import type { UsageSnapshot } from './usage.js';
export interface AccountUsage {
    name: string;
    /** null when the account has no usage cache yet (never used); treated as full headroom. */
    usage: UsageSnapshot | null;
}
export interface RotateDecision {
    shouldRotate: boolean;
    reason: string;
    target?: string;
}
export interface RotateInput {
    active: string;
    accounts: AccountUsage[];
    /** Percent at which an account is considered capped (e.g. 95 for proactive rotation). */
    threshold: number;
    /** Judged against this instant, so a window that has reset is not a cap. */
    now?: number;
}
/**
 * Decide whether to rotate off the active account and to which account. Rotates
 * only when the active account is capped and a non-capped account exists; picks
 * the candidate with the most headroom.
 */
export declare function decideRotation(input: RotateInput): RotateDecision;