rest of the circle.
 */
export declare function isImmediateKeySwitchError(error: unknown): boolean;
/** Whether this error should rotate to the next API key (auth / capacity / transient). */
export declare function isKeyRotatableError(error: unknown, isRetriable: (e: unknown) => boolean): boolean;
/**
 * Model/request errors that will not improve with another key for the same
 * model. Outer provider fallback may still apply for some statuses (e.g. 413).
 */
export declare function isKeyCircleStopError(error: unknown): boolean;
export type ProviderKeyEventType = "using" | "retry" | "switch" | "endpoint" | "exhausted";
export interface ProviderKeyEvent {
    readonly type: ProviderKeyEventType;
    readonly provider: string;
    /** Last-4 style mask, e.g. `…ab12`. */
    readonly maskedTail: string;
    readonly reason?: string | undefined;
    readonly waitMs?: number | undefined;
    readonly keyIndex?: number | undefined;
    readonly keyCount?: number | undefined;
}
export declare function formatKeyEventStatus(event: ProviderKeyEvent): string;
export declare function isProviderFailureStatus(text: string): boolean;