/**
 * Caches a short-lived access token, refreshing before expiry.
 *
 * Subclasses implement `refreshPair` with their provider's grant. An
 * in-flight refresh is shared so concurrent callers cost one round-trip,
 * and `bufferSeconds` refreshes early so a token never expires
 * mid-request.
 */
export declare abstract class TokenManager {
    private accessToken;
    private expiresAt;
    private inflight;
    private readonly bufferSeconds;
    constructor(bufferSeconds?: number);
    /** Fetch a fresh token as `[accessToken, expiresInSeconds]`. */
    protected abstract refreshPair(): Promise<[string, number]>;
    /**
     * Preload the cache with a token minted outside the refresh flow.
     * `expiresAt` is epoch seconds after which `getToken` refreshes again;
     * pass `Number.POSITIVE_INFINITY` for a token the manager can never
     * replace itself.
     */
    protected seed(token: string, expiresAt: number): void;
    getToken(): Promise<string>;
    private refresh;
}
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